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The geological record on Earth is most conveniently studied and catalogued as a chronological development of changes. The geological law of superposition rules supreme, that younger layers lay above older ones - though there are some profound exceptions like during mountain-building when crunching-shoving forces move things around and tip them over. We don't even like to mention that there is a big upside-down rock series in the Spring Mountains west of Las Vegas due to big-scale 'thrust faulting', shoving an older rock series on top another. But we have A SINGLE METHOD of determining absolute ages of rocks, by measuring the results of radioactive decay of chemical elements like uranium, thorium, potassium, rubidium, etc. I personally worked in such a lab in Tucson for 10 years and know the process and its various pitfall traps. (Carbon-14 or radiocarbon dating shares the basic process of measuring radioactive decay, but can only be used to age-date dead organic tissues, and not rocks, that are less than ~50,000 years old.) The first age-dates on rocks were made in about 1896 in Britain, and were surprisingly precise, but a major advance came in about 1950 with new high-tech equipment called a mass spectrometer that could measure isotope levels. The technique is too tricky to explain here except to say that what is measured is the ratio between a 'parent' radioisotope (uranium, rubidium, potassium) and its 'daughters' of decay (lead, strontium, argon). The ratio goes into an equation of exponential decay using an extrapolated laboratory-measured rate of decay (half-life), and an age of the rock is determined. This represents the age of formation by cooling of an igneous rock, or the last time of an intense heating of the rock that redistributes isotopes that 'resets' the clock. We now have more than 50,000+ age-dates on rocks around the world (my guess).
The body of combined age-dates of the world's rocks produces a logical sequence of events. There are indeed spurious age-dates that we must contend with. Religious fundamentalists use these anomalies to discredit the entire science as they desire enlightenment, just like the rest of us.
The game is to figure out our planet's history. Go to other sources for details. Based upon stratigraphy and geological events worldwide we divide total Earth history into four major eons of time, thus Figure 2, see above.
Hadean Eon is the time before surface rocks formed when the entire planet became molten due to intense radioactive decay and when the heavy metal core congealed at the center. The solar system seems to have been born in orbit of the Milky Way galaxy's center point, taking about 250 m.y. to go around once - so far, 11 times around. Early in Hadean time was when, by best account, a small stray planet hit Earth, blew a fair chunk of rock debris out, some of which went into orbit, then collected together into the body we call the moon. Why don't we have a name for our moon? It's like calling your dog 'dog', or 'Hey You!' I much prefer the name 'Georgette' or perhaps 'Appleyard.' Anyway, that just had to be a bleak Thursday early in Hadean time. Another early possible cataclysmic event was a minor 'readjustment' of the vigorous young sun called a 'T-tauri' explosion whose solar wind outburst may have blown away the bulk of the atmospheres of the inner planets, explaining why the outer planets have such thick atmospheres. No oceans then - too hot, so all the water that seeped out of the inner Earth after T-tauri time was present as a steam atmosphere along with nitrogen, carbon dioxide, methane, etc. Water vapor got blown out as far as Pluto that has tall mountains of ice. Little or no oxygen on Earth in the early days. At 3,900 m.y. it is guessed that two other planets collided, producing the asteroid belt (with pretty good evidence), but then a bunch of stray debris hit all other planets, causing great welts on the moon and Mars, and on Earth. Most of the moon's craters are thought to have formed at that time. There are some big ones still visible on Earth such as in eastern Quebec Canada, seen easily on Google Earth, and 150+ others. An impact in South Africa called the Vreedefort ring damaged the early crust that then bled out huge volumes of basalt magmas that happened to bring up enough gold to become the site of the world's largest gold mine, and then, tremendous human greed and angst.
During Archean time the planet became covered with an initial thin oceanic basalt crust. It thickened with basalt volcanoes everywhere, and soon pockets of a new kind of magma were produced, a less dense rock called granite that rose and solidified into mushroom-shaped islands. And so were born the cores of continents. Figure 7 shows details of this process - see the figure's write-up. And as the atmospheric temperature dropped below 212° F, the oceans started condensing as shallow freshwater boiling lakes in early valleys. Heat-loving bacterial life showed up very early and lived on the first sandy shores of the island continents, basking in the near-boiling tidal waters. Their fossils, oldest on Earth, are in the coastal Isua Complex of SW Greenland. These bacteria still live - called 'bifs' (banded iron formations) (Figures 37 & 38), blown out of black smoker hot spring vents in the oceanic spreading centers. The fellow who first dove in the Alvin submarine to discover these smoker vents in about 1978 off the southern tip of Baja California, Jack Corliss, was my boss during Biosphere 2 construction.
Then at about 3,500 m.y. ago we find the earliest fossil traces of another life form called stromatolites, with the capability of photosynthesis (Figures 39 & 40), so that levels of their waste oxygen started to increase in the atmosphere. They still live in intertidal zones of warm oceans, shaped like 1-2 foot diameter mushroom-shaped heads in colonies or simple bio-scums. Photosynthesis is an extraordinarily tricky process to have begun by 'chance' atomic encounters, and this process of conversion of sunlight into chemical energy sits as a huge stumbling block towards our understanding of life's origin. I once had a very interesting afternoon coffee at Biosphere 2 (Oracle) with H.J. Morowitz, an expert on the origin of life. Like the rest, he was grappling with the whopping improbability of this reality.
During Proterozoic time the continents grew much larger, to nearly their modern extents. At about 2,500 m.y. ago were the first obvious signs of some oxygen in the atmosphere, marked by the presence of 'redbeds,' which are sandstones with their sand grains stained red-brown by oxidized iron minerals like hematite. Signs of massive continental collisions - the early mountain chains they produced, now worn away into plains like across the Canadian Arctic. The first marine floating algae are recorded at 2,000 m.y. (Figures 34 & 35), and then later, marine burrowing worms (Figures 41 & 42) and jellyfish, and then sponges and many other unrecognizable critters who left fossil traces. A supercontinent called Rodinia came crashing together late in the eon, and finally broke up.
Phanerozoic time saw vigorous continental drift and many temporary arrangements of continental groups. For awhile there were two big clusters, called Laurasia and Gondwanaland. Then all conjoined into Pangea at the end of Paleozoic time, and then it broke apart with parts drifting into modern positions. Figure 5 displays this last breakup dance. During Phanerozoic time came the great bursting forth of multitudes of life in the oceans and on the continents by some extremely mysterious process, something called evolution. We do not understand more than a modicum of that process. The process is hidden behind barriers that we cannot breach, such as the fact that we can find fossil traces of some 0.01% of all organisms that have likely ever lived. Human history is similarly sketchy as we continue to destroy all the libraries. See E.O. Wilson's book, The Diversity of Life, (W.W. Norton, 1992) or Richard Fortey's book Life.
All of the Southwest - the lands south of southern Wyoming and west of Denver - contain only rocks of the Proterozoic and Phanerozoic eons, and nothing older than about 1,800 m.y.. Wyoming and land northward contains Archean-age rocks. There are no rocks on Earth from the Hadean eon, the time after formation when the Earth virtually melted so that all older rocks were recycled. There are Archean rocks on all major continents. Oldest rocks preserved on Earth are found in SW Greenland, NW Canada, NW Australia, central Africa. A great showing of late Archean rocks, granites and gneisses, is the fabulous mountains of Grand Teton National Park of Wyoming, with great hiking trails - take the Jenny Lake trail up the canyon. Gneiss is a layered igneous rock with the minerals of granite with layers due to intense compression.
There is a large-scale issue regarding the age distribution of continental rocks across the planet. Since Archean time we can find many rock sequences through all of time, except for a great scarcity of rocks between about 1,500 and 550 m.y. ago - with only a few exceptions. This time seems to mark a period when the Earth's surface was very quiet, with little or no continental drift, mountain-building, volcanism, or other disruptive process. But surely the production of inner heat continued, which is the driving force of it all. So what happened? We guess that some kind of re-arrangement of internal layering was taking place at a layer boundary buried down about 670 kilometers (420 miles). This time of missing rock record is found on all continents, and is labeled the time slot of the Great Unconformity, glibly called the 'missing time' interval. Time's not missing, its all here, just the rocks are missing. It represents about one-quarter of planetary history - gone - missing - kaput. No preserved rock record, except in a very few places, that happens to include Arizona. Planetary development has not been a steady forward-march of events. Progress is a word for humankind's ego, not planetary events. But change seems inevitable. | 0.91332 | 3.372131 |
Dark Energy should not to be confused with Dark Matter or Dark Fluid.
In astronomy and cosmology Dark Matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation.
Dark Fluid is an alternative theory to both Dark Matter and Dark Energy that attempts to explain both phenomena in a single framework. It proposes that dark matter and dark energy are not separate physical phenomena as previously thought, nor do they have separate origins, but that they are linked together and are really specific sub-effects of new extended laws of gravity at very large scales.
While dark energy repels, dark matter attracts. Dark energy shows itself only on the largest cosmic scale, while dark matter exerts its influence on individual galaxies as well as the universe at large. About one-quarter of the universe consists of dark matter, which releases no detectable energy, but which exerts a gravitational pull on all the visible matter in the universe.
In physical cosmology, astronomy and celestial mechanics, dark energy was a hypothetical and allegedly confirmed form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most accepted theory to explain recent observations and experiments that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.
Two proposed forms for dark energy are the cosmological constant, originally proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. Einstein abandoned the concept after the observation of the Hubble redshift indicated that the universe might not be stationary, as he had based his theory on the idea that the universe is unchanging. However, a number of observations including the discovery of cosmic acceleration in 1998 have revived the cosmological constant, and the current standard model of cosmology includes this term.
Researcher finds hint of dark energy discussion in letters between Einstein and Schrodinger PhysOrg - December 11, 2012
Alex Harvey, a physics professor at the City University of New York has uploaded a paper in which he claims Albert Einstein and Erwin Schrodinger were writing letters suggesting the two men were on the precipice of discussing the possibility of the existence of dark energy. The letter exchange came in the years after Einstein had published his theories on general relativity, and revolved around the matter of the cosmological constant.
The first direct evidence for dark matter was discovered while studying the outer regions of the Milky Way Galaxy.
The first direct evidence for dark energy came from supernova observations of accelerated expansion, in Riess et al. and later confirmed in Perlmutter et al. This resulted in the Lambda - CDM model, which as of 2006 is consistent with a series of increasingly rigorous cosmological observations, the latest being the 2005 Supernova Legacy Survey. First results from the SNLS reveal that the average behavior (i.e., equation of state) of dark energy behaves like Einstein's cosmological constant to a precision of 10%. Recent results from the Hubble Space Telescope Higher-Z Team indicate that dark energy has been present for at least 9 billion years and during the period preceding cosmic acceleration.
The term dark energy, echoing Fritz Zwicky's dark matter from the 1930s, was coined by Michael Turner in 1998. By that time, the missing mass problem of big bang nucleosynthesis and large scale structure was established, and some cosmologists had started to theorize that there was an additional component to our universe.
In the 1970s Alan Guth proposed that a negative pressure field, similar in concept to dark energy, could drive cosmic inflation in the very early universe. Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the Big Bang. Such expansion is an essential feature of most current models of the Big Bang. However, inflation must have occurred at a much higher energy density than the dark energy we observe today and is thought to have completely ended when the universe was just a fraction of a second old. It is unclear what relation, if any, exists between dark energy and inflation. Even after inflationary models became accepted, the cosmological constant was thought to be irrelevant to the current universe.
Scientists use quasars to probe dark energy over 10 billion years in the past PhysOrg - November 13, 2012
BOSS, the Baryon Oscillation Spectroscopic Survey, is mapping a huge volume of space to measure the role of dark energy in the evolution of the universe. BOSS is the largest program of the third Sloan Digital Sky Survey (SDSS-III) and has just announced the first major result of a new mapping technique, based on the spectra of over 48,000 quasars with redshifts up to 3.5, meaning that light left these active galaxies up to 11.5 billion years in the past.
Dark energy is real, say astronomers PhysOrg - September 12, 2012
Dark energy, a mysterious substance thought to be speeding up the expansion of the Universe is really there, according to a team of astronomers at the University of Portsmouth and LMU University Munich. After a two-year study led by Tommaso Giannantonio and Robert Crittenden, the scientists conclude that the likelihood of its existence stands at 99.996 per cent.
Dark Energy, Dark Matter NASA - April 2012
We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 70% of the Universe is dark energy. Dark matter makes up about 25%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the Universe.
Is Dark Energy Really "Repulsive Gravity"? National Geographic - February 16, 2012
A powerful repulsion between normal matter and hidden pockets of antimatter could be an alternate explanation for the mysterious force known as dark energy, according to a controversial new theory. In 1998 scientists discovered that the universe is not only expanding but that its expansion is accelerating. This totally unexpected behavior has been called the "most profound problem" in physics, because our current understanding of gravity says that attractions between mass in the universe should be causing the expansion to slow down.
Galaxy Evolution Explorer finds dark energy repulsive PhysOrg - May 20, 2011
New results from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy (represented by purple grid) is a smooth, uniform force that now dominates over the effects of gravity (green grid). The observations follow from careful measurements of the separations between pairs of galaxies (examples of such pairs are illustrated in the image above). The five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds.
Dark Energy vs. The Void: What if Copernicus was Wrong? PhysOrg - September 26, 2008
Dark energy is at the heart of one of the greatest mysteries of modern physics, but it may be nothing more than an illusion. The problem facing astrophysicists is that they have to explain why the universe appears to be expanding at an ever increasing rate. The most popular explanation is that some sort of force is pushing the accelerating the universe's expansion. That force is generally attributed to a mysterious dark energy. Copernicus was among the first scientists to argue that we're not in a special place in the universe, and that any theory that suggests that we're special is most likely wrong. The principle led directly to the replacement of the Earth-centered concept of the solar system with the more elegant sun-centered model.
Dark Energy: The Movie Hubble Website - December 7, 2007
The universe we can see ... the universe we can touch ... is only a tiny fraction of the universe that exists.
