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In the past four decades, NASA and other space agencies from around the world have accomplished some amazing feats. Together, they have sent manned missions to the Moon, explored Mars, mapped Venus and Mercury, conducted surveys and captured breathtaking images of the Outer Solar System. However, looking ahead to the next generation of exploration and the more-distant frontiers that remain to be explored, it is clear that new ideas need to be put forward of how to quickly and efficiently reach those destinations.
Basically, this means finding ways to power rockets that are more fuel and cost-effective while still providing the necessary power to get crews, rovers and orbiters to their far-flung destinations. In this respect, NASA has been taking a good look at nuclear fission as a possible means of propulsion.
In fact, according to presentation made by Doctor Michael G. Houts of the NASA Marshall Space Flight Center back in October of 2014, nuclear power and propulsion have the potential to be “game changing technologies for space exploration.”
As the Marshall Space Flight Center’s manager of nuclear thermal research, Dr. Houts is well versed in the benefits it has to offer space exploration. According to the presentation he and fellow staffers made, a fission reactor can be used in a rocket design to create Nuclear Thermal Propulsion (NTP). In an NTP rocket, uranium or deuterium reactions are used to heat liquid hydrogen inside a reactor, turning it into ionized hydrogen gas (plasma), which is then channeled through a rocket nozzle to generate thrust.
A second possible method, known as Nuclear Electric Propulsion (NEC), involves the same basic reactor converted its heat and energy into electrical energy which then powers an electrical engine. In both cases, the rocket relies on nuclear fission to generates propulsion rather than chemical propellants, which has been the mainstay of NASA and all other space agencies to date.
Compared to this traditional form of propulsion, both NTP and NEC offers a number of advantages. The first and most obvious is the virtually unlimited energy density it offers compared to rocket fuel. At a steady state, a fission reactor produces an average of 2.5 neutrons per reaction. However, it would only take a single neutron to cause a subsequent fission and produce a chain reaction and provide constant power.
In fact, according to the report, an NTP rocket could generate 200 kWt of power using a single kilogram of uranium for a period of 13 years – which works out of to a fuel efficiency rating of about 45 grams per 1000 MW-hr.
In addition, a nuclear-powered engine could also provide superior thrust relative to the amount of propellant used. This is what is known as specific impulse, which is measured either in terms of kilo-newtons per second per kilogram (kN·s/kg) or in the amount of seconds the rocket can continually fire. This would cut the total amount of propellent needed, thus cutting launch weight and the cost of individual missions. And a more powerful nuclear engine would mean reduced trip times, another cost-cutting measure.
Although no nuclear-thermal engines have ever flown, several design concepts have been built and tested over the past few decades, and numerous concepts have been proposed. These have ranged from the traditional solid-core design to more advanced and efficient concepts that rely on either a liquid or a gas core.
In the case of a solid-core design, the only type that has ever been built, a reactor made from materials with a very high melting point houses a collection of solid uranium rods which undergo controlled fission. The hydrogen fuel is contained in a separate tank and then passes through tubes around the reactor, gaining heat and converted into plasma before being channeled through the nozzles to achieve thrust.
Using hydrogen propellant, a solid-core design typically delivers specific impulses on the order of 850 to 1000 seconds, which is about twice that of liquid hydrogen-oxygen designs – i.e. the Space Shuttle’s main engine.
However, a significant drawback arises from the fact that nuclear reactions in a solid-core model can create much higher temperatures than the conventional materials can withstand. The cracking of fuel coatings can also result from large temperature variations along the length of the rods, which taken together, sacrifices much of the engine’s potential for performance.
Many of these problems were addressed with the liquid core design, where nuclear fuel is mixed into the liquid hydrogen and allowing the fission reaction to take place in the liquid mixture itself. This design can operate at temperatures above the melting point of the nuclear fuel thanks to the fact that the container wall is actively cooled by the liquid hydrogen. It is also expected to deliver a specific impulse performance of 1300 to 1500 (1.3 to 1.5 kN·s/kg) seconds.
However, compared to the solid-core design, engines of this type are much more complicated, and therefore more expensive and difficult to build. Part of the problem has to do with the time it takes to achieve a fission reaction, which is significantly longer than the time it takes to heat the hydrogen fuel. Therefore, engines of this kind require methods to both trap the fuel inside the engine while simultaneously allowing heated plasma the ability to exit through the nozzle.
The final classification is the gas-core engine, a modification of the liquid-core design that uses rapid circulation to create a ring-shaped pocket of gaseous uranium fuel in the middle of the reactor that is surrounded by liquid hydrogen. In this case, the hydrogen fuel does not touch the reactor wall, so temperatures can be kept below the melting point of the materials used.
An engine of this kind could allow for specific impulses of 3000 to 5000 seconds (30 to 50 kN·s/kg). But in an “open-cycle” design of this kind, the losses of nuclear fuel would be difficult to control. An attempt to remedy this was drafted with the “closed cycle design” – aka. the “nuclear lightbulb” engine – where the gaseous nuclear fuel is contained in a series of super-high-temperature quarts containers.
Although this design is less efficient than the open-cycle design, and has a more in common with the solid-core concept, the limiting factor here is the critical temperature of quartz and not that of the fuel stack. What’s more, the closed-cycle design is expected to still deliver a respectable specific impulse of about 1500–2000 seconds (15–20 kN·s/kg).
However, as Houts indicated, one of the greatest assets nuclear fission has going for it is the long history of service it has enjoyed here on Earth. In addition to commercial reactors providing electricity all over the world, naval vessels (such as aircraft carriers and submarines) have made good use of slow-fission reactors for decades.
Also, NASA has been relying on nuclear reactors to power unmanned craft and rover for over four decades, mainly in the form of Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units (RHU). In the case of the former, heat is generated by the slow decay of plutonium-238 (Pu-238), which is then converted into electricity. In the case of the latter, the heat itself is used to keep components and ship’s systems warm and running.
These types of generators have been used to power and maintain everything from the Apollo rockets to the Curiosity Rover, as well as countless satellites, orbiters and robots in between. Since its inception,a total of 44 missions have been launched by NASA that have used either RTGs or RHUs, while the former-Soviet space program launched a comparatively solid 33.
Nuclear engines were also considered for a time as a replacement for the J-2, a liquid-fuel cryogenic rocket engine used on the S-II and S-IVB stages on the Saturn V and Saturn I rockets. But despite their being numerous versions of a solid-core reactors produced and tested in the past, none were ever put into service for an actual space flight.
Between 1959 and 1972, the United States tested twenty different sizes and designs during Project Rover and NASA’s Nuclear Engine for Rocket Vehicle Application (NERVA) program. The most powerful engine ever tested was the Phoebus 2a, which during a high-power test operated for a total of 32 minutes – 12 minutes of which were at power levels of more than 4.0 million kilowatts.
But looking to the future, Houts’ and the Marshall Space Flight Center see great potential and many possible applications. Examples cited in the report include long-range satellites that could explore the Outer Solar System and Kuiper Belt, fast, efficient transportation for manned missions throughout the Solar System, and even the provisions of power for settlements on the Moon and Mars someday.
One possibility is to equip NASA’s latest flagship – the Space Launch System (SLS) – with chemically-powered lower-stage engines and a nuclear-thermal engine on its upper stage. The nuclear engine would remain “cold” until the rocket had achieved orbit, at which point the upper stage would be deployed and reactor would be activated to generate thrust.
This concept for a “bimodal” rocket – one which relies on chemical propellants to achieve orbit and a nuclear-thermal engine for propulsion in space – could become the mainstay of NASA and other space agencies in the coming years. According to Houts and others at Marshall, the dramatic increase in efficiency offered by such rockets could also facilitate NASA’s plans to explore Mars by allowing for the reliable delivery of high-mass automated payloads in advance of manned missions.
These same rockets could then be retooled for speed (instead of mass) and used to transport the astronauts themselves to Mars in roughly half the time it would take for a conventional rocket to make the trip. This would not only save on time and cut mission costs, it would also ensure that the astronauts were exposed to less harmful solar radiation during the course of their flight.
To see this vision become reality, Dr. Houts and other researchers from the Marshall Space Center’s Propulsion Research and Development Laboratory are currently conducting NTP-related tests at the Nuclear Thermal Rocket Element Environmental Simulator (or “NTREES”) in Huntsville, Alabama.
Here, they have spent the past few years analyzing the properties of various nuclear fuels in a simulated thermal environment, hoping to learn more about how they might effect engine performance and longevity when it comes to a nuclear-thermal rocket engine.
These tests are slated to run until June of 2015, and are expected to lay the groundwork for large-scale ground tests and eventual full-scale testing in flight. The ultimate goal of all of this is to ensure that a manned mission to Mars takes place by the 2030s, and to provide NASA flight engineers and mission planners with all the information they need to see it through.
But of course, it is also likely to have its share of applications when it comes to future Lunar missions, sending crews to study Near-Earth Objects (NEOs), and sending craft to the Jovian moons and other locations in the outer Solar System. As the report shows, NTP craft can be easily modified using modular components to perform everything from Lunar cargo landings to crewed missions, to surveying Near-Earth Asteroids (NEAs).
The universe is a big place, and space exploration is still very much in its infancy. But if we intend to keep exploring it and reaping the rewards that such endeavors have to offer, our methods will have to mature. NTP is merely one proposed possibility. But unlike Nuclear Pulse Propulsion, the Daedalus concept, anti-matter engines, or the Alcubierre Warp Drive, a rocket that runs on nuclear fission is feasible, practical, and possible within the near-future.
Nuclear thermal research at the Marshall Center is part of NASA’s Advanced Exploration Systems (AES) Division, managed by the Human Exploration and Operations Mission Directorate and including participation by the U.S. Department of Energy. | 0.838804 | 3.437782 |
Crescent ♈ Aries
Moon phase on 1 May 2084 Monday is Waning Crescent, 26 days old Moon is in Aries.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 4 days on 27 April 2084 at 10:29.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing first ∠3° of ♈ Aries tropical zodiac sector.
Lunar disc appears visually 1.6% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1873" and ∠1904".
Next Full Moon is the Flower Moon of May 2084 after 18 days on 20 May 2084 at 02:36.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 26 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 1042 of Meeus index or 1995 from Brown series.
Length of current 1042 lunation is 29 days, 13 hours and 40 minutes. It is 1 hour and 1 minute shorter than next lunation 1043 length.
Length of current synodic month is 56 minutes longer than the mean length of synodic month, but it is still 6 hours and 7 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠92.7°. At beginning of next synodic month true anomaly will be ∠128.4°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
8 days after point of perigee on 23 April 2084 at 11:07 in ♐ Sagittarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 7 days, until it get to the point of next apogee on 9 May 2084 at 08:15 in ♋ Cancer.
Moon is 382 660 km (237 774 mi) away from Earth on this date. Moon moves farther next 7 days until apogee, when Earth-Moon distance will reach 405 281 km (251 830 mi).
5 days after its ascending node on 26 April 2084 at 09:18 in ♑ Capricorn, the Moon is following the northern part of its orbit for the next 8 days, until it will cross the ecliptic from North to South in descending node on 10 May 2084 at 08:57 in ♋ Cancer.
5 days after beginning of current draconic month in ♑ Capricorn, the Moon is moving from the beginning to the first part of it.
7 days after previous South standstill on 24 April 2084 at 03:07 in ♐ Sagittarius, when Moon has reached southern declination of ∠-25.760°. Next 6 days the lunar orbit moves northward to face North declination of ∠25.673° in the next northern standstill on 7 May 2084 at 17:28 in ♊ Gemini.
After 3 days on 4 May 2084 at 19:32 in ♉ Taurus, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.168383 |
The glaciers are going
As can be seen above, the Waggonwaybreen glacier in Svalbard, Norway, has retreated substantially since 1900. Svalbard's glaciers are not only retreating, they are also losing about two feet of their thickness each year. Glaciers around the world have retreated at unprecedented rates and some have disappeared altogether. The melting of glaciers will affect people around the world, their drinking water supplies, water needed to grow food and supply energy, as well as global sea levels.
The Intergovernmental Panel on Climate Change estimates that around the world glaciers (excluding the Greenland and Antarctic ice sheets) will decrease in volume between 15 to 55 percent by 2100 even if we are able to limit global warming to under 2˚C; they could shrink up to 85 percent if warming increases much more.
In Earth's history, there have been at least five major ice ages, when long-term cooling of the planet resulted in the expansion of ice sheets and glaciers. Past ice ages have been naturally set off by a numerous factors, most importantly, changes in the Earth's orbit around the sun (Milankovitch cycles) and shifting tectonic plate movements that affect wind and ocean currents. The mixture of gases in the atmosphere (such as carbon dioxide and methane) as well as solar and volcanic activity are also contributing factors. Today we are in a warm interval—an interglacial—of the Earth's fifth ice age.
A glacier is a large accumulation of ice, snow, rock, sediment and water on land that is moving down slope under its own weight and gravity. Today 10 percent of Earth's land is covered by glaciers (including Antarctica and Greenland). They contain 75 percent of the planet's freshwater, storing it as ice during the cold season and releasing some of it as meltwater during summer months. Runoff from glaciers cools the streams below, providing habitat for plants and animals during dry periods.
More than one-sixth of the world's population, particularly in China, India and other Asian countries, live in the basins of glacier-fed rivers and depend on them for drinking and irrigation water.
A glacier's mass balance determines if it will advance or retreat. If the amount of snow and ice accumulated during winter is less than the melting that takes place in summer, the glacier is considered to have a negative mass balance and retreats. Today, nearly all glaciers have a negative mass balance due to global warming and changes in precipitation.
In New Zealand's Southern Alps, Joerg Schaefer, a research professor at Lamont-Doherty Earth Observatory, and his colleagues chemically analyzed elements in rocks that were left uncovered when glaciers retreated 20,000 years ago at the end of the last ice age. They figured out how long the rocks had been exposed, then reconstructed local glacial records and compared them to other records such as Antarctic ice cores, which reveal changing atmospheric carbon dioxide levels.
"Glaciers seem to follow closely what happens with the atmospheric carbon dioxide concentration," said Schaefer. "Throughout our glacier chronologies, whenever the CO2 started to rise, the glaciers in New Zealand started to retreat. So we think that proves that there's a very close link between greenhouse gases, carbon dioxide, and glaciers. Which is actually very bad news, because we're pumping so much CO2 in the air."
Earth is actually due for a natural new ice age, explained Schaefer. Typically the interglacial between ice ages lasts 10,000 to 12,000 years, and we are already 12,000 years into this one. A natural cooling cycle should be starting, but even if it does, said Schaefer, we will not see evidence of it because humans have so altered conditions on the planet by burning fossil fuels.
Schaefer has been working on a global survey of mountain glaciers, comparing glacier retreat over the last 150 years to how glaciers behaved in the past, particularly at the end of the last ice age. "That [the transition out of the last ice age] was one of the most dramatic geological and natural changes that the Earth has seen," he said.
"The rate of change that we see in the moment, recorded most directly and visibly by mountain glaciers, is way, way, way faster than it was at the end of the ice age," said Schaefer. "What we have seen over the last 150 years, all over the planet, is that these mountain glaciers record a retreat corresponding to 1˚ to 1.5˚C warming over 150 years, with the biggest part of that retreat happening over the last decade. The speed with which these glaciers are retreating has exponentially speeded up…and if you compare the rate of change, nothing ever happened like that in the geological past."
Humans are exacerbating glacial melt because burning fossil fuels not only releases CO2, it also emits black carbon, a tiny component of air pollution that can absorb one million times more solar energy than CO2. When black carbon falls to earth with precipitation, it darkens the snow and ice, reduces their albedo (the reflecting power of a surface), warms the snow, and speeds up melting.
Marco Tedesco, a research professor at Lamont-Doherty, is researching the processes driving glacial melt in Greenland, including albedo reduction, bare ice exposure after snow layers melt away and atmospheric circulation patterns. He is studying "feedback" mechanisms such as how melting reduces albedo and increases moisture in the air, which also warms the air. "We understand these processes," said Tedesco. "But we don't yet know how they interact and how much they amplify each other over time to accelerate the pace of melting. Today there are more data available, more observations from space and the ground, and better and faster models. These can help us improve our estimates and better project Greenland's contribution to sea level rise."
"But we know things are going in one direction and will be getting much faster in this direction. There will be more warming and more melt. All the things that could slow the melting down, like the cooling of the Arctic or more accumulation of snow in summer, are not going to happen. And even if they did, they would be short, just a bump in the road."
Here are a few examples of the glaciers we are losing.
- Montana's Glacier National Park had 150 glaciers in 1850; today there are 25.
- The greater Himalayas, which contain nearly one-third of Earth's non-polar ice, have warmed much more than the global average over the last 100 years; between 1950 and 2000, 82 percent of glaciers in western China shrank.
- The Aletsch Glacier, the largest in Switzerland, retreated 1.7 miles between 1880 and 2009.
- By 2000, the Furtwangler Glacier on top of Mount Kilimanjaro in Tanzania was half the size it was in 1976.
If the melting continues over the next few decades, some of the world's most populous areas could run out of water during the dry season. For awhile, the increase in flow from melting ice and snow during the dry season will seem like a boon, but in the future, the downstream flow's variability will increase and eventually flow could disappear altogether, impacting food production, biodiversity and economic growth.
Communities around the world rely on glacial water that has been dammed for the production of hydropower. Retreating glaciers will increase the variability of flow or decrease it, which will affect power generation.
France gets about 75 percent of its electricity from nuclear power plants, half of which are on the Rhone River, fed by the rapidly retreating Rhone Glacier. Over the last 15 years, the Rhone River twice became so hot and water levels were so low in summer that nuclear power plants had to be shut down.
As a result of glacial melting, glacial lake outburst floods are increasing. As glaciers shrink, meltwater can form a lake that is dammed by glacial debris (ice or soil and rock) at the tongue of the glacier.
But those dams can be unstable and collapse under the pressure of more melting. Peru has experienced some of the most destructive glacial lake outburst floods; between 1941 and 1950, three such floods killed 6,000 people.
Glacial retreat can destablilize slopes, which can lead to landslides, and warming temperatures can trigger avalanches. In 2002, a huge portion of the Kolka Glacier on the Russia-Georgia border broke off and, hastened by the meltwater underneath, created an avalanche that hurtled down the mountain at 150 miles per hour, killing over 100 people in the town below. The onrush lasted 7 minutes. In July 2016, two avalanches occurred in Tibet, one of which killed nine people.
If all the world's glacial ice were to melt, sea levels would rise 265 feet as the meltwater flowed into rivers and ended up in the ocean. Most sea level rise would come from Antarctica and Greenland in the Arctic, not mountain glaciers, which would contribute only about 20 inches.
Recent research about melting glaciers in the Arctic (which has been warming twice as fast as the rest of the world for the last half-century) and Antarctica suggest that the low-end projections for sea level rise made by the Intergovernmental Panel on Climate Change are too low.
In its most recent report, the Panel projected that if we are able to reduce emissions significantly, sea levels could rise 11 to 24 inches by 2100; if emissions remain high, we could see a rise of 20 to 38 inches. Sea level rise will cause coastal flooding, erosion, damage to infrastructure and buildings, ecosystem changes and compromised drinking water sources.
The freshwater from glacial melt flowing into the oceans has an impact not only on sea levels, but also on ocean acidification, biological productivity and weather patterns. The amount of freshwater in the upper layers of the Arctic Ocean, which has increased 11 percent since its 1980-2000 average, could also affect circulation in the Nordic Sea and the Atlantic Ocean.
The influx of freshwater could potentially disrupt or slow down the "Global Ocean Conveyer," the regular cycling of cold water south and warm water north through the Atlantic Ocean that plays a huge part in the climate of North America and Western Europe, as well as in ocean nutrient and carbon dioxide cycles.
Pollutants like pesticides, heavy metals, persistent organic pollutants and PCBs, polychlorinated biphenyls, have made their way to the Arctic and Antarctica on ocean and wind currents. When the glaciers melt, pollutants once trapped in ice are released and can enter rivers, oceans and food webs where they bioaccumulate in marine creatures; those at the top of the food chain, like polar bears and humans, will be affected the most.
Researchers have also found living bacteria and microbes in 420,000-year-old ice cores and revived them. As glaciers melt, masses of microbes, some 750,000 years old, are released from the ice. When they reach the ocean, they could affect ocean chemistry and marine ecosystems, with unpredictable effects. Scientific American reported, "…the biomass of microbial cells in and beneath the ice sheet may amount to more than 1,000 times that of all the humans on Earth."
Ongoing research is key to understanding the melting glaciers and their potential impacts on safety, water supplies, energy production and economies. "The important question for the future is going to be, when are problems going to arise as a result of the changes in glaciers," said Tedesco. "What are the things we can tackle, understanding the time line…I'd want to know before the Netherlands is under water so that policy adjustments can be made to protect people. And projections for the impacts on cities are going to be different from the impacts on food production or on GDP."
"We need help from political and social scientists…we have to transfer the information to policy makers to prepare for this," said Schaefer. "We need the five- to 10-year perspective—that is our mission here at Lamont-Doherty, to preach that to everybody."
This story is republished courtesy of Earth Institute, Columbia University: http://blogs.ei.columbia.edu . | 0.831263 | 3.321738 |
In almost precisely a decade’s time, a giant asteroid will fly past Earth, closer than any recent asteroids of comparable size. Scientists have named this piece of rock Apophis after the Egyptian god of chaos.
Fortunately that won’t hit the Earth, though there was a time when there was thought to be a small but worrying chance that it might. That close passage will occur on 13 April 2029 – Black Friday – and people watching the sky in expectation of its arrival will see a spot of light which quickly becomes much brighter, eventually as bright as the stars.
It’s also fast. It’s estimated it will cross the width of the moon in a minute. It’s big, around 340 meters across and at its closest approach it will be about 19,000 miles from Earth, a lot closer than the moon and as close as some satellites in geostationary orbit.
This close approach will give scientists an unprecedented opportunity for examination of the asteroid surface from Earth. The approach of Apophis was discussed at the International Academy of Astronautics Planetary Defence conference in the US last week, where scientists considered means of detecting, tracking and characterising near-Earth objects and exploring means to deflect those that could potentially impact.
It also examined emergency procedures if and when an impact does occur.
“The Apophis close approach in 2029 will be an incredible opportunity for science,” said radar scientist Marina Brozović from the NASA Jet Propulsion Laboratory in Pasadena, California.
“We’ll observe the asteroid with both optical and radar telescopes. With radar observations, we might be able to see surface details that are only a few metres in size.”
Apophis was first spotted by astronomers at the Kitt Peak National Observatory in Arizona, USA, in June 2004, then located again by the Siding Springs Observatory in NSW in 2007.
Astronomers calculated there was a 2.7 per cent chance it would hit the Earth. But as the asteroid’s orbit became better known, impact was ruled out but there would still be a very close encounter.
Apophis will certainly be visible from Australia without optical aids, travelling east to west over the Australian mainland. It’s closest approach to Earth will be over the Atlantic Ocean.
Apophis will then head out into the solar system, returning to Earth in 2036 when there’s a one in 45,000 chance it will strike. Paul Chodas, director of the JPL Center for Near Earth Objects Studies (CNEOS) said Apophis is a representative of about 2,000 currently known Potentially Hazardous Asteroids (PHAs).
“By observing Apophis during its 2029 flyby, we will gain important scientific knowledge that could one day be used for planetary defence,” he said.
Asteroid strikes on earth have long been a staple of science fiction movies. While the chances are low the consequences could be devastating for life on Earth and scientists have been thinking seriously about how to deal with such a threat.
Receive the latest developments and updates on Australia’s space industry direct to your inbox. Subscribe today to Space Connect here. | 0.859914 | 3.586981 |
Scientists reveal solar system's oldest molecular fluids could hold the key to early life
The oldest molecular fluids in the solar system could have supported the rapid formation and evolution of the building blocks of life, new research in the journal Proceedings of the National Academy of Sciences reveals.
An international group of scientists, led by researchers from the Royal Ontario Museum (ROM) and co-authors from McMaster University and York University, used state-of-the-art techniques to map individual atoms in minerals formed in fluids on an asteroid over 4.5 billion years ago.
Studying the ROM's iconic Tagish Lake meteorite, scientists used atom-probe tomography, a technique capable of imaging atoms in 3-D, to target molecules along boundaries and pores between magnetite grains that likely formed on the asteroid's crust. There, they discovered water precipitates left in the grain boundaries on which they conducted their ground-breaking research.
"We know water was abundant in the early solar system," explains lead author Dr. Lee White, Hatch postdoctoral fellow at the ROM, "but there is very little direct evidence of the chemistry or acidity of these liquids, even though they would have been critical to the early formation and evolution of amino acids and, eventually, microbial life."
This new atomic-scale research provides the first evidence of the sodium-rich (and alkaline) fluids in which the magnetite framboids formed. These fluid conditions are preferential for the synthesis of amino acids, opening the door for microbial life to form as early as 4.5 billion years ago.
"Amino acids are essential building blocks of life on Earth, yet we still have a lot to learn about how they first formed in our solar system," says Beth Lymer, a Ph.D. student at York University and co-author of the study. "The more variables that we can constrain, such as temperature and pH, allows us to better understand the synthesis and evolution of these very important molecules into what we now know as biotic life on Earth."
The Tagish Lake carbonaceous chondrite was retrieved from an ice sheet in B.C.'s Tagish Lake in 2000, and later acquired by the ROM, where it is now considered to be one of the museums iconic objects. This history means that the sample used by the team has never been above room temperature or exposed to liquid water, allowing the scientists to confidently link the measured fluids to the parent asteroid.
By using new techniques, such as atom probe tomography, the scientists hope to develop analytical methods for planetary materials returned to Earth by space craft, such as by NASA's OSIRIS-REx mission or a planned sample-return mission to Mars in the near future.
"Atom probe tomography gives us an opportunity to make fantastic discoveries on bits of material a thousand times thinner than a human hair," says White. "Space missions are limited to bringing back tiny amounts of material, meaning these techniques will be critical to allowing us to understand more about the solar system while also preserving material for future generations." | 0.852281 | 3.834049 |
Thermonuclear explosions on the surface of white dwarf stars are relatively frequent in the Universe and are divided between those that are more recurrent - the new classics - and the explosions that repeat over decades - the novae remnants.
A team of international researchers, including Valério Ribeiro (a researcher of the University of Aveiro and a IT collaborator), studied for the first time the results of thousands of these latest explosions in Andromeda, the galaxy closest to the Milky Way. The work has just been published in the prestigious journal Nature.
This study demonstrates that repeated explosions create a 'super-remnant' cloud larger than many remnants of supernova explosions. "This is because the various recurrent bursts that occur annually sweep the interstellar material, creating cavities in the space around the nova", explains Valério Ribeiro.
These explosions expel several chemical elements that are essential to life (hydrogen and helium in greater quantity, but also oxygen, iron, carbon, etc.) creating a cloud called the "remnant." The explosions cause the material to be distributed through the interstellar medium where new stars and planets are being formed. These clouds of chemical elements scattered by repeated explosions can reach 440 light years, 1000 million times the distance between Earth and Jupiter.
"Andromeda is an excellent laboratory for the study of novas, because in our galaxy the remnants are overshadowed by interstellar dust, which is opaque to visible light. To eliminate the problem of dust, astronomers can observe the novas through radio waves, for which the dust is transparent", says Valério Ribeiro.
Portuguese astronomers associated with ENGAGE SKA (wich is led by IT, under the coordination of Domingos Barbosa), in collaboration with a multidisciplinary team from South Africa, UK, France, the Netherlands, and others, will work with data from the forthcoming Square Kilometer Array (SKA) radio telescope, which is being built in South Africa and Australia, in order to discover all the novas in our galaxy.
Valério Ribeiro points out that the mapping of all the novas in our galaxy "helps us understand the distribution of chemical elements and how they enrich other planets in formation, creating conditions for the emergence of life-critical molecules as it has occurred with the Earth a few thousand million years ago".
Photo: This is a composite image of Liverpool Telescope data (bottom left) and Hubble Space Telescope data (top right) of the nova super-remnant. Credit: Matt Darnley / LJMU | 0.905561 | 4.073575 |
Five planets orbiting a star have been discovered outside our solar system, thanks to a crowdsourcing effort that enlisted the help of about 10,000 citizen scientists worldwide to comb through data collected by the Kepler space telescope, the Massachusetts Institute of Technology said.
The exoplanets are orbiting a star in the constellation Aquarius, nearly 620 light years from Earth, MIT said in a statement. They are two to three times larger than Earth.
The new findings were presented Thursday by researchers from MIT and the California Institute of Technology at the meeting of the American Astronomical Society.
The data from the telescope are composed of light curves, or graphs of light intensity from stars. Dips in starlight indicate transits, or objects crossing in front of the stars, MIT said.
Ian Crossfield, assistant professor of physics at MIT, who at the time was a Sagan fellow at the University of California at Santa Cruz, worked last year with fellow astronomer Jesse Christiansen at Caltech to enlist volunteers for the Exoplanet Explorers program, MIT said.
“We put all this data online and said to the public, ‘Help us find some planets,’ ” Crossfield said in the statement. “It’s exciting because we’re getting the public excited about science, and it’s really leveraging the power of the human cloud.”
Using a citizen scientist platform called Zooniverse, people were able to review actual light curves and click “yes” or “no,” depending on whether they thought it looked as if a transit had taken place.
The researchers got a boost when an Australian television program, “Stargazing Live,” featured it, MIT said.
“It turns out the world is big enough that there’s a lot of people who are interested in doing some amateur science,” Crossfield said.
“We also look at the data with machines, but the human brain provides a complementary approach that can pick out signals missed by computers,” he said in an e-mail.
Crossfield and Christiansen, along with NASA astronomer Geert Barentsen, looked at what the citizen scientists had flagged and determined that more than 200 of them were objects of interest.
They did further research on the five planets in the new system, K2-138 — the single biggest system that was found — before submitting their work to the Astrophysical Journal, which has accepted it.
“We are working on finalizing analysis and follow-up observations from ground-based telescopes of these other systems, which we also intend to eventually publish,” Crossfield said. | 0.890952 | 3.176574 |
Georges Lemaître: the Belgian priest who preached the Big Bang
Even Einstein initially found Lemaître’s ‘big bang’ model of the origins of the universe far-fetched
As pointed out by Brian Maye in a recent article in this newspaper, this month marked the 50th anniversary of the death of Monsignor Georges Lemaître, the Belgian cleric and physicist who first suggested the theory now known as the Big Bang model of the universe. How did it come to pass that one of the most famous theories of modern science was first proposed by an obscure Belgian priest?
Lemaître was born in Charleroi, Belgium, in 1894. After attending the Jesuit secondary school there, he studied civil engineering at the Catholic university of Louvain. These studies were interrupted by the outbreak of the first World War. After serving as an artillery officer in the Belgian army, he switched to mathematics and physics, completing a master’s degree in one year.
In 1920 Lemaître entered the seminary of Malines to study for the priesthood. He was permitted to continue his studies in physics, specialising in the field of Einstein’s general theory of relativity (the modern theory of gravity). He was ordained a priest in 1923. He won a prestigious scholarship to study with Arthur Eddington, a world-renowned authority on astronomy and general relativity at the University of Cambridge. Following a glowing recommendation from Eddington, Lemaître was accepted for further studies in astronomy and cosmology at Harvard University and at Massachusetts Institute of Technology.
At this time, a great upheaval was taking place in the world of astronomy. Thanks to the pioneering observations of American astronomers such as Edwin Hubble and Vesto Slipher, it was becoming clear that distant astronomical objects known as “spiral nebulae’ constituted distinct galaxies far beyond the confines of our own Milky Way, and that these distant galaxies were racing away from us at high speed.
Lemaître’s first great contribution to science was to provide a convincing explanation for this bizarre phenomenon. Displaying a stunning mastery of Einstein’s general theory of relativity, he showed the theory predicted an expansion of space on the largest scales. He concluded that the runaway galaxies were a manifestation of this stretching of space. This ground-breaking proposal did not receive much attention at first, but with the publication of Hubble’s definitive observations of the nebulae in 1929, the community took notice. By 1931 most researchers in the field had accepted the astonishing idea of an expanding universe.
Great ball of fire
So, Lemaître’s model of a universe that was once a primeval fireball received little support from the community for 30 years. However, in 1965, radio astronomers at Bell lab reported the discovery of a ubiquitous background radio signal of unknown extragalactic origin. With the help of some colleagues at Princeton University, it was eventually realised that the mysterious signal constituted radiation left over from a universe that was once much smaller and hotter: the first direct evidence of the primeval fireball.
Today, intense studies of this “cosmic background radiation” by giant terrestrial and satellite telescopes have yielded an astonishingly detailed picture of our universe as it was billions of years ago. However, it should be pointed out that such studies tell us little about the origin of the universe. Indeed, the term “big bang” is one of science’s great misnomers: how the universe got into the state of a concentrated fireball remains beyond the reach of science at this time.
As for Lemaître, he lived just long enough to learn of the discovery of the cosmic background radiation on his deathbed. History does not record whether he said “I told you so”.
Dr Cormac O’Raifeartaigh lectures in physics at Waterford Institute of Technology and is a fellow of the Royal Astronomical Society | 0.827409 | 3.179909 |
A dwarf planet discovered over a decade ago is the largest body we know of in our solar system without a proper name – but that’s about to change.
Meg Schwamb, an astronomer at Gemini Observatory in Hawaii, and her colleagues have opened a public vote to name the distant world, which is currently known only as 2007 OR10. They have selected three potential names that fit the International Astronomical Union’s (IAU) rules on official names for minor planets, and will recommend the winner to the IAU, which will then select the formal name.
So why now, instead of when the researchers discovered OR10 in 2007? “You can’t name something when you don’t know anything about it,” says Schwamb. “When we found it, I knew the orbit and generally the size.” Now, after lots of follow-up observations, we know more than just that it is about 1250 kilometres across and orbits beyond Pluto in the Kuiper belt.
We know that its surface is covered in water ice, with traces of methane ice. When sunlight hits the methane ice, it turns red, which may be why OR10 is one of the reddest rocks in the Kuiper belt. The water ice may have welled up from deep inside OR10 sometime in its past through cryovolcanism.
“It went from being this point of light to a whole world,” says Schwamb. And a world must have a name. The three names Schwamb and her colleagues have proposed are Gonggong, a Chinese water god who caused floods and chaos, Holle, a winter spirit from European folk tales who is associated with fertility and rebirth, and Vili, a Nordic god and brother of Odin. The vote is now open to the public.
Even though OR10 is small, it has its own moon with a diameter of less than 250 metres, but that was discovered by another team, meaning Schwamb and her colleagues aren’t able to suggest names to the IAU. “Once we have a name for the primary object we can get a name for the moon,” she says.
More on these topics: | 0.836583 | 3.212146 |
Project Leader: Prof. Ben Moore
The aim of this project is to study in detail some of the key processes involved during the formation and evolution of planetary systems, from the collapse of the proto-stellar cloud through to the formation of rocky earth-like planets. Insights into the various phases of this complex evolution can be obtained through supercomputer calculations using several state-of-the-art numerical codes developed in Zurich that follow the hydro-dynamical and collisional processes that drive planet formation. Amongst the key goals are: to test and compare models of planet formation with observational data, to make predictions for the statistical properties of planet populations, to explore the long term evolution and stability of planetary systems, to study the accretion history of terrestrial planets and the radial elemental abundances, and to explore the frequency of habitable planetary systems in different environments of our Galaxy.
Our project is split into two parts that will allow us to simulate planet formation across the distinct epochs that occur over the ~100 million year timescale that planet formation takes place:
- The first part led by Prof. Lucio Mayer, explores the early formation phase including the mass inflow rates into the forming star and surrounding proto-planetary disk. This project will also target the subsequent evolution of the gaseous disk and the formation of gas-giant planets.
- The second part led by Dr. Joachim Stadel, aims to develop the numerical tools and techniques to study the formation and long term evolution of rocky Earth-like planets. These tools will then be applied to make statistical libraries of numerical solar systems for comparison with data and to make predictions for new observational strategies.
Ultimately, these techniques allow us to also investigate fascinating science questions, such as the stability of planetary systems, to study the accretion histories of planets and to quantify the radial mixing of elements. Our long term goal would be to merge these techniques together so that we can carry out fully self-consistent simulations of the combined gaseous and rocky components.
Prof. Lucio Mayer
Understanding the formation of planets requires first to understand the origin and development of their natal places, namely protoplanetary disks around young stars. From observational evidence disks are known to evolve through various phases in which several complex processes take place, regulating mass transport, thermodynamics and the gathering of gaseous and solid matter into planets. Read more >>
Dr. Joachim Stadel
This part of our project focuses in detail on the late stages of planet formation using direct N-body simulations which follow all the gravitational interactions between planetesimals over hundreds of millions of orbits, including an accurate treatment of close approaches of multiple bodies as well as their collisions.
Read more >> | 0.875806 | 3.772048 |
For most of us, asteroids exist primarily as a threat. An asteroid that landed around the Yucatan peninsula, after all, is generally considered to have set into motion the changes that resulted in the elimination of the dinosaurs.
Other large in-coming asteroids laid waste to swaths of Siberia in 1908, dug the world’s largest crater (118 mile wide) in South Africa long ago, and formed the Chesapeake Bay a mere 35 million years past. And another large asteroid will almost certainly threaten Earth again some day.
There is, however, a reverse and possibly life-enhancing side to the asteroid story, one that is becoming more clear and intriguing as we learn more about them where they live. Asteroids not only contain a lot of water — some of it possibly delivered long ago to a dry Earth — but they contain some pretty complex organic molecules, the building blocks of life.
The latest chapter in the asteroid saga is being written about Ceres, the largest asteroid in the solar system and recently declared to also be a dwarf planet (like Pluto.)
Using data from NASA’s Dawn spacecraft, a team led by the National Institute for Astrophysics in Rome and the University of California, Los Angeles identified a variety of complex organic compounds, amino acids and nucleobases — the kind that are the building blocks of life. The mission has also detected signs of a possible subsurface ocean as well as cryovolcanos, which spit out ice, water, methane and other gases instead of molten rock.
“This discovery of a locally high concentration of organics is intriguing, with broad implications for the astrobiology community,” said Simone Marchi, a senior research scientist at Southwest Research Institute and one of the authors of the paper in Science. “Ceres has evidence of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and now organic materials.”
He said that the organic-rich areas include carbonates and ammonia-based minerals, which are Ceres’ primary constituents. Their presence along with the organics makes it unlikely that the organics arrived via another asteroid.
In an accompanying comment in the Feb. 16 edition of Science, Michael Küppers of the European Space Astronomy Center in Madrid makes the case that Ceres might once have even been habitable.… Read more | 0.824576 | 3.511843 |
Pasadena, CA— Sometimes there is more to a planetary system than initially meets the eye.
Ground-based observations following up on the discovery of a small planet by NASA’s Transiting Exoplanet Survey Satellite (TESS) revealed two additional planets in the same system, one of which is located far enough from its star to be potentially habitable. These findings were announced in Astronomy & Astrophysics by an international team that included several Carnegie astronomers and instrumentation specialists.
The newly found exoplanets orbit a star named GJ 357, an M-type dwarf that’s about one-third of the Sun’s mass and located 31 light-years away in the Hydra constellation. In February, TESS cameras caught the star dimming slightly every 3.9 days, revealing the presence of an exoplanet transiting or passing across its face and dimming its light in every orbit.
The transits that TESS observed belong to GJ 357 b, a planet about 80 percent more massive than Earth and about 22 percent larger in size. It orbits 11 times closer to its star than Mercury does our Sun. This gives it an equilibrium temperature of around 490 degrees Fahrenheit (254 degrees Celsius), leading the team to call it a “hot Earth.” They say these conditions make it one of the best exoplanets discovered to date for research on exoplanet atmospheric compositions.
To confirm the TESS-detected planet’s presence, the discovery team, which was led by Rafael Luque of the Institute of Astrophysics of the Canary Islands on Tenerife, used additional data from ground-based observatories, which revealed two additional, non-transiting planets.
“In a way, these planets were hiding in measurements made at numerous observatories over many years,” Luque said. “It took TESS to point us to an interesting star where we could uncover them.”
These additional worlds were found by measurements using the radial velocity method of exoplanet detection, which takes advantage of that fact that not only does a star’s gravity influence the planet orbiting it, but the planet’s gravity also affects the star in turn. This creates tiny wobbles in the star’s orbit that can be detected using advanced instruments, such as the Planet Finder Spectrograph on one of the Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile.
“Because it is a nearby M dwarf, which we know often host small planets, the PFS team started monitoring this star in 2016,” explained Carnegie’s Johanna Teske. “As soon as we saw that TESS had indeed detected a small transiting planet, we accelerated our PFS observing campaign.”
The mission’s goal of determining the masses of 50 small planets necessitates collaborations with ground-based observatories like Las Campanas, since planet mass is not a parameter that TESS measures.
Carnegie’s Sharon Wang noted, “This planetary system helps demonstrate how crucial tools such as the PFS are for TESS’ success.”
All of PFS team members—which also includes Fabo Feng, Paul Butler, Jeff Crane, and Stephen Shectman—are co-authors on the paper announcing the discoveries.
GJ 357 c, which has a mass at least 3.4 times Earth’s, orbits the star every 9.1 days at a distance of a bit more than twice its sibling GJ 357 b. It has an equilibrium temperature of around 260 Fahrenheit (127 Celsius).
GJ 357 d, the system’s farthest-known planet, has a mass at least 6.1 times Earth’s, and orbits the star every 55.7 days at a distance of about 20 percent of that between Earth and the Sun. The planet’s size and composition are unknown, but with an equilibrium temperature of -64 Fahrenheit (-53 Celsius), the planet seems more glacial than habitable. Future studies are needed to determine if it has a dense atmosphere, but if so, it could trap enough heat to warm its surface enough to host liquid water.
Studying the detailed composition of the atmospheres of nearby exoplanets will be a task for NASA’s James Webb Space Telescope, slated to launch in 2021, and by the new generation of so-called “extremely large” ground-based telescopes now under construction, including the Giant Magellan Telescope, which is being built at Las Campanas.
Top Right Image Caption: An artist’s illustration of the GJ357 system, courtesy of Carl Sagan Institute/Jack Madden
TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide are participants in the mission. | 0.894169 | 3.831282 |
When the New Horizons spacecraft launched, Pluto was still considered a planet. Now, eight years later, the space probe is finally nearing the end of its 2.9 billion-mile journey to Pluto—and has just roused itself from deep hibernation ahead of its arrival.
The New Horizons Spacecraft is the first step of NASA's $650 million New Frontiers program. It's about the size of a grand piano and is powered by a small nuclear engine. Fun fact: New Horizons notched the highest launch speed in NASA's history when it lifted off in 2006 aboard an Atlas V rocket from Cap Canaveral. Shot directly into a solar escape trajectory, New Horizons sped towards Pluto at more than 37,000 mph—just a hair slower than Voyager 1, which exited our solar system traveling at 38,350 mph.
The spacecraft's mission is a simple one: Discover how Pluto and its oversized moon, Charon, came to exist as a binary planet, and also what Pluto's surface and atmospheric compositions really are. The dwarf planet is so ludicrously far away from the Sun, we've never really studied it up close, and that's exactly what New Horizons is built to do.
In July of next year, the spacecraft should reach its nearest flyby point of Pluto, upon which a suite of on-board long range imaging and sensing instruments will go to work. Though, at 37,000 mph, they'll have to work fast. Once New Horizons is done with Pluto—and assuming it's still functional after all that time in interplanetary space—New Horizons will attempt to study objects floating around the Kuiper Belt. You know the Kuiper belt: It's where the asteroid that wiped out the dinosaurs came from.
Both Pluto itself and numerous space rocks floating about the Kuiper belt are known to be heavily laden with ancient, organic compounds. So who knows—we may just luck out and discover extraterrestrial life in our own solar back yard. [New Scientist - Johns Hopkins - Wiki - NASA] | 0.855184 | 3.277137 |
|Large asteroid hitting Earth (stock illustration).|
The Younger Dryas lasted a thousand years and coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. In the 1980s, some researchers put forward the idea that the cool period, which fell between two major glaciations, began when a comet or meteorite struck North America.
In the new study, published online in the Journal of Archaeological Science, scientists analyzed siliceous scoria droplets -- porous granules associated with melting -- from four sites in northern Syria dating back 10,000 to 13,000 years ago. They compared them to similar scoria droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas.
"For the Syria side, the impact theory is out," said lead author Peter Thy, a project scientist in the UC Davis Department of Earth and Planetary Sciences. "There's no way that can be done."
The findings supporting that conclusion include:
- The composition of the scoria droplets was related to the local soil, not to soil from other continents, as one would expect from an intercontinental impact.
- The texture of the droplets, thermodynamic modeling and other analyses showed the droplets were formed by short-lived heating events of modest temperatures, and not by the intense, high temperatures expected from a large impact event.
- And in a key finding, the samples collected from archaeological sites spanned 3,000 years. "If there was one cosmic impact," Thy said, "they should be connected by one date and not a period of 3,000 years."
So if not resulting from a cosmic impact, where did the scoria droplets come from? House fires. The study area of Syria was associated with early agricultural settlements along the Euphrates River. Most of the locations include mud-brick structures, some of which show signs of intense fire and melting. The study concludes that the scoria formed when fires ripped through buildings made of a mix of local soil and straw. | 0.879531 | 3.27387 |
The transit or passage of a planet across the face of the Sun is a relatively rare occurrence to view.
"This Monday is called the transit of Mercury, where Mercury passes in front of the image of the Sun as we look at it from the Earth". Greg Scheiderer's Seattle Astronomy blog lists several, including a gathering that he's planning to host at Seacrest Marina Park in West Seattle at 7 a.m. PT Monday (weather permitting).
The entire 5 ½-hour event will be visible, weather permitting, in the eastern USA and Canada, and all Central and South America. Asia and Australia will miss out.
According to the Delta College Planetarium, the next transit of Mercury won't be until 2032 and the next time Mercury passes this close to the center of the sun will not be until 2187. The next transit of Mercury is in 2032. Earthlings get treated to just 13 or 14 Mercury transits a century.
If you have a solar scope or filter, take it along. There's no harm in pulling out the eclipse glasses from the total solar eclipse across the USA two years ago, but it would take "exceptional vision" to spot minuscule Mercury, said NASA solar astrophysicist Alex Young.
"That's really close to the limit of what you can see", he said earlier this week.
"I was far from suspecting that Mercury would project such a small shadow", Gassendi wrote. Venusian transits are even rarer, happening on average only once a century. The next one isn't until 2117. When Mercury's leading edge first touches the sun, the planet will appear to grow a narrow neck connecting it to the edge of the sun, making the silhouette look like a teardrop.
Clouds won't be a problem for NASA's Solar Dynamics Observatory, however. Scientists will use the transit to fine-tune telescopes, especially those in space that can not be adjusted by hand, according to Young. From this data, astronomers can then calculate the size, orbit, and even some physical properties of these alien worlds. Periodic, fleeting dips of starlight indicate an orbiting planet.
Astronomers say transits of Mercury are not as historically important as transits of Venus due to its very small, angular size compared to the diameter of the sun. | 0.837014 | 3.208724 |
Our Location In The Universe
Another reason why there hasn't been any Direct Meetings With Aliens may have to do with our location in the Milky Way Galaxy and even the wider universe. We are almost on the outskirts of a very huge galaxy with the center having many enormous stars and a black hole! We, in other words are like a small village far from the big city - there is no rush to visit us, no one might even know about us.
Image from NASA - where we are in the Milky Way.
Our Location In The Universe (Hover)
I guess it will have to depend on how long these very advanced aliens have had their technology to visit other solar systems without taking much time to do it. Really, our step up from primitive man has only been about 10,000 years if that. If anyone passed through here before that they have thought the planet wasn't worth the visit.
ATLASGAL Survey Of Milky Way Completed
Science Related News
A spectacular image of the Milky Way has been released to mark the completion of the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The APEX telescope has mapped the full area of the Galactic Plane visible from the southern hemisphere for the first time at submillimeter wavelengths and in finer detail than space-based surveys. The APEX telescope allows the study of the cold universe, a few tens of degrees above absolute zero.
A source accelerating Galactic cosmic rays to unprecedented energy discovered at the center of the Milky Way
For more than ten years the H.E.S.S. Observatory in Namibia, run by an international collaboration of 42 institutions in 12 countries, has been mapping the center of our galaxy in very-high-energy gamma rays. These gamma rays are produced by cosmic rays from the innermost region of the Galaxy. A detailed analysis of the latest H.E.S.S. Data reveals for the first time a source of this cosmic radiation at energies never observed before in the Milky Way: the supermassive black hole at the center of the Galaxy, likely to accelerate cosmic rays to energies 100 times larger than those achieved at the largest terrestrial particle accelerator Ref. Source 6b.
Cosmic beacons reveal the Milky Way's ancient core
Astronomers have discovered that the central 2000 light years within the Milky Way Galaxy hosts an ancient population of stars. These stars are more than 10 billion years old and their orbits in space preserve the early history of the formation of the Milky Way. For the first time the team kinematically disentangled this ancient component from the stellar population that currently dominates the mass of the central Galaxy. Ref. Source 2b.
Measuring the Milky Way: One massive problem, one new solution
It is a galactic challenge, to be sure, but Gwendolyn Eadie is getting closer to an accurate answer to a question that has defined her early career in astrophysics: what is the mass of the Milky Way? Ref. Source 1w.
Astronomers discover dizzying spin of the Milky Way galaxy's 'halo'
Astronomers have discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy's disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies. Ref. Source 2x.
Milky Way had a blowout bash 6 million years ago
The center of the Milky Way galaxy is currently a quiet place where a supermassive black hole slumbers, only occasionally slurping small sips of hydrogen gas. But it wasn't always this way. A new study shows that 6 million years ago, when the first human ancestors known as hominins walked the Earth, our galaxy's core blazed forth furiously. The evidence for this active phase came from a search for the galaxy's missing mass. Ref. Source 6w. | 0.8623 | 3.233145 |
In 1923, Edwin Hubble discovered the universe—or rather, he discovered a star, and humans learned that the Milky Way wasn’t the whole of the cosmos. Less than 100 years later, thanks to the telescope named after him, NASA scientists estimate the universe contains at least 100 billion galaxies, and who-knows-what beyond that. The exponential growth of astronomical data collected since Hubble’s time is absolutely staggering, and it developed in tandem with the revolutionary increase in computing power over an even shorter span, which enabled the birth and mutant growth of the internet.
Modern “maps” of the internet can indeed look like sprawling clusters of star systems, pulsing with light and color. But the “weird combination of physical and conceptual things," Betsy Mason remarks at Wired, results in such an abstract entity that it can be visually illustrated with an almost unlimited number of graphic techniques to represent its hundreds of millions of users. When the internet began as ARPANET in the late sixties, it included a total of four locations, all within a few hundred miles of each other on the West Coast of the United States. (See a sketch of the first four “nodes” from 1969 here.)
By 1973, the number of nodes had grown from U.C.L.A, the Stanford Research Institute, U.C. Santa Barbara, and the University of Utah to include locations all over the Midwest and East Coast, from Harvard to Case Western Reserve University to the Carnegie Mellon School of Computer Science in Pittsburgh, where David Newbury’s father worked (and still works). Among his father’s papers, Newbury found the map above from May of '73, showing what seemed like tremendous growth in only a few short years.
The map is not geographical but schematic, with 36 square “nodes”—early routers—and 42 oval computer hosts (one popular mainframe, the massive PDP-10, is sprinkled throughout), and only naming a few key locations. Significantly, Hawaii appears as a node, linked to the mainland by satellite. Just above, you can see an update from just a few months later, now representing 40 nodes and 45 computers. “The network,” writes Selina Chang, “became international: a satellite link connected ARPANET to nodes in Norway and London, sending 2.9 million packets of information every day.”
These early networks of global interconnectivity, created by the Defense Department and used mostly by scientists, predate Tim Berners-Lee and CERN’s development of the World Wide Web in 1991, which opened up the enormous, expanding alternate universe we know as the internet today (and was, coincidentally, invented around the same time as the Hubble Telescope). Though maps aren’t territories (a 1977 ARPANET “logical map” disclaims total accuracy in a note at the bottom), these early representations of the internet resemble medieval maps of the cosmos next to the beautiful complexity of glowing colors we see in 21st century infographics like the authoritatively-named “The Internet Map.” | 0.806946 | 3.5068 |
Jupiter (upper right) and Venus (left) Feb. 10, 2012 6:50 PM
Jupiter and Venus, the two great and famous luminaries of heaven are now 30° apart in the western sky during early evening and are moving closer to each other by roughly one degree each day.
Jupiter, king of planets, has been our constant evening companion for the last six months. Only Venus outshines Jupiter among the planets and stars. Venus and Jupiter are so bright you might think you’ve witnessed a double supernova beaming through the evening twilight. But, no, it’s just the two brightest planets in our own solar system.
Over the next couple weeks, Venus and Jupiter will continuously reign the evening sky; only the moon will be brighter. The planets will continue to get closer and closer to one another until March.
On the evenings of February 24, 25 and 26, the thin lunar crescent will pass close to Venus and Jupiter.
By March 14 and 15, these two bright objects will be on a spectacular conjunction — the closest in 2012. The next Venus-Jupiter conjunction after this one falls on May 28, 2013.
At the moment of closest approach, Venus will be at mag -4.9, and Jupiter at mag -2.1, both in the constellation Aries. The pair will be too widely separated to fit within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.
After this event, Venus and Jupiter will remain close throughout the month of March 2012. They are like twin beacons – two very bright planets – near each other in the west as soon as the sun goes down.
This year’s Orionids will peak on the evening of October 21/22 . These meteor fragments radiate from the top of Orion’s upraised club, near the Gemini border.
The cometary debris left behind by Comet Halley — bits of ice, dust and rubble — create the Orionid meteor shower. It last visited Earth in 1986. As the comet moves through space, it leaves debris in its wake that strikes Earth’s atmosphere most fully around October 20-22. Around this time every year, Earth is more or less intersecting the comet’s orbit.
Meteor specialists have meteor counts for this pass averaging a modest 20 per hour under dark skies. The moonlit glare of the waning crescent Moon, however will probably reduce the numbers somewhat this year.
The best time to view these meteors is usually in the wee hours before dawn. That time holds true no matter what time zone you’re in.
Clear skies to all and happy viewing! 🙂
- Stellarium planetarium software | 0.887967 | 3.452195 |
LOFAR radio observations document rejuvenation in space
In observations of galaxy clusters, astronomers in collaboration with the MPA discovered a new class of cosmic radio sources. With the digital radio telescope Low Frequency Array (LOFAR) they received the longest radio waves that can be measured on Earth. They identified a remarkable "tail"behind a galaxy in the radio light, which must have been re-energized after it had faded away. In the journal Science Advances, the team describes this discovery, which either confirms a theoretical prediction on the interaction between shock waves and radio plasma or represents a novel phenomenon.
Looking into space with the help of radio telescopes, astronomers often find long, radio-luminescent tails behind wandering galaxies. These tails occur when the active black hole in the center of a galaxy produces clouds of energetic electrons with typical velocities close to the speed of light. These clouds then stay behind the galaxy, which is traveling through the gas filling the intergalactic space.
Normally, these luminous trails fade over time until they are not visible anymore, as the electrons radiate their energy away. However, a group of researchers from Germany, Italy, the Netherlands and the United States observed the galaxy cluster Abell 1033 at very low radio frequencies and found that one of the tails was behaving contrary to expectations, starting to glow again in the galaxy gas (see figure).
This is surprising as the electron clouds that make up the tail gradually release their energy. They should therefore fade until they finally disappear completely. Instead, in this case, the observed tail still shines after more than a hundred million years - and what is more, it is located in the middle of a cluster in which several galaxies are merging.
For Dr. Torsten Enßlin at the MPA, however, this was not a surprise, but rather the confirmation of his prediction. In 2001, in cooperation with Indian scientist Gopal Krishna (IUCAA), he postulated a connection between gas dynamics in galaxy clusters and a rejuvenation of radio plasma. When radio plasma is compressed via shock waves, electrons gain energy adiabatically, just like molecules in a bicycle pump get heated via compression. If enough energy was transferred, the electrons become visible again in the frequency range of radio telescopes. It is important to note that compression has to happen fast enough so that it outperforms the simultaneous loss of energy via radiation, which makes the electrons invisible again. The recent discovery of a re-illuminated radio tail may therefore confirm the theory of Enßlin and Krishna. Torsten Enßlin was responsible for the theoretical interpretation of the observational data in the current project.
Nevertheless, the structures observed in Abell 1033 and their origin remain mysterious. The tail has gigantic dimensions and should be "dead" in the astrophysical sense, because only then can a radio tail rise from the ashes like a phoenix if a shock wave squeezes the gas over a long distance simultanously. The angle between tail and shock wave needs to be adjusted exactly, otherwise only a small region would light up. Either this special geometry is just a coincidence in this case, which could also explain why this phenomenon occurs so rarely in this size; or a completely different, as yet unknown, mechanism must be responsible for the rejuvenation.
The new discovery was made possible by a cooperation between the Indian Giant Meterwave Radio Telescope (GMRT) and the European Low Frequency Array (LOFAR). LOFAR is able to detect radio waves with a length of up to 30 meters. The unique telescope connects thousands of antennas located in eight different countries, their data converge in a supercomputer in Groningen (Netherlands). The computer collects 200 gigabytes of data per second and thus forms a virtual radio telescope, which is just as large as the European continent and can therefore pick up very long-wave and weak radio signals. MPA operates a LOFAR station in Unterweilenbach near Munich. | 0.830167 | 4.063601 |
If all goes according to plan, UMass Lowell will have a planet-finding telescope soaring to the edge of the atmosphere and a miniature satellite orbiting Earth this year. The telescope and satellite are being built and tested at the university’s Lowell Center for Space Science and Technology (LoCSST) by teams of UML students, faculty researchers, scientists and engineers.
“Both missions are firsts for UMass Lowell,” says Prof. Supriya Chakrabarti of the Department of Physics and Applied Physics, who is the principal investigator for both projects. “Our goal is to train the next generation of astronomers, space scientists and engineers through hands-on involvement in all phases of the mission, from instrument development to data analysis.”
The telescope project (dubbed PICTURE-C, which stands for Planetary Imaging Concept Testbed Using a Recoverable Experiment—Coronagraph) aims to develop and validate the technology necessary for detecting Jupiter-size planets orbiting nearby stars in the Milky Way. The project is funded with a five-year, $5.6 million grant from NASA. The team’s ultimate goal is to discover Earth-like planets around sun-like stars capable of supporting life.
“PICTURE-C will enable us to learn about debris disks around other stars and to gain a better understanding of the processes and dynamics that formed our own solar system,” explains Chakrabarti, who directs LoCSST. “But in order for us to do this, we have to fly the instrument to about 120,000 feet — roughly 3½ times higher than the typical cruising altitude of a passenger jetliner — to get above 99 percent of the Earth’s atmosphere. Atmospheric turbulence distorts and blurs our image of the stars.”
The telescope’s launch is set to take place this spring from NASA’s Columbia Scientific Balloon Facility in Palestine, Texas, where it will be carried aloft to the stratosphere using an unmanned helium balloon 400 feet wide and several stories high. The balloon’s launch window is tight, so any bad weather at the site can potentially delay the mission for days or weeks. A second balloon flight for PICTURE-C is planned for 2020.
TO THE THRESHOLD OF SPACE
“We’re extremely excited,” says LoCSST research scientist Christopher Mendillo. “We’ve done sounding rockets before, but PICTURE-C is our very first balloon mission. Balloons are an amazing platform to use for conducting cutting-edge exoplanet research because of their relatively low cost and long observing duration.”
PICTURE-C features a coronagraph, a specialized optical imaging system coupled to a 24-inch-diameter telescope designed to “mask,” or block out, the direct light from the star so that faint objects very close to the star—such as planets and interplanetary dust, which otherwise would be hidden in the star’s bright glare— can be studied in great detail. High winds in the upper atmosphere are expected to buffet the entire telescope. To keep the coronagraph aimed precisely at the target, the instrument is mounted on a special NASA gimbal platform in the balloon’s gondola that can compensate for any unwanted movements. PICTURE-C will use the platform in conjunction with an onboard active optical pointing control system designed and built by Mendillo and physics Assoc. Prof. Timothy Cook, who is the project’s co-investigator.
“This control system can optically stabilize the light coming out of the telescope and keep the coronagraph centered on the target star to an accuracy of one milliarcsecond, or better,” says Mendillo. “A milliarcsecond is equivalent to resolving an object approximately 2 meters wide on the surface of the moon, which is about 385,000 kilometers away.”
Unlike a sounding rocket, which offers an observing window that lasts only for a few minutes before the payload parachutes back to the ground, the helium balloon will keep PICTURE-C aloft as long as 10 hours. At the end of the mission, ground controllers will send a command to release PICTURE-C from the balloon. A parachute is then deployed to slow PICTURE-C down and allow it to land gently for reuse in the next mission.
Aside from Chakrabarti, Mendillo and Cook, the other members of the PICTURE-C team are LoCSST mechanical engineer Jason Martel and physics graduate students Kuravi Hewawasam and Glenn Howe. Other collaborators include researchers from NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center as well as Caltech, MIT, the Space Telescope Science Institute and the University of California, Santa Barbara.
STUDENT SPACE RESEARCH
In the meantime, a total of about 100 students from physics, math, computer science, mechanical engineering, electrical engineering and computer engineering have worked on the satellite project called SPACE HAUC (pronounced “Space Hawk”), which stands for Science Program Around Communications Engineering with High-Achieving Undergraduate Cadres. The project is funded with a two-year, $200,000 grant from NASA and is based on the CubeSat model used worldwide for Low Earth Orbit space research.
“SPACE HAUC is progressing well,” says Susanna Finn, a research scientist at LoCSST who is advising the team. “Currently, the students are building and testing the CubeSat components, and shortly we will be in our integration and testing phase, assembling the whole system and testing it.”
Once the satellite is flight-ready, the researchers will turn it over to Nanoracks, a Texas-based commercial CubeSat deployer, to prepare it for launch to the International Space Station (ISS), from where it will be released into orbit.
“Launch is currently scheduled in the fall, but these things can still change,” says Finn.
SPACE HAUC will be launched during a scheduled resupply mission to the ISS, either aboard a Northrop Grumman Antares rocket from the Wallops Island spaceport facility in Virginia or a SpaceX Falcon 9 rocket from Cape Canaveral, Florida.
“SPACE HAUC will be part of NASA’s ELaNa [Educational Launch of Nanosatellites] payload, along with other CubeSats from other schools and NASA research centers. Nanoracks will pack SPACE HAUC into a deployer, and once our satellite is in orbit, it will be released from the ISS,” says Finn.
The mission’s goal is to demonstrate the practicality of communicating at high data rates in the X band using a phased array of patch antennas on the CubeSat and electronic beam steering. The antennas will operate at frequencies of 7.2 to 8.3 gigahertz from an orbit of about 450 kilometers.
“The use of X-band signal has yet to be attempted in a CubeSat and, if successful, would aid future CubeSat applications and space exploration,” says Simthyrearch Dy, SPACE HAUC’s student program manager. Dy is an Honors College student and a computer science, physics and math triple major from Lowell.
“Many CubeSats transmit data to ground controllers in the S-band at an average speed of 2 to 5 megabits per second. SPACE HAUC seeks to increase the speed to 50 to 100 megabits per second,” he says.
The students plan to maintain a communication link between the satellite and ground stations at the university’s Olney Science Center on North Campus and the MIT Haystack Observatory in Westford, Mass. SPACE HAUC is expected to stay in orbit for about a year or more before it gradually loses altitude and falls back to Earth, disintegrating and burning up harmlessly high above the ground.
Finn says the students’ drive and dedication have impressed her from day one: “They have been very independent and self-motivated to dive right in and research and learn what they need to know.”
For some, the project has opened the door to new career possibilities.
“This experience has laid the groundwork for my eventual plan of working for NASA,” says Dy. “I have background knowledge from my studies in STEM, and now I have R&D experience in an actual space science mission. An opportunity like this doesn’t come around often, especially during one’s undergraduate years.”
He adds, “The Francis College of Engineering has recently started offering a minor in aerospace studies. Because of SPACE HAUC, I plan to pursue a Ph.D. in either astronomy or computer science.”
In addition to LoCSST, other SPACE HAUC research collaborators include the university’s Raytheon-UMass Lowell Research Institute and the Printed Electronics Research Collaborative, as well as the Massachusetts Space Grant Consortium, Raytheon, BAE Systems and Draper Laboratory. | 0.835477 | 3.392137 |
The highest highlight of 2009 was clearly the revival of the Hubble Space Telescope, a mission that blended moments of beauty and brute force 350 miles above the earth.
Or was it?
Maybe the top story was the reassessment of NASA’s plans for human spaceflight. After all, tens of billions of dollars could be at stake. Or maybe it was the series of victories in NASA-backed competitions that had gone unwon for years.
See more here…
Taken by astronaut William Anders from the Apollo 8 spacecraft, this December 1968 photo of Earth rising over the lunar surface would become one of the most famous images of the 20th century. Credit: NASA
NASA heads into 2010 with the bittersweet assignment of retiring the space shuttle after nearly three decades. But that’s not all the agency has planned: There are also launches of three new satellites aimed at better understanding the Earth’s climate and oceans, and the sun.