Mysterious Dark Energy Has Existed For Most of Time, Scientists Say National Geographic - November 17, 2006
Peeling back both space and time, scientists using the Hubble Space Telescope have found that the strange force known as dark energy appears to have existed for at least the past two-thirds of the universe's history. Dark energy is a mysterious repulsive force that opposes gravity, causing the universe to expand. Albert Einstein posited that a form of the force existed nearly a century ago by, but it was not discovered until 1998.
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Both Voyager spacecraft are only in communication with Earth via a Canberra tracking station.
The Voyager space probes sent back some amazing images of the planets in the outer Solar System, and they're still talking to Earth every day via Australia's tracking station.
The raw images of Jupiter’s Great Red Spot taken this week by the Juno probe.
The images are in from the Juno probe's closest flyby so far of Jupiter's Great Red Spot. Citizen scientists are now getting involved in processing those images.
Jupiter’s Great Red Spot observed by Juno in July 2017.
.NASA/JPL-Caltech/MSSS/Kevin M. Gill
Juno has flown closer to the solar system's most famous storm than any other spacecraft to take the most detailed images to date. They may help scientists reveal some of the spot's best-kept secrets.
This enhanced-color image of Jupiter’s south pole and its swirling atmosphere was created by citizen scientist Roman Tkachenko using data from the JunoCam imager on NASA’s Juno spacecraft.
We may need to re-think our models of Jupiter’s formation thanks to the first results from Juno probe orbiting the planet, and new observations from Earth.
New close-up of Jupiter’s south pole. The oval features are cyclones.
: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
Measurements suggest Jupiter's core may be fluffy rather than dense and that its magnetic field is much stronger than previously thought.
This illustration shows Cassini diving through geyser plumes on Saturn’s the ocean world
moon of Enceladus.
Earth is a relatively dry planet compared to some of the other ocean worlds in our Solar system. Life needs water so what about life on these other places?
A likely candidate for life: Saturn’s icy moon Enceladus.
NASA/JPL-Caltech/Space Science Institute
There has been much excitement this week about the possibility of water -- and life -- on some newly discovered exoplanets. But we can look closer to home for evidence of ET.
An artist’s concept of what it could look like on the surface of one of the exoplanets of TRAPPIST-1.
Several of the newly-discovered exoplanets orbiting a small star appear to be locked in an intricate dance that hints at how such planetary systems can form.
Hi Juno, welcome to Jupiter.
From the discovery of gravitational waves, to the Pokémon Go phenomenon to the Census debacle, it's been a big year in science and technology.
Jupiter’s South Pole, as seen by NASA’s Juno spacecraft on August 27 2016.
Credit: NASA/SwRI/MSSS, processed by R. Tkachenko
NASA's Juno spacecraft has faced a series of challenges during its first 150 days.
New research solves enigma of strange hotspots in Jupiter's atmosphere.
An artist’s impression of Juno above Jupiter’s pole.
Juno’s visit to Jupiter promises to pick up on many of the unsolved mysteries that still remain in understanding of the Jovian system.
Jupiter and its Great Red Spot.
NASA, ESA, and M. Kornmesser.
Look towards the north-west after sunset and there is currently one bright point of light that easily stands out relative to everything around it. That is the planet Jupiter, shining with an intense and…
Artist’s concept of the Juno mission to Jupiter.
The perilous Juno mission could help reveal how Jupiter formed, whether it has a rocky core and even whether it influenced life on Earth.
Enceladus, with its warm internal ocean, is thought to be potentially habitable.
Marc Van Norden/Flickr
A new theory could change our understanding of the moons in our solar system – and the genesis of life itself.
Juno in front of Jupiter.
Missions including ExoMars, Juno and Rosetta could make some major discoveries in 2016.
It's regarded as a Biblical myth, but what the magi are supposed to have seen is rooted in astronomy.
Artist’s depiction of the newly discovered Jupiter-like planet orbiting the star HD 32963.
Jupiter had a big influence on how our solar system's planets formed. New research – led by a high school student – tried to nail down how rare Jupiter analogs really are in other planetary systems.
Recent Martian findings are just the latest discoveries of aurora on other planets, both in and out of our solar system.
Jupiter and its shrunken Great Red Spot.
NASA, ESA, and A. Simon (Goddard Space Flight Center)
Climate change is altering the iconic face of Jupiter, too | 0.894619 | 3.308528 |
Only three or four supernovas happen in our galaxy every century. These are super-energetic events that release neutrinos at the speed of light. At the Super-Kamiokande detector in Japan, a new computer system has been installed in order to monitor in real time and inform the scientific community of the arrival of these mysterious particles, which can offer crucial information on the collapse of stars and the formation of black holes.
A kilometre underground, in the depths of a Japanese mine, scientists have built a tank of ultra-pure water inside a gigantic cylinder full of photomultiplier tubes. This is the Super-Kamiokande experiment, one of the major objectives of which is the detection of neutrinos -particles with near-zero mass- that come from nearby supernovas.
The problem is that these stellar explosions occur very infrequently: only three or four each century in our galaxy. For this reason, the members of the international Super-Kamiokande scientific collaboration want to be prepared for one of these rare phenomena and have built a ‘monitor’ that is constantly on the lookout for a nearby supernova. The details are published in the journal ‘Astroparticle Physics’.
“It is a computer system that analyses the events recorded in the depths of the observatory in real time and, if it detects abnormally large flows of neutrinos, it quickly alerts the physicists watching from the control room,” Luis Labarga, a physicist at the Autonomous University of Madrid (Spain) and a member of the collaboration, explained to SINC.
Thanks to this neutrino monitor, experts can assess the significance of the signal within minutes and see whether it is actually from a nearby supernova, basically inside the Milky Way. If it is, they can issue an early warning to all the interested research centres around the world, which they provide with information and the celestial coordinates of the source of neutrinos. They can then point all of their optical observation instruments towards it, since the electromagnetic signal arrives with a delay.
“Supernova explosions are one of the most energetic phenomena in the universe and most of this energy is released in the form of neutrinos,” said Labarga. “This is why detecting and analysing neutrinos emitted in these cases, other than those from the Sun or other sources, is very important for understanding the mechanisms in the formation of neutron stars -a type of stellar remnant- and black holes”.
“Furthermore,” he added “during supernova explosions an enormous number of neutrinos is generated in an extremely small space of time -a few seconds- and this why we need to be ready. This allows us to research the fundamental properties of these fascinating particles, such as their interactions, their hierarchy and the absolute value of their mass, their half-life, and surely other properties that we still cannot even imagine”.
Labarga said that the Super-Kamiokande is permanently ready to detect neutrinos, except for essential calibration or repair intervals. Any day could take us by surprise.
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Fireworks near the Big Dipper
Twenty-one million years ago, a white dwarf star exploded in a burst of light and energy that began racing through space in all directions. In late August, a robotic telescope in California detected evidence of the event. Word went out to stargazers all over the world. Soon, they turned their telescopes to watch the light show.
And they were delighted.
A star explosion is called a supernova. And it’s rare for astronomers to see one that’s so close. (The star that exploded was about 21 million light-years away, which makes it a nearby neighbor. Since a light-year is the distance covered by light in one year, it took 21 million years for evidence of the explosion to reach Earth.) It’s also uncommon to see a supernova from beginning to end, so this one — named PTF 11kly — was a stellar surprise.
“Saying it’s ‘once in a generation’ is very true,” Peter Nugent told Science News. This astronomer works at the Lawrence Berkeley National Laboratory in California. He was part of an international team who made the discovery. He said only three similar supernovas have been witnessed so close to Earth in the past 40 years.
“We think we found it probably 12 hours after it exploded [into view],” Mark Sullivan told Science News. Sullivan is an astronomer at the University of Oxford in England. Like Nugent, he’s part of the international research team, which uses a robotic telescope on Palomar Mountain, about 100 miles from Pasadena, Calif.
The star is part of the Pinwheel Galaxy. It appears near the Big Dipper in the night sky. On August 23, the star was far too faint to be seen by human eyes. Then, on August 24, the star became six times brighter. This change in brightness was picked up by the telescope. Astronomers predicted that the supernova would continue to brighten for about two weeks, when it would be bright enough to see with binoculars (at least for people under clear skies on a moonless night).
Astronomers call the newly discovered explosion a Type Ia supernova. This kind of supernova forms when two stars race around each other. One of the stars is called a white dwarf. These types of stars are superdense: A tablespoon of white-dwarf matter weighs 15 tons. White dwarfs have a powerful gravitational force, so they steal mass from their companion star. Eventually, so much extra mass piles up that the white dwarf star explodes.
Type Ia supernovas, which are about four billion times as bright as the sun, have played an important role in the history of astronomy. Scientists have used these stellar explosions to estimate the distance from Earth to distant galaxies. By studying Type Ia supernovas, scientists also have learned that the universe is expanding — and that this expansion is speeding up.
Scientists are now doing a bit of detective work to see if they can learn more about the supernova. They’re studying older pictures of the part of the sky where the supernova took place to see what the white dwarf and its companion looked like before the dazzling display of fireworks.
POWER WORDS (adapted from the New Oxford American Dictionary and NASA’s “Imagine the Universe”)
supernova A star that suddenly gets brighter because of a catastrophic explosion that ejects most of the star’s mass.
galaxy A system of gas, dust and millions or billions of stars held together by gravity.
type Ia supernova A supernova that results from some binary (paired) star systems in which a white dwarf star gains matter from a companion. The white dwarf eventually gains so much mass that it explodes.
white dwarf A small, very dense star that is typically the size of a planet.
telescope An instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses.
N. Drake. “Star goes boom, telescopes zoom.” Science News. August 30, 2011.
You may still have a chance to see the supernova for yourself! This video, from the Berkeley Lab, shows you how.
S. Ornes. “The dark side of the universe.” Science News for Kids. April 26, 2011. | 0.8479 | 3.717716 |
Above: Fraser Cain of Universe Today talks us through it.
Human colonisation of Venus doesn't sound too smart on paper. Terraforming Venus – a world that is much closer to Earth in size, surface gravity, and location than almost any other – is a much harder proposition than terraforming a sun blasted airless desert like Mercury or our Moon.
Mainly because of what is already there – Venus’ atmosphere. The surface is drowned under a CO2 atmosphere so thick and hot it's almost more like a boiling ocean, and turns the planet into a badly maintained suburb of hell. The pressure is over 90 atmospheres, and the temperature tops 450 degrees Celsius everywhere except the mountaintops – on which heavy metals, rather than H2O, snow out as a glittering coating.
|Above: The barren rocks of Venus today, beneath the hazy sky and pressure cooker atmosphere.|
To add to the worrisome brochure reading for a colonist, it rains sulphuric acid.
If people are ever to live there we need to renovate, but to do that we’d need to remove that sweltering atmosphere. Here are a few of the ideas most often tossed about:
1: Drop thousands of huge asteroids onto Venus.
It’s the brute force and ignorance approach – smash huge asteroids hundreds of kilometres wide into Venus until the atmosphere is blasted away into space. Brute force and ignorance has a lot of charm in some situations, but in this one it’s stunted by the Venusian gravity: Nearly as strong as Earth’s, it means that it would take thousands of such huge impacts to eject enough atmosphere. Worse, the ejected atmosphere would remain in the vicinity of Venus’ orbit, so that same high gravity might well just re-absorb it. Lastly there’s the inconvenient fact that either wed have to space the asteroid strikes so widely that the whole process took hundreds of thousands of years, or so many huge asteroid strikes in quick succession would turn Venus surface into a lava ocean, like the new born Earth had – a lava ocean that would generate lots of hot gas, replenishing the lost atmosphere.
|Send in the Willis|
2: Drop massive amounts of calcium and magnesium from space.
A more realistic alternative is to use chemistry on a massive scale to turn Venus’ atmospheric gas into something else. One idea - less mad than dropping huge asteroids but still pretty mind bending in scale - is that the atmosphere could be reacted with refined magnesium and calcium, turning it into carbonate rock. Using calcium and magnesium we’d need more than twice the weight of the giant asteroid Vesta of each.
|Above: The giant asteroid Vesta. A whole lotta rock.|
3: Drop huge amounts of hydrogen into the atmosphere.
The atmosphere could also be reacted with hydrogen, via an aerosol of iron in the atmosphere, turning it into graphite and water. The attraction of this approach is that it delivers a worldwide ocean to Venus (roughly 10% the volume of Earth’s) at the same time the atmosphere thins. If we used the hydrogen approach we’d need mass mine hydrogen from the water ice of one of the icy moons of Jupiter or Saturn. Still, this would make a more workable approach than the giant asteroid strikes, unless anyone’s especially fond of living on a ball of lava.
And no one wants to live on a ball of molten lava.
Aside from Darth Vader (minor spoiler for Star Wars: Rogue 1 there, sorry).
|Vader, Sauron, Voldemort...I can't help but think there's an Ikea 'dark lord's castle' flatpack all these guys are all just modifying slightly.|
4: Freeze the atmosphere out:
This is actually a way that falls between terraforming Venus and simply colonising its atmosphere: Cool it with sunshades. Once it drops below a certain point the atmospheric CO2 would start to snow out as crystals that could then be scooped up and shipped off world. There are two ways we could freeze Venus enough to do this: Orbiting sunshades, or with sunshades floating in the upper atmosphere.
If we based our reflectors in space they’d have to be big – and by big I mean really, stupidly, huge: The best place to site such a reflector would be the point where the Sun’s gravity and Venus gravity cancel out… but it would need to be four times wider than Venus itself.
It’s the second option that would give the crossover with more near term colonisation – there would need to be an enormous number of sunshades floating in the Venusian atmosphere, and some of them could actually be floating cities. Keeping them aloft wouldn’t be a problem, as breathable air would be a lifting gas on Venus. We’d only need to coat the upper surface with a high reflectivity layer, and they'd fit right in with the countless floating reflectors we'd need to fill the atmosphere with.
|Above: An artists impression of a huge floating city in the atmosphere of Venus.|
The time scale for all of these ideas is looong – thousands of years – but eventually the atmosphere would thin. Water and organic molecules to support life could be imported from the outer solar system. What would our new Venus be like?
Exactly what we got would depend on how we'd gone about terraforming it, but a few key differences would be:
- The Sun rises in the west and sets in the east
- One day is 117 Earth days long - so daytime temperatures near the equator will climb ferociously high, and night time ones will be able to get bitterly cold
- There's no moon in the sky, but Mercury shines as a brilliant evening / morning star, and the Earth and moon are an incredibly bright point of light in the night time sky.
- Venus has no axial tilt to speak of - so there are no seasons.
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|Above: An artists impression of a terraformed Venus| | 0.811883 | 3.689075 |
Each year between 15 and 18 November (approximately), typically peaking between midnight and dawn on 17 November, the the Earth encounters the Leonid Meteors, one of the more spectacular of the annual meteor showers, although it is likely to be a poor show this year as both the closest lunar perigee of the last five decades (i.e. the point at which the Moon is closest to the Earth fot the last five decades) and the full Moon fall on Monday 14 November this yeat. Unlike most such showers, which are essentially composed of dust particles, the Leonids comprise particles of up to 8 mm across and up to 85 g in mass, leading to some spectacular fireballs, and each year the shower is thought to deposit 12-13 tonnes of material on the Earth. The Leonid Meteor Shower is so called because the meteors they appear to originate in the constellation of Leo. (Note a meteor is a 'shooting star', a piece of material visibly burning up in the atmosphere and detectable via the light it produces when doing this; a meteorite is a piece of rock that has fallen from the sky and which a geologist can physically hold; and an asteroid is a chunk of rock in orbit about the Sun, to small to be regarded as a planet.
The Leonid Meteors are thought to originate from the tail of Comet 55P/Tempel-Tuttle, which orbits the Sun every 33 years, on an orbit that brings it slightly within the orbit of the Earth then out to slightly beyond the orbit of Uranus. Comets are composed largely of ice (mostly water and carbon dioxide), and when they fall into the inner Solar System the outer layers of this boil away, forming a visible tail (which always points away from the Sun, not in the direction the comet is coming from, as our Earth-bound experience would lead us to expect). Particles of rock and dust from within the comet are freed by this melting (strictly sublimation) of the comet into the tail and continue to orbit in the same path as the comet, falling behind over time.
The material in the meteor shower is densest close behind the comet, and, since Comet 55P/Tempel-Tuttle has a 33 year orbit, the Leonid Meteor Shower has a 33-year cycle, with a particularly spectacular display every thirty-third year, then a gradual decline in meteor number till the end of the cycle. The last such peak year was in 1998.
Follow Sciency Thoughts on Facebook. | 0.87252 | 3.708136 |
A team led by a researcher at the IAC and the University of La Laguna (ULL) has accurately measured the variation of oxygen abundance along the disc of our Galaxy.
During the Big Bang, which gave rise to our universe, only two chemical elements were formed in significant quantities, hydrogen and helium. Almost all the other elements, except those elements created by human beings, are produced in the stars during their lives and in processes associated with their deaths. In Astrophysics, the elements which are heavier than hydrogen and helium are called, generically, “metals” and the proportion of these elements in a cosmic object is termed its “metallicity”, whose average value has been growing continually with time within the galaxies. Among these “metals”, oxygen is the most abundant, and is therefore used widely as an index to estimate metallicities in general.
All spiral galaxies, such as the Milky Way, show a quantity of oxygen which falls off as we go further away from the galactic centre, and this is termed the “oxygen abundance gradient”. This behavior can be explained in terms of a number of different factors, firstly by the radial flows of gas within a galaxy disc, and secondly by the subsequent formation of stars. Almost 30 years ago indications were found that the slope of this gradient seemed to flatten in the outer reaches of the Milky Way, out beyond the “isophotal radius” which is at 37,500 light years from the Galactic centre. Until now, this supposed flattening did not have firm observational proof, because the ionized nebulae associated with star formation (so-called “HII regions”), which are the objects best suited for measuring the oxygen abundance, are very faint and difficult to observe in these distant regions.
However, thanks mainly to the OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) at the Roque de los Muchachos Observatory (Garafía, La Palma), a research team from the IAC and the University of Hong Kong has been able to make precise measurements of the temperature in the nebulae in these external regions for the first time, and to determine the oxygen abundance. Their results, recently published in the journal Monthly Notices of the Royal Astronomical Society, show that this flattening does not exist, and that the gradient of oxygen is practically constant out to 55,500 light years from the centre of the Milky Way, a considerable fraction of the disc, which reaches out to a radius of some 70,000 light years.
“If the oxygen gradient in the outer zones of the disc of the galaxy presented a flattening -says César Esteban, professor at the University of La Laguna (ULL), researcher at the IAC and the first author of this study- it would mean that some complex and exotic mechanisms would be acting in these distant zones. For example, if the star formation efficiency remained constant, or the processes of radial mixing of gas were unusually efficient. Our results suggest that we can be calm about this, nothing strange appears to be occurring in the outskirts of the Milky Way”.
Jorge García Rojas, an IAC researcher and another of the authors of the article, explains that “the results we have obtained indicated that the mechanisms which govern star formation and chemical evolution in the Milky Way do not change significantly according to radial position in the Galaxy disc”.
To obtain detailed spectra which allow to determine the temperature of the ionized gas of the nebulae, it has been essential to use large telescopes such as the GTC, of 10.4m, or the Very Large Telescope (VLT), a system of four 8.2m telescopes at the La Silla Observatory in Chile, belonging to the European Southern Observatory (ESO). “Until now -suggests Xuan Fang, researcher at the University of Hong Kong, who also participated in this study- we had spectra obtained with telescopes considerably smaller, and many of the chemical abundance determinations were indirect, without sufficient accuracy to establish the behavior we have found without the shadow of a doubt”.
“These results show that the most widely accepted models for the formation and evolution of the Milky Way, those referred to as “inside out”, can be applied to at least the greater part of the galactic disc” concludes one of those responsible for the research, Laura Toribio, who recently obtained her doctorate at the IAC.
Article: “The radial abundance gradient of oxygen towards the Galactic anticentre”/, por C. Esteban, X. Fang, J. García-Rojas and L. Toribio san Cipriano, Monthly Notices of the Royal Astronomical Society.
Article in astro-ph: https://arxiv.org/pdf/1706.07727.pdf
Artículo en Royal Astronomical Society: https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stx1624 | 0.869069 | 4.135201 |
ORBITAL ANALYSIS AND OBSERVATIONS OF PLANET X
For those of you who've been following and supporting our work at yowusa.com over the years, this is the video you've been waiting for. In this video, we're going to view some very compelling images of two objects within the Planet X system. The brown dwarf at its core and one of it's outmost orbitals, we call Bluebonnet.
Here is what our findings shows.
Current: PX System is presently inbound from beyond the orbit of Saturn in conjunction with us (opposite side of the sun beyond Earth's orbit.)
Late 2013 to early 2014: The brown dwarf will be in a superior conjunction (opposite side of the sun inside Earth's orbit.) Around this time, the brown dwarf will be passing through the ecliptic into the Northern skies. This is when it will begin have more severe interactions with our Sun. We'll see solar storms and a big increase in volcanism and seismicity.
2015 to 2016: We'll see Bluebonnet (the outermost orbital we've tracked from the Turrialba volcan feed, with hundreds of images.) Shortly after that, the Brown Dwarf will move around to our side of the sun to it's point of perihelion (closest distance to the Sun) to the Greatest-western elongation (our side of the sun, inside our orbit to our right.) At this time, the brown dwarf will enter the kill zone.
Early Kill Zone: The Kill Zone is that part of the brown dwarf's orbit from perihelion to the ecliptic (the plane of our solar system.) This will be when we see solar storms of Biblical proportions.
Late Kill Zone: The Planet X system will exit our system through the Western-quadrature (our side of the side, exiting behind Earth's orbit) as it crosses the ecliptic from the Northern skies into the Southern skies. This is when the pole shift will be most likely as this is when the brown dwarf will lock on to our lithosphere (crust and the portion of the upper mantle) and where it's tidal gravity forces cause the pole shift.
Post Kill Zone: Overall, this whole flyby could take as long as a decade from now to when we begin to see the first signs of blue skies once again. | 0.817004 | 3.374096 |
NASA's Stardust-NExT spacecraft is nearing a celestial date with comet Tempel 1 at approximately 8:37 p.m. PST (11:37 p.m. EST), on Feb. 14. The mission will allow scientists for the first time to look for changes on a comet's surface that occurred following an orbit around the sun.
The Stardust-NExT, or New Exploration of Tempel, spacecraft will take high-resolution images during the encounter, and attempt to measure the composition, distribution, and flux of dust emitted into the coma, or material surrounding the comet's nucleus. Data from the mission will provide important new information on how Jupiter-family comets evolved and formed.
The mission will expand the investigation of the comet initiated by NASA's Deep Impact mission. In July 2005, the Deep Impact spacecraft delivered an impactor to the surface of Tempel 1 to study its composition. The Stardust spacecraft may capture an image of the crater created by the impactor. This would be an added bonus to the huge amount of data that mission scientists expect to obtain. | 0.844836 | 3.041868 |
DAN DURDA'S RESEARCH INTERESTS
Airborne Observations of Planetary Occultations
Planetary occultations are a well-proven technique for measuring the sizes of solar system objects too small to be resolved in an angular sense and for obtaining pressure and temperature profiles of planetary atmospheres. Planetary occultations have been routiniely observed from groundbased sites for decades, and (in high-priority cases) by the NASA Kuiper Airborne Observatory (KAO) when it was operating. Unfortunately, many events are missed either because of bad weather or because they occur over water (which covers over 70% of the Earth's surface).
I am working with Alan Stern (SwRI) to develop techniques for, and to flight demonstrate the capability of, observing scientifically valuable planetary and asteroidal occultation events from high-performance NASA aircraft. This project utilizes the SWUIS-A instrument developed by our group and successfully flight-demonstrated aboard NASA WB-57 and F-18 aircraft flying out of JSC and DFRC. SWUIS (the Southwest Ultraviolet Imaging System) is an imaging telescope/camera system sensitive to mid-ultraviolet, visible, and near-infrared wavelengths that was developed as a mid-deck locker experiment aboard the Space Shuttle. SWUIS-A is a simpler, airborne version of the system now being developed to provide a low-cost, fast-response planetary occultation capability to the scientific community.
SWUIS-A consists of an image-intensified CCD camera with broadband response in the visible, accompanying high-quality foreoptics, a miniature video recorder, an aircraft-to-camera power and telemetry box with camera controls (called the PIB), and associated cables, filters, and other minor equipment. The primary SWUIS-A foreoptic is a high-quality, fixed focal length 85mm f/1.4 lens with a field-of-view of 8.7 deg. A 60-300 mm zoom lens, with a continuously-variable field-of-view capability from 13 to 3 deg is also flown. The SWUIS-A ICCD frames at video rates, which is a key requirement for both jitter compensation and the high time resolution needed for occultation studies. SWUIS-A image coadds can attain a limiting astronomical magnitude of V=10 in <1 sec with dark sky conditions.
Click here to read about the successful SWUIS-A mission to observe the 308 Polyxo occultation event the evening of 9 Jan 2000.
Experimental Study of the Impact Disruption of Meteoritic Samples
The collisional disruption of main-belt asteroids has been linked to the production of interplanetary dust particles (IDPs) by the discovery of the IRAS dust bands and their demonstrated association with major asteroid families. A detailed understanding of the dust production from the catastrophic disruption of asteroids and the subsequent comminution of their debris is therefore required to relate the chemical and mineralogical properties of IDPs collected at Earth to their parent bodies in the mainbelt.
George Flynn (SUNY-Plattsburgh) and I have begun a series of impact experiments to directly investigate the production of dust-size fragments in hypervelocity impacts. The goals of this research project are: (1) To determine the physical, chemical, and mineralogical properties of dust-size fragments from the impact disruption of meteorites. We will assess to what extent we can infer the bulk properties of the parent meteorites from analysis of the fragments. This will lead to a better understanding of the relationship of IDPs to their parent asteroids in the mainbelt. (2) To determine the size (and velocity) distribution of dust-size fragments from the impact disruption of meteorites. The results from the latest collisional models of main-belt evolution show that knowledge of the production function of the smallest particles is required to understand the collisional evolution of even the larger asteroids. (3) To quantify the fragmentation mechanics (size distribution of large fragments and target impact strengths) of actual meteoritic materials. This is a secondary objective of this research program, but is a natural by-product of the impact experiments and will provide valuable data that will be used to validate and constrain both hydrocode models of impacts into asteroidal materials and collisional models of the main-belt.
So far, we have conducted a set of impact experiments on terrestrial basalt as a feasibility study for the more detailed experiments involving actual meteorites. Using the NASA Ames Vertical Gun Range, we impacted three ~300 gram samples of porphyritic olivine basalt with ¼ inch aluminum spheres at speeds of ~5 km/s. The basalt was selected as a target because it exhibited two features similar to the carbonaceous chondrite meteorites: (1) it consists of large olivine phenocrysts, typically a few millimeters in size, in a weaker, fine-grained matrix, and, (2) it exhibits significant porosity, with observable vesicles. The results so far suggest that carbonaceous chondrite parent bodies might preferentially overproduce olivine-rich debris at the size scale of the chondrules and that olivine might be underrepresented in the debris at substantially smaller sizes. Our test experiments produced very useful data, demonstrated the validity of our approach, and clearly showed the need for further experiments with actual meteorites. Our experiments on meteorite samples (Allende and an ordinary chondrite) will begin in late 2001.