Two of the probes will examine Earth — specifically the concentration of salt in the world’s oceans and the presence of aerosol particles, such as soot, in the atmosphere. A third mission will study the sun and its effect on space weather including solar flares that can disrupt communication on Earth.
All three come at a critical time for NASA. Data from the two Earth probes will likely influence global-warming research, and the trio of launches could serve as bright spots in a year otherwise dominated by debate over the future of the agency’s manned space program.
“They are extraordinary timely,” said Michael Freilich, head of NASA’s Earth-science division, of the two Earth probes. “It is a quest for understanding of the Earth system and [to improve] our ability to predict how our wonderful environment and our planet is going to change in the future.”
Combined, the three missions will cost more than $1.5 billion.
Get the full details here…
“…we must choose between two assumptions: either the souls which move the planets are the less active the farther the planet is removed from the sun, or there is only one moving soul in the center of all the orbits, that is the sun, which drives the planet the more vigorously the closer the planet is, but whose force is quasi-exhausted when acting on the outer planets because of the long distance and the weakening of the force which it entails.” (in ref. 1, p 261)
As the story goes, on Christmas night 2,000 years ago, wise men followed a star in the night sky to reach the baby Jesus. NASA-Ames is following the stars too, looking for life on other worlds, and astronomers have a new celestial tool to help them.
“If we’re going to be looking for planets, earth-like planets are the key,” Foothill College Astronomy Department Chair Andrew Fraknoi said.
Fraknoi has loved astronomy since childhood. He says NASA’s Kepler mission is one of the most exciting in quite some time.
“In the last 16 years, we’ve discovered over 400 planets going around other stars, but the methods so far that we have been using only allowed us to find big planets like Jupiter,” Fraknoi said.
Kepler is a telescope designed to find planets orbiting other stars by looking for a break in the star light as a planet moves in front of it.
The challenge now is to find planets that are half to twice the size of the earth in the habitable zone of their stars, where it is possible that water and even life might exist.
Read the rest here…
Blue lines show Earth’s northern magnetic field and the magnetic north pole in an artist’s rendering. Credit: Stefan Maus, NOAA NGDC
Earth’s north magnetic pole is racing toward Russia at almost 40 miles (64 kilometers) a year due to magnetic changes in the planet’s core, new research says.
The core is too deep for scientists to directly detect its magnetic field. But researchers can infer the field’s movements by tracking how Earth’s magnetic field has been changing at the surface and in space.
Now, newly analyzed data suggest that there’s a region of rapidly changing magnetism on the core’s surface, possibly being created by a mysterious “plume” of magnetism arising from deeper in the core.
And it’s this region that could be pulling the magnetic pole away from its long-time location in northern Canada, said Arnaud Chulliat, a geophysicist at the Institut de Physique du Globe de Paris in France.
Read the rest here…
Dreamliner First Class seating Credit: Boeing Company
The successful test flight of the Boeing 787 Dreamliner this week marks not only the introduction of a next generation aircraft, but is also a technological milestone. For example, the aircraft makes extensive use of composite materials, making its airframe lighter, stronger, and more fuel efficient. But that’s just the start of many new innovations.
The larger, eye level windows have no sliding plastic shades for a reason. There is an electrostatic film sandwiched internally that can adjust the level of light which passes through them, individually controlled by passengers, as well as the flight crew. They act the same way as tinted windows, but with multiple levels of adjustment.
See the rest of the article here…
This artist’s conception shows the WISE telescope mapping the whole sky in infrared. The mission will unveil hundreds of thousands of asteroids, and hundreds of millions of stars and galaxies. Credit: NASA
NASA is getting ready to launch a new space telescope that will scan the entire sky for the infrared glow of hidden asteroids and stars that are close to Earth but too dim to be easily seen.
Unlike telescopes that look for visible light, the Wide-field Infrared Survey Explorer, or WISE telescope, will pick up infrared light. All objects that have any heat give off infrared light — and that includes things we normally think of as being cold. WISE will be able to see objects at a wide range of temperatures, from as cold as liquid nitrogen to as hot as molten aluminum, according to NASA.
To make sure WISE isn’t blinded by its own heat, it has to be kept supercold. It will work inside a giant thermos bottle called a cryostat, and hydrogen ice will keep the telescope at -438 degrees Fahrenheit. “We have now 40 pounds of solid hydrogen in our cryostat,” says William Irace, WISE project manager at NASA’s Jet Propulsion Lab in California. “Some people think it looks like R2D2 without wheels. It’s kind of a funny-looking thing.”
The funny-looking thing is about the size of a polar bear. A rocket will blast it into orbit around the Earth. NASA is targeting launch for Monday morning.
Once it reaches orbit, WISE will spend about six months taking over 1 million images that will be stitched together to create a panoramic, infrared view of the entire sky.
Read the rest of the story here…
Most astronomers today believe that one of the most plausible reasons we have yet to detect intelligent life in the universe is due to the deadly effects of local supernova explosions that wipe out all life in a given region of a galaxy.
While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it’s actually 13.7 billion, but stars didn’t form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe!
Certain rare stars -real killers -type 11 stars, are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary “core-collapse” supernova. Concrete proof of the core-collapse GRB model came in 2003.
Read the rest here…
Even more from NASA here: A Hypernova: The Super-charged Supernova and its link to Gamma-Ray Bursts
A new exhibit at the Smithsonian’s National Air and Space Museum asks the big questions: How can human spaceflight become routine? How can a home and workplace be created in the extreme environment of space? What does the future hold for humans in space?
“Moving Beyond Earth” at the Washington D.C. museum features launch-vehicle models representing the quest for space, telescopes brought back from the Hubble, the suit worn by space tourist Dennis Tito and other items from NASA’s space exploration history.
Read more here…
NASA’s launch of its Ares test rocket has Buzz Aldrin questioning the vehicle’s design and outlining the need for better rockets.
The launch of NASA’s new rocket, Ares I-X, on October 28 was the first test flight of a new launch vehicle since the Apollo missions. The flight was spectacular and historic, but the famous Apollo 11 astronaut Buzz Aldrin says it was little more than a half-a-billion dollar political show.
Read the rest of this great article at www.technologyreview.com | 0.929598 | 3.104525 |
NASA engineers have a new plan for pushing down on the heat probe of the InSight Lander, which has been stuck at the Martian surface for a year, according to a release of NASA's Jet Propulsion Laboratory (JPL) published on Friday.
The mission team plans to command the scoop on InSight's robotic arm to press down on the "mole," a mini pile driver designed to hammer itself as much as 5 meters down.
They hope that pushing down on the mole's top will keep it from backing out of its hole on Mars, as it did twice in recent months after nearly burying itself.
As part of the heat probe, the mole is a 40-centimeter-long spike equipped with an internal hammering mechanism. While burrowing into the soil, it is designed to drag with it a ribbon-like tether that extends from the spacecraft.
Temperature sensors are embedded along the tether to measure heat coming deep from within the planet's interior to reveal important scientific details about the formation of Mars and all rocky planets, including Earth.
The mole found itself stuck on Feb. 28, 2019, the first day of hammering. The InSight team has since determined that the soil here is different from what has been encountered on other parts of Mars. InSight landed in an area with an unusually thick duricrust, or a layer of cemented soil.
The mole needs friction from soil in order to travel downward; without it, recoil from its self-hammering action causes it to simply bounce in place, according to JPL.
Throughout late February and early March, InSight's arm will be maneuvered into position so that the team can test what happens as the mole briefly hammers.
Meanwhile, the team is also considering using the scoop to move more soil into the hole that has formed around the mole. This could add more pressure and friction, allowing it to finally dig down, according to JPL.
The InSight landed safely on Mars on Nov. 26 of 2018 for a two-year mission to explore the deep interior of the Red Planet.
Delta-X, a new NASA airborne investigation, is preparing to embark on its first field campaign in U.S. Mississippi River Delta in coastal Louisiana state, according to a release of NASA's Jet Propulsion Laboratory (JPL) on Wednesday.
Beginning in April, the Delta-X science team, led by Principal Investigator Marc Simard of JPL, will be collecting data by air and by boat to better understand why some parts of the delta are disappearing due to sea-level rise while other parts are not.
"Millions of people live on, and live from services provided by, coastal deltas like the Mississippi River Delta. But sea-level rise is causing many major deltas to lose land or disappear altogether, taking those services with them," Simard said.
"We hope to be able to predict where and why some parts of the region will disappear and some are likely to survive," he said.
Deltas protect inland areas from wind and flooding during storms. They serve as a first line of defense against sea-level rise, and they are home to many species of plants and wildlife.
The Mississippi River Delta, one of the world's largest, also helps to drive local and national economies via the shipping, fishing and tourism industries. But it is quickly losing land area, according to the release.
Over the course of two field campaigns, one in April and another in the fall, the Delta-X science team will investigate how and why sediment accumulates in some areas and not in others. They will also determine what areas are most susceptible to disappearing beneath rising seas.
The team will fly four times for each campaign, collecting data at both high and low tides to better understand how the tides impact the exchange of water and sediment between river channels and wetlands.
After processing the data, which is expected to take about nine months, the science team will use it to provide detailed models of the delta region and how it works.
"These models will empower local communities and resource managers with the information and prediction capabilities they need to make the necessary decisions to save and restore the delta," Simard said.
Larry Tesler, an icon of early computing, has died at the age of 74, reports the BBC.
Mr Tesler started working in Silicon Valley in the early 1960s, at a time when computers were inaccessible to the vast majority of people.
It was thanks to his innovations - which included the "cut", "copy" and "paste" commands - that the personal computer became simple to learn and use.
Xerox, where Mr Tesler spent part of his career, paid tribute to him.
"The inventor of cut/copy & paste, find & replace, and more, was former Xerox researcher Larry Tesler," the company tweeted. "Your workday is easier thanks to his revolutionary ideas."
Mr Tesler was born in the Bronx, New York, in 1945, and studied at Stanford University in California.
Larry Tesler: The Silicon Valley history man
After graduating, he specialised in user interface design - that is, making computer systems more user-friendly.
He worked for a number of major tech firms during his long career. He started at Xerox Palo Alto Research Center (Parc), before Steve Jobs poached him for Apple, where he spent 17 years and rose to chief scientist.
After leaving Apple he set up an education start-up, and worked for brief periods at Amazon and Yahoo.
In 2012, he told the BBC of Silicon Valley: "There's almost a rite of passage - after you've made some money, you don't just retire, you spend your time funding other companies.
"There's a very strong element of excitement, of being able to share what you've learned with the next generation."
'A counterculture vision'
Possibly Mr Tesler's most famous innovation, the cut and paste command, was reportedly based on the old method of editing in which people would physically cut portions of printed text and glue them elsewhere.
The command was incorporated in Apple's software on the Lisa computer in 1983, and the original Macintosh that was released the following year.
One of Mr Tesler's firmest beliefs was that computer systems should stop using "modes", which were common in software design at the time.
"Modes" allow users to switch between functions on software and apps but make computers both time-consuming and complicated.
So strong was this belief that Mr Tesler's website was called "nomodes.com", his Twitter handle was "@nomodes", and even his car's license plate was "No Modes".
Silicon Valley's Computer History Museum said Mr Tesler "combined computer science training with a counterculture vision that computers should be for everyone".
Researchers at the University of California, Los Angeles (UCLA) have found that a person's ability to feel empathy can be assessed by studying their brain activity while they are resting rather than engaged in specific tasks, according to a release on Tuesday.
Traditionally, empathy is assessed through the use of questionnaires and psychological assessments. The new findings offer an alternative to people who may have difficulty in filling out questionnaires or expressing their feelings, such as people with severe mental illness or autism, said Marco Iacoboni, senior author of the study and professor of psychiatry and biobehavioral sciences at UCLA.
For the study, published in Frontiers in Integrative Neuroscience, researchers recruited 58 male and female participants aged 18-35.
They were told to let their minds wander while keeping their eyes still by looking at a fixation cross on a black screen. Afterward, the participants completed questionnaires designed to measure empathy.
Using a form of artificial intelligence, also known as machine learning, to collect the resting brain activity data of the participants, the researchers can pick up subtle patterns in data, which more traditional data analyses can not do.
In the study, the researchers also applied a noninvasive technique called functional magnetic resonance imaging, which measures and maps brain activity through small changes in blood flow, to assess the participants' empathy ability.
"We found that even when not engaged directly in a task that involves empathy, brain activity within these networks can reveal people's empathic disposition," Iacoboni said.
"Empathy is a cornerstone of mental health and well-being. It promotes social and cooperative behavior through our concern for others. It also helps us to infer and predict the internal feelings, behavior and intentions of others," Iacoboni said.
The maiden flight of the Long March-5B rocket carrying a trial version of China's new-generation manned spaceship is expected to take place in April, indicating the imminent start of construction of China' space station.
The rocket, the prototype core capsule of the space station and the experimental manned spaceship are undergoing tests at the Wenchang Space Launch Center on the coast of south China's island province of Hainan.
During the flight in mid to late April, the experimental manned spaceship will be sent into space with no crew. The prototype of the core capsule of the space station will not be launched.
The Long March-5B is a modified version of the Long March-5, currently China's largest carrier rocket, and will be mainly used for sending capsules of China's space station and large spacecraft to the low-Earth orbit, according to the China Manned Space Agency (CMSA).
Space engineers developed a new large fairing, which is 20.5 meters long and 5.2 meters in diameter, for the Long March-5B. The whole rocket is about 53.7 meters long, with a 5-meter diameter core stage and four 3.35-meter diameter boosters.
The rocket uses environment-friendly fuel, including kerosene, liquid hydrogen and liquid oxygen. It has a takeoff weight of about 849 tonnes and a payload capacity of 22 tonnes to low-Earth orbit, said Wang Jue, chief director of the Long March-5 development team at the China Academy of Launch Vehicle Technology under the China Aerospace Science and Technology Corporation.
After the maiden flight of the Long March-5B, the Long March-5 carrier rocket will launch China's first Mars probe and the Chang'e-5 lunar probe later this year.
China aims to complete construction of the space station around 2022. According to the CMSA, more than 10 missions are planned in the next three years to complete the construction and master technologies for in-orbit assembly and construction of large complex spacecraft, long-term manned spaceflight in near-Earth space and large-scale space science experiments.
China still faces many challenges, so joint drills at the space launch center and the maiden flight of the Long March-5B are very important, said experts.
The space station will be a T shape with the Tianhe core module at the center and a lab capsule on each side. The core module -- at 16.6 meters long and 4.2 meters in diameter, with a takeoff weight of 22.5 tonnes -- will be the management and control center.
China's current largest spacecraft, the Tianhe core module will be able to support a long-term stay of three astronauts in space.
The living space in the core module is about 50 cubic meters. With the two lab capsules, the living space could be up to 110 cubic meters, which would provide the astronauts a confortable environment, said experts from the China Academy of Space Technology (CAST), the main developer of the space station capsules.
The longest stay in space so far by Chinese astronauts is 33 days. The necessary water and oxygen were taken into space. To enable astronauts to stay longer in orbit, the space station will be equipped with a renewable life support system, said experts.
The water vapor exhaled by astronauts will be recovered by condensation, and urine will be recycled and purified as drinking water and domestic water. The hydrogen produced in electrolytic oxygen production and the carbon dioxide exhaled by astronauts can generate oxygen through chemical reaction, which can supplement oxygen for the space station.
Science facilities on the space station could support hundreds of research projects in fields such as astronomy, space life science, biotechnology, microgravity, basic physics and space materials.
More than a dozen advanced experiment racks will be installed, and an extra-vehicular experiment platform will be built. In addition, a capsule holding a large optical telescope will fly in the same orbit. | 0.831452 | 3.080662 |
We often think of asteroids and comets as distinct types of small bodies, but astronomers have discovered an increasing number of “crossovers.” These objects initially appear to be asteroids, and later develop activity, such as tails, that are typical of comets.
Now, the University of Hawai’i Asteroid Terrestrial-impact Last Alert System (ATLAS) has discovered the first known Jupiter Trojan asteroid to have sprouted a comet-like tail. ATLAS is a NASA-funded project using wide-field telescopes to rapidly scan the sky for asteroids that might pose an impact threat to Earth. But by searching most of the sky every two nights, ATLAS often finds other kinds of objects — objects that aren’t dangerous, but are very interesting.
Early in June 2019, ATLAS reported what seemed to be a faint asteroid near the orbit of Jupiter. The Minor Planet Center designated the new discovery as 2019 LD2. Inspection of ATLAS images taken on June 10 by collaborators Alan Fitzsimmons and David Young at Queen’s University Belfast revealed its probable cometary nature. Follow-up observations by UH astronomer J.D. Armstrong and his student Sidney Moss on June 11 and 13 using the Las Cumbres Observatory (LCO) global telescope network confirmed the cometary nature of this body. | 0.839345 | 3.408634 |
NASA's New Horizons spacecraft is being readied for a January liftoff to the outer reaches of the solar system. It will be humanity's first mission to Pluto and the Kuiper Belt--a vast and distant repository of the solar system's leftover building materials--and is expected to reap rich scientific rewards.
"The New Horizons mission to Pluto completes our initial survey of the nine planets we believed comprised the Solar System when we began the space age," said NASA Administrator Michael Griffin. "In that sense, this mission truly marks the end of the beginning, and all of us look forward to receiving those first pictures of Pluto and Charon when they finally arrive."
Those first pictures could arrive as early as 2015 assuming New Horizons launches on time. When the data does start flowing back from the ninth planet it promises to increase dramatically scientific understanding of the Pluto.
"Everything we know about Pluto could basically fit on a postcard," said Colleen Hartman, NASA's deputy associate administrator for science. "We are truly going to a new frontier."
The 5-billion kilometer journey is expected to take as little as nine and a half years provided New Horizons launches in time to take advantage of a gravity assist during a planned flyby of Jupiter that is designed to use the gravitational power of the solar system's largest planet to give the already speeding spacecraft an additional boost of speed.
New Horizons' window opens Jan. 11 and remains open until Feb. 14, but the spacecraft must launch no later than Feb. 2 to take advantage of the time saving Jupiter gravity assist. Otherwise, New Horizons will have to be launched on a direct trajectory that would delay its encounter with Pluto perhaps as much as three years.
If NASA misses the upcoming window entirely, it will have a second shot in February 2007. However, a launch during that two-week window would not put New Horizons in the vicinity of Pluto until perhaps as late as 2020.
Under either scenario, the New Horizons spacecraft, which is about the size of a grand piano, will be lifted into orbit atop a Lockheed Martin Atlas 5 rocket equipped with five solid-rocket boosters, a Centaur upper stage and a special STAR 48B solid propellant-fueled third stage that will propel the spacecraft out of low Earth orbit and toward its destination.
About a year after launch, assuming the spacecraft gets off in time for the gravity assist, New Horizons would encounter Jupiter, snapping pictures, making measurements and picking up speed as it slingshots past the gas giant on an eight-year cruise.
The New Horizons spacecraft was built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., which also is managing the mission for NASA. The total price tag for the New Horizons mission, including launch and more than 10 years of operations, has grown to $675 million. According to NASA, the cost growth is mostly due to additional work that had to be done preparing the spacecraft's compact nuclear power source and higher than expected launch costs. NASA spokesman Dwayne Brown said the launch alone is costing about $205 million.
A Long Wait
Scientists captivated by Pluto and the mysterious Kuiper Belt are no strangers to long waits. Since 1990, several missions to Pluto have been proposed only to be quickly abandoned for largely budgetary reasons. The most recent false start was Pluto Kuiper Belt Express, which NASA canceled in 2000 after its estimated price tag more than doubled. In 2001, under pressure from the U.S. Congress, NASA held an open competition to find a cheaper way to do a Pluto flyby and ultimately selected the $500 million New Horizons proposal but did not request any funding for the mission. Congress funded the New Horizons program as a budget earmark for two years before NASA finally got the message and started requesting money for the mission.
New Horizons' principal investigator, planetary scientist Alan Stern of the Boulder, Colo.-based Southwest Research Institute, has been waiting about as long as anybody to send a probe to Pluto. While Pluto has the distinction of being the only one of the solar system's nine long-discovered planets not to have been visited by a spacecraft, Stern said the reasons for going are science driven.
"I don't know anybody who thinks that checking it off the list is a good reason for going," he said. "We are going to Pluto to study the origins of the outer solar system, to better understand the formation of binary planets including the Earth-Moon system, and to explore for the first time this different kind of planet - not a terrestrial planet and not a gas giant, but an ice dwarf."
Ice dwarves like Pluto, Stern said, almost certainly outnumber the terrestrial planet and gas giants--at least in this solar system.
"It used to be said that Pluto is a misfit. But now we know Earth is the misfit," Stern said. "This is the most populous class of planet in our solar system and we have never sent a mission to this class."
Scientists believe that as Pluto continues its 248-yearlong orbit around the sun, its tenuous atmosphere eventually will freeze and collapse to the surface. Pluto has been racing away from the sun since its closest approach in 1989 and scientists do not know how much time remains before Pluto's atmosphere collapses. Once that happens its atmosphere is not expected to re-emerge for about 200 years.
"Some people think its 20 years off and some people think its five years off," said Stern. "No one really knows when Pluto's atmosphere will snow out and collapse."
As frigid Pluto grows even colder as it travels further from the sun, scientists believe that more and more of its surface will be cloaked in nitrogen-based snow, accelerating the freezing process that causes the atmosphere to collapse. Stern said the New Horizons team cannot be sure that there will still be an atmosphere to study until less than a year from encounter. That's because scientists suspect that once the process starts, it progresses fairly rapidly. "Some models say the collapse can be very sudden," Stern said. "It can happen in a matter of months."
The New Horizons spacecraft is about 2.5 meters across and weighs roughly 465 kilograms fully fueled. The spacecraft's onboard computers and suite of seven scientific instruments will be powered by a nuclear-fueled battery supplied by the U.S. Department of Energy. The single Radioisotope Thermal Generator (RTG) aboard New Horizons works by transforming heat from decaying Plutonium-238 into electrical power.
RTG's weaken over time, but New Horizons' RTG has enough Plutonium-238 on board to still be pumping out about 200 watts of power when the spacecraft encounters Pluto.
New Horizons' instruments include a high-resolution optical telescope; an ultraviolet spectrometer for measuring gas composition; a combination infrared spectrometer and color camera for mapping Pluto's surface; a radio experiment for measuring atmospheric composition and temperature; a plasma-sensing instrument for measuring properties in the solar wind at Pluto; and a student-built instrument that will record how much dust and debris hit the New Horizons spacecraft during its lengthy journey.
Richard Binzel, a Massachusetts Institute of Technology professor and member of the New Horizons science team, said the probe will produce the best images ever seen of Pluto. New Horizons' cameras are capable of recording raw images detailed enough to depict surface erosion and cratering, important clues to the tiny planet's past.
"We think the polar ice caps come and go seasonally," Binzel said. "But is it just a few millimeters or is it tens of meters of ice that comes and goes? The way we will see that is by seeing how much erosion is on the surface. Is it heavily cratered, indicating that the surface is very old or does the season process of ice movement erase the craters?"
In contrast, the best set of images available today were taken by the Hubble Space Telescope in the mid-1990s and had to be substantially enhanced just to show dark regions at Pluto's equator and brighter regions believed to be ice and snow at the poles.
New Horizons will begin making its observations of Pluto starting about four months out from its closest encounter. The busy part of the mission will last one day as the probe passes within 10,000 kilometers of Pluto and within 27,000 kilometers of its moon Charon. Stern said it is expected to take about nine months after closest encounter to transmit all the collected data back to Earth through the Deep Space Network.
After New Horizons completes its primary mission, assuming the spacecraft is still in good health, NASA expects to send the spacecraft off to take a closer look at one or two yet to be selected Kuiper Belt objects, perhaps another three to five years travel time from Pluto.
The first leg of the long journey begins at Cape Canaveral Air Force Station, Fla., where New Horizons and its Atlas 5 rocket are being prepared for launch.
The Atlas 5 was successfully fueled and tested during a so-called wet dress rehearsal Dec. 5. The rocket's fifth and final solid-rocket booster was strapped to the launcher about a week before. The spacecraft itself was filled with a full load of hydrazine fuel the day before the launch rehearsal and at press time was on track to be installed inside the Atlas 5's payload fairing Dec. 12.
A special Boeing-supplied STAR 48B solid-propellant-fueled third stage that will boost New Horizons spacecraft out of low-Earth orbit was delivered to the cape Dec. 1 as scheduled despite an ongoing Boeing machinist strike that has put three other U.S. government launches on hold.
Hartman said in a Dec. 8 interview she was confident that New Horizons' third stage was being handled properly by the five replacement workers assigned to the Lockheed Martin-provided launch. | 0.852377 | 3.342172 |
Imagine there are high-intensity radio signals speeding through the universe at incredible speeds, over incredible distances. The signals only last a few milliseconds — making them extremely difficult to detect, let alone study and analyze. It’s unclear what produces them, from where they originate, and exactly what they say. Maybe supernovas or star-forming nebulae cause them or maybe it’s aliens (because it’s always maybe aliens). Maybe we’re just picking up strange signals from our own satellites.
These signals, called fast radio bursts (FRBs), might hold the key to understanding the origins of the universe. Or they could very well be bupkis strewn about on an astronomical scale.
FRBs have been a never-ending mystery for astronomers since the first one — the Lorimer Burst — was discovered in archived data in 2001. We’ve only documented 16 of them so far.
Well, make that 17 now.
An international team of astronomers discovered a new FRB. Better yet, it’s the first recurring FRB signal ever observed. This incredible new discovery could help crack the mystery behind FRBs to better understand the universe.
Or it could just add to the mystery and fuck things up even further.
Before this latest discovery (published in Nature), scientists assumed FRBs were one-off events — strange but singular phenomena originating from independent incidents. To find an FRB that’s on repeat, however, is unprecedented.
The new signal, called 121102, was picked up by researchers working with the Arecibo radio telescope in Puerto Rico (the world’s largest radio telescope). It’s the first time an FRB has been found by any instrument outside of the Parkes radio telescope in Australia.
That’s neat, but why exactly is this new study important? A pulsing signal like 121102 narrows the possible origins of FRBs down to only a certain kind of energy-based events — ones that don’t result in the destruction of whatever is causing the FRBs.
Still, the recurring FRBs weren’t coming in on regular intervals — they were clustered in bursts. And they also were observed across a wide range of different spectra. That limits the possible origins of FRBs. The strange nature of 121102, however, suggests FRBs are much more dynamic than we’ve previously thought.
One possible solution to this particular mystery is that 121102 could be caused by a magnetar: a type of exotic neutron star characterized by insane magnetic fields. A rapid reconfiguration of the magnetic field — a “starquake” — could produce FRBs in such a way that fires them off in multiples.
But scientists need to figure out the signal’s original location to prove this theory. Astronomers working on a different FRB did exactly that at the end of February, pinpointing the galaxy from which it was emitted. Maybe it was from a magnetar, or a different event, but at least we know the general location to start digging.
That study also illustrated bigger implications of FRBs: How scientists could use them to sort out the distribution of matter in the universe, a cosmological question that strikes at the heart of astrophysics research.
Whether the mystery of FRBs gets clearer or murkier, you can definitely expect to hear more about them soon. | 0.829794 | 4.046497 |
What Does a Marsquake Look Like?
Southern California got all shook up after a set of recent quakes. But Earth isn’t the only place that experiences quakes: Both the Moon and Mars have them as well. NASA sent the first seismometer to the Moon 50 years ago, during the Apollo 11 mission; the agency’s InSight lander brought the first seismometer to Mars in late 2018, and it’s called the Seismic Experiment for Interior Structure (SEIS).
Provided by the French space agency, Centre National d’Études Spatiales (CNES), the seismometer detected its first marsquake on April 6, 2019. The InSight mission’s Marsquake Service, which monitors the data from SEIS, is led by Swiss research university ETH Zurich.
Quakes look and feel different depending on the material their seismic waves pass through. In a new video, scientists at ETH demonstrate this by using data from the Apollo-era seismometers on the Moon, two of the first quakes detected on Mars by SEIS and quakes recorded here on Earth.
By running data from these worlds through a quake simulator, or “shake room,” scientists can experience for themselves how different the earthquakes can be. Researchers had to amplify the marsquake signals by a factor of 10 million in order to make the quiet and distant tremors perceptible in comparison to the similarly amplified moonquakes and unamplified earthquakes.
JPL manages InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight spacecraft, including its cruise stage and lander, and supports spacecraft operations for the mission.
A number of European partners, including France’s Centre National d’Études Spatiales (CNES) and the German Aerospace Center (DLR), are supporting the InSight mission. CNES provided the Seismic Experiment for Interior Structure (SEIS) instrument to NASA, with the principal investigator at IPGP (Institut de Physique du Globe de Paris). Significant contributions for SEIS came from IPGP; the Max Planck Institute for Solar System Research (MPS) in Germany; the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland; Imperial College London and Oxford University in the United Kingdom; and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología (CAB) supplied the temperature and wind sensors.
Jet Propulsion Laboratory, Pasadena, Calif.
NASA Headquarters, Washington | 0.811185 | 3.523145 |
“Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening as it’s a very difficult observation,” comments team leader Roberto Maiolino from the University of Cambridge. “Our results are exciting because they show unambiguously that stars are being created inside these outflows.”
The group set out to study stars in the outflow directly, as well as the gas that surrounds them. By using two of the world-leading VLT spectroscopic instruments, MUSE and X-shooter, they could carry out a very detailed study of the properties of the emitted light to determine its source.
Uploaded on Mar 23, 2017: (ESO) New observations from ESO’s Very Large Telescope have revealed stars forming in the huge outflows in galaxies, which are driven by central supermassive black holes. This ESOcast Light takes a quick look at the important facts. More information and download options: http://www.eso.org/public/videos/eso1… Credit: ESO. Editing: Herbert Zodet. Web and technical support: Mathias André and Raquel Yumi Shida. Written by: Thomas Barratt, Lauren Fuge, Oana Sandu & Richard Hook. Music: STAN DART (www.stan-dart.com). Footage and photos: ESO, ESA/Hubble, M. Kornmesser and C. Malin (christophmalin.com). Directed by: Herbert Zodet. Executive producer: Lars Lindberg Christensen.
Radiation from young stars is known to cause nearby gas clouds to glow in a particular way. The extreme sensitivity of X-shooter allowed the team to rule out other possible causes of this illumination, including gas shocks or the active nucleus of the galaxy.
The group then made an unmistakable direct detection of an infant stellar population in the outflow . These stars are thought to be less than a few tens of millions of years old, and preliminary analysis suggests that they are hotter and brighter than stars formed in less extreme environments such as the galactic disc.
As further evidence, the astronomers also determined the motion and velocity of these stars. The light from most of the region’s stars indicates that they are travelling at very large velocities away from the galaxy centre — as would make sense for objects caught in a stream of fast-moving material.
Co-author Helen Russell (Institute of Astronomy, Cambridge, UK) expands: “The stars that form in the wind close to the galaxy centre might slow down and even start heading back inwards, but the stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether.”
The discovery provides new and exciting information that could better our understanding of some astrophysics, including how certain galaxies obtain their shapes ; how intergalactic space becomes enriched with heavy elements; and even from where unexplained cosmic infrared background radiation may arise .
Maiolino is excited for the future: “If star formation is really occurring in most galactic outflows, as some theories predict, then this would provide a completely new scenario for our understanding of galaxy evolution.”
Stars are forming in the outflows at a very rapid rate; the astronomers say that stars totalling around 30 times the mass of the Sun are being created every year. This accounts for over a quarter of the total star formation in the entire merging galaxy system.
The expulsion of gas through galactic outflows leads to a gas-poor environment within the galaxy, which could be why some galaxies cease forming new stars as they age. Although these outflows are most likely to be driven by massive central black holes, it is also possible that the winds are powered by supernovae in a starburst nucleus undergoing vigorous star formation.
This was achieved through the detection of signatures characteristic of young stellar populations and with a velocity pattern consistent with that expected from stars formed at high velocity in the outflow.
Spiral galaxies have an obvious disc structure, with a distended bulge of stars in the centre and surrounded by a diffuse cloud of stars called a halo. Elliptical galaxies are composed mostly of these spheroidal components. Outflow stars that are ejected from the main disc could give rise to these galactic features.
How the space between galaxies — the intergalactic medium — becomes enriched with heavy elements is still an open issue, but outflow stars could provide an answer. If they are jettisoned out of the galaxy and then explode as supernovae, the heavy elements they contain could be released into this medium.
Cosmic-infrared background radiation, similar to the more famous cosmic microwave background, is a faint glow in the infrared part of the spectrum that appears to come from all directions in space. Its origin in the near-infrared bands, however, has never been satisfactorily ascertained. A population of outflow stars shot out into intergalactic space may contribute to this light.
This research was presented in a paper entitled “Star formation in a galactic outflow” by Maiolino et al., to appear in the journal Nature on 27 March 2017.
The team is composed of R. Maiolino (Cavendish Laboratory; Kavli Institute for Cosmology, University of Cambridge, UK), H.R. Russell (Institute of Astronomy, Cambridge, UK), A.C. Fabian (Institute of Astronomy, Cambridge, UK), S. Carniani (Cavendish Laboratory; Kavli Institute for Cosmology, University of Cambridge, UK), R. Gallagher (Cavendish Laboratory; Kavli Institute for Cosmology, University of Cambridge, UK), S. Cazzoli (Departamento de Astrofisica-Centro de Astrobiología, Madrid, Spain), S. Arribas (Departamento de Astrofisica-Centro de Astrobiología, Madrid, Spain), F. Belfiore ((Cavendish Laboratory; Kavli Institute for Cosmology, University of Cambridge, UK), E. Bellocchi (Departamento de Astrofisica-Centro de Astrobiología, Madrid, Spain), L. Colina (Departamento de Astrofisica-Centro de Astrobiología, Madrid, Spain), G. Cresci (Osservatorio Astrofisico di Arcetri, Firenze, Italy), W. Ishibashi (Universität Zürich, Zürich, Switzerland), A. Marconi (Osservatorio Astrofisico di Arcetri, Firenze, Italy), F. Mannucci (Osservatorio Astrofisico di Arcetri, Firenze, Italy), E. Oliva (Osservatorio Astrofisico di Arcetri, Firenze, Italy), and E. Sturm (Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”. | 0.914841 | 3.776111 |
Scientists Spy Never-Before-Seen Halo of Cool Gas Circling the Milky Way’s Supermassive Black Hole Sagittarius A*
Well, that was unexpected.
Nobody had any idea that there is a halo of cool gas circling the black hole at the center of our galaxy until a team of researchers at the ALMA observatory in Chile's Atacama desert took a closer look. Their paper was published yesterday in Nature, the world's leading science journal.
Sagittarius A* is the supermassive black hole that sits some 26,000 light-years away in the center of our Milky Way galaxy with a mass approximately 4 million times that of our Sun. It is surrounded by something called an accretion disc, which is a wide, flat band of cosmic detritus that has not been swallowed into the gravitational abyss beyond the event horizon.
Within this accretion disc, there is a ring of blisteringly hot gas. How hot? 18 million Fahrenheit, according to Science Alert – which lights up on X-ray observations like Times Square at its worst – but it didn't seem to be moving. This is atypical, to say the least.
Scientists found a loophole: hydrogen. The radiation surrounding Sagittarius A* causes hydrogen atoms to constantly gain and lose electrons, which produces a very distinct signal that can reach Earth with hardly any deterioration. Scientists used the ALMA (Atacama Large Millimeter Array) to image the hydrogen wavelength which revealed that not only was the accretion disc moving but that there was also a previously unknown ring of much cooler gas surrounding the black hole. They were then able to map the rotation by analyzing its redshift and blueshift (more on those phenomena here and here).
Image Credit: ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello CC BY 3.0
Elena Murchikova, the lead author of the paper and an astrophysicist at the Institute for Advanced Study in Princeton, said in a statement:
"We were the first to image this elusive disk and study its rotation…This is important because this is our closest supermassive black hole. Even so, we still have no good understanding of how its accretion works. We hope these new ALMA observations will help the black hole give up some of its secrets."
Watch how scientists go about finding black holes here:
Cover Image Credit: NRAO/AUI/NSF; S. Dagnello CC BY 3.0 | 0.874361 | 3.718685 |
This image shows an oxygen trail created when a small comet was disrupted as it approached our planet on September 15, 1996. This image was taken by the Polar spacecraft's Earth Camera in ultraviolet wavelengths. The oxygen trail has been superposed upon a "Face of the Earth" map of our planet.
Courtesy of Dr. Louis A. Frank, The University of Iowa and NASA
In 1997, we released a piece called "Snowballs Entering the Earth's Atmosphere?"
We were recently alerted that those snowballs may have been identified! Here's the scoop!
These snowballs may really be small comets. If the hypothesis is correct, these snowballs are millions of times smaller than comets like Halley's or Linear, but they are mainly made of water like these larger comets. They lack dust and iron though and so they do not glow or produce a bright tail.
These small comets may have been crashing into the Earth for the last 4.5 billion years! If that's true, then some or all of the Earth's water probably did come from these small comets.
It's been estimated that one small comet hits the Earth every three seconds. But, don't worry about getting hit by one of these snowballs! Small comets are not a danger to humans on Earth. They get torn apart at about 800 miles above the Earth and are vaporized by the Sun by about 600 miles above the Earth.
This may sound like something out of a cartoon show, but the Polar spacecraft may have confirmed the existence of these small comets originally found by Louis A. Frank of the University of Iowa. The Polar spacecraft sees the small comets from really far away. So, the next step is to send a spacecraft to see the small comets up close! That will help us to know whether or not this snowball hypothesis is correct!
Some scientists do not believe that Dr. Frank is actually seeing small comets. They do not believe the small comets hypothesis is correct. They think there is evidence that whatever Dr. Frank has discovered, it cannot be comets. Scientists are still debating whether the small comets hypothesis is true or not.
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Scientists have been working for many years to try and figure out how the Earth first came to have water on it. Now there is a new theory -- the Small Comet theory. Dr. Louis Frank and Dr. John Sigwarth...more
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Six spacecraft flew by Halley's comet in 1986. There were two spacecraft launched from Japan, Suisei and Sakigake, and two from the Soviet Union, Vega 1 & 2. One spacecraft, ICE, from the United States...more
Comets are observed to go around the sun in a long period of time or a short period of time. Thus they are named "long-period" or "short-period" comets. One group of short-period comets, called the Jupiter...more
Scientists have learned a great deal from the crash of comet Shoemaker-Levy 9. Scientists traced the orbit of the comet backwards in time to guess its origin. The crash of a comet like Shoemaker-Levy 9...more
Mathematical theory suggests that comet Shoemaker-Levy 9 was likely a short-period comet which was captured into orbit around Jupiter in 1929 and began to execute the path plotted in this diagram. This...more
As the ices of the comet nucleus evaporate, they expand rapidly into a large cloud around the central part of the comet. This cloud, called the coma, is the atmosphere of the comet and can extend for millions...more | 0.83788 | 3.353916 |
A binary main-belt comet
Publication date: 22 September 2017
Authors: Agarwal. J., et al.
Copyright: © 2017 Macmillan Publishers Limited, part of Springer Nature
Asteroids are primitive Solar System bodies that evolve both collisionally and through disruptions arising from rapid rotation. These processes can lead to the formation of binary asteroids and to the release of dust, both directly and, in some cases, through uncovering frozen volatiles. In a subset of the asteroids called main-belt comets, the sublimation of excavated volatiles causes transient comet-like activity. Torques exerted by sublimation measurably influence the spin rates of active comets and might lead to the splitting of bilobate comet nuclei. The kilometre-sized main-belt asteroid 288P (300163) showed activity for several months around its perihelion 2011 (ref. 11), suspected to be sustained by the sublimation of water ice and supported by rapid rotation, while at least one component rotates slowly with a period of 16 hours (ref. 14). The object 288P is part of a young family of at least 11 asteroids that formed from a precursor about 10 kilometres in diameter during a shattering collision 7.5 million years ago. Here we report that 288P is a binary main-belt comet. It is different from the known asteroid binaries in its combination of wide separation, near-equal component size, high eccentricity and comet-like activity. The observations also provide strong support for sublimation as the driver of activity in 288P and show that sublimation torques may play an important part in binary orbit evolution.Link to publication | 0.833391 | 3.761778 |
Has the Sausage been turned on by an Electric Universe?
Is it a Birkeland current or some other form of space plasma filament or circuit?
Stars being formed or powered on in z pinches (zeta pinches)?
A so-called "cosmic tsunami" is rousing a galaxy cluster affectionately nicknamed "Sausage," suggesting that stagnant galaxies can be rejuvenated when galactic clusters collide, scientists say.
Astronomers made the discovery while studying CIZA J2242.8+5301, an ancient galaxy cluster 2.3 billion light-years from Earth. The cluster (yes, they actually call it Sausage), which is full of old red stars, is waking up as a shock wave triggers new star formation. The shock wave from the cluster's collision, which scientists compared to a tsunami, began 1 billion years ago and is moving at a mind-boggling speed: 5.6 million mph (9 million km/h).
"We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role," study co-leader Andra Stroe, an astronomer at Leiden Observatory, said in a statement. "The comatose galaxies in the Sausage cluster are coming back to life, with stars forming at a tremendous rate. When we first saw this in the data, we simply couldn't believe what it was telling us."
'Cosmic Tsunami' Shocks Comatose 'Sausage' Galaxy Cluster Into Star Formation | 0.855911 | 3.295668 |
After another near miss, Stanford professor wants to find asteroids that threaten Earth
Several large asteroids have zipped dangerously close to Earth in the past month.
Scott Hubbard is part of a team that plans to track down future threats.
Diagram depicts the passage of asteroid 2012 DA14 through the Earth-moon system on Feb. 15, 2013.
(Image credit: NASA/JPL-Caltech)
March 11, 2013
By Bjorn Carey
On Saturday, an asteroid the size of one and a half football fields flew within 240,000 miles of Earth. If the space rock had hit land, it would have leveled an area the size of San Francisco Bay. If it had hit the Pacific Ocean, the impact would have sent a tsunami to every facing shore.
But what is perhaps most alarming about this particular asteroid, called 2013 ET, is that, until March 3, no one had any idea it was headed toward Earth.
Scott Hubbard, a consulting professor of
aeronautics and astronautics at Stanford, thinks we can do something about that. Hubbard, a former director of NASA Ames
Research Center, is also the program architect for the
B612 Foundation, which aims to track down the hundreds of thousands of unknown asteroids that could pose a threat to Earth.
Many asteroids that come near Earth – such as 2013 ET, or 2012 DA14, the football stadium-size asteroid that passed inside the orbit of Earth's communication satellites in February – have unusually long orbits.
There are an estimated million of these near-Earth asteroids longer than 100 meters, or about 300 feet. But because they are relatively small and spend so much time far from Earth, scientists tend to find them only by chance.
"We know about 90 to 95 percent of the asteroids larger than a kilometer," Hubbard said. "But we know only maybe 1 percent of the asteroids in the 100 meter range."
This is worrisome, considering that an impact from a 100-meter asteroid would be equal to detonating a 100-megaton hydrogen bomb.
The first step toward protecting the planet from these asteroids, Hubbard said, is to detect them. To that end, B612 is in the process of raising
public funds to build an asteroid-hunting space telescope called
Near-Earth asteroids are particularly difficult to spot. In addition to being relatively small, they are comprised mostly of black carbon, so they blend in with the equally black background of space. The upside to being dark is that the rocks absorb a decent amount of heat, which will make them obvious to Sentinel's planned array of infrared detectors.
"Once we detect an asteroid and track it long enough to know what the orbit is, then we can just apply the laws of physics and know exactly where it will be 50 to 100 years from now," Hubbard said.
Using this method, Sentinel, which will cost around $450 million to build and launch, should discover nearly all the asteroids larger than 140 meters, and about half of those between 50 and 140 meters.
"The fundamental technology needed to achieve this exists, we just need to demonstrate that the detectors are sensitive enough and scale up to what we need," he said. "We're drawing on the heritage from two previous space telescopes, Kepler, which was used to detect exoplanets, and Spitzer, an infrared telescope. So far it all looks very doable, but we need a prototype to confirm the design."
Should Sentinel find an asteroid on a crash course with Earth, the Hayabusa and Deep Impact spacecraft (asteroid and comet impactors, respectively) would provide a basic strategy for deflecting the rock: run something into it.
"We just need to alter its velocity by about the speed of an ant walking, and over the years its course will be changed enough so that it will miss Earth," Hubbard said. "You don't need a nuclear bomb to do that."
Another plan calls for a gravity tractor, a process that involves placing an object in the vicinity of the rock. The gravitational interaction between the asteroid and the object throws off the asteroid's velocity by a tiny amount that multiplies over time so that it misses Earth.
But neither of these solutions is possible unless we know an asteroid is bearing down on us a few years in advance, making efforts such as Sentinel all the more important. | 0.81373 | 3.230817 |
©Copyright 2018 GEOSCIENCE RESEARCH INSTITUTE
11060 Campus Street • Loma Linda, California 92350 • 909-558-4548
SOME RECENT DATA FROM VENUS AND JUPITER: IMPLICATIONS FOR COSMOGONY
George T. Javor
Associate Professor of Microbiology
Loma Linda University
WHAT THIS ARTICLE IS ABOUT
Views of unexplored areas, be they in science or geography, are constructed either from extrapolation of known experiences or from wild fantasy. Earthbound cosmologists have viewed our solar system from both perspectives. With the advent of unmanned probes, results have been obtained which have forced the abandoning of supposed similarities with our own earth as well as causing the destruction of several fantasies. The solar system appears not to be homogeneous in its composition and structure. These results are puzzling in view of a supposed similar source of raw materials. Atmospheric compositions are uniformly hostile to known life forms. Elemental and molecular studies indicate great variance in apparent ages. These results provide little confidence in any naturalistic model of a cosmology for our solar system.
A collection of planetary bodies clustered around a medium-sized star constitutes man's backyard in this vast universe. After millennia of wistful gazing with the naked eye and centuries of squinting through earth-bound telescopes, man in the last two decades has arrived at the grand moment when he can study neighboring worlds in unprecedented detail from comparatively close-up positions.
The era of unmanned planetary missions began in December 1962, when the spacecraft Mariner 2 flew by Venus and measured that planet's surface temperature and the strength of its magnetic field. This initial exploration was followed by more than three dozen missions of varied complexity to other parts of the solar system . As of early 1980, seven American planetary spacecraft were in operation: two Viking landers on the surface of Mars, two Voyagers cruising toward Saturn, the Pioneer 10 vehicle leaving the solar system and carrying a "cosmic greeting card," the Pioneer 11 craft traveling between the orbits of Saturn and Uranus, and a Pioneer-Venus satellite in orbit around Venus.
Most students of the solar system believe that it was formed four to five billion years ago out of a large rotating cloud of gas and small rocky particles named the "presolar nebula." After the sun condensed out, the planets formed at various distances from the sun. The composition of each planet was influenced by the concentration of matter in that portion of the nebula and by the timing of its aggregation. According to this hypothesis, the early-forming planets (i.e., Jupiter and Saturn) scooped up more matter than late-forming ones such as Earth and Mars .
Currently recognized components of our solar system consist of the sun, nine planets and their thirty-five satellites, numerous comets, thousands of asteroids, plus countless meteoroids. Ninety-seven percent of the solar system's mass is located in the sun, a seething caldron of largely ionized hydrogen.
Nearest to the sun revolve the four small "inner" or "terrestrial" planets, Mercury, Venus, Earth and Mars. All have high densities varying from 3.93-5.52 times that of water. Beyond the orbit of Mars is an asteroid belt 300 million km wide which separates the inner planets from the large, gaseous outer planets, Jupiter, Saturn, Uranus and Neptune. Pluto, the farthest known planet from the sun, is anomalous in that position because it resembles the inner planets in size and density. Some have suggested that Pluto is a runaway satellite of Neptune.
The two gas giants Jupiter and Saturn are surrounded by numerous orbiting moons of various sizes and makeup. Each planet mimics the larger solar system in its form, and indeed, some of Jupiter's moons are of planet size.
There is on the whole a prevailing optimism among scientists that increased knowledge of our solar system will clarify the theories of its origins. But there are still dissenting opinions. For example Carl Sagan writes: "Yet even preliminary reconnaissance of the entire solar system out to Pluto and the more detailed exploration of a few planets ... will not solve the fundamental problem of solar system origins. What we need is to discover other solar systems, perhaps at various stages of their evolution" . Prospects of discovering or exploring planetary systems outside the solar system are remote in the foreseeable future.
The reason for this pessimistic view is that the new data from various parts of space necessitated a modification of the theories of the solar system's origin. This article will discuss selected findings of the Pioneer-Venus missions and of the Voyager 1 and 2 missions to Jupiter which have caused this reexamination.
Recent Data from Venus
Venus is our nearest planetary neighbor in space, a mere one hundred and twenty-day journey from Earth by modern spaceships. It closely resembles Earth in size and density; hence, according to the "presolar nebula" theory, one would infer similarities in planetary makeup. Though it receives almost twice as much solar radiant energy as does Earth, it actually absorbs only about the same amount of solar energy, due to its highly reflective cloud cover .
Despite these similarities, observed conditions on Venus are singularly unique in the solar system. Its surface is uniformly hot, in the vicinity of 750 K. Its heavy atmosphere is composed largely of carbon dioxide, creating a surface atmospheric pressure of nearly 100 times that on Earth. Conditions on Venus are so inhospitable that none of the half a dozen Soviet spacecraft survived more than a few hours after making a soft landing on the planet.
Venus is continually veiled by an unbroken, pale-yellow cloud cover that appears to be featureless at visible wavelengths. In the ultraviolet region these clouds display a complex pattern of bright and dark swirls. Both the clouds and the planet rotate in the retrograde direction. The upper clouds rotate with a period of about four days, driven by 360 km/hr winds at the equator, while the planet itself moves at the much slower rate of one rotation in 243 Earth days. Venus' slow rotation is thought to be the reason why there is no detectable magnetic field around the planet.
In December 1978 the Venusian atmosphere was extensively analyzed by five Pioneer Venus probes during their short plunges on various trajectories through it. Using radar, the Pioneer "bus" orbiter has produced a complete topological map of Venus. Initial results of these experiments have been published recently .
The Pioneer Venus space probes discovered that the cloud cover enveloping Venus has three distinct layers, extending vertically from 48 to 70 km above its surface. The upper cloud region contains droplets of an 85% aqueous solution of sulfuric acid. There are liquid droplets and solids of various sizes with uncertain chemical composition in the middle and lower clouds. Below the clouds a thin haze of sulfur dioxide and sulfuric acid extends from 48 km to 32 km. There is no particulate matter in the lower 32 km of the Venusian atmosphere, but visible light is so sharply bent here that looking straight down at the planet from orbit, one could see nothing but an empty sky.
These probes also made extensive measurements on the chemical composition and isotopic distribution of the gaseous components of the Venusian atmosphere using ion and neutral mass spectrometers and gas chromatographs.
Interaction between components of the upper atmosphere and the solar wind produces numerous ionic species. Of the 11 ions detected, the most abundant above 200 km are O+ and some C+, N+, H+ and He+, whereas at the 150 km level the O2+ is the dominant species with minor amounts of NO+, CO+ and CO2+ .
As for neutral molecules and atoms, helium is the highest detectable substance, being found as far away as 700 km from the planet. Carbon dioxide appears at 450 km and becomes the dominant species below 200 km. The atmospheric composition at 150 km above the surface is seen in Table 1.
In addition to these, measurable quantities of sulfur dioxide were found at the 70 km level. The composition of the lower portion of the Venusian atmosphere (25-54 km above the surface) is seen in Table 2.
Currently available data analyses do not permit the unequivocal identification of molecular oxygen. Its presence in measurable quantities would be a surprise to scientists who assume that most planets are surrounded by a reducing atmosphere resulting from outgassing processes from the planet's interior. Photodissociation of water and the subsequent escape of hydrogen could conceivably give rise to oxygen on Venus, were it not for the low rate of hydrogen escape, 107/cm2 sec. This has prompted the conclusion that "if Venus ever possessed a large amount of water, it cannot have lost it by escape mechanisms known to be operating now" .
A major surprise was the finding of 2-300 times as much 20Ne and 36Ar in the lower atmosphere of Venus than on Earth . These particular isotopes of inert gases are not decay products of radioactive elements, and as such they are assumed to have been present since the formation of the planet. At the same time, the abundance of elements lighter than argon, such as 14N or 12C, are about the same in Venusian atmosphere as in our own. These data necessitated a departure from previous thinking, causing scientists to conclude that "primordial" noble gas abundances do not give adequate estimates of other volatiles in a planetary atmosphere .
On the basis of low levels of primordial noble gas concentrations in our atmosphere, evolutionary theorists suggested that the original atmosphere of Earth was lost, followed by outgassing of a secondary atmosphere from the interior of the planet. This widely accepted notion will have to be reevaluated in the light of the findings above. Earlier studies of the atmosphere of Mars by the Viking probes showed that both the 36Ar to 40Ar ratio and the total abundance of argon are significantly lower there than in Earth's atmosphere, even though the abundances of other gaseous components, such as nitrogen, are comparable. A straightforward application of the "solar nebula" hypothesis would have predicted similar argon concentrations for both planets, since they were supposed to have been condensed out of the same nebula at close proximity.
To account for the actual findings, theorists suggested that perhaps nitrogen was somehow more effectively bound in the interior of Mars than was argon during the formation of the planet. When argon outgassed, it was swept away by an energetic "early" solar wind. By the time the Martian nitrogen was released into the atmosphere, this energetic solar wind had subsided.
This same scenario should also apply to Venus, which, like Mars, possesses only a weak magnetic field, permitting in theory the close approach of the hypothetical, early energetic solar winds. The prediction was that the argon content of Venus would be similar to that of Mars. The actual results were totally unexpected. Compared to Mars, Venus showed an increase in primordial argon content. More recently a new concept has been proposed, postulating that perhaps the temperature of the solar nebula was fairly even during planet formation. This permits the existence of an increase in noble gas concentration toward its center . However, this proposal does not predict the uniform 12C and 14N abundances observed in the atmospheres of Venus, Earth and Mars. There is no known basis upon which we would expect a gradient of noble gases to exist in the absence of the same gradient among other gases.
Another perplexing problem is the extremely hot temperature near the surface of Venus. The obvious explanation that the heavy atmosphere of carbon dioxide, water vapor and sulfur dioxide prevent the loss of absorbed radiant solar energies, a "greenhouse" effect, does not appear sufficient to explain the 750 K surface temperatures. Additional sources of energy are needed. One intriguing proposal suggests that compounds with high bond energies would form high in the atmosphere under the influence of sunlight, then would drift downward and decompose near the surface, releasing their chemical energies. In this way, a portion of the sun's energy would reach the Venusian surface in a chemical form. This decomposition energy is one possible cause of the faint glow observed in the lower atmosphere .
The surface of Venus has been mapped by radar from the Pioneer Venus orbiter. A variety of surface features can be seen: volcanoes, plateaus, mountain ranges, craters and great valleys. The craters, however, are few in number and are very shallow perhaps due to a surface softened by heat. A chain of volcanic prominences running north-south for thousands of miles has been seen, some reaching 4 km above the surrounding terrain. The most prominent mountain on Venus is Maxwell, towering alone 12 km above the surrounding region.
Venus lacks the equivalent of Earth's great ocean basins which account for 70% of our planet's surface. As a result, tectonic forces that gave rise to the Venusian mountains are not yet understood. Horizontal movements of crustal plates which are thought to be responsible for plateaus and mountains on Earth also explain the appearance of the corresponding basins.
Recent Data from Jupiter
Beyond the orbit of Mars and the asteroid belt, 800 million km from the sun, is Jupiter. Three hundred times more massive than Earth, Jupiter contains about two-thirds of the planetary mass of the solar system. Its elemental composition is thought to resemble that of the sun, but its structure is neither that of a star nor that of an inner planet. It is one-and-one third times as dense as water, presumably composed mostly of gas and liquid with possibly a small solid core of comparatively dense material .
Jupiter is surrounded by zones of clouds of alternating light and dark appearance, all oriented parallel to its equator. Infrared measurements by two Pioneer spacecraft reveal that the dark belts are warmer than the light zones. Chemically, the upper atmosphere of Jupiter is made up of hydrogen, helium, ammonia, methane, water and hydrogen sulfide, all colorless substances. Nevertheless, highly colored organic and inorganic compounds and free radicals are believed to form in the upper atmosphere under the influence of the sun's ultraviolet radiation, giving rise to the colored bands that are observed.
In the southern hemisphere is the "Great Red Spot," a 30-40,000 km by 14,000 km reddish vortex, observed by earth-based telescopes to fade and reappear periodically over the past several centuries. It appears to be a gigantic cyclonic disturbance of the atmosphere, hovering over a postulated sea of liquid hydrogen.
Voyager measurements focused on the composition, structure and dynamics of Jupiter's atmosphere, on magnetic field properties, and on the comparative geologies of the Galilean satellites.
The Voyager craft found the dynamics of Jupiter's atmosphere very complex. What appeared from a distance to be a rather stable, multicolored, banded cloud system turned out to be, upon closer inspection, a dynamic system of fast-moving streams, vortices and turbulence undergoing noticeable changes in rotational and lateral motion within hours. Besides the Great Red Spot, a host of light and dark colored spots were observed. Some spots were seen to overtake or roll around one another before separating. In view of such turbulence, it is surprising that the Great Red Spot has remained essentially intact for at least the three centuries it has been observed. This unexpected, complex motion invalidates all existing atmospheric circulation models for Jupiter.
Infrared spectroscopy of Jupiter's atmosphere revealed the presence of a wide variety of gases: hydrogen, methane, ethylene, ethane, deuterated methane, ammonia, phosphorus trihydride, water, and germanium tetrahydride. It also showed that the atmosphere above the Great Red Spot is measurably cooler when compared to the areas surrounding it .
Pictures taken on Jupiter's night side showed a vast glowing arc over the planet. Huge flashes of light were seen above the cloud tops, each estimated at 10 billion joules of electrical energy. They resemble the "superbolts," seen occasionally above Earth's tropical regions.
Another discovery was a thin flat equatorial ring of particles surrounding Jupiter. Some 30 km thick and 6000 km wide, this ring system appears to reach down to the cloud tops . It consists of particles about 10-100 meters across.
Jupiter's rotation period of just under 10 hours makes it the fastest rotating planet in the solar system, and it is therefore expected to have an intense magnetic field as observed. According to current theories, this magnetic field requires that the planet's interior be a rotating, electrically conductive fluid. Scientists postulate that underneath a 25,000 km deep surface layer of liquid molecular hydrogen, there exists yet another 25,000 km layer of hydrogen in an atomic, liquid, metallic state. This latter layer surrounds the core. This unusual metallic state of hydrogen is brought about by an estimated pressure of three million Earth atmospheres and a temperature near 11,000 K .
Jupiter has two distinguishable magnetic fields, an inner one which directs particles along a magnetic equator, and an outer field that fans far into space along the rotational equatorial plane of the planet. The inner magnetosphere extends to about 1,400,000 km while the outer field reaches to six and a half million km into space. Both magnetic fields are tilted 11º to the planet's axis of rotation. The strength of the magnetic field at Jupiter's cloud tops ranges from 2-15 G, compared to 0.5 G at Earth's surface. Jupiter's strong magnetic field accelerates electrons and protons to energies thousands of times higher than those observed in the Earth's magnetic belts. The radiation intensities are comparable to those following a nuclear explosion in our upper atmosphere .
Voyager 1 discovered that the inner magnetosphere forms a "flux tube" between Jupiter and one of its moons, Io. Charged particles of oxygen and sulfur flow along this "tube" at the rate of about 1010/cm2 sec, generating a current of about 5×106 A .
More than a dozen satellites orbit around Jupiter. The four largest rival the smaller planets in size and are often referred to as the "Galilean satellites." The Voyager missions examined extensively their surface structures. Some of the findings are given below in Table 3.
Io is the innermost Galilean satellite, featuring a mottled surface of orange, red, yellow and white, pock-marked with jet-black pits. It is surprising that no impact craters were found on Io, for most planetary bodies devoid of atmosphere are covered with these. Instead, eight active volcanoes were discovered spewing matter 70-300 km into space. The cause of volcanism is suspected to be a gravitational tug of war over Io between Jupiter on the one hand and Europa plus Ganymede on the other. As Io moves in a slightly eccentric orbit (caused by Europa and Ganymede), tidal bulges on its surface are "pumped" in and out by Jupiter, heating it to temperatures required for volcanism to occur.
Europa appears almost white, reflecting light nearly ten times better than Earth's moon. Its surface is criss-crossed by stripes and bands, tens of kilometers wide, and some extending thousands of kilometers in length. They appear to be filled fractures in the satellite's icy crust. This moon's surface is under a thick mantle of ice which effectively obscures most topographic features.
Ganymede and Callisto have numerous similar features. Both have large areas of dark and bright colors and both are pock-marked with numerous craters, although Callisto's surface has a greater number of these. One of Callisto's hemispheres is dominated by a system of concentric rings of grooves. Ganymede's surface is also covered with ridges and troughs that appear as grooves, except these run in random directions. The grooves on both moons are thought to be caused by tectonic forces .
Implications for Theories of the Solar System's Origin
The massive amount of new data reveals that the solar system is a much more complex, heterogeneous collection of planets, moons and interacting forces than previously suspected. Venus is a vastly different planetary body than the Earth and Mars. Jupiter and its four Galilean moons also form a complex and possibly unique subsystem.
It is not difficult to perceive that the "presolar or solar nebula" hypothesis neither predicts nor explains many of the recent findings. The very idea of planets condensing out of a cloud of gas and dust is not a secure one. Moreover, it is not at all obvious how planets of such widely diverse properties as Earth and Venus could have condensed out of the same rotating cloud at comparatively close distances to each other. The problem is further compounded when we note the variance in density and apparent composition of Europa and Ganymede, which are theorized to have formed, again at very close range, from the same primordial matter.
Since 1644, when Descartes published his vortex theory in Principia Philosophie, more than 20 major hypotheses have been advanced to explain the intricacies of the solar system. These are, according to one author, "a record of the versatility of the human mind" . Another writer summed it up this way:
Each new fact seemed to add to the complexity of the problem. It is clear that the solar system did not originate in a simple manner, in spite of the fact that many of the theories which have attempted to explain it are framed in simple terms. If a theory of the origin of the solar system is to be truly complete, it must explain all the facts. This is still extremely difficult, not only because all the known facts amount to such a large and bewildering sum of data, but because many vital facts are not yet known .
Thus we note the frustration of the theorists who attempt to formulate coherent theories of origins in terms of purely natural forces and without invoking the handiwork of a Creator. Yet they press on, convinced that eventually all the data will fall into place.
Creationists observe the orderly orbits of the planets around the sun, the strange admixture of similarities and diversities among the components of the solar system and find harmony between these and their concept of the Creator described in the Bible. Although they too are unaware of the undiscovered aspects of the solar system, given the choice between uniformity and non-uniformity, they would tend to predict that Saturn, Uranus and Neptune will turn out to be quite different from what was seen in the Jovian system. The Creator they know does not use the "assembly line" approach to creation, but rather He is an artist who does variations on a theme.
Carl Sagan. 1975. The solar system. Scientific American 233(3):22-31.
F.W. Cousins. 1972. The solar system. J. Baker Ltd., London.
A.G.W. Cameron. 1975. The origin and evolution of the solar system. Scientific American 233(3):32-41.
Reported in Science 203:743-808 (February 23, 1979).
Carl Sagan. 1975. The solar system. Scientific American 233(3):30.
A. Young and L. Young. 1975. Venus. Scientific American 233(3):70-78.
Reported in Science 205:41-121 (July 6, 1979).
H.A. Taylor, Jr., Henry C. Brinton, Siegfried J. Bauer, Richard E. Hartle, Thomas M. Donahue, Paul A. Cloutier, F. Curtis Michel, Robert E. Daniell, Jr., and Bruce H. Blackwel. 1979. Ionosphere of Venus: first observations of the dayside ion composition near dawn and dusk. Science 203:752-754.
H.B. Niemann, R.E. Hartle, W.T. Kasprzak, N.W. Spencer, D.M. Hunten, and G.R. Carignan. 1979. Venus upper atmosphere neutral composition: preliminary results from the Pioneer Venus orbiter. Science 203:770-772.
V.I. Oyama, G.C. Carle, and F. Woeller. 1980. Corrections in the Pioneer Venus sounder probe gas chromatographic analysis of the lower Venus atmosphere. Science 208:399-401.
A.I. Stewart, D.E. Anderson, Jr., L.W. Esposito, and C.A. Barth. 1979. Ultraviolet spectroscopy of Venus: initial results from the Pioneer Venus orbiter. Science 203:777-779.
J.H. Hoffman, R.R. Hodges, Jr., M.S. McElroy, T.M. Donahue, and M. Kolpin. 1979. Venus lower atmospheric composition: preliminary results from Pioneer Venus. Science 203:800-802.