Click to see a QuickTime (555K) or mpeg (2534K) movie of one of our basalt targets being destroyed. The 500 frames/s video clearly shows the target disappearing in a cloud of cm- and mm-scale fragments and dust. The white squares behind and to the sides of the target rock (hanging from a black thread in the center of the experiment chamber) contain foil and aerogel detectors for analysing the size distribution of the dust-size fragments and their chemical and mineralogical properties.
Durda, D. D. and G. J. Flynn 1999. Experimental study of the impact disruption of a porous, inhomogeneous target. Icarus 142, 46-55.
Durda, D. D. and G. J. Flynn 1997. An experimental study of the impact disruption of a porous, inhomogeneous target. Lunar Plan. Sci. XXVIII, 313-314.
Durda, D. D. and G. J. Flynn 1997. Impact disruption of a porous, inhomogeneous target. Meteoritics & Planetary Science 32, A36-A37.
Searches for Vulcanoids
Interior to Mercury's orbit is a dynamically stable region where a population of small, asteroid-like bodies called Vulcanoids has been hypothesized to reside. The Vulcanoid Zone (VZ) extends inward from about 0.21 AU, a stability limit set by eccentricity perturbations due to Mercury and the other planets, to about 0.07 AU, where thermal conditions and dynamical transport mechanisms such as Poynting-Robertson (PR) drag and the Yarkovsky effect rapidly remove smaller objects. This putative reservoir plausibly contains a sample of condensed material from the early inner solar system, and bears additional relevance to our understanding of Mercury's cratering record.
Alan Stern (SwRI) and I have conducted numerical models of the collisional evolution of various-size populations of objects in this region that suggest that a modest population of km-scale or larger objects could have survived the harsh collisional environment in this region from primordial times to the present epoch. The most favorable locale for residual bodies to survive is in low eccentricity orbits near the outer edge of the dynamically stable zone (i.e., near 0.2 AU). Our results suggest that a population of a few hundred objects larger than ~2 km in diameter could presently exist in the VZ, with perhaps a few tens of such objects in the 0.01 AU-wide band near the outer stability boundary at 0.21 AU. Bill Bottke (SwRI) and collaborators examined the removal of Vulcanoids from this region through the Yarkovsky effect and reached a similar conclusion.
Although a modest population of Vulcanoids may well exist, they will be particular hard to detect, due to their angular proximity to the Sun and relative faintness against a twilight sky. Viewed from 1 AU, the inner and outer boundaries of the VZ correspond to maximum solar elongation angles of only 4 deg and 12 deg (15 and 45 solar radii), respectively. Consequently, only a few visible wavelength observational searches for Vulcanoids have been conducted, and these have been limited to relatively bright limiting magnitudes, corresponding to objects with diameters larger than ~20-60 km (assuming Mercury-like albedos and phase functions.
We recently completed a search for Vulcanoids in coronagraph images obtained by the Solar and Heliospheric Observer (SOHO) spacecraft. We recognized that SOHO's Large Angle Spectroscopic Coronagraph (LASCO) instrument, which has been routinely detecting sungrazing comets, provides an opportunity to explore the inner heliosphere to search for small bodies orbiting the Sun. We therefore examined a 40-day continuous sequence of white light images obtained by the LASCO C3 coronagraph to search for Vulcanoid candidates. Although we detected no Vulcanoids to a moving object detection limit of V=8 (20-60 km diameter objects), our search was far more comprehensive than past ground-based searches.
Future searches complete to magnitudes fainter than V=8.0 are required in order to place tighter constraints on the size of the Vulcanoid population. We are working to conduct a deeper and more extensive Vulcanoid search than has ever been made. The limitations that have plagued past ground-based visible-wavelength searches for Vulcanoids can be greatly alleviated by reducing or removing the various observing problems (clouds, variable hazes, turbulence, scattered light, high airmass, etc.) associated with the atmosphere. We are preparing to fly our SWUIS-A astronomical imaging system to altitudes over 70,000 feet aboard a USAF U-2 aircraft. From above more than 90% of the Earth's atmosphere, in deeper twilight than is ever possible from the ground for objects so close to the Sun, we will be able to detect Vulcanoids down to at least magnitude V = 12.5, corresponding to objects only 8 km across at the outer boundary of the Vulcanoid zone. This is at the location and in the size range where we predict that a sizable population of Vulcanoids is most likely to exist. Covering some 108 square degrees to limiting magnitude V = 12.5, this effort will result in the most comprehensive, constraining search yet conducted for these objects. The figure to the left illustrates the geometry of a search for Vulcanoids from high altitude at twilight near the equinox. As viewed from the southwest United States, the ecliptic is nearly vertical with respect to the horizon at the equinox. The outer limits of the Vulcanoid zone extend outward from the Sun to about 12 deg along the ecliptic. Our airborne search will cover over half of the Vulcanoid zone and beyond to ~15 deg solar elongation and out to 6 deg north and south of the ecliptic.
Durda, D. D., S. A. Stern, W. B. Colwell, J. Wm. Parker, H. F. Levison, and D. M. Hassler 2000. A new observational search for Vulcanoids in SOHO/LASCO Coronagraph Images. Icarus 148, 312-315.
Stern, S. A. and D. D. Durda 2000. Collisional evolution in the Vulcanoid region: Implications for present-day population constraints. Icarus 143, 360-370.
Durda, D. D., S. A. Stern, J. Wm. Parker, W. B. Colwell, H. F. Levison, D. M. Hassler, and D. C. Slater 1999. Collisional and observational constraints on the putative Vulcanoid population. Bull. Amer. Astron. Soc. 31, 1118.
The Global Distribution of Ejecta from the Chicxulub Impact Crater
65 million years ago a 10 km diameter asteroid or comet slammed into the Earth near what today is the Yucatan Peninsula. 75% of all the species alive at the time, including the dinosaurs, became extinct as a result of a number of complexly interacting environmental and ecological perturbations caused by the impact. Ejecta from the impact forms a boundary sequence (the K/T boundary) composed of two macroscopic layers in North America and a single layer in the eastern hemisphere. The lower layer in (and adjacent to) North America is interpreted to be relatively low-energy ejecta deposited from the crater's ejecta curtain, while the upper layer is derived from higher energy ejecta carried in a vapor plume that rose far above Earth's atmosphere and distributed material globally. Unfortunately, we still do not understand the details of these processes, even though many post-impact environmental effects depend on the mass distribution in each of these ejecta units and the timescales over which they were deposited.
To examine the trajectories of material in the vapor plume and the ejecta curtain and the effects the ejecta might have on the post-impact environment, David Kring (LPL) and I constructed a computer simulation of the launch and deposition of the low- and high-energy ejecta. The low-energy ejecta is distributed more or less symmetrically around the impact site and is concentrated within about 1000 km of Chicxulub. The high-energy ejecta is distributed globally, although it is concentrated near the antipode, where the sub-continent of India was located 65 million years ago. Most of the high-energy ejecta stays within 50,000 km of Earth, with several percent reaching 100,000 km or more, before reentering the atmosphere. Approximately 25% of the material reaccretes within 2 hrs, ~50% within 8 hrs, and ~75% within ~72 hrs. We also found that at least 20-30% of the ejected material escapes, even when we make the very conservative assumption that the speeds of materials in the vapor plume are <11.2 km/s (Earth's escape speed). This is due to the effect of the Earth's rotation, which adds 0.4-0.5 km/s to material launched in the same direction as Earth's rotation. In reality, some material will be launched at greater than escape speed, so that the fraction of material lost from Earth will actually be greater than 20-30%.
These results lead to some potentially useful conclusions about the post-impact environment. In either a vertical or oblique impact event, the amount of heating in the upper atmosphere by reaccreting high-energy ejecta may be greatest at the antipode and above the impact site, although a time-intregrated series of calculations is needed to accurately determine the magnitude of this effect. Nonetheless, this could be an important factor when calculating post-impact chemical reactions in the stratosphere and on the possibility of the ignition of fires on the surface.
Durda, D. D., D. A. Kring, E. Pierazzo, and H. J. Melosh 1997. Model calculations of the proximal and globally distributed distal ejecta from the Chicxulub impact crater. Lunar Plan. Sci. XXVIII, 315-316.
Kring, D. A., and D. D. Durda 2001. The distribution of wildfires ignited by high-energy ejecta from the Chicxulub impact event. Lunar Plan. Sci. XXXII, abstract no. 1447.
The Formation of Asteroidal Satellites
The discovery of Dactyl, the small satellite of the asteroid 243 Ida, has revived interest in how such satellites might be formed. There are several ways to make asteroidal satellites and all involve collisions of one sort or another:
In 1979, William K. Hartmann suggested that a catastrophic collision between two asteroids
might result in the ejection of some fragments with very similar velocities
resulting in mutual capture into gravitationally bound pairs (left) or in extremely low-speed collisions forming contact binaries (lower right).
The results of my numerical models show that asteroidal satellites are indeed a natural outcome of catastrophic collisions. A small fraction of the fragments of the parent asteroid end up in gravitationally bound pairs, either orbiting each other or in contact configurations.
Another possible mechanism for forming small satellites about asteroids is through the mutual reaccretion of ejecta from large cratering impacts on the primary. In the absence of collisions or other perturbing forces, a particle ejected from the surface of a rapidly rotating, irregularly shaped asteroid will eventually re-impact the primary if it does not escape the system altogether. A small satellite cannot then be formed simply by launching a large ejecta block directly into orbit. However, numerical integrations of the trajectories of impact ejecta around 243 Ida show that many debris particles can temporarily co-exist in complex orbits about the primary, offering the possibility that a fraction of the crater ejecta might collide and mutually reaccrete in orbit.
Paul Geissler (LPL) and I examined the accretion of ejecta particles from three craters on Ida: Azzurra (Lat +30, Long 220), Undara (Lat 0, Long 120), and a hypothetical crater located at the north pole of the asteroid. In each case we assumed a crater diameter of 10 km, and followed the evolution of 1000 ejecta particles (each 68 meters in diameter) for 100 hours after the cratering impact. In order to increase the probability of inter-particle collisions for so few particles, the particle sizes were increased by a factor of 3 and the resulting accretion statistics normalized accordingly. Our most significant results from this ongoing study so far are:
(1) The formation of asteroidal satellites by accretion of cratering debris is inefficient at best. Although accretion events do regularly occur, we have not yet seen the formation of accreted particles in stable orbits. Our model results indicate that in the first 100 hours following a large cratering collision, up to 0.1% of the ejected debris will have accreted while in flight around the primary. (For comparison, the formation of Dactyl would require the accretion of roughly 3% of the ejecta from a 10km diameter crater on Ida.) 80-90% of these accreted particles eventually re-impact Ida, with the remainder escaping the system altogether (we see essentially the same behavior for indiviudual ejecta particles).
(2) There is a very strong selection for accretion of particles on trajectories with inclinations resembling that of Dactyl: For debris accreted from the craters Azzurra and Undara, the majority of accreted particles are formed in prograde orbits nearly coincident with Ida's equatorial plane. This can be understood when we realize that the vast majority of ejecta launched initially in the direction opposite the primary's sense of rotation rapidly re-impact the surface of the asteroid. Only those particles launched in the direction of rotation are lofted on trajectories high enough to allow sufficient time for there to be a significant probability of encountering other particles.
(3) The location of the source crater appears to be significant in affecting not only the efficiency of the ccretion process, but also the distribution of orbital elements for the accreted particles. Only 0.007% of ejecta accreted from a hypothetical crater at Ida's north pole; accretion of debris from craters nearer the equator is observed to be as much as 15 times more efficient. As might be expected by symmetry, there are no prefered inclinations from debris originating from polar craters.
Durda, D. D. 1996. The formation of asteroidal satellites in catastrophic collisions. Icarus 120, 212-219.
Durda, D. D. 1994. Numerical models of the origin of asteroidal moons during Hirayama family formation. Bull. Amer. Astron. Soc. 26, 1158.
Durda, D. D. and P. E. Geissler 1996. The formation of asteroidal satellites in large cratering collisions. Bull. Amer. Astron. Soc. 28, 1101.
Ejecta Accretion on Irregular, Rapidly Rotating Asteroids
Because of their low gravities, asteroids represent a valuable and previously inaccessible laboratory for the study of space erosion and the mechanics of impact cratering. The non-spherical shapes and rapid rotation of many asteroids produce interesting dynamical environments in which marked non-uniformities of soil thickness can be expected to occur. Careful study of the characteristics and spatial distribution of regolith on such a body may provide important insights about the nature and physical properties of the asteroid, its collisional and erosional history, the population of impactors which crater its surface, and the details of impact cratering in a low-gravity regime.
Each of the asteroid-like objects so far imaged by spacecraft has shown substantial evidence for the presence of regolith. Direct indications include high resolution imaging observations of the Martian moons Phobos and Deimos and the main-belt S-type asteroid 243 Ida, all of which have large (up to 150 m diameter) angular blocks on their surfaces. These are presumed to be fragments of impact ejecta, and thus represent the coarsest size fraction of impact-generated soil on these small object. Indications of mass-wasting or landslides have been interpreted on Deimos and Ida, suggesting regolith accumulation on slopes beyond the angle of repose. Although the lower resolution images of Gaspra preclude similar such direct observations, many lines of evidence such as the subtle color differences between ridges and topographic lows are suggestive of regolith development on this S-type asteroid as well.
The existence of soil on the smallest solar system bodies supports the view that a substantial fraction of the ejecta from impact events on small bodies may be retained. At present, predictions of ejecta velocities and regolith retention rates are derived largely from extrapolating observations made under very different circumstances. The nature of cratering in low-gravity environments like the surfaces of small asteroids is largely unknown. Spacecraft imaging of the distribution of regolith on asteroids provides an important opportunity to obtain direct measurements of impact ejecta velocities on such small bodies.
Geissler, P., J.-M. Petit, D. D. Durda, R. Greenberg, W. Bottke, M. Nolan, and J. Moore 1996. Erosion and ejecta reaccretion on 243 Ida and its moon. Icarus 120, 140-157.
Geissler, P. E., D. D. Durda, J. Plassmann, T. Hurford, and R. Greenberg 1996. Generation of regolith on 243 Ida. Bull. Amer. Astron. Soc. 28, 1102-1103.
Geissler, P. E., J.-M. Petit, D. D. Durda, R. Greenberg, W. Bottke, M. Nolan, and J. Moore 1995. Ejecta reaccretion on 243 Ida. Bull. Amer. Astron. Soc. 27, 1070.
The Collisional and Dynamical Evolution of Asteroids
The size distribution of the main-belt asteroids provides a strong constraint on models of the collisional history of the asteroid belt. The most important factor in determining the shape of the evolved size distribution is the dependence of the critical specific energy on target size. The critical specific energy, Q*, is the energy per unit target mass required to fragment and disrupt a target asteroid, leaving a largest remnant with 50% the mass of the original target.
A number of studies have focused on determining how Q* varies with the size of the target asteroid. Treatments of the size dependence of Q* have generally been considered in two separate regimes: the strength-scaling regime, where the response of small targets to catastrophic impacts is governed by material strength and Q* decreases with increasing target size, and the gravity-scaling regime, where the outcome of collisions is dominated by gravitational effects and Q* increases with increasing asteroid size. Considerable uncertainty remains in the precise size dependence of Q* in the two scaling regimes as well as the size at which gravitational effects begin to dominate over inherent material strength.
Rick Greenberg (LPL), Robert Jedicke (LPL), and I explored an alternative means of determining the size-strength scaling relation for asteroidal bodies. We utilized the fact that the detailed dependence of Q* on target size translates directly into observational features in the evolved size distribution. I showed in my Ph.D. thesis that the power-law index of a collisionally evolved population is linearly dependent upon the slope index of the size-strength scaling relation and that abrupt changes in the size dependence of Q* can result in distinct kinks or humps in the size distribution. Given that the evolved size distributions generated by collisional models depend strongly (and understandably) upon the shape of the size-strength scaling law, we least-squares adjust the strength law for asteroidal bodies to obtain a best fit to the actual asteroid size distribution determined from the catalogued asteroids and Spacewatch data. A successful match would be strong evidence that the corresponding size-strength scaling law is a good representation of the actual behavior of asteroids in catastrophic collisions.
Our results show for the first time general agreement between the predictions of hydrocode models, the results of numerical collisional models, and the observed asteroid size distribution, and lead to a new interpretation of the shape of the main-belt asteroid size distribution. We find a strength scaling law which, when used within our numerical collisional model, gives good agreement with the two-hump structure observed in the actual size distribution of main-belt asteroids. The hump in the size distribution between ~3-30 km is a primary hump due to the transition from strength scaling to gravity scaling for asteroids larger than ~150 m. The well-known hump observed in the asteroid size distribution at ~50-200 km is a secondary hump resulting from wave-like structure induced in the size distribution by the ~3-30 km primary hump.
Combined with results of continued laboratory impact experiments and further refinements to hydrocode our results should lead to a better understanding of the physical structure of asteroids of all sizes.
Durda, D. D., R. Greenberg, and R. Jedicke 1998. Collisional Models and scaling laws: A new interpretation of the shape of the main-belt asteroid size distribution. Icarus 135, 431-440.
Durda, D. D., R. Greenberg, and R. Jedicke 1998. A new interpretation of the size distribution of main-belt asteroids. Lunar Plan. Sci. XXIX, abstract no. 1680.
Durda, D. D. and S. F. Dermott 1997. The collisional evolution of the asteroid belt and its contribution to the zodiacal cloud. Icarus 130, 140-164.
Durda, D. D. and S. F. Dermott 1996. Size distributions of asteroidal dust: Possible constraints on impact strengths. In Physics, Chemistry, and Dynamics of Interplanetary Dust. ASP Conference Series, Vol. 140 (B. A. S. Gustafson and M. S. Hanner, Eds.), pp. 473-476. Astronomical Society of the Pacific, San Francisco. | 0.8815 | 3.300007 |
(CNN) — Even in a country of impossibly great distances, Sossusvlei is remote.
With its red sand dunes and white salt pans, Namibia's southern Namib Desert looks so Martian that it wouldn't come as a shock if the Curiosity Rover rumbled over a dune and frightened a herd of oryx.
They're among the few animals that survive in a place whose name means "marsh of no return."
But then not many people come here for the wildlife.
This is a place where people come for the stars.
Dark Sky Reserve
It's so far from any human center that the light pollution is non-existent, meaning the night skies are among the darkest on Earth.
The International Dark-Sky Association, the go-to authority on light pollution, has certified the region as one of its Dark Sky Reserves because of the spectacular starry night.
What's most amazing about a sky so dark is how bright it actually is.
The Milky Way stretches overhead, with the Magellanic Clouds in bursts of light to the side.
Familiar constellations of the southern skies suddenly have millions of neighbors.
These groupings are normally invisible even from small towns.
This is how humans saw the sky for thousands of years.
If you're not okay with small planes, you're better off driving from Windhoek.
There are only two ways of getting to the Sossusvlei clay and salt pans: either a six-hour drive from Windhoek, mostly along an unpaved road, or with a flight on a six-seater plane that lands on a gravel airstrip.
On a hill above the dining area, an observatory hosts a 12-inch telescope, with a resident astronomer to navigate the sky.
"With the telescope, we start by showing the bright planets and the moon when they are visible, and our close neighbor star, the double star Alpha Centauri," said andBeyond CEO Joss Kent.
"Then we look at some of the bright, very well-known objects in the far southern sky."
The neighborhood star factory
With the telescope, familiar objects become less so.
Within the Southern Cross is the Jewel Box, which looks like a star to the naked eye but is actually a cluster of stars with an orange supergiant surrounded by cooler blue neighbors.
In the Large Magellanic Cloud, the Tarantula Nebula was also once thought to be a star.
It's actually a spidery cloud of dust and gas, and one of the biggest star factories in our galactic neighborhood.
Inside are some of the biggest and brightest stars ever discovered.
Closer to home, the 12-inch Meade LX200 telescope shows the rings of Saturn and the moons of Jupiter.
With an astronomer to guide the stargazing, it's easy to spend hours looking at the sky, peering at even faint objects like planetary nebulae and galaxies up to 60 million light years away.
The telescope is computerized with tracking software, so it can hone in on distant objects with remarkable ease.
Sleeping beneath the stars
The lodge has a resident astronomer to help you sort your Ursa Majors from your Ursa Minors.
To get certified as an International Dark Sky Reserve, the lodge had to remove many outside lights.
Paths to the guest rooms are lit with red energy-saver bulbs that help with night vision.
And once in bed, a skylight opens overhead so guests fall asleep under the stars.
During the day, Namibia's iconic sand dunes are an hour's drive away.
NamibRand is a private reserve, and the dunes are inside the adjacent Namib-Naukluft National Park.
In the morning the crowds wait at the gate, but they're only crowds in the Namibian sense.
This is one of the world's least populated countries (only Mongolia has fewer people per square mile) so traffic out here is maybe a dozen other vehicles.
Still, that makes for a small parade of people hiking up the dunes -- although the word "dunes" doesn't quite do them justice.
These aren't rolling mounds on the beach suitable for buggies.
These are small mountains of red sand, up to 400 meters high, with a sharp ridge formed by the wind that makes for the easiest ascent.
600-year-old petrified trees
Farther along is Deadvlei (vlei is a marsh in Afrikaans), a suitably creepy expanse of salt pans studded with dead trees.
Not petrified trees, but 600-year-old dead trees scorched black by the sun.
The desert is so dry, they simply haven't decomposed.
Few animals brave these conditions, but there are new things still being discovered.
Miles Paul, one of the astronomers, discovered a new species of gecko in 2011 while on a hike.
It was named Pachydactylus etultra, for "andBeyond" in Latin.
The area around the lodge is still the only place it's ever been found. | 0.846247 | 3.25069 |
|Voyager Probes Exiting Solar System into Interstellar Space Reveals Sun's Protective Shield|
JUNE 14th 2012--"Data from NASA's Voyager 1 spacecraft indicate that the venerable deep-space explorer has encountered a region in space where the intensity of charged particles from beyond our solar system has markedly increased." Nasa.gov
Voyager: From 1977 til now, has been flying at about 38,000 mph toward the exit of our Solar System. 35 years ago this primitive probe was launched and has traveled 11.1 billion miles approximately, which is only about 1/1000th of a light year. In all this time it has been measuring, photographing, and doing its "business" for NASA, and has won the hearts of Americans for decades. No scientist could have ever hoped it would live this long, and apparently it is doing fine, that is, until it does actually leave the Solar System. This is mostly because the probe has been power all this time by the Sun's rays through unique solar panels and plutonium. It was a veritable rechargeable probe like those fancy batteries you love so much. Once it leaves the Solar System, it should not take long to run out of power, sadly, and also will lose its signal for reasons listed below.
The Sun shields the entire Solar System very well indeed, however this boundary, called the Heliosheath, also causes extreme signal interference, which means that when Voyager exits this boundary the signal from Earth will be cut off soon after, if not immediately. Voyager will run out of power, go silent to us, and drift in the heavens for decades or more until it hits something. Space is large and frictionless, so it could be a very, very long time before this 38,000 mph probe even slows down or crashes, or it could be very soon.
The reason I say this is because Voyager has detected massive increases in charged particles just outside of our Solar System! In fact, the magnetic forces, deadly cosmic rays, and charged particles have increased over 25% thus far, and are averaging ~5% increases per week. The increases are increasing too as the Voyagers continue through this boundary. The chances seem fairly high that interstellar space is far more deadly than astronomers may have anticipated, and although they knew space would be harsh, most scientists thought it was mostly empty. In all the articles I've read to date, astronomers were still quite surprised with the sudden large increases in these ionic forces. The chances are high that space itself is a playground for all sorts of deadly and chaotic forces, as the chances between exploding or not exploding are as good as 50-50 out there and seem virtually unpredictable. It is in this medium that stars are born, after all. Stars aren't born in friendly environments, duhh, as they are extremely hot and explosive, with their supernovae immediately destroying all things within 200 light years distance. Some articles, like this one, describe how our Sun prevents the Earth from being destroyed utterly, and even predict that when our Sun begins to weaken and die, the Earth will actually die long before the Sun goes dark because this protective shield it casts will fray, allowing these deadly interstellar forces to reach Earth, destroying all life. So don't worry young ones, we will not die of cold or in darkness, but rather in skin scorching, eye blistering radiation and brain fraying magnetic forces...yay...?
I would not be half surprised if Voyager's data indicate that even exiting our Solar System at all would be a suicide mission. I stand ready to read articles with funny titles like "Voyager Explodes in Interstellar Space" and the like. As it stands, these rays and particles would annihilate Earth without our Sun, so how can we expect to travel through these forces at millions of miles per hour for decades and centuries on end to explore the universe and colonize other planets not in their own systems like ours? We could find the perfect planet, but the deadly space forces would kill us if we tried to colonize it. Uhg.
--Einstein didn't think it was at all possible to space travel, but then again, what did Einstein know anyway?? (everything) | 0.869105 | 3.530975 |
The term "Planet X" has a variety of meanings and uses. After the discovery of Neptune, Percival Lowell "proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities."
Today, the astronomical community widely agrees that Planet X, as originally envisioned, does not exist, but the concept of Planet X has been revived by a number of astronomers to explain other anomalies observed in the outer Solar System. In popular culture, and even among some astronomers, Planet X became a stand-in term for any undiscovered planet in the outer Solar System, regardless of its relationship to Lowell's hypothesis.This week, good evidence was reported for the existence of such a previously-undiscovered planet. I've seen it referred to as Planet X or as Planet IX.
The embedded video gives a broad overview. This article in Science provides more details. Even more amazing than the existence of the planet is its extraordinary orbit:
In the schematic, the entire known solar system is represented by the small blue circle in the center (magnified in an offset in the upper part of the image).
The orbit of the inferred planet is similarly tilted, as well as stretched to distances that will explode previous conceptions of the solar system. Its closest approach to the sun is seven times farther than Neptune, or 200 astronomical units (AUs). (An AU is the distance between Earth and the sun, about 150 million kilometers.) And Planet X could roam as far as 600 to 1200 AU, well beyond the Kuiper belt, the region of small icy worlds that begins at Neptune’s edge about 30 AU.Mind-boggingly awesome. | 0.806537 | 3.33909 |
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The flashcards below were created by user
on FreezingBlue Flashcards.
• Linear size = how big something really is– Meters, inches, light years, feet• Angular size = how big something looks– Degrees, arcminutes, arcseconds, milliarcsecondsCircle = 360 degrees1 degree = 60 arcmin1 arcmin = 60 arcsec1 arcsec = 1000 mas
- can appear big or
- small in the sky because they are really big or small or because they are
- very close or far away
- 2x distance = ½ as big, 10x distance = 1/10 as
Distances in the Solar System
- • Can use angular size to find distances to planets• Transits of Venus and Mercury• Can also bounce radar waves off planets to find distance
- – Example: Laser measurements indicate the averagedistance to the Moon is 385,000 kilometers (+- 3 cm!)Distances in solar system often measured inAstronomical Units – average distance fromEarth-Sun150 million km or 93 million milesJupiter – 5 AU from Sun, Pluto – 40 AU
Distances to the Stars
One proof of a heliocentricUniverse is stellar parallax.– Greeks, Tycho Brahe saw no parallax.– Copernicus: stars too far away.• Nearest star: Proxima Centauri– Parallax angle = 0.76 arcsec– Tycho’s precision = 1 arcmin
• What is the distance of anobject with a parallax angle of1 arcsec?Distance = 206,265 AU• This distance is 1 parsec (pc)1 pc = 206,265 AU = 3.26 ly• 1 lightyear = distance light travels inone year.