J.H. Hoffman, R.R. Hodges, Jr., M.B. McElroy, T.M. Donahue, and M. Kolpin. 1979. Composition and structure of the Venus atmosphere: results from Pioneer Venus. Science 205:49-52.
The argon content of the upper atmosphere (100 km and up) is considerably lower, as shown by K. Mauersberger, et al. (1979) in Geophysical Research Letters 6:671, where they reevaluate their earlier report, published in Science 203:768 (1979). What appeared at first as signals of 36Ar and 40Ar in the neutral mass spectrometer aboard the Pioneer Venus multiprobe bus turned out, in fact, to be primarily due to other background gases and ions scattered inside the analyzer. Their conclusions, however, do not affect other data on the lower atmospheric composition, gathered by different instruments.
J.B. Pollack and D.C. Black. 1979. Implications of the gas compositional measurements of Pioneer Venus for the origin of planetary atmospheres. Science 204:56-59.
R.A. Kerr. 1980. Venus: not simple or familiar, but interesting. Science 207:289-293.
J.H. Wolfe. 1975. Jupiter. Scientific American 233(3):118-126.
B.A. Smith, L.A. Soderblom, T.V. Johnson, A.P. Ingersoll, S.A. Collins, E.M. Shoemaker, G.E. Hunt, H. Masursky, M.H. Carr, M.E. Davies, Allan F. Cook II, J. Boyce, G.E. Danielson, T. Owen, C. Sagan, R.F. Beebe, J. Veverka, R.G. Strom, J.F. McCauley, D. Morrison, G.A. Briggs, and V.E. Suomi. 1979. The Jupiter system through the eyes of Voyager 1. Science 204:951-971.
A.L. Broadfoot, M.J.S. Belton, P.Z. Takacs, B.R. Sandel, D.E. Shemansky, J.B. Holberg, J.M. Ajello, S.K. Atreya, T.M. Donahue, H.W. Moos, J.L. Bertaux, J.E. Blamont, D.F. Strobel, J.C. McConnell, A. Dalgarno, R. Goody, and M.B. McElroy. 1979. Extreme ultraviolet observations from Voyager 1. Encounter with Jupiter. Science 204:979-982.
The technical achievements in telecommunications during the Voyager experiments were staggering. In order to receive clear signals as weak as 4×10-21 watts from 700 million km in space, steerable, 2.7 million kg antennas of 64 meters diameter were used by Deep Space tracking stations. The sensitivity of these receiving systems is 85 million times greater than a home T.V. set. Information was transmitted at the incredible rate of 230,400 symbols per second. Voyager 1 transmitted 4×1011 symbols during its Jupiter mission, including 18,770 pictures. During this same mission 112,151 words were loaded into the on-board computer. The position of the spacecraft was known at all times within a standard deviation of 10 meters and its velocity was known within a standard deviation of 0.5 mm/sec. See R.E. Edelson, B.D. Madsen, E.K. Davis, and G.W. Garrison. 1979. Voyager telecommunications: the broadcast from Jupiter. Science 204:913-921.
R.O. Fimmel, W. Swindell, and E. Burgess. 1974. Pioneer odyssey, encounter with a giant. National Aeronautics and Space Administration SP 349.
L.A. Soderblom. 1980. The Galilean moons of Jupiter. Scientific American 242(1):88-100.
P.W. Hodge. 1979. Concepts of contemporary astronomy. 2nd ed. McGraw-Hill, New York, pp. 11-12. | 0.896228 | 3.644147 |
December 26, 2019 – When astronomers look around the solar system, they find that planets can be made out of almost anything. Terrestrial planets like Earth, Mars, and Venus have dense iron cores and rocky mantles. The massive outer planets like Jupiter and Saturn are mostly gaseous and liquid. Astronomers can’t peel back their cloud layers to look inside, but their composition is deduced by comparing the planet’s mass (as calculated from its orbital motion) to its size. The result is that Jupiter has the density of water, and Saturn has an even lower density (it could float in a huge bathtub). These gas giants are just 1/5th the density of rocky Earth.
Now astronomers have uncovered a completely new class of planet unlike anything found in our solar system. Rather than a “terrestrial” or “gas giant” they might better be called “cotton candy” planets because their density is so low. These planets are so bloated they are nearly the size of Jupiter, but are just 1/100th of its mass. Three of them orbit the Sun-like star Kepler 51, located approximately 2,600 light-years away.
The puffed-up planets might represent a brief transitory phase in planet evolution, which would explain why we don’t see anything like them in the solar system. The planets may have formed much farther from their star and migrated inward. Now their low-density hydrogen/helium atmospheres are bleeding off into space. Eventually, much smaller planets might be left behind.
New data from NASA’s Hubble Space Telescope have provided the first clues to the chemistry of two of these super-puffy planets, which are located in the Kepler 51 system. This exoplanet system, which actually boasts three super-puffs orbiting a young Sun-like star, was discovered by NASA’s Kepler space telescope in 2012. However, it wasn’t until 2014 when the low densities of these planets were determined, to the surprise of many.
The recent Hubble observations allowed a team of astronomers to refine the mass and size estimates for these worlds — independently confirming their “puffy” nature. Though no more than several times the mass of Earth, their hydrogen/helium atmospheres are so bloated they are nearly the size of Jupiter. In other words, these planets might look as big and bulky as Jupiter, but are roughly a hundred times lighter in terms of mass.
How and why their atmospheres balloon outwards remains unknown, but this feature makes super-puffs prime targets for atmospheric investigation. Using Hubble, the team went looking for evidence of components, notably water, in the atmospheres of the planets, called Kepler-51 b and 51 d. Hubble observed the planets when they passed in front of their star, aiming to observe the infrared color of their sunsets. Astronomers deduced the amount of light absorbed by the atmosphere in infrared light. This type of observation allows scientists to look for the telltale signs of the planets’ chemical constituents, such as water.
To the amazement of the Hubble team, they found the spectra of both planets not to have any telltale chemical signatures. They attribute this result to clouds of particles high in their atmospheres. “This was completely unexpected,” said Jessica Libby-Roberts of the University of Colorado, Boulder, “we had planned on observing large water absorption features, but they just weren’t there. We were clouded out!” However, unlike Earth’s water-clouds, the clouds on these planets may be composed of salt crystals or photochemical hazes, like those found on Saturn’s largest moon, Titan.
These clouds provide the team with insight into how Kepler-51 b and 51 d stack up against other low-mass, gas-rich planets outside of our solar system. When comparing the flat spectra of the super-puffs against the spectra of other planets, the team was able to support the hypothesis that cloud/haze formation is linked to the temperature of a planet — the cooler a planet is, the cloudier it becomes.
The team also explored the possibility that these planets weren’t actually super-puffs at all. The gravitational pull among the planets creates slight changes to their orbital periods, and from these timing effects planetary masses can be derived. By combining the variations in the timing of when a planet passes in front of its star (an event called a transit) with those transits observed by the Kepler space telescope, the team better constrained the planetary masses and dynamics of the system. Their results agreed with previous measured ones for Kepler-51 b. However, they found that Kepler-51 d was slightly less massive (or the planet was even more puffy) than previously thought.
In the end, the team concluded that the low densities of these planets are in part a consequence of the young age of the system, a mere 500 million years old, compared to our 4.6-billion-year-old Sun. Models suggest these planets formed outside of the star’s “snow line,” the region of possible orbits where icy materials can survive. The planets then migrated inward, like a string of railroad cars.
Now, with the planets much closer to the star, their low-density atmospheres should evaporate into space over the next few billion years. Using planetary evolution models, the team was able to show that Kepler-51 b, the planet closest to the star, will one day (in a billion years) look like a smaller and hotter version of Neptune, a type of planet that is fairly common throughout the Milky Way. However, it appears that Kepler-51 d, which is farther from the star, will continue to be a low-density oddball planet, though it will both shrink and lose some small amount of atmosphere. “This system offers a unique laboratory for testing theories of early planet evolution,” said Zach Berta-Thompson of the University of Colorado, Boulder.
The good news is that all is not lost for determining the atmospheric composition of these two planets. NASA’s upcoming James Webb Space Telescope, with its sensitivity to longer infrared wavelengths of light, may be able to peer through the cloud layers. Future observations with this telescope could provide insight as to what these cotton candy planets are actually made of. Until then, these planets remain a sweet mystery.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. | 0.873708 | 3.931711 |
A full list is found at http://www.phy6.org/StarFAQsA.htm
and links arranged by subject are at http://www.phy6.org/stargaze/StarFSubj.htm.
396B Posssibility of Asteroid Hitting Earth (2)
396B Posssibility of Asteroid Hitting Earth (2)
305. About mountainsDear Dr. Stern,
I would be very grateful if you answer my following questions in details?
ReplyWhat strange questions! your first question--I would say "no," except that I really do not know what you mean. Stabilize against what?
Some things should be understood. Compared to the size of the Earth, mountains are not at all high. They provide less surface variation than the markings on a coin. What they do is provide evidence for forces inside the Earth which deform its surface--throw up volcano peaks, crumple sections of surface which are pressed or stretched sideways (just look at a relief map of Nevada, with its north-south ridges) or raise parts of continental plates as one plate pushes beneath another.
This last process is responsible for some high mountains--for the Himalayas, raised by the plate of India (which I have read started as an island south of the equator and migrated north) pushing beneath the Asian plate. In Alaska, Mt. Denali (or McKinley) is similarly produced as the Pacific plates pushes northwards beneath the American plate and lifts it. Both processes create earthquakes.
Mountains on Earth are just about as high as they can get: unless pushed up or held by pressure below, they would sag under their own weight and gradually flatten. Mars has a giant volcano, Olympus Mons, nearly 3 times higher than any mountain on Earth: but then again, Mars only has 0.39 times our surface gravity, and no oceans (measuring Earth mountains from the sea bottom shows greater height).
And how would Earth be without mountains? Depends. We have continents of lighter rock, which float on top of denser rock and poke out above the oceans. If that floating did not exist, Earth would be one big ocean and dry-land plants and animals would have no chance. How would Earth look without mountains? The icy satellites of Jupiter have all sorts of surface markings, e.g."ghost" craters from long-ago impacts. But unlike Moon craters, they are just markings on a flat surface ("palimpsests") because ice is weak and easily sags, even under low gravity.
306a. "Will the World end in 2012?"I came across your website while looking for answers to this question and wondered if you could help. Unfortunately a Google search on this subject brings up more coo-coo science from dooms-day authors than scientific facts. Fortunately I found your website and was able to locate your email address.
My eight year old daughter was told by a friend at school that, "the world was ending in 2012." Her friend cited something about reversal of the earths poles, increasing solar activity (solar max??), planetary alignment and the Mayan Calendar ending at 2012. I tend to put things like this in the Art Bell/George Noory category and move on, but this has really frightened my little girl so I'm seeking some guidance. More importantly, her question suggests that she has some interest in physics so I'd like to find a way to keep that spark alive while providing some reassurance.
Can you provide a simple way of explaining earth rotation, earth polarity and angular momentum that would help quell her fears while at the same time peaking her interest in physics? Also any information on the Mayan calendar would be helpful.
ReplyI hope your daughter learns a lesson from this--don't trust Google, which collects web pages by machine and cannot tell sane from crazy. And don't rely on rumors. Find out! Rumors and Google can provide hints where to look, but to make a judgment--of what makes sense and what does not--is one's own job.
Being 8 years old is a bit early for making such judgments, so I hope she has your help (and maybe her mother's and her teacher's) to sort out the facts. I myself am just a retired physicist, too far from you to be of much help.
Luckily, questions like hers have arisen before, and the more significant ones are answered on the web site. The key file is
which sorts the questions by subject. Your daughter's interests are particularly suited for section #7a ("Earth Rotation") and there to questions such as #26, #78, #165, #166 and #171 . Also section #7c ("Calendar and related items") and in particular the last two entries (#264 and #302) which relate directly to the Maya calendar and the year 2012 (as does one following immediately below here).
I hope your daughter (with your help) will be reassured and informed by what she reads. I also hope that she will become interested in science, and in particular astronomy! You can start her on the early sections of "Stargazers" and maybe begin with the paper sundial in section #2a there.
The reversal of the Earth's magnetic poles is a different subject altogether, discussed in "The Great Magnet, the Earth." It's not expected to happen soon, and while it has occurred in the past, you are not likely to notice it if it does, unless you are using a compass.
306b. Another question about the year 2012Hello, I've been doing a little bit of research on the December 21st 2012 theory lately, seeing as it is the only respectable end of the world theory out there. I believe I understand the principle behind it but I'm unsure about a few notes in it. It seems to state that we will be perfectly aligned with the Black Hole that is at the center of our universe, giving a 10 percent chance that our own poles will dramatically switch as the Earth slows down and starts to turn the other way. As I'm sure you already know of this theory, knowing your intelligence just from your other articles that I've read, I would like to ask you your own opinion on this theory, and would the change take effect on other planets as well, causing their poles to shift and sort of having a Galaxy wide end?
Nothing much will happen to the universe or Earth and planets in December 2012. It is the time when the Maya calendar, which is quite sophisticated and has long cycles, will end (I think) its 5th cycle and start its 6th. It's like your car's odometer going past 499,999 to 500,000.
The universe has no center, by the way. Our Milky Way galaxy has one, for sure, and a big black hole sits there (I have written about it) but I am not sure it has much influence on us. If its rotation axis were pointed at Earth, telescopes might see a lot of X-ray and radio noise from it, but we are too far for any large effect, also it probably rotates the way the galaxy does, and therefore we are looking at its equator. And Earth's rotation can't change significantly because of the conservation of its angular momentum..
For more, see top of this page and look under #264, #291b and #302, also (about the Earth's rotation) #165, #166 and #108.
307. Advice to graduating High School StudentI have just passed out my 11th exams (from the Gujarat state board in India) with maths, physics and chemistry as my main subjects, English as language and computer science as a side subject and I am thinking to take up aeronautics as my main subject (to be an aerospace engineer or designer) so which are good universities and which are good courses which you would suggest me to choose. I am a bit weak in chemistry.
Please give me some suggestions to improve it.
Your site have been really very helpful for my school studies and also in outer school examinations
ReplyI do not know enough about conditions in India to advise you. For instance: some very good universities exist in India, but they charge high tuition, have difficult entrance examinations, and much competition exists among those who wish to attend. Where you belong in this, I do not know.
One thing, perhaps. What will you be doing in the coming summer vacation? If you are interested in aviation, look for a technical job associated with it--perhaps at a local airport, at an airplane refitting or repair facility. If you can afford it, be prepared to work for minimal pay, or even no pay at all. That way you will be in contact with people in the profession. Choose carefully, and if you are lucky, you might find a good mentor.
One last note: whenever you write ANYTHING, make sure to re-read and edit your words more than once, to catch any mistakes in spelling (your message had a few) or in grammar. The way you write gives your correspondent the first impression about what sort of person you might be.
A similar letter, received earlier:I'm a 23 year-old girl. Work in astronomy and being an astronaut are an old dream dating back to my childhood. Since I was a little girl I wanted to be in space and when I became older dreamt of La Silla, and being an astronaut like Story Musgrave as my hero fascinated me. I was very young and I didn't know which major should I study in high school. I thought that aerospace engineering was the best choice for me and I intended to study this major. So I studied mathematics and physics in high school, although at that time we didn't have aerospace engineering for women in our country, but I was very serious in my choice. After finishing high school I participated in university entrance examination to fulfil my dreams but unfortunately it was very hard and I couldn't pass the exam for my selected major and I had to study industrial management, despite my other interest. Finally a year ago I finished my studying but it doesn't satisfy me. I studied a lot but I couldn't achieve my dreams because in my country there is a university entrance exam for entering the university which is very hard and unfair. I cannot forgive the government because of this carelessness and injustice.
Anyway, now I have the chance to follow my dreams. I want to study aerospace engineering or engineering physics but I have a concern and it is about my health. I afraid of passing the time and money and then reaping nothing. Now I have bachelor degree in industrial management and I work in a good company and I can follow my education in my major in Europe (I have admission from one of the best universities from Sweden) . I'm worried about this problem. I afraid to quit everything and follow my dreams but it doesn't have any result for me.
Now I have a question from you and I need your help and guidance. I'd like to know about the medical and physical examination for selecting the astronauts. I afraid that I lose everything because of these kinds of examinations. Could you tell me about this examinations? I know medical tests include audio and visual examinations, dental examination, electrocardiography, pulmonary function test, and analyses of feces, blood and urine but I do not know anything about the physical examination. Also I'd like to know whether or not the person has curvature in his/ her spine can be an astronaut or not. Please guide and help me. I'd appreciate if you kindly answer my questions and raise my ambiguities.
Please accept my thanks in advance and I'm looking forward to receiving your early reply.
ReplyYou may not like to read this--but in fact, you are asking a lot. In this world, many dreams end up being just dreams. As far as I recall, astronauts are selected from a very small group--either outstanding airplane pilots (usually military airplanes)--or people with outstanding professional records, usually in science. Many people have a dream like yours, but few are chosen. Also, almost all astronauts are US citizens, and those who are not, are chosen by their governments, in countries collaborating with NASA.
I should add that nowadays just a few space missions with astronauts are conducted each year, far fewer than what was once predicted.
I don't know what effect curvature of the spine has. May depend on how bad it is, how much it interferes with your normal life.
Aerospace engineering or engineering physics are more realistic goals, but take a lot of study and please remember, even there few jobs are exciting. I know a young man who dreamt of becoming a pilot (even though he studied computers), he studied flying, got his license and then found it was hard to get a good job. For a while he flew tourists to see the Grand Canyon and other small-plane missions (once even transporting convicts from one prison to another), but his company went bankrupt and now he is in Alaska, transporting passengers and cargo in small airplanes to distant native villages, or tourists who want to see some scenic areas. It is hard and uncertain work, and all but stops in the coldest part of the year.
In truth, the number of interesting jobs in aviation or space is small--much fewer than jobs for doctors, trained nurses, computer experts or school teachers. The same is true in astronomy--see "Advice to a would-be astronomer" on
I would not discourage you from asking around a university (and joining a flying club, maybe?), but you will need persistence, ability to work hard and luck. I hope you have them all.
308. Could a (heat resistant!) ship float on the Sun?Hello. I am Chris. I just stumbled upon your website when I was inquiring around the internet about the rotation of the earth. I found your website to be very interesting and informative. Thus, I would like to know your thoughts on this question.
This question may seem like an irrelevant and impossible excursion into science fiction, yet it is a question that has tickled my curiosity for quite some time. If we were to build a spaceship that could successfully reach the sun's surface, how would the ship behave on the sun's surface? Or, more simply, what would the consistency of the sun's surface be like? Would the ship fall right through the surface, or would it float on it like a rubber duck floating on water? Could it be something else? Although I heard that the sun is gaseous, wouldn't the immense gravity of the sun cause sufficient compaction of the gases to give it a more fluid consistency? I don't think anybody has a definite answer on the subject, yet I would like to know your thoughts on the matter. Thank you for your time.
Matter comes in 3 varieties--solid, liquid and gas (viewing here plasma as a special gas). Solid and liquid form well-defined surface boundaries, e.g. the ocean surface. Gas just dwindles away exponentially, e.g. in the Earth's atmosphere (discounting temperature variation) air density drops by half with every 5 km of altitude, approximately. So at 10 km it is down to 1/4 the sea-level density, 15 km to 1/8 of the density... I think you get the point (the process ends around 100 km, where molecular collisions become rare).
For mathematical reasons, physicists use the "scale height" H, the distance where pressure and density are reduced, not by a factor 2, but by a factor e=2.7128... , But the physics is the same. Light objects can definitely float in an atmosphere--consider helium balloons--but the altitude can vary, they do not rise to any outer surface, but find an altitude which matches their density.
Same with a balloon near the Sun--if it were not instantly evaporated by the heat. Gravity is about 30 times larger, but molecules are lighter (hydrogen) and a lot hotter, so H is larger. In
I estimate H=150 km. In http://web.njit.edu/~dgary/321/Lecture7.html the result is 270 km. Take your choice!
A balloon floating above Jupiter, Saturn etc. is subject to the same laws.
309. Reducing the fuel weight of the Space Shuttle?I have a question you probably could answer really easily. I know the escape velocity for the Shuttle is around 18,000 miles per hour. But the Shuttle is very heavy and the fuel tanks filled with propellant are very heavy too.
So if you had a craft that had some sort of electronic propulsion that did not require those tanks filled with heavy fuel, I gather the escape velocity might still be the same?
So if you had perhaps a craft with 2 or 3 different systems that were like 2 or 3 stage systems, the outlay of raw energy would be less but the required speed would still be the same. And basically, such a craft would be quite large enough–with using all the lightweight materials–to carry 6-20 astronauts (or a large family wanting to leave Earth for greener pastures).
ReplyYour scheme unfortunately will not work, Newton's laws of motion conspire against it. To understand how that happens, you will need read about them in "From Stargazers to Starships,"--sections 16, 17, various parts of 18, as well as 25.
The shuttle starts off with something like 2500 tons of fuel, NOT just because that fuel supplies it with the ENERGY needed for reaching escape velocity, but also, because it supplies it with the FORCE needed to accelerate it to that speed. By Newton's 3rd law, you cannot exert force without pushing against something. Forces come in pairs between two objects, if A pushes B, then B pushes A with equal and opposite force.
With the shuttle, "B" is the fast jet of burning gas: by pushing that jet backwards, the shuttle (or any rocket) is pushing itself forwards at the same time. It is like the recoil of a gun, which is another example of these laws in action.
Electric propulsion (sect. 33) is not very suitable here, it still would require something massive to be thrown backwards, and electric energy can't be stored as easily as chemical energy. As for "greener pastures"--no such thing exists, not for life like ours, depending on liquid water: Venus is too close to the Sun and hot enough to boil water, while Mars is to far from it, and water there would be frozen much of the time. Earth alone is in the "Goldilocks range" of distances: be grateful for its green pastures, forests and fields!
310. How do Rockets Land?I am not a young student, but a medical doctor. I have been teaching some stuff about space to my young daughter. However, I am unable to tell her how a rocket lands, reason being I myself don't exactly know.
Could you please enlighten me? How do rockets land? Do they land at all or do they all burn up? Why do we see pictures of astronauts jumping from parachutes?
Could you advise a good website which can satisfy my doubts?
ReplyA major problem of an airliner returning to Earth is how to get rid of its energy of motion--kinetic energy--while still getting enough "lift" from the motion of air across its wings. If your daughter ever sat by the window of a landing airliner, she would see all sorts of auxiliary extensions of the wing sliding into place at the back of the wing--increasing air resistance and slowing down the airplane, and at the same time creating extra "lift" to hold the airplane up. The lift is much less efficiently produced than in ordinary flight, but that is all right, this unusually slow flight lasts only a short time and then the airplane is rolling on the ground.
A satellite in low Earth orbit must move at 24 times the speed of sound (or faster), which means its kinetic energy, the energy of motion, is at least 24 x 24 = 576 times the energy of something moving at the speed of sound, which is already more than the speed of an airliner. Weight for weight, a satellite has about 20-50 times the energy of a rifle bullet, enough to melt it, even boil it away.
Getting rid of that energy safely is the main challenge in landing. The astronauts returning from the Moon (at even greater speed) could not save their spacecraft but had to abandon it, and return in a "capsule" designed to stand a lot of heating, and meanwhile creating a powerful shock wave ahead of it, containing very hot air whose glow dissipated the energy. Then in the thicker atmosphere, at low speed, they used a parachute, and splashed down into the ocean.
Like the Apollo Moon ship, many research rockets are abandoned when their job is done--it would be too hard to bring them back intact.
The space shuttle enters the upper atmosphere (which is very rarefied) sideways, with its bottom forward: the bottom has heat-resistant ceramic tiles, and creates a great shock wave (in the "Columbia" some tiles broke away and the heat destroyed the shuttle). By the time it reaches the denser atmosphere, it has slowed down to about half the speed of sound, and it can land like an airplane--still, much faster than a jetliner, requiring accurate computer control.
Burt Rutan's "Spaceship One" similarly used wings, first as brakes (turning them to create air resistance), then to land as an ordinary airplane. However, since it only reached about 3.5 times the speed of sound, this was not as great a challenge.
311. The Earth's Spin reduced by Global WarmingI have read an article on internet which says that due to continue warming of earth, the length of day is becoming greater. Although the change is very small but with the passage of time it may perhaps become appreciable. Reference: http://space.newscientist.com
My question is: does there exist a chances that a time will come when due to change, the rotation of earth will stop?
ReplyI could not find the item on the site you have mentioned, and the only thing I can guess about it is the following.
As you know, the water level in the oceans is rising. The main reason (at least now) is not melting of icecaps, but warming of the water, which like almost any substance expands when heated. Therefore, since most of the Earth surface is ocean, if the water rises by, say, half a meter, the effective radius of Earth might increase by something like 35 cm.
In a rotating object, expanding away from the rotation axis slows the rotation (think about a rapidly spinning ice skater, extending her/his arms out and almost stopping). Expansion of the Earth will therefore slow down the rotation. But only by a tiny amount, since 35 cm is maybe 1 part in 20 million of the radius of the Earth. It will never become appreciable.
312. Circumnavigation of the SunA question came up in my family and interests me. I am indeed a new stargazer who is very interested in the workings of our solar system, galaxy, and the universe itself. The question I would like answered is...
"Why can't humans circumnavigate the sun?"
ReplyNot only have humans done so, but you yourself have done so too. Every year the Earth carries you on such a trip!
There even exists a bumper sticker, something like "Living on Earth is expensive, but you get a free trip around the sun."
ResponseMy question had nothing to with being on planet earth. I meant it as traveling in a space ship. Like the ones they send out now.
Answer to the responseThere exists no good reason for such a trip. It is also a difficult thing to do: no one has yet supported a human in space for as long a year, the orbit must be chosen carefully to have a period of exactly one year (or else Earth won't be there on the return!), and there is not much a human can do in such an orbit that an instrument cannot do simpler and cheaper--observe not just light but ultra-violet, x-rays, energetic particles, magnetic field etc.
Such instruments have in fact orbited the sun aboard "Ulysses". The aim was not just orbit the sun, but do so above the poles of the sun, a region which cannot be observed from Earth. That is a difficult orbit to achieve: the spacecraft first approached Jupiter and used its gravity to rotate its orbital plane by nearly 90 degrees. It was primarily a European space mission, launched in 1990, it has accomplished interesting discoveries, and is still working. No human astronaut could so as much. More on Ulysses home pages, e.g. http://ulysses.esa.int/science-e/.
313. Are nuclear forces merely gravity at very close distance?Is it possible that when we are speaking of strong nuclear forces, we are actually speaking of a tiny gravity space for the nuclei?
Are there any pages on this? I don't even know what it might be called.
I am just a layperson, who cannot master the math in my quantum gravity book, but I think --what I can read is rather accurate.
It just "looks" like we may replace the phrase strong nuclear force with gravitational field (with quantum restriction (?)) as holding the particles in place. Would this also apply to the sub particles, --and might it be the sub particles which allow the escape of the alpha particle in the first place?
ReplyNuclear physics is not my field, so you might check what follows below with someone more familiar, and with a fresher education in physics-- I'm past 75!
The drawing in section Q8.htm uses a "gravity well" as an analogy to the energy well caused by the nuclear force. However, the two forces are far apart in strength: the nuclear force is much stronger than the electric force, while gravity is much, much weaker.
You might perhaps argue that nuclear particles could be so small, that distances between them are small enough for gravity to be quite strong. However, if the proton is small, its electric charge should be confined to the same tiny size, and then the electric repulsion between neighboring protons will always overcome their gravitational attraction.
Anyway, I suspect that protons cannot be that small, because quantum mechanics demands for them to be spread out over a certain wavelength. Also, when protons or nuclei collide, their "cross section" is of the order of a "barn" or a fraction thereof, suggesting a dimension of the order of one part in a thousand billion of a centimeter. It sounds tiny, but is still too large for strong gravity.
314. Changing the Earth's RotationI have a serious question
What is the energy required to either slow down of speed up the Earth's rotation by say, 1 msec? I have tried out the calculations but I think I am missing a parameter or two.
ReplyThe energy E of the rotation of Earth is (I believe) (I ω2)/2 (check the "Hyperphysics" web site) where I is the moment of inertia of Earth, and ω is the angular velocity (a Greek omega). The value of I can be found on
and is around 8 1037 kg/m2
The earth rotates in about 86000 seconds, so approximately
ω = 2π /86000 = 7.3 10–5 radian/sec
ω2 = 5.3 10–9
and the energy E is around
E = 2 1029 joule
Changing the period by 1 msec out of about 105 sec means a relative change around
dω/ω = 10–8
The energy change, found by differentiating the energy equation, is approximately dE = E 2dω/ω = 2 10–8 E = 4 1021 joule.
A million power stations of 100 megawatt each would produce about as much in a year. Of course, it is not enough to have the energy--the Earth must also grab hold of something outside it, to transfer the angular momentum. The Moon and Sun do slow down the rotation, by raising tides on the Earth. But they do so at their own slow pace, and discussing this process would take us too far off.
315. Why are planetary orbits eccentric?I was reading yours question/answer section wherein you clarified several doubts beautifully and interestingly.
Why would the orbit of any planet be elliptical? Any planet that orbits any star or other planet is being pulled by the gravity of the central object (star or planet). Shouldn't the orbit always be circle, as the force pulling the planet inside would want it to be?
Assume the planet encountered the star while moving somewhere in the space, and started orbiting it. Then due to its own initial motion, it has at first an elongated elliptical orbit. But that orbit would slowly become more circular as the speed of planet on the edge of ellipse would be reduced. If we go by the pendulum theory, as the planet is moving under the impact of gravity of the star, the distance it moves far from the star (the longer axis of the orbit) would eventually shorten and become equal to its shorter axis, resulting in a circular orbit.
In case of a planet orbiting another planet (like our moon), we may have to consider the motion of the center planet (the one being orbited) and that may reduce the speed with which the elliptical orbit becomes circle, but at the end the orbit should be circle.
I can't think of any other theory to convince myself with the truth that earth is still in an elliptical orbit, while orbiting an relatively stationary star.
If so, at some point of time, the Earth's orbit will become circle (considering for now that my ideas hold true). Then it's also interesting to think about what happens when there are not longer or shorter days on earth. All days measure exactly equal and there remains only one season through out the year.
Waiting to know the things I'm not aware of (not very good with Physics - didn't get a chance to study formally).
ReplyCopernicus thought orbits should be circles, because the circle had a perfect shape (or else, because he knew how to calculate with circles). But your question really relates to the way the solar system came to be. I don't have answers, but knowing some physics and astronomy (and having read a bit about the problem), I can guess a few things.
It is generally agreed that the solar system began as a cloud of dust and gas, pulled together by gravity (astronomers have observed such clouds). Planets were not encountered by chance, after they had already formed. At first the material of that cloud just moved (on the average) towards the center. A dust particle or gas molecule pulled towards such a center does have an orbit, but if it starts far away, this will be a very elongted oval. The width of that oval will depend on the distribution of the "sideways velocity" of dust particles (related to "angular momentum").
However, as particles and gas come closer to the center, they may collide and convert some of their energy to heat. Such energy loss slows them down, allowing gravity to clump them together. The clumps radiate heat into space and become very cold, so gas molecules and atoms hitting them are likely to freeze and stick (as may have happened in comets, whose motion remains very elliptical). Furthermore, if the cloud is not completely symmetric--extending further on one side than the other--more will circle in one direction than in the other (say more counterclockwise than clockwise, as seen from some distant star), causing the average of the cloud to rotate.
The loss of energy to collisions will prevent dust particles from returning to their starting region. It will also bring everything down to a rotating disk, explaining why all major planets are very nearly in the plane of the ecliptic. Any particle moving on a steeply inclined orbit will collide again and again with the disk, and its fragments tend to share the disk's motion.
You would think that in the end everything would move in circular orbits in a thin layer, like the particles with make up the rings of Saturn, which tolerate no ellipses. However, before that stage is reached, the clumping produces "planetesimals" and then larger "protoplanets." These will collide and stick together to form planets, before a smooth circular structure like the rings of Saturn is achieved.
Apparently the planets formed before all their orbital eccentricity (traceable to the elongated initial orbits) has completely disappeared, and so we have elliptical orbits. However, the eccentricity of planetary orbits is very small. I have seen a picture of the Earth's orbit superposed on a circle. The difference between the two is expressed by the varying thickness of the drawn line and is barely noticeable (however, the separation between the focus of the ellipse and the center of the circle is quite evident.
In any case, the major planets now orbit clear of each other, and the slight ellipticity of their orbits is quite stable. It might change with time due to the pull of other planets (e.g. Jupiter), but I know of no significant mechanism which would gradually make orbits more and more circular. The process which you propose resembles the gradual change of a satellite's orbit if its lower end (perigee) grazes the atmosphere, but there exists no significant "atmosphere" in interplanetary space able to do the same to the motion of a planet.
The length of days may perhaps change over the billions of years, because tides raised by the Sun take away rotation energy of the Earth. The final state would have one end of the Earth pointing sunwards, as is the case now with the Moon-Earth system. The process is very slow, however, and the Sun may run out of fuel, etc., before it happens. Seasons, in any case, are caused not by the daily rotation but by the inclination of the Earth's axis to the plane of the Earth's motion.
316. Forces on Comet-dwellersAssume a habitable comet in a highly eccentric orbit. If you were living on it, would you feel acceleration as it sped up close to the sun? My thoughts:
(i) No. the comet and you are just following curved spacetime. If there was a feeling of acceleration - would it not mean that the comet would break up? We don't feel acceleration as we orbit the sun (nor do astronauts in the space station orbiting the earth). Maybe we do feel it but we are so used to it that we can no longer notice it?
(ii) Yes. There is definitely acceleration - tangential as well as radial. If you have a large change in speed, how could you not feel it?
ReplyYou stand on the comet, somewhere far from the Sun, and let go of an apple. Ignoring now the feeble gravity of the comet itself, the apple would move in the same orbit and therefore just hang there. It will not "feel" any force impelling it to move to another location. And neither would you (if the icy chill, so far from the Sun, lets you feel anything).
Next suppose the same comet is near perihelion, following a hairpin orbit around the Sun. Sure, you are undergoing a large acceleration, moving you in a curved path. But so does the apple. If both of you sense the same force, you will maintain your relative positions, and so would all parts of your body. It will feel the same as no acceleration at all.
But wait! The apple may experience a different force (per unit mass) than the comet, if it is closer to the sun than the comet's center of gravity--or if it is on the side away from the sun, at greater distance. That difference, in fact, could even break up the comet itself, as has been observed (with Biela's comet). For more on that, look into the gravity gradient acting on our moon.
317. Nuclear reactors and bombsWhy does a nuclear reactor require a moderator to slow the neutrons down, but a nuclear bomb does not?
Also: Is the uranium in a nuclear bomb doped with an element that emits neutrons - in order to start the chain reaction? Or are there enough neutrons just flying around to trigger it (assuming that critical mass has been reached)?
ReplyA nuclear reactor uses slowed-down ("thermal") neutrons, while a nuclear bomb uses "fast" neutrons, emerging right after fission has occurred. The large spacing between "fuel rods" in a reactor makes sure it cannot explode like a bomb--though it may undergo "meltdown" if the nuclear reaction becomes uncontrolled (not supposed to happen, but a few times it has).
Slow neutrons are efficient in causing fission in U-235, but any such fission produces mainly fast neutrons, and if there is U-238 around, these are likely to be captured by it first (leading later to plutonium production). In a nuclear reactor, almost all these fast neutrons escape the fuel rod and wander around surrounding material, of a kind chosen not to absorb them well (such as "heavy water" or pure carbon), losing energy until they are slow enough to evade absorption. Then, if they re-enter a fuel rod, they can fission another U-235 atom. For these reasons, nuclear reactors can tolerate a fair amount of unenriched uranium containing mostly U-238, and the original "pile" of Enrico Fermi in 1942 used natural uranium with only 0.72% U-235. See
Bombs use highly enriched uranium or plutonium, with little or no U-238, and therefore can use fission by fast neutrons. Still, they need a "critical mass" for an appropriate ratio of surface area to volume. If they are too small, too many neutrons escape through the boundary and not enough are left to sustain the nuclear reaction (reactors have a somewhat similar problem). The reaction is started by explosively compressing the plutonium sphere to smaller size, and it will then spontaneously start a chain reaction, because plutonium 240 fissions and releases neutrons spontaneously at a small rate, although beryllium may also help speed up the process. See
May our world be safe from nukes.
318. Why doesn't magnetism affect electro-magnetic waves?I'm a 6th form student in the UK and it suddenly occurred to me while I was revising what we had learnt on waves and magnetic fields that, if EM waves, are indeed electro-magnetic waves, why is it that they are not affected by magnetic fields? And why do such waves not display the properties of magnetic fields in the fact that they loop from pole to pole?
Forgive me if this is a rather naive question, I do understand the principals behind EM radiation and waves quite well, its wave-particle nature, thus allowing superposition etc., but I'm just curious as to how there is such a distinction between an electromagnetic wave and a magnetic field. If one consists of the other then how is it not affected by the other, and how is it EM radiation can travel in a straight line for nearly infinite distances (gravity aside)?
ReplyElectromagnetic waves are linear--when several are added together, each preserves its identity and can be separated again. On the radio, or on TV, many stations can send their signals through the same region of space, and yet your receiver can pick out any of them and amplify it alone.
You could regard a steady magnetic field as a signal of zero frequency (taking forever to switch to its electric signature). It does not interact with any electromagnetic waves of non-zero frequency, at least in vacuum.
In a material medium the magnetic field may modify the electromagnetic properties of the medium, affecting the propagation of waves. For instance, the Faraday effect in transparent media may rotate the plane of polarization of an electromagnetic wave.
In a plasma (gas containing freely floating ions and electrons) many different kinds of modified electromagnetic waves are possible--depending on the frequency of the wave and how far it is from some characteristic resonances, which depend on density and magnetic field in the plasma. In particular, "Whistler Waves" (in space near Earth they are produced by lightning at frequencies like 3000 Hz) are indeed guided by field lines, sometimes bouncing back and forth from one hemisphere to the other.
319. Is humanity changing the climate, or is it the Sun and the Earth's magnetism?Can you comment how climate change is affected by the earth's magnetic field, the sun's output, and other directly and not so directly related factors?
Where I can read about such theories? I have tried to understand the common reasoning about man being directly responsible for (however you label it) Global Warming, Climate Shift, etc. However, based on the sheer magnitude of such changes, I find that man-made causes are the most dubious direct factors. Among the other far larger factors, man's impact adds at most an assist or a catalyst to the equation.
It would seem to me that the earth's magnetic field might have a huge impact on how the sun's various and changing outputs are directed and distributed around our globe. Changes in the sun's output and changes in the earth's magnetic field seem to greatly affect global changes, with no input from mankind needed.
However, I have heard very little discussion of this highly suspect aspect of the discussion. It is almost as if the science of the sun and the earth, in areas where you appear to be an expert, have been curiously absent from the debate. Is this due to political pressure? Has the objective process of true scientific discovery started to buckle under the pressure of political correctness? Al Gore and Ponzi scheme carbon credits be damned!
ReplyI do not think magnetism has any connection to global warming. There is too little energy in the solar wind or its magnetic field, compared to the flood of energy we receive in the form of heat from sunlight.
Global warming is caused by molecules in the atmosphere, as described in
(you may like to browse that entire collection, too). Sunlight heats the ground, except for the small part reflected by clouds (something like 20%, I think), and some more scattered by dust and atomic processes. It reaches the ground, because air is transparent to visible light. Atoms can emit and absorb such light (though in general only in narrow ranges of wavelength), but atoms in the air are combined in molecules, which generally do not absorb.
But obviously, heat absorbed by the ground must return to space--otherwise Earth would just get hotter and hotter. In fact Earth radiates its heat by the same broad process as the Sun--the process which makes any heated object shine in electromagnetic radiation. With the Sun those are visible wavelengths, because of its 6000 deg temperature; luckily it is a small object in the sky, otherwise we'd quickly get fried. The Earth is only moderately warm, so it radiates in the infra-red. That is a weaker radiation, but it goes out in all directions, and can therefore balance the sun's input.
Molecules, as it happens, absorb and emit infra-red. They too are tuned to certain "frequency bands", not as sharp as atomic resonances but also depending on the substance. Water vapor, for instance, is a "greenhouse gas": it absorbs infra-red in its resonant frequencies, re-emits it, higher up it is absorbed again and re-emitted, and so on up to the high levels, which are dry and rarefied, allowing the radiation to escape to space. Were it not for water vapor, Earth may have been in a permanent ice age.
But there exist other wavelength bands which water vapor does not cover: carbon dioxide, methane and ozone cover some of these, and that is where human influence makes a difference. It is a serious effect. Put one drop of India ink in a glass of water and note how much darker it gets. Similarly, a moderate amount of an additional "greenhouse gas" can seriously slow down the escape of heat from the surface, by closing (or at least narrowing down) yet another wavelength window through which heat escapes. If that happens, the surface of the Earth needs to radiate more strongly to keep up with what arrives from the Sun. Climate gets hotter, oceans warm up and expand to flood seacoasts, and so forth.
I hope that made it clear. Enjoy my web sites!
By the way--the heat output from the Sun might conceivably vary too, which is why NASA has put very sensitive detectors of total radiation on some spacecraft (measurements from the ground are not accurate enough, the atmosphere absorbs and scatters too much of the light). These have found some tiny variations associated with sunspots and their cycle, but nothing to explain global warming.
320. Advice to home-schooling parentIn the process of searching for an Astronomy curriculum for my home-schooled high school senior, I came across your website.
I am interested in getting this curriculum for my daughter. Will she be able to complete the course work online? Or should I purchase the CD as well? I am not a very "technical" individual, but my daughter is! She desires to become an astrophysicist. I'm confident she'll achieve her goal because she has the passion for it as well as the understanding in math and science. Thank you for your help.
Could you please also provide a working link to the poems listed on your website, e.g. those by Bialik? I was not able to access them using the provided link.
ReplyThe central linking page is
You should be able to reach any of my files from there, including the poetry. The home page for the non-science pages is
As a home-schooling parent, you can buy a disk from April Dykes in Texas (see link at the end of big yellow box at the start of "From Stargazers to Starships"), but if you have a DSL web connection (or patience) you can also download the files to your computer (about 40 Mb) as "zip-archives" which automatically create the proper files after they are downloaded. The web addresses for this are on the "readfirst" page linked above. Of course, you can also copy them after that from your hard drive onto disks.
One thing you might want are solutions to problems of "Stargazers," made available only to teachers and teaching parents (the problems are listed at the end, in two sections). They will be attached to this message (but readers of this shouldn't expect them here!): please do NOT pass them any further (except to other homeschooling parents, who agree to abide by a similar restriction). They are not for your daughter--let her figure them out!
"Stargazers" is a course in physics and astronomy. Over the years it has grown far too big to be given in a regular classroom
(see http://www.phy6.org/stargaze/Scaution.htm )
but a determined teenager can cover most of it--depending on motivation and on competing interests, of course. Get her started on sections 1 to 11 of "Stargazers" and see how much time they take: if progress is too slow, some parts may need to be skipped or abbreviated.
YOU are the teacher. Therefore, even though your daughter may roam through the material at will, you should acquire an understanding of it, too, preferably ahead of her. The 46 lesson plans may help. Much more can be said, but homeschooling parents learn to improvise, and if your daughter has reached the senior level, I am sure you can do that well by now. Some thoughts:
---The questions and answers at the end of sections are a selection of what users have written (and my answers to them). They often clear up problems by viewing them from a different angle.
---The math course may help, if your daughter's math has gaps. It does have some problems to solve, too.
---The timeline (especially the one in "Stargazers") is useful for integrating history and science, and helping see the overall framework.
---If your daughter is studying Spanish as a foreign language, she may find it fun to read the Spanish translations together with the original English web pages. (Or the French, or Italian.)
Final thought: becoming an astrophysicist is hard and may be frustrating. Your daughter should read an exchange I had with a student in India, at about the same age, with the same question:
All the same, I wish you and your daughter every possible success.
321. Science of Clothing Have any ideas about how to introduce some of the concepts which you discuss to 6th graders -- girls in particular? Any advice you can provide will be greatly appreciated. Thanks so much for sharing your knowledge on the internet.
(Later additional message) What I'm most interested in is the science of clothing: how can I apply angles, force, friction, color theory perhaps? All this, to show girls that there is science behind fashion.
Reply There is science behind clothing, but it is mostly chemistry (dyes, fabrics...) and I happen to be a physicist. The physics involved is mainly related to heat insulation: why is a fluffy fabric so much better as a barrier to loss or entry of heat than a solid heavy material--bricks or metal, say? It has to do with the trapping of air and stopping it from circulating; air is a poor conductor of heat, but it can transport heat by circulating (as it does in the atmosphere). Wool and feathers have finer fibers than cotton, so they are most efficient in trapping air and in cold climate they are best.
On the other hand, cotton draws water and fluids, so for candle wicks and clothes in hot climate--to shield the sun but keep the skin cool--cotton is preferred. Desert Arabs (e.g. Tuaregs) wear a cotton shawl over their mouth: when you breathe out moist air, some of it is caught by the fibers and helps moisten the air you next breathe in, with water you otherwise may have breathed out and lost. And the Polynesians have their culture based on Tapa cloth, a felt made of fibers--the kind of fabric used before spinning and weaving were invented.
About colors, see
including maybe the section "experimenting with color"--if you have access to computers. You may need some help there. By the way, the color "orange" comes from the Indian name for the fruit (naranja), not from the name of the royal house of Holland. There exists a whole lore of color--Tyrian purple, mauve (first artificial dye), saffron, khaki, indigo and so on.
But I would rather use clothing to teach language: Muslin comes from Mosul in northern Iraq, Calico from Calicut in India (calico cats have patches of color like that cloth; and tabby cats resemble a cloth made in the Attabi quarter of Baghdad), Damask originated in Damascus, seersucker, pajama, dungaree, denim--let the girls search dictionaries on their own, also words like distaff and hose (pants in German are "hosen")... so much more.
Let them look through the book of Marco Polo and learn his story... being a merchant, wherever he traveled, he often noted what kind of fabric the city specialized in. In one place he was shown a fabric which could be put through a flame and not burn: I guess it was asbestos.
And then of course all those artificial fibers. But sorry, I am just a physicist, who specialized in space research. Ask someone from the textile industry!
322. Calculating a CollisionI saw your website and thought you have great answers to many questions. I hope you can help me figure out what I know is a probably a basic physics problem. I could be doing this wrong but I'd like to know. There was a story I read recently about a 1,500 lb wrecking ball that came loose, rolled downhill, and smashed into a car moving it 20 feet. The car weighs about 2,400 lbs, I would imagine. I was trying to formulate a way to calculate how fast the ball must have been rolling, using "slugs."
(A detailed calculation followed).
Is this right?:
ReplyYour answer is probably not the right one, and in fact the problem cannot be solved without added information about the roughness of the surface. The same force will push the car much further if it is standing on smooth ice then in a plowed field!
You need to know the coefficient of friction k (my notation here, many tests use μ), the ratio (in this case) between the (horizontal) force of friction on a moving object and the (vertical) weight causing that friction. It is an observed fact that k is almost independent of speed, so whether you move fast or slowly, the friction force is the same. We assume so here--without doing so, the problem becomes even more complicated and more assumptions need to be made.
The value of k can vary anywhere from about 0.02 (car on smooth road, axles greased and turning freely, tires well inflated) to 1.00 (car with brakes applied tightly, to where it would not slide even on a 45-degree slope). Let me assume here k=0.2.
You must also assume something about the collision--most likely, an inelastic collision, in which the ball smashes into the car, after which the two travel together.
I am not familiar with calculation in slugs and feet--most of the world (especially technical people) uses the metric system, so excuse me if I solve a slightly different problem--a 700 kg ball hitting a car weighing 1100 kg, moving it 6.1 meters.
Say the ball started with velocity v, and after impact, car and ball continued together with velocity u. By the conservation of momentum (section #18b)
700 v = (700 + 1100) u = 1800 u
The kinetic energy of the (car + ball), after impact is
0.5 m u2 = 0.5 (1800) u2 = 900 u2 joule.
This is converted to heat of friction by dragging car and ball over a distance of 6.1 meters, against a friction force F, equal to 0.2 times the weight F' of the object being moved. We get F' = mg (section #18) by multiplying mass (1800 kg) by the acceleration of gravity, which is 9.8 m/sec2, so
F' = 1800 . 9.8 = 17,640 Newton
F = 0.2 F' = 3528 Newton
The work W performed (section #18c) equals the force F being overcome times the distance, and by conservation of energy, it should equal the initial kinetic energy 900 u2 (the final kinetic energy is zero). So
W = 21520.8 joule = 900 u2
u2 = 23.912
u = 4.89 meters/second
v = (1800/700) 4.89 = 12.57 meter/sec
which is about the velocity of a ball falling from a height of 12 meters. We ignore the fact the ball is rolling and assume it is sliding. Otherwise the calculation is more complicated, since the rolling motion takes up some of the kinetic energy. A ball rolling down a slope from 12 meter height is slower than one sliding (without friction) down the same distance, because some of the energy of gravity goes into the rotation of the ball.
You see how complicated real-life problems can become!
RsponseThanks! Yes, it is all about the friction, and I'll think in metrics from now on. Since the police report was in feet and pounds, I used slugs. Also thought it would be hard to calculate velocity since the car was slowing down after being hit by the ball. I very much liked this part of your explanation:
323. The Coriolis force and moreOn your website you state that the Coriolis force is too small to affect the rotation of water down a toilet, yet the water does flow in opposite directions in the Northern Hemisphere as compared with the Southern Hemisphere. What else would explain this phenomena?
The Coriolis acceleration I learned in school from Prof Wills at CCNY is described as a vector equation as follows:
Ac = 2 ω x V
where ω is the vector describing the angular velocity of the rotating earth, approx 70 micro-radians per second, V is the velocity vector and Ac is the coriolis acceleration. It is approximately 0.004 feet/second squared, which is small but perhaps large enough to start water flowing in different directions down a smooth toilet bowl.
I enjoy reading your web site just as I enjoyed reading the books of George Gamow in the 50s.
Why are all planetary bodies planets, stars, etc. round? Asteroids may be pear shaped but most bodies are round, why are some not shaped like a disk? Why does gravity exist at all? Did Einstein ever discuss that issue?
ReplyYour formula is correct, assuming V is the velocity vector in the rotating frame of reference (velocity in addition to the one resulting from being carried around by the Earth's rotation itself) and x denotes vector multiplication, which also depends on the sine of the angle between the direction of motion (vertical, for draining water) and the Earth's axis.
However, the rotation induced by the Coriolis force F = m Ac depends not just on F. It also depends on the variation of F between the two sides of the descending or rising fluid. If F is the same on both sides, the entire motion just gets deflected to one side. Rotation is produced because F is smaller on the point closer to the pole. Near the pole omega is almost parallel to V, making 2(ω x V) very small.
That is why hurricanes are affected--they are much bigger--and draining sinks are not. In Jupiter's red spot, which is still bigger, the effect is even more pronounced--and Jupiter also rotates faster than Earth. In fact Voyager's pictures of Jupiter show many additional swirls in its atmosphere.
Why are planetary bodies round? You would expect gravity to make them so, if they were all liquid or gas--any bump rising on the surface would be pulled down to its level. In a big planet like Earth, the force of gravity is strong enough to force the material into the shape of a sphere. Rocks on the surface can vary in elevation, but at a depth of 100 km (say), the weight of layers piled up above makes even rocks adjust their level as if they were fluid.
That is the reason no mountain on Earth reaches even 10 km: the weight of mountains pulls them down. On Mars, the highest volcano can rise to about 25 km, because gravity is weaker. Asteroids and moons up to about 500 km can maintain irregular shapes, but if they are larger, gravity causes them to become round. See also question 305 in this collection.
All this in the absence of rotation. Slow rotation makes the shape elliptical (oblate), a small effect on Earth, a larger one on Jupiter and Saturn. But a limit exists: speed up the rotation too much, and the planet breaks up to a disk, somewhat like the rings of Saturn.
See also reference 26 on the list on top.
Finally, why does gravity exist? We don't know any more fundamental reason, except maybe that if it did not, the universe and Earth would not exist, and we would not be here to ask questions. For us, and for Einstein too, gravity has been a fundamental force of nature, and we are still trying to understand its properties (see http://www.phy6.org/stargaze/Sun4Adop3.htm )
324. Why isn't the solar system stratified by density?I'm a law student (sigh) from Germany, and I spend way too much time thinking about physics
A question has been nagging me some time now.
I've been thinking through the formation of the solar system: ok, so we have this huge gaseous cloud compressed into a disk by it's own gravitational pull. Seeing that the disk is still rotating I assume a centrifugal force to be exerted on it which leads the elements it is comprised of to distribute according to their specific mass, lightest at the core, heaviest at the edges. Next step, they clump into pieces. OK, so far so good, plenty of hydrogen at the core, massive planets following and then the asteroid belts that for some funny reason don't want to stick together (maybe the pull of nearby Jupiter disrupted their clumping).
BUT THEN: the gas giants. I mean. Excuse me? Is my thinking that flawed? Isn't that gas supposed to be in the sun to give us a few more years of gentle warmth? Hydrogen and helium? (I imagine some kind of dialogue of the type "hey, what is such a cute and especially light couple doing out here at this time?") Could it be possible that it's the hydrogen scooped up from deep space AFTER the formation of the core solar system? I just don't get it. Where did I go wrong? What did I miss?
ReplyYou are asking intelligent questions, and it is not easy to answer them, especially without mathematics. If you go on with your studies, I wonder if you end up practicing patent law, where such questions sometimes arise.
Why doesn't the solar system separate--light stuff in the middle, heavy stuff outside? Let's look at a situation where this DOES happen: a very tall glass (tall enough so you need not worry about friction with the bottom) filled with a mixture of gasoline and water, and stirred into rotation by a long spoon, or maybe a paddle attached to a motor.
You know what will happen: the water which is heavier will gradually move outwards, and the gasoline which is lighter will be near the middle. In the rotating frame of the fluid, every bit of matter experiences an outwards-directed centrifugal force (sections #23 and #23a in "Stargazers"). If two equal globules rotate side by side, one of gasoline and one of water, the one of water is denser and senses the greater force, so it moves out while pushing the lighter gasoline inwards.
Now replace this by a solar nebula, rotating because of some systematic average motion it had when it started to pull together. No spoon or paddle is necessary--it just rotated when it came together, and there is nothing to stop it. The centrifugal force may be said to be balanced by gravity (or else, looking from a non-rotating frame, the centripetal force is supplied by gravity). If some material moves out, it slows down, but has then larger potential energy, so it regains its speed as is moves in again--as, say, Halley's comet does (see section on Kepler's 2nd law, section dealing with energy).. This holds for light and heavy material alike, for dust and gas, and in this motion, materials do not separate. The difference is that instead of glass walls, you have here the force of gravity, and it behaves differently.
At early times, however, you expect parts of the "solar nebula" to also have large random motions, producing many collisions between dust grains and gas molecules moving in different directions. Such collisions convert energy into heat, and help material concentrate in the middle, where the Sun is formed. The Sun also rotates, but its angular momentum (which measures its rotation) is rather small, compared to that left in the planets. (This process, by the way, is also discussed in the reply to question 315 above).
When the Sun started to glow, it evaporated much of the material which has collected around it, and those molecules were blown away--by light pressure maybe (this is not my area). The gas giants were distant and escaped great heating; comets and distant moons also stayed frozen. But Earth and Venus are lucky to keep their atmospheres; they may well have once had big hydrogen clouds around them, too, before the Sun blew them away.
These at least are my thoughts; you might ask an astronomer, who might have better information. My real field is the magnetic field of the Earth and ions and electrons moving in it.
Go to main list of questions (by topic) | 0.930756 | 3.284732 |
NASA’s Galileo spacecraft arrived at Jupiter on December 7, 1995, and proceeded to study the giant planet for almost 8 years. It sent back a tremendous amount of scientific information that revolutionized our understanding of the Jovian system. By the end of its mission, Galileo was worn down. Instruments were failing and scientists were worried they wouldn’t be able to communicate with the spacecraft in the future. If they lost contact, Galileo would continue to orbit the Jupiter and potentially crash into one of its icy moons.
Galileo would certainly have Earth bacteria on board, which might contaminate the pristine environments of the Jovian moons, and so NASA decided it would be best to crash Galileo into Jupiter, removing the risk entirely. Although everyone in the scientific community were certain this was the safe and wise thing to do, there were a small group of people concerned that crashing Galileo into Jupiter, with its Plutonium thermal reactor, might cause a cascade reaction that would ignite Jupiter into a second star in the Solar System.
Hydrogen bombs are ignited by detonating plutonium, and Jupiter’s got a lot of hydrogen.Since we don’t have a second star, you’ll be glad to know this didn’t happen. Could it have happened? Could it ever happen? The answer, of course, is a series of nos. No, it couldn’t have happened. There’s no way it could ever happen… or is there?
Jupiter is mostly made of hydrogen, in order to turn it into a giant fireball you’d need oxygen to burn it. Water tells us what the recipe is. There are two atoms of hydrogen to one atom of oxygen. If you can get the two elements together in those quantities, you get water.
In other words, if you could surround Jupiter with half again more Jupiter’s worth of oxygen, you’d get a Jupiter plus a half sized fireball. It would turn into water and release energy. But that much oxygen isn’t handy, and even though it’s a giant ball of fire, that’s still not a star anyway. In fact, stars aren’t “burning” at all, at least, not in the combustion sense.
Our Sun produces its energy through fusion. The vast gravity compresses hydrogen down to the point that high pressure and temperatures cram hydrogen atoms into helium. This is a fusion reaction. It generates excess energy, and so the Sun is bright. And the only way you can get a reaction like this is when you bring together a massive amount of hydrogen. In fact… you’d need a star’s worth of hydrogen. Jupiter is a thousand times less massive than the Sun. One thousand times less massive. In other words, if you crashed 1000 Jupiters together, then we’d have a second actual Sun in our Solar System.
But the Sun isn’t the smallest possible star you can have. In fact, if you have about 7.5% the mass of the Sun’s worth of hydrogen collected together, you’ll get a red dwarf star. So the smallest red dwarf star is still about 80 times the mass of Jupiter. You know the drill, find 79 more Jupiters, crash them into Jupiter, and we’d have a second star in the Solar System.
There’s another object that’s less massive than a red dwarf, but it’s still sort of star like: a brown dwarf. This is an object which isn’t massive enough to ignite in true fusion, but it’s still massive enough that deuterium, a variant of hydrogen, will fuse. You can get a brown dwarf with only 13 times the mass of Jupiter. Now that’s not so hard, right? Find 13 more Jupiters, crash them into the planet?
As was demonstrated with Galileo, igniting Jupiter or its hydrogen is not a simple matter.
We won’t get a second star unless there’s a series of catastrophic collisions in the Solar System.
And if that happens… we’ll have other problems on our hands. | 0.82406 | 3.681288 |
A new study using data from NASA’s NuSTAR space telescope suggests that the most luminous and massive stellar system within 10,000 light-years, Eta Carinae, is accelerating particles to high energies -- some of which may reach Earth as cosmic rays.
Cosmic rays with energies greater than 1 billion electron volts (eV) come to us from beyond our solar system. But because these particles -- electrons, protons and atomic nuclei -- all carry an electrical charge, they veer off course whenever they encounter magnetic fields. This scrambles their paths and masks their origins.
Eta Carinae, located about 7,500 light-years away in the southern constellation of Carina, contains a pair of massive stars whose eccentric orbits bring them unusually close every 5.5 years. The stars contain 90 and 30 times the mass of our Sun.
Both stars drive powerful outflows called stellar winds, which emit low-energy X-rays where they collide. NASA’s Fermi Gamma-ray Space Telescope observes gamma rays -- light packing far more energy than X-rays -- from a source in the direction of Eta Carinae. But Fermi’s vision isn’t as sharp as X-ray telescopes, so astronomers couldn’t confirm the connection.
To bridge this gap, astronomers turned to NASA's NuSTAR observatory. Launched in 2012, NuSTAR can focus X-rays of much greater energy than any previous telescope. The team examined NuSTAR observations acquired between March 2014 and June 2016, along with lower-energy X-ray observations from the European Space Agency’s XMM-Newton satellite over the same period.
NuSTAR detects a source emitting X-rays above 30,000 eV, some three times higher than can be explained by shock waves in the colliding winds. For comparison, the energy of visible light ranges from about 2 to 3 eV.
The researchers say both the X-ray emission seen by NuSTAR and the gamma-ray emission seen by Fermi is best explained by electrons accelerated in shock waves where the winds collide. The X-rays detected by NuSTAR and the gamma rays detected by Fermi arise from starlight given a huge energy boost by interactions with these electrons.
Some of the superfast electrons, as well as other accelerated particles, must escape the system and perhaps some eventually wander to Earth, where they may be detected as cosmic rays.
Eta Carinae shines in X-rays in this image from NASA's Chandra X-ray Observatory. The colors indicate different energies. Red spans 300 to 1,000 electron volts (eV), green ranges from 1,000 to 3,000 eV and blue covers 3,000 to 10,000 eV. For comparison, the energy of visible light is about 2 to 3 eV. NuSTAR observations (green contours) reveal a source of X-rays with energies some three times higher than Chandra detects. X-rays seen from the central point source arise from the binary’s stellar wind collision. The NuSTAR detection shows that shock waves in the wind collision zone accelerate charged particles like electrons and protons to near the speed of light. Some of these may reach Earth, where they will be detected as cosmic ray particles. X-rays scattered by debris ejected in Eta Carinae's famous 1840 eruption may produce the broader red emission. | 0.907048 | 4.084827 |
HomeGearTop 5 Targets for Skywatchers Charles October 21, 2016 Gear, Sky Ryan Wick A computerised telescope If you’ve just purchased your first telescope, then congratulations – you’re about to experience a world of discovery right in your backyard. With a modest telescope or even a decent pair of binoculars, you’ll be able to see numerous planets, stars, nebulae and other astronomical objects that appear only as tiny dots of light to the naked eye, if indeed you can even see them at all. If you’re wondering what the most spectacular objects in the night sky are, then consider training your new telescope on the following easy targets for skywatchers: #1. Venus Thanks to its highly reflective atmosphere and relative proximity to Earth, Venus is by far the brightest object in the night sky aside from the moon. Earth’s evil twin appears as a cloudy white disk through even a small telescope or powerful pair of binoculars. Depending on the time of year, Venus is best viewed either shortly after sunset or sunrise. Due to Venus being an inferior planet (i.e.: closer to the Sun than Earth), it also has phases, which you’ll be able to see with a good enough telescope. However, you won’t see any surface details due to the immensely thick atmosphere. #2. Jupiter For first-time telescope users, Jupiter is perhaps the most impressive sight of all. With the naked eye, it looks like nothing more than a bright star, but even with a modest telescope, the Solar System’s largest planet reveals itself splendidly. At the very least, you should be able to see the four Galilean moons, Io, Europa, Callisto and Ganymede as points of light near the planet. With something slightly more powerful with a five-inch aperture, you’ll even be able to see bands of clouds in its atmosphere as well as the centuries-old storm that is the Great Red Spot. #3. Mars Like the other planets, Mars looks much like a star to the naked eye, but with a good telescope, you’ll be able to see a lot more. Train your telescope to Mars, and you should be able to see a small red disk at the very least. With a slightly more powerful telescope, you will even be able to make out the polar icecaps. Those with the best telescopes might even be able to spot some clouds, particularly near the equator. Mars is at its closest point to Earth only once every two years, during which its surface features are far more visible in front of a telescope. #4. Andromeda Also known as Messier 31 or M31, Andromeda is the nearest galaxy to the Milky Way and, at 2.5 million light-years away, it’s by far the most distant object visible to the naked eye. However, with a powerful set of binoculars, Andromeda will transform from what looks like just another star to a disc with a bright centre, clearly distinguishing it from the stars. You should also be able to see its two largest satellite galaxies – M32 and M110. However, for the best viewing experience, you’ll need to be far away from any city lights and observe on a moonless night. #5. Orion Nebula The Orion Nebula is a region where new stars are born some 1344 light-years away. It is the easiest nebula to see through a telescope, and it is one of the better targets for viewing in areas where there is considerable light pollution. Through a small telescope, you should see a greyish cloud, but with more powerful equipment, you may even be able to make out colours of green and red leaping out of the bright core that is a birthplace for new stars. When looking for the nebula, start in Orion’s Belt, which consists of three bright stars, and locate the fuzzy area, which is the nebula. Conclusion First-time skywatchers often find it difficult to get the right targets, so it is important to adequately prepare yourself for your evening of observing the heavens. As such, novices will be best off with a telescope that features a star finder, such as the Celestron beginner series, which will locate targets based on the time of day and year and their geographical locations. However, an almanac, such as Patrick Moore’s Yearbook of Astronomy, detailing visible astronomical targets throughout the year will undoubtedly come in handy too. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on WhatsApp (Opens in new window)Click to email this to a friend (Opens in new window) Leave a Reply Cancel ReplyYour email address will not be published.CommentName* Email* Website Please enter an answer in digits:fifteen + 15 = Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. | 0.82961 | 3.209625 |
Astronomers have been awarded 45 million units of supercomputing time to study the influence of supermassive black holes on their host galaxies.
The team from WA, Tasmania and the UK were awarded the time on Australia’s largest research supercomputing facility, the National Computational Infrastructure (NCI Australia) in Canberra.
They will use it to combine computer models of black holes—and the jets that shoot out of them—with large-scale cosmological simulations of the Universe.
Associate Professor Chris Power, from the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), is leading the research.
He said black holes can have a profound effect on how galaxies evolve.
“Black holes produce very powerful jets and winds,” he said.
“We know they can stop stars forming, and create the different kinds of galaxies we see in the Universe today.
“But the problem is that we have a very cartoonish understanding of how this process works.”
The researchers will use the supercomputer time to study how powerful jets from black holes impact their larger galactic and cosmic environments.
They will combine sophisticated cosmological simulations of galaxy formation, developed at ICRAR, with detailed models of black hole jets, developed by Dr Stanislav Shabala and PhD student Patrick Yates at the University of Tasmania.
The team also includes researchers from the University of Hertfordshire.
Associate Professor Power said running the simulations on a laptop computer would take almost 5,000 years.
“On the supercomputer, we’ll probably get results in a couple of days,” he said.
“So we want to be able to run hundreds of these kinds of simulations. We’re basically treating them as experiments.”
The astronomers will tweak their models with each simulation, improving our understanding of how black holes change their host galaxies.
“It’s a bit like when we go into a lab and we’re pouring combinations of chemicals into test tubes—we can see what kinds of things happen,” Associate Professor Power said.
The study will be one of the first to run on NCI’s brand new supercomputer Gadi, and will be undertaken over the next six to nine months.
It was one of four awarded time through the Australasian Leadership Computing Grants program, which attracts bids from researchers all over the country.
The other projects will conduct research in global climate modelling, decadal climate forecasts and combustion for low emissions gas turbines. More at NCI Australia.
A/Prof. Chris Power (ICRAR / University of Western Australia)
Ph: +61 478 906 421 E: [email protected]
Kirsten Gottschalk (Media Contact, ICRAR)
Ph: +61 438 361 876 E: [email protected] | 0.840224 | 3.453827 |
新概念英语－听录音，并回答问题When will it be possible for us to think seriously about colonising Mars?
新概念英语 - 小编笔记
新概念英语 - 教材原文
The Moon is likely to become the industrial hub of the Solar System, supplying the rocket fuels fro its ships, easily obtainable from the lunar rocks in the from of liquid oxygen. The reason lies in its gravity. Because the Moon has only an eightieth of the Earth's mass, it requires 97 per cent less energy to travel the quarter of a million miles from the Moon to Earth-orbit than the 200 mile-journey from Earth's surface into orbit! This may sound fantastic, but it is easily calculated. To escape from the Earth in a rocket, one must travel at seven miles per second. The comparable speed from the Moon is only 1.5 miles per second. Because the gravity on the Moon's surface is only a sixth of Earth's (remember how easily the Apollo astronauts bounded along), it takes much less energy to accelerate to that 1.5 miles per second than it does on Earth. Moon-dwellers will be able to fly in space at only three per cent of the cost of similar journeys by their terrestrial dwellers will be able to fly in space at only three per cent of the cost of similar journeys by their terrestrial cousins.
Arthur C. Clark once suggested a revolutionary idea passes through three phases:
- 1 'It's impossible -- don't waste my time.'
- 2 'It's possible, but not worth doing.'
- 3 'I said it was a good idea all along.'
The idea of colonising Mars -- a world 160 times more distant time the Moon -- will move decisively from the second phase to the third, when a significant number of people are living permanently in space. Mars has an extraordinary fascination for would-be voyagers. America, Russia and Europe are filled with enthusiasts -- many of them serious and senior scientists -- who dream of sending people to it. Their aim is understandable. It is the one world in the Solar System that is most like the Earth. It is a world of red sandy deserts (hence its name -- the Red Planet), cloudless skies, savage sandstorms, chasms wider than the Grand Canyon and at least one mountain more than twice as tall as Everest. It seems ideal for settlement.
--7 DAYS, February 19, 1989--
新概念英语－单词和短语hub n. （活动的）中心
lunar adj. 月球的
oxygen n. 氧气
Apollo n. 阿波罗
accelerate v. 加速
terrestrial adj. 地球的
permanently adv. 永远地
fascination n. 魅力
senior adj. 资历深的，年长的
chasm n. 断层，裂口
canyon n. 峡谷
月球很可能成为太阳系的工业中心。从月球上的岩石中很容易提炼出液态氧，作为航天飞船的燃料。其原因在于月球的重力。因为月球的重只有地球的1/8，因此，从月球到地球的25万英里所消耗的能量要比从地球表面进入地球轨道的200英里所耗能量少97%。 这点听起来令人难以置信，但却很容易计算出来。要乘坐一枚火箭飞离地球，火箭的速度要达到每秒7英里，而从月球出发的相应速度史是每秒1.5英里。由于月球表面的重力仅是地球表面的1/6 -- 还记得阿波罗飞船中的宇航员累松地跳跃 -- 在月球上加速到每秒1.5英里比在地球上所用能源要少得多。月球居民在太空遨游的费用仅是地球上朋友飞越同样路所需费用的3%。
如果有相当数量的人永久性地住在太空，征服火星的计划 -- 一个比月球远160倍的星球 -- 就可以明确地从第2阶段进入第3阶段。火星对未来的星际旅客说有着特殊的魅力。美国、俄罗斯和欧洲都有许多热心此项事业的人 -- 其中的不少是认真和资深的科学家，他们一直梦想着把人送上火星。他们的目标是可以理解的。火星是太阳系里与地球最接近的一颗行星。这是一个红色沙漠的世界（因而得名：红色行星），无云的天空，凶猛的沙暴，比大峡谷还宽的裂缝，起码有一座山有珠穆朗玛峰的近两倍高。看起来，它很合适居住。 | 0.820972 | 3.202971 |
An interstellar comet revealed
Comet 2I/Borisov. Photo: Gemini Observatory/NSF/AURA
The big picture: Comet 2I/Borisov represents just the second-known interstellar object to make its way through our solar system, and it's astronomers' best chance so far to study a piece of a distant star system at close range.
- Even if it does turn out that the comet is just like those native to our solar system, it will show astronomers that other planetary systems light-years from our own likely formed in similar ways.
What they found: Unlike the strange cigar shape of the first interstellar object — named 'Oumuamua and seen in 2017 — 2I/Borisov has a pronounced dust tail and a reddish color that can be compared to other comets, according to the study.
- "In combination with what we have learned from peculiar `Oumuamua, it tells us that there may be a lot of diversity in other planetary systems and the formation of minor bodies," Piotr Guzik, one of the authors of the new study, told Axios via email.
- The team began its observations of the comet on Sept. 10, using the Gemini North Telescope in Hawaii and the William Herschel Telescope in Spain.
"This is a quick first look at the object and is showing what everyone has seen who has been observing this."— University of Hawaii astronomer Karen Meech, who did not take part in the study, told Axios via email
What to watch: Astronomers will be keeping a close eye on 2I/Borisov as long as it's visible from Earth.
- An earlier study submitted to The Astrophysical Journal Letters found cyanogen, a common molecule in solar system comets, in 2I/Borisov's atmosphere.
- However, the comet still isn't in the perfect position to be able to get a good look at its chemical signature yet.
- As the object gets closer — with its closest flyby of the Sun expected in early December — scientists should be able to piece together the chemical makeup of the comet's atmosphere and figure out just how familiar or alien it really is. | 0.910145 | 3.656542 |
One of Saturn’s moons has a secret, and scientists are trying to figure out what it is.
A Cornell University astronomer has been studying measurements of the wobble of Saturn’s small, icy moon Mimas taken by the Cassini spacecraft, and he and his team have determined that under all that ice there must be either an irregular “rugby-ball-shaped” rocky core or an underground ocean sloshing about.
“After carefully examining Mimas, we found it librates — that is, it subtly wobbles — around the moon’s polar axis,” Radwan Tajeddine, Cornell research associate in astronomy and lead author of the article. “In physical terms, the back-and-forth wobble should produce about 3 kilometers of surface displacement. Instead we observed an unexpected 6 kilometers of surface displacement,” he said.
“We’re very excited about this measurement because it may indicate much about the satellite’s insides. Nature is essentially allowing us to do the same thing that a child does when she shakes a wrapped gift in hopes of figuring out what’s hidden inside,” Tajeddine said.
Mimas is just 400 kilometers in diameter and sometimes referred to as the “Death Star” moon because of its resemblance to the to the Star Wars weapon. The wobble was determined using a technique called stereo-photogrammetry, which put together various photographs taken of Mimas by Cassini and created a computer model to compare hundreds of reference points, which showed an irregularity in the moon’s rotation.
The team hasn’t determined yet whether it is water or rock inside the moon. Any ocean would be 25 to 30 kilometers under the moon’s icy crust. If it is the weirdly shaped rocky core its irregular shape might be explained by gravitational flattening by Saturn.
[Source: Cornell University] | 0.875603 | 3.651498 |
This is an image of the solar system.
Click on image for full size
The Beginning of the Solar System
Scientists believe that the solar system was formed when a
cloud of gas and dust in space was disturbed, maybe by the expl
osion of a nearby star (called a
This explosion made waves in space which squeezed the cloud of gas and dust.
Squeezing made the cloud start to collapse, as gravity pulled
the gas and dust together.
Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cool at the edges.
As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moons .
Near the center of the cloud, where planets like Earth formed, only rocky material could stand the great heat. Icy matter settled in the outer regions of the disk, where the giant planets like
As the cloud continued to fall in, the center eventually got so hot that it became a star, the Sun, and blew most of the gas and dust of the new solar system. By studying fragments of rock left over from this early phase of the solar system, scientists have found that the solar system is about 4600 million years old!
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“It didn’t seem to be any different than the other near-Earth asteroids that we discover,” Dr. Wierzchos said, “except that it was found to be orbiting Earth instead of the sun.”
If the discovery holds up, the object, named 2020 CD3 for now, would be the second mini-moon ever found.
“They are orbiting roughly the same space that we are, and some will get into the right spot where it can nudge into a ballet with us. And then it’s like any dance: you do a couple of spins together, and go your separate ways,” she says. “There’s something beautifully transient about it.” [NY Times]
BIG NEWS (thread 1/3). Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object. Here are the discovery images. pic.twitter.com/zLkXyGAkZl
— Kacper Wierzchoś (@WierzchosKacper) February 26, 2020
Shortly after this discovery was made, some astronomers over at the Minor Planet Center took some time to collect some data on the object. At the time, they weren’t able to make any calls in terms of its exact contents, but they were able to confirm that it wasn’t just a random piece of leftover rocket debris. Our new moon is the size of a small car, probably most comparable to a smart car. Alesondra Springman, an astronomer at the University of Arizona, even stated that it could probably fit in a bedroom.
Astronomers and researchers will be keeping a close eye on the object. The new moon is temporary and will be leaving in a matter of time. Apparently, there will be more celestial objects joining earth orbit relatively soon.
It is pretty interesting to see how there are still quite a few things that can surprise us when it comes to looking up at the sky. I’ll be perfectly honest, though when I heard that it was a moon, I thought it was going to be a little bit bigger than a car. Recently we’ve seen a couple of sudden surprises coming from space. As a matter of fact, we almost got hit by an asteroid last year because it “snuck up” on us. I would be more partial toward a more predictable future when it comes to these types of things. Apparently, we have a few more moon that will be joining us relatively soon, so let’s hope none come too close for comfort.
Attn: Wayne Dupree is a free speech champion who works tirelessly to bring you news that the mainstream media ignores. But he needs your support in order to keep delivering quality, independent journalism. You can make a huge impact in the war against fake news by pledging as little as $5 per month. Please click here Patreon.com/WDShow to help Wayne battle the fake news media. | 0.842627 | 3.244727 |
I don't take this at face value because we should expect more distant
objects to have higher observed speeds and therefore higher observed
That's true. That was the original Hubble discovery - the farther away things were, the faster they were moving away from us.
Here's why. Let's start with a model where the Universe expanded very
fast early on, but has been slowing down ever since due to gravity, as
one would normally expect.
Yes - that's what everybody thought following Hubble's discovery.
Remember that, the farther away a cosmic object is, the farther back
in the past we are observing it. An object 1,000 light years away, if
it's light is reaching us now, is being observed in its state that
existed 1,000 years ago. We are effectively looking through a time
This is not lost on Astrophysicists.
So if we observe a more distant object, we're observing an older state
of that object. Therefore, we are observing it at a time when the
Universe was expanding faster than it is now, so it has higher
OK, 2 points. 2nd point first. The red-shift has to do with relative velocity, not speeding up or slowing down. Something can be more red-shifted and slowing down and something can be less red-shifted and speeding up, especially since the acceleration/deceleration is comparatively slow compared to the relative velocity.
and other point - lets keep in mind, we don't know what a galaxy 3 billion light years away is doing now. We can guess and we can run models, but we can only see what it's doing 3 billion years ago.
And isn't that what we observe today? The more distant the galaxy, the
higher its red-shift? This is not inconsistent with a "normal" model
where the expansion is slowing down due to gravity.
Yes, the more distant the galaxy the higher it's red-shift. But no, that's not inconsistent with expansion. That's what you'd see, expansion or contraction, because red-shift is just relative velocity.
What am I missing? Why are scientists trying to explain such things
with weird dark matter and dark energy that otherwise have never been
detected or found evidence of and aren't needed for any other model,
and in fact get in the way of our models of physics and quantum
A lot of these ideas are confusing. They're confusing to scientists too, especially when they were first discovered - so you're not alone.
Dark matter was observed because galaxies were behaving strangely. The stars in the outer arms of the galaxy were observed to be moving much too fast and faster than the stars more towards the middle of the galaxy and that made no sense. The galaxies also weighed too much and the only way to explain this was extra mass in kind of a halo around the galaxy, but this extra mass, also, didn't interact with electromagnetic waves like the mass here on earth does - so they called this extra mass (and there's a lot of it, more than there is regular mass), but since it's invisible, they called it "dark matter" and it's not dark like dirt or coal, it's dark as in - invisible. It's completely transparent to light, but it has mass and they still don't know what it is. They have some OK theories, but nothing definite.
Now, dark energy - think about the big bang and all matter flying apart - the galaxies twice as far are moving away twice as fast, BUT, as you said, because of gravity, we should see the galaxies that are twice as far moving away more than twice as fast, cause the nearer the galaxy, the more time it's had to slow down - aha, they thought, if we can compare the speed of the galaxies 4 billion light years away to the speed of the galaxies 2 billion light years away to the speed 1 billion light years - etc, etc and measure it all carefully, we can measure the rate at which gravity is slowing down the universe. - that makes sense right.
And with careful measurement of Type 1A supernovas, which temporarily outshine entire galaxies - with remarkable consistency (what they call a standard candle - a very bright standard candle, but a standard candle all the same) - with that, they thought they could measure the gravitational slow down of expansion - exactly what you're talking about.
The problem was, the measurements told them the opposite of what they expected to find. The measurements told them that the galaxies 2 billion light years away were traveling slightly more than half as fast as the galaxies 4 billion light years away, and so on. They checked this, cause it had to be wrong, then they re-checked it, and re-checked again and the only conclusion was, stuff out there is speeding up, not slowing down - cause that's what the telescopes tell us.
Dark energy wasn't a hair-brained scheme that mad scientists thunk up. It was an observed reality that nobody expected (well, cept just maybe for Einstein and his cosmological constant, but that's another story).
Dark energy's just a name anyway. They have to call it something, even if they're not sure what it is or how it works. | 0.820736 | 3.734296 |
- Awareness in space.
NASA’s Kepler Space telescope
What to study?
- For Prelims: About Kepler telescope, TESS.
- For Mains: What are exoplanets, significance of their findings.
Context: Scientists have discovered a cache over 100 new exoplanets using data from NASA’s Kepler Space telescope as well as ground-based observatories. The diverse planets are expected to play a large role in developing the research field of exoplanets and life in the Universe.
The Kepler Space Telescope has been officially retired by NASA. Its successor space telescope, called TESS, has already started collecting data.
About Kepler Mission:
Launched in 2009, the Kepler mission is specifically designed to survey our region of the Milky Way galaxy to discover hundreds of Earth-sized and smaller planets in or near the habitable zone and determine the fraction of the hundreds of billions of stars in our galaxy that might have such planets.
About TESS mission:
- The Transiting Exoplanet Survey Satellite (TESS) is a NASA mission that will look for planets orbiting the brightest stars in Earth’s sky. It was led by the Massachusetts Institute of Technology with seed funding from Google.
- Mission: The mission will monitor at least 200,000 stars for signs of exoplanets, ranging from Earth-sized rocky worlds to huge gas giant planets. TESS, however, will focus on stars that are 30 to 100 times brighter than those Kepler examined. This will help astronomers better understand the structure of solar systems outside of our Earth, and provide insights into how our own solar system formed.
- Orbit: TESS will occupy a never-before-used orbit high above Earth. The elliptical orbit, called P/2, is exactly half of the moon’s orbital period; this means that TESS will orbit Earth every 13.7 days.
- How it works? It will use transit method to detect exoplanets. It watches distant stars for small dips in brightness, which can indicate that planet has passed in front of them. Repeated dips will indicate planet passing in front of its star. This data has to be validated by repeated observations and verified by scientists.
Sources: the hindu. | 0.895572 | 3.294832 |
Delta Circini (δ Cir), is a multiple star system located in the constellation Circinus. Delta Circini is also known as HR 5664, and HD 135240. The system has a combined apparent visual magnitude of +5.09, and is located at a distance of 770 pc (2,500ly) from the Sun.
δ Circini B is a 13th magnitude companion nearly an arc-second away. It is unclear whether the two are physically associated and little is known about the fainter star although it has been reported to be a G5 main sequence star or giant.
HD 135160 is a 6th magnitude binary Be star that shares a common space motion with δ Circini and is only 4 arc minutes away. The two make a faint naked eye pair.
All three components of δ Circini A are hot luminous stars. The brightest is an O8 star just beginning to evolve away from the main sequence. It is in a very close orbit with an O9.5 main sequence star. The two stars are deformed into ellipsoidal shapes and eclipse each other every 3.9 days. The total brightness change is only 0.15 magnitudes.
The third component is a B0.5 main sequence star in a long eccentric orbit around the close pair. It is fainter and cooler than either of the two close stars, yet it is calculated to be more massive than δ Cir A, so it is suspected that it may also be a close binary system.
- Mayer, Pavel; Harmanec, Petr; Sana, Hugues; Le Bouquin, Jean-Baptiste (2014). "The Three-body System δ Circini". The Astronomical Journal 148 (6): 114. doi:10.1088/0004-6256/148/6/114. Bibcode: 2014AJ....148..114M.
- Lindroos, K. P. (1985). "A study of visual double stars with early type primaries. IV Astrophysical data". Astronomy and Astrophysics Supplement Series 60: 183. Bibcode: 1985A&AS...60..183L.
- "del Cir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=del+Cir.
- Delta Circini on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
https://en.wikipedia.org/wiki/Delta Circini was the original source. Read more. | 0.900128 | 3.63257 |
An evanescent shell of glowing gas spreading into space — the planetary nebula ESO 577-24 — dominates this image. This planetary nebula is the remains of a dead giant star that has thrown off its outer layers, leaving behind a small, intensely hot dwarf star. This diminished remnant will gradually cool and fade, living out its days as the mere ghost of a once-vast red giant star.
Red giants are stars at the end of their lives that have exhausted the hydrogen fuel in their cores and begun to contract under the crushing grip of gravity. As a red giant shrinks, the immense pressure reignites the core of the star, causing it to throw its outer layers into the void as a powerful stellar wind. The dying star’s incandescent core emits ultraviolet radiation intense enough to ionize these ejected layers and cause them to shine. The result is what we see as a planetary nebula — a final, fleeting testament to an ancient star at the end of its life.
This dazzling planetary nebula was discovered as part of the National Geographic Society — Palomar Observatory Sky Survey in the 1950s, and was recorded in the Abell Catalogue of Planetary Nebulae in 1966. At around 1400 light years from Earth, the ghostly glow of ESO 577-24 is only visible through a powerful telescope. As the dwarf star cools, the nebula will continue to expand into space, slowly fading from view.
This image of ESO 577-24 was created as part of the ESO Cosmic Gems Programme, an initiative that produces images of interesting, intriguing, or visually attractive objects using ESO telescopes for the purposes of education and public outreach. The program makes use of telescope time that cannot be used for scientific observations; nevertheless, the data collected are made available to astronomers through the ESO Science Archive. | 0.891231 | 3.526218 |
Norwegian researchers are looking into how a snake robot might carry out maintenance work on the International Space Station (ISS), study comets, and explore the possibility of living and working in lava tunnels on the Moon.
Three years ago SINTEF was investigating whether snake robots could help astronauts working on Mars with mobility and access. As part of a project commissioned by the ESA, researchers are to continue with this work and are carrying out a preliminary study to examine the technology and other opportunities for utilising robots in space.
“More ambitious applications include potential activities on comets and the Moon”, says Aksel Transeth at SINTEF. Snake robot" that can assist ISS astronauts in maintaining their equipment is perhaps a solution which can be possible to realize on a more short term."
It is almost 50 years since the first men walked on the surface of the moon. The ESA believes that humanity’s next great step may be a joint global project aimed at establishing a settlement on the Moon – a “moon village”. Such a settlement could provide a permanent base for scientific activity, business, tourism or mining, and the most likely place for such a base will be in lava tubes, or tunnels, where molten rock once flowed.
Building in lava tubes will mean that settlers will be protected from harmful exposure to cosmic radiation and meteorites.
However, such tunnels must be inspected to ensure that it is possible for people to live and work in them, and this is where the snake robots may have a role to play. The force of gravity is weaker on the Moon. Moreover, lava tubes may drop vertically from the surface. So how will it be possible to facilitate access and mobility?
The ESA is also interested in studying comets. Since comets come from the far reaches of outer space, researchers are hoping to uncover some of the mysteries of the solar system, and to obtain help in forming a picture of what it looked like before the planets were formed.
In 2004, the ESA launched the Rosetta space probe, and in 2014 the probe released the Philae lander onto the comet 67P/Tsjurjumov–Gerasimenko. The lander was equipped with a system of harpoons designed to hold it in place on landing. Unfortunately, this failed to work.
“There is pretty much no gravity on a comet”, says Transeth. “If you try to walk on the surface, you could be thrown into space”, he says. “So we have to find ways in which snake robots can move around on a comet while at the same time keeping themselves fixed on the surface”, says Transeth.
Inspection and maintenance on the ISS
But for today’s SINTEF researchers, it’s the snake robots on the ISS that represent their most natural and realistic project on shorter term. There are no problems with extreme temperatures on the ISS, which is occupied at all times.
Astronauts carry out experiments sent to them in boxes by their colleagues on Earth, and these experiments have to be carried out in a state of weightlessness. For example, what plants can grow in space? How do wounds heal in such surroundings?
These are the astronauts’ main tasks, but they also have their work cut out inspecting and maintaining all the equipment needed to keep the space station in operation. Anything that saves them time during their hectic schedule is worth its weight in gold.
“It’s possible that a robot could carry out some of the routine inspection and maintenance work”, says Transeth. “The experiments are stacked in the shelf sections, behind which corrosion can occur. To find this out, inspections have to be made. A snake robot could creep behind the sections, carry out an inspection, and perhaps even perform small maintenance tasks”, he says.
Rolls up, creeps and extends
There is no shortage of challenges facing researchers attempting to develop an inspection and maintenance snake robot system. One important factor is to find out how a snake robot can make its way around the ISS. Since the ISS is in a constant state of freefall around the earth, astronauts “float” around the station, moving around by grabbing onto things and then pushing themselves off.
“We believe that we can design a robot that can hold on, roll itself up and then extend its body in order to reach new contact points”, explains Transeth. “Moreover, we believe that it can creep in among equipment components on the ISS and use equipment surfaces to gain traction in order to keep moving forward – much in the same way as real snakes do in the wild”, he says.
“We want to find out what specifications a snake robot system requires”, he adds. “For example, what kind of sensors does the robot need to obtain an adequate understand its surroundings? What technologies are available to help us meet these needs, and what new technologies will have to be developed? What uncertainties are involved in terms to what it may be possible to achieve?” asks Transeth.
A drone called Astrobee will soon be flying around and making inspections on the ISS. The researchers believe that they can learn a lot from Astrobee because some of its technology will be similar to that which can be applied in a snake robot system. | 0.86924 | 3.047053 |
For still or motion photography, delivering a bright, clean light source for a wide variety of subjects. Buff is compact, light weight unit capable of shouldering studio work yet portable enough to take on . Einstein was fascinated by the nature of light. It explores how scientific imagination and innovation . In this video, we discuss the features of the unit.
His radical insight into the nature of light.
The speed of light in a vacuum is considered to be one of the fundamental constants of nature. I always wondered why on earth someone would pay tens of thousands for “the best” lighting out there when the same could be accomplished . Why are some scientists world-famous but not others? Astronomers used the Hubble Space Telescope to measure the mass of a nearby white dwarf, as it bent the light of a . LENS-LIKE ACTION OF A STAR BY THE DEVIATION OF LIGHT IN THE GRAVITATIONAL FIELD.
See allHide authors and affiliations. Theories of the deflection of light by mass date back at least to the late 18th century. At that time, the Reverend John Michell, an English clergyman and natural .
For the first time ever, astronomers have seen a distant star warp the light of another star, making it seem as though the object changed its . When light strikes a glass prism, we get both refraction and reflection. The mineral mica can be split into extremely thin sheets, each quite clear and . The questions here span a range of difficulty. If you can answer them all, you have.
The perfect circle surrounding a galaxy cluster in a new Hubble Space Telescope image is a visual indicator of the huge masses that are . People had observed gravitational . The stronger the force of gravity, the more the light would be bent. It has an incredible toy bar that . Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the . Lights on for the right tower. A new theory suggests that the speed of light was not always constant, which could shake up physics as we know it. An experiment showing it is possible to travel faster than the speed of light , and so confound a fundamental principle of theoretical physics, has . A new study confirms a theory that the great man of physics never much liked. Rotating black holes could leave a twisty signature on light.
According to the general theory . He explained the interaction between light and.
At the middle of the image, you can see two bright lights —this is . Now baby can rock out to classical melodies with this adorable guitar! Bay Area scientists announced today that they had seen the fireball cast off by colliding neutron stars 1million light -years away, a landmark . The eclipse presented a rare chance to verify one of the essential consequences of general relativity, the bending of light by gravity. | 0.876318 | 3.238967 |
Solar Orbiter is on its way
A rocket carrying Solar Orbiter, a probe that will take pictures of the top and bottom of the sun, launched Sunday night. The Atlas 5 rocket launched on time, just as the final Oscar statues were being handed out for the 2020 Academy Awards. It illuminated the night sky over Florida’s Atlantic coast as it headed away from Earth to place thespacecraft into an orbit around the sun.
It was a successful beginning to a mission that is a collaboration between NASA and the European Space Agency. In the day ahead, Solar Orbiter will test its instruments and prepare to initiate the complex maneuvers it needs to set course for what scientists hope is a decade of solar discoveries.
A new view of the sun
With Solar Orbiter, scientists will for the first time get a good view of the top and bottom of the sun. Until now, almost all of the solar-watching spacecraft have orbited in the ecliptic, or the same plane that the planets travel around the sun.
That change of view could help solve mysteries about how the sun spews high-velocity charged particles that fly outward through the solar system and buffet the planets, including Earth. The magnetic fields that accelerate those particles flow into and out of the sun’s poles. The data from Solar Orbiter could help explain the sunspot cycle — Why does the cycle last 11 years? Why are some quiet and others roar violently? — and help models to predict solar storms that could disrupt Earth’s power grids and satellites in orbit.
Ulysses, an earlier collaboration between NASA and the European Space Agency launched in 1990, also passed over the sun’s poles, but at much farther distances, and it did not carry a camera.
A long and winding journey
The launch trajectory will take Solar Orbiter away from Earth into an orbit around the sun. A flyby of Venus on the day after Christmas will sap some of its energy and let it spiral closer toward the sun.
Additional flybys — one of Earth, two more of Venus — will further adjust the orbit, which will still be in the ecliptic, the plane of the orbits.
A flyby of Venus in 2025 will swing Solar Orbiter out of the ecliptic to an angle of 17 degrees. That is enough to get a good glimpse of the polar regions. Additional Venus flybys will increase the angle to 33 degrees.
The mission is expected to complete 22 orbits of the sun in 10 years.
Solar Orbiter’s instruments
The spacecraft’s 10 scientific instruments are a mix. Some measure what is happening directly around the spacecraft, like the magnetic fields and particles of the solar wind. Others take pictures of what is occurring on the sun.
Remember the caution that you should not look directly at the sun? Solar Orbiter’s cameras have to do just that, and at a distance where the sunlight is 13 times as intense. Three peepholes in the heat shield will open for 10 days at a time to allow the instruments to collect data. The assorted cameras also have heat-resistant windows (think of them as scientific sunglasses) as protection.
The cameras will look at a range of wavelengths of light, including ultraviolet and X-rays. Some of the cameras break the light into separate wavelengths to identify specific molecules. The coronagraph includes a disk to block out most of the light to look at what is going on in the sun’s outer atmosphere.
Magnetic fields and solar storms
Occasionally, the sun erupts giant amounts of particles known as coronal mass ejections. When such an eruption slams into Earth’s magnetic field, it generates surges of electrical current.
Solar scientists do not have reliable ways to predict such an eruption. The largest one known to hit Earth was the Carrington event in 1859, named after one of the people who observed an intensely bright spot on the sun where the eruption occurred. The surge caused some telegraph wires to catch fire.
When Nicola J. Fox, director of NASA’s heliophysics division, talks about solar science to children at schools she introduces the Carrington event and how it knocked out the telegraph system in the U.S. for four days.
“The kids just kind of look at me like, ‘So what?’,” she said. “And then I say, ‘Imagine you didn’t have your iPad for four days.’ Panic ensues in the classroom.”
A similar event today could potentially cause not only continentwide blackouts, but also destroy giant transformers on the electric grid — damage that might take months or years to repair.
A smaller solar storm in March 1989 knocked out power in Quebec for nine hours.
Just a few years ago, Earth was lucky.
On July 23, 2012, NASA’s Stereo-A spacecraft was hit by a gigantic coronal mass ejection. Analysis showed that this outburst was bigger than the Carrington eruption. If Earth had been where Stereo-A was — the spacecraft travels in the same orbit as Earth, but ahead of the planet — that would have been a very interesting day.
A partnership with Parker Solar Probe
In 2018, NASA launched the Parker Solar Probe, which is making closer and closer flybys of the sun as it reaches the fastest speeds ever achieved by a human-built spacecraft. That probe is flying into the sun’s outer atmosphere, known as the corona, and eventually coming within four million miles of its surface. By comparison, Earth is 93 million miles from the sun. Mercury, the closest planet, is 29 million miles from the sun.
The close distance allows the Parker Solar Probe to make direct measurements of those regions, but it has to be protected from temperatures of about 2 million degrees Fahrenheit.
Solar Orbiter will be passing farther from the sun. At the closest point along its elliptical orbit, it will be just three million miles inside of the orbit of Mercury, and experience much less extreme temperatures. Instead of millions of degrees, temperatures at Solar Orbiter will reach several hundred degrees. That allows Solar Orbiter to carry a wider range of instruments.
Coordinated observations between Parker and Solar Orbiter could identify phenomena on the surface with conditions in the corona.
“It’s really a perfect dream, a marriage in heaven,” said Guenther Hasinger, director of science at European Space Agency during a news conference on Friday.
A fleet of sun watchers
In addition to Solar Orbiter and Parker Solar Probe, nine other missions are currently keeping an eye on the sun and the solar wind. Each has been designed to add unique data to our understanding of what our star is doing.
Here is what else is out there:
Advanced Composition Explorer, or ACE — A NASA spacecraft that monitors the solar wind from a vantage point between Earth and the sun.
Cluster — Four European Space Agency Earth-orbiting spacecraft investigating the interactions of the solar wind with Earth’s magnetic field.
Hinode — A Japanese spacecraft measuring the sun’s magnetic fields.
Interface Region Imaging Spectrograph, or IRIS — A small NASA ultraviolet telescope in orbit around Earth that studies the movement of heat and energy in the lower parts of the sun’s atmosphere.
Proba-2 — Two instruments on this low-cost European Space Agency satellite observe the sun.
Solar Terrestrial Relations Observatory, or Stereo — A NASA mission of two nearly identical spacecraft traveling around the sun in the same orbit as Earth, with one ahead of Earth and one trailing.
Solar Dynamics Observatory, or S.D.O. — A NASA spacecraft in geosynchronous orbit that studies the influence of the sun and solar weather on Earth.
Solar and Heliospheric Observatory, or SOHO — An earlier European-NASA collaboration that has been taking pictures of the sun since 1995.
Wind — A NASA spacecraft observing heated gas of charged particles coming from the sun.
European spacecraft, American rocket
Many big space missions are international collaborations. For Solar Orbiter, the European Space Agency was in charge of developing the spacecraft and its instruments. NASA paid for the Atlas 5 rocket for the trip to space.
The James Webb Space Telescope, the successor to the Hubble Space Telescope, is the opposite. NASA is building the telescope, and the Europeans are providing the launch vehicle, an Ariane 5 rocket from French Guiana.
The Rosalind Franklin rover that is to launch to Mars this summer was originally another NASA-European Space Agency collaboration but NASA backed out in 2012, because of cuts in the NASA budget. The Europeans turned to Russia to provide the rocket and the system to land the rover on the surface.
A slightly less busy rocket day
Solar Orbiter was not the only spacecraft scheduled to be launched from the East Coast on Sunday. A crewless Antares cargo ship with supplies, equipment and experiments destined for International Space Station was to lift off at 5:39 p.m. Eastern time from the Mid-Atlantic Regional Spaceport in Virginia. However, after a short postponement, Sunday’s launch was called off.
Northrop Grumman, which manages the Antares and Cygnus flights, described a problem with a sensor on the ground. It said it will not be able to attempt a launch again until Thursday because of weather concerns as well as time needed to address the problem that caused the scrubbed launch. | 0.842676 | 3.672095 |
Spherical coordinate system
In mathematics, a spherical coordinate system is a coordinate system for three-dimensional space where the position of a point is specified by three numbers: the radial distance of that point from a fixed origin, its polar angle measured from a fixed zenith direction, and the azimuthal angle of its orthogonal projection on a reference plane that passes through the origin and is orthogonal to the zenith, measured from a fixed reference direction on that plane. It can be seen as the three-dimensional version of the polar coordinate system.
The radial distance is also called the radius or radial coordinate. The polar angle may be called colatitude, zenith angle, normal angle, or inclination angle.
The use of symbols and the order of the coordinates differs among sources and disciplines. This article will use the ISO convention frequently encountered in physics: gives the radial distance, polar angle, and azimuthal angle. In many mathematics books, or gives the radial distance, azimuthal angle, and polar angle, switching the meanings of θ and φ. Other conventions are also used, such as r for radius from the z-axis, so great care needs to be taken to check the meaning of the symbols.
According to the conventions of geographical coordinate systems, positions are measured by latitude, longitude, and height (altitude). There are a number of celestial coordinate systems based on different fundamental planes and with different terms for the various coordinates. The spherical coordinate systems used in mathematics normally use radians rather than degrees and measure the azimuthal angle counterclockwise from the x-axis to the y-axis rather than clockwise from north (0°) to east (+90°) like the horizontal coordinate system. The polar angle is often replaced by the elevation angle measured from the reference plane, so that the elevation angle of zero is at the horizon.
The spherical coordinate system generalizes the two-dimensional polar coordinate system. It can also be extended to higher-dimensional spaces and is then referred to as a hyperspherical coordinate system.
To define a spherical coordinate system, one must choose two orthogonal directions, the zenith and the azimuth reference, and an origin point in space. These choices determine a reference plane that contains the origin and is perpendicular to the zenith. The spherical coordinates of a point P are then defined as follows:
- The radius or radial distance is the Euclidean distance from the origin O to P.
- The inclination (or polar angle) is the angle between the zenith direction and the line segment OP.
- The azimuth (or azimuthal angle) is the signed angle measured from the azimuth reference direction to the orthogonal projection of the line segment OP on the reference plane.
The sign of the azimuth is determined by choosing what is a positive sense of turning about the zenith. This choice is arbitrary, and is part of the coordinate system's definition.
The elevation angle is 90 degrees (π/ radians) minus the inclination angle.
If the inclination is zero or 180 degrees (π radians), the azimuth is arbitrary. If the radius is zero, both azimuth and inclination are arbitrary.
Several different conventions exist for representing the three coordinates, and for the order in which they should be written. The use of to denote radial distance, inclination (or elevation), and azimuth, respectively, is common practice in physics, and is specified by ISO standard 80000-2:2009, and earlier in ISO 31-11 (1992).
However, some authors (including mathematicians) use ρ for radial distance, φ for inclination (or elevation) and θ for azimuth, and r for radius from the z-axis, which "provides a logical extension of the usual polar coordinates notation". Some authors may also list the azimuth before the inclination (or elevation). Some combinations of these choices result in a left-handed coordinate system. The standard convention conflicts with the usual notation for two-dimensional polar coordinates and three-dimensional cylindrical coordinates, where θ is often used for the azimuth.
The angles are typically measured in degrees (°) or radians (rad), where 360° = 2π rad. Degrees are most common in geography, astronomy, and engineering, whereas radians are commonly used in mathematics and theoretical physics. The unit for radial distance is usually determined by the context.
When the system is used for physical three-space, it is customary to use positive sign for azimuth angles that are measured in the counter-clockwise sense from the reference direction on the reference plane, as seen from the zenith side of the plane. This convention is used, in particular, for geographical coordinates, where the "zenith" direction is north and positive azimuth (longitude) angles are measured eastwards from some prime meridian.
Major conventions coordinates corresponding local geographical directions
(Z, X, Y)
right/left-handed (r, θinc, φaz,right) (U, S, E) right (r, φaz,right, θel) (U, E, N) right (r, θel, φaz,right) (U, N, E) left
Any spherical coordinate triplet specifies a single point of three-dimensional space. On the other hand, every point has infinitely many equivalent spherical coordinates. One can add or subtract any number of full turns to either angular measure without changing the angles themselves, and therefore without changing the point. It is also convenient, in many contexts, to allow negative radial distances, with the convention that is equivalent to for any r, θ, and φ. Moreover, is equivalent to .
If it is necessary to define a unique set of spherical coordinates for each point, one must restrict their ranges. A common choice is
- r ≥ 0,
- 0° ≤ θ ≤ 180° (π rad),
- 0° ≤ φ < 360° (2π rad).
However, the azimuth φ is often restricted to the interval (−180°, +180°], or (−π, +π] in radians, instead of [0, 360°). This is the standard convention for geographic longitude.
The range [0°, 180°] for inclination is equivalent to [−90°, +90°] for elevation (latitude).
Even with these restrictions, if θ is 0° or 180° (elevation is 90° or −90°) then the azimuth angle is arbitrary; and if r is zero, both azimuth and inclination/elevation are arbitrary. To make the coordinates unique, one can use the convention that in these cases the arbitrary coordinates are zero.
To plot a dot from its spherical coordinates (r, θ, φ), where θ is inclination, move r units from the origin in the zenith direction, rotate by θ about the origin towards the azimuth reference direction, and rotate by φ about the zenith in the proper direction.
The geographic coordinate system uses the azimuth and elevation of the spherical coordinate system to express locations on Earth, calling them respectively longitude and latitude. Just as the two-dimensional Cartesian coordinate system is useful on the plane, a two-dimensional spherical coordinate system is useful on the surface of a sphere. In this system, the sphere is taken as a unit sphere, so the radius is unity and can generally be ignored. This simplification can also be very useful when dealing with objects such as rotational matrices.
Spherical coordinates are useful in analyzing systems that have some degree of symmetry about a point, such as volume integrals inside a sphere, the potential energy field surrounding a concentrated mass or charge, or global weather simulation in a planet's atmosphere. A sphere that has the Cartesian equation x2 + y2 + z2 = c2 has the simple equation r = c in spherical coordinates.
Two important partial differential equations that arise in many physical problems, Laplace's equation and the Helmholtz equation, allow a separation of variables in spherical coordinates. The angular portions of the solutions to such equations take the form of spherical harmonics.
Another application is ergonomic design, where r is the arm length of a stationary person and the angles describe the direction of the arm as it reaches out.
Three dimensional modeling of loudspeaker output patterns can be used to predict their performance. A number of polar plots are required, taken at a wide selection of frequencies, as the pattern changes greatly with frequency. Polar plots help to show that many loudspeakers tend toward omnidirectionality at lower frequencies.
The spherical coordinate system is also commonly used in 3D game development to rotate the camera around the player's position.
To a first approximation, the geographic coordinate system uses elevation angle (latitude) in degrees north of the equator plane, in the range −90° ≤ φ ≤ 90°, instead of inclination. Latitude is either geocentric latitude, measured at the Earth's center and designated variously by ψ, q, φ′, φc, φg or geodetic latitude, measured by the observer's local vertical, and commonly designated φ. The azimuth angle (longitude), commonly denoted by λ, is measured in degrees east or west from some conventional reference meridian (most commonly the IERS Reference Meridian), so its domain is −180° ≤ λ ≤ 180°. For positions on the Earth or other solid celestial body, the reference plane is usually taken to be the plane perpendicular to the axis of rotation.
The polar angle, which is 90° minus the latitude and ranges from 0 to 180°, is called colatitude in geography.
Instead of the radial distance, geographers commonly use altitude above or below some reference surface, which may be the sea level or "mean" surface level for planets without liquid oceans. The radial distance r can be computed from the altitude by adding the mean radius of the planet's reference surface, which is approximately 6,360 ± 11 km (3,952 ± 7 miles) for Earth.
However, modern geographical coordinate systems are quite complex, and the positions implied by these simple formulae may be wrong by several kilometers. The precise standard meanings of latitude, longitude and altitude are currently defined by the World Geodetic System (WGS), and take into account the flattening of the Earth at the poles (about 21 km or 13 miles) and many other details.
In astronomy there are a series of spherical coordinate systems that measure the elevation angle from different fundamental planes. These reference planes are the observer's horizon, the celestial equator (defined by Earth's rotation), the plane of the ecliptic (defined by Earth's orbit around the Sun), the plane of the earth terminator (normal to the instantaneous direction to the Sun), and the galactic equator (defined by the rotation of the Milky Way).
Coordinate system conversions
As the spherical coordinate system is only one of many three-dimensional coordinate systems, there exist equations for converting coordinates between the spherical coordinate system and others.
The spherical coordinates of a point in the ISO convention (i.e. for physics: radius r, inclination θ, azimuth φ) can be obtained from its Cartesian coordinates (x, y, z) by the formulae
The inverse tangent denoted in φ = arctan y/ must be suitably defined, taking into account the correct quadrant of (x, y). See the article on atan2.
Alternatively, the conversion can be considered as two sequential rectangular to polar conversions: the first in the Cartesian xy plane from (x, y) to (R, φ), where R is the projection of r onto the xy-plane, and the second in the Cartesian zR-plane from (z, R) to (r, θ). The correct quadrants for φ and θ are implied by the correctness of the planar rectangular to polar conversions.
These formulae assume that the two systems have the same origin, that the spherical reference plane is the Cartesian xy plane, that θ is inclination from the z direction, and that the azimuth angles are measured from the Cartesian x axis (so that the y axis has φ = +90°). If θ measures elevation from the reference plane instead of inclination from the zenith the arccos above becomes an arcsin, and the cos θ and sin θ below become switched.
Conversely, the Cartesian coordinates may be retrieved from the spherical coordinates (radius r, inclination θ, azimuth φ), where r ∈ [0, ∞), θ ∈ [0, π], φ ∈ [0, 2π), by
Cylindrical coordinates (axial radius ρ, azimuth φ, elevation z) may be converted into spherical coordinates (central radius r, inclination θ, azimuth φ), by the formulas
Conversely, the spherical coordinates may be converted into cylindrical coordinates by the formulae
These formulae assume that the two systems have the same origin and same reference plane, measure the azimuth angle φ in the same senses from the same axis, and that the spherical angle θ is inclination from the cylindrical z axis.
Modified spherical coordinates
It is also possible to deal with ellipsoids in Cartesian coordinates by using a modified version of the spherical coordinates.
Let P be an ellipsoid specified by the level set
The modified spherical coordinates of a point in P in the ISO convention (i.e. for physics: radius r, inclination θ, azimuth φ) can be obtained from its Cartesian coordinates (x, y, z) by the formulae
An infinitesimal volume element is given by
The square-root factor comes from the property of the determinant that allows a constant to be pulled out from a column:
Integration and differentiation in spherical coordinates
The following equations (Iyanaga 1977) assume that the colatitude θ is the inclination from the z (polar) axis (ambiguous since x, y, and z are mutually normal), as in the physics convention discussed.
The line element for an infinitesimal displacement from (r, θ, φ) to (r + dr, θ + dθ, φ + dφ) is
are the local orthogonal unit vectors in the directions of increasing r, θ, and φ, respectively, and x̂, ŷ, and ẑ are the unit vectors in Cartesian coordinates. The linear transformation to this right-handed coordinate triplet is a rotation matrix,
The general form of the formula to prove the differential line element, is
that is, the change in is decomposed into individual changes corresponding to changes in the individual coordinates.
To apply this to the present case, one needs calculate how changes with each of the coordinates. In the conventions used,
The desired coefficients are the magnitudes of these vectors:
The surface element spanning from θ to θ + dθ and φ to φ + dφ on a spherical surface at (constant) radius r is then
Thus the differential solid angle is
The surface element in a surface of polar angle θ constant (a cone with vertex the origin) is
The surface element in a surface of azimuth φ constant (a vertical half-plane) is
Thus, for example, a function f(r, θ, φ) can be integrated over every point in ℝ3 by the triple integral
Further, the inverse Jacobian in Cartesian coordinates is
The metric tensor in the spherical coordinate system is .
Distance in Spherical Coordinates
In spherical coordinates, given 2 points with φ being the azimuthal coordinate
The distance between the two points can be expressed as
In spherical coordinates, the position of a point is written as
Its velocity is then
and its acceleration is
The angular momentum is
In the case of a constant φ or else θ = π/, this reduces to vector calculus in polar coordinates.
- Celestial coordinate system
- Coordinate system
- Del in cylindrical and spherical coordinates
- Elevation (ballistics)
- Euler angles
- Gimbal lock
- Jacobian matrix and determinant
- List of canonical coordinate transformations
- Spherical harmonic
- Vector fields in cylindrical and spherical coordinates
- Yaw, pitch, and roll
- Duffett-Smith, P and Zwart, J, p. 34.
- Eric W. Weisstein (2005-10-26). "Spherical Coordinates". MathWorld. Retrieved 2010-01-15.
- "Line element (dl) in spherical coordinates derivation/diagram". Stack Exchange. October 21, 2011.
- Iyanaga, Shōkichi; Kawada, Yukiyosi (1977). Encyclopedic Dictionary of Mathematics. MIT Press. ISBN 978-0262090162.
- Morse PM, Feshbach H (1953). Methods of Theoretical Physics, Part I. New York: McGraw-Hill. p. 658. ISBN 0-07-043316-X. LCCN 52011515.
- Margenau H, Murphy GM (1956). The Mathematics of Physics and Chemistry. New York: D. van Nostrand. pp. 177–178. LCCN 55010911.
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- Sauer R, Szabó I (1967). Mathematische Hilfsmittel des Ingenieurs. New York: Springer Verlag. pp. 95–96. LCCN 67025285.
- Moon P, Spencer DE (1988). "Spherical Coordinates (r, θ, ψ)". Field Theory Handbook, Including Coordinate Systems, Differential Equations, and Their Solutions (corrected 2nd ed., 3rd print ed.). New York: Springer-Verlag. pp. 24–27 (Table 1.05). ISBN 978-0-387-18430-2.
- Duffett-Smith P, Zwart J (2011). Practical Astronomy with your Calculator or Spreadsheet, 4th Edition. New York: Cambridge University Press. p. 34. ISBN 978-0521146548.
- Hazewinkel, Michiel, ed. (2001) , "Spherical coordinates", Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4
- MathWorld description of spherical coordinates
- Coordinate Converter — converts between polar, Cartesian and spherical coordinates | 0.81944 | 3.263476 |
Dr. Alexander Kashlinsky is a principal investigator on several NASA and NSF grants studying topics related to cosmological bulk flows, cosmic microwave and infrared background radiation, and early stellar populations. Using the Wilkinson Microwave Anisotropy Probe, Kashlinsky recently discovered a phenomenon called “dark flow,” which are clusters of galaxies moving at a constant velocity toward a 20-degree patch of sky between the constellations of Centaurus and Vella.
NASA Tech Briefs: You have a PhD in astrophysics from Cambridge University in England and your area of expertise at NASA is observational cosmology. What prompted you to pursue a career in this field?
Dr. Alexander Kashlinsky: It actually started in my youth from reading too much science fiction, which I no longer do. I distinctly remember how it was triggered. I picked up a book from the shelf by Stanislaw Lem, called the “Magellanic Cloud,” which was about the first interstellar travel, and it conquered my mind at the time, but I ended up in astrophysics and not traveling to the stars. Later, when I was doing my PhD, I was very privileged to work with Martin Rees, who is a very inspirational scientist, and that triggered my interest in astronomy and particularly in cosmology. He was very open-minded, and very interested in completely different ideas, which I found very stimulating and very inspiring. The rest is history.
NTB: Several years ago you were part of a team that succeeded in isolating the energy radiated by the first stars formed after the Big Bang, called Population 3, from all other energy that makes up the cosmic infrared background. What did you learn from that breakthrough?
Kashlinsky: What we did at the time was, we analyzed very deep data available thanks to the Spitzer Infrared Telescope, and we were trying to find how much diffuse radiation is left after we removed the various contributions that we can isolate in the images. What we learned is that the residual diffuse background – the so-called cosmic infrared background radiation – has quite a bit of energy emitted from sources that are much too faint to be detected, even in deep Spitzer exposures. That most likely means that these sources are very far away, because we removed galaxies down to a very faint level, that is, very far away. They had very little time to radiate all this very substantial energy that we detected and, therefore, they had to be quite abundant and they had to be radiating at enormous rates compared to typical populations living today. That, in our opinion, meant these populations were dominated by very massive stars, or very massive black holes, that lived very short times, but each unit of their mass emitted so much more energy than present day stars – such as the sun – that they had to produce this signature.
What is important in this context is not only what we learned, but what we did not learn. With the current data we could not learn whether these sources were stars that emit their energy by converting hydrogen into helium, or they were massive black holes that existed in very early times and that emitted energy by accretion processes, by gas falling into them and emitting energy in the process.
NTB: More recently, using NASA’s Wilkinson Microwave Anisotropy Probe, you discovered a phenomenon you refer to as “dark flow.” What is dark flow?
Kashlinsky: What we set out to measure in that measurement was the so-called peculiar velocities of clusters of galaxies, which are deviations from the uniform expansion of the universe. We never expected to find what we found at the end. We designed a method several years ago to probe the expected – within the standard cosmological models – peculiar velocities. The trick was to use many, many clusters of galaxies whereby you detect a very faint signal by beating down the noise. So we teamed up with colleagues at the University of Hawaii who assembled this x-ray cluster catalogue, and applied that method to the Wilkinson Microwave Anisotropy Probe, and we were very surprised by the results.
We found a flow that does not decrease with distance as far as we could tell, and we could probe to several billion light years away from us. It roughly was a constant amplitude, whereas in the standard cosmological model you expect that it should’ve been decreasing linearly with increasing scale. That is, as you go from, say, a few hundred-million light years to a few billion light years, it should decrease by an order of magnitude. We did not find that. We found a more or less constant velocity all the way as far as we can probe. The reason we called it dark flow is because the matter distribution in the observed universe, which is very well-known from galaxy surveys and from cosmic microwave background anisotropy measurements, that matter distribution cannot account for this motion. So this is why we suggested that if this motion already extends so far, then it probably goes all the way across the observable universe to the so-called cosmological horizon, and it is caused by the matter inhomogenity, or, I should say, space-time inhomogenity, at very large distances well beyond the cosmological horizon, which is about 40 billion light years away from us.
NTB: It’s been theorized that this dark flow may somehow be related to inflation, the brief hyper-expansion of the universe that occurred shortly after the Big Bang. Can you explain that relationship to us?
Kashlinsky: Yes. What we suspect is happening is the following. Inflation was designed, if I’m not mistaken in the early 1980s, to explain why the universe we see around us is homogeneous and isotropic. It is homogeneous – it’s roughly the same on all scales – and isotropic – it’s roughly the same in every direction.
Now, the way inflation works is as follows. It says that at some very early time the universe, or the underlying space-time, was not homogeneous. What happened then was that there was some bubble, a very tiny bubble of space-time, which, by pure chance, happened to be homogeneous by purely casual process, and then because of the various high-energy processes in the early universe this bubble, along with the rest of the space-time, expanded by a huge amount. We, today, live inside a tiny part of that original homogeneous bubble and we, therefore, see the universe around us as homogeneous and isotropic because the scales of inhomogenities that are other bubbles have been pushed away very, very far. What it means, at the same time, is that the original space-time was not homogeneous. If we go sufficiently far away, we should see the remnants of the pre-inflationary structure of the universe, of the space-time. These remnants would cause a very long wavelength wave across our universe and because there would be a gradient in this wave from one edge of the universe to the other, or from one edge of the cosmological horizon to the other, we would see a certain tilt, or the matter would be flowing from one edge to the other.
The analogy I could think of is as follows. Suppose you are in the middle of a very quiet ocean and you see the horizon, which determines how far you can see. As far as you can see, the ocean is isotropic and homogeneous. You would then think, at first, that the entire universe is just like what you see locally, that it’s homogeneous and isotropic like your own horizon. But then, inside that ocean, you discover a very faint stream from one edge of the horizon to the other...a flow. From the existence of that flow, you could deduce that somewhere very far away there should be structures that are very different than what you see locally. There should be mountains for this flow to flow from, or some ravines for this flow to fall into. So that would give you a probe of what the underlying very large scale structure of what your universe, or space-time, or some today call it multiverse, is that it is not just like what you see locally, but that sufficiently far away your space-time is very different from what you see here. So, in that sense it’s very much in agreement with the underlying inflationary paradigm that the initial space-time was very inhomogeneous, and we just happen to live inside a very homogeneous and isotropic bubble, but if we were to go very, very far away, we should be able to see such inhomogenities.
NTB: The galaxy clusters that make up this dark flow are rapidly moving toward a 20-degree patch of sky between the constellations of Centaurus and Vella. Why there, and do we know what’s attracting them?
Kashlinsky: Our limit on the 20-degree patch is purely due to observational error. If we were to make this measurement with, say, an infinite sample of clusters of galaxies and infinitely noiseless cosmic microwave background data, we presumably would measure just one uniform direction measurement. Why there? It’s by pure chance. It just happens to flow in that particular direction. As for what’s attracting them, we know that such flow cannot be generated by the matter distribution inside the observable universe, inside the universe that we observe. So, we therefore concluded that it must be something else very, very far away from us that is attracting them.
NTB: What impact, if any, does the discovery of dark flow have on our understanding of the universe and how it works?
Kashlinsky: What it tells us is that what we call, today, the universe is part of the overall cosmos, the overall space-time, whose structure is very different than what we see locally. Today, various issues of terminology that, at first, what people would call universes essentially...people would think that this is all the space-time there is and the universe, by definition, is all that there is in it. Today, people start talking in terms of multiverse, and multiverse is then composed of the various universes such as our own — that is, our own cosmological horizon, or our own bubble in the terms of this inflationary language. But there could be various other universes in this multiverse, in this landscape in which we live.
So, in that sense, what these measurements may imply is that our universe is just one of many and others may be very different from ours, and that there is an underlying multiverse in which these universes exist. So, if you would, it could imply an ultimate Copernican principle. It could generalize it, ultimately, that not only is our planetary system one of many, and our planet one of many, our universe may be just one of many.
NTB: One of the projects you’re currently working on at NASA is called “Studying Fluctuations in the Far IR Cosmic Infrared Background with COBE FIRAS Maps.” Tell us about that project and what you hope to accomplish with it.
Kashlinsky: This project and the group of us working on it — it’s myself, Dave Fixsen, and John Mather here at Goddard Space Flight Center — what it is designed to measure is the structure of the cosmic infrared background radiation at far infrared bands.
Why COBE FIRAS? FIRAS is the Far Infrared Absolute Spectrophotometer that was launched onboard the COBE satellite, the satellite that discovered cosmic microwave background structure. That instrument measured the spectrum of the cosmic microwave background radiation and it determined that it is a basic black body spectrum, basically down to almost one part in 1,000,000. But it also gave us very useful maps to work with for other parts of science. It measured all sky maps at the various far infrared wavelengths. Because we know the spectrum of the cosmic microwave background radiation, we can remove it from these maps very well. Then, if we’re lucky — and by lucky I mean if we can remove other foreground, such as our own galaxy, sufficiently well — we can then determine how much is produced by distant galaxies at far infrared wavelengths. That will give us very important cosmological information as to how these galaxies lived when they produced these emissions, how much of these emissions they produced, and so on and so forth. This project is just beginning, so I don’t know what our results will be, but the hope is to isolate the fluctuations in the cosmic infrared background radiation after subtracting the cosmic microwave background radiation from the FIRAS maps.
NTB: You mentioned that one of your co-investigators on this project is Dr. John Mather, the 2006 Nobel Laureate in physics. Do you ever find yourself dreaming of one day possibly winning a Nobel Prize, or is that something scientists don’t really think about until it happens?
Kashlinsky: Oh, I think it’s the latter. It just doesn’t cross the mind, I would say, of most scientists because you are so busy trying to understand whether the results you are measuring are real; what the systematics are; what the statistical significance is; whether you have been fooled by the various other processes that you have not accounted for; that it doesn’t give you much time to stress or share thoughts. So no, I don’t spend time thinking about it. And once you produce results, you really are worried that these are real results; that they can be maintained by future measurements; and you should always seek confirmation of these results, so no, there’s not much time to think about that.
NTB: What are some of the other significant projects you’re either working on, or anticipate working on, in the future?
Kashlinsky: It’s a very fortunate era now in the field of cosmology. I remember when I was starting my PhD, there was very little data to go by and there were many ideas, but also the theoretical part of the field was not particularly developed as I look back at it now. Slowly but surely, theoretical understanding developed and then, what’s even more important, in the last, I would say, ten or fifteen years there has been an explosion in the data – high quality data – that has been obtained in this field. This data comes from various space observatories or satellites such as the COBE satellite. It was a very important point in cosmology, and it was reached also thanks to the new generations of ground telescopes that can see very far with very high resolution and very low noise.
So, today you have a lot of data that can really constrain your understanding of the theoretical issues of the universe, and these data come at various wavelengths. For instance, in terms of cosmic microwave background measurements, there was COBE, then there was WMAP (Wilkinson Microwave Anisotropy Probe), which is still operating. It’s a superb instrument. And the Europeans are going to launch, this spring, the successor to WMAP, called the Planck satellite, which should bring a lot of new cosmic microwave background radiation data over a very wide range of frequencies with very low noise and with fairly good angular resolution. That is one of the projects we’re thinking to do with the dark flow studies; we want to try it with the Planck data.
At other wavelengths there is the Spitzer satellite, which is still operating. It is now about to begin its so-called warm mission because it’s run out of cryogens, so it has been extended for warm mission and it should still bring some very important data for understanding distant populations and the cosmic infrared background radiation emitted by them.
You can also go to a completely unexpected range of wavelengths or energies. At very high energies there is now operating… The GLAST (now renamed Fermi) satellite, which is the successor to the Compton Gamma Ray Observatory, and it is going to map the universe very well at gamma ray wavelengths and find a lot of distant gamma ray sources, gamma ray bursts, and so on. This would also be important in terms of studying early stellar populations because – this is one of the projects I hope to do with the data – you should see a very distinct cutoff in the spectrum of gamma-ray sources (bursts and blazars) at very large distances. This is produced by the cosmic infrared background from very early sources, such as Population 3, or the first black holes, and it is produced because the energy that these sources emit, which reach us in the infrared band, would also contain a lot of photons, and the very high-energy photons produced by these gamma ray bursts then would flow in the sea of IR photons – the cosmic infrared photons produced by the first stars – and they would get absorbed at sufficiently high energies by the so-called photon-photon absorption process. So, you should see a certain spectral feature that would tell you, yes, this is the epoch where these first stars lived. Maybe they lived for the first hundred-million years, maybe they lived for the first two-hundred-million years, and so on. You should be able to see the feature, if they produced enough energy.
And, of course, there are preparations for science that can be done with the James Webb Space Telescope, the JWST, which is going to be launched four or five years from now. That would be a successor to Hubble, but it also measures the universe in infrared bands, so it would see very far. It would see at completely different wavelengths, and it would bring a lot of data and probably revolutionize our understanding of the evolution of the universe.
To listen to this interview as a podcast, click here | 0.856271 | 3.822518 |
Richard Holme is Professor of Geomagnetism in the University’s School of Environmental Sciences:
“This year, 2016, is a leap year – we have an extra day, February 29th. This concept has a long history, and a number of cultural influences – traditionally, women are allowed to propose on February 29th and not on other days.
The ‘age’ of someone born on February 29th also provided an important plotline for William Gilbert in ‘The Pirates of Penzance.’ But why do we have leap years, and what is their impact?
The basic story is quite simple. The year (the time taken for the Earth going around the sun) is approximately 365.25 days, so to keep our seasons in phase with Earth’s orbit (so that, for example, 21st December is always the shortest day, or at least close to it) our normal 365-day year needs an extra day every four years.
In fact, it isn’t exactly this amount – the solar year is slightly shorter than 365.25 days, so that there is no leap year every hundred years (e.g., 1700, 1800, 1900). Only it isn’t quite this short, so there is a leap year every 400 years – so 2000 was a leap year, so this exception hasn’t been noticed by anyone still alive today, and most of us won’t be worrying about the next special case in 2100.
This correction was due to Pope Gregory – September in 1752 had only 19 days, causing large-scale demonstrations from people demanding back their “stolen” day.
All very simple and algebraic, except that the real Earth and solar system aren’t quite so simple. There are variations in both the rate of rotation of the Earth (the length-of-day) and orbital period around the sun. The latter arise primarily due to gravitational interactions between the planets – Jupiter in particular has a strong influence on the other planets because of its size.
Formally, orbital dynamics is a chaotic system – it becomes increasingly difficult to predict the planets’ paths with time, and going back in time, we can’t calculate the position of the planets in time further back than about 60 million years due to uncertainties caused by the positions of the (really rather small) asteroids Vesta and Ceres.
Variations in orbital structure have important implications for studies of past climate – extremely important for discussions of anthropogenic climate change.
Length-of-day variations (changes in the spin of the Earth) occur on timescales from hundreds of millions of years (the slowing down of Earth’s spin due to lunar tides), through millennia (post-glacial rebound) through decades (exchange of “spin” (angular momentum) between the solid Earth and its fluid core) to variations on daily or shorter time scales (due to the winds “blowing” the Earth faster or slower).
These variations – milliseconds over the 86400 seconds in a standard day – provide a geophysical probe of the Earth system which tell us much about its interior and the interactions between its different parts – all used by scientists at Liverpool! They also give rise to “leap seconds” – extra seconds in the year, because the average day is slightly longer than 86400 seconds.
The last leap second was on June 30th 2015 – I hope you used your extra time well – I did, an extra second of sleep! These changes keep mid-day at Greenwich truly at mid-day, but may well be abolished – the computing, communications and even financial sectors find them very difficult to deal with.
What implications does the leap year have for us at Liverpool?
Well, it means that term in September will start not one day earlier than last year, but two days earlier – meaning fewer years until we get a jump in the academic year and an extra week in the summer. Not to mention an extra day before the start of Christmas shopping!.”
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With all the attention that astronomers have lavished on old Sol over the centuries, you'd think that by now they'd know its diameter to, oh, 10 or 12 significant digits.
Nope. While the Sun's girth has indeed been measured dozens of times over the past 40 years, the results haven't converged on a single value and scatter by as much as ± 0.1%. One big reason is that, though some measurement techniques are extremely precise, their accuracy suffers because of the turbulence induced by Earth's atmosphere. Most often astronomers use a compromise value of 865,000 miles (1,392,000 km).
So Marcelo Emilio (State university of Ponta Grossa, Brazil) has teamed with observers at the University of Hawaii and Stanford to approach this measurement with, literally, space-age techniques. They used images taken by the Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory (SOHO), homing in on transits of the planet Mercury across the solar disk in 2003 and 2006.
This makes perfect sense. The spacecraft sits at the L1 Lagrange point, a million miles from Earth, and Mercury has nothing but the barest wisps of atmosphere — a made-to-order combination for crisp images. (The SOHO team has posted a movie of 2006 transit).
However, as the team describes in a forthcoming issue of Astrophysical Journal, the technique wasn't without its complications.