Distance (in parsecs) = 1 / parallax (in arcsec)
If Star A has a parallax of 2 arcseconds, and StarB has a parallax of 0.25 arcseconds:
a. Star A is closer to us than Star B. Both are fartherfrom us than 1 pc.
b. Star A is closer to us than Star B. Both are closer to usthan 1 pc.
c. Star A is closer to us than 1 pc. Star B is farther than 1pc.
d. Star B is closer to us than 1 pc. Star A is farther than 1pc.
e. Star B is closer to us than Star A. Both are fartheraway than 1 pc.
• How bright arethey really?• What is due todistance?• What is due toluminosity?• Luminosity:– Total energyradiated everysecond.
Brightness = Howintense is the light Isee from where I am.– Magnitude is thetechnical term for this.• Luminosity = howmuch light is the thingreally giving off.
Brightness vs. Distance
• Inverse square lawBrightness = 1/distance22x distance = ¼ as brightWhat is the brightness at10x distance?Size and distance?How much smaller does object appear at 10x distance?
• The SMALLER thenumber the BRIGHTERthe star!– Every difference of 1magnitude = 2.5x brighter ordimmer.– Difference of 2 magnitudes= 2.5x2.5 = 6.25x brighter ordimmer
Star light, starbright
Sirius is magnitude -1.5Polaris is magnitude 2.5• Is Sirius really moreluminous than Polaris?• Not necessarily, Sirius isjust closer.• Example: light bulbs.
Magnitude and Brightness
• Apparent magnitude - how bright a star appearsto be from Earth; mv• Absolute magnitude - intrinsic luminosity of astar; Mv– brightness at a given distance(10 pc = 32.6 light years)– Difference between apparent and absolutemagnitude can give you distance to star
Apparent and Absolute
Apparent Magnitude = brightness (magnitude) of astar as seen from Earth. m– Depends on star’s total energy radiated (Luminosity) anddistance• Absolute Magnitude = brightness (magnitude) of astar as seen from a distance of 10 pc. M– Only depends on a star’s luminosity
Cepheid variables – pulsating starsthese stars change brightness over time in aregular way – can be used to find distance
Period of pulsation related to luminosity: the longer the period, the brighter the star
How Big Are Stars?
-We can’t see the stars’diameters through a telescope.Stars are so far away that wesee them just as points of light.
- If we know a star’s temperature and its luminosity,we can calculate its diameter.
- -Luminosity depends on….
- TEMPERATURE -the hotter a star is,the brighter it is.DIAMETER –the bigger a star is,the brighter it is.Stars range in size from about the size of the Earth tohundreds of times the Sun’s diameter
We see stars have differentluminosities and differenttemperatures.• Stars have different sizes.• If you know a star’s– Distance– Angular size• You can find its real size.
How hot are stars?• Thermal radiationand temperature.• Different starshave differentcolors, differentstars aretemperatures.• Different temp,different tracecompositions
The Composition of Stars
90% hydrogen atoms10% helium atomsLess than 1%everything else(and everythingelse is made in stars!)
Everything comes from the Stars
Elements that make up the human body are mostly carbon, hydrogen,oxygen (hydrocarbons) and calcium.• Trace amounts of sodium, potassium play a crucial role in the process ofhuman thought.• Food is mostly also C, H, O and trace amounts of heavy elements (zinc isused to grow pineapples!).• The air we need to breathe is oxygen and nitrogen.• Most of what we use for living is also C, H, O, and metals like iron,aluminum, etc.• Let’s not forget silicon. It makes beaches, glass, and email possible
Abundance of Elements in the Sun
Chemical elements arecreated• in the EarlyUniverse• in Stars• in Supernovae• The Galaxy is enrichedin chemical elementsthrough interstell
- How do you weigh a star?• Kepler’s Laws – devised for the planets.• Apply to any object that orbits another object.• Kepler’s Third Law relates:– Period: “how long it takes to orbit something”– Semimajor axis: “how far you are away from that something”– Mass: “how much gravity is pulling you around in orbit”• Where M is the Total Mass.• Can calculate the mass of stars this way.
- period squared = distance cubed / mass
Most stars in the skyare in multiplesystems.• Binaries, triplets,quadruplets, etc….– Sirius– Alcor and Mizar– Tatooine• The Sun is in theminority by beingsingle.
You can watch how stars go around each other and figure out theirmasses from Kepler’s third law
Masses of Stars
- The more massive the star, the more luminous it is.The more massive the
- star, the hotter it is.• Between 1/100th and 100x the mass of the Sun•
- Smallest stars: brown dwarfs, too small for fusion tohappen – just a
- “dull glow”Gliese 623b:1/10 mass of Sun,60,000x fainterJust barely a
Most stars aroundthe sun aredimmer…
And smaller than thesun… | 0.86399 | 3.157783 |
The San Andreas fault is so sensitive that gravitational pull from the moon and sun is causing continual tremors deep underground.
"Tremors seem to be extremely sensitive to minute stress changes," said Roland Bürgmann, UC Berkeley professor of earth and planetary science. "Seismic waves from the other side of the planet triggered tremors on the Cascadia subduction zone off the coast of Washington state after the Sumatra earthquake last year, while the Denali earthquake in 2002 triggered tremors on a number of faults in California. Now we also see that tides – the daily lunar and solar tides – very strongly modulate tremors."
The team reckons that the fault's extreme sensitivity to stress – and specifically to shearing stress along the fault – means that the water deep underground it is under extreme pressure.
"The big finding is that there is very high fluid pressure down there, that is, lithostatic pressure, which means pressure equivalent to the load of all rock above it, 15 to 30 kilometers of rock," said seismologist Robert Nadeau of the Berkeley Seismological Laboratory. "Water under very high pressure essentially lubricates the rock, making the fault very weak."
"These tremors represent slip along the fault 25 kilometers underground, and this slip should push the fault zone above in a similar pattern," Bürgmann said. "But it seems like it must be very subtle, because we actually don't see a tidal signal in regular earthquakes. Even though the earthquake zone also sees the tidal stress and also feels the added periodic behavior of the tremor below, they don't seem to be very bothered."
Nevertheless, said Nadeau, "It is certainly in the realm of reasonable conjecture that tremors are stressing the fault zone above it. The deep San Andreas Fault is moving faster when tremors are more active, presumably stressing the seismogenic zone, loading the fault a little bit faster. And that may have a relationship to stimulating earthquake activity."
To learn more about the source of the tremors, the teamcorrelated eight years' worth of tremor activity with the effects of the sun and moon on the crust and with the effects of ocean tides.
They found the strongest effect when the pull on the Earth from the sun and moon sheared the fault in the direction it normally breaks.
"When shear stress on a plane parallel to the San Andreas Fault most encourages slipping in its normal slip direction is when we see the maximum tremor rate," Bürgmann said. "The stress is many, many orders of magnitude less than the pressure down there, which was really, really surprising. You essentially could push it with your hand and it would move."
It may be that tremors only occur on faults where fluid is trapped deep underground with no cracks or fractures allowing it to squirt away, Nadeau added. That may explain why tremors are not observed on other faults, despite intense searching.
"There is still all lot to learn about tremor and earthquakes in fault zones," he said. "The fact that we find tremors adjacent to a locked fault, like the one at Parkfield, makes you think there are some more important relationships going on here, and we need to study it more."
The paper appears in Nature. | 0.882128 | 3.587622 |
Mon, 20 Mar 2017
A comet crosses the Plough
Comet 41P photographed with a 300 mm lens on 20 March.
Photo: Stuart Atkinson
A periodic comet is about to move fairly close to the Earth, and will be visible for those with good skies in one of the most easily recognised parts of the sky – The Plough (or Big Dipper for American readers). But Comet 41P/Tuttle-Giacobini-Kresak (let’s call it 41P from now on) isn’t one of those eyeball-searing bright comets we all look forward to. Instead, it is a fairly small run-of-the-mill comet that will take a little finding with binoculars or a telescope.
The comet itself was discovered as long ago as 1868 by Horace Tuttle, but was twice lost and then found again after long intervals by Giacobini and Kresak, hence its triple-barrelled name. It is in an orbit that takes it out just beyond the orbit of Jupiter and then brings it in to just beyond Earth’s orbit. It so happens that this year the Earth is in a good position to see its closest approach to the Sun, as the diagram here from JPL shows (click to enlarge). Even at its closest, on 1 April would you believe, it will be far too distant to affect Earth (despite what you might read on some websites where fake news gets clicks).
You can see 41P for yourself by using our map of Ursa Major (below). Click for a much larger version that shows stars down to magnitude 8, produced using SkyMap. You’ll find the constellation fairly high up in the north-eastern part of the sky, with the handle of the Plough pointing downwards. You will need a good, clear sky as dark as you can get. City observers should head for a darker area if possible. At around magnitude 7.5 41P is comparatively bright, but the fuzzy nature of comets can make them tricky to see where there is light pollution. If you have a choice of binoculars, use higher rather than lower magnification. 10 x 50s might be good enough in a dark sky but 15 x 70s are preferable. This comet is more of a photographic than a visual target from the UK.
Observing from Portslade in Sussex on March 21, Mike Feist could just see the comet with averted vision using a 65 mm spotting scope x 31. This indicates that in most UK skies, the comet is currently a tricky object. However, during the first week in April it is predicted to be about half a magnitude brighter than at present.
Highlight of the event will come on 22 March when the comet passes close to two well-known features, the Owl Nebula (M97) and the galaxy M108. These can be seen in good skies with binoculars, but suitably equipped astrophotographers should be able to capture the image with a DSLR or CCD camera. Unfortunately for UK observers, the closest approach of the comet to M108 occurs at around 2 pm on the 22nd. However, the three objects will still be within close quarters on the morning or evening of the 22nd.
Comet 41P (lower right) with the star Merak (top), M97 and M108 (left), photographed with a 135 mm lens on March 20 by Stuart Atkinson. Click to enlarge.
Our Comet Section Director, Stuart Atkinson, has written a more detailed account of Comet 41P on our Facebook page. If you observe or photograph the comet, please do drop him a line at [email protected] to tell him what you saw.
Positions for comet 41P during March 2017. Click for a larger and more detailed version. Ticks are for 0h UT on the day in question, so bear in mind that in the evening the comet will be closer to the next day's tick.
Added by: Robin Scagell | 0.820267 | 3.615885 |
February 1, 2009
NASA Prepares Kepler For Launch
NASA on Friday showed off its new telescope aimed at determining if a habitable planet exists in other solar systems.
Set to launch aboard a United Launch Alliance Delta II rocket, the Kepler telescope is designed to survey more than 100,000 stars in the galaxy with the goal of identifying the number of sun-like stars that have Earth-size and larger planets, including those that lie in a star's "habitable zone," a region where liquid water, and perhaps life, could exist, the space agency said.Kepler is being prepared for launch on March 5 at Space Launch Complex 17 at Cape Canaveral Air Force Station.
Kepler will mark the first mission to survey the Milky Way galaxy in search of Earth-size planets around other stars.
"A null result is as important as finding planets," Michael Bicay, director of science at NASA's Ames Research Center in California, told reporters in Titusville, Florida.
Kepler has a 0.95-meter diameter photometer - or light meter - with a large field of view for an astronomical telescope. It is equipped with a 95 megapixel camera "“ the largest ever flown in space.
NASA hopes to determine the distribution of sizes and shapes of the orbits of larger planets in or near the habitable zone of wide variety planets.
"Kepler finds planets by looking for tiny dips in the brightness of a star when a planet crosses in front of it"”we say the planet transits the star," said NASA.
"Once detected, the planet's orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler's Third Law of planetary motion."
"The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet's characteristic temperature can be calculated. From this the question of whether or not the planet is habitable (not necessarily inhabited) can be answered," the space agency added.
To find a planet like Earth, scientists will need to catch at least four transits, a process that will take about 3 1/2 years. Its gaze will be fixed on a patch of sky between the constellations Cygnus and Lyra. Ground-based telescopes will be used to verify results, according to Reuters.
More than 330 planets have been observed circling stars in other solar systems, but none of them have had the size or properties suitable for sustaining life.
"There's several astrophysical phenomena that masquerade as planets," Bicay said. "We're going to have to sort them out."
Image Caption: Kepler Mission Star Field - An image by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, showing the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square. Credit: Carter Roberts / Eastbay Astronomical Society
On the Net: | 0.844686 | 3.288199 |
Tonight – July 13, 2016 – as darkness falls, look for the waxing gibbous moon near a reddish “star.” It’s not a star, but instead the red planet Mars. The moon and Mars both reside in front of the constellation Libra on this night. You’ll have plenty of time to catch the evening couple – the moon and Mars – as the twosome will be out until the wee hours after midnight.
And if you miss them tonight, try tomorrow night!
What’s more, there’s another nearby planet – Saturn – which is visible to the east of the moon and Mars. The moon will move on to pair up with Saturn on July 15.
Summer 2016 (winter 2016 if you live in the Southern Hemisphere) presents a grand time to watch both Mars and Saturn. So identify them now, and enjoy them for weeks to come!
Okay, got Mars and Saturn? Now, look westward as soon as darkness falls for another extremely bright planet in the evening sky. It’s the king planet, Jupiter.
Mars was brightest this year in May, when we passed between the red planet and the sun. Mars is one world in Earth’s sky whose brightness changes dramatically. In Mars’ case, the cycle is about two years, as Earth and Mars both orbit the sun.
Mars lodges about seven times farther away at its farthest than at its closest to Earth. Therefore, Mars’ apparent diameter at its farthest point shrinks to 1/7th of its size of when Mars is at its closest.
Yet, that 1/7th-figure doesn’t tell the whole story. At its farthest, Mars disk size is actually 1/49th as great because you have to square the change in apparent diameter to find out how much its disk has shrunk (1/7 x 1/7 = 1/49).
So maybe you can see that July 2016 is good viewing for Mars!
A year from now – in July, 2017 – Mars will pass behind the sun as seen from Earth, to disappear in the glare of the sun. In other words, Earth will have traveled so far ahead of Mars in our smaller, faster orbit that we’ll turn the corner ahead of Mars in orbit, leaving Mars behind the sun’s glare.