For example, the MDI takes images that are 1,024 pixels on a side — state of the art when the spacecraft was built during the 1990s, but still yielding a modest resolution of 4 arcseconds in its full-Sun imaging mode. That's a bit less than half of Mercury's diameter during each transit. Also picking the instrument's focus point also affects the crispness of the planet's silhouette against the solar disk. And then there's the matter of where, exactly, to place the "edge" of the of the Sun's photosphere.
Taking all these factors into consideration, Emilio and his collaborators peg the diameter of the Sun at 865,374 miles (1,392,684 km), plus or minus about 0.01%. And they got the same solar size during both transits, confirming (as this same group reported two years ago) that the Sun's diameter is "rock steady."
It should be possible for researchers to improve on this new value when Venus transits the Sun in just a couple of months (76 days to be exact). This time astronomers can use the Solar Dynamics Observatory, which can take images with four times better resolution than SOHO. "SDO will be able to see the transit of Venus in June and we have several activities planned," according to project scientist Dean Pesnell. In fact, the SDO team has launched its own transit website, though it's still under development. | 0.820552 | 3.938488 |
New research reveals the origins of fundamental structures in the wind on a supergiant star
An international team of astronomers have discovered, for the first time, observational evidence in how some features at the surface of the hot massive supergiant star ‘Zeta Puppis’ induce the formation of fundamental structures in its wind.
In contrast to cool low-mass stars like the Sun, hot massive stars are scarce, possess extremely strong winds, and catastrophically end their lives as supernovae that stir up and enrich the interstellar medium with chemical elements involved in the creation of new stars and even planets like Earth. Thus, the research team’s breakthrough results on the hot massive supergiant star Zeta Puppis are a significant step towards a better understanding of the true nature of hot massive stars which play a crucial role in the evolution of the Universe.
The team used the network of nanosatellites of the BRIght Target Explorer (BRITE) space mission to monitor the visible brightness changes coming from the surface of Zeta Puppis over about six months, and simultaneously monitored the behavior of the wind of the star from several ground-based professional and amateur observatories.
The observations, published in Monthly Notices of the Royal Astronomical Society, revealed a 1.78-day periodicity both at the surface and in the wind of Zeta Puppis. The behaviour of this periodic signal turns out to reflect the spinning of the star through the presence of slowly evolving bright spots tied to its surface, which are driving large-scale spiral-like structures dubbed corotating interaction regions (CIRs) in its wind.
Tahina Ramiaramanantsoa, PhD student at the Université de Montréal and member of the Centre de Recherche en Astrophysique du Québec (CRAQ), who led the investigation, said, “Once we found that the variations in the brightness of Zeta Pup arise because bright spots on its surface are carried into and out of our view by the star’s rotation every 1.78 days, we employed an algorithm that used those brightness variations to make maps showing where the bright spots are on the star’s surface and how they change over time. Then by studying the light emitted at a specific wavelength by ionized helium from the star’s wind, we clearly saw some “S” patterns that are caused by arms of CIRs induced in the wind by the bright surface spots.”
The 1.78 day periodicity was initially discovered in 2014 using an instrument called SMEI (Solar Mass Ejection Imager), designed and built at the University of Birmingham. However, at that point the origin on the period was unclear. The new data from the BRITE nanosatellites has enabled this mystery to be solved.
In addition to the 1.78-day periodicity, the research team also detected random changes on timescales of hours at the surface of Zeta Puppis, strongly correlated with the behavior of small regions of higher density in the wind known as “clumps” that travel outward from the star.
Anthony Moffat, professor emeritus at Université de Montréal, and Principal Investigator for the Canadian contribution to the BRITE mission, explained, “These results are very exciting because we also find evidence, for the first time, of a direct link between surface variations and wind clumping, both random in nature.”
The southern naked-eye bright star Zeta Puppis is an evolved massive star currently at the stage of supergiant. It is often considered as the archetype of hot massive stars with strong stellar winds. Indeed, about sixty times more massive and seven times hotter than the Sun, Zeta Puppis has a stellar wind about a billion times stronger than that of the Sun. In that sense, the solar wind that drives aurorae and shapes the tails of comets appears like a light breeze when compared to the gale-force wind from Zeta Puppis.
Also, most massive stars occur in binary or multiple systems. However, Zeta Puppis is particular because not only is it amongst the few massive stars known to be single, but also it is moving through space at a particularly fast velocity of about 60 km/s.
Dany Vanbeveren, professor at Vrije Universiteit Brussels, said, “The existing theoretical scenarios that explain this high peculiar space velocity for Zeta Pup involve past interactions within a binary or a multiple system, and predicted a relatively short rotation period for the star. That prediction is now supported by these new observational results.”
Dr Ian Stevens, from the School of Physics and Astronomy at the University of Birmingham, said, “Zeta Pup will become either a black hole or a neutron star at the end of its life. In that regard, it is interesting to realise that, if Zeta Pup had survived its past interactions within a massive binary system, it would have been a perfect candidate for the generation of a gravitational-wave signals from the coalescence of a pair involving any combination of stellar-mass black holes or neutron stars in the future!”
The physical origins of the bright surface spots and the random brightness variations discovered in Zeta Puppis remain unknown at this point, and will be the subject of further investigations.
After several decades of puzzling over the potential link between the surface variability of very hot massive stars and their wind variability, these results are a significant breakthrough in massive star research, essentially owing to the BRITE nanosatellites and the large contribution by amateur astronomers.
“It is really exciting to know that, even in the era of giant professional telescopes, dedicated amateur astronomers using off-the-shelf equipment at their backyard observatories can play a significant role at the scientific front!”, said investigating team member Paul Luckas from the International Centre for Radio Astronomy Research (ICRAR) at the University of Western Australia. Paul is one of the six amateur astronomers who intensively observed Zeta Puppis from their backyard small observatories during the observing campaign, as part of the Southern Amateur Spectroscopy initiative.
Notes to editors
For more information, or interviews with Dr Stevens, please contact Luke Harrison, Media Relations Manager, University of Birmingham on +44 (0)121 414 5134.
To contact lead investigator, Tahina Ramiaramanantsoa at Université de Montréal and Centre de Recherche en Astrophysique du Québec (CRAQ), email [email protected]
More information on the BRITE mission. | 0.883975 | 4.06706 |
Radio astronomy is the study of the radio frequencies emitted from stars, galaxies and other celestial objects. Radio waves are produced naturally from lightning and astronomical objects, or are produced by man-made communication techniques and broadcasting technology.Many radio telescopes are located around the globe and have helped discover new types of stars and galaxies that do not emit light and remain invisible to traditional telescopes. The catalyst for the birth of this new subfield in astronomy was a man often deemed the “father of radio astronomy”, Karl Jansky.
Karl Guthe Jansky (1905-50) was born in Norman, Oklahoma; he was of French, Czech and English descent and grew up in Madison, Wisconsin. Jansky was the third of six children and was named after physicist Karl Guthe whom his father Cyril Jansky had worked for earlier in his career.An interest in science and physics was perhaps in Karl’s genes as Cyril Jansky was a teacher who retired as a professor of Electrical Engineering at the University of Wisconsin.Karl Jansky’s eldest brother Cyril M. Jansky Jnr, also became a professor in radio engineering at the University of Minnesota.
Jansky joined Bell laboratories, New Jersey in 1928 after graduating from the University of Wisconsin with a degree in physics the previous year.He started his master’s degree immediately after his undergraduate degree but never completed it.Initially Karl Jansky was refused a position in the company until his brother Cyril, who was familiar with some members of the personnel department, persuaded them to take a chance on his little brother. Bell Laboratories wanted to improve their radiotelephone service and Jansky was assigned the role of investigating the origins of static which was affecting trans-Atlantic radio transmissions.
In 1929, Karl Jansky began building an antenna to receive radio signals.This antenna system rotated, scanning the sky in 20 minutes , and gaining the nickname Jansky’s Merry-Go-Round.In the autumn of the following year his rotating short radio wave receiver was in working order.After recording signals for several months Jansky discovered three types of static.A weak signal caused by distant thunder storms, a more powerful burst due to local thunder storms and a third type which produced a steady hiss.In a 1933 journal article “Electrical Disturbances apparently of extra-terrestrial origin” Jansky refers to these electromagnetic waves detected causing the hiss to be coming from an unknown origin.
Jansky originally believed the steady hiss to be radiation coming from the Sun but after investigating this emission for over a year he discovered that the radio signal was not repeated every 24 hours like a solar day.Instead, it repeated every 23hours and 56 minutes , this was the same as a sidereal day, that is the time it takes for the stars to rotate across the sky (of course, they are really essentially stationary which the Earth rotates under them) .This discovery allowed Jansky to determine that the signal was not coming from our Solar System but instead from the centre of Milky Way in the direction of the constellation of Sagittarius.
This astonishing and uexpected discovery appeared in many publications including the New York Times in May 1933.Karl then proposed that Bell Laboratories build a 30 m dish antenna to study the galactic radio waves in more detail.During the 1930s the Great Depression had swept across America and funding a radical science project was not on the cards for another few years.Also, the original premise of his work was to discover the origins of static which he had achieved.Jansky then moved to a different department in Bell Labs measuring noise, but continued to investigate the stellar waves in his own time.He submitted his dissertation entitled ‘Star Noise’ which finally gained him his Masters degree in 1936.During the Second World War, Jansky worked in the development of direction finders to locate German submarines, and after the war he developed frequency amplifiers.
Karl Jansky died on Valentine’s Day, 1950 at 44 years old after suffering for years from Bright’s disease, a chronic kidney disease. Jansky was diagnosed with kidney problems during his time at university and towards the end of his life; despite special diets he had high blood pressure and heart problems.His two children were still in their teens. Karl Jansky never had the opportunity to delve deeper into the study of interstellar radio waves.
However, despite never pursuing his keen interest into radio astronomy, Jansky is often recognised as the first person to discover these signals coming from outer space.He was fortunate during the time of research, in the early 1930s, that the Sun was going through an inactive period in its 11 year sun-spot cycle so detecting signals from further a field was easier.Otherwise the Sun’s radiation would have overwhelmed any other signals.Jansky’s findings inspired many other scientists such as Grote Reber who built his own radio telescope in 1937 and John Kraus who established a radio observatory after the war; both names now synonymous with Radio Astronomy.
Karl Guthe Jansky whilst just doing his normal job made a very important discovery in the realms of astronomy, despite never being an astronomer.
Discoveries of radio signals travelling from the centre of our galaxy inspired a new subfield of astronomy to be established and many subsequent discoveries to be made, which in turn justifies and explains that Karl Jansky should be the father of Radio Astronomy, he even has a unit named after him.
The unit of strength of radio sources is now known as the jansky.
(Article by Martina Redpath, Education Support Officer) | 0.873229 | 3.454795 |
Research to be published today in the respected journal Science presents observations made by NASA’s four Magnetospheric Multiscale (MMS) satellites in the Earth’s magnetotail. Two scientists from the Swedish Institute of Space Physics (IRF) in Uppsala are co-authors of the article. The lead author is from the University of New Hampshire in USA.
Magnetic reconnection is an energy conversion process important in many astrophysical contexts including the Earth’s magnetosphere, where the process releases the energy powering the auroras. The article presents the first encounter of a reconnection site by the MMS spacecraft in the magnetotail, one of the few regions where the process can be investigated by satellites in-situ. The unprecedented electron-scale plasma measurements revealed super-Alfvénic electron jets reaching 15,000 km/s, electron meandering motion and acceleration by the electric field. Despite the presence of turbulence near the reconnection site, the well-structured multiple layers of electron populations indicate that the key electron dynamics appear to be largely laminar.
The magnetotail reconnection electron diffusion region differs from that on the dayside as it involves symmetric conditions on both sides of the reconnecting current sheet. MMS determined the aspect ratio of the diffusion region (0.1-0.2), which is consistent with predictions for fast reconnection. The MMS observations of electron dynamics in the diffusion region match predictions made by one class of theories and models – nearly laminar ones that assume the effects of turbulence and associated fluctuations on the electron dynamics are small. Electrons can be accelerated up to three successive times by the reconnection electric field, possibly as a consequence of longer confinement in the symmetric magnetic structure. Taken together with MMS observations at the magnetopause, these results provide confirmation that reconnection is an efficient mechanism for the release of magnetic energy, for both geomagnetic substorms and auroral phenomena.
“The magnetotail plasma sheet is one of the hottest places in our solar system, with plasma temperatures reaching 100 million degrees”, says Yuri Khotyaintsev of the Swedish Institute of Space Physics. “Reconnection is one of the key processes involved in heating the plasma. The new MMS measurements help us to understand how the plasma particles and in particular electrons are accelerated during reconnection.”
R. B. Torbert et al., “Electron-Scale Dynamics of the Diffusion Region during Symmetric Magnetic Reconnection in Space”, to be published in Science on 15 November 2018.
- Love Alm, Postdoctoral Fellow, Swedish Institute of Space Physics, Uppsala, [email protected], tel. +46-18-471 5923, +46-70-377 1795.
- Yuri Khotyaintsev, Associate Professor, Swedish Institute of Space Physics, Uppsala, [email protected], tel. +46-18-471 5929
Institutet för rymdfysik, IRF, är ett statligt forskningsinstitut under Utbildningsdepartementet. IRF bedriver grundforskning och forskarutbildning i rymdfysik, atmosfärfysik och rymdteknik. Mätningar görs i atmosfären, jonosfären, magnetosfären och runt andra planeter med hjälp av ballonger, markbaserad utrustning (bl a radar) och satelliter. För närvarande har IRF instrument ombord på satelliter i bana runt jorden och Mars. IRF har ca 100 anställda och bedriver verksamhet i Kiruna (huvudkontoret), Umeå, Uppsala och Lund.
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The Swedish Institute of Space Physics (IRF) is a governmental research institute which conducts research and postgraduate education in atmospheric physics, space physics and space technology. Measurements are made in the atmosphere, ionosphere, magnetosphere and around other planets with the help of ground-based equipment (including radar), stratospheric balloons and satellites. IRF was established (as Kiruna Geophysical Observatory) in 1957 and its first satellite instrument was launched in 1968. The head office is in Kiruna (geographic coordinates 67.84° N, 20.41° E) and IRF also has offices in Umeå, Uppsala and Lund. | 0.819494 | 3.834141 |
NASA’s planet-hunting TESS mission has found its first Earth-size exoplanet in a star system only 53 light-years from Earth. Another exoplanet, a warm mini-Neptune, was found in the same system.
“It’s so exciting that TESS, which launched just about a year ago, is already a game-changer in the planet-hunting business,” Johanna Teske, author of a study describing the planets and Hubble Postdoctoral Fellow at the Carnegie Institution for Science, said in a statement. “The spacecraft surveys the sky and we collaborate with the TESS follow-up community to flag potentially interesting targets for additional observations using ground-based telescopes and instruments.”
The Earth-size planet, dubbed HD 21749c, completes an orbit of its host star every eight days. Its planetary sibling, HD 21749b, is about 23 times Earth’s mass and has a radius about 2.7 times that of Earth. This puts the exoplanet in the category of a sub-Neptune or mini-Neptune.
The study was published in The Astrophysical Journal Letters Monday.
Researchers determined that the density suggests the mini-Neptune has a substantial atmosphere. But it’s not a rocky planet, like Earth, which could make for insightful followup observations about how the atmosphere is composed and its evolution.
The star both planets orbit has the equivalent of 80% of our sun’s mass.
Most of the exoplanets TESS will find are expected to have orbital periods of 10 days or less. The mini-Neptune was an exciting find for researchers because of its orbital period of 36 days.
This made the discovery more challenging. The researchers used the Planet Finder Spectrograph on the Magellan II telescope at Las Campanas Observatory in Chile to confirm the signals picked up by TESS were planets. This device also measured the mass of the mini-Neptune.
Mass is key for exoplanet discovery because it enables the determination of density or even chemical composition.
“There was quite some detective work involved, and the right people were there at the right time,” said Diana Dragomir, lead study author and Hubble Fellow at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, in a statement. “But we were lucky, and we caught the signals, and they were really clear.”
The researchers hope to learn more about the Earth-size planet, as well.
“Measuring the exact mass and composition of such a small planet will be challenging, but important for comparing HD 21749c to Earth,” said Sharon Wang, study author and Carnegie Institution for Science postdoctoral fellow, in a statement. “Carnegie’s [Planet Finder Spectrograph] team is continuing to collect data on this object with this goal in mind.”
TESS will look for exoplanets using the transit method, observing slight dips in stars’ brightness as planets pass in front of them. Bright stars allow for easier followup study through ground- and space-based telescopes.
NASA expects TESS to allow for the cataloging of more than 1,500 exoplanets, but it has the potential to find thousands. Of these, officials anticipate, 300 will be Earth-size exoplanets or double-Earth-size super Earths. Those planets could be the best candidates for supporting life outside our solar system. Like Earth, they are small, rocky and usually within the habitable zones of their stars, meaning liquid water can exist on the surface.
TESS is considered a “bridge to the future,” finding exoplanet candidates to study in more detail.
These exoplanets will be studied so NASA can determine the best targets for missions like the James Webb Space Telescope. That telescope, launching in 2021, would be able to characterize the details and atmospheres of exoplanets in ways scientists have not been able to do.
But TESS will also help researchers measure mass and maybe even the composition of planetary atmospheres.
“For stars that are very close by and very bright, we expected to find up to a couple dozen Earth-sized planets,” Dragomir said. “And here we are — this would be our first one, and it’s a milestone for TESS. It sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable.” | 0.891121 | 3.585296 |
7 Earth-sized worlds found orbiting star, could hold life
In what NASA researcher Sean Carey calls the “most exciting discovery” made using the Spitzer Telescope, NASA announced the discovery of seven new planets near a dwarf star, known as TRAPPIST-1.
The earth-sized planets are estimated to be 39 light years away from Earth. Because the planets are located outside of our solar system, the planets are given the term “exo-planets.”
Using the Spitzer telescope, researchers discovered that the TRAPPIST-1 star is a dwarf star that is much cooler and much smaller than the sun. The planet system is the first known system of Earth sized planets around a single star.
"This discovery gives a hint that discovering a second earth is not a matter of if, but when," said Thomas Zurbuchen, NASA associate administrator of the Science Mission Directorate.
Three of the planets are located within the ‘habitable zone.’ Scientists believe that all seven could have liquid water on the planet’s surface, but the highest chances come with the three within the habitable zone.
Nikole Lewis, an astronomer with the Space Telescope Science Institute says the temperatures on the exo-planet known as TRAPPIST-1E could be very similar to earth's. TRAPPIST-1E is close in size to our earth, and receives the same amount of light as earth does.
"The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star," said Michael Gillon, principal investigator of the TRAPPIST exoplanet survey at the University of Liege, Belgium. "It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds."
"The TRAPPIST-1 system provides one of the best opportunities in the next decade to study the atmospheres around Earth-size planets," said Nikole Lewis, astronomer at the Space Telescope Science Institute in Baltimore, Maryland.
Scientists believe the planets are could be tidally locked to their star, which means that only one side of the planet will face the star.
Spitzer, Hubble, and Kepler will help astronomers plan for follow-up studies using NASA's upcoming James Webb Space Telescope which will launch in 2018.
The Webb telescope will be able to detect the chemical fingerprints of water, methane, oxygen, ozone, and other components of a planet's atmosphere. Webb will also analyze planets' temperatures and surface pressures – key factors in assessing their habitability. | 0.807309 | 3.57273 |
Basic Facts About the Sun
Most of the facts about the sun known to us today are fairly recent, coming after the invention of the telescope, photography, spectroscopy, and the launching of satellites.
Invention of the Telescope
It appears that the earliest working models of the telescope seem to have been invented by Hans Lippershy in 1608. Just a year later, Galileo was using these devices to do incredible research, helping him discover that the sun was rotating – and fully convincing him that the Heavens were governed by predictible movement. This lead to his later assertion, that the Earth moves around the sun - one of the most basic facts about the sun.
However it wasn't until the invention of photography and spectroscopy in the 19th century, combined with proper record keeping, that proper solar research could begin, and we could finally learn some more useful facts about the sun.
On September 1st, 1859, a British astronomer observed and recorded for the first time a major coronal mass ejection / solar flare, now known as the “Carrington Event”. As the radiation from the storm hit the Earth it knocked out telegraphs - the world’s first electromagnetic-based communications system. Since then a number of solar storms have demonstrated the fragility of our electronic communications and power systems.
Click on the following links to learn more about
Coronal Mass Ejections
or about why NASA and other scientists are concerned that an even worse scenario than what happened in 1859 could occur in
In 1989 a similar solar storm destroyed a transformer and blacked out most of Quebec. Since then, our dependence on delicate digital systems has increased and few of them are hardened against sudden spikes in solar radiation. Even moderate solar activity can have an effect on our lives such as degrading the accuracy of the signals from the GPS satellites or the power-output from communications satellites.
In 1998 a solar storm knocked out a communications satellite and rendered millions of pagers all over America useless.
Even moderate solar activity can have an effect on our lives such as degrading the accuracy of the signals from the GPS satellites or the power-output from communications satellites.
Increasing our understanding of the sun and the ability to predict solar weather is a key goal of the Solar Dynamics Observatory [SDO] NASA launched in February 2010 to study the variability of the sun.
SDO is equipped with cameras that will be able to take IMAX-quality images of solar explosions. It also has sensors that can look deep inside the sun to reveal the inner workings of the sun’s magnetic dynamo, the root of all solar activity. SDO’s Helioseismic and magnetic imager will allow “Scientists to make ultrasound images of the Sun and to study active regions in a way similar to watching sand shift in a desert dune.”
The following is one of the first photos from SDO showing a huge loop of material shooting up from the sun's surface in March. Known as a prominence eruption, the loop was born from a relatively cold cloud of plasma, or charged gas, tenuously tethered to the sun's surface by magnetic forces. Such clouds can erupt dramatically when they break free of the sun's unstable hold.
The most important feature of NASA’s SDO mission is the Solar Sentinel program, which will send a series of satellites that will give us a permanent three-dimensional near-real-time vision of the Sun. These spacecraft will actually lead the way towards a move from gathering data for science and gathering data for what might be termed - Solar System Wide Weather forecasting.
Meanwhile, the following is a summary of some of the facts about the sun we have learned so far:
Made from Recycled Material
Our sun is one of around 300 billion stars in the Milky Way Galaxy, which was formed around 9 billion years ago.
If you want to know what recycling is good for you … be thankful for the sun. It formed from an interstellar cloud 4.6 billion years ago, out of material that had been at least partially recycled from earlier generations of stars in our Galaxy. It accounts for 99.8% of the mass of our solar system.
Almost all of the elements in the Sun beyond element number 2 (helium) were made in these earlier generations of stars, including small amounts of sulfur, magnesium, carbon, neon, iron, oxygen, nickel, chromium and calcium.
The Sun's Orbit
The Sun orbits the center of the Milky Way at a distance of approximately 24 to 26 thousand light years from the galactic center, completing one clockwise orbit every 225 to 250 million years. The Sun has circled the Milky Way galaxy about 20 times only since it's formation.
The Sun is pretty bright
Our own Sun is a relatively bright star. Of the stars within 17 light-years of the Earth and ranked them by brightness, our sun would be number 4.
The luminosity of the Sun is equivalent to the luminosity of 4 trillion, trillion 100 watt light bulbs.
Color of the Sun
From space, the Sun looks white.
Why then does it appear reddish around sunrise and sunset … and yellow during the day?
Basically the reason has to do with the absorption and scattering of the electromagnetic energy by the molecules of gas that make up the atmosphere (ozone, nitrogen, oxygen, argon, water vapor, etc.). Gas molecules are smaller than the wavelength of visible light. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates the light in a different direction. The color radiated is the same color absorbed. All of the colors can be absorbed, but the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)
As the sun begins to set, the light must travel farther through the atmosphere before it gets to you. More of the light is reflected and scattered. As less reaches you directly more of the light is absorbed / scattered. The sun loses its brightness and color of the sun itself appears to change, first to orange and then to red. This is because even more of the short wavelength blues and greens are now scattered. Only the longer wavelengths (reds and oranges) are left in the direct beam that reaches your eyes.
The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water. These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out. You see the longer wavelengths, and the sky appears red, pink or orange.
It feels like the Sun has been around forever, unchanging, but that's not true. The Sun is actually slowly heating up. It's becoming 10% more luminous every billion years.
In fact, within just a billion years, the heat from the Sun will be so intense that liquid water won't exist on the surface of the Earth. Life on Earth as we know it will be gone forever.
It'll take another 7 billion years for the Sun to reach its red giant phase before it actually expands to the point that it engulfs the Earth and destroys the entire planet. In other words, the expected life of the sun is around 11 billion years.
Rotation of the Sun
All matter in the Sun is in the form of gas and plasma because of its high temperatures.
One of the most potentially important facts about the sun deals with the rotations of these gases and plasma. Because of the effects of gravity, the Sun rotates faster at its equator (about 25 days) than it does at higher latitudes (about 35 days near its poles).
The differential rotation speeds causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the Sun's surface and trigger the formation of the Sun's dramatic sunspots,
coronal mass ejections (CMEs)
and geomagnetic storms.
Every 11 years solar cycle of magnetic activity. Basically, this means that the sun reverse's it magnetic field about every 11 years, i.e., its north magnetic pole becomes a south pole, and vice versa.
Click here to read more about solar flares, geomagnetic storms and the problems they can cause.
22 Year Magnetic Cycle
The Sun has a strong and complex magnetic field, which is caused in part because the varying speeds that the plasma spins as the sun rotates on its axis. The sun's magnetic field plays an important role in most aspects of the active Sun (sunspots, prominences, flares, the solar wind, and the nature of the corona), so the 22 year magnetic cycle is central to the periodicity of the active Sun.
On average the Sun's polarity reverses every 11 years, i.e., the north magnetic pole becomes the south pole, and vice versa. The Solar magnetic field has a 22 year cycle, exactly twice that of the sunspot cycle, because the polarity of the field returns to its original value every two sunspot cycles.
Sunspot Cycle 24
After viewing the sun with his new telescope, Galileo made the first European observations of sunspots in 1610. Solar sunspot cycles have been tracked continuously since March 1755 in the West. We are currently in cycle 24, which started December 2001. On average, each cycle lasts 11.1 years.
Sunspots are well-defined surface areas that appear darker than their surroundings because of lower temperatures. The largest sunspots can be tens of thousands of kilometers across. As the temperatures cool, the sun contracts increasing the pressure below the sunspot, and helping to keep the nuclear fusion reactions going.
During a 75-year period beginning in 1645, astronomers detected almost no sunspot activity on the sun. Called the “Maunder Minimum,” this event coincided with the coldest part of the Little Ice Age, a 350-year cold spell that gripped much of Europe and North America.
Note 1: F. Richard Stephenson and Kevin K.C. Yau found evidence or more than 200 records of sunspot activity in the Orient going back to 200 BC.
Note 2: A recent theory claims that there are magnetic instabilities in the core of the Sun that cause fluctuations with periods of either 41,000 or 100,000 years. These could provide a better explanation of the ice ages.
Solar winds are essentially bands of plasma, extremely hot, charged particles, or electrons that escape from the Sun's surface. They carry around 6.7 billion tons of matter away from the sun per hour This is equivalent to losing a mass equal to the Earth every 150 million years. However, given the size of the sun even these large number only represent about 0.01% of the Sun's total mass has been lost through the solar wind.
The solar wind is not uniform. Although it is always directed away from the Sun, it changes speed and carries with it magnetic clouds, interacting regions where high speed wind (800 km/s) catches up with slow speed wind (300 km/s). These high and low speed streams interact with each other and alternately pass by the Earth as the Sun rotates.
These wind speed variations buffet the Earth's magnetic field and can produce storms in the Earth's magnetosphere and can cause numerous problems.
The wind is considered responsible for the tails of comets to always face away from the sun.
For more information about possible risks and problems caused by solar winds, see a more detailed explanation regarding
and geomagnetic storms.
The energy output of the sun has been relatively stable over the past 50,000 years which has allowed humanity to flourish. Scientists predict that even though there are likely to be numerous fluctuations (e.g., solar flares, coronal mass ejections, etc.) the energy output should remain fairly constant for another 50,000 years, which gives a fair amount of time to get our collective act together.
Miscellaneous Facts About the Sun
The Greek philosopher Aristarchus of Samos (310 to 230 BC) is credited as being the first person to claim that the Earth orbited the sun. The crater Aristarchus on the Moon is named in his honor.
During photosynthesis the sun's energy is used to split water molecules, starting a flow of electrons. The energy from this flow of electrons is harnessed and used to make the bonds in organic molecules.
The source of the sun's energy has challenged scientists for centuries. In the 19th century it was assumed that the sun's energy resulted from its gravitational collapse.
Some solar scientists believe that global warming is caused primarily by solar activity and that while man-made pollution causes a host of other problems and does contribute to global warming it is not the major cause, however at the present time this is more of a theory than widely accepted fact.
Solar eclipses are visible in a narrow path, a maximum of 269 km wide. A maximum of 5 Solar eclipses only can occur in an year. No Total solar eclipse can last longer than 7 minutes and 58 seconds because of the speed that the earth and moon rotate. At any place on the Earth, a total solar eclipse will occur on an average of once every 360 years.
Approximately one million Earths can fit inside the Sun.
Around 50 trillion neutrinos from the Sun will pass through your body every second while you read this sentence. Neutrinos are a by-product of the fusion of hydrogen into helium – and are basically mass-less and as the name implies, charge neutral.
The Near-Term Future
Mainstream scientific concern about the consequences of peak solar activity that could occur in 2012 has grown since a recent National Research Council report funded by NASA and issued by the National Academy of Sciences, entitled “Severe Space Weather Events: Understanding Economic and Societal Impact” was issued.
This report details the potential devastation that a severe solar storm could have on the current planetary energy grid and because of the inter-linkages of a cybernetic society, on our entire human civilization. The report has stimulated a number of interesting discussions regarding ways that utility operators, the military, corporations and individuals can protect their vulnerable electronics, and provide another reason to consider the potential benefits of producing your own electricity and reducing your dependency on the electrical grid.
Stay tuned as we intend to update an expand our section on facts about the sun, including adding more links to related articles you might find beneficial.
Click on the appropriate link to return to the top of this
Facts About the Sun
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Creating Moon craters
If you've ever seen a photo of Earth's Moon, you may have noticed that there are numerous craters on its surface. Some of them are bigger than cities on Earth! About 80% of the Moon's surface is covered in craters. These are impact marks left on the Moon's surface by ancient meteorites or other celestial bodies. Meteorite impacts have been shaping Earth and the Moon for over 4 billion years. Craters on the Moon are virtually permanent, as opposed to those on Earth. Earth has processes such as erosion, which constantly changes Earth's landscape. As a result, traces of craters are harder to find.
In this activity, you will be recreating the Moon's craters and exploring how a crater's size, ejecta, and characteristics depend on the incoming meteorite's mass, velocity, angle and height. The Moon's Tycho crater (bottom left), which looks like the navel on an orange, is 86 km in diameter, almost 5 km deep and approximately 108 million years old.
Did you know?
- The Moon does not shine with its own light. It simply reflects the light coming from the Sun.
- There is no wind or air on the Moon to move the soil, so its surface is covered with old and new impact craters.
- Only 12 astronauts have walked on the Moon. They were all Americans who flew on six different missions between and .
- The United States, the Soviet Union (now Russia) and China have landed unmanned spacecraft on the Moon.
You will need:
- A large baking tray or plastic container that is about 6 cm deep
- Flour (to a depth of about 5 cm in the tray or container)
- Cinnamon or cocoa (to a depth of about 1 cm in the tray or container)
- A sifter
- 4 or 5 rocks of different shapes and sizes
- Safety glasses
- Ruler (optional)
How to make your craters:
- Lay down several sheets of newspaper for easy cleanup.
- Pour and evenly spread 5 cm of flour in your baking tray or plastic container.
- Using the sifter, evenly sift 1 cm of cinnamon or cocoa on top of the flour. This will be the Moon's surface.
- Hold your first rock 40 cm to 50 cm above the tray or container.
- Drop it into the tray or container to simulate a meteorite impact.
- Carefully remove the rock and observe the crater created. The material that was ejected is called the ejecta.
- Experiment by dropping differently sized rocks at various angles and heights, and see how one ejecta pattern differs from the next.
How it works:
When you throw a rock, it gains kinetic energy (which means the energy that an object has because it is in motion). When the rock hits the flat, powdery surface, its kinetic energy is transferred to the powder and creates an impact crater. Try different heights (e.g. 1 metre, 2 metres) and different angles. The craters should change their shape depending on the speed, size and angle of the incoming meteorite. Higher-energy impacts make bigger craters, with debris shooting out from their centres as "
rays." Throwing a rock at an angle makes an oblong crater.
Calculate the effects of a meteorite impact on the Moon, Earth and Mars using the Impact Calculator.
- Crater: a large, bowl-shaped cavity on the surface of a planet or the Moon, typically one caused by an explosion or the impact of a meteorite or other celestial body
- Meteorite: a fragment of matter from outer space that strikes the surface of a planet or the Moon
- Erosion: the process of being gradually worn away by wind, water or other natural agents
- Ejecta: material that is forced or thrown out, especially as a result of volcanic eruption, meteoritic impact or stellar explosion
- Date modified: | 0.817479 | 3.688744 |
Paris: Stupefied astronomers on Wednesday unveiled the first and only known galaxy without dark matter, the invisible and poorly-understood substance thought to make up a quarter of the Universe.
The discovery could revise or even upend theories of how galaxies are formed, they reported in the journal Nature.
"This is really bizarre," said co-author Roberto Abraham, an astronomer at the University of Toronto.
"For a galaxy this size, it should have 30 times as much dark matter as regular matter," he told AFP by phone. "What we found is that there is no dark matter at all."
"That shouldn't be possible," he added.
There are 200 billion observable galaxies, perhaps more, astronomers estimate.
Some 65 million light-years from Earth, NGC1052-DF2 -- "DF2" for short -- is about the same size as our Milky Way, but has 100 to 1,000 times fewer stars.
Dark matter's existence is inferred from the motion of objects affected by its gravitational pull.
"It is conventionally believed to be an integral part of all galaxies, the glue that holds them together and the underlying scaffolding on which they are built," said co-author Allison Merritt from the Max Planck Institute for Astronomy, in Germany.
One surprise after another
So-called ordinary matter -- including stars, gases, dust, planets and everything on them -- accounts for only five percent of all content in the Universe.
Dark matter and dark energy comprise the rest, and scientists have yet to directly observe either.
The discovery was made with a new kind of telescope developed by Abraham and lead author Pieter van Dokkum of Yale University.
Unlike mirror-based devices, the mobile Dragonfly Telescope Array is composed entirely of nano-coated lenses, 48 in all.
"Conventional telescopes are good at finding small, faint objects. Ours is really good at finding large ones," said Abraham.
Indeed, over the last few years Dokkum and Abraham have used it to uncover a whole new category of sparsely populated "ultra diffuse galaxies" -- and sparked a cottage industry as astronomers struggle to explain their strange properties.
"Everything about them is a surprise, starting with the very fact they exist," Abraham said.
Up to now, the analysis of galaxies has shown a fairly tight ratio of dark to ordinary matter. But this new class "is breaking all the rules," he said.
The first anomalies discovered were galaxies almost entirely composed of dark matter. That was odd enough.
But the real shocker was DF2, which has virtually none at all.
An 'OMG' moment -
DF2 was first identified by Russian astronomers conducting a photographic survey, but it's uniqueness didn't come to light until later.
Dokkum's team used the Keck telescopes in Hawaii to track the motion of several star clusters -- each with about 100,000 stars -- within the galaxy.
The clusters, they found, travelled at the same speed as the galaxy, itself moving through the Universe. Had there been dark matter, the clusters would be moving slower or faster.
Abrahams recalls seeing the graphic plot showing the motion of DF2's constellations for the first time, and wondering if something was amiss.
"We asked ourselves where we had screwed up, if the measurements were wrong," he said.
"Then I suddenly realised the implications. That's as close to an 'Oh My God' moment as I got."
A galaxy entirely bereft of dark matter raises vexing questions that, so far, have stumped astronomers.
"It challenges the standard ideas of how we think galaxies work," said Dokkum.
Figuring out how something as big as a galaxy is held together without dark matter will be difficult, but understanding how it formed in the first place will be even harder, he said.
Whatever the explanation, a galaxy with no dark matter poses an ironic challenge to astronomers who question the very existence of the substances, according to the study.... | 0.810549 | 3.815741 |
Imagine if you will that your name would forever be associated with a groundbreaking scientific theory. Imagine also that your name would even be attached to a series of units, designed to performs measurements for complex equations. Now imagine that you were German who lived through two World Wars, won the Nobel Prize for physics, and outlived many of your children.
If you can do all that, then you might know what it was like to be Max Planck, the German physicist and founder of quantum theory. Much like Galileo, Newton, and Einstein, Max Planck is regarded as one of the most influential and groundbreaking scientists of his time, a man whose discoveries helped to revolutionized the field of physics. Ironic, considering that when he first embarked on his career, he was told there was nothing new to be discovered!
Early Life and Education:
Born in 1858 in Kiel, Germany, Planck was a child of intellectuals, his grandfather and great-grandfather both theology professors and his father a professor of law, and his uncle a judge. In 1867, his family moved to Munich, where Planck enrolled in the Maximilians gymnasium school. From an early age, Planck demonstrated an aptitude for mathematics, astronomy, mechanics, and music.
He graduated early, at the age of 17, and went on to study theoretical physics at the University of Munich. In 1877, he went on to Friedrich Wilhelms University in Berlin to study with physicists Hermann von Helmholtz. Helmholtz had a profound influence on Planck, who he became close friends with, and eventually Planck decided to adopt thermodynamics as his field of research.
In October 1878, he passed his qualifying exams and defended his dissertation in February of 1879 – titled “On the second law of thermodynamics”. In this work, he made the following statement, from which the modern Second Law of Thermodynamics is believed to be derived: “It is impossible to construct an engine which will work in a complete cycle, and produce no effect except the raising of a weight and cooling of a heat reservoir.”
For a time, Planck toiled away in relative anonymity because of his work with entropy (which was considered a dead field). However, he made several important discoveries in this time that would allow him to grow his reputation and gain a following. For instance, his Treatise on Thermodynamics, which was published in 1897, contained the seeds of ideas that would go on to become highly influential – i.e. black body radiation and special states of equilibrium.
With the completion of his thesis, Planck became an unpaid private lecturer at the Freidrich Wilhelms University in Munich and joined the local Physical Society. Although the academic community did not pay much attention to him, he continued his work on heat theory and came to independently discover the same theory of thermodynamics and entropy as Josiah Willard Gibbs – the American physicist who is credited with the discovery.
In 1885, the University of Kiel appointed Planck as an associate professor of theoretical physics, where he continued his studies in physical chemistry and heat systems. By 1889, he returned to Freidrich Wilhelms University in Berlin, becoming a full professor by 1892. He would remain in Berlin until his retired in January 1926, when he was succeeded by Erwin Schrodinger.
Black Body Radiation:
It was in 1894, when he was under a commission from the electric companies to develop better light bulbs, that Planck began working on the problem of black-body radiation. Physicists were already struggling to explain how the intensity of the electromagnetic radiation emitted by a perfect absorber (i.e. a black body) depended on the bodies temperature and the frequency of the radiation (i.e., the color of the light).
In time, he resolved this problem by suggesting that electromagnetic energy did not flow in a constant form but rather in discreet packets, i.e. quanta. This came to be known as the Planck postulate, which can be stated mathematically as E = hv – where E is energy, v is the frequency, and h is the Planck constant. This theory, which was not consistent with classical Newtonian mechanics, helped to trigger a revolution in science.
A deeply conservative scientists who was suspicious of the implications his theory raised, Planck indicated that he only came by his discovery reluctantly and hoped they would be proven wrong. However, the discovery of Planck’s constant would prove to have a revolutionary impact, causing scientists to break with classical physics, and leading to the creation of Planck units (length, time, mass, etc.).
By the turn of the century another influential scientist by the name of Albert Einstein made several discoveries that would prove Planck’s quantum theory to be correct. The first was his theory of photons (as part of his Special Theory of Relativity) which contradicted classical physics and the theory of electrodynamics that held that light was a wave that needed a medium to propagate.
The second was Einstein’s study of the anomalous behavior of specific bodies when heated at low temperatures, another example of a phenomenon which defied classical physics. Though Planck was one of the first to recognize the significance of Einstein’s special relativity, he initially rejected the idea that light could made up of discreet quanta of matter (in this case, photons).
However, in 1911, Planck and Walther Nernst (a colleague of Planck’s) organized a conference in Brussels known as the First Solvav Conference, the subject of which was the theory of radiation and quanta. Einstein attended, and was able to convince Planck of his theories regarding specific bodies during the course of the proceedings. The two became friends and colleagues; and in 1914, Planck created a professorship for Einstein at the University of Berlin.
During the 1920s, a new theory of quantum mechanics had emerged, which was known as the “Copenhagen interpretation“. This theory, which was largely devised by German physicists Neils Bohr and Werner Heisenberg, stated that quantum mechanics can only predict probabilities; and that in general, physical systems do not have definite properties prior to being measured.
This was rejected by Planck, however, who felt that wave mechanics would soon render quantum theory unnecessary. He was joined by his colleagues Erwin Schrodinger, Max von Laue, and Einstein – all of whom wanted to save classical mechanics from the “chaos” of quantum theory. However, time would prove that both interpretations were correct (and mathematically equivalent), giving rise to theories of particle-wave duality.
World War I and World War II:
In 1914, Planck joined in the nationalistic fervor that was sweeping Germany. While not an extreme nationalist, he was a signatory of the now-infamous “Manifesto of the Ninety-Three“, a manifesto which endorsed the war and justified Germany’s participation. However, by 1915, Planck revoked parts of the Manifesto, and by 1916, he became an outspoken opponent of Germany’s annexation of other territories.
After the war, Planck was considered to be the German authority on physics, being the dean of Berlin Universit, a member of the Prussian Academy of Sciences and the German Physical Society, and president of the Kaiser Wilhelm Society (KWS, now the Max Planck Society). During the turbulent years of the 1920s, Planck used his position to raise funds for scientific research, which was often in short supply.
The Nazi seizure of power in 1933 resulted in tremendous hardship, some of which Planck personally bore witness to. This included many of his Jewish friends and colleagues being expelled from their positions and humiliated, and a large exodus of Germans scientists and academics.
Planck attempted to persevere in these years and remain out of politics, but was forced to step in to defend colleagues when threatened. In 1936, he resigned his positions as head of the KWS due to his continued support of Jewish colleagues in the Society. In 1938, he resigned as president of the Prussian Academy of Sciences due to the Nazi Party assuming control of it.
Despite these evens and the hardships brought by the war and the Allied bombing campaign, Planck and his family remained in Germany. In 1945, Planck’s son Erwin was arrested due to the attempted assassination of Hitler in the July 20th plot, for which he was executed by the Gestapo. This event caused Planck to descend into a depression from which he did not recover before his death.
Death and Legacy:
Planck died on October 4th, 1947 in Gottingen, Germany at the age of 89. He was survived by his second wife, Marga von Hoesslin, and his youngest son Hermann. Though he had been forced to resign his key positions in his later years, and spent the last few years of his life haunted by the death of his eldest son, Planck left a remarkable legacy in his wake.
In recognition for his fundamental contribution to a new branch of physics he was awarded the Nobel Prize in Physics in 1918. He was also elected to the Foreign Membership of the Royal Society in 1926, being awarded the Society’s Copley Medal in 1928. In 1909, he was invited to become the Ernest Kempton Adams Lecturer in Theoretical Physics at Columbia University in New York City.
He was also greatly respected by his colleagues and contemporaries and distinguished himself by being an integral part of the three scientific organizations that dominated the German sciences- the Prussian Academy of Sciences, the Kaiser Wilhelm Society, and the German Physical Society. The German Physical Society also created the Max Planck Medal, the first of which was awarded into 1929 to both Planck and Einstein.
The Max Planck Society was also created in the city of Gottingen in 1948 to honor his life and his achievements. This society grew in the ensuing decades, eventually absorbing the Kaiser Wilhelm Society and all its institutions. Today, the Society is recognized as being a leader in science and technology research and the foremost research organization in Europe, with 33 Nobel Prizes awarded to its scientists.
In 2009, the European Space Agency (ESA) deployed the Planck spacecraft, a space observatory which mapped the Cosmic Microwave Background (CMB) at microwave and infra-red frequencies. Between 2009 and 2013, it provided the most accurate measurements to date on the average density of ordinary matter and dark matter in the Universe, and helped resolve several questions about the early Universe and cosmic evolution.
Planck shall forever be remembered as one of the most influential scientists of the 20th century. Alongside men like Einstein, Schrodinger, Bohr, and Heisenberg (most of whom were his friends and colleagues), he helped to redefine our notions of physics and the nature of the Universe.
We have written many articles about Max Planck for Universe Today. Here’s What is Planck Time?, Planck’s First Light?, All-Sky Stunner from Planck, What is Schrodinger’s Cat?, What is the Double Slit Experiment?, and here’s a list of stories about the spacecraft that bears his name.
We’ve also recorded an entire episode of Astronomy Cast all about Max Planck. Listen here, Episode 218: Max Planck. | 0.840532 | 3.026515 |
The idea of a galactic habitable zone (GHZ) has a certain inevitability. After all, we talk about habitable zones around stars, so why not galaxies? A stellar habitable zone is usually considered to refer to those areas around the star where liquid water can exist on a planetary surface. Those who believe that confining habitable zones to regions like these carries an implicit bias — limiting them to life much like our own — miss the point. The habitable zone concept simply tells us where it makes the most sense to search for the kind of life we can most readily recognize, and as such, it hardly rules out other, more exotic forms of life.
But while liquid water takes precedence in a stellar habitable zone, a galactic HZ is still being defined. Charles Lineweaver and team have examined it, among other things, in terms of stellar metallicity (the elements heavier than hydrogen and helium found in the body of a star), concluding that there is a ring several kiloparsecs wide surrounding galactic center in which life would be most likely to be found. But the ring evolves, spreads outwards with time, leaving us to recognize that galactic habitable zones can vary over the eons.
Image: A computer simulation showing the development and evolution of the disk of a galaxy such as the Milky Way. Credit: Rok Roškar/University of Washington.
That evolution now gets a much closer look from a team at the University of Washington, which ran 100,000 hours of computer simulations to study how galactic disks evolve, beginning with conditions nine billion years ago. The resultant data show that the average star can migrate through the galaxy, thus skewing the results of any habitable zone based partly on the abundance of certain chemical elements necessary for life. UW graduate student Rok Roškar puts the case this way:
“Our view of the extent of the habitable zone is based in part on the idea that certain chemical elements necessary for life are available in some parts of a galaxy’s disk but not others. If stars migrate, then that zone can’t be a stationary place.”
Stellar migration comes in handy because our understanding of the relationship between age and metallicity across star populations is changing. The paper on this work explains that relationship in terms of galactic chemical evolution:
Stars of the same age in the same general region of the galaxy are… expected to have similar metallicities. Indeed, early determinations of the AMR [age-metallicity relationship] confirmed that the mean trend of stars in the solar neighborhood is toward lower metallicity with increasing age. Models, which assume that stars remain where they are born and return their nucleosynthetic yields to their local ISM [interstellar medium], typically successfully reproduce this trend.
All of which gets interesting when you consider that in the part of the galaxy in which the Sun resides, field stars and open clusters show a wide range of metallicities. The ‘scatter’ in these data implies that stars near the Sun may well have come from completely different parts of the galaxy. The findings from the simulated galaxy are clear:
Roughly 50% of all “solar neighborhood” stars have come from elsewhere, primarily from the disk interior. Interestingly, some metal poor stars have been scattered into the solar neighborhood from the outer part of the disk. Such migration has recently been inferred from observational data… Metal-rich stars, like our Sun, could have originated almost anywhere in the Galaxy.
We just looked at the question of the Sun’s siblings, and whether or not systems forming in the same early cluster as the Sun might have exchanged life-bearing materials. Tracing stellar movements back in time to reveal which stars comprise those siblings may be a tricky matter. Stars encountering a galactic spiral arm seem to retain the circularity of their orbits after such an encounter, but their orbits may change considerably in size, meaning the Sun could have been in a much different position in relation to galactic center when it formed than it is today.
Bear in mind that galactic habitable zones also factor in supernovae explosions, which could cause exterminations on nearby worlds. We have much to learn in the study of supernovae, but the UW simulations suggest that the GHZ may be a more flexible area than we have previously considered. The paper is Roškar et al., “Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks,” accepted for publication in Astrophysical Journal Letters (abstract). The earlier Charles Lineweaver paper is “The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way,” Science Vol. 303, No. 5654 (2 January 2004), pp. 59-62, with abstract here. | 0.838787 | 4.072988 |
In the far reaches of the Photo voltaic Procedure, previous the orbit of Neptune, items start off having trickier and trickier to see. Right imaging compact objects out in the darkness of the Kuiper Belt – where by Pluto resides – is genuinely tricky, which can make a current discovery all the additional remarkable.
If you know where by some thing is, you can observe it by waiting around for it to move in front of distant stars. This is called occultation, and astronomers use it to review all kinds of trans-Neptunian objects.
But when astronomers utilized occultation in 2018 to review one particular these kinds of object they have been seeing for virtually two decades, they found some thing genuinely unanticipated – a chonk of a moon, relative to the human body it is orbiting. A review describing their conclusions has now been recognized into Astronomy & Astrophysics, and was initial lined by Jonathan O’Callaghan in excess of at New Scientist.
The object caught sporting this moon is possible dwarf earth (84522) 2002 TC302. It was initial uncovered in 2002, right after which it was also identified in earlier observations.
Amongst 2000 and 2018, astronomers collected at the very least 126 observations of the object throughout a assortment of wavelengths (which includes the Hubble Space Telescope) employing this facts, they calculated the probable dwarf planet’s orbit, sizing, and color.
They found that it really is all over 584 kilometres (363 miles) in diameter, and with an orbital period of 417 several years – in a two:five orbital resonance with Neptune.
That is fairly brilliant. It implies 2002 TC302 nearly satisfies the prerequisites for a dwarf earth – it really is in orbit all over the Sunshine (but not an additional earth) it has not cleared its orbital neighbourhood and it must have more than enough mass to attain hydrostatic equilibrium, or a round condition.
But we’re not fairly certain. When predictions of its orbit pointed to an occultation function on 28 January 2018, observatories all over Europe pointed their eyes at 2002 TC302‘s neighbourhood to attempt and determine out its actual physical qualities, these kinds of as sizing and condition.
Telescopes in Italy, France, Slovenia and Switzerland produced 12 beneficial detections of the occultation function, as perfectly as four detrimental detections. This created the greatest observation of a trans-Neptunian object we’ve acquired to day, the researchers reported.
Adding these together permitted the researchers to obtain a new, additional precise measurement of the object’s diameter: five hundred kilometres (311 miles).
So, how to account for the lacking eighty four kilometres calculated from the other observations? Effectively, there’s a genuinely appealing reply to that. If 2002 TC302 had a moon all over 200 kilometres (124 miles) in diameter, and just two,000 kilometres (one,243 miles) from the possible dwarf earth, it could develop the sign that other astronomers interpreted as a a bit larger sized 2002 TC302.
This is nuts shut. The Moon, for context, is 384,four hundred kilometres (238,900 miles) from Earth (on average). At these kinds of a shut proximity, 2002 TC302‘s satellite would be very really hard to impression – not even the Hubble Space Telescope photographs taken in 2005 would be capable to take care of it individually.
If the probable dwarf earth genuinely has a satellite, that can aid us study items about the early Photo voltaic Procedure. Stuff in the Kuiper Belt has adjusted pretty very little given that the Photo voltaic Procedure fashioned, and as these kinds of, these objects are viewed as time capsules.
Two objects very shut together could aid us to improved fully grasp shut interactions when the Photo voltaic Procedure was forming. Due to the fact the planets are considered to have fashioned through accretion – additional and additional stuff sticking together – this could be an essential clue as to how scaled-down bodies grow.
An object of very similar curiosity is Arrokoth, the odd snowman-shaped rock visited by the New Horizons probe in 2015. The info provided by that flyby confirmed us that planetary accretion may well be a additional gentle procedure than we considered.
2002 TC302 is a great deal larger than Arrokoth, but it could be at a later stage of the procedure – which would be genuinely useful in piecing together the levels in which it transpires. At any amount, it really is distinct that we should really in all probability glance at it a bit additional and attempt to determine out what its deal is. Exciting!
The exploration has been recognized into Astronomy & Astrophysics, and is available on arXiv. | 0.876357 | 3.832289 |
Press release: 11 August 2010
Astronomers have captured a spectacular new image in a region of our neighbouring galaxy known to have an abnormally high rate of star formation that reveals yet more details about its history and development. The picture, taken with the UK-designed and built VISTA (Visible and Infrared Survey Telescope for Astronomy) telescope, is of the Tarantula Nebula, a region in the Large Magellanic Cloud which contains many stars that can be difficult to detect because they are enshrouded in the gas and dust clouds from which they formed. Astronomers were able to take the image by using ESO (link opens in a new window)’s (European Southern Observatory) VISTA telescope because it can pick up near infra-red light, which we cannot see ourselves, that has a longer wavelength of visible light, enabling it to penetrate much of the dust that would normally obscure our view.
VISTA Magellanic Cloud Survey view of the Tarantula NebulaCredit:ESO
The leader of the survey team, Maria-Rosa Cioni (University of Hertfordshire, UK) explains: "This view is of one of the most important regions of star formation in the local Universe — the spectacular 30 Doradus star-forming region, also called the Tarantula Nebula. At its core is a large cluster of stars called RMC 136, in which some of the most massive stars known are located."
The wide-field image shows a host of different objects. The bright area above the centre is the Tarantula Nebula itself, with the RMC 136 cluster of massive stars in its core. To the left is the NGC 2100 star cluster. To the right is the tiny remnant of the supernova SN1987A. Below the centre are a series of star-forming regions including NGC 2080 — nicknamed the “Ghost Head Nebula” — and the NGC 2083 star cluster.
The VISTA project was managed by The Science and Technology Facilities Council’s (STFC) UK Astronomy Technology Centre (UKATC) and the camera was constructed by STFC's Rutherford Appleton Laboratory. Professor Ian Robson, Head of UKATC said; “We are very proud of the wealth of data that the VISTA telescope is producing for the astronomical community; the spectacular images are not only telling us about new science, but look absolutely fantastic”.
The picture has been taken as part of ESO’s VISTA Magellanic Cloud (VMC) survey which will scan an area nearly a thousand times the apparent area of the full moon (184 square degrees). Chris Evans from the VMC team said; “The VISTA images will allow us to extend our studies beyond the inner regions of the Tarantula into the multitude of smaller stellar nurseries nearby, which also harbour a rich population of young and massive stars. Armed with the new, exquisite infrared images, we will be able to probe the cocoons in which massive stars are still forming today, while also looking at their interaction with older stars in the wider region.”
The VMC Survey is one of six huge near-infrared surveys of the southern sky that will take up most of the first five years of operations of VISTA.
STFC allows UK astronomers access to ESO’s telescopes through a subscription.
More details can be found on ESO’s Press Release (link opens in a new window).
Notes to editors
Images are available, please see ESO's Press Release (link opens in a new window) for more details.
- Lucy Stone
STFC Press Officer
Rutherford Appleton Laboratory
Tel: +44 (0)1235 445 627
Mob: +44 (0)7920 870 125
VISTA is a 4m diameter telescope based in Chile operating at Infrared wavelengths. It was provided by the UK to the European Southern Observatory (ESO) as an in-kind contribution and part of the UK’s joining fee.
Even before being formally handed over to ESO at the end of 2009 VISTA was used for two detailed studies of small sections of the sky before it embarked on the much larger surveys that are now in progress. One of these “Science Verification surveys” was a detailed study of the Sculptor Galaxy and its environment.
Further information about VISTA can be found on ESO's telescope pages (link opens in a new window).
VISTA is a £37 million project, funded by grants from the DTI's (now Department for Business Innovation and Skills (BIS)) Joint Infrastructure Fund and the STFC to Queen Mary, University of London, the lead institute of the VISTA consortium. VISTA was project managed by STFC's UK Astronomy Technology Centre. The camera was constructed by STFC’s Rutherford Appleton Laboratory.
The VISTA consortium consists of:
- Queen Mary University of London
- Queen’s University of Belfast
- University of Birmingham
- University of Cambridge
- Cardiff University
- University of Central Lancashire
- Durham University
- The University of Edinburgh
- University of Hertfordshire
- Keele University
- Leicester University
- Liverpool John Moores University
- University of Nottingham
- University of Oxford
- University of St Andrews
- University of Southampton
- University of Sussex
- University College London
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research.
ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA (Atacama Large Millimetre Array), the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
For more information please contact: RAL Space Enquiries | 0.849138 | 3.739764 |
Both push and pull drive our Galaxy’s race through space
January 31, 2017
Discovery of the “Dipole Repeller” confirms that both attraction and repulsion are at play in our extragalactic neighborhood
Jerusalem, January 30, 2017 — Although we can’t feel it, we’re in constant motion: the earth spins on its axis at about 1,600 km/h; it orbits around the sun at about 100,000 km/h; the sun orbits our Milky Way galaxy at about 850,000 km/h; and the Milky Way galaxy and its companion galaxy Andromeda are moving with respect to the expanding universe at roughly 2 million km/h (630 km per second). But what is propelling the Milky Way’s race through space?
Until now, scientists assumed that a dense region of the universe is pulling us toward it, in the same way that gravity made Newton’s apple fall to earth. The initial “prime suspect” was called the Great Attractor, a region of a half dozen rich clusters of galaxies 150 million lightyears from the Milky Way. Soon after, attention was drawn to an area of more than two dozen rich clusters, called the Shapley Concentration, which sits 600 million lightyears beyond the Great Attractor.
Now researchers led by Prof. Yehuda Hoffman at the Hebrew University of Jerusalem report that our galaxy is not only being pulled, but also pushed. In a new study in the forthcoming issue of Nature Astronomy, they describe a previously unknown, very large region in our extragalactic neighborhood. Largely devoid of galaxies, this void exerts a repelling force on our Local Group of galaxies.
“By 3-d mapping the flow of galaxies through space, we found that our Milky Way galaxy is speeding away from a large, previously unidentified region of low density. Because it repels rather than attracts, we call this region the Dipole Repeller,” said Prof. Yehuda Hoffman. “In addition to being pulled towards the known Shapley Concentration, we are also being pushed away from the newly discovered Dipole Repeller. Thus it has become apparent that push and pull are of comparable importance at our location.”
PHOTOS and VIDEO are available at http://irfu.cea.fr/dipolerepeller. Use of these materials is permitted on condition of respecting the publication embargo and including the proper credit information.
The presence of such a low density region has been suggested previously, but confirming the absence of galaxies by observation has proved challenging. But in this new study, Hoffman, at the Hebrew university’s Racah Institutes of Physics, working with colleagues in the USA and France, tried a different approach.
Using powerful telescopes, among them the Hubble Space Telescope, they constructed a 3-dimensional map of the galaxy flow field. Flows are direct responses to the distribution of matter, away from regions that are relatively empty and toward regions of mass concentration; the large scale structure of the universe is encoded in the flow field of galaxies. They studied the peculiar velocities – those in excess of the Universe’s rate of expansion – of galaxies around the Milky Way, combining different datasets of peculiar velocities with a rigorous statistical analysis of their properties. They thereby inferred the underlying mass distribution that consists of dark matter and luminous galaxies — over-dense regions that attract and under-dense ones that repel.
By identifying the Dipole Repeller, the researchers were able to reconcile both the direction of the Milky Way’s motion and its magnitude. They expect that future ultra-sensitive surveys at optical, near-infrared and radio wavelengths will directly identify the few galaxies expected to lie in this void, and directly confirm the void associated with the Dipole Repeller.
Hoffman’s collaborators include Daniel Pomarède, Institut de Recherche sur les Lois Fondamentales de l’Univers, CEA, Université Paris-Saclay, Gif-sur-Yvette, France; R. Brent Tully, Institute for Astronomy (IFA), University of Hawaii, USA; and Hélène M. Courtois, IPN Lyon, University of Lyon, France.
CITATION: The dipole repeller. Yehuda Hoffman, Daniel Pomarède, R. Brent Tully and Hélène M. Courtois. Nature Astronomy, Advance Online Publication January 30, 2017. doi: 10.1038/s41550-016-0036
SUPPORT: The researchers thank the Israel Science Foundation (1013/12), the Institut Universitaire de France, the US National Science Foundation, Space Telescope Science Institute (for Observations with Hubble Space Telescope), the Jet Propulsion Lab (for observations with Spitzer Space Telescope) and NASA (for analysis of data from the Wide-field Infrared Survey Explorer).
To contact the researchers: Prof. Yehuda Hoffman, Racah Institute of Physics, The Hebrew University of Jerusalem, +972 54 575 3900, [email protected] | 0.847223 | 3.622681 |
This was first published on the now-retired polarcosmology.com website, a companion site for the book North: The Rise & Fall of the Polar Cosmos by Gyrus – an epic, animism-infused history of cosmology. Check out more information, or buy from Strange Attractor Press.
In this essay I’d like to discuss the thesis championed by Romanian historian of religion, Mircea Eliade: that one of the most primal and universal elements of human cosmology is the axis mundi, the idea of a cosmic axis around which everything — both literally and metaphorically — revolves. This axis is seen as the umbilical cord which connects our mundane material realm to the higher strata of sacred power.
Before we look into the depth of this image’s history, we can appreciate its significance better by looking at the symbolic cultural impact of the Copernican Revolution. In seventeenth-century Europe it became clear that Earth isn’t the centre of the cosmos, as was previously assumed. The axis mundi was never precisely equated with the literal axis of Earth, but there was always a heavy overlap between the imaginal and literal axes. So when the literal axis was shown merely to be the axis of Earth’s rotation — and not the axis of the whole cosmos, centred on Earth — the status of the imaginal axis suffered greatly. Its unseating was the prime symbolic aspect of the wider challenge to spiritual cosmology mounted by increasingly materialist science. For Eliade, and the Traditionalist school of thought which he often echoes, the Copernican Revolution’s literal impact on astronomical science was dwarfed by its symbolic impact on the ancient cosmology which hinged on this idea of the axis mundi.
There were two intimately related shifts involved in this revolution, which served to severely undermine the axis and the centralised, hierarchical vision of the cosmos it epitomised. If we look at the impact of these shifts, we’ll be in a better position to appreciate why the ancient geocentric cosmology was so important to Eliade, and why he was so convinced that it stretched all the way to the origins of human culture.
Firstly, there was the decentralisation initiated by the Copernican argument that the cosmos did not — despite appearances — revolve around our humble earthly home. This decentralisation wasn’t unequivocal. The radically decentred vision of an infinite universe in which every star is a sun — championed before Copernicus by Nicholas of Cusa, and after Copernicus by Giordano Bruno — was too much for most to take on board. Our new local centre, the sun, inherited much of the symbolic power of the ancient image of the cosmic axis transpiercing Earth. Royalty’s social centrality easily became ‘solar’, as Louis XIV demonstrated. Also, the flourishing of humanism in the centuries after Copernicus showed that while our home may have lost its cosmic pre-eminence, we were very capable of retaining our own centrality. All the same, the destabilisation of the old polar cosmos, with Earth as its absolute centre, caused great shockwaves in the psychic depths of Europe.
Alongside this, the work of Galileo and Newton ended another venerable certainty. Since ancient Greece, at least, civilised philosophers had seen the space of the heavens above as being fundamentally, qualitatively of a different order from the space of Earth below. The divine bodies in the sky seemed to move in circles, in their eternal, unchanging rounds. But let go of a lowly material object here, and it moved in a line, straight down — and then decayed or eroded in its resting place. All vitality in terrestrial bodies was seen as being sourced in the Empyrean — the radiant home of divinity beyond the sphere of the fixed stars — and channelled down to the otherwise moribund sublunary realm via networks of correspondence. But Galileo’s telescope confirmed dark rumours of the unthinkable — change in the heavens, a star appearing where previously there was no star. Later, Newton’s work on universal gravitation supplied an explanatory framework for both the motion of heavenly bodies and falling bodies here on Earth. Even more than the Copernican decentralisation, this Newtonian collapse of the cosmic hierarchy profoundly upset the ambient order of European society.
Briefly, for some — such as the Diggers, Levellers, and other radical nonconformists in the English Civil War — this decentralisation and collapse acted to spread the divinity which had been hoarded in the empyreal heights back across the earthly plane. This symbolic spread was both mirrored in and reflective of their call for egalitarian distribution of power previously hoarded by elites. For an increasing number of other people, the loss of a fundamental separation of above and below signalled the banishment of divinity itself. A new, homogeneous, purely material world was heralded — perhaps a liberation from old superstitions, perhaps a descent into a barren wasteland of nihilism.
In any case, the old spatial division between Heaven and Earth gave way to a new temporal division between ‘traditional’ and ‘modern’ — with the former realm of spiritual glory cast as superstitious and fusty, and the latter cast as a thrilling new realm of freedom and power. And in the wake of the Darwinian revolution, which further cemented the unfamiliar new cosmic order (or lack of order), there was an inevitable backlash which tried to salvage the psychic reassurances of the ancient polar cosmos. Spiritualist communication with the dead and fundamentalist dogmatism about the word of God are instances of this backlash in the popular sphere. Among intellectuals reacting against the modern onslaught, Traditionalism and its fringes sought to justify a new valorisation of the ancient order of things.
Legitimate concerns about the alienating impacts of modernity naturally became enmeshed with a nostalgia for the old geocentric cosmology — not necessarily in a denial of new astronomical realities, but in an attempt to downplay the importance of mere physics, and to revive the life of the spirit which still, in its embodied relation to the lived world, saw the stars turning around the celestial pole, and felt the apparent concentricity of the cosmos to be an imaginal grounding for the psyche. Henry Corbin, a philosopher and theologian greatly concerned with the cosmologies of esoteric Islam, thought that just as alchemy could and should be liberated by esotericism from a view of it as a primitive precursor to modern chemistry, geocentrism should likewise be set free from its status as a relic in the history of science.
Considering the perception of the world and the feeling of the universe on which it is based, it may be that geocentrism should be meditated upon and evaluated essentially after the manner of the construction of a mandala.
It is this mandala upon which we should meditate in order to find again the northern dimension with its symbolic power, capable of opening the threshold of the beyond. This is the North which was ‘lost’ when, by a revolution of the human presence, a revolution of the mode of presence in the world, the Earth was ‘lost in the heavens’.1
Corbin became a prominent member of Carl Jung’s Eranos discussion group in Switzerland in the middle of the twentieth century. Corbin’s call for a return to an ‘imaginal geocentrism’ of course resonated with Jung’s obsession with the mandala as an image of the Self. And this deep concern for the pre-eminence of the centre was also shared by another important Eranos attendee: Mircea Eliade.
Eliade’s work, hugely influential on the late twentieth-century revival of paganism and occultism, was overwhelmingly concerned with what he terms the axis mundi — the axis of the world as an image of connection between the mundane terrestrial plane and the transcendent home of the spirit above. Eliade saw the motif of the separation of Heaven and Earth in creation myths as a primary truth, signalling — like the Biblical expulsion from Eden — a fundamental alienation from the primordial unity of spiritual being. Consequently, people could only maintain their connection to the spiritual sources of meaning through an imaginal conduit, a bond between Heaven and Earth which became implicitly present in religious ritual, and which was embodied architecturally in important temples and sacred sites. The symbolic impact of the Copernican Revolution, then, was devastating. At once it literalised the axial sense of the world, dismissing its symbolic weight, and then demolished the axis in any case, revealing it to be an illusion of the naive senses. Bound up in this symbolic devastation were all the spiritual agony and ennui of modern humanity — perilously cut off from its grounding it transcendent spirit.
Eliade found evidence for this axis mundi across the ancient world, and throughout the documentation of traditional peoples — which was steadily mounting in Western libraries, and which he consumed voraciously. He was especially taken by ethnographies of Aboriginal Australians — for him, ‘true primitives’ whose isolation on their island continent seemed to be an assurance that their culture preserved genuine, living evidence of the very earliest human notions.2
One report of Aborigine beliefs served to root Eliade’s conviction of the primacy of an sky- and axis-orientated cosmos in the deepest strata of our species’ culture. Eliade first wrote of this in 1957’s The Sacred and the Profane:
According to the traditions of an Arunta tribe, the Achilpa [Tjilpa], in mythical times the divine being Numbakula cosmicized their future territory, created their Ancestor, and established their institutions. From the trunk of a gum tree Numbakula fashioned the sacred pole (kauwa-auwa) and, after anointing it with blood, climbed it and disappeared into the sky. This pole represents the cosmic axis, for it is around the sacred pole that territory becomes habitable, hence is transformed into a world. The sacred pole consequently plays an important role ritually. During their wanderings the Achilpa always carry it with them and choose the direction they are able to take by the direction toward which it bends. This allows them, while being continually on the move, to be always in ‘their world’ and, at the same time, in communication with the sky into which Numbakula vanished.3
The supreme importance of this pole couldn’t have been more forcefully impressed upon Eliade, confirming him in his convictions, than by the next ethnographic snippet:
For the pole to be broken denotes catastrophe; it is like ‘the end of the world,’ reversion to chaos. Spencer and Gillen report that once, when the pole was broken, the entire clan were in consternation; they wandered about aimlessly for a time, and finally lay down on the ground together and waited for death to overtake them.4
As Corbin was to write later:
The human person is only a person by virtue of this celestial dimension, archetypal, angelic, which is the celestial pole without which the terrestrial pole of this human dimension is completely depolarized in vagabondage and perdition.5
However, behind this apparent rooting of the polar cosmos in primal humanity lies a tangle of sloppy scholarship and prejudiced misunderstanding which can be taken as emblematic of the basic mistake of the Traditionalist project: a failure to understand the difference between Palaeolithic and Neolithic realities, between the world of hunter-gatherers and the world of farmers and city-dwellers.6
Jonathan Z. Smith, a historian of religion who studied with and succeeded Eliade at the University of Chicago, has pointed out that the account relied upon by Eliade — that of Australian anthropologists Walter James Spencer and Francis James Gillen — isn’t an account of present-day actions of the Achilpa tribe. Even at the start of the twentieth century, when Spencer and Gillen were collecting information on Aboriginal life, these people weren’t actually carrying a pole around to consecrate any place they set up camp. And they certainly weren’t lying down to die when the pole broke. Like Numbakula’s ascent into the sky, these events were mythical events, taking place in the Aboriginal ‘once upon a time’ epoch, the Dreaming.7 Eliade later corrected this mistake — but it isn’t the only problem.
In fact, the two stories — of Numbakula’s ascent and the significance of the pole — have been greatly telescoped together by Eliade. In Spencer and Gillen’s work, they are separated by thirty pages of other tales. Not only that, the two snippets are also separated by thirty years between their being gathered.8 Even admitting that these incidents are myths, there seems to be no reason for conflating them into an expression of Eliade’s dual concern with the separation of Heaven and Earth (Numbakula’s ascent up the pole) and the essential nature of the axis mundi (consternation at the breaking of the pole). They are particular incidents in a vast narrative cycle — not centrally important keys to the Aboriginal cosmos.
To make matters worse for Eliade’s position, Spencer and Gillen’s source material is riddled with problems. Neither of these anthropologists were fluent in the language of their informants, and they relied heavily on their informants’ imperfect English. What’s more, it seems that one of Spencer and Gillen’s informants, whose English name was Charlie Cooper, had been a police tracker for 15 years before they talked with him. He would have been quite well versed in what whites were interested in hearing from Aboriginals — what these believers in an all-important sky god wanted to hear (not an uncommon anthropological trap). Anthropologist Theodor Strehlow has suggested that Cooper was actually making stuff up for Spencer and Gillen. In turn, this accusation is embroiled in colonial power struggles: ‘Strehlow frequently criticized Spencer. The criticism was part of Strehlow’s defence of his missionary father, Carl Strehlow, whose work on the Arrernte was frequently attacked by Spencer.’9
Even if Strehlow was wrong about Cooper, Eliade’s use of these fragments — by painting them as constitutive of Aboriginal cosmology — was radically misjudged. As Smith points out, a more balanced, wider-ranging survey of Aboriginal myths finds that the usual pattern for the disappearance of ancestral figures like Numbakula ‘is not one of celestial withdrawal, but of terrestrial transformation and continued presence.’10 As is often the case, the particulars of this story serve to memorialise the ancestor in a landscape feature. Here, the breaking of the pole is not significant in itself — it merely serves to account for a specific tall stone, the ‘broken end’ of the pole. The focus is not on the loss of something into the sky, but on the continued presence of something on the land. Thus, Smith concludes:
The horizon of the Tjilpa myth is not celestial, it is relentlessly terrestrial and chthonic. The emphasis is not on the dramatic creation of the world out of chaos by transcendent figures, or on the ‘rupture’ between these figures and men. Rather, the emphasis is on transformation and continuity, on a world fashioned by terrestrial wanderings across the featureless, primeval surface of the earth.11
This is the only piece of evidence rallied by Eliade to demonstrate the primal nature of the vertically hierarchical, concentric cosmos, its occurrence among pre-agricultural people — and it demonstrates nothing of the sort.
Evidence of such cosmological thinking can be found here and there among hunter-gatherers. But even where we can discount the potential influence of bygone or nearby civilisations or pastoralists (which is rarely the case), as Smith points out, the question is ultimately one of emphasis. Hunter-gatherers are famously sensitive to the details of the world, and would no doubt notice the basic structure of the heavens, revolving around a central point (outside equatorial latitudes). But why would they care about it? As sensitive to symbolism as any archaic people, why would these generally egalitarian nomads feel the need to emphasise and mythologise this structure of elevated immobility? Isn’t this natural structure more appealing to societies organised around a singular all-powerful leader? Isn’t the axis mundi generally the province of cultures under the sway of chiefs and kings? Smith’s conclusion is clear:
The language of ‘center’ is preeminently political and only secondarily cosmological. It is a vocabulary that stems, primarily, from archaic ideologies of kingship and the royal function.12
The basic mistake of Eliade, then, and of the Traditionalist school, was that they weren’t ‘traditional’ enough. In their efforts to establish their obsession with centralised cosmic hierarchy in the roots of human being, they projected the concerns of pre-modern agricultural myth — which is profoundly geared toward images of political stratification — back onto the pre-agricultural world of the hunter-gatherer. And this world was the entire human world until very recently — for more than 90% of our species’ existence. A true traditionalism would need to go beyond the narrow, constructed ‘naturalness’ of hierarchical society, and embrace our complex and diverse history — in which the decentred and fluid cosmos of mobile hunter-gatherers figures prominently.
The Copernican Revolution, then, rather than being a tragic loss of primal orientation, is in fact an ongoing opportunity to do what we did to survive the vast stretch of millennia before civilisation: forge new orientations to adapt to changing circumstances. New orientations, no longer fettered by the mundane patterns of power which have so successfully painted themselves in the colours of the sacred. | 0.826907 | 3.45342 |
Near the end of World War II, Allied pilots were startled by a new German fighter plane. It had no propeller, flew with a deep roar, and flashed through the air at a speed of more than 500 miles (800 kilometers) per hour. This amazing airplane was a jet-propelled Messerschmitt Me-262.
Today jet fighters fly through the stratosphere more swiftly than sound. Jet airliners fly higher, faster, and farther than ever before.
Jet propulsion speeds missiles to their targets (see guided missile). In addition, rockets boost Earth satellites into orbit.
Although most uses of jet propulsion have been for flight, it can also be applied to hydraulic jet propulsion for small, high-speed boats and pleasure craft. In such applications water is taken in at the forward end of the boat, compressed by high-pressure pumps, and discharged through a nozzle at the rear of the craft. The need for efficient pumps and the limitations of boat speeds have not made hydraulic jet propulsion an attractive or economic alternative to propeller-driven vessels.
Jet propulsion is the driving forward of a body by means of a jet of gas or fluid. The idea dates back to the 1st century ad when Hero of Alexandria built an engine called an aeolipile. He mounted a hollow metal globe with projecting tubes between two pipes so it could spin. Steam entered the globe through the pipes. As it escaped through the bent tubes, the jets of steam spun the globe.
Hero’s machine illustrates a scientific principle that Sir Isaac Newton formulated in 1687. Newton’s third law of motion states that for every action there is an equal and opposite reaction. In Hero’s machine the jets of steam escaping from the tubes are the action, the spinning of the globe the reaction. The same principle applies to jet engines, and for this reason they are called reaction engines.
Newton himself designed a jet-propelled carriage called Newton’s Wagon. A water-filled sphere was heated by fire, creating steam. A large nozzle projected back from the sphere. As the steam escaped from the nozzle, it propelled the wagon forward.
There are many everyday examples of jet propulsion. A blown-up toy balloon with its neck closed shows no tendency to move because the air inside is pressing equally in all directions. If the neck is opened suddenly, the balloon shoots away. The escaping air relieves pressure at the neck, and there is a reaction from the air opposite the neck. It is not the air rushing out of the neck and pushing against the outside air, however, that drives the balloon ahead. It is the air pushing against the inside front wall of the balloon that propels it forward. In fact, a jet would operate more efficiently in a vacuum because there would be no air to obstruct the escaping gases.
The recoil of a rifle also illustrates action and reaction. Expanding gases propel the bullet out of the barrel at high velocity. The rifle in response to the force of the gases “kicks back.” Another example of jet action is the garden hose whose nozzle jumps back when the water is suddenly turned on full force.
There are two general types of jet propulsion—air-breathing and nonair-breathing engines (see airplane). Air-breathing engines use oxygen from the atmosphere in the combustion of fuel. They include the turbojet, turboprop, ramjet, and pulse-jet. The term jet is generally used only in reference to air-breathing engines.
Nonair-breathing engines carry an oxygen supply. They can be used both in the atmosphere and in outer space. They are commonly called rockets and are of two kinds—liquid-propellant and solid-propellant.
Air-breathing engines may be further divided into two groups, based on the way in which they compress air for combustion. The turbojet and turboprop each has a compressor, usually turbine-driven, to take in air. They are called gas-turbine engines. The ramjet and the pulse-jet do not have compressors.
The most widely used air-breathing engine is the turbojet. After the air is drawn into the engine through an inlet, its pressure is first increased by a component called a compressor. The air then enters the combustion chamber, where it is burned with fuel to increase its temperature. The hot, high-pressure gas then expands through a wheel-like device called a turbine, where it produces power. The turbine is connected to the compressor by a shaft, and the power output of the turbine drives the compressor. At the turbine outlet the hot-gas pressure is still above that of the surroundings, and the final expansion takes place through an exhaust nozzle where the speed of the exhaust gas is increased. It is the final high-velocity jet that produces the thrust to push the plane through the air. Although in concept a jet engine is much simpler than a reciprocating engine that turns a propeller, the actual design for efficient operation is complex, and large jet engines are extremely costly.
Today almost all airborne jet engines utilize axial-flow compressors. In these devices the air flows generally in one direction along the shaft that connects the compressor and the turbine; it moves through alternate rows of stationary and rotating sets of blades called stators and rotors respectively. The blades are arranged so that the entering air is slowed while passing through them and its pressure increased. Modern axial-flow compressors can increase the pressure 25-fold in about 16 “stages,” each stage consisting of a set of rotor and stator blades.
Centrifugal compressors, which were used in early aircraft jet engines, take air in at the center of an impeller, or vaned wheel, and compress it in a radial, or outward, direction. Lower efficiencies, a limited pressure rise, and large diameters that add to the drag of the engine assembly now limit the use of centrifugal compressors to small engines and to non-flight applications.
When the air in a turbojet engine leaves the compressor and enters the combustion chamber, it is mixed with a finely atomized kerosene-like fuel and burned. In theory, for best performance the burning temperature should be as high as can be achieved from the complete combustion of the fuel and the oxygen in the air. This would, however, make the turbine inlet temperature much too high for operation, and at present turbine inlet temperatures are limited to about 1,900° to 2,200° F (1,040° to 1,200° C). The temperature is controlled by burning only part of the compressor discharge air, while the rest is diverted past the burning section and mixed with the high-temperature gases farther along the combustion chamber.
Combustion chambers can be composed of individual cans, or cylinders, arranged around the turbine shaft. Another approach is the use of an annular chamber in which a liner, or tubular sleeve, surrounds the shaft.
Special alloys that are both strong and lightweight are required in turbine blades in order to withstand the high temperatures and stresses there. Among those under study are combinations of metals and ceramics called cermets. Turbine blades can be cooled by diverting some of the unburned compressor air and feeding it through internal passages to small holes at the front, or leading edge, of the turbine blades. This provides a film of cool air that protects the blade wall from the hot gases.
High-pressure ratio engines are built with two shafts rotating within each other. The outer one is a high-speed shaft, which can operate at about 11,000 revolutions per minute (RPM). It connects the high-pressure turbine and compressor stages. The inner shaft, operating at about 3,000 RPM, connects a low-pressure turbine and compressor portions of the engine.
The greatest thrust would be obtained if the exhaust nozzle could expand the gas to the pressure of the surrounding air. However, a nozzle that is capable of doing this would be too large and heavy, and so the shorter nozzles that are used cause small losses in engine performance.
A turbojet engine cannot be started directly from rest. An external starting motor starts the unit spinning. The fuel is then ignited by a heated spark plug. Once the engine is running, combustion can be maintained without a spark plug.
The useful output of the turbojet is its thrust, which is proportional to the mass flow rate of air through the engine and the change in velocity between the exit and the inlet. (Mass flow rate is the mass of a fluid in motion that crosses a given area per unit of time.) This makes it desirable to achieve a high velocity at the nozzle exit.
Two performance characteristics are commonly used to describe turbojets: the specific thrust and the specific fuel consumption. The specific thrust produced (units of thrust per unit of engine gas flow per second) increases with the turbine inlet temperature. For this reason engineers continuously seek higher turbine inlet temperatures by means of improved materials and better blade cooling. The specific fuel consumption (unit of thrust produced per unit of fuel burned per second), which is lowered as the engine efficiency is increased, improves with increasing pressure ratio. This requires more and more compressor stages. In an actual jet engine there must be a trade-off between high pressures and high temperatures for best overall performance.
Another important performance factor of the turbojet engine is the in-flight propulsion efficiency. In this case, the best performance is obtained if the jet exit (from the nozzle) velocity is about twice the flight velocity of the aircraft. As the thrust is increased by raising the turbine inlet temperatures, the turbine exit velocity also increases and the jet exit velocity becomes too high. In such a case, propulsion performance can be increased by adding bypass air, as discussed later in this article.
Maximum thrust is usually required at takeoff, while maximum efficiency is desired at the aircraft’s cruising speed, which is about 500 to 550 miles (800 to 880 kilometers) per hour for most commercial airliners. For takeoff from a high-altitude airport on a hot summer day, the lower air density results in a lower mass flow rate of air through the engine and thus decreases the available thrust. In such a case, the plane may have to fly partially empty.
Since the combustion products leaving the turbine still have a large amount of oxygen contained in them (from the mixing of additional compressed air in the combustion chamber), it is possible to put another combustion chamber at the turbine exit. This so-called afterburner is used in some military aircraft to provide emergency bursts of speed. The fuel consumption in an afterburner is very high, however, so this thrust augmentation, or increase, is not practical for cruising or for commercial aircraft.
Water injection consists of introducing water into the compressor. This increases the thrust by cooling the air and thereby increasing both its density and the mass that can be passed for a given air velocity. Water injection can be used for emergency takeoff thrust, but the weight of water that is required to be carried on a plane does not make it desirable for in-flight operation.
As indicated above, it is desirable to have the average jet exit velocity about twice the air speed of the plane. A direct expansion of all the gases through the turbine would result in a jet velocity that would be too high for effective in-flight performance. Most modern aircraft jets now employ a turbofan, in which much of the air is only slightly compressed by a propeller-like compressor device at the front of the engine and then is passed around the engine core for mixing with the turbine exhaust gases, therefore bypassing the main engine. Bypass engines provide increased thrust for takeoff and climb, and they reduce jet noise. Modern engines may bypass five or six times the flow that goes through the engine core, and even higher bypass ratios are anticipated in the future for engines operating at higher turbine inlet temperatures.
In most commercial aircraft engines, the initial compression for both core and bypass flow is achieved by a large fan consisting of one or two compressor-like stages. After the flow has been divided, the core flow is further compressed, and the bypass flow is directed around the engine.
Turbojet engines tend to be noisy, which creates a problem in the neighborhood of airports. There is both a high-frequency noise, or whine, emanating from the compressor and a lower-frequency noise from the exit jet as it mixes with the surrounding air and produces turbulence. Compressor noise can be reduced by placing sound-absorbing material into the inlet ducting. The jet mixing noise is reduced by increasing the bypass air and by special mixers in the exhaust pipe. These mixers are corrugated to increase the area over which the hot and cool gases are in contact as they begin to mix.
At the tail of the engine is the thrust brake, or thrust reverser. This is a clamshell-like device activated by the pilot after landing. It closes over the jet exit nozzle to deflect the flow outward and slightly forward so that the thrust exerted on the plane is now backward, helping to brake the craft. With thrust reversers on, a jet plane can be made to roll backward on the ground.
The most serious problem a jet plane can encounter is the breaking off of a turbine or compressor blade if it is struck by a foreign object or if it breaks loose because of an internal engine failure. All engines must be designed with a casing strong enough to contain failing blades and to prevent a broken blade from cutting through the engine and damaging vital parts or from penetrating into the passenger space.
The most serious problem facing the compressor is posed by birds. All engines must be able to “swallow” a heavy bird without catastrophic failure, since birds can be unpredictably sucked into jet engines at low altitudes or on the ground.
In the event of engine failure in flight, the engine must be shut down. All multi-engine planes can land safely on one engine so that there is little more than inconvenience to the passengers involved if the plane must turn back for safety reasons.
In turboprop engines a conventional aircraft propeller is usually mounted in front of the jet engine and in one type of engine is driven by a second, or free, turbine. This is located behind the turbine that is driving the compressor. In other designs the power is obtained by additional stages on the main turbine.
Since turbine speeds are much higher than propeller speed, a reduction gear is required between the turbine and the propeller. About 90 percent of the energy in the hot gases is absorbed in the turbine, and only about 10 percent remains to increase the speed of the exhaust jet. Accordingly, only a very small portion of the overall thrust is produced by the jet; most of it comes from the propeller.
Turboprops are advantageous for small- and medium-sized planes and at air speeds from 300 to 400 miles (480 to 640 kilometers) per hour. They cannot compete with turbojets for very large planes or at higher speeds.
The air into which an engine rushes at high flight speeds is partially compressed by the so-called ram effect. If the speed is high enough, this compression can be sufficient to operate an engine with neither a compressor nor a turbine. A ramjet has been called a flying stovepipe because it is open at both ends and has only fuel nozzles in the middle. A straight stovepipe, however, would not work; a ramjet must have a properly shaped inlet diffuser that produces low-velocity, high-pressure air at the combustion section, and it must also have a properly shaped exhaust nozzle to increase the speed of flow.
Ramjets can operate at speeds above 200 miles (320 kilometers) per hour, but they become practical only at very high speeds, which must be greater than that of sound. Rockets or other similar devices are needed to produce the initial speed at which a ramjet can begin to operate.
A pulse-jet is similar to a ramjet except that a series of spring-loaded, shutter-type valves is located ahead of the combustion section. In a pulse-jet the combustion is intermittent or pulsing rather than continuous as in a ramjet. Air is admitted through the valves, and combustion begins. This increases the pressure and closes the valves, preventing backflow through the inlet. As the gases expand through the rear nozzle to produce thrust, the pressure in the combustion section drops to the point where the valves open again to admit fresh air. This cycle is then repeated.
The most widely known pulse-jet was the German V-1 missile, or “buzz bomb,” which was used near the end of World War II and which fired at a frequency of about 40 cycles per second. Pulse-jets are inefficient, noisy, and subject to severe vibration. Their use is now limited to low-cost pilotless vehicles.
Rocket engines carry both fuel and oxidizer on board, and they are therefore not dependent on the surrounding atmosphere for the needed supply of oxygen. Accordingly, they provide the primary means of propulsion in outer space.
Rockets are usually classified by the type of fuel burned; solid-propellant rockets carry a solid mixture of fuel and oxidizer. This mixture is similar to gunpowder and burns completely after ignition. The burning generates a large volume of high-pressure gas in the combustion section. This gas is then expanded into a high-velocity jet as it leaves the exhaust nozzle. The burning rate is controlled by shaping the solid fuel in such a fashion that the combustion gases are released at a nearly uniform rate. The control of the thrust, however, is limited, making solid-propellant rockets only suitable for the first, or takeoff, stage of space rockets.
Better control can be obtained in liquid-propellant rockets. In these, both fuel and oxidizer are stored in separate tanks and are then pumped in a carefully metered fashion into the combustion chamber. There they are atomized, mixed, and burned. Because liquid-propellant rockets can be restarted and fully adjusted, they have become the primary propulsion systems in space programs.
Hero of Alexandria applied the principle of jet propulsion in his aeolipile in the first century ad. The Chinese probably invented rockets about 1100. About 1400 a wealthy Chinese developed a rocket-propelled sled-chair, but it exploded when tested.
Leonardo da Vinci in the 16th century used the jet engine principle to design a mechanism for turning a roasting spit. In 1629 Giovanni Branca, an Italian engineer, built a steam turbine that drove a stone-crushing mill. John Barber of England was issued the first patent for a gas turbine in 1791.
Sanford A. Moss in 1902 was probably the first to develop a gas turbine in the United States. Working for the General Electric Company, he designed an aircraft gas turbine in 1918.
In England A. A. Griffith of the Royal Aeronautical Establishment experimented with gas-turbine compressors in 1927. In 1930 another Englishman, Frank Whittle, patented a design for a jet engine, and in 1937 such an engine was successfully tested and in 1941 achieved its first flight.
In Germany the Ernst Heinkel aircraft company produced in 1939 the first successful gas-turbine jet plane, the Heinkel He-178. The next year the Caproni-Campini CC2 was flown in Italy. A reciprocating engine, not a gas turbine, was used to provide the exhaust jet.
In 1941 the British flew their first jet airplane, the Gloster E28/39, powered by a Whittle engine. In the United States the General Electric Company built an engine based on Whittle’s design. It powered the Bell XP-59 Airacomet in 1942—the first jet airplane to fly in the United States. In the same year the Germans produced the first successful jet combat plane, the Messerschmitt Me-262. Germany was the only nation with jets in combat during World War II, but they were introduced too late to be decisive.
After the war jet research continued. In 1947 the American rocket-powered Bell X-1 became the first airplane to fly faster than sound. The next year Britain flew its first supersonic plane, the De Havilland DH-108. In 1959 the American F-106, built by Convair, flew at more than twice the speed of sound.
Britain began the first jet airline service in 1952 with the De Havilland Comet serving scheduled flights from London to Johannesburg, South Africa. This service was stopped, however, after two serious accidents in 1954. In the United States the first jet plane to be commercially tested in 1954 was the Boeing 707, which began regular airliner service in 1958. Since then numerous jet liners, both large and small, have been developed, and today the major portion of all commercial air fleets throughout the world use jet planes.
The British- and French-built Concorde, the first supersonic transport made in the non-Communist world, entered commercial service in 1976. Flying at 2.5 times the speed of sound, the plane seats only about 100 passengers. Because of its high fuel consumption and low seating capacity, it has not proven to be a commercial success.
While the original Boeing 707 and Douglas DC-8 planes utilized four engines, increasing engine size and improved performance have allowed the use of fewer engines. The Lockheed L-1011 and the McDonnell Douglas DC-10 are large three-engine planes with two engines under the wing and one centered at the tail. More recently medium-size twin-engine planes such as the Airbus, built by several European firms, and the Boeing 767 have been introduced with fuel-efficient engines. They are competing with the Boeing 727, a three-engine plane that has become one of the most widely used aircraft in the free world. | 0.826851 | 3.075645 |
TESS, a NASA space exploration telescope, discovered 21 exoplanets outside our solar system and collected data on other interesting events in the southern half of the sky during its first year. But TESS seems to be focusing its attention now on the northern hemisphere to complete the most comprehensive planet-hunting expedition ever undertaken.
On July 18, the survey of the southern part was completed, the spacecraft turned its cameras to the north, and when the northern part is completed by 2020, TESS will have identified more than three quarters of the sky.
“TESS takes the next step, if the planets are everywhere,” said Paddy Boyd, a TESS scientist at NASA’s Goddard Space Flight Center. “Let’s find those nearby glittering stars orbiting us, because they will be the stars that we can now follow through existing terrestrial and space telescopes “He said.
To find the outer planets, TESS uses four large cameras to watch a 24-degree segment of the sky for 27 days at a time. Some of these sections overlap, so some parts of the sky are watched for nearly a year. TESS focuses on stars closer to 300 years from our solar system.
NASA is working hard to put astronauts on some of the closest space objects “Moon and Mars” to understand more about the planets in our solar system. Following observations with powerful telescopes of the planets will enable us to better understand how Earth and the solar system were formed.
The mission, which was launched with a budget capped at $200 million, spent its first year surveying the southern hemisphere. Now, it has turned its cameras on the northern skies to repeat a similar scan. | 0.803994 | 3.300383 |
Black hole dynamo may be cosmos' electricity generator
LANL NEWS RELEASE
Posted: June 9, 2002
Researchers at the U.S. Department of Energy's Los Alamos National Laboratory believe that magnetic field lines extending a few million light years from galaxies into space may be the result of incredibly efficient energy-producing dynamos within black holes that are somewhat analogous to an electric motor. Los Alamos researchers Philipp Kronberg, Quentin Dufton, Stirling Colgate and Hui Li discussed this finding at the American Astronomical Society meeting in Albuquerque, N.M.
By interpreting radio waves emanating from the gigantic magnetic fields, the researchers were able to create pictures of the fields as they extended from an object believed to be a black hole at the center of a galaxy out into regions of intergalactic space. Because the class of galaxies they studied are isolated from other intergalactic objects and gas ‹ which could warp, distort or compress the fields ‹ the fields extend a distance of up to ten million light years.
The energy in these huge magnetic fields is comparable to that released into space as light, X-rays and gamma rays. In other words, the black hole energy is being efficiently converted into magnetic fields. The mechanism is not yet fully understood, but Kronberg and his colleagues believe a black hole accretion disk could be acting similarly to an electric motor.
Colgate and Los Alamos colleagues Vladimir Pariev and John Finn have developed a model to perhaps explain what is happening. They believe that the naturally magnetized accretion disk rotating around a black hole is punctured by clouds of stars in the vicinity of the black hole, like bullet holes in a flywheel. This, in turn, leads nonlinearly to a system similar to an electric generator that gives rise to a rotating, but invisible magnetic helix.
In this way, huge amounts of energy are carried out and away from the center of a galaxy as a set of twisted magnetic field lines that eventually appear via radio waves from luminous cloud formations on opposite sides of the galaxy.
The Los Alamos researchers are calculating methods by which enormous amounts of expelled magnetic energy are converted into heat ‹ manifested in the form of a relativistic gas of cosmic rays that create radio energy that can be detected by radio telescopes such as the Very Large Array. Although the exact mechanism is still a mystery, the Los Alamos researchers believe that a sudden reconnection or fusing of the magnetic field lines creates and accelerates the cosmic rays.
The researchers still don't understand why this fast magnetic field reconnection occurs. But understanding the mechanism could have important applications here on Earth such as creating a system of magnetic confinement for a fusion energy reactor.
The Los Alamos research is supported by the Laboratory Directed Research and Development Program and the Institute of Geophysics and Planetary Physics. The Natural Sciences and Engineering Research Council of Canada also provided support.
Los Alamos recently joined Southwest Universities consortium, which is hoping to build a very low frequency radio telescope called "LOFAR" in New Mexico or West Texas. The new telescope will be an excellent instrument for detecting hidden magnetic energy of the type the Los Alamos research team is interested in studying.
Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy and works in partnership with NNSA's Sandia and Lawrence Livermore national laboratories to support NNSA in its mission.
Los Alamos enhances global security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health and national security concerns.
DVD is here!|
The first in a series of space DVDs is now available from the Astronomy Now Store. Relive shuttle Columbia's March flight to refurbish the Hubble Space Telescope in spectacular DVD quality.
U.K. & WORLDWIDE STORE
The Apollo 14 Complete Downlink DVD set (5 discs) contains all the available television downlink footage from the Apollo 14 mission. A two-disc edited version is also available. | 0.906956 | 3.854351 |
The earth and other celestial bodies are continually bombarded by extremely fast-moving, subatomic particles known as cosmic rays, gamma rays and neutrinos. Although the origin of ultra-high energy (UHE) particles (defined as above 1018 electronvolts or eV) is unknown, scientists believe that they could be created and accelerated by cataclysmic events, such as collisions between compact objects or a star falling into the black hole at the center of a galaxy.
Nearly all of the cosmic rays that originate outside of Earth’s atmosphere are the nuclei of well-known atoms, such as hydrogen and helium, stripped of their electron shells. Neutrinos also are subatomic particles, but they possess a neutral electrical charge, only interact weakly and, therefore, can pass through normal matter unimpeded.
Astrophysicists can use information gleaned from these elusive particles to learn more about the universe and even about particle physics. A study led by Amy Connolly, Ph.D., assistant professor of physics at The Ohio State University, leveraged Ohio Supercomputer Center resources to evaluate the complementarity of cosmic rays and neutrinos as a source of information about the universe’s most extreme particle accelerators.
“Cosmic rays above 1019.5 eV cannot have originated from more than approximately 100 megaparsecs from Earth due to the onset of the GZK process,” said Connolly. The Greisen–Zatsepin–Kuzmin (GZK) process represents the slowing and bending of cosmic rays over long distances due to microwave background radiation. “Neutrinos, however, can travel cosmological distances unabated and would be our only view of the distant universe above the GZK cutoff.”
Connolly’s group utilized open-source CRPropa, as well as other simulation and analysis software, to calculate the energy spectrum of protons, gamma rays and neutrinos observed at Earth. They analyzed protons produced at energies between 1016 eV and 1025 eV and at distances up to 3 gigaparsecs.
They quantified the implications of current cosmic ray measurements and neutrino constraints on parameters characterizing the UHE sources, subject to existing gamma ray measurements. The group measured the spectral index below 1020 eV and the overall normalization of source emission. Neutrinos provide the ultimate acceleration energy (Emax) and are unique probes of redshift evolution, or the dependence of the density of sources on distance. For the first time, they constrained Emax based on the non-observation of UHE neutrinos by current experiments and quantified the sensitivity of future experiments to measuring Emax and the source evolution.
Project Lead: Amy Connolly, The Ohio State University
Research Title: The complementary nature of cosmic rays and neutrinos in constraining UHE astrophysics
Funding Source: National Science Foundation | 0.847608 | 4.195076 |
Pluto's strange "snakeskin" terrain has an Earthly counterpart, a new study suggests.
The "scales" of this alien landscape, which were first spotted by NASA's New Horizons spacecraft during its epic Pluto flyby in July 2015, are ice ridges 1,650 feet (500 meters) or so tall. But they're very similar to erosion-formed features known as "penitentes," which rise just a few meters above the ground in cold, mountainous regions of Earth, the scientists said in the study.
"This gargantuan size is predicted by the same theory that explains the formation of these features on Earth," study lead author John Moores, of York University in Toronto, said in a statement. "In fact, we were able to match the size and separation, the direction of the ridges, as well as their age — three pieces of evidence that support our identification of these ridges as penitentes." [Amazing Pluto Photos by New Horizons]
The penitentes of Pluto and Earth differ in both composition and size: Earth's are made of snow or water ice, whereas Pluto's ridges are mostly methane and nitrogen ices, the researchers said.
Moores and his colleagues used computer simulations to model the growth of penitente-like features in Pluto's unique environment. Their results suggest that, although these ice ridges are currently known to exist only on Earth and Pluto, they may also be on other solar system bodies with the right conditions — for example, low temperatures and the presence of an atmosphere.
The new study, which was published this week in the journal Nature, also indicates that Pluto's penitentes probably formed within the past few tens of millions of years, the researchers said. (These features were so named because arrays of them look like groups of people on their knees, doing penance for their sins.)
New Horizons got within 7,800 miles (12,550 kilometers) of Pluto on July 14, 2015, giving humanity its first up-close looks at the faraway dwarf planet. The spacecraft is now cruising toward a Jan. 1, 2019, close encounter with a small object called 2014 MU69, which lies about 1 billion miles (1.6 billion km) beyond Pluto. | 0.811185 | 3.518069 |
A rocket powered by kerosene and liquid oxygen and carrying a scientific observatory blasted off into space at 10:49 p.m., March 6, 2009 (by local calendars and clocks). The launch came from the third planet out from a G-type star, 25,000 light-years from the center of a galaxy called the Milky Way, itself located on the outskirts of the Virgo Cluster of galaxies. On the night of the launch, the sky was clear, with no precipitation or wind, and the temperature was 292 degrees by the absolute temperature scale. Local intelligent life forms cheered the launch. Shortly before the blastoff, the government agency responsible for spacecraft, named the National Aeronautics and Space Administration, wrote in the global network of computers: “We are looking at a gorgeous night to launch the Kepler observatory on the first-ever mission dedicated to finding planets like ours outside the solar system.”
The above account might have been written by an intelligent life form located on exactly the kind of distant planet that Kepler would soon begin to search for. Named after the Renaissance astronomer Johannes Kepler, the observatory was specifically designed to find planets outside our solar system that would be “habitable”—that is, neither so near their central star that water would be boiled off, nor so far away that water would freeze. Most biologists consider liquid water to be a precondition for life, even life very different from that on Earth. Kepler has surveyed about 150,000 sun-like stellar systems in our galaxy and discovered over 1,000 alien planets. Its enormous stockpile of data is still being analyzed.1
If the Gobi Desert represents all of the matter flung across the cosmos, living matter is a single grain of sand.
For centuries, we human beings have speculated on the possible existence and prevalence of life elsewhere in the universe. For the first time in history, we can begin to answer that profound question. At this point, the results of the Kepler mission can be extrapolated to suggest that something like 10 percent of all stars have a habitable planet in orbit. That fraction is large. With 100 billion stars just in our galaxy alone, and so many other galaxies out there, it is highly probable that there are many, many other solar systems with life. From this perspective, life in the cosmos is common.
However, there’s another, grander perspective from which life in the cosmos is rare. That perspective considers all forms of matter, both animate and inanimate. Even if all “habitable” planets (as determined by Kepler) do indeed harbor life, the fraction of all material in the universe in living form is fantastically small. Assuming that the fraction of planet Earth in living form, called the biosphere, is typical of other life-sustaining planets, I have estimated that the fraction of all matter in the universe in living form is roughly one-billionth of one-billionth. Here’s a way to visualize such a tiny fraction. If the Gobi Desert represents all of the matter flung across the cosmos, living matter is a single grain of sand on that desert. How should we think about this extreme rarity of life?
Most of us human beings throughout history have considered ourselves and other life forms to contain some special, nonmaterial essence that is absent in nonliving matter and that obeys different principles than does nonliving matter. Such a belief is called “vitalism.” Plato and Aristotle were vitalists. Descartes was a vitalist. Jöns Jakob Berzelius, the 19th-century father of modern chemistry, was a vitalist. The hypothesized nonmaterial vital essence, especially in human beings, has sometimes been called “spirit.” Sometimes “soul.” The eighth-century B.C. Egyptian royal official Kuttamuwa built an 800-pound monument to house his immortal soul and asked that his friends feast there after his physical demise to commemorate him in his afterlife. The 10th-century Persian polymath Avicenna argued that since we would be able to think and to be self-aware even if we were totally disconnected from all external sensory input, there must be some nonmaterial soul inside of us. These are all vitalist ideas.
Modern biology has challenged the theory of vitalism. In 1828, the German chemist Friedrich Wöhler synthesized the organic substance urea from nonorganic chemicals. Urea is a byproduct of metabolism in many living organisms and, previous to Wöhler’s work, was believed to be uniquely associated with living beings. Later in the century, the German physiologist Max Rubner showed that the energy used by human beings in movement, respiration, and other forms of activity is precisely equal to the energy content of food consumed. That is, there are no hidden and nonmaterial sources of energy that power human beings. In more recent years, the composition of proteins, hormones, brain cells, and genes has been reduced to individual atoms, without the need to invoke nonmaterial substances.
Yet, I would argue that most of us, either knowingly or unknowingly, remain closet vitalists. Although there are moments when the material nature of our bodies screams out at us, such as when we have muscle injuries or change our mood with psychoactive drugs, our mental life seems to be a unique phenomenon arising from a different kind of substance, a nonmaterial substance. The sensations of consciousness, of thought and self-awareness, are so gripping and immediate and magnificent that we find it preposterous that they could have their origins entirely within the humdrum electrical and chemical tinglings of cells in our brains. However, neuroscientists say that is so.
A universe without comment is a universe without meaning.
Polls of the American public show that three-quarters of people believe in some form of life after death. Surely, this belief too is a version of vitalism. If our bodies and brains are nothing more than material atoms, then, as Lucretius wrote two millennia ago, when those atoms disperse as they do after death, there can be no further existence of the living being that once was.
Paradoxically, if we can give up the belief that our bodies and brains contain some transcendent, nonmaterial essence, if we can embrace the idea that we are completely material, then we arrive at a new kind of specialness—an alternative to the specialness of “vitalism.” We are special material. We humans living on our one planet wring our hands about the brevity of our lives and our mortal restraints, but we do not often think about how improbable it is to be alive at all. Of all the zillions of atoms and molecules in the universe, we have the privilege of being composed of those very, very few atoms that have joined together in the special arrangement to make living matter. We exist in that one-billionth of one-billionth. We are that one grain of sand on the desert.
And what is that special arrangement deemed “life?” The ability to form an outer membrane around the organism that separates it from the external world. The ability to organize material and processes within the organism. The ability to extract energy from the external world. The ability to respond to stimuli from the external world. The ability to maintain stability within the organism. The ability to grow. The ability to reproduce. We human beings, of course, have all of these properties and more. For we have billions of neurons connected to each other in an exquisite tapestry of communication and feedback loops. We have consciousness and self-awareness.
The two tramps in Samuel Beckett’s Waiting for Godot, placed on a minimalist stage without time and without space, waiting interminably for the mysterious Godot, capture our bafflement with the meaning of existence.
Estragen: “What did we do yesterday?”
Vladimir: “What did we do yesterday?”
Vladimir: “Why ... (Angrily) Nothing is certain when you’re about.”
Of course, there are questions that do not have answers.
But if we can manage to get outside of our usual thinking, if we can rise to a truly mind-bending view of the cosmos, there’s another way to think of existence. In our extraordinarily entitled position of being not only living matter but conscious matter, we are the cosmic “observers.” We are uniquely aware of ourselves and the cosmos around us. We can watch and record. We are the only mechanism by which the universe can comment on itself. All the rest, all those other grains of sand on the desert, are dumb, lifeless matter.
Of course, the universe does not need to comment on itself. A universe with no living matter at all could function without any trouble—mindlessly following the conservation of energy and the principle of cause and effect and the other laws of physics. A universe does not need minds, or any living matter at all. (Indeed, in the recent “multiverse” hypothesis endorsed by many physicists, the vast majority of universes are totally lifeless.) But in this writer’s opinion, a universe without comment is a universe without meaning. What does it mean to say that a waterfall, or a mountain, is beautiful? The concept of beauty, and indeed all concepts of value and meaning, require observers. Without a mind to observe it, a waterfall is only a waterfall, a mountain is only a mountain. It is we conscious matter, the rarest of all forms of matter, that can take stock and record and announce this cosmic panorama of existence before us.
I realize that there is a certain amount of circularity in the above comments. For meaning is relevant, perhaps, only in the context of minds and intelligence. If the minds don’t exist, then neither does meaning. However, the fact is that we do exist. And we have minds. We have thoughts. The physicists may contemplate billions of self-consistent universes that do not have planets or stars or living material, but we should not neglect our own modest universe and the fact of our own existence. And even though I have argued that our bodies and brains are nothing more than material atoms and molecules, we have created our own cosmos of meaning. We make societies. We create values. We make cities. We make science and art. And we have done so as far back as recorded history.
In his book The Mysterious Flame (1999), the British philosopher Colin McGinn argues that it is impossible to understand the phenomenon of consciousness because we cannot get outside of our minds to discuss it. We are inescapably trapped within the network of neurons whose mysterious experience we are attempting to analyze. Likewise, I would argue that we are imprisoned within our own cosmos of meaning. We cannot imagine a universe without meaning. We are not talking necessarily about some grand cosmic meaning, or a divine meaning bestowed by God, or even a lasting, eternal meaning. But just the simple, particular meaning of everyday events, fleeting events like the momentary play of light on a lake, or the birth of a child. For better or for worse, meaning is part of the way we exist in the world.
And given our existence, our universe must have meaning, big and small meanings. I have not met any of the life forms living out there in the vast cosmos beyond Earth. But I would be astonished if some of them were not intelligent. And I would be further astonished if those intelligences were not, like us, making science and art and attempting to take stock and record this cosmic panorama of existence. We share with those other beings not the mysterious, transcendent essence of vitalism, but the highly improbable fact of being alive.
Alan Lightman is a physicist, novelist, and professor of the practice of the humanities at the Massachusetts Institute of Technology. His latest book is Screening Room. | 0.854883 | 3.790969 |
Why do we celebrate Christmas just a few days after the winter solstice when almost no one thinks Jesus was born on December 25th? Is the astronomical connection with Christianity's high holy day a fluke or an ancient cynical political calculation. Or, more importantly, does it point us to a deeper truth now almost entirely lost in a world alienated from its own most intimate experience of the night sky?
Before we answer that question we must stop for a word from our solar system.
What, exactly is the winter solstice? The winter and summer solstices mark the poles of Earth's temporal cycle as it marches around the Sun. Our planet's spin axis is tilted 23 degrees relative to the line linking us with our Star (that line defines the plane of our orbit as we sweep around Sol). Since the spin axis direction remains fixed relative to the stars (i.e. it points for now towards Polaris, the "North Star"), the duration of daylight changes as the Earth moves around the Sun. In the northern hemisphere the Earth's axis is tilted towards the Sun in the summer and we have long days (more hours of sunlight). Likewise the axis is tilted away from the Sun in the northern hemisphere in the winter and we have short days. The winter solstice marks that day with the fewest sunlit hours (again, in the northern hemisphere).
At winter solstice the sun marks its southern-most rising. Also on the solstice the Sun's noontime position is its lowest (closest to the horizon) of the entire year. Each of these extremes are connected (rising position, noontime position and hours of daylight) and all result from the basic fact that the axis of our planet's spin and the axis of its orbit around the Sun are not aligned.
Which brings us back to, and before, Christmas.
There remains a lot debate about the how Christmas got its location on the calendar. The popular account makes hay of the ancient Roman's pinning the solstice to December 25th. Early Christians simply co-opted the solstice for the own ends, or so the story goes. To make things more explicit, in 274 C.E., the Roman emperor Aurelian established a feast of the birth of Sol Invictus (the Unconquered Sun), on December 25. Given this Roman holiday and the fact that barbarian peoples of both western and northern Europe would have had their own festivals during this period, it seems reasonable that Christmas is really "a spin-off" from early pagan solar holy days.
There are, however, scholars who do not support this idea. The detractors note that Aurelian was vehemently anti-Christian and may have established his feast after the Christians began their celebrations of Jesus' birth on December 25th. The scholars also see little hard historical evidence for the co-opted pagan holiday theory. As theologian Andrew McGowen puts it:
"Early Christian writers never hint at any recent calendrical engineering; they clearly don’t think the date was chosen by the church. Rather they see the coincidence as a providential sign, as natural proof that God had selected Jesus over the false pagan gods."
Reading over the debate one finds a definite undercurrent of either antagonism or reactive defensiveness. Sometimes the "pagan-co-opt" camp seems intent on proving the political machinations of Christians in stealing the solstice holiday of others for their own ends. The "anti-co-opt" camp can seem just as intent on liberating the church's founders from claims of holiday pilfering. What is lost in all this argumentation, however, is the very real loss we have all suffered in the long march of centuries.
Astronomy, you see, has always been destiny. We have simply been able to forget that fact for a century or so.
Most of us we have little first hand experience of the solstice and its celestial message. Living in a world saturated with artificial illumination and run off meticulously accurate, mechanical (or electronic) chronometers, we rarely notice anything that happens in the sky. But the genes we carry in every cell of our bodies know. They remember. For those thousands of human generations -- those whose ancestry you inherited -- the Sun, the sky and the stars were the only true pageant and its turnings signaled life and death. The sky foretold the end of winter and hunger, it signaled the beginning of warmth and renewed growth. In this way our great, great, great grandparents could not help but see the heavenly wheels turn and they could not help but turn their imaginative creations, sacred or otherwise, to its imperatives.
Seventy kilometers or so north of Dublin stands the Neolithic monument at Newgrange. The 80-meter wide circular mound was built 500 years before the pyramids and 3,000 years before anyone thought about when to hold Christmas. There is only one entrance, a narrow 25-meter long passageway that leads into a vaulted central chamber. Without a flashlight, it is darker than death itself within the chamber. But for a few days each year around the winter solstice the rising sun aligns with the ancient passageway and something remarkable happens. A shaft of sunlight pierces the darkness and, for a few minutes, the central chamber glows in warm ochre -- a promise of the light and life to come with the approaching spring. With the massive effort required to build Newgrange 5,000 years ago the forgotten builders of Newgrange show us that they knew something in their bones that we can barely recall.
The sky has always been our first tabernacle, our first vault of the sacred. That we live in a scientific age does not change this fact. No one need feel offended, defensive or outraged that Christianity's holiest day falls near the turning of the year. It should not be a surprise. In fact, it should serve as a reminder. The solistice was always a holy day.
We are born of the world and we are born of the stars. None of our changing perspectives, religious or scientific, can change that fact. We once knew it in our bones. Buried down deep we still know. | 0.884501 | 3.514282 |
HD 46375 is an 8th magnitude K-type subgiant star located approximately 109 light-years away in the constellation of Monoceros. This star resembles a orange dwarf but which has a larger radius and luminosity indicating that fusion reactions in its core are starting to cease and the star is on its way becoming a red giant. Spectral type of the star is K1 IV. Its advanced evolutionary stage shows that it is considerably older than our Sun.
This star has sometimes been classified as a member of the NGC 2244 star cluster in the Rosette Nebula, but in reality it just happens to lie in the foreground. The distance to the cluster is much greater, about 4500 light years.
In 2000, a low-mass gas giant was found orbiting the star.
On March 29, 2000, the planet HD 46375 b with only three quarters the mass of Saturn was discovered by Marcy, Butler, and Vogt in California, together with 79 Ceti b. This planet was discovered using the "wobble method" or radial velocity method, which calculates the rate and shape of the stellar wobble caused by the revolving planet's gravity.
* List of extrasolar planets
1. ^ Marcy et al.; Butler, R. Paul; Vogt, Steven S. (2000). "Sub-Saturn Planetary Candidates of HD 16141 and HD 46375". The Astrophysical Journal Letters 536 (1): L43–L46. doi:10.1086/312723. http://www.iop.org/EJ/article/1538-4357/536/1/L43/005174.html.
* "Notes for star HD 46375". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=HD+46375. Retrieved 2008-08-23. | 0.847623 | 3.293068 |
Where did the moon come form, how did the moon form, how old is the moon, how did it get there? There is much speculation and mystery surrounding the subject of the moon and its origins. There are currently three main stream theories attempting to explain the origin of the moon.
The fission theory suggests the moon was once part of the earth and somehow separated from our planet in its early history. The condensation theory suggests the moon and earth condensed together from the original nebula that formed the solar system. The capture theory states the Moon was formed not in the vicinity of the Earth, but in a different part of the solar system, and was later captured by the Earth. The impact theory states an object in space the size of mars crashed into Earth ejecting large volumes of matter into earths orbit which condensed to form the moon.
Although there are facts that disprove every theory we are told by mainstream science, they are still put out there.
According to mainstream scientists, the Earth and the moon are the same age; but according to the facts, this is not true. Some moon rocks are as old as 5.3 billion years old, and others are as old as 20 billion years. The Earth itself is said to be 4.6 billion years old. Elements such as Uranium 236 and neptunium 237 were discovered in lunar rocks and are not found naturally on earth; This fact, and the age of lunar rocks disprove the fission, impact, and condensation theory. Scientists also discovered that the moon contains heavier elements on the surface, the crust is composed primarily of illeminite, a mineral containing large amounts of titanium, uranium 236 and neptunium 237. The heavier elements of a naturally forming objects in space would have ended up in the center and the surface would contain the lighter elements; this means the moon is not a naturally forming object, this fact also disproves the condensation, and capture theory.
On November 20, 1969, the Apollo 12 crew crashed a lunar modual onto the moon, this created a moon quake which caused the moon reverberated like a bell for over an hour, leading to the conclusion the moon has a light, or no core.
According to Thomas J Glover, our moon has a diameter of 2,160 miles and a gravity of .17, that of earth. NASA’s more accurate moon gravity figure is 1.6, with a current orbital speed is 19,051 miles per hour. The moons density is 3.3 times an equal volume of water while earth’s average density is 5.5 times that of an equal volume of water. The fact that the Moon is only 60 percent as dense as Earth has led scientists to two theories that the Moon is without an iron core, and possibly, is partially hollow. Data and computations point to the conclusion that our Moon is internally hollow to a great extent. Since most scientists claim that there is no natural explanation for such a peculiar phenomenon, the inevitable conclusion indicated that the Moon is artificially hollow. Our Soviet theorists, agree.
Isaac Asimov, a Russian professor of biochemistry and writer of popular science books, said by all cosmic laws, the Moon should not be orbiting Earth. He went on saying, “we cannot help but come to the conclusion that the Moon by rights ought not to be there. The fact that it is, is one of those strokes of luck almost too good to accept. Small planets, such as Earth, with weak gravitational fields, might well lack satellites. In general, then, when a planet does have satellites, those satellites are much smaller than the planet itself. Therefore, even if the Earth has a satellite, there would be every reason to suspect that at best it would be a tiny world, perhaps 30 miles in diameter. But that is not so. Earth not only has a satellite, but it is a giant satellite, 2,160 miles in diameter. Its too big to have been captured by the earth. The chances of such a capture having been effected and the moon they having taken up nearly circular orbit around our earth are too small to make such an eventually credible.”
Our ancestors on both sides of the globe tell of a time when there was no moon orbiting our land.
Ancient, which include Greek philosophers, describes a time when there was no moon near Earth. Democritus and Anaxagoras taught that there was a time when the Earth was without the Moon. Aristotle wrote that Arcadia in Greece, before being inhabited by the Hellenes, had a population of Pelasgians, and that these aborigines occupied the land already before there was a moon in the sky above the Earth.
Censorinus, a Roman grammarian and miscellaneous writer from the 3rd century A D, also refers to the time in the past when there was no moon in the sky.
The memory of a world without a moon lives in oral tradition among the Native tribes in South America. The Natives of the Bogota highlands, in the eastern Cordilleras of Colombia, relate some of their tribal reminiscences to the time before there was a moon. “In the earliest times, when the moon was not yet in the heavens,” as described the tribesmen of Chibchas.
People on both sides of the globe have oral and written records of a time when there was no moon in the sky.
Another theory of the moons origins does not share the popularity of that of the mainstream theories. Theorists suggest the moon is a hollowed out planetoid, partially artificial, belonging to and still in use by the Annunaki. One thing to note about the moon is the chemical composition of moon dust is different than rocks, which means it is not a result of weathering. This means it must have originated elsewhere. Another thing to note about moon rocks is that despite having no magnetic field, moon rocks were magnetized, which shocked scientists. If you believe the earth does not have a solid, or molten interior, and is hollow, one thing you may wonder is “Where does the Earths magnetic field come from?”.
If you understand the Reptilian Agenda you may understand my theory on the purpose of the moon and the magnetic field surrounding earth. I theorize the moon is not only a base, or home to another species, but also a machine belonging to the Blood Line Elite, which generates the magnetic field around our environment. As organic machinery, our bodies are containers for our souls, or consciousness. As soon as a conscious being, human or not, dies on Earth, he or she is trapped in this “prison planet”, with the magnetic field as a net, keeping us from escaping the Matrix controlled by the Reptilian Elite; we are forced to reincarnate here to be used as a cheap energy source and be their eternal slaves. | 0.880377 | 3.186414 |
Authors: David Ehrenreich, Christophe Lovis, Romain Allart, et. al.
First Author’s Institution: Observatoire astronomique de l’Université de Genève, University of Geneva, Switzerland
Status: Published in Nature, open access on arXiv
Thousands of exoplanets have now been detected beyond our Solar System and many have challenged our expectations of what an exoplanetary system ought to look like. Before the first confirmed discoveries it was generally assumed that other planetary systems would more or less resemble our own – with small, rocky planets located close to the host star and larger gas giants residing farther out. But the discovery of the class of ‘hot Jupiters’ – large gas giants similar to Jupiter orbiting excruciatingly close to their host stars – showed that exoplanetary systems can exist in far more exotic configurations than was previously believed possible. Now an international team of researchers led by David Ehrenreich at the University of Geneva have discovered one of the most exotic exoplanets yet – an ultra-hot Jupiter where liquid iron rains from the skies.
The team observed the exoplanet known as WASP-76b as it crossed the disc of its host star using ESPRESSO, the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, at the European Southern Observatory’s Very Large Telescope (VLT) in Chile. ESPRESSO is a fibre-fed, high-resolution spectrograph and was originally designed to hunt for Earth-size rocky planets around Sun-like stars by detecting the tiny wobble of the star due to the orbital motion of an unseen companion planet (known as the radial velocity method).
WASP-76b is located about 640 light-years from the Earth and orbits at only about three times the radius of its host star – much closer than Mercury does to our own Sun. The planet is about the same mass as Jupiter but about twice as large, and completes a full orbit in only 1.8 days. The planet is so close to its star that it receives thousands of times more radiation than the Earth does from the Sun, resulting in extreme temperatures on its surface and establishing WASP-76b as a member of the ‘Ultra Hot’ class of exoplanets. At such close proximity the planet is also likely to be tidally locked, meaning that it takes the same time for the planet to rotate on its axis as it does for it to complete an entire orbit. One hemisphere of the planet therefore constantly faces towards the star, similar to our own Earth/Moon configuration. The consequences of this are an estimated dayside temperature exceeding 2400 degrees Celsius and a nightside which is a relatively cooler 1500 degrees. The temperature on the dayside is so high that most matter will exist in atomic form and is high enough that metals such as iron will vaporise. The large temperature gradient between the day and night sides also drives extremely strong winds across the planet.
The team used the technique of high-resolution spectroscopy to examine the atmospheric composition of WASP-76b. This technique can be used to resolve the doppler shift of absorption features originating in the planet’s atmosphere from those of the host star (which is essentially stationary compared to the motion of the planet). Chemical species in the planet’s atmosphere can then be detected by isolating the planet’s signal and cross-correlating its spectrum with a template spectrum containing that species.
The researchers found a strong absorption signature corresponding to iron at the day-to-night border, which was blueshifted due to the combination of the rotation of the planet and the strong winds blowing from the hotter dayside. The team also found that the signal was not apparent at the morning border showing that absorption is not taking place there and therefore that iron is much less abundant or even entirely absent on the nightside and morning terminator of the planet. The team concluded that the most likely explanation for these observations is that iron vapour travels from the hot dayside of WASP-76b to the cooler night side via the strong day-to-night winds, where it can then condense into clouds and fall as liquid iron droplets.
These results are the first to show different atmospheric chemistry between the day-to-night and night-to-day terminators for an ultra-hot exoplanet atmosphere and were obtained during the very first science observations made with ESPRESSO in September 2018. The techniques used offer an exciting way to explore the climates of other extreme exoplanetary atmospheres and could also help to refine 3D global circulation models. | 0.894117 | 3.936014 |
Theme: The future cannot be predicted, but future can be invented!!
Astronomy Congress 2018
Astronomy Congress 2018 aims to bring together a multi-disciplinary group of scientists and engineers to present and exchange breakthrough ideas relating to Early Universe, Dark Matter and Dark Energy ,Astronomy, Gravitational Physics, Particle and Nuclear Astrophysics, Large-Scale Structures, Stellar Formation and Evolution, Observational Astronomy and Astrophysics, Celestial Mechanics, Theoretical Astronomy and Astrophysics, Interdisciplinary Studies, Space Observation and Exploration, Structure and Evolution of the Cosmos, Unsolved Problems in Astronomy. It promotes top-level research and to globalize the quality research in general, thus making discussions, presentations and contributions more internationally competitive.
Importance and Scope:
The existence of the Earth's galaxy, the Milky Way, as a separate group of stars, was only proved in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the Universe, seen in the recession of most galaxies from us. Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars, and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's law, and cosmological abundances of elements. Space telescopes have enabled measurements in parts of the electromagnetic spectrum normally blocked or blurred by the atmosphere. The core aim of Astronomy 2018 conference is to provide an opportunity for the delegates to meet, interact and exchange new ideas in the various areas of Astronomy and related fields.
- Space Scientists
Track 1: Astronomy
Natural Science is a branch of Science which explains the natural phenomena with description, prediction, and understanding based on observational and empirical evidences. Astronomy is the Oldest of natural sciences and an effort to explain the origin of various objects and their evolution. According to NASA (National Aeronautics and Space Administration) Astronomy is the study of “stars, planets and space”. It is a growing field in research and development and almost every day a new discovery is being made. Various questions like – How did galaxy formed? How was sun created? How long does it take to travel from one planet to another? How many solar systems are there in this universe? What is Higgs Boson? How Did the First Quasars Form? And so on….. Finally have answers, thanks to astronomy.
The early civilizations in history such as Greeks, Egyptians, Nubians, Iranians, Chinese, and Indians performed methodical observations of the night sky to make calendars. So, in 20th century the field of professional astronomy was split into two branches
OBSERVATIONAL Astronomy and THEORETICAL Astronomy.
Observational Astronomy, the data is acquired from observations of astronomical objects which are then later analyzed via basic principles of physics.
Theoretical Astronomy on the other hand bends towards computational or analytical models to explain an astronomical objects as well as phenomena.
Both the fields are related to each other as theoretical astronomy explains observational results and vice versa.
In this session of astronomy, latest research trends and the existence of Planets, stars, sun,moon,galaxies etc., will be discussed.
Track 2: Astrophysics
Astrophysics is the branch of astronomy that incorporates the basic principles of physics and chemistry to study and give out observations and understandings on objects like sun, moon, planets, galaxies, nebulae, black holes, and all remaining objects that drift in cosmos. Astrophysics is also called as “Space Science”. The role of an Astrophysicist is to understand the universe and our place in it. They work on one goal and that is to discover how this universe works, how did it all begin and how did it evolved.
Track 3: Computational Astrophysics
Many areas in physics rely on computational techniques to study the dynamic evolution of various complex physics problems. All the stimulations performed by the computer should be precise and timely. To make sure that happens, Computational Astrophysics was introduced in the field.
Various Important techniques that are used in computational physics are “Particle-in-cell, particle mesh, N-body simulations, Monte Carlo methods, and grid-free & grid-based methods for fluids.
To perform the above task both hardware and software should be at its ace. A supercomputer or a cluster of computers is used as the hardware for the computational astrophysics. And various codes tend to be n-body packages. Example being ChaNGa, MODEST, nbodylab.org and Starlab.
AMUSE--one of the software package used by computational astrophysicist takes a different approach than others by giving them an interface structure to a larger number of publicly available astronomical codes for addressing stellar dynamics, stellar evolution, and hydrodynamics.
Track 4: Dark Matter, Dark Energy, and Black Holes
During early 1990's scientists were sure about the expansion of the universe. Theoretically the expansion process had to slow down due to the gravitational force as time pass by, but by the findings of Hubble Space Telescope in 1998 which observed a distant supernova that the universe was expanding more than slowing down today. Scientists even though it’s a result of a long-discarded version of Einstein's theory of gravity, one that contained the "cosmological constant" but even that didn't give them the answer they were looking for. So they decided it to name it as Dark Energy. Almost 68% of the entire universe is dark energy, 27% composes of Dark Matter and all the other normal matter comprises to 5%.
Dark Matter is the little portion of that visible matter present in the universe which sums up to form a total of 27 % . The matter is made up of particles called baryons. Scientists found this discovery after observing the absorption of radiations passing through them. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs. Days later they discovered that the Dark Matter is not baryonic at all but it is made up of other more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).
Black Holes are great amount of matter packed together in a very small area which then results in large gravitational force that even light could escape through it. The term was coined by Princeton physicist John Wheeler in 1967.
Black holes are formed after the supernova explosion of any star. Einstein’s theory of general relativity predicted that after any star dies, it leaves behind a small, dense remnant core. And if the mass of this core is almost three times the mass of sun then according to the equation the black hole is generated by overcoming all the gravitational forces. And if the remnant is small then it becomes a dense neutron star that is just incapable of trapping enough light into it.
Track 5: Gravitational Physics
Gravitational physicists explore the implications of the general theory of relativity, in which gravitation is a consequence of the curvature of space and time. This curvature thus controls the motion of inertial objects. Modern research in gravitational physics includes studying applications of numerical relativity, black hole dynamics, sources of gravitational radiation, critical phenomena in gravitational collapse, the initial value problem of general relativity, and relativistic astrophysics. The works of Isaac Newton and Albert Einstein dominate the development of gravitational theory. Newton’s classical theory of gravitational force held sway from his Principia, published in 1687, until Einstein’s work in the early 20th century. Newton’s theory is sufficient even today for all but the most precise applications. Einstein’s theory of general relativity predicts only minute quantitative differences from the Newtonian theory except in a few special cases. The major significance of Einstein’s theory is its radical conceptual departure from classical theory and its implications for further growth in physical thought.