Right now – July 2016 – is a great time to watch Mars. So enjoy the red planet before it fades into oblivion in 2017, as seen from our earthly perspective!
Bottom line: Watch the moon! It’s near Mars on July 13 and 14, and near Saturn on July 15, 2016.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York. | 0.859358 | 3.328222 |
Human beings have long wondered whether they are alone in the universe. Now we are closer than ever to getting an answer. That’s thanks in large part to the astronomers who are searching for exoplanets—planets orbiting other stars—that could be home to life.
Three have been most influential of late: Guillem Anglada-Escudé of the Queen Mary University of London, who last year discovered an Earth-size planet orbiting Proxima Centauri, our closest neighboring star; Michaël Gillon of the University of Liège in Belgium, who in February announced the discovery of a full solar system of seven Earth-size planets orbiting Trappist-1, another comparatively local star; and Natalie Batalha, the current lead scientist for NASA’s Kepler space telescope, who has helped find approximately 4,700 new worlds since 2009. If life exists on the closest of these exoplanets, telescopes should be able to confirm its chemical signatures within a decade.
There was a time when Pluto—which NASA’s New Horizons spacecraft at last explored in 2015, a mission I led—was considered the last planet. We now know there are thousands of other, possibly inhabited, planets. Perhaps later in this century or in the next, we will even develop the technology to visit them.
Stern leads NASA’s New Horizons mission | 0.892375 | 3.151349 |
Cape Canaveral: Scientists reported today they finally have "good evidence" for Planet X, a true ninth planet on the fringes of our solar system.
The gas giant is thought to be almost as big as Neptune and orbiting billions of miles beyond Neptune's path, distant enough to take 10,000 to 20,000 years to circle the sun.
This artist's concept illustration, courtesy of Caltech/Robert Hurt shows a distant view from Planet Nine back towards the sun. AFP PHOTO/CALTECH/ROBERT HURT
This Planet 9, as the two California Institute of Technology researchers call it, hasn't been spotted yet. They base their findings on mathematical and computer modelling, and anticipate its discovery via telescope within five years or less.
The two reported on their research today in the Astronomical Journal because they want people to help them look for it.
"We could have stayed quiet and quietly spent the next five years searching the skies ourselves and hoping to find it. But I would rather somebody find it sooner, than me find it later," astronomer Mike Brown told The Associated Press.
"I want to see it. I want to see what it looks like. I want to understand where it is, and I think this will help."
Once it's detected, Brown insists there will be no Pluto-style planetary debate. Brown ought to know; he's the so-called Pluto killer who helped lead the charge against Pluto's planetary status in 2006. (It's now officially considered a dwarf planet.)
His colleague in this latest Planet 9 report, also from Caltech in Pasadena, is planetary scientist Konstantin Batygin.
"For the first time in more than 150 years, there's good evidence that the planetary census of the solar system is incomplete," Batygin said, referring to Neptune's discovery as Planet 8.
The two based their findings on the fact that six objects in the icy Kuiper Belt, or Twilight Zone on the far reaches of the solar system, appear to be influenced by only one thing: a real planet.
Brown actually discovered one of these six objects more than a decade ago, Sedna, a large minor planet way out there on the solar system frontier.
"This is a prediction. What we have found is a gravitational signature of Planet 9 lurking in the outskirts of the solar system,' Batygin said. "We have not found the object itself," he stressed, adding that the actual discovery when it happens will be "era-defining."
Added Brown: "We have felt a great disturbance in the force." Depending on where this Planet 9 is in its egg-shaped orbit, a space telescope may be needed to confirm its presence, the researchers said.
Or good backyard telescopes may spot it, they noted, if the planet is relatively closer to us in its swing around the sun. It's an estimated 20 billion to 100 billion miles from us.
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Photos: Malaika Arora parties wearing see-through lace dress | 0.8887 | 3.266318 |
Galaxies during the era of reionisation in the early Universe (simulation)
Astronomers using ESO’s Very Large Telescope (VLT) have measured the distance to the most remote galaxy so far, UDFy-38135539, existing when the Universe was only about 600 million years old (a redshift of 8.6).At this early time, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies. The transitional period when the fog was still being cleared by this ultraviolet light is known as the era of reionisation, illustrated with this still from a representative scientific simulation (see Alvarez et al. (2009) for more details).
When the Universe cooled down after the Big Bang, about 13.7 billion years ago, electrons and protons combined to form neutral hydrogen gas. This cool dark gas was the main constituent of the Universe during the so-called Dark Ages, when there were no luminous objects. This phase eventually ended when the first stars formed and their intense ultraviolet radiation slowly made the hydrogen fog transparent again by splitting the hydrogen atoms back into electrons and protons, a process known as reionisation. This epoch in the Universe’s early history lasted from about 150 million to 800 million years after the Big Bang. In this visualisation, ionised regions are blue and translucent, ionisation fronts are red and white, and neutral regions are dark and opaque.
The new study shows that the glow from UDFy-38135539 seems not to be strong enough on its own to clear out the hydrogen fog. There must be other galaxies, probably fainter and less massive nearby companions of UDFy-38135539, which also helped make the space around the galaxy transparent.Credit:
M. Alvarez (http://www.cita.utoronto.ca/~malvarez), R. Kaehler, and T. Abel
About the Image
|Release date:||20 October 2010, 19:00|
|Size:||2220 x 1607 px|
About the Object
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|Very Large Telescope| | 0.810116 | 3.855943 |
On the first day of the year 1801, Italian astronomer Gioacchino Giuseppe Maria Ubaldo Nicolo Piazzi found a previously uncharted “tiny star” near the constellation of Taurus. The following night Piazzi again observed this newfound celestial object, discovering that the speck had changed its position relative to the nearby stars.
Piazzi knew that real stars were so far away that they never wandered – that they always appeared in the sky as fixed in location relative to each other. Due to the movement of this new object, the astronomer to the king of the two Sicilies suspected he had discovered something much closer – something within our solar system. Piazzi made history’s first asteroid discovery. He named it after the Roman goddess for agriculture: Ceres.
While astronomers of Piazzi’s era eventually understood there were many more small rocky bodies to be found, for decades after the Ceres discovery, asteroid detections were few and far between. Even a half-century after Ceres’ detection, there were only 15 known asteroids. But as time marched on, so did astronomers’ equipment, techniques and interest in hunting asteroids. By 1868 the number of known asteroids had reached 100. By 1923 it was 1,000. Today, it is more than half a million.
As a nod to the importance of these objects, the United Nations has declared June 30 International Asteroid Day.
Most asteroids are farther from the sun than Mars is – more than 1.5 times farther from the sun than Earth’s orbit is. Asteroids that come closer to the sun than about 1.3 times Earth’s distance from the sun are called near-Earth asteroids.
The term “near” in near-Earth asteroid is actually a bit of a misnomer, since most of these bodies do not come close to Earth at all. As of this month, more than 16,000 of them are known. Near-Earth asteroids and comets that come within the neighborhood of Earth’s orbit are, together, classified as near-Earth objects, or NEOs.
Thanks to new technology, better search techniques and a team of professional and dedicated amateur astronomers hunting for them, the number of known NEOs expands by about five every night of the year.
Ever wonder how these small celestial objects are discovered?
“Just as in Piazzi’s day, it usually starts with just a speck of light in an astronomer’s telescope,” said Paul Chodas, manager of the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“Even with some of the most powerful optical telescopes on the planet tasked with hunting asteroids, they appear as mere specks of light in the sky because they are so small. When an astronomer finds a speck that is moving, that’s when the fun begins.” The Planetary Defense Coordination Office at NASA Headquarters in Washington is responsible for finding, tracking and characterizing potentially hazardous asteroids, issuing warnings about possible impacts, and coordinating U.S. government planning for response to an actual impact threat. Almost always, a new asteroid detection is courtesy of telescopes that are sponsored by NASA.
The planetary defense office oversees the Near-Earth Object Observation Program, which in turn funds the Catalina Sky Survey in Arizona and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii. Both projects upgraded their telescopes in 2015, significantly improving their asteroid and near-Earth object discovery rates.
“Telescopes funded by outside institutions and even some amateurs are also involved with NEO discovery and do other important asteroid-related work,” said Chodas. “But, at present, Catalina and Pan-STARRS are our most powerful asteroid detection instruments. Between these two surveys, four telesopes in all, about 90 percent of all new NEO discoveries are made.”
At the heart of each one of these survey telescopes is a hyper-upgraded version of the same kind of camera chip (called a CCD, or charge-coupled device) that is inside our cellphones.
With the exception of nights that have too much rain or snow, or several nights surrounding a full moon (when moonlight can drown out the faint light of an asteroid), the dedicated observers of Catalina and Pan-STARRS open up their telescopes every night they can find a hole in the cloud cover and take 30-second exposure after 30-second exposure of the heavens above.
Survey astronomers are on the lookout for points of light that move relative to the more distant and fixed background stars. To find them, they take three or more images of the same region of the sky (called a field), separated by several minutes. On a good night a survey will take several hundred photos of the sky.
When survey astronomers find a point of light that appears to move across the same field in a series of images of the same region of the sky, they check it against the predicted positions of all the known objects in the catalog maintained by the NASA-sponsored Minor Planet Center (MPC) in Cambridge, Massachusetts.
If the newfound, moving point of light does not match up with the predicted position and motion of an object in the MPC’s database of known asteroids and comets, there is a good chance it’s a new discovery – but there is more work to be done.
Computers do much of this detection work, but a prudent astronomer also double checks the work, making sure the points of light are not some kind of reflection of a nearby star, or perhaps a faulty pixel on the CCD.
If confident about the potential space-rock discovery, the astronomer ships the discovery’s coordinates (known as the “astrometry”) to the MPC’s NEO Confirmation Page, where it is given a temporary identifier – like YL9E0A0. The MPC also computes an initial (approximate) orbit for the still-to-be-confirmed NEO.
CNEOS has a system called Scout, which actively monitors the MPC confirmation page, getting the data from each potential new asteroid discovery and automatically computing the possible range of future motions even before these objects have been confirmed as discoveries.
“If our calculations indicate a new discovery could be coming close by Earth, we call in the reinforcements,” said Chodas.
“NASA has a worldwide network of astronomers who perform follow-up observations. They take the latest astrometry and try to find the new speck of light, too. If they do find it, they measure its coordinates and send their follow-up astrometry back to the MPC, where it is added to a table of information about the object. This follow-up is extremely important. It really helps expand our understanding of a new discovery’s orbit.”
Usually it takes two to three nights of observations for enough information to be collected on a new discovery for the MPC to verify that a speck of light is indeed a near-Earth object.
When that transformation occurs, the MPC removes it from its confirmation page and replaces its temporary tag with a more permanent name, which always starts out with the year it was discovered and then an alphanumeric code indicating the half-month of discovery and the sequence within that half-month.
The MPC then generates a Minor Planet Electronic Circular which contains all known astrometry and the preliminary orbit of the object. The MPC announces the new asteroid discovery in an email to those who are interested in that sort of thing.
“We are interested all right,” said Chodas. “And we stay interested even after a discovery is announced, because we are in the asteroid- and comet-hunting game for the long run. The more information we get on a celestial object – new discovery or old – the more we refine our knowledge of its orbit.”
All the new orbits are automatically picked up by a computer system at JPL called Sentry, where all asteroid and comet orbits, including those with future close-Earth approaches, are calculated and impact probabilities are assessed daily.
“While NASA is leading the way in near-Earth object survey, we are not resting on our laurels,” said Lindley Johnson, NASA’s planetary defense officer.
“New optical systems are coming on line, new computer programs are being created, and we are exploring new technologies both ground- and space-based that will further accelerate our discovery, characterization and orbital analysis of these potential threats.” | 0.887966 | 3.883461 |
The Next Generation of Deep-Space Telescopes
With Hubble now approaching the end of its scientific life, a new generation of spacecraft are set to blast off in the next few years. These missions may alter the way we see the Universe forever. This article looks at the most exciting prospects of the missions, with easy to understand explanations.
Since it's launch in 1990, the Hubble Space Telescope has produced some of the richest views of the galaxy we have ever seen and some of the most impressive science. In 2015 Hubble has it's last servicing mission and is expected to reach the end of its scientific life sometime in 2020. Over this time Hubble has discovered new star-forming regions in the Pillars of Creation, discovered new galaxies in the Ultra Deep Field and created the highest resolution image ever made of the entire Crab Nebula. It all makes you wonder what the next generation of space telescopes will discover.
Gaia is an ambitious mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. While this sounds a lot, it actually amounts to about 1% of the Galactic stellar population.
While surveying the positions of over a billion stars, ESA's Gaia mission is also measuring their colour, a key diagnostic to study the physical properties of stars.
Wide Field Infrared Survey Telescope
The Wide Field Infrared Survey Telescope (WFIRST) is a future infrared space observatory planned for the mid-2020's. WFIRST is based on an existing 2.4m wide field-of-view telescope and will carry two scientific instruments. The Wide-Field Instrument is a 288-megapixel multi-band near-infrared camera, providing a sharpness of images comparable to that achieved by the Hubble Space Telescope over 100 times the area. The Coronagraphic Instrument is a high contrast small field of view camera and spectrometer covering visible and near-infrared wavelengths using novel starlight-suppression technology.
James Webb Space Telescope
James Webb Space Telescope is a space telescope as part of NASA's Next Generation Space Telescope program which is scheduled to launch in October 2018. It features a large infrared telescope with a 6.5-meter primary mirror and will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System. | 0.867056 | 3.660674 |
A team of experts have currently discovered that Comet C/2014 Q2, also known as Lovejoy, is discharging large amounts of alcohol as well as a type of sugar into space. This has been the first time ethyl alcohol has been found in a comet. The article was published today in the journal Science Advances.