Track 6: Neutrino Astronomy
We are educated some further things about the cosmos beyond the solar system by sighting cosmic rays, which are mostly prepared of either atomic nuclei minus their orbiting electrons, or one of their basic components, protons. But these positively charged particles don’t point to their place of origin due to the magnetic fields of our galaxy which affect their flight paths like a magnet affects iron filings. The total number of elementary particles in the cosmos, and these neutral weakly interacting particles arisen to us almost without any trouble straight from their sources, traveling at very close to the speed of light. A with low energy of neutrino in flight would not notice a barrier of lead 50 light years thick. When we are able to see out in neutrino light we will undoubtedly get an amazing new view of the universe.
Track 7: Optical Astronomy
Optical telescopes are the most conspicuous, as they are fundamentally the same as those you use in your own particular lawn. Optical space science gives both the most amazing pictures we see and the most essential data we think about our nearby planetary group, the Milky Way, and every one of the systems encompassing us.
Optical space science is constrained by both the relative restriction of the optical range and the way that the Earth's own climate shut out and skips around some of this light, misshaping the picture we see. The human nearness is likewise an issue for optical seeing, as light contamination additionally extremely restrains the nature of information you can gather. Along these lines, observatories are typically situated in spots with a low rate of day by day overcast cover (less mists = additionally watching), far from towns and city (less light contamination = better watching), and ordinarily at high heights (less environment = less scrambling).
Given these confinements, space-based observatories, (for example, Hubble) will give clearer pictures, and better quality data about the items. In any case, putting a telescope in space is a troublesome, tedious and expensive practice. All things considered, a great deal of progressions in the field of optical cosmology have been centered around earthbound based observatories.
Track 8: Cosmology
Our universe which is both ancient and vast and is expanding in an accelerating manner day by day and the dark energy adds another bit to the puzzle. The scientists have named the puzzle as Cosmology.
Cosmology is the scientific study of origin, evolution, and eventual fate of the universe. Cosmology involves in the formation of these theories or hypothesis about the universe which helps them to predict a phenomenon that can be tested with observations and depending upon that observation the theories are then modified or are discarded. After various advances in the field since 1990 , including microwaves background, distant supernovae and galaxy redshift surveys have helped in developing various standard models of cosmology. This model require a large amount of dark matter and dark energy who’s nature is not understood but the developed model will give detailed prediction that are excellent agreement with many diverse observations
Track 9: Particle Physics – Higgs Boson
Particle Physics which is also called as high energy physics is the branch of the physics that deals with the studies of nature of particles that contains radiation and matter. As of now, we know of 12 fundamental particles: six quarks and six leptons.
12 fundamental particles that we know till now and 4 forces.(Source: Wikipedia)
From the current dominating theory explaining the fundamental particles and the fields with their dynamics is the Standard Model. This model was first developed in 1970. The latest finding by using this model is “Higgs Boson” or also called as “God Particle”.
CERN’s main focus is particle physics. Scientists at CERN use the most powerful particle accelerator and detectors to test the predictions and the limit of the Standard Model. The model is only capable to provide 4% of the known universe.
Higgs Boson, a particle so difficult to produce due to energy requirement. After 40 years of constant research, world’s most expensive and complex experiments facilities, CERN’s Large Hadron Collider on 4 July 2012 gave the elementary particle to the Standard model of Particle Physics. A particle with a mass of 126 GeV (Giga-electron Volt) is a manifestation to the Brout-Englert-Higgs mechanism having parity and fundamental spin as two of it’s attributes was named as “Higgs Boson” or “God Particle”. The particle is associated with the Higgs field that physicists think permeates all of space-time and helps give other particles their mass.
Track 10: Astrobiology
The word Astrobiology is derived from two diverse fields of study: Astronomy and Biology. Astrobiology , sometimes also referred as space biology is the study of the life in this universe. It helps in finding amount the life that exists beyond the life of earth. To understand, it requires a nature of environments, a planetary system and a stellar process. To understand the above fields, astrobiology makes use of physics, chemistry, biology, molecular biology, ecology, geology, geography, and planetary science. Astrobiologyists from different disciplines work together to examine complex questions about the origin of life, evolution of life, environment required to survive and so on.
To answer all the above questions the research has a significant impact on agencies like NASA which launched Kepler Mission in 2009 and the European Space Agency launched COROT space mission in 2006. The goals of both the missions is not just to find a earth-like-planet but to also detect light from them to study spectroscopically. By examining the spectra of the light it will be possible to compose extrasolar planet’s atmosphere which is then created virtually in Virtual Planet Laboratory at NASA.
With the new generation of telescopes like Atacama Large Millimeter Array(ALMA) and European Space Agency’s far-infrared space telescope Hershel has helped biologist to study the distribution of abiotic organic molecules in the star forming regions. Various studies have also shown that life is possible in extraterrestrial environments on the Earth.
Astrobiology is already making a major contribution for research in NASA by sending the rover to Mars in the year 2015. And by the year 2020 Astrobiologists are planning for next Mars Rover mission.
Track 11: Biophysics
Biophysics is an interdisciplinary science which combines Biology and Physics and studies the life from their atom to organization level. Biophysics is a bridge between Biology and Physics. Biophysical research overlaps with biochemistry, physical chemistry, nanotechnology etc.
Biophysics discovers how atoms are arranged to work in DNA and proteins.
Protein molecules perform the body’s chemical reactions. They push and pull in the muscles that move your limbs. Proteins make the parts of your eyes, ears, nose, and skin that sense your environment. They turn food into energy and light into vision. They become immunity to individual’s illness. Proteins repair what is broken inside of cells, and regulate growth. They fire the electrical signals in brain. They read the DNA blueprints in body and copy the DNA for future generations.
Biophysicists are discovering how proteins work. Scientists know exactly where the thousands of atoms are located in more than 50,000 different proteins. Every year, over a million scientists and students from all over the world, from physicists to medical practitioners, use these protein structures for discovering how biological machines work, in health and also in diseases.
Track 12: Astrochemistry
Astrochemistry is the study of chemical elements and molecules in the universe and their interaction with each other via radiation. It is again an interdisciplinary which contains Chemistry and Astronomy. The research in this area includes gathering of the spectroscopic information from air, ground and space to recreate the identical environment to space and study on it.
The Astrochemistry Lab which is located in the Space Science and Astrophysics Branch (SSA) of the Space Science and Astrobiology Division(SSA) at NASA’s Ames Research Center(ARC) mainly researches upon the physical and the chemical properties of interstellar polycyclic hydrocarbons aerosols in the planetary atmosphere, ice mantles on interstellar grains and surface ices on comets. Extraterrestrial material analogs are produced in this laboratory under conditions realistically close to space environments and range from molecules and ions in gas-phase interstellar clouds and planetary atmospheres to interstellar, cometary, and planetary ices and dust. The materials are studied using analytical techniques such as photonic spectroscopy, time-of-flight mass spectrometry and gas chromatography.
Track 13: Astromicrobiology
Astromicrobiology is the study of microorganisms from the outer space. It is an interdisciplinary approach of astronomy and microbiology. As microorganism are the most widespread life forms on earth so it is necessary to study their life forms and try to create another ecosystem identical to them so that it will be easier to check for the existence of life. Also small and simple cells evolve a bit faster as compared to a larger cell and have increased likelihood of being transported from one planet to another via panspermia hypothesis.
With the NASA’s Viking program in 1970, two mars rovers were sent , each equipped with a robotic arm and to collect samples and bring back to earth, was the first step towards Astrobiology and searching for life on other planets excluding earth. The current mission that is under process is the Mars rover by Mars Science Laboratory by NASA.
In coming years various missions like ExoMars, Mars 202 Rover, Red Dragon, Ice Breaker Life are going to be executed to get some more insights and information about the planet and the living conditions in it.
Track 14: X-Ray Astronomy
X-rays are a form of light, but much more energetic than the light detected by our eyes. The energy of an X-ray photon (light particle) is ~1000 times that of a photon of visible light. They are part of the electromagnetic spectrum which includes visible light, radio waves, microwaves and infrared radiation. X-rays are so energetic that they pass straight through many materials, which is why they are used in hospitals to image bones to check for breaks and fractures. They are absorbed better by materials which are dense, and so, when used in hospitals, they are stopped more by the bone and any metal (e.g. dental fillings) then the fleshy parts of the body. The X-rays cause the film to be exposed, and so if they are blocked, the film remains dark, hence producing a shadow of the denser parts of the body.
X-ray astronomy is an observational branch of astronomy which deals with the study of X ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere,. Scientists hypothesized that X-rays from stellar sources in our galaxy were primarily from a so-called "X-ray binaries." The X-ray binaries consist of a neutron star in a binary system with a normal star. The X-rays in these systems originate from material traveling from the normal star to the neutron star in a process called acceleration. The binary nature of the system allowed astronomers to measure the mass of the neutron star. For other systems, the inferred mass of the X-ray emitting object supported the idea of the existence of black holes, because they were too massive to be neutron stars. Other systems displayed a characteristic X-ray pulse, just as pulsars had been found to do in the radio regime, which allowed a determination of the spin rate of the neutron star. Finally, some of these galactic X-ray sources were found to be highly variable. In fact, some sources would appear in the sky, remain bright for a few weeks, and then fade again from view. Such sources are called X-ray transients.
Track 15: Aerospace Engineering
Aerospace engineering deals with designing and building machines that fly. It is one of the newest branches of engineering, and began in the 19th century with the first experiments in powered flight. As technology progressed, two specialties emerged; aeronautical engineering, which involves designing aircraft such as powered lighter-than-air craft, gliders, fixed-wing airplanes and jets, autogyros, and helicopters; and astronautical engineering, which focuses on the design and development of spacecraft.
An Aerospace engineer designs aircraft, spacecraft, satellites and missiles, according to the BLS. In addition, these engineers test prototypes to make sure that they function according to plans. These professionals also design components and subassemblies for these craft; those parts include engines, airframes, wings, landing gear, control systems and instruments. Additionally, engineers may perform or write the specifications for destructive and nondestructive testing for strength, functionality, reliability, and long-term durability of aircraft and parts.
Why to attend?
The aim of Astronomy Congress 2018 meeting is to bring together scientists to present and exchange breakthrough ideas relating to Astronomy and related fields. It promotes top-level research and to globalize the quality research in general, thus making discussions, presentations and contributions more internationally competitive.
Major Astronomy and Associations around the Globe:
The Royal Astronomical Society
International Astronomical Union
Amateur Astronomers Association of Pittsburgh
International Meteor Organization
The Planetary Society
Astronomical Association of Queensland
Astronomical Institute of Amsterdam
Astronomical Society at the University of Illinois
Astronomical Society of Palm Beaches
Major Astrophysics Associations in Japan:
National Astronomical Observatory of Japan
Junior/Senior research fellows
Directors of companies
Members of different physics associations.
Top Universities in Japan
The University of Tokyo
University of Tsukuba
Tokyo Institute of Technology
Glance at Market of Astrophysics in japan
The economy of Japan is the third-largest in the world by nominal GDP and the fourth-largest by purchasing power parity (PPP)and is the world's second largest developed economy to the International Monetary Fund, the country's per capita GDP (PPP) was at $37,519, the 28th highest in 2014, down from the 22nd position in 2012. Japan is the world's third largest automobile manufacturing country has the largest electronics goods industry, and is often ranked among the world's most innovative countries leading several measures of global patent filings. With the GDP that high, japan is able to perform some serious space research experiments.
Countries investing the most in space program
- Computational Astrophysics
- Dark Matter, Dark Energy, and Black Holes
- Gravitational Physics
- Neutrino Astronomy
- Optical Astronomy
- Particle Physics – Higgs Boson
- X-Ray Astronomy
- Aerospace Engineering
- Robotics and Artificial Intelligence
To share your views and research, please click here to register for the Conference. | 0.886722 | 3.050427 |
From: University of California Berkeley
Posted: Tuesday, March 11, 2003
BERKELEY -- Ask any kid how many planets are in our solar
system, and you'll get a firm answer: nine.
But knock on a few doors in Berkeley's astronomy
department, and you'll hear, amid the hemming and hawing,
a whole range of numbers.
Professor Gibor Basri, who plans soon to propose a formal definition of a planet to the international body that names astronomical objects, argues that there are at least 14 planets, and perhaps as many as 20. To the well-known list of nine he adds several large asteroids and more distant objects from the rocky swarm called the Kuiper Belt circling beyond the orbit of Neptune.
Professor Imke de Pater and Assistant Professor Eugene Chiang, on the other hand, toss out Pluto without a backward glance. It's just a big rock, they say, a former member of the Kuiper Belt, puppy-dogging Neptune around the solar system.
Not so fast, says Professor Alex Filippenko. The International Astronomical Union (IAU), which rules on names for astronomical bodies, has officially said that Pluto remains a planet, at least for the time being. Thus, officially, there are nine. He cavils a bit, however, making it clear to his students that Pluto is "more fundamentally a Kuiper Belt Object (KBO), though an unusually large one."
Professor Geoffrey Marcy and research astronomer Debra Fischer, both "planet hunters" within the department, also prefer to keep the number at nine, noting that the sun, though it probably had 12 or 14 planets in the past, will in five billion years probably lose Mercury and Pluto, bringing the count down to seven.
Moons, fusors, brown dwarfs
This difference of opinion within the astronomy department is part of a larger debate in the astronomical community over what constitutes a planet. It provides endless hours of beer-hall debate and Friday-afternoon tea-time chat, with little hope for resolution in the near future.
"It's something of an embarrassment that we currently have no definition of what a planet is," Basri said. "People like to classify things. We live on a planet; it would be nice to know what that was."
The IAU has sidestepped any formal definition, largely, Basri says, because a good definition would eject Pluto from the list and relegate it to a "minor planet" or, even worse, a comet. Basri has come up with a definition that keeps Pluto in the fold, but necessarily brings in other objects that until now have not been considered planets -- objects with names such as Vesta, Pallas and Ceres, now considered asteroids, or KBOs such as Varuna.
He's now preparing a formal definition to put before the IAU Working Group on Extra-Solar Planets, and has posted an article on his Web site that lays out his definition and arguments as to why it should be adopted.
"By 10 years from now, I'd be a little surprised if the IAU had not adopted something along the lines I'm proposing," Basri said. "It's reasonable."
Most astronomers and the IAU agree that planets should be orbiting a star -- or more precisely, an object that is big enough to ignite hydrogen fusion in its core (what Basri calls a fusor). The IAU Working Group also excludes anything, like a star, that is big enough to manage core fusion itself. The consensus thus excludes moons, even those such as Ganymede, which is almost as large as Mars but which happens to be orbiting the planet Jupiter rather than a star.
The definition also excludes failed stars called brown dwarfs, which are too small to be stars but too big to be planets. These are the subjects of Basri's research. In 1995, he was the first to obtain a spectrum confirming that brown dwarfs exist, and he has concentrated on tests that can distinguish brown dwarfs from low-mass stars.
This work naturally led him to focus on mass as a way to distinguish between planets and non-planets. He proposes a natural upper limit for a "planetary mass object" of about 13 times the mass of Jupiter, or about 4,000 Earths. At this size, gravity will cause an object to give off heat, as happens with Jupiter, but the pressure at the core is a bit too cool to fuse the element easiest to fuse, deuterium or heavy hydrogen. Because anything bigger, including stars and brown dwarfs, is able to fuse deuterium, Basri argues that it makes sense to define a "planetary mass object" -- or planemo, as he has dubbed them -- as an object too small to achieve any fusion.
A natural lower limit to the mass of a planemo, Basri says, would be a body large enough for self-gravity to squash it into a round shape. On average, that would be about 700 kilometers in diameter, though that number is squishy -- an iron wrecking ball like Mercury could be smaller and round, while icy planets like Pluto would need to be larger to achieve roundness. This limit excludes all but a few asteroids and KBOs, most of which bear a resemblance to potatoes.
"The upper limit of a planetary mass is the fusion boundary, and the lower limit is roundness," he said. "This definition does not depend on either circumstance or origin."
Basri then throws in the other traditional property of planets to reach a final definition: a planet is a planemo orbiting a fusor.
"If you take this definition," he says, "you don't have any trouble what to call these objects," including many of the new extrasolar planets that Geoff Marcy and Debra Fischer are discovering.
Marcy disagrees. In his search for planets around other stars -- he and his colleagues have found about two-thirds of all known extrasolar planets -- he has come across planet systems that aren't so neat. Two years ago, his team discovered two bodies orbiting the star HD168443 -- one with a mass about 7.6 times that of Jupiter, and one 17 times Jupiter. Basri would call this a planetary system with one large gas planet and one brown dwarf companion -- sort of a failed binary star system, where one "star" wasn't big enough to make the grade.
Talk show host David Letterman, an astronomy buff, quizzed Marcy about these two objects when he was a guest in April 2001. Marcy admitted that the larger of the objects is "so large it doesn't even seem like a planet. We don't know what to call it. Is it a planet? Is it a star? Is it something in between? We're befuddled."
"Well, what the hell are we going to do?" asked Letterman.
"We're screwed," Marcy admitted.
"Run for your life, everybody," Letterman quipped.
Marcy and Fischer believe that consideration should be given to how an object formed, with the name planet reserved for objects forming in accretion disks around a star. In the early dust and gas cloud from which stars form, fluffy dust bunnies coalesce into bigger dust bunnies, until they're big enough for their own gravity to actively sweep in even more stuff. Anything that forms this way around a star should be called a planet, they argue. Stars and brown dwarfs form differently, in the middle of a swirling nebula, thus providing a way to differentiate planets from the rest.
But, Basri counters, "I don't think we should define what an object is based on how it formed, because I don't think we know enough about formation mechanisms, and you can't easily observe how things form."
No one now knows how brown dwarfs form, and to throw a wrench into things, there's some doubt that Jupiter formed the way the other planets did. Asks Basri, not entirely rhetorically: "Is Geoff going to stop calling Jupiter a planet if he discovers it was formed the way a brown dwarf is?"
A taxonomy of planets
Marcy and Fischer believe that assigning a firm definition to planet may also lock astronomers into a taxonomy that will quickly become obsolete as we learn more about the varieties of planets in the galaxy.
"I think any time you try to draw sharp lines you get into trouble," said Fischer. "We should be a lot humbler and say we are calling these things planets because we have this historical precedent, this historical inertia. Let's admit that at either end, the high-mass end and low-mass end, this has been completely arbitrary, and that some things don't fit with our classification scheme."
"It's way too early to define a planet," Marcy said. "No one would have predicted 10 years ago that we'd have any extrasolar planets. Even though we have now found more than 100 of them, these are still the early days in planet hunting."
He anticipates that 70-80 percent of all stars will be found to have planets, most of these in multiple planet systems. And even though no Earth-sized planets have yet been discovered, the Milky Way galaxy could well harbor hundreds of millions of Earths.
"It's a little arrogant, I think, for us to imagine that we understand what the full spectrum is going to shake out to be. Are we really in the ultimate position right now where we should redefine things, because it freezes it in again? In a decade or two it may look incomplete again," Fischer said.
Basri scoffs at these objections. "It's like saying we shouldn't define what a star is until we understand all about star formation and weird binary stars, and so on. If we define a planet based on the basic observable properties of these objects, people can later apply all sorts of adjectives to them as they are understood better, without changing what they are basically talking about."
When Neptune dominates
Imke de Pater, who uses both radio telescopes and optical telescopes to study planets such as Jupiter and Neptune and volcanic activity on Jupiter's moon Io, also thinks that how a body forms should not make a difference in deciding whether a body is a planet.
"I would say a planet is a body in orbit about a star, but not forming part of a larger swarm, like the asteroids in the asteroid belt or the Kuiper Belt Objects," she proposes. "A planet also would have to be in a stable orbit for a few billion years -- it shouldn't be a KBO in transit to becoming a comet."
Eugene Chiang, a new member of Marcy's Center for Integrative Planetary Studies, knows these swarms well. He's part of a national team called the Deep Ecliptic Survey that is scanning the plane of the solar system in search of as many Kuiper Belt Objects as it can find. They've discovered some 250 since 1998, bringing the total known KBOs to about 600, all swarming beyond Neptune's orbit, 30 times farther from the sun than Earth.
Pluto, Chiang notes, is the largest of the Kuiper Belt Objects, and its orbit, like that of all the KBOs, is dominated by Neptune. In fact, it orbits in lock-step with Neptune: Pluto goes around the sun twice for every three Neptune orbits. A large class of such objects in the Kuiper Belt has been dubbed Plutinos because they also inhabit this so-called 3:2 resonance. Of the 100 KBOs that Chiang has tracked well, 25 percent are in resonant orbits with Neptune.
"The asteroid belt is dominated by Jupiter, and the Kuiper Belt is dominated by Neptune," he says, and objects in neither of these belts should be called planets. In fact, because the Kuiper Belt is the source of many short-period comets that plunge through the interior solar system, Pluto could even be called a comet.
Chiang's interest in the KBOs with resonant orbits comes from his theory that planets migrate inward or outward after their initial formation. The many objects in resonant orbits with Neptune argue that it has migrated outward, he says, shepherding the KBOs with it and locking many into resonances. The theory could explain some of the bizarre planetary systems that Marcy, Fischer, Paul Butler and others have found, in which large gas planets seem to be sitting awfully close to their star, in contrast to our own solar system, where the gas giants are far out. Early in a system's history, gravitational interactions between large gas planets and the gaseous disk or small objects called planetesimals can drive planets in or out, he said.
The case for Pluto
None the less, Basri feels that Pluto needs to remain a planet, partly for historical reasons, but primarily because it fits a consistent and reasonable definition of a planetary mass object orbiting a fusor. And if we include Pluto, how can we exclude other Kuiper Belt Objects and asteroids that look almost identical? There's really no difference between Mercury and Ceres, he says, so any consistent definition of a planet would have to include both. He suggests calling the eight undisputed planets "major planets" and the others, including Pluto, "minor planets" -- a usage once applied to the asteroids before their numbers skyrocketed. But they'd all still be planets.
"I've thought about this for two years now, and I think I've seen all the arguments, I've chewed on them for a long time, I've played with them. So I'm ready," he said. "That doesn't mean anyone else is."
Basri's proposed definition means that the number of planets in the solar system will continue to grow as more large objects are discovered in the Kuiper Belt. The Caltech team that discovered the largest known KBO last year -- a body half the diameter of Pluto that they named Quaoar (kwah-o-wahr), after a creation force in California Indian mythology -- estimates that they "should be able to find 5 to 10 more of these really big Kuiper Belt Objects over the next couple of years, including perhaps a couple [of] 'super-Plutos,'" according to their Web site. That means an eventual 25 planets.
Someday kids may be stumping their parents with planet names such as Vesta, Quaoar and Varuna, if not Ixion or Radamanthus. They'll be around for a while -- at least a few billion years -- so you might as well get used to them.
What's in a name? Help us remember
For ages, teachers have been creating mnemonics to help students remember the order of the planets. One well- known version is "My Very Educated Mother Just Sent Us Nine Pizzas." Another variant, mentioned in Robert Heinlein's book "Have Space Suit, Will Travel," goes: "Mother very thoughtfully made a jam sandwich under no protest." (Thoughtfully stands for Terra, Earth's other name.) But with another five (or more) potential planets, it's back to the drawing board. Please send us your mnemonics for the latest solar system lineup: Mercury, Venus, Earth (or Terra), Mars, Vesta, Ceres, Pallas, Jupiter, Saturn, Uranus, Neptune, Pluto, Quaoar and Varuna. The best submissions will be featured in a future issue of the NewsCenter,
* Gibor Basri's thoughts on defining planets http://astron.berkeley.edu/%7Ebasri/defineplanet/index.html * Geoff Marcy's Web site for extrasolar planets http://exoplanets.org/
[NOTE: Images supporting this release are available at http://www.berkeley.edu/news/media/releases/2003/02/26_planet.shtml ]
// end // | 0.935899 | 3.383084 |
- Open Access
On the origin of jets from disc-accreting magnetized stars
Computational Astrophysics and Cosmology volume 1, Article number: 3 (2014)
A brief review of the origin of jets from disc-accreting rotating magnetized stars is given. In most models, the interior of the disc is characterized by a turbulent viscosity and magnetic diffusivity (‘alpha’ discs) whereas the coronal region outside the disc is treated using ideal magnetohydrodynamics (MHD). Extensive MHD simulations have established the occurrence of long-lasting outflows in the case of both slowly and rapidly rotating stars. (1) Slowly rotating stars exhibit a new type of outflow, conical winds. Conical winds are generated when stellar magnetic flux is bunched up by the inward motion of the accretion disc. Near their region of origin, the winds have a thin conical shell shape with half opening angle of ∼30∘. At large distances, their toroidal magnetic field collimates the outflow forming current carrying, matter dominated jets. These winds are predominantly magnetically and not centrifugally driven. About 10-30% of the disc matter from the inner disc is launched in the conical wind. Conical winds may be responsible for episodic as well as long lasting outflows in different types of stars. (2) Rapidly rotating stars in the ‘propeller regime’ exhibit twocomponent outflows. One component is similar to the matter dominated conical wind, where a large fraction of the disc matter may be ejected in this regime. The second component is a high-velocity, low-density magnetically dominated axial jet where matter flows along the open polar field lines of the star. The axial jet has a mass flux of about 10% that of the conical wind, but its energy flux, due to the Poynting flux, can be as large as for the conical wind. The jet’s magnetically dominated angular momentum flux causes the star to spin down rapidly. Propeller-driven outflows may be responsible for protostellar jets and their rapid spin-down.
When the artificial requirement of symmetry about the equatorial plane is dropped, the conical winds are found to come alternately from one side of the disc and then the other, even for the case where the stellar magnetic field is a centered axisymmetric dipole.
Recent MHD simulations of disc accretion to rotating stars in the propeller regime have been done with no turbulent viscosity and no diffusivity. The strong turbulence observed is due to the magneto-rotational instability. This turbulence drives accretion in the disc and leads to episodic conical winds and jets.
Outflows in the form of jets and winds are observed from many disc accreting objects ranging from young stars to systems with white dwarfs, neutron stars and black holes. A large body of observations exists for outflows from young stars at different stages of their evolution, ranging from protostars, where powerful collimated outflows - jets - are observed, to classical T Tauri stars (CTTSs) where the outflows are weaker and often less collimated (see review by Ray et al. ). Correlation between the disc’s radiated power and the jet power has been found in many CTTSs (Cabrit et al. ; Hartigan et al. ). A significant number of CTTSs show signs of outflows in spectral lines, in particular in He I where two distinct components of outflows had been found (Edwards et al. , , ; Kwan et al. ). Outflows are also observed from accreting compact stars such as accreting white dwarfs in symbiotic binaries (Sokoloski and Kenyon ), or from the vicinity of neutron stars, such as from Circinus X-1 (Heinz et al. ).
Different theoretical models have been proposed to explain the outflows from protostars and CTTSs (see review by Ferreira et al. ). The commonly favored model for the origin of protostellar jets and outflows are the radially distributed magneto-centrifugal disc winds which originate from discs threaded by a poloidal magnetic field (Blandford and Payne ; Königl and Pudritz ). MHD simulations disc winds were pioneered by Shibata and Uchida () and Uchida and Shibata () who used a Lax-Wendroff method to solve the axisymmetric MHD equations for a sub-Keplerian disc initially threaded by a vertical magnetic field. Subsequently, a large number of MHD simulation studies of the disc winds have been carried out with different codes and different assumptions (e.g., Ustyugova et al. , ; Ouyed and Pudritz ; Romanova et al. ; Krasnopolsky et al. ; Casse and Keppens ; Ferreira et al. ; Matt and Pudritz [2008a], [2008b]; Tzeferacos et al. ).
A less favored model for the origin of protostellar jets discussed in this review is one where the jets originate from the innermost region of the accretion disc (Lovelace et al. ) or the disc/magnetosphere boundary. This model is related to the X-wind model (Shu et al. , ; Najita and Shu ; Cai et al. ) where the outflow originates from the vicinity of the disc-magnetosphere boundary. Progress in understanding the theoretical models has come from MHD simulations of accretion discs around rotating magnetized stars as discussed below. Laboratory experiments are also providing insights into jet formation processes (Hsu and Bellan ; Lebedev et al. ) but these are not discussed here.
Outflows or jets from the disc-magnetosphere boundary were found in early axisymmetric MHD simulations by Hayashi et al. () and Miller and Stone (). A one-time episode of outflows from the inner disc and inflation of the innermost field lines connecting the star and the disc were observed for a few dynamical time-scales. Somewhat longer simulation runs were performed by Goodson et al. (, ), Hirose et al. (), Matt et al. () and Küker et al. () where several episodes of field inflation and outflows were observed. These simulations hinted at a possible long-term nature for the outflows. However, the simulations were not sufficiently long to establish the behavior of the outflows. MHD simulations showing long-lasting (thousands of orbits of the inner disc) outflows from the disc-magnetosphere have been obtained by our group (Romanova et al. ; Lii et al. , ) and independently by Fendt (). We obtained these outflows/jets in two main cases: (1) where the star rotates slowly but the field lines are bunched up into an X-type configuration, and (2) where the star rotates rapidly, in the ‘propeller regime’ (Illarionov and Sunyaev ; Alpar and Shaham ; Lovelace et al. ). Field bunching occurs for conditions where the viscosity is larger than the magnetic diffusivity. Figure 1 shows sketches of the equatorial angular rotation rate of the plasma in the two cases. Here, is the radius of the star; is the magnetospheric radius where the kinetic energy density of the disc matter is about equal to the energy density of the magnetic field; and is the co-rotation radius where the angular rotation rate of the star equals that of the Keplerian disc . For a slowly rotating star whereas for a rapidly rotating star in the propeller regime .
Figure 2 shows examples of the outflows in the two cases. In both cases, two-component outflows are observed: One component originates at the inner edge of the disc near and has a narrow-shell conical shape close to the disc and therefore is termed a ‘conical wind’. It is matter dominated but can become collimated at large distances due to its toroidal magnetic field. The other component is a magnetically dominated high-velocity ‘axial jet’ which flows along the open stellar magnetic field lines. The axial jet may be very strong in the propeller regime. A full discussion of the simulations and analysis can be found in Romanova et al. () and Lii et al. ().
The simulation codes used by our US/Russia group have been extensively tested and refined in many respects over the past fifteen years. The tests include the different well-known shock problems described for example by Mignone et al. () in regard to the testing of the PLUTO code as well as the magnetic rotor tests described by Romanova et al. (). More importantly, our group has pioneered the detailed comparison of MHD simulation results (Ustyugova et al. ) with the analytic theory of stationary axisymmetric MHD flows (Lovelace et al. ). Furthermore, detailed analysis of the simulations have been made to evaluate the different forces acting to drive outflows and jets (e.g., Lii et al. ). A major effort by our group has been to implement physically consistent boundary conditions at the outer boundaries of the simulation regions. We were the first to point out the necessity of having the fast-magnetosonic Mach cone of an outflow pointing outwards from the simulation region (Ustyugova et al. ). A number of published MHD simulations of jets in long axial cylindrical regions violate this requirement and are therefore unphysical.
Section 2 describes the simulations. Section 3 discusses the conical winds and axial jets, the driving and collimation forces, and the variability of the winds and jets. Section 4 discusses lopsided jets. Section 5 gives the conclusions.
2 MHD simulations
We simulate the outflows resulting from disc-magnetosphere interaction by solving the equations of axisymmetric MHD on grids using a Godunov type method. Outside of the disc the flow is described by the equations of ideal MHD. Inside the disc the flow is described by the equations of viscous, resistive MHD. In an inertial reference frame the equations are:
Here, ρ is the density, S is the specific entropy, v is the flow velocity, B is the magnetic field, is the magnetic diffusivity, is the momentum flux-density tensor, Q is the rate of change of entropy per unit volume, and is the gravitational acceleration due to the star which has mass M. In the simulations reviewed here it is assumed that the viscous plus Ohmic heating is balanced by radiative cooling so that . Most of the volume of the simulated flows does not have shocks and there is no shock heating; however, at the surface of the star where the funnel flows impact the star’s surface there are strong shocks and the shock heating is included (Koldoba et al. ). The total mass of the disc is assumed to be negligible compared to M. Here, is the sum of the ideal plasma terms and the α-viscosity terms discussed in the next paragraph. The plasma is considered to be an ideal gas with adiabatic index , and . We use spherical coordinates with θ measured from the symmetry axis. The equations in spherical coordinates are given in Ustyugova et al. ().
Both the viscosity and the magnetic diffusivity of the disc plasma are considered to be due to turbulent fluctuations of the velocity and the magnetic field. Both effects are non-zero only inside the disc as determined by a density threshold. The microscopic transport coefficients are replaced by turbulent coefficients. The values of these coefficients are assumed to be given by the α-model of Shakura and Sunyaev (), where the coefficient of the turbulent kinematic viscosity is , where is the isothermal sound speed and is the Keplerian angular velocity. We take into account the viscous stress terms and (Lii et al. ). Similarly, the coefficient of the turbulent magnetic diffusivity . Here, and are dimensionless coefficients which are treated as parameters of the model. The inward advection of matter and large-scale magnetic field in accretion discs with different values has been studied by Dyda et al. (). Note that shearing box simulations by Guan and Gammie () suggest that . In the simulation studies of our group we have studied cases with in the ranges 0.03-0.3. For these values the viscosity and diffusivity are much larger than the numerical values due to the finite grids.
The MHD equations are solved in dimensionless form so that the results can be readily applied to different accreting stars (see Table 1). Equations (1)-(4) have been integrated numerically in spherical coordinates using a Godunov-type numerical scheme. The flux densities of the different quantities are calculated using an eight-wave Roe-type approximate Riemann solver analogous to one described by Powell et al. (). The calculations were done in the region , . Matter flowing into the star is absorbed. The grid is uniform in the θ-direction with cells. The cells in the radial direction have () so that the poloidal-plane cells are curvilinear rectangles with approximately equal sides. This choice results in high spatial resolution near the star where the disc-magnetosphere interaction takes place while also permitting a large simulation region. We have used a range of resolutions going from to in order to establish the numerical convergence of our results.
3 Conical winds and axial jets
A large number of simulations were done in order to understand the origin and nature of conical winds. All of the key parameters were varied in order to ensure that there is no special dependence on any parameter. We observed that the formation of conical winds is a common phenomenon for a wide range of parameters. They are most persistent and strong in cases where the viscosity and diffusivity coefficients are not very small, , . Another important condition is that ; that is, the magnetic Prandtl number of the turbulence, . This condition favors the bunching of the stellar magnetic field by the accretion flow.
The velocities in the conical wind component are similar to those in conical winds around slowly rotating stars. Matter launched from the disc-magnetosphere region initially has an approximately Keplerian azimuthal velocity, . It is gradually accelerated to poloidal velocities and the azimuthal velocity decreases. The flow has a high density and carries most of the disc mass into the outflows. The situation is the opposite in the axial jet component where the density is 102-103 times lower, while the poloidal and total velocities are significantly higher. Thus we find a two-component outflow: a matter dominated conical wind and a magnetically dominated axial jet.
We observe conical winds in both slowly and rapidly rotating stars. In both cases, matter in the conical winds passes through the Alfvén surface (and shortly thereafter through the fast magnetosonic point), beyond which the flow is matter-dominated in the sense that the energy flow is carried mainly by the matter. The situation is different for the axial jet component where the flow is sub-Alfvénic within the simulation region. For this component the energy flow is carried by the Poynting flux and the angular moment flow is carried by the magnetic field. X-ray observations of the jet from the protostellar object L1551 IRS 5 suggest a high-velocity, highly collimated inner jet and a lower-velocity, less-collimated outer outflow component (Schneider et al. ).
Collimation and driving of the outflows Figure 3 shows the long-distance development of a conical wind from a slowly rotating star. At large distances the conical wind becomes collimated. To understand the collimation we analyzed total force (per unit mass) perpendicular to a poloidal magnetic field line (Lii et al. ). For distances beyond the Alfvén surface of the flow this force is approximately
(Ustyugova et al. ). Here, Θ is the angle between the poloidal magnetic field and the symmetry axis, s is the arc length along the poloidal field line, n is a coordinate normal to the poloidal field, and the p-subscripts indicate the poloidal component of a vector. Once the jet begins to collimate, the curvature term also becomes negligible. The magnetic force may act to either collimate or decollimate the jet, depending on the relative magnitudes of the toroidal gradient (which collimates the outflow) and poloidal gradient (which ‘decollimates’). In our simulations, the collimation of the matter implies that the magnetic hoop stress is larger than the poloidal field gradient. Thus the main perpendicular forces acting in the jet are the collimating effect of the toroidal magnetic field and the decollimating effect of the centrifugal force and the gradient of . The collimated effect of dominates. Note that in MKS units is the poloidal current flowing through a surface of radius r from colatitude zero to θ. For the jets from young stars this current is of the order of .
The driving force for the outflow is simply the force parallel to the poloidal magnetic field of the flow . This is obtained by taking the dot product of the Euler equation with the unit vector which is parallel to the poloidal magnetic field line . The derivation by Ustyugova et al. () gives
Here, the terms on the right-hand side correspond to the pressure, gravitational, centrifugal and magnetic forces, respectively denoted . The pressure gradient force, , dominates within the disk. The matter in the disk is approximately in Keplerian rotation such that the sum of the gravitational and centrifugal forces roughly cancel (). Near the slowly rotating star, however, the matter is strongly coupled to the stellar magnetic field and the disk orbits at sub-Keplerian speeds, giving . The magnetic driving force (the last term of Eq. (6)) can be expanded as
(Lovelace et al. ). Figure 4 shows the variation of the total force , the gravitational plus centrifugal force, and the magnetic force along a representative field line. This analysis establishes that the predominant driving force for the outflow is the magnetic force (Eq. (7)) and not the centrifugal force. This in agreement with the analysis of Lovelace et al. ().
Variability For both rapidly and slowly rotating stars the magnetic field lines connecting the disc and the star have the tendency to inflate and open (Lovelace et al. ). Quasi-periodic reconstruction of the magnetosphere due to inflation and reconnection has been discussed theoretically (Aly and Kuijpers ) and has been observed in a number of axisymmetric simulations (Hirose et al. ; Goodson et al. , ; Matt et al. ; Romanova et al. ). Goodson and Winglee () discuss the physics of inflation cycles. They have shown that each cycle of inflation consists of a period of matter accumulation near the magnetosphere, diffusion of this matter through the magnetospheric field, inflation of the corresponding field lines, accretion of some matter onto the star, and outflow of some matter as winds, with subsequent expansion of the magnetosphere. There simulations show 5-6 cycles of inflation and reconnection. Our simulations often show 30-50 cycles of inflation and reconnection.
Kurosawa and Romanova () have calculated spectra from modeled conical winds and accretion funnels combining the 3D MHD simulations with 3D radiative transfer code TORUS. They have shown that conical winds may explain different features in the hydrogen spectral lines, in the He I line and also a relatively narrow, low-velocity blue-shifted absorption components in the He I λ 10830 which is often seen in observations (Kurosawa et al. ). Further, the 3D MHD+3D radiative transfer codes have been used to model the young star V2129 Oph, where the parameters of the star including the surface magnetic field distribution are known (Alencar et al. ). The spectrum in several Hydrogen lines was calculated and compared it with observed spectrum. A good match was obtained between the modeled and observed spectra (Alencar et al. ).
4 Lopsided jets and outflows from discs
There is clear evidence, mainly from Hubble Space Telescope (HST) observations, of the asymmetry between the approaching and receding jets from a number of young stars. The objects include the jets in HH 30 (Bacciotti et al. ), RW Aur (Woitas et al. ), TH 28 (Coffey et al. ), and LkHα 233 (Perrin and Graham ). Specifically, the radial speed of the approaching jet may differ by a factor of two from that of the receding jet. For example, for RW Aur the radial redshifted speed is ∼100 km/s whereas the blueshifted radial speed is ∼175 km/s. The mass and momentum fluxes are also significantly different for the approaching and receding jets in a number of cases. It is possible that the observed asymmetry of the jets could be due to differences in the gas densities on the two sides of the source. However, it is more likely that the asymmetry of the outflows arises from the asymmetry of the star’s magnetic field. Substantial observational evidence points to the fact that young stars often have complex magnetic fields consisting of dipole, quadrupole, and higher order poles misaligned with respect to each other and the rotation axis (Jardine et al. ; Donati et al. ). Analysis of the plasma flow around stars with realistic fields have shown that a significant fraction of the star’s magnetic field lines are open and may carry outflows (Gregory et al. ).
The complex magnetic field of a star will destroy the commonly assumed symmetry of the magnetic field and the plasma about the equatorial plane. MHD simulations by Lovelace et al. () fully support the qualitative picture suggested in the sketch in Figure 1 of Lovelace et al. (). The idea of mixing of even and odd symmetry magnetic fields about to get lopsided outflows was proposed earlier by Wang et al. (). The time-scale during which the jet comes from the upper hemisphere is set by the evolution time-scale for the stellar magnetic field. This is determined by the dynamo processes responsible for the generation of the field. Remarkably, once the assumption of symmetry about the equatorial plane is dropped, the conical winds alternately come from one hemisphere and then the other even when the stellar magnetic field is a centered axisymmetric dipole (Lovelace et al. ). Fendt and Sheikhnezami () likewise found that symmetric magnetic field configurations produced asymmetric outflows if there were thermal asymetries in the disc. The time-scale for the ‘flipping’ is the accretion time-scale of the inner part of the disc which is expected to be much less than the evolution time of the star’s magnetic field.
We have revisited the problem of the asymmetry of the jets and outflows using a new axisymmetric code with a high-resolution stretched-grid (Dyda et al.: Bipolar MHD Outflows from T Tauri Stars, in preparation). The star has a radius of 1 in our simulation units, and the first 30 grid cells have lengths . At larger R, the cell lengths are given recursively by . Similarly, in the Z-direction, the first 30 grid cells above and below the equatorial plane have lengths . At larger , the cell lengths are given recursively by . This grid gives high resolution in the region occupied by the disc and by the jet. Here, we present sample results with as simulation region of cells. Figure 5 shows a sparse version of this grid.
The initial magnetic field is taken to be a superposition of a dipole field centered in the star described by the flux function
and a Zanni-type distributed field in the disc,
(Zanni et al. ), where μ is the magnetic moment of the star, is a reference value for the disc field, and m is a dimensionless parameter which controls the initial disc field geometry.
Figure 6 shows a zoomed-in view of results from the new stretched-grid code for an episode of lopsided jet formation for a case where the dipole field of the rotating star is parallel to the disc field in the disc midplane. The outflow from the top side of the disc is at super escape speed velocities with the result that the mass outflow is predominantly from the top side of the disc. During the duration of the run (203 rotation periods of the disc at the corotation radius), the poloidal flux of the disc field advects inward and accumulates in the low-density axial blue region in the figure. In this region there are magnetically collimated Poynting flux outflows of energy and angular momentum in the ±z directions.
Detailed magnetohydrodynamic simulations have established that long-lasting outflows of cold disc matter are ejected into a hot, low-density corona from the disc-magnetosphere boundary in the case of both slowly and rapidly rotating stars. The main results are the following:
For slowly rotating stars a new type of outflow - a conical wind - has been discovered. Matter flows out forming a conical wind which has the shape of a thin conical shell with a half-opening angle . The outflows appear in cases where the magnetic flux of the star is bunched up by the inward accretion flow of the disc. We find that this occurs when the turbulent magnetic Prandtl number (the ratio of viscosity to diffusivity) , and when the viscosity is sufficiently high, .
Winds from the disc-magnetosphere boundary have been proposed earlier by Shu and collaborators and referred to as X-winds (Shu et al. ). In this model, the wind originates from a small region near the corotation radius , while the disc truncation radius (or, the magnetospheric radius ) is only slightly smaller than (, Shu et al. ). It is suggested that excess angular momentum flows from the star to the disc and from there into the X-winds. The model aims to explain the slow rotation of the star and the formation of jets. In the simulations discussed here we have obtained outflows from both slowly and rapidly rotating stars. Both have conical wind components which are reminiscent of X-winds. In some respects the conical winds are similar to X-winds: They both require bunching of the poloidal field lines and show outflows from the inner disc; and they both have high rotation and show gradual poloidal acceleration (e.g., Najita and Shu ).
The main differences are the following: (1) The conical/propeller outflows have two components: a slow high-density conical wind (which can be considered as an analogue of the X-wind), and a fast low-density jet. No jet component is discussed in the X-wind model. (2) Conical winds form around stars with any rotation rate including very slowly rotating stars. They do not require fine tuning of the corotation and truncation radii. For example, bunching of field lines is often expected during periods of enhanced or unstable accretion when the disc comes closer to the surface of the star and . Under this condition conical winds will form. In contrast, X-winds require . (3) The base of the conical wind component in both slowly and rapidly rotating stars is associated with the region where the field lines are bunched up, and not with the corotation radius. (4) X-winds are driven by the centrifugal force, and as a result matter flows over a wide range of directions below the ‘dead zone’ (Shu et al. ; Ostriker and Shu ). In conical winds the matter is driven by the magnetic force (Lovelace et al. ) which acts such that the matter flows into a thin shell with a cone half-angle . The same force tends to collimate the flow.
For rapidly rotating stars in the propeller regime where and where the condition for bunching, , is satisfied we find two distinct outflow components (1) a relatively low-velocity conical wind and (2) a high-velocity axial jet. A significant part of the disc matter and angular momentum flows into the conical winds. At the same time a significant part of the rotational energy of the star flows into the magnetically-dominated axial jet. This regime is particularly relevant to protostars, where the star rotates rapidly and has a high accretion rate. The star spins down rapidly due to the angular momentum flow into the axial jet along the field lines connecting the star and the corona. For typical parameters a protostar spins down in years. The axial jet is powered by the spin-down of the star rather than by disc accretion. The matter fluxes into both components (wind and jet) strongly oscillate due to events of inflation and reconnection. Most powerful outbursts occur every 1-2 months. The interval between outbursts is expected to be longer for smaller diffusivities in the disc. Outbursts are accompanied by higher outflow velocities and stronger self-collimation of both components. Such outbursts may explain the ejection of knots in CTTSs every few months.
When the artificial requirement of symmetry about the equatorial plane is dropped, MHD simulations reveal that the conical winds may alternately come from one side of the disc and then the other even for the case where the stellar magnetic field is a centered axisymmetric dipole (Lovelace et al. ; Fendt and Sheikhnezami ; Dyda et al.: Bipolar MHD Outflows from T Tauri Stars, in preparation).
In recent work we have studied the disc accretion to rotating magnetized stars in the propeller regime using a new code with very high resolution in the region of the disc. In this code no turbulent viscosity or diffusivity is incorporated, but instead strong turbulence occurs due to the magneto-rotational instability. This turbulence drives the accretion and it leads to episodic outflows. The effective values due to the turbulence arising from the magneto-rotational instability (MRI) are found to be ∼0.1. These values are much larger than the numerical viscosity and diffusivity values due to the finite grids used which are ≲0.01. Note however that the characterization of the turbulence by α-values is a rough approximation.
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The authors thank GV Ustyugova and AV Koldoba for the development of the codes used in the reviewed simulations. This research was supported in part by NSF grants AST-1008636 and AST-1211318 and by a NASA ATP grant NNX10AF63G; we thank NASA for use of the NASA High Performance Computing Facilities.
The authors declare that they have no competing interests.
RL and MR were principal investigators of this research and drafted this manuscript. PL performed the simulations and analysis of the conical winds and axial jets. SD performed the simulations and analysis of the lopsided jets and disc outflows. All authors read and approved the final manuscript.
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Lovelace, R.V., Romanova, M.M., Lii, P. et al. On the origin of jets from disc-accreting magnetized stars. Comput. Astrophys. 1, 3 (2014). https://doi.org/10.1186/s40668-014-0003-5
- Toroidal Magnetic Field
- Tauri Star
- Magnetic Diffusivity
- Disc Wind
- Poloidal Magnetic Field | 0.847759 | 3.826932 |
A proof-of-concept demonstration by NASA to determine whether we could save Earth from a doomsday asteroid by literally knocking it off course may end up causing the first human-generated meteor shower.
Called the Double Asteroid Redirection Test (DART), the unprecedented mission will begin with the launch of an 1,100-pound NASA probe aboard a SpaceX Falcon 9 in 2021. It will then travel roughly 6.6 million miles for a dramatic rendezvous with a binary asteroid system called Didymos in late September 2022. Instead of targeting Didymos, which measures nearly 2,600 feet across, DART will set its sights instead on a smaller, 500-foot-wide orbiting object nicknamed "Didymoon." Traveling at a speed of 13,500 mph, DART's collision with Didymoon is expected to generate enough force to change the small rock's orbit.
"The collision will change the speed of the moonlet in its orbit around the main body by a fraction of one percent, but this will change the orbital period of the moonlet by several minutes — enough to be observed and measured using telescopes on Earth," NASA states on the mission website.
A new manmade meteoroid stream
When DART collides with Didymoon, the resulting explosion is expected to create a 30-foot-wide crater in the asteroid and, according to The New York Times, eject anywhere from 22,000 to 220,000 pounds of centimeter-sized debris. While the vast majority of these tiny meteoroids will envelope the Didymos system like a cloud, an unknown number will be ejected into space. Due to the asteroid's orbit passing by Earth only a few days after the collision, it's likely that some will burn up in the atmosphere as part of the first meteor shower caused by human activities in space.
According to Paul Wiegert, an astronomy professor at the University of Western Ontario, this precedent is as much a warning as an opportunity. In a new paper published in The Planetary Science Journal he writes that while the vast majority of the ejecta created by DART won't cross paths with Earth for potentially thousands of years, the experiment still proves that we need to be careful –– particularly in regards to spacecraft safety –– and understand the repercussions of violent actions in space.
"Though one is tempted to dismiss the problem as negligible at this time, it is reminiscent of the problem of space debris in low Earth orbit," he writes. "Neglected initially, we are now reaching a point where we may be denied the full use of valuable portions of near-Earth space because of orbital debris build-up. Much future expense and risk could be averted if the same story does not unfold with asteroidal debris production."
Wiegert adds in the paper that future instruments, such as the mirrors on the upcoming James Webb Space Telescope, could be critically damaged by artificially-generated meteoroid streams. He urges researchers to monitor not only the results of the collision, but also the path of the debris field. Setting such a precedent could help protect future missions from increased human activity elsewhere in our solar system.
"Though it is unlikely to occur in the case of the DART impact, future human asteroid operations such as planetary defense tests or asteroid mining, could conceivably produce debris streams whose meteoroid particle content rivals or exceeds naturally occurring meteoroid streams," he warns. | 0.885182 | 3.789047 |
Observations of light coming from a star zipping in orbit around the humongous black hole at the center of our galaxy have provided fresh evidence backing Albert Einstein’s 1915 theory of general relativity, astronomers said on Thursday.
Researchers studied a star called S0-2, boasting a mass roughly 10 times larger than the sun, as it travels in an elliptical orbit lasting 16 years around the supermassive black hole called Sagittarius A* residing at the center of the Milky Way 26,000 light years from Earth.
They found that the behavior of the star’s light as it escaped the extreme gravitational pull exerted by the black hole, with 4 million times the sun’s mass, conformed to Einstein’s theory’s predictions. The famed theoretical physicist proposed the theory, considered one of the pillars of science, to explain the laws of gravity and their relation to other natural forces.
While Einstein’s theory held up in the observations of this star, astronomer Andrea Ghez of the University of California, Los Angeles said it may not be able to fully account for what happens in the most exotic possible gravitational environments like those of black holes. These extraordinarily dense celestial entities exert gravitational fields so strong that no matter or light can escape.
The study detected a co-mingling of space and time near the black hole as predicted by Einstein’s theory. Isaac Newton’s 17th century law of universal gravitation could not account for these observations, Ghez said.
“Newton had the best description of gravity for a long time but it started to fray around the edges. And Einstein provided a more complete theory. Today we are seeing Einstein’s theories starting to fray around the edges,” said Ghez, who led the study published in the journal Science.
At some point a more comprehensive theory of gravity may be required, she said.
The study, relying heavily on data from the Keck Observatory in Hawaii, focused on an effect called gravitational redshift.
Einstein’s theory foresees the wavelength of electromagnetic radiation including light lengthening as it escapes the pull of gravity exerted by a massive celestial body like a black hole.
Photons – particles of light – expend energy to escape but always travel at the speed of light, meaning the energy loss occurs through a change of electromagnetic frequency rather than a slowing of velocity. This causes a shift to the red end of the electromagnetic spectrum, a gravitational redshift. | 0.865601 | 3.879808 |
Some Mars experts are eager and optimistic for a dust storm this year to grow so grand it darkens skies around the entire Red Planet.
This biggest type of phenomenon in the environment of modern Mars could be examined as never before possible, using the combination of spacecraft now at Mars.
A study published this week based on observations by NASA’s Mars Reconnaissance Orbiter (MRO) during the most recent Martian global dust storm — in 2007 — suggests such storms play a role in the ongoing process of gas escaping from the top of Mars’ atmosphere. That process long ago transformed wetter, warmer ancient Mars into today’s arid, frozen planet.
“We found there’s an increase in water vapor in the middle atmosphere in connection with dust storms,” said Nicholas Heavens of Hampton University, Hampton, Virginia, lead author of the report in Nature Astronomy. “Water vapor is carried up with the same air mass rising with the dust.”
A link between the presence of water vapor in Mars’ middle atmosphere — roughly 30 to 60 miles (50 to 100 kilometers) high — and escape of hydrogen from the top of the atmosphere has been detected by NASA’s Hubble Space Telescope and the European Space Agency’s Mars Express orbiter, but mainly in years without the dramatic changes produced in a global dust storm. NASA’s MAVEN mission arrived at Mars in 2014 to study the process of atmosphere escape.
“It would be great to have a global dust storm we could observe with all the assets now at Mars, and that could happen this year,” said David Kass of NASA’s Jet Propulsion Laboratory, Pasadena, California. He is a co-author of the new report and deputy principal investigator for the instrument that is the main source of data for it, MRO’s Mars Climate Sounder.
Continue reading here. | 0.834228 | 3.508693 |
Introduction & Background Material
- What is the difference between the solar system, galaxy, and universe?
- What is a light year (ly)?
- Define an astronomical unit (AU).
- Place in order of increasing size: parsec, AU, ly
- Did the solar system form as a direct result of the Big Bang?
- List the planets, in order, from closest to the Sun outward.
History of Astronomy
- What is retrograde motion? Why was it important?
- Detail the evolution from the geocentric to heliocentric model for our solar system.
- What contribution(s) did Ptolemy, Copernicus, Kepler and Newton make?
Navigating the Sky
- Discuss how to recognize the Big Dipper, and use it to find 2 other stellar objects.
- What makes Polaris special?
- What does Cassiopeia really look like?
- List the major stars in the Summer Triangle.
- Describe how to find the Andromeda Galaxy.
- What does Bootes look like? What is its major star?
The Sky, Star Motions, Coordinates, and Calendars
- Explain how constellations differ from asterisms.
- Define/explain: Celestial Sphere, NCP, SCP, celestial equator, ecliptic, equinoxes, solstices
- Be able to label all of the important points on the Celestial Sphere.
- What effect does Earth’s rotation have on the motion of stars in the sky?
- How does your location on Earth affect what you see in the sky?
- Define/explain: Arctic & Antarctic Circles, Tropics of Cancer & Capricorn
- Know where the Sun is (as seen from Earth) on solstices & equinoxes.
- What is precession? How has it affect our view of the sky?
Seasons and Phases of the Moon
- What causes seasons on the Earth? What common answer is incorrect?
- Give 2 reasons why are summers warmer than winters in the northern hemisphere.
- Know the order of the phases of the Moon; be able to draw them, give rise/set times.
- Explain the difference between synodic and sidereal periods of the Moon.
- List 2 conditions required for an eclipse.
- Define umbra and penumbra.
- Be able to discuss the three types of lunar eclipses in detail.
- Be able to discuss the three types of solar eclipses in detail.
- Why does the Moon appear red during a total lunar eclipse?
- Why are eclipses so rare?
- Why are solar eclipses so short compared to lunar eclipses?
- What is a nebula? A solar nebula?
- Why are the terrestrial (rocky) planets closer to the Sun?
- Be able to describe the time-line of planetary formation: planetesimals to planets.
- How did the way planets form affect things like the shape of orbits & the ecliptic?
- What are comets and asteroids?
- How do we know how old the solar system is?
- What is the Earth’s interior like? How do we know? Detail its layers/make up.
- What is Plate Tectonics? What evidence is there for it?
- How did Earth’s atmosphere originally form? How did it change over time? Why?
- List the various kinds of radiation in the EM spectrum.
- What kinds of radiation reach Earth’s surface?
- Why do aurora form?
- List major surface features on the Moon.
- What is regolith? How does it differ from soil?
- Describe the various formation theories for the Moon.
- What is synchronous rotation?
- Why do we have tides on the Earth? What is their impact?
- Define spring and neap tides.
- How does Mercury differ from the Moon?
- Name surface features on Mercury that were discussed in class.
- Why does Mercury have such a weak magnetic field?
- Why is Venus so hot?
- Compare the atmospheres, past and present, of Earth and Venus.
- Why are there so few craters on Venus?
- Why do we have so few pictures of the surface of Venus?
- What are the Martian “canals”?
- Discuss a few of the major surface features on Mars.
- Compare Mars’ atmosphere to that of Earth.
- Did Mars ever have flowing water? What evidence is there?
- What happened to the water on Mars?
- Does Mars have moons? If so, how many & describe their origin.
Jupiter & Saturn
- How big is Jupiter? What is it made of?
- What are belts and zones?
- What is the Great Red Spot, and why has it survived so long?
- Name all 4 Galilean moons and a few interesting facts about each.
- What forms the rings around Saturn?
- What other planets also have rings?
- Why is Saturn’s atmosphere less stormy than Jupiter’s?
- What is interesting about Saturn’s moon Titan?
Uranus, Neptune & Pluto
- What strange feature does Uranus have compared to the other planets?
- What gives Neptune its distinctive colour?
- Compare the outer planets to each other.
- What is unusual about Pluto? What is Charon?
Other Solar System objects
- How do asteroids, comets and meteors compare to each other? Differ?
- What is the difference between meteoroids, meteors, and meteorites?
- What are the 3 main parts of a comet?
- Why do comets have tails?
- What happened to the dinosaurs? | 0.910843 | 3.477968 |
A NASA spacecraft studying the sun has recorded amazing video of a giant plume of super-hot plasma erupting from the star's surface, only to crash back down hours later.
The solar plasma eruption, which NASA scientists nicknamed a "Dragon Tail," rose up from the sun's surface today (Jan. 31) and was spotted by the agency's Solar Dynamics Observatory, a powerful spacecraft that constantly records the sun's weather in different wavelengths of light.
A video of the Dragon Tail solar eruption shows a tendril of solar plasma, which scientists call a "filament," extending across the northeastern face of the sun over the course of four hours. Near the end of the event, the filament begins to break apart.
"Some of the plasma was released into space but not all could escape the gravitational pull of the sun," SDO mission officials explained in a video description. "It's not surprising that plasma should fall back to the sun. After all, the sun's gravity is powerful. "
Filaments are plasma formations on the sun sculpted by the star's intense magnetic field, with one end anchored to the sun's surface. The other end can extend through the sun's outer atmosphere, called the corona, hundreds of thousands of miles into space.
Filament structures typically last about a single day, though stable ones can exist for months at a time, SDO officials explained. The plasma in filaments consists of super-hot helium and hydrogen that is electrically charged, they added.
NASA's Solar Dynamics Observatory is one of several spacecraft constantly monitoring the sun for signs of solar flares, eruptions and other space weather events. The sun is currently in an active phase of its 11-year solar weather cycle and is expected to reach its peak activity period in 2013. The current sun weather cycle is known as Solar Cycle 24. | 0.83386 | 3.317175 |
Remember the spacecraft GALEX (which means Galaxy Evolution Explorer) that was sent to space with the mission of observing galaxies in ultraviolet light across 10 billion years of cosmic history through an incorporated telescope on April 28th of 2003? It’s now officially been traveling the space and sending information back to Earth for five years.
“GALEX’s ultraviolet observations are telling the scientists how galaxies, the building block of our Universe, evolve and change. GALEX observations are providing data for NASA’s investigators to find out when and how the stars that we see today were formed and which chemical elements are the galaxies made off.”
Now GALEX has already observed more than 100 million galaxies. The first comprehensive map of the Universe of galaxies is now ready for construction, helping us understand how galaxies like our own Milky Way were formed.
“In effect, GALEX acts like a time machine through which humans see the universe as it was a few billion years after its birth because it observes places so far away that the light reaching GALEX, even traveling at 299.792.458 meters per second is still the same as billions of years before.”
Read the full article | 0.847856 | 3.136786 |
Using data captured by ALMA in Chile and from the ROSINA instrument on ESA’s Rosetta mission , a team of astronomers has found faint traces of the chemical compound [Freon-40] – (CH3Cl), also known as methyl chloride and chloromethane, around both the infant star system IRAS 16293-2422 , about 400 light-years away, and the famous comet 67P/Churyumov-Gerasimenko (67P/C-G) in our own Solar System. The new ALMA observation is the first detection ever of a stable organohalogen in interstellar space .
Organohalogens consist of halogens, such as chlorine and fluorine, bonded with carbon and sometimes other elements. On Earth, these compounds are created by some biological processes — in organisms ranging from humans to fungi — as well as by industrial processes such as the production of dyes and medical drugs .
This new discovery of one of these compounds, Freon-40, in places that must predate the origin of life, can be seen as a disappointment, as earlier research had suggested that these molecules could indicate the presence of life.
“Finding the organohalogen Freon-40 near these young, Sun-like stars was surprising,” said Edith Fayolle, a researcher with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts in the USA, and lead author of the new paper. “We simply didn’t predict its formation and were surprised to find it in such significant concentrations. It’s clear now that these molecules form readily in stellar nurseries, providing insights into the chemical evolution of planetary systems, including our own.”
Exoplanet research has gone beyond the point of finding planets — more than 3000 exoplanets are now known — to looking for chemical markers that might indicate the potential presence of life. A vital step is determining which molecules could indicate life, but establishing reliable markers remains a tricky process.
“ALMA’s discovery of organohalogens in the interstellar medium also tells us something about the starting conditions for organic chemistry on planets. Such chemistry is an important step toward the origins of life,” adds Karin Öberg, a co-author on the study. “Based on our discovery, organohalogens are likely to be a constituent of the so-called ‘primordial soup’, both on the young Earth and on nascent rocky exoplanets.”
This suggests that astronomers may have had things around the wrong way; rather than indicating the presence of existing life, organohalogens may be an important element in the little-understood chemistry involved in the origin of life.
Co-author Jes Jørgensen from the Niels Bohr Institute at University of Copenhagen adds: “This result shows the power of ALMA to detect molecules of astrobiological interest toward young stars on scales where planets may be forming. Using ALMA we have previously found precursors to sugars and amino acids around different stars. The additional discovery of Freon-40 around Comet 67P/C-G strengthens the links between the pre-biological chemistry of distant protostars and our own Solar System.”
The astronomers also compared the relative amounts of Freon-40 that contain different isotopes of chlorine in the infant star system and the comet — and found similar abundances. This supports the idea that a young planetary system can inherit the chemical composition of its parent star-forming cloud and opens up the possibility that organohalogens could arrive on planets in young systems during planet formation or via comet impacts.
“Our results shows that we still have more to learn about the formation of organohalogens,” concludes Fayolle. “Additional searches for organohalogens around other protostars and comets need to be undertaken to help find the answer.” | 0.903853 | 4.069189 |
The notion of a static, unchanging climate is foreign to the history of the earth or any other planet with a fluid envelope. The fact that the developed world went into hysterics over changes in global mean temperature anomaly of a few tenths of a degree will astound future generations. Such hysteria simply represents the scientific illiteracy of much of the public, the susceptibility of the public to the substitution of repetition for truth, and the exploitation of these weaknesses by politicians, environmental promoters, and, after 20 years of media drum beating, many others as well. Climate is always changing. We have had ice ages and warmer periods when alligators were found in Spitzbergen. Ice ages have occurred in a hundred thousand year cycle for the last 700 thousand years, and there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now. More recently, we have had the medieval warm period and the little ice age. During the latter, alpine glaciers advanced to the chagrin of overrun villages. Since the beginning of the 19th Century these glaciers have been retreating. Frankly, we don’t fully understand either the advance or the retreat.
For small changes in climate associated with tenths of a degree, there is no need for any external cause. The earth is never exactly in equilibrium. The motions of the massive oceans where heat is moved between deep layers and the surface provides variability on time scales from years to centuries. Recent work (Tsonis et al, 2007), suggests that this variability is enough to account for all climate change since the 19th Century.
For warming since 1979, there is a further problem. The dominant role of cumulus convection in the tropics requires that temperature approximately follow what is called a moist adiabatic profile. This requires that warming in the tropical upper troposphere be 2-3 times greater than at the surface. Indeed, all models do show this, but the data doesn’t and this means that something is wrong with the data. It is well known that above about 2 km altitude, the tropical temperatures are pretty homogeneous in the horizontal so that sampling is not a problem. Below two km (roughly the height of what is referred to as the trade wind inversion), there is much more horizontal variability, and, therefore, there is a profound sampling problem. Under the circumstances, it is reasonable to conclude that the problem resides in the surface data, and that the actual trend at the surface is about 60% too large. Even the claimed trend is larger than what models would have projected but for the inclusion of an arbitrary fudge factor due to aerosol cooling. The discrepancy was reported by Lindzen (2007) and by Douglass et al (2007). Inevitably in climate science, when data conflicts with models, a small coterie of scientists can be counted upon to modify the data. Thus, Santer, et al (2008), argue that stretching uncertainties in observations and models might marginally eliminate the inconsistency. That the data should always need correcting to agree with models is totally implausible and indicative of a certain corruption within the climate science community.