This investigation became an important objective to achieve for scientists in January and February of this year. Comets are key elements in astronomical investigations due to the fact that they are relatively pristine and may hold clues to how the solar system was made.
The Institut de Radioastronomie Millimétrique (IRAM), located on Pico Veleta in the Sierra Nevada (Spain), facilitated the study by lending investigators their IRAM 30m telescope. Thanks to the versatility of the receivers and spectrometers of this telescope, scientists were able to observe the atmosphere of comet Lovejoy during two periods – between 13–16 and 23–26 January 2015. To study the line of molecules, investigators used the latest spectroscopic data available in the JPL or CDMS database.
The analysis revealed lines of 21 molecules. Two of these were detected for the first time in a comet, ethanol and glycolaldehyde, a type of sugar. Furthermore, this comet originated from the Oort cloud and has been the only comet where depletion has been observed for such a large number of molecules.
“The result definitely promotes the idea the comets carry very complex chemistry,” said Stefanie Milam of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a co-author on the paper.
Around 3.8 billion years ago the Earth got attacked by comets and they may have scattered around some of their molecules. Current findings of this study suggest that comets could have been a source of the complex organic molecules necessary for the emergence of life on Earth.
According to another co-author of the paper, Dominique Bockelée-Morvan from Paris Observatory, further studies have to take place in order to define where the organic material of the comet came from; whether it was from the time when the solar system was formed or if it was created later on.
Source: Science Advances | 0.858898 | 3.660075 |
Return to the Moon
On July 20, 1969, man first set foot on the Moon.
Almost exactly forty years since Neil Armstrong and Buzz Aldrin made history on the dusty plains of the Sea of Tranquillity, NASA has returned to the Moon.
This time, we are going back to stay.
This vanguard for our return to the Moon – the Lunar Reconnaissance Orbiter – launched from Pad 41 at Cape Canaveral Air Force Station on Thursday, June 18. It slid, with little fanfare, into lunar orbit on Tuesday, June 23.
According to Richard Vondrak, Project Scientist for the LRO and Deputy Director of Solar System Exploration, the LRO spacecraft will spend several weeks maneuvering into its polar orbit. LRO’s camera is capable of imaging the lunar surface at such a high level of detail, it will be able to take pictures of the descent stages of the Apollo landers, the craters their descent engines made, and even items of hardware left behind by the men who walked there forty years ago.
The recent launch carried two missions: the LRO mission itself and the separate LCROSS mission. LCROSS (Lunar Crater Observation and Sensing Satellite) comprises the Centaur booster upper stage and the interstage adaptor ring (which joined the booster and the LRO payload during launch). The adaptor ring has been fitted with instruments that will observe the Centaur upper stage as it crashes into a permanently shadowed crater in the south polar region of the Moon on October 8, 2009. The impact of the booster will create a fresh ejecta plume from the lunar surface that will allow the instrumented adaptor ring following behind it to detect – using infrared and visible light spectrometers and cameras – whether the impact of the booster exposed traces of water ice.
LRO is one of the most ambitious and important experiments in the history of the scientific investigation of the Moon, according to Vondrak. “We want to identify whether there is hydrogen at the poles that is associated with water ice or the other volatiles,” he says. “Our goal is to locate them, measure their concentration and after that the question becomes: Is that material accessible in the quantities required for use?"
The Lunar Reconnaissance Orbiter’s photograph of the Apollo 14 landing site.
Credit: NASA/Goddard Space Flight Center/Arizona State University
Finding water ice on the Moon is important because, if there is enough water to access, future expeditions will be able to use it to support the habitation and eventual colonization of the Moon. Not only could the water be used for human consumption, but the hydrogen in the water could be converted into rocket propellant.
Vondrak sees the LRO mission as the first step in humankind’s journey to Mars and then beyond. “The official NASA goal of going to the Moon … is to get experience in living and working off of our home planet and living and working on another planetary surface, testing systems so that then we are better prepared to go to Mars,” he notes.
NASA’s LRO will use its six instruments collecting detailed information about the lunar environment from a low polar orbit.
However, Vondrak is clear that the merits of a Moon mission are sufficient on their own terms. “There are many interesting places on the Moon, there are many places we would like to go purely for science, and so I expect that developing the capability to return to the Moon safely will have many benefits both for exploration and for science.”
Farouk El-Baz, the geologist behind the site selection of the Apollo missions, is equally enthusiastic about the return to the Moon. “There are all kinds of questions about the Moon which remain to be answered,” he says. “I think to answer them in the best way is to send robotic missions. We already have all kinds of information from three missions sent to the Moon by India, Japan and China, and [the LRO and LCROSS missions] will add to that.”
However, El-Baz is less enthusiastic about the idea of sending humans back to the Moon. “Our objective in the long run should be an astronauts’ mission to Mars. That’s what we should concentrate on.”
But Vondrak points out that “the intent is not to build spacecraft [on the Moon], but to use it as a place to test systems and to learn how to live and work on another planetary surface”
NASA’s LCROSS mission will confirm the presence or absence of water ice in a permanently shadowed crater at the Moon’s South Pole.
Credit: NASA Ames
El-Baz emphasizes that the best place to launch a mission to Mars is from a stable, strategically-positioned, orbiting space station. “There is an L5 point between the Earth and the Moon [where the gravity is much less] than the gravitational pull of the Moon,” he notes. “If you want to put together a [human-carrying] spacecraft to send to Mars, you don’t need to go to the Moon at all.” El-Baz comments that President Obama has already appointed a committee, chaired by Norm Augustine, former CEO of Lockheed Martin, to consider these and other suggestions. As El-Baz says, “For the US to remain in the lead of space business, the US needs to send humans to Mars.”
Returning to the immediate drama of the LRO, however, another ardent supporter of the mission is Bill Hartmann, a lunar specialist since the days of Apollo and the co-developer of the impact theory of the origin of the Moon. Like Vondrak and El-Baz, Hartmann believes that the search for ice on the Moon is very important but – as an inveterate crater enthusiast – he is very excited about what the LRO and LCROSS mission will tell us about the rate at which small craters form on the Moon. This is important because, once that number has been established, he says it will be possible to work out the age of geomorphologic features on the Moon and elsewhere. Hartmann is intrigued by the notion that the LRO data – by telling us the rate of cratering in our part of the solar system – will eventually allow us to date the age of geologic formations on Mars.
On July 17, 2009, NASA released pictures of five of the six Apollo landing sites (images of the Apollo 12 landing site will be acquired next month). The resolution of the images will only get better as the LRO retrieves more data. The most detailed images so far released are from the Apollo 14 landing site at the Fra Mauro highlands – the site that ill-fated Apollo 13 had aimed for. The images from the Apollo 14 site are so detailed that the tracks left by the astronauts between the Lunar Module and the ALSEP instrument package are clearly discernable, “like going into an old building [where] the carpet is worn out down the middle of the hall” as LRO Camera principal investigator Mark Robinson of Arizona State University put it.
The traces of the Apollo 14 astronauts pulling a "shopping cart" while traversing the surface to reach Cone crater are clearly visible in the images. This indicates that the lunar dust layer is brightened by solar radiation, since the disturbed area by human activity exposed darker soil.
LRO and LCROSS will provide essential information for NASA’s return to the moon. NASA is currently developing a new fleet of spacecrafts and rockets in order to transport equipment and human explorers to the Moon. In the near future, humankind may once again spread its reach beyond our home planet.
El-Baz comments, “These are fabulous photographs in the highest resolution we have ever seen. They tell a great deal about the Apollo landing sites. For example, now we see how dramatic the large crater east (to the right) of Apollo 11’s landing looks. The lander would have crashed into it had Neil Armstrong not taken over the controls to move farther west. Similarly the photograph of the Apollo 16 landing site shows it is perilously close to a large crater pit.”
Hartmann, when asked (days before these images were published) whether he thought the Apollo landing site images would be the final rebuff for all those who claim the Moon landings were bogus, sighed wearily. “They’ll just say we faked the pictures.”
Now though, any space buff worth the name can compare these new images (http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/apollosites.html) with the fantastically detailed map of the Apollo 14 traverses available on Google Moon (http://www.google.com/moon/). A quick comparison shows the match is virtually perfect. So much for the conspiracy theorists!
But, in fact, we did not need these new data to rebuff those nay-sayers of one of humanity’s greatest achievements. Hartmann rightly points out that the science that came out of the Apollo landings is proof enough that America went to the Moon. “The Russians also went to the Moon with their robotic probes, and three of them returned samples to Earth. Do people really believe that the Soviets would have failed to publicize it if their scientific findings of the Moon’s geology had differed from those published by the Americans at the height of the Cold War?”
The real excitement of the LRO and LCROSS missions lies in the future rather than in nostalgia of past glories. It is already clear that the science that LRO and LCROSS will be doing in the next few months will impact directly on humanity’s plans to head for the planets of our solar system, and, ultimately, the stars. | 0.847868 | 3.445118 |
**By Duncan Geere, Wired UKA team of exometeorologists at MIT have calculated the size of the snowflakes that fall onto the polar regions of Mars in its winter, and it turns out that they're pretty tiny.
[partner id="wireduk"] Mars' weak atmosphere is comprised almost entirely of carbon dioxide, and during the chilly -87C winters on the red planet, it gets cold enough for particles of snow to form. Except that it's not snow as we know it, which is made of water crystals. Instead, it's dry ice – frozen crystals of carbon dioxide.
Using data from orbiting spacecraft, MIT researchers found that the crystals are about the size of a red blood cell – eight to 22 micrometers across – in the northern hemisphere and a smaller four to 13 micrometers across in the southern hemisphere. "These are very fine particles, not big flakes," said Kerri Cahoy, who worked on the project, in a press release, adding that if you were standing in a Martian blizzard, "you would probably see it as a fog, because they're so small."
To work out how big the particles are, the team first estimated the mass of snow deposited at both poles by measuring tiny changes in the planet's gravitational field over the seasons. Using this mass, and physical characteristics of carbon dioxide crystals, the team was able to determine the number of snow particles in a given volume of snow cover, and from there the dimensions of the particles.
"It's neat to think that we've had spacecraft on or around Mars for over 10 years, and we have all these great datasets," Cahoy said. "If you put different pieces of them together, you can learn something new just from the data."
The research addresses the question of how Mars' ice caps form. Over the course of a 687-day-long Martian year, snow clouds can stretch half-way to the equator, before shrinking back again as winter recedes. Since carbon dioxide makes up almost the entirety of the planet's atmosphere, it's hoped that it could shed light on Mars' climate – something that would be crucial if humans were to ever settle on the planet.
The research was funded by the Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission.
Source: Wired UK
Image: MSSS, JPL, Nasa | 0.83651 | 3.822906 |
The find of a largest timing anomaly nonetheless celebrated in a pulsar is a initial acknowledgment that pulsars in binary systems vaunt a bizarre materialisation famous as a ‘glitch’. The investigate is published in a biography Monthly Notices of a Royal Astronomical Society.
Pulsars are one probable outcome of a final stages of expansion of vast stars. Such stars finish their lives in outrageous supernova explosions, ejecting their stellar materials outwards into space and withdrawal behind an intensely unenlightened and compress object; this could possibly be a white dwarf, a proton star or a black hole.
If a proton star is left, it might have a really clever captivating margin and stagger intensely quickly, emitting a lamp of light that can be celebrated when a lamp points towards Earth, in most a same approach as a beacon lamp unconditional past an observer. To a spectator on Earth, it looks as yet a star is emitting pulses of light, hence a name ‘pulsar’.
Now a organisation of scientists from the Middle East Technical University and Başkent University in Turkey have detected a remarkable change in a revolution speed of a rare pulsar SXP 1062. These jumps in frequency, famous as ‘glitches’, are ordinarily seen in removed pulsars, though have so distant never been celebrated in binary pulsars (pulsars orbiting with a messenger white dwarf or proton star) such as SXP 1062.
SXP 1062 is located in a Small Magellanic Cloud, a satellite universe of a possess Milky Way galaxy, and one of a nearest intergalactic neighbours during 200,000 light years away. Lead author of a study, Mr M. Miraç Serim, a comparison PhD tyro operative underneath a organisation of Prof Altan Baykal, said, “This pulsar is utterly interesting, given as good as orbiting a partner star as partial of a binary pair, it is also still surrounded by a ruins of a supernova blast that combined it.”
The pulsar is suspicion to lift in a leftover element from a supernova explosion, feeding on it in a routine famous as accretion. The group trust that a distance of a glitch is due to a gravitational change of a messenger star and this summation of a surrounding vestige material, that together strive vast army on a membrane of a proton star. When these army are no longer sustainable, a fast change in inner structure transfers movement to a crust, changing a revolution of a pulsar really unexpected and producing a glitch.
“The fractional magnitude burst celebrated during this glitch is a largest, and is singular to this sold pulsar”, commented Dr Şeyda Şahiner, a co-author of a study. “The distance of a glitch indicates that a interiors of proton stars in binary systems might be utterly opposite to a interiors of removed proton stars.”
This work was primarily presented in 2017 during a European Week of Astronomy and Space Science, that will be hold subsequent year in Liverpool jointly with a UK National Astronomy Meeting. The work will be followed adult with NASA’s Neutron Star Interior Composition Explorer (NICER) mission, launched in Jun this year – a group wish that a anticipating might lead to a improved bargain of a interior of a proton stars, putting new constraints on a proton star equation of state.
Comment this news or article | 0.817915 | 3.816401 |
The universe is more than a smattering of distant stars—it’s also chock-full of other worlds. But if the universe is so crowded, where is the alien life? While there are many theories addressing this apparent contradiction, known as the Fermi Paradox, new research suggests that people may just not be looking for aliens in the right places.
A pair of scientists, Rosane Di Stefano, of the Harvard-Smithsonian Center for Astrophysics, and Alak Ray, of the Tata Institute of Fundamental Research, in India, suggest we should be looking to globular clusters. The duo explained their research this week in a presentation at the American Astronomical Society meeting.
Globular clusters