It turns out that there is a much more fundamental and unambiguous check of the role of feedbacks in enhancing greenhouse warming that also shows that all models are greatly exaggerating climate sensitivity. Here, it must be noted that the greenhouse effect operates by inhibiting the cooling of the climate by reducing net outgoing radiation. However, the contribution of increasing CO2 alone does not, in fact, lead to much warming (approximately 1 deg. C for each doubling of CO2). The larger predictions from climate models are due to the fact that, within these models, the more important greenhouse substances, water vapour and clouds, act to greatly amplify whatever CO2 does. This is referred to as a positive feedback. It means that increases in surface temperature are accompanied by reductions in the net outgoing radiation – thus enhancing the greenhouse warming. All climate models show such changes when forced by observed surface temperatures. Satellite observations of the earth’s radiation budget allow us to determine whether such a reduction does, in fact, accompany increases in surface temperature in nature. As it turns out, the satellite data from the ERBE instrument (Barkstrom, 1984, Wong et al, 2006) shows that the feedback in nature is strongly negative — strongly reducing the direct effect of CO2 (Lindzen and Choi, 2009) in profound contrast to the model behaviour. This analysis makes clear that even when all models agree, they can all be wrong, and that this is the situation for the all important question of climate sensitivity. Unfortunately, Lindzen and Choi (2009) contained a number of errors; however, as shown in a paper currently under review, these errors were not relevant to the main conclusion.
According to the UN’s Intergovernmental Panel on Climate Change, the greenhouse forcing from man made greenhouse gases is already about 86% of what one expects from a doubling of CO2 (with about half coming from methane, nitrous oxide, freons and ozone), and alarming predictions depend on models for which the sensitivity to a doubling for CO2 is greater than 2C which implies that we should already have seen much more warming than we have seen thus far, even if all the warming we have seen so far were due to man. This contradiction is rendered more acute by the fact that there has been no statistically significant net global warming for the last fourteen years. Modellers defend this situation, as we have already noted, by arguing that aerosols have cancelled much of the warming (viz Schwartz et al, 2010), and that models adequately account for natural unforced internal variability. However, a recent paper (Ramanathan, 2007) points out that aerosols can warm as well as cool, while scientists at the UK’s Hadley Centre for Climate Research recently noted that their model did not appropriately deal with natural internal variability thus demolishing the basis for the IPCC’s iconic attribution (Smith et al, 2007). Interestingly (though not unexpectedly), the British paper did not stress this. Rather, they speculated that natural internal variability might step aside in 2009, allowing warming to resume. Resume? Thus, the fact that warming has ceased for the past fourteen years is acknowledged. It should be noted that, more recently, German modellers have moved the date for ‘resumption’ up to 2015 (Keenlyside et al, 2008).
Climate alarmists respond that some of the hottest years on record have occurred during the past decade. Given that we are in a relatively warm period, this is not surprising, but it says nothing about trends.
Given that the evidence (and I have noted only a few of many pieces of evidence) strongly implies that anthropogenic warming has been greatly exaggerated, the basis for alarm due to such warming is similarly diminished. However, a really important point is that the case for alarm would still be weak even if anthropogenic global warming were significant. Polar bears, arctic summer sea ice, regional droughts and floods, coral bleaching, hurricanes, alpine glaciers, malaria, etc. etc. all depend not on some global average of surface temperature anomaly, but on a huge number of regional variables including temperature, humidity, cloud cover, precipitation, and direction and magnitude of wind. The state of the ocean is also often crucial. Our ability to forecast any of these over periods beyond a few days is minimal (a leading modeler refers to it as essentially guesswork). Yet, each catastrophic forecast depends on each of these being in a specific range. The odds of any specific catastrophe actually occurring are almost zero. This was equally true for earlier forecasts of famine for the 1980’s, global cooling in the 1970’s, Y2K and many others. Regionally, year to year fluctuations in temperature are over four times larger than fluctuations in the global mean. Much of this variation has to be independent of the global mean; otherwise the global mean would vary much more. This is simply to note that factors other than global warming are more important to any specific situation. This is not to say that disasters will not occur; they always have occurred and this will not change in the future. Fighting global warming with symbolic gestures will certainly not change this. However, history tells us that greater wealth and development can profoundly increase our resilience.
In view of the above, one may reasonably ask why there is the current alarm, and, in particular, why the astounding upsurge in alarmism of the past 4 years. When an issue like global warming is around for over twenty years, numerous agendas are developed to exploit the issue. The interests of the environmental movement in acquiring more power, influence, and donations are reasonably clear. So too are the interests of bureaucrats for whom control of CO2 is a dream-come-true. After all, CO2 is a product of breathing itself. Politicians can see the possibility of taxation that will be cheerfully accepted because it is necessary for ‘saving’ the earth. Nations have seen how to exploit this issue in order to gain competitive advantages. But, by now, things have gone much further. The case of ENRON (a now bankrupt Texas energy firm) is illustrative in this respect. Before disintegrating in a pyrotechnic display of unscrupulous manipulation, ENRON had been one of the most intense lobbyists for Kyoto. It had hoped to become a trading firm dealing in carbon emission rights. This was no small hope. These rights are likely to amount to over a trillion dollars, and the commissions will run into many billions. Hedge funds are actively examining the possibilities; so was the late Lehman Brothers. Goldman Sachs has lobbied extensively for the ‘cap and trade’ bill, and is well positioned to make billions. It is probably no accident that
Gore, himself, is associated with such activities. The sale of indulgences is already in full swing with organizations selling offsets to one’s carbon footprint while sometimes acknowledging that the offsets are irrelevant. The possibilities for corruption are immense. Archer Daniels Midland (America’s largest agribusiness) has successfully lobbied for ethanol requirements for gasoline, and the resulting demand for ethanol may already be contributing to large increases in corn prices and associated hardship in the developing world (not to mention poorer car performance). And finally, there are the numerous well meaning individuals who have allowed propagandists to convince them that in accepting the alarmist view of anthropogenic climate change, they are displaying intelligence and virtue For them, their psychic welfare is at stake.
With all this at stake, one can readily suspect that there might be a sense of urgency provoked by the possibility that warming may have ceased and that the case for such warming as was seen being due in significant measure to man, disintegrating. For those committed to the more venal agendas, the need to act soon, before the public appreciates the situation, is real indeed. However, for more serious leaders, the need to courageously resist hysteria is clear. Wasting resources on symbolically fighting ever present climate change is no substitute for prudence. Nor is the assumption that the earth’s climate reached a point of perfection in the middle of the twentieth century a sign of intelligence.
Professor Richard S Lindzen has responded to the invitation to supply a paper for this site with the above.
He asks us to remember that this is only one of a number of papers that are currently being revised to allow for new advances and new data.
He is well qualified to have a considered opinion.
Alfred P. Sloan Professor of Meteorology, Department of Earth, Atmospheric and Planetary Sciences, MIT
Professor Lindzen is a dynamical meteorologist with interests in the broad topics of climate, planetary waves, monsoon meteorology, planetary atmospheres, and hydrodynamic instability. His research involves studies of the role of the tropics in mid-latitude weather and global heat transport, the moisture budget and its role in global change, the origins of ice ages, seasonal effects in atmospheric transport, stratospheric waves, and the observational determination of climate sensitivity. He has made major contributions to the development of the current theory for the Hadley Circulation, which dominates the atmospheric transport of heat and momentum from the tropics to higher latitudes, and has advanced the understanding of the role of small scale gravity waves in producing the reversal of global temperature gradients at the mesopause, and provided accepted explanations for atmospheric tides and the quasi-biennial oscillation of the tropical stratosphere. He pioneered the study of how ozone photochemistry, radiative transfer and dynamics interact with each other. He is currently studying what determines the pole to equator temperature difference, the nonlinear equilibration of baroclinic instability and the contribution of such instabilities to global heat transport. He has also been developing a new approach to air-sea interaction in the tropics, and is actively involved in parameterizing the role of cumulus convection in heating and drying the atmosphere and in generating upper level cirrus clouds. He has developed models for the Earth’s climate with specific concern for the stability of the ice caps, the sensitivity to increases in CO2, the origin of the 100,000 year cycle in glaciation, and the maintenance of regional variations in climate. Prof. Lindzen is a recipient of the AMS’s Meisinger, and Charney Awards, the AGU’s Macelwane Medal, and the Leo Huss Walin Prize. He is a member of the National Academy of Sciences, and the Norwegian Academy of Sciences and Letters, and a fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Sciences, the American Geophysical Union and the American Meteorological Society. He is a corresponding member of the NAS Committee on Human Rights, and has been a member of the NRC Board on Atmospheric Sciences and Climate and the Council of the AMS. He has also been a consultant to the Global Modeling and Simulation Group at NASA’s Goddard Space Flight Center, and a Distinguished Visiting Scientist at California Institute of Technology’s Jet Propulsion Laboratory. (Ph.D., ’64, S.M., ’61, A.B., ’60, Harvard University)
Barkstrom, B.R., 1984: The Earth Radiation Budget Experiment (ERBE), Bull. Amer. Meteor. Soc., 65, 1170–1185.
Douglass,D.H., J.R. Christy, B.D. Pearsona and S. F. Singer, 2007: A comparison of tropical temperature trends with model predictions, Int. J. Climatol., DOI: 10.1002/joc.1651
Keenlyside, N.S., M. Lateef, et al, 2008: Advancing decadal-scale climate prediction in the North Atlantic sector, Nature, 453, 84-88.
Lindzen, R.S. and Y.-S. Choi, 2009: On the determination of climate feedbacks from ERBE data, accepted Geophys. Res. Ltrs.
Lindzen, R.S., 2007: Taking greenhouse warming seriously. Energy & Environment, 18, 937-950.
Ramanathan, V., M.V. Ramana, et al, 2007: Warming trends in Asia amplified by brown cloud solar absorption, Nature, 448, 575-578.
Santer, B. D., P. W. Thorne, L. Haimberger, K. E. Taylor, T. M. L. Wigley, J. R. Lanzante, S. Solomon, M. Free, P. J. Gleckler, P. D. Jones, T. R. Karl, S. A. Klein, C. Mears, D. Nychka, G. A. Schmidt, S. C. Sherwood, and F. J. Wentz, 2008: Consistency of modelled and observed temperature trends in the tropical troposphere, Intl. J. of Climatology, 28, 1703-1722.
Schwartz, S.E., R.J. Charlson, R.A. Kahn, J.A. Ogren, and H. Rodhe, 2010: Why hasn’t the Earth warmed as much as expected?, J. Climate, 23, 2453-2464.
Smith, D.M., S. Cusack, A.W. Colman, C.K. Folland, G.R. Harris, J.M. Murphy, 2007: Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model, Science, 317, 796-799.
Tsonis, A. A., K. Swanson, and S. Kravtsov, 2007: A new dynamical mechanism for major climate shifts, Geophys. Res. Ltrs., 34, L13705, doi:10.1029/2007GL030288
Wong, T., B. A. Wielicki, et al., 2006: Reexamination of the observed decadal variability of the earth radiation budget using altitude-corrected ERBE/ERBS nonscanner WFOV Data, J. Climate, 19, 4028–4040. | 0.805874 | 3.23538 |
|Home > Public Information > Scientific Highlights > 2001|
discoveries following from observations
GALAXY | EXTRAGALACTIC
DISCOVERY OF THE FIRST BLACK HOLE IN THE HALO OF OUR GALAXY
X-ray novae or soft
X-ray transients constitute a subset of low-mass
X-ray binaries (LMXBs) that consist
of a late-type secondary star and a neutron
star or black hole exhibiting bright optical
and X-ray outbursts that are recurrent on time
scales of decades. During their
outbursts, they resemble persistent LMXBs
in which the light of the secondary
star is overwhelmed by a luminous accretion
disk surrounding the compact object. After a
year or less in some objects, the system
returns to quiescence. The secondary star now
contributes a much larger fraction of
the total light, and its atmospheric absorption
lines become visible in optical spectra.
Thus, quiescent X-ray novae provide the ideal
opportunity to study the nature and dynamical
properties of the binary system. These
studies have demonstrated so far that the mass of
the compact object in 10 X-ray
novae exceeds the theoretical maximum
mass of a neutron star and thus
must evidently be a black hole.
A previously unknown
X-ray transient, XTE J1118+480, was
discovered by the Rossi X-Ray Timing Explorer all-sky
monitor on 2000 March 29. An optical counterpart
was then identified and confirmed spectroscopically. The shape of the light curve
and its temporal evolution resembled those of
superhumps observed during superoutbursts of
short-period cataclysmic variables and outbursts of
some other soft X-ray transients. The binary system
was found at a distance of about 6,000 light years in a direction pointing
62 degrees away from the Galactic plane.
From spectroscopic observations
carried out by an international team of astronomers using a
number of telescopes, including the WHT, and spanning a couple of months,
the mass of the compact object was determined to be at least 6 times
the mass of the Sun. This lower limit to its mass firmly implies that
it is a black hole, the first one firmly identified in the Galactic halo.
UZ For is a member of the
AM Herculis type cataclysmic variables (CVs), in which a strongly magnetic
white dwarf accretes material from a late-type companion that fills its
Roche lobe. As material passes through the inner Lagrange point of
the system towards the white dwarf, the magnetic field does not initially
dominate the motion of the material. Closer to the white dwarf surface,
beyond the stagnation region, the field threads and disrupts the flow,
channelling infalling material into a funnel which terminates in a shock
front at or near the magnetic pole(s). Shock-heated plasma cools via
bremsstrahlung, Compton cooling, and cyclotron emission as it settles
onto the white dwarf, with the accretion stream also contributing to
the optical and ultraviolet emission. Magnetic interaction between the
white dwarf and its companion keeps the white dwarf in rotational synchronism
with the M dwarf companion, and the system rotation then leads to the
coherent variability observed in these systems.
The orbital period of UZ
For is 126.5 min, of which the white dwarf is eclipsed for approximately
8 min. The simultaneous rapid intensity and spectral variations
which are characteristic of the eclipses of cataclysmic variables make
these objects ideal targets for study with advanced photon-counting
detectors which record the time of arrival and the energy of each incident
photon. Although such detectors have long been available for high-energy
studies (e.g. proportional counters or CCD detectors operated in X-ray
photon-counting mode), they are only now becoming available for optical
work, based on the new development of superconducting tunnel junction
A photon incident
on an individual STJ breaks a number of the Cooper pairs responsible
for the superconducting state. Since the energy gap between the ground
state and excited state is only a few meV, each individual photon
creates a large number of free electrons, in proportion to the photon
energy. The amount of charge thus produced is detected and measured,
giving an accurate estimate of the photon arrival time as well as a direct
measurement of its energy. Arrays of such devices provide imaging capabilities.
A 6×6 array of 25×25
μm2 tantalum STJ device built at ESA was incorporated
into a cryogenic camera operated at the Nasmyth focus of the 4.2-m
William Herschel Telescope. The projected pixel size of 0.6×0.6 arcsec2 results in an array covering a sky area of
4×4 arcsec2. This camera, 'S-Cam2', is
a development of the system first applied to observations of the Crab
pulsar in 1999. Several modifications, including a new detector array,
and improved detector stability and uniformity, result in an improved
wavelength resolution of Δλ=30, 60, and 100 nm at λ=350, 500, and 650
For each individual detected
photon, the arrival time, x, y array element (or
pixel) , co-ordinateand energy channel are recorded. Photon arrival times
are recorded with an accuracy of about ±5 μs with respect to
GPS timing signals, which is specified to remain within 1 μs of UTC.
The characteristics of
STJ arrays are ideally suited to the observation of CVs. The high time
resolution, high efficiency, large dynamic range, and modest energy resolution
afforded by the S-Cam2 system allow a direct probing of the energy dependence
of the intensity variations across the eclipse, and investigation of the
details of the ingress and egress light curves, whose structure provides
important diagnostics of the emission mechanism.
Astronomers obtained data
for three eclipses of UZ For. They attributed two sharp changes in brightness
to the eclipse of two small accretion regions and localize them on the
surface of the white dwarf primary. The first of these is in the lower
hemisphere at the location seen by others in the optical, and in the EUV
and X-rays. The second is in the upper hemisphere, near the rotation axis,
and there is no evidence for any emission from this region in X-rays. The
diameter of the accretion spots is less than about 100 km.
The central velocity
dispersions of many Local Group dwarf spheroidal (dSph) galaxies are significantly
larger than expected for self-gravitating systems. Assuming virial equilibrium,
the implied mass-to-light (M/L) ratios reach as high
250, making the dSph galaxies among the most dark matter- dominated
systems in the universe. Given the apparent absence of dark matter in globular
clusters, dSph galaxies are also the smallest dark matter- dominated stellar
systems in the universe. As such, they have emerged as crucial testing
grounds for competing theories of dark matter.
Despite their importance,dynamical
models of dSph galaxies to date have been very simple. Most
analyses have relied on the use of single-mass
isotropic King models, with their associated
assumptions that mass follows light and that
the stellar velocity distribution is isotropic.
Hitherto, the validity of such assumptions
has remained unchallenged because of the
small size of the data sets. When only
small numbers of radial velocities are available,
there is a well-known degeneracy between mass
and velocity anisotropy. An increase in the
line-of-sight velocity dispersion at large
radii may by due to either (1) the
presence of large amounts of mass at
large radii or (2) tangential anisotropy
in the velocity distribution. This degeneracy
could be broken by means of improved modelling and a larger data set
with many more stars in the outer parts.
Observations were conducted
from 2000 June 23 to 26 at the William Herschel Telescope using the AF2/WYFFOS
multifiber positioner and spectrograph. A total of 284 stars were observed,
spanning the magnitude range of V
17.0-19.8. Of these, 159 were Draco members (extending to 25')
with spectra of sufficient quality to be included in the dynamical analyses.
The median velocity uncertainty for these 159 stars was 1.9 km s-1.
These are the first observations to probe the outermost regions of a strongly
dark matter-dominated dSph galaxy.
From subsequent analysis,
astronomers found that the velocity dispersion profile is flat or slowly
rising at large radii, which provides the first c lear signature of an
extended dark matter halo in any dSph galaxy.
Further studies of this
cocoon, whose composition remains a mystery, promise to illuminate the
early history of our own Galaxy, which presumably built up from such
dark-matter quanta. This result also fits with the bottom-up view of
galaxy formation, in which the gravitational fields of big galaxies
shred smaller ones and assimilate their stars, gas, and dark matter.
The Wide Angle Survey,
one of the ING Wide Field Survey programmes, brings together a
diverse range of scientific topics, merging the observational programme
to increase scientific effectiveness.
As part of the Virgo
survey component some 25 square degrees of Virgo were obtained in the
B photometric band, and the pipeline processed object catalogues were
analysed. More than 500 Low Surface Brightness galaxies Btot<21 were discovered
by comparing the light profiles of the millions of objects in the
data frames with those of previously known template LSB galaxies.
Using this data astronomers
at Cambridge discovered a new nearby dwarf galaxy in the constellation of Cepheus. This LSB dwarf galaxy is a typical
example of previously unknown nearby galaxies, and it had been previously
overlooked because of its low surface brightness relative to the night
function in Virgo, when combined with the much flatter function found
in the field, will enable the efficiency of low mass galaxy formation
in differing environments to be investigated. First results are indicating
a strong environmental dependence, which would need to be taken
into consideration by Cold Dark Matter theories.
A GIANT STREAM OF METAL-RICH STARS IN THE HALO OF THE GALAXY M31
framework of hierarchical structure formation, large spiral galaxies
like the Milky Way or Andromeda arose from the merger of many small
galaxies and protogalaxies. Later in their evolution, spiral galaxies
become the dominant component in such mergers, cannibalizing smaller
systems that fall within their sphere of influence. The complete destruction
of the victim is usually progressive, and may take several orbits.
However, the stellar debris from the destroyed dwarf galaxy follows
a similar orbital trajectory to the progenitor, which is likely to
have started life far away from the place of its final demise, and
so the tidally disrupted matter tends to be deposited over a broad range
in distance from the larger galaxy. Over time, with the accumulation
of many such mergers, large galaxies develop an extensive stellar and
dark-matter 'halo', the latter being by far the most massive component
of the galaxy. Meanwhile, part of the (dissipative) gas component of
the smaller galaxies feeds the growth of the disk of the larger galaxy.
This is seen in numerical simulations of galaxy formation, which result
in galactic haloes comprising clumps of dark matter. If this prediction
is correct, then haloes should possess significant substructure—in contrast
to previous suggestions, which predict the dark and luminous components
of haloes to be distributed smoothly.
Andromeda or M31 galaxy
is our Galaxy's "big sister", twice as large but otherwise very similar.
It is the nearest large galaxy, lying only 2.2 million light-years away.
Astronomers have known for some years that our own Galaxy is a cannibal.
Its outer parts are threaded with tell-tale streams of stars from small
galaxies it has engulfed.
The first sensitive panoramic
wide field imaging
survey of M31 using the Wide Field Camera on the Isaac Newton Telescope
has unambiguously revealed the presence of a giant stellar stream
within M31's halo. The source of the stream is likely to be either,
or both, of the peculiar dwarf galaxies M32 and NGC205, close companions
of M31, which may have lost a substantial amount of stars, gas and dust
due to their tidal interactions with the massive host galaxy. The broad
agreement of the metallicity distribution of the stream stars with
these two dwarf satellites together with their alignment, physical
proximity, and distorted morphological appearance, point to a common
origin. The well-known disparity in properties between the Milky
Way and M31 stellar haloes would be understandable if the majority
of M31's stellar halo arose as relatively recent tidal debris from prolonged
bouts of aggressive tidal interaction with its two nearest neighbour
satellites. Together with recent observations of tidal debris in
the Milky Way halo, these results clearly demonstrate that the epoch
of galaxy building still continues, and that substructure in the form
of huge, recently-deposited tidal streams, could be a generic feature
of large galaxy haloes.
The new survey was possible only because the digital detector arrays such as the Wide Field Camera now cover fairly large areas of sky. Even so, more than fifty long exposures had to be pieced together to give a panorama of the halo on one side of Andromeda.
COMPLETELY DARK GALAXIES
The universe could be harbouring numerous galaxies that have no stars at all and are made entirely of dark matter. Astronomers may ultimately discover that completely dark galaxies outnumber the familiar kind populated by shining stars and gas, perhaps by as many as 100 to 1. There is already a considerable amount of evidence that bright galaxies contain large amounts of dark matter, often ten times more than the mass of all their stars put together. There must be extra mass that we do not see to account for the observed movements of the stars under the influence of the gravity of the whole galaxy. In some galaxies we see so few stars they are incapable of holding themselves together as a galaxy. They would have long since scattered through space without the gravity of unseen matter to keep them together. But the question is: How do we look for these largely or even completely dark galaxies?
It's a difficult challenge, and the best technique will depend on the nature of the dark matter, which is still unknown. If the dark matter is composed entirely of fundamental particles, dark galaxies may act as gravitational lenses, distorting the appearance of; distant galaxies that happen to lie behind them. If the dark matter includes some brown dwarfs their infrared radiation may be detectable. The same will be true if the galaxies contain any dead stars, such as white dwarfs or black holes. If they are nearby, it might be possible to detect these stellar remnants acting as gravitational lenses on the light of individual stars in other galaxies beyond them. Several lensing events in a small area of sky would suggest the presence of a dark galaxy.
On place where a dark galaxy may exist has been identified using images taken with the INT Wide Field Camera. A galaxy called UGC 10214 has a stream of material flowing out of it, as if it is interacting with another galaxy. But in this case, there is no other galaxy or source of visible light present, hence the companion galaxy may be completely dark.
of standard cosmology is that dwarf protogalaxies
are the first to born as individual systems
in the universe. Afterward, many
of these merge to form larger galaxies such
as the Milky Way. The
way in which this process takes place
has consequences for the present-day structure
of the Milky Way. The significant issues are
how the merging efficiency compares with
the star formation efficiency in the protogalactic
fragments and how the fragment merging
and disruption compare with the age
of the Milky Way. If fragments are able
to form stars before merging, they will
collapse nondissipatively. If disruption
was not complete, Galactic precursors should
be visible today as dwarf galaxy satellites
or as stellar streams within the Galactic
The Sagittarius dwarf
galaxy, the closest Milky Way satellite
in an advanced state of tidal disruption,
provides a "living" test for tidal interaction
models and for galaxy formation theories. It was
soon apparent that its extent was larger than
at first assumed, and dynamical models
predict that the stream associated with the
galaxy should envelop the whole Milky Way in
an almost polar orbit.
Using the Wide Field
Camera on the Isaac Newton Telescope, astronomers detected a
very low density stellar system at 50 ±
10 kpc from the Galactic centre that could
be related to a merger process.
The found system is 60°
north and 46±12 kpc away from the centre
of the Sagittarius dwarf galaxy. If it
is really associated with this galaxy, it would
confirm predictions of dynamical interaction models indicating
that tidal debris from Sagittarius
could extend along a stream completely enveloping the
Milky Way in a polar orbit. However, the possibility that
it corresponds to a hitherto unknown
galaxy, also probably tidally stripped, cannot
DISTANT GALAXIES ARE IN THE RED
The panoramic IR camera, CIRSI has been used to carry out a large-scale survey of distant galaxies in the prime focus of the INT. The main goal of the project was to study the Universe when it was 7 billion years old, or around half its current age.
The recently completed infrared sky survey has detected over 50,000 galaxies in a patch of sky covering roughly the area of a full Moon. Although only one fifth of the data has been analysed so far, already three times as many very red galaxies have been found as was expected.
One possibility is that these galaxies have more old stars in them than expected. Old stars tend to be large and relatively cool -hence the red colour. A second possibility is that the galaxies are very dusty, where scattering by dust particles causes objects to appear red.
A second significant result is the discovery that these red galaxies seem to clump together much more than galaxies in the nearby Universe. One possible explanation is that these red galaxies are merging with each other to form single more massive galaxies.
This merging process would explain why the astronomers are seeing more galaxies in the past than expected. If galaxies merge, their total number will decrease to the present-day value.
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Satellite image of California’s San Andreas fault, where two continental plates come together. NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
By Dr. Phil Heron / 07.04.2016
Postdoctoral Fellow in Geodynamics
University of Toronto
Fifty years ago, there was a seismic shift away from the longstanding belief that Earth’s continents were permanently stationary.
In 1966, J. Tuzo Wilson published Did the Atlantic Close and then Re-Open? in the journal Nature. The Canadian author introduced to the mainstream the idea that continents and oceans are in continuous motion over our planet’s surface. Known as plate tectonics, the theory describes the large-scale motion of the outer layer of the Earth. It explains tectonic activity (things like earthquakes and the building of mountain ranges) at the edges of continental landmasses (for instance, the San Andreas Fault in California and the Andes in South America).
At 50 years old, with a surge of interest in where the surface of our planet has been and where it’s going, scientists are reassessing what plate tectonics does a good job of explaining – and puzzling over where new findings might fit in.
Evidence for the theory
Although the widespread acceptance of the theory of plate tectonics is younger than Barack Obama, German scientist Alfred Wegener first advanced the hypothesis back in 1912.
He noted that the Earth’s current landmasses could fit together like a jigsaw puzzle. After analyzing fossil records that showed similar species once lived in now geographically remote locations, meteorologist Wegener proposed that the continents had once been fused. But without a mechanism to explain how the continents could actually “drift,” most geologists dismissed his ideas. His “amateur” status, combined with anti-German sentiment in the period after World War I, meant his hypothesis was deemed speculative at best.
In 1966, Tuzo Wilson built on earlier ideas to provide a missing link: the Atlantic ocean had opened and closed at least once before. By studying rock types, he found that parts of New England and Canada were of European origin, and that parts of Norway and Scotland were American. From this evidence, Wilson showed that the Atlantic Ocean had opened, closed and re-opened again, taking parts of its neighboring landmasses with it.
And there it was: proof our planet’s continents were not stationary.
How plate tectonics works
Earth’s crust and top part of the mantle (the next layer in toward the core of our planet) run about 150 km deep. Together, they’re called the lithosphere and make up the “plates” in plate tectonics. We now know there are 15 major plates that cover the planet’s surface, moving at around the speed at which our fingernails grow.
Based on radiometric dating of rocks, we know that no ocean is more than 200 million years old, though our continents are much older. The oceans’ opening and closing process – called the Wilson cycle – explains how the Earth’s surface evolves.
A continent breaks up due to changes in the way molten rock in the Earth’s interior is flowing. That in turn acts on the lithosphere, changing the direction plates move. This is how, for instance, South America broke away from Africa. The next step is continental drift, sea-floor spreading, ocean formation – and hello, Atlantic Ocean. In fact, the Atlantic is still opening, generating new plate material in the middle of the ocean and making the flight from New York to London a few inches longer each year.
Oceans close when their tectonic plate sinks beneath another, a process geologists call subduction. Off the Pacific Northwest coast of the United States, the ocean is slipping under the continent and into the mantle below the lithosphere, creating in slow motion Mount St Helens and the Cascade mountain range.
In addition to undergoing spreading (construction) and subduction (destruction), plates can simply rub up against each other – usually generating large earthquakes. These interactions, also discovered by Tuzo Wilson back in the 1960s, are termed “conservative.” All three processes occur at the edges of plate boundaries.
But the conventional theory of plate tectonics stumbles when it tries to explain some things. For example, what produces mountain ranges and earthquakes that occur within continental interiors, far from plate boundaries?
Gone but not forgotten
The answer may lie in a map of ancient continental collisions my colleagues and I assembled.
Over the past 20 years, improved computer power and mathematical techniques have allowed researchers to more clearly look below the Earth’s crust and explore the deeper parts of our plates. Globally, we find many instances of scarring left over from the ancient collisions of continents that formed our present-day continental interiors.
A map of ancient continental collisions may represent regions of hidden tectonic activity. These old impressions below the Earth’s crust may still govern surface processes – despite being so far beneath the surface. If these deep scarred structures (more than 30 km down) were reactivated, they would cause devastating new tectonic activity.
It looks like previous plate boundaries (of which there are many) may never really disappear. These inherited structures contribute to geological evolution, and may be why we see geological activity within current continental interiors.
Mysterious blobs 2,900 km down
Modern geophysical imaging also shows two chemical “blobs” at the boundary of Earth’s core and mantle – thought to possibly stem from our planet’s formation.
These hot, dense piles of material lie beneath Africa and the Pacific. Located more than 2,900 km below the Earth’s surface, they’re difficult to study. And nobody knows where they came from or what they do. When these blobs of anomalous substance interact with cold ocean floor that has subducted from the surface down to the deep mantle, they generate hot plumes of mantle and blob material that cause super-volcanoes at the surface.
Does this mean plate tectonic processes control how these piles behave? Or is it that the deep blobs of the unknown are actually controlling what we see at the surface, by releasing hot material to break apart continents?
Answers to these questions have the potential to shake the very foundations of plate tectonics.
Plate tectonics in other times and places
And the biggest question of all remains unsolved: How did plate tectonics even begin?
The early Earth’s interior had significantly hotter temperatures – and therefore different physical properties – than current conditions. Plate tectonics then may not be the same as what our conventional theory dictates today. What we understand of today’s Earth may have little bearing on its earliest beginnings; we might as well be thinking about an entirely different world.
In the coming years, we may be able to apply what we discover about how plate tectonics got started here to actual other worlds – the billions of exoplanets found in the habitable zone of our universe.
So far, amazingly, Earth is the only planet we know of that has plate tectonics. In our solar system, for example, Venus is often considered Earth’s twin – just with a hellish climate and complete lack of plate tectonics.
Incredibly, the ability of a planet to generate complex life is inextricably linked to plate tectonics. A gridlocked planetary surface has helped produce Venus’ inhabitable toxic atmosphere of 96 percent CO₂. On Earth, subduction helps push carbon down into the planet’s interior and out of the atmosphere.
It’s still difficult to explain how complex life exploded all over our world 500 million years ago, but the processes of removing carbon dioxide from the atmosphere is further helped by continental coverage. An exceptionally slow process starts with carbon dioxide mixing with rain water to wear down continental rocks. This combination can form carbon-rich limestone that subsequently washes away to the ocean floor. The long removal processes (even for geologic time) eventually could create a more breathable atmosphere. It just took 3 billion years of plate tectonic processes to get the right carbon balance for life on Earth.
A theory works now, but what’s in the future?
Fifty years on from Wilson’s 1966 paper, geophysicists have progressed from believing continents never moved to thinking that every movement may leave a lasting memory on our Earth.
Life here would be vastly different if plate tectonics changed its style – as we know it can. A changing mantle temperature may affect the interaction of our lithosphere with the rest of the interior, stopping plate tectonics. Or those continent-sized chemical blobs could move from their relatively stable state, causing super-volcanoes as they release material from their deep reservoirs.
It’s hard to understand what our future holds if we don’t understand our beginning. By discovering the secrets of our past, we may be able to predict the motion of our plate tectonic future. | 0.847379 | 3.113136 |
The purpose of this paper is to present experimental results on the performance and operating life of a kW plasma jet rocket engine for space propulsion. The arc- jet thrustor represents an engine for potential space applications rocket, which may have a potential specific impulse in excess of seconds. Then go and clear out arc jet systems and go help Danse clear the day of the month, you can pile a bunch of ghouls in it, calibrate the rocket.
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The first ground experimental nuclear rocket engine XE assembly is shown here in “cold flow” configuration, as it makes a late evening arrival at Engine Test Stand No. The solar energy required is 0.
The Hydrogen – Boron reaction is sometimes termed “thermonuclear fission ” as opposed to the more common “thermonuclear fusion”.
Somehow the exhaust needs to have sufficient momentum for the opposite reaction to give the ship a good acceleration. Microscopic amounts of antimatter are injected into large amounts of water or hydrogen propellant. Efficiencies can be as high as 50 percent. After leaving the NEO, onboard crushers and grinders convert small amounts of the regolith to very fine powder. Smaller chemical engines are used to change orbits or to keep satellites in a particular orbit.
The heat generated by this arc causes the resultant gas to turn into plasma, thereby creating a charged gas cloud. According to Some Examples of Propulsion Applications Using Antimatter by Bruno Augenstein a tungsten block heated by antiprotons can heat hydrogen propellant up arcket a specific impulse of 1, to 1, seconds, depending up on the pressure the hydrogen operates at.
There had been many who had rocekt whether the effort needed to survive here was worthwhile, since the colonization of Mars and Venus offered much greater opportunities. The trouble is that it tends to decay spontaneously, with a lifetime of a mere 2. American inventions Revolvy Brain revolvybrain.
In addition, iron with the lowest specific impulse is sufficiently energetic for cislunar and asteroidal transportation.
Electric engines make up for this by running for months or years instead of minutes like chemical engines. Table gives the attunation for various rockket of tungsten radiation shields.
Variable Specific Impulse Magnetoplasma Rocket
The lead absorbs the gamma rays and radiates lower-energy X-rays, which vaporize the nozzle material. The plasmoid is expanded down a diverging electrically conducting nozzle. Two phase flow losses are estimated to be acceptable for anticipated throat sizes based on measured thrust loss data from solid rocket motors ustng aluminized propellants.
For instance the high density engine has a normalized thrust of 8. Many schemes have been proposed for extracting these metals and oxygen for agcjet, electrical, and materials processing space operations.
Industry for Key Deep-Space Capabilities. These engines are popular with the Russians and over have been used on their space missions.
Due to the nature of fusion torch drives, your small ships may be sitting on the end of a large volume drive assembly. They use so little power, watts or less and then only intermittently, that they can operate using residual electrical power already available on the satellite.
Posts promoting or facilitating piracy in any way will be removed.
Arcjet rocket | Revolvy
Compared to ion drives, MPDs have good thrust densities and have no need for charge neutralization. Making rcket stuff is easy. But you only need 27 rockdt of water to absorb MeV from a 75 MeV pion. Pulsed plasma thruster topic A pulsed plasma thruster PPTalso known as a plasma jet engine, is a form of electric spacecraft propulsion. Mirrors, like all magnetic fusion devices, can readily augment their thrust by open-cycle cooling.
Hall thrusters operate on a variety of propellants, the most common being xenon.
And yes, it’s easy to miss and pretty cool. The concentrating mirror is one half of a giant inflatable balloon, the other half is transparent so it has an attractive low mass. Electrostatic ion thrusters use the Coulomb force to move the propellant ions. Additionally, some classes of NEOs such as carbonaceous chondrites are expected to have extremely low mechanical strength; for such Roocket, it would be immaterial whether or not pre-existing regolith layers were rocet, as the crumbly material of the NEO could be crushed easily.
Stealth Boy — The first is past a locked door Novice to the left of a collapsed stairway in the small lobby with a broken, flooded floor. | 0.83073 | 3.083308 |
THE sun could be about to batter us with a shower of deep space rays so intense it could cause part of our atmosphere to COLLAPSE.
Space boffs reckon we are on the verge of a "deep solar minimum", which is a period of low activity.
Unlike the name suggests, this could cause an outer layer of the atmosphere called the thermosphere to contract - and it's not entirely clear what the effects of this could be on our planet.
Professor Yvonne Elsworth at the University of Birmingham believes that a "fundamental change in the nature of the [sun's magnetic] dynamo may be in progress".
It's backed by Nasa's Solar Dynamics Observatory's daily snaps which have shown a spotless sun for 44 days in a row.
This has led scientists to believe that it's nearing a tumultuous period not seen since 2008.
Solar minimums are known to spark lots of cosmic ray activity which can penetrate our atmosphere.
These cosmic beams cause "air showers" of particles when they hit our atmosphere.
They pose a health hazard to astronauts and a single stray cosmic ray could cause a satellite to malfunction.
As well as wiping out communication systems, a solar blast could down power grids, too.
It's not entirely clear why low solar activity causes our thermosphere to collapse - or what it might be doing to our planet.
But when it happened back in 2008/2009, scientists suggested that climate change might be adding to the cooling and contracting in the upper layer of our atmosphere.
The thermosphere begins at a height of about 53 miles above humanity's heads.
The International Space Station orbits the Earth within the middle of the thermosphere,
Professor Elsworth reckons it will be 2019 before we reach the peak minimum, but that we're already seeing strange things going on with our star.
In her recently published study of the sun, she wrote: "This is not how it used to be and the rotation rate [of the sun] has slowed a bit at latitudes around about 60 degrees.
"We are not quite sure what the consequences of this will be but it's clear that we are in unusual times.
"However, we are beginning to detect some features belonging to the next cycle and we can suggest that the next minimum will be in about two years," said Elsworth.
Nasa is sending a probe to “touch the sun” and unlock the mysteries of the star we're circling and prepare for any threats.
It will send a craft called the Parker Probe Plus on a journey within four million miles of the surface of the sun next year.
MOST READ IN TECH AND SCIENCE
The brave robot will face heat and radiation more intense than any spacecraft has endured before.
It said it was an “extraordinary and historic mission exploring arguably the last and most important region of the solar system”.
We pay for your stories! Do you have a story for The Sun Online news team? Email us at [email protected] or call 0207 782 4368 | 0.84465 | 3.665808 |
The real sun
The great physicist Newton told us that quite contrary to our everyday experience there is no such thing as a 'heavy' mass. An apple falls because it is attracted by earth. So where today's solar fusion theory assumes the biggest forces - at the center of a celestial body - they are in reality zero. Gravitational forces at the center of a celestial body simply cancel out. This may seem paradox at first glance but is basic vector math (see end of this page**). Gravitational forces decay to zero when you approach the center.
How today's astrophysics sees the nuclear energy production in the sun (see e.g.: http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/index.html )
This cancelation of the gravitational forces at the center of a celestial body is the reason why we find a solid core at the center of the earth (and as newer evidence shows at the center of the moon and the sun (see here or here : "solid body rotation") also, the gas and ice giants (Jupiter, Saturn...) are since long supposed to pocess a solid core and also the small bodies (see e.g. here) and this is the reason why celestial bodies of very different sizes are possible.
On Dec 13,2010 NASA reported: “The whole solar hemisphere erupted simultaneously in an avalanche effect that had been triggered in the tiny solar core and propagated outwards”. This brings more and more solar experts to agree that the sun has a solid core (Why this takes so long till it is fully accepted is the fact that this invalidates today's astronomy (and astrophysics) in whole - except f.i. wobbling stars. In a nutshell, today's astronomy classifies stars according to the Hertzsprung–Russell diagram. While this is in the first place only a luminosity/spectral type diagram, it is interpreted according to today's stellar astrophysics (fusion-theory) as a direct indication of the masses of the stars. This connection was introduced in 1926 by Arthur Eddington in his book 'The Internal Constitution of the Stars', initiating thereby today's astrophysics. Wikipedia:"In the process of developing his stellar models, he sought to overturn current thinking about the sources of stellar energy. Jeans and others defended the Kelvin–Helmholtz mechanism, which was based on classical mechanics, while Eddington speculated broadly about the qualitative and quantitative consequences of possible proton-electron annihilation and nuclear fusion processes." But also supernovae etc. are constructs and interpretations of the fusion theory. Read more here and here.). It seems this was the event and the reason that solar researchers started in 2011 for the first time to take into account that: "the sun might not be symmetric on the inside". If you can't believe it, you should read the whole thread.
Then there is the fact that the surface of the sun has a much lower average temperature than the corona, 5800 kelvin compared to the corona's temperature of one to three million kelvin. There is absolutely no lucid explanation how a fusion reactor at the center of the sun should heat the corona through a rather cold solar surface. Which now also other scientists see as 'mystery' which needs explanation. See also here and here. See also "The Sun as an X-ray Source". The search experiments for the missing solar neutrinos has reached the third generation. Popular explanation. But also other evidence challenges the assumption that H-fusion is the main source of energy that powers the Sun .
And "Despite more than 50 years of effort, today’s nuclearfusion reactors still require more power to run than they can produce". And compare this Sun spot record over last 60 years with the oscillogram that the here downloadable program computes (this program is no more downloadable, because it was a dos-program and you would need special graphics driver programs which today no more exist). You will be surprised... More here or under links.
Now if there are additional surface forces added - as for example in the case of the central body of a planetary system - we have a shining star. These forces additionally melt the thin outer crust. How we name the effect in the end is a matter of semantics, not physics. This is the whole 'mystery' of stars and therefor our sun.
Already in 2015 the mainstream astrophysics theory tried to build a bridge to a complete new understanding: "Effects associated with rotation can modify stellar properties, altering the luminosities, surface temperatures, sizes, and shapes of stars in ways that are unaccounted for in nonrotating models." There should be no doubt that already this statement invalidates all actual textbooks on astronomy and astrophysics.
As is known since long the sun rotates very much faster at its equator than at the poles, another fact for which today's solar fusion energy theory is not able to give a plausible explanation. The here downloadable program calculates the thus produced energy (in a preliminary calculation - if we understand the process fully, much better calculations will be possible) to 1.2 x 1022Ws to 2.0 x 1023Ws. The difference to the here on earth measurable 2.6 x 1026Ws to 1 x 1027Ws is due to plasma processes and other not regarded sources of heat in this preliminary calculation. Any theory which is not able to give a satisfying explanation for this differential rotation is bound to fail in the end.
Friction in the shear-layer produces heat (the measured 5800 Kelvin on the surface of the sun) which in turn produces convectional plasma flow in turbulent warps and waves. This turbulent action and induction produce in the plasma layer electric currents and magnetic fields which are responsible for the flares and coronal mass ejections of magnetized plasma gas. The flares heat the corona through resistive heating. This functions very similar to the toaster you use in the morning to toast your bread. The mass ejections are short circuits when two inversely polarized flares attract each other and finally collide.
Rotation period on the surface of the Sun
"The Sun is a ball of plasma and gas, and does not rotate like a rigid body. Its outer layers rotate differentially with equatorial regions being faster than the polar regions" (image:NASA)
Credit: The satellite Solar and Heliospheric observatory an international project of ESA and NASA
Rotate a glass of water in the below shown manner - you will get a rotation of the water as you see in the pictures above (expressed a little bit more scientifically 'spin-orbit-coupling'). And although this movement is really small and slow - this is the reason why it has been detected so late - it has, considered the enormous mass of the sun, enormous consequences as you can see in the photos above. And you don't need a degree in physics to understand that flares occure exactly there where you would expect them to occure (in the high resolution pictures above you can see them also on the surface of the sun). For more indepth simulations see here.
The NY-Times: The Wobbling Sun
Another big problem of astronomy is solved as a side effect. A big mystery for astro physics in general has always been the much too low angular momentum of the sun (search for angular momentum problem.). The Sun contains about 1000 times more mass than all the planets combined, but it possesses a mere 0.3 (0.5) percent of the total angular momentum of the solar system. "Jupiter (..)has about 60 percent of the solar system's angular momentum. The four jovian planets account for well over 99 percent of the total angular momentum of the solar system". (see also: "Astronomy today",Chaisson,McMillan,2005 Pearson Prentice Hall) (Non-uniform rotation presents a certain problem besides others. So the number should be taken as an orientation.)
other links if you want to read more on the subject:
http://www.zipcon.net/~swhite/docs/astronomy/Angular_Momentum.html (sun 4% of total angular momentum)
www.phys.utk.edu/daunt/Astro/.../Ch_15.ppt (four jovian planets account for more than 99% )
http://en.wikipedia.org/wiki/History_of_Solar_System_formation_and_evolution_hypotheses (the nebular/protoplanetary hypothesis is almost disproved)
at the end of this paper there is a condensed rough representation of today's theory concerning this point but also what makes today's theory so vulnerable to the argumentation of creationists etc:
http://cass246.ucsd.edu/~ppadoan/new_website/PHYSICS_1A/Lecture21.pdf ( no more accessible to the public? )
Links to Esa sun videos and photographs:
http://www.esa.int/esa-mmg/mmg.pl?topic=Sun&subtopic=Surface+features&subm1=GO&keyword=+--%3E+Keyword (solar surface)
http://www.esa.int/esa-mmg/mmg.pl?topic=Sun&subtopic=Eruptions&subm1=GO&keyword=+--%3E+Keyword (solar eruptions)
http://www.esa.int/esa-mmg/mmg.pl?topic=Sun&subtopic=Atmosphere+%28corona%29&subm1=GO&keyword=+--%3E+Keyword (solar atmosphere)
http://sohowww.nascom.nasa.gov/gallery/Movies/flares.html (FLARES & CMEs)
Some videos of the sun on YouTube
photos NASA/ESA and The satellite Solar and Heliospheric observatory an international project of ESA and NASA
In case there are other copyrights involved please tell me!
** Symmetry conditions at the center of a celestial body dictate the cancelation of the forces. A very much simplified mechanical 2-d model of a celestial body would consist of a ring and many springs symmetrically attached to that ring which are connected to each other at the other end. If all springs are of equal strength this connection point is located at the center of the ring. Now if you pull this center connection of the springs to any point inside the ring you get a rough impression of the forces at that point. (Outside the ring things get much more complicated and this simple model is no more applicable.) As you can clearly see the forces at the center cancel out and are very moderate in the vicinity of the center. You may even move this center point nearly halve way to the outer ring without exertion of too big forces. This is also in conformance with all newer measurements to the inner structure of the earth and here and here and here and here. And the moon as well. And also what all newer helioseismic measurements say (also here or here, popular article). "Solar experts (..) say the sun has an iron core". (Which leads to such remarkable statements as this one: "The innermost layer of the sun is the core. With a density of 160 g/cm^3, 10 times that of lead, the core might be expected to be solid. However, the core's temperature of 15 million kelvins (27 million degrees Fahrenheit) keeps it in a gaseous state." Original quotation from http://fusedweb.ppl.gov/CPEP/Chart_Pages/5.Plasmas/SunLayers.html where your browser will tell you that this governemental site is not trustworthy ??. After this site linked to that page the address changed to: https://fusedweb.llnl.gov/CPEP/Chart_Pages/5.Plasmas/SunLayers.html Should this quotation disapear once again, search for "sun density 160 g/cm^3" You will find many university servers with a similar statement.) Formerly it was assumed that the matter at the center of the earth is fluid - 'heavy' masses should exert biggest 'pressure' thereby liquefying the matter. It has even been "mooted in the past (..) that a natural nuclear reactor exists deep within the Earth...the possibility of such an underground reactor" (...cannot be ruled out) "but" (..data from KamLAND and Borexino) "place upper limits on how much heat could be produced by the reactor deep, if it exists". ( This arcticle is from July,2011!) The gas giants (Jupiter, Saturn..) are since long supposed to pocess a solid core. A condensed historical overview of the way to today's solar fusion theory you can read here. And last but not least this is also the reason for the perfect round shape of celestial bodies (centrifugal forces from rotation and gravitational irregularities neglected).
It should be noted that this model is really very much simplified and is only thought to demonstrate the cancelation of the forces. It has some severe deficiences in other aspects. This model serves the purpose to demonstrate that
gravitational forces don't push or press. There is no 'highest pressure' because of 'heavy masses' at the center of a celestial body. Gravitational forces attract, pull, they exert a tug.
300 years after Newton it is high time to put finally an end to this medieval thinking.
How today's physics sees the nuclear energy production in the sun (see: http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/index.html ) :
If you want to read more on nuclear fusion (articles to the real theoretical problems are not freely accessible in the net):
If you want to experience the actually changing view in science you should compare these two descriptions http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/SunLayers.html (new view, so it seems it is only a matter of time...) and wikipedia\Nuclear fusion - Wikipedia, the free encyclopedia.html(old view, the 2 pages are local copies of Sep 12, 2011 since wikipedia is ever changing) or this description: http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/index.html
Neutrino problem - despite contrary assertions it is not solved: http://www.tim-thompson.com/fusion.html and http://crio.mib.infn.it/wigmi/pages/cuore.php and http://arxiv.org/pdf/1104.1639
Nobel Laureate William A. Fowler (1988) ". . . we do not even understand how our own star really works."
Einstein wrong? Lab Claims Faster-Than-Light Particle
Read : Why Einstein was wrong here.
(should any link on this page be non functional: please tell me. I'll upload local copies in this case.) | 0.887778 | 3.640722 |
In Rendezvous with Rama (by Arthur C. Clarke), a mysterious object is discovered passing through the Solar System. The object has a strange shape — it’s a giant cylinder. It was discovered by the Spaceguard survey, designed to find objects that might impact Earth (so-called near-Earth objects). Spoiler alert: the cylinder is a spaceship sent by super-intelligent aliens to prospect for other space life.
Guess what? Rendezvous with Rama just happened in real life!
A month ago (Oct 19, 2017), the Pan-STARRS survey discovered the first object passing through our Solar System. (Like Spaceguard, Pan-STARRS was designed to find near-Earth Objects.)
The object is on a hyperbolic trajectory: it is simply passing through the Solar System. It feels the Sun’s gravity of course, but it is moving too fast to be bound to the Sun. It is just zooming through for a quick visit before it heads back to interstellar space. Here is a sweet animation of its path:
The object has been officially named 1I/’Oumuamua.
The name comes from Hawaiian ʻou.mua.mua, meaning “scout”, (from ʻou, meaning “reach out for”, and mua, reduplicated for emphasis, meaning “first, in advance of”) and reflects the way this object is like a scout or messenger sent from the distant past to reach out to us. (Source: Wikipedia)
A couple of things about ‘Oumuamua are pretty strange.
First, it passed very close to the Sun (within about 0.25 Astronomical Units) but it showed no signs of activity. When comets approach the Sun, small jets release water vapor (and other volatiles), creating a giant coma and tails. The Rosetta mission got up close to comet 67P/Churyumov–Gerasimenko and saw its jets in action:
Why doesn’t ‘Oumuamua have jets (or a coma or tails)? Maybe it’s rocky with very little ice. But it’s possible that ‘Oumuamua contains ice but only under the surface. There is a class of objects called Damocloids, that have comet-like orbits but no activity. The Damocloids are thought to be extinct comets, which passed close to the Sun so many times that they completely lost their water and volatiles. Maybe ‘Oumuamua is similar.
Second, ‘Oumuamua has a weird shape. It is super-stretched along one axis, which is about 10 times longer compared with the other two axes. It’s been called a cigar, but it might look like a cucumber. Or a baseball bat. Or a carrot. It rotates every 8 hours or so, tumbling along the shortest axis. (Like a cigar/cucumber/baseball bat/carrot thrown up in the air).
There is some disagreement between different groups on just how stretched-out ‘Oumuamua is; it could be at little as 3:1, more like an interstellar potato than a cigar. But, the cigar people have the better images!
The sad thing is that we will probably never know what ‘Oumuamua really looks like. It’s just too far away to get a resolved picture. To do that we would need an image from way up close. We’ve sent spacecraft to intercept comets and asteroids to see what’s really going on there. But ‘Oumuamua showed up too suddenly and is moving too fast. We’ll never catch up (at least not for decades). Big frowny face.
‘Oumuamua’s origins story probably goes something like this. It formed as a “planetesimal” (a planetary building block) in a disk orbiting a young star. Somehow it did not end up being incorporated into a planet. Instead, the gravity of the growing planets kicked it onto a stretched-out (eccentric) orbit, then kept kicking it until it was ejected into interstellar space. The most efficient ejection happens when a system with more than one giant planet becomes unstable. Here is an animation of an instability from my own research:
As you can see, when the giant planets go unstable, the whole outer disk of comet-like objects is completely ejected from the star, left to roam interstellar space. (Of course, some planets might share their fate, and some might even harbor life…). Comet-like objects are thought to be much more abundant than rocky ones, and also to be much easier to eject (rather than to be thrown onto the star). That is why we think it likely that ‘Oumuamua is closer to an extinct comet than to a rocky asteroid (see here for details).
There are a couple of final things that we can learn from ‘Oumuamua. Of course, let’s keep in mind that this is just one object. (How much do you learn about a movie from the first frame? How much do you learn about clouds from the first raindrop?)
First, ‘Oumuamua is small! It’s only about the size of a large stadium. That’s much smaller than we usually think the building blocks of the planets were. Is ‘Oumuamua a fragment created in a collision between building blocks? That might explain its weird shape, but at this point it’s just a guess.
Second, humanity is lagging behind! If this object was really sent by super-intelligent aliens, then we are just watching it pass by. Sure, we’re learning some interesting stuff but we don’t have the capabilities to catch up to ‘Oumuamua and make sure it’s not a real spaceship like in Rendezvous with Rama. I guess that means that we’re not even smart enough to end up in a Galactic zoo…. Sheesh,
The astronomy community is super-jazzed about ‘Oumuamua and I’m sure the story will keep unfolding over the coming months.
UPDATE: Upon writing this article, I was not aware of Project Lyra, a study of how to intercept and analyze ‘Oumuamua. This exciting concept is nicely-summarized in this article.
Questions? Comments? Words of wisdom?
- ‘Oumuamua on Wikipedia
- Nature paper by Meech et al
- Jason Wright’s blog post asking whether ‘Oumuamua could be an alien spacecraft (spoiler: doubtful)
- My own paper with some thoughts on ‘Oumuamua | 0.914328 | 3.731847 |
Asteroids are generally considered rocky, inert, and dry, with orbits in the Solar System comparable to those of the planets. On the other hand, comets have big, looping orbits and are full of volatile ices that discharge a dusty, misty halo and tail when approaching the Sun.
A recent discovery, however, challenges those definitions. Here is what astronomers found.
New Type of Asteroid Intrigues Astronomers
A newly spotted asteroid dubbed 2019 LD2 is genuinely fascinating. It appears to have a comet-like tail, and an orbit, similar to an asteroid. That’s unique, but not unknown – astronomers call asteroids that display comet-like features (such as sublimation and outgassing) active asteroids. So, it’s not the “what,” but the “where” that makes 2019 LD2 special.
2019 LD2 shares its orbit with Jupiter, in an asteroid colony known as the Jupiter Trojans. And it’s the first Jupiter Trojans astronomers have ever spotted discharging out gas like a comet.
The space object was first detected last year in June when the University of Hawaii’s ATLAS (Asteroid Terrestrial-Impact Last Alert System) captured a faint signal that seemed to be an asteroid in the Trojan category.
Other observations came quickly. But, it wasn’t until June 10, astronomers observed what appeared to be comet-like activity. Then, on June 11 and 13, they used the Las Cumbres Observatory and discovered the same behavior. Finally, the July 2019 results showed a trialing comet-like trail.
There are lots of asteroids in the Jupiter Trojan category, divided into two groups. One of it orbits in front of Jupiter, where 2019 LD2 is, and the other trails behind it, in curved areas concentrating on the planet’s Lagrangian edges. These are points where the mixed gravitational forces of two larger bodies (Jupiter and Saturn, in this case) develop a small area of gravitational balance. The Jupiter Trojans are challenging to study, but astronomers could find out a lot from taking a closer look at 2019 LD2.
As our second lead editor, Suzanne Fisher provides guidance on the stories Tech Life reporters cover. She has been instrumental in making sure the content on the site is clear and accurate for our readers. If you see a particularly clever title, you can likely thank Suzanne. Suzanne received a BA and MA from Fordham University. | 0.866216 | 3.622595 |
Exploring new worlds requires vision and some well-educated guesses; visual cues are nice, too.
The asteroid Psyche is a new world that will be explored by a group of space scientists led by Arizona State University. The project, which received funding from NASA in January, is underway and one of the early steps in the process has been to build a model of the target asteroid. In this case, the model is 3-D print of what Psyche might look like.
The model will fill an educational role, said Lindy Elkins-Tanton, the principal investigator of the Psyche mission and the director of ASU’s School of Earth and Space Exploration.
“It is really helpful to have visuals for people to interact with when we are talking about the mission,” she said. “It will be easier to have people look at this while we try to explain what we might find when we get there.”
Getting there won’t begin until 2023, when the mission is scheduled to launch. It will take seven years for the spacecraft to reach Psyche, which is located in the outer part of the main asteroid belt roughly 280 million miles from the sun. Psyche is large for an asteroid, about 130 miles in diameter, roughly the size of Massachusetts, and is thought to be the stripped core of a failed planet. That fact makes Psyche an intriguing piece of planetary debris to inspect.
“This is the first time humans will be able to explore a planetary core,” Elkins-Tanton said. “The mission will help us gain insights into the metal interior of all rocky planets in our solar system, including Earth.”
Beyond that, little is known about the mysterious Psyche. So how did they come up with a shape for it and its surface features to be incorporated into this model?
Elkins-Tanton said the fundamental shape of the model “is based on previously obtained radar returns. Its surface features, like how the craters look, are based on scientific hypotheses, because there are no images of its surface.”
In 3D Alley, a portion of the makerspace in the Technology Center on the Polytechnic campus, engineering associate Eddie Fernandez sets up the Objet 350 3-D printer for the Psyche job.
The Objet 350 is not the largest printer there, but it’s the most accurate with a resolution of 0.004 inches.
“This is a cool project,” he said. “It’s definitely different from what I usually get to print, and it has a greater amount of detail.”
Once everything is set, he begins the process, a continuous print that will run for 86 hours and 43 minutes. It will print the asteroid and its exterior supporting material horizontally, slice by slice. The printer head will traverse the printing table 6,619 times, stopping only periodically to clean its heads, laying down a layer of print material and immediately curing it.
“It’s going to be about as big as a basketball but as heavy as a bowling ball,” Fernandez said.
Sure enough, when the print completes, it yields what basically looks like a 28-pound birthday cake.
After the print, Fernandez takes the model to a cleaning station where he removes outer support material and uses water jets to clean the intricate surface of the miniature Psyche. After that a three-hour sonic bath removes any remaining support material, yielding a pristine asteroid.
The model matches artist renditions, Elkins-Tanton said. She and artist Peter Rubin worked for a couple of years on the computer animation. Plans are to paint the model, bringing it to another level of realism.
“The look of the model is based on science, based on scientific hypotheses of what it might look like and the radar returns we have,” Elkins-Tanton said, anticipating the first close-up inspection of the real thing.
“It’s going to surprise us,” she added. “I’m pretty darn sure of that.”
A time-lapse of the 3-D printing process, which took over 4 days. Shown here in 24 seconds. | 0.822128 | 3.351385 |
Almost a decade ago astronomers discovered a peculiar star system, BD +20 307, located 300 light-years from us. It has two stars about a billion years in age, and swirly, dusty debris all around it. What was peculiar about it was that the debris was warm, much warmer than it should have been. Astronomers realized that this was evidence of an impact collision between two exoplanets.
New observations, reported in The Astrophysical Journal, have shown that the infrared brightness is now more than 10 percent higher than it was nine years ago, a sign the system has gained even more warm dust over the last decade. These findings strengthen the view that a planetary collision was key to creating the unexpected warm dust.
“The warm dust around BD +20 307 gives us a glimpse into what catastrophic impacts between rocky exoplanets might be like,” said Maggie Thompson, a graduate student at the University of California, Santa Cruz, and lead author on the paper, in a statement. “We want to know how this system subsequently evolves after the extreme impact.”
Planets in star systems form from the dusty gas disks orbiting newborn stars. At first, these disks are warm, but as time goes on, they go from little pebbles slamming into each other to fully-formed planets. After a billion years, most of the dust not forming the planets should either have been pushed out of the system or pulled into the star, which is why the original detection was so striking. No one was expecting warm dust from a billion-year-old star.
The quick evolution of the system, observed by the Stratospheric Observatory for Infrared Astronomy, or SOFIA, is certainly intriguing and the team hopes to better understand how the BD +20 307 is evolving. This has implications for our own Solar System. The Moon is believed to have formed when a Mars-sized object impacted ancient Earth.
“This is a rare opportunity to study catastrophic collisions occurring late in a planetary system’s history,” said Dr Alycia Weinberger, from the Carnegie Institution for Science, and lead investigator on the project. “The SOFIA observations show changes in the dusty disk on a timescale of only a few years.”
The planetary collision hypothesis is not the only explanation for the data but it is the best explanation for the sudden increase in brightness witnessed over the last few years. | 0.859453 | 3.919742 |
A NASA spacecraft recently encountered Jupiter, and the University of Iowa was there for the rendezvous.
An instrument built at the UI is aboard the Juno spacecraft that made a star-spangled entry into Jupiter’s orbit on July 4. During the Juno mission, the orbiter will gather information about Jupiter’s interior, atmosphere, and magnetosphere. The long-awaited trove of data, scientists hope, will help them better understand the origin and evolution of the giant gaseous body that is by far the largest planet in the solar system, with a mass 300 times that of Earth.
William Kurth, research scientist in the Department of Physics and Astronomy at the UI, is lead co-investigator for the Waves instrument. Designed and built at the UI, Waves will sample the electric and magnetic fields of radio and plasma waves around Jupiter to determine how the planet’s auroras are produced.
• First space mission to operate a solar-powered spacecraft at Jupiter
• Farthest solar-powered spacecraft from Earth
• First space mission to orbit an outer planet from pole to pole
• First space mission to fly as close as 2,600 miles to Jupiter’s cloud tops
• First mission designed to operate in the heart of Jupiter’s radiation belts
• Will take the highest-resolution images of Jupiter in history
Auroras, called northern or southern lights because they’re most visible in Earth’s polar regions, have dazzled humans for eons. The atmospheric fireworks at Jupiter’s poles, powered by the planet’s rotation, are the brightest in the solar system, making the Earth’s display seem puny by comparison.
“It would take 200 times the power generation capability of the U.S. to equal the power driving Jupiter’s auroras,” says Kurth, who will be at NASA’s Jet Propulsion Laboratory in California when the Juno spacecraft settles into Jupiter’s orbit.
Waves’ primary sensor is located on the bottom of the craft, with two nine-foot-long whip antennas that stick out “like seagull wings,” Kurth says. The group of engineers and scientists that helped design and build the instrument included Donald Kirchner, Terrance Averkamp, and George Hospodarsky. Along with Kurth and Hospodarsky, physics professor Don Gurnett and postdoctoral research scholar Masafumi Imai will interpret data collected from the mission.
The Waves instrument has two sensors: The first, an electric dipole antenna, is a V-shaped device similar to the rabbit ears that once were common on TVs. It will detect the electric component of radio and plasma waves. The second sensor is a magnetic search coil, which is sensitive to only the magnetic component of plasma waves.
Waves will take measurements in Jupiter’s magnetosphere as Juno darts just above the atmosphere. The planet’s magnetic field is immense and intense: Its tadpole-like shape balloons 600,000 to 2 million miles toward the sun and tapers into a long tail that extends more than 600 million miles from Jupiter, reaching as far as Saturn’s orbit.
Jupiter also contains radiation belts that are hundreds of times more intense than Earth’s Van Allen radiation belts discovered by and named after UI space pioneer James Van Allen.
“It’s a place where you don’t want to spend much time if you don’t have to,” Kurth says.
Juno lifted into space on Aug. 5, 2011. In October 2013, it executed a slingshot maneuver around the Earth, using our planet’s gravity to propel the spacecraft toward Jupiter. The mission is scheduled to end in February 2018, after traveling 2.1 billion miles.
Since 1958, the UI has designed and built instruments for 69 successfully launched spacecraft. Seventeen are currently carrying UI instruments. | 0.856659 | 3.823178 |
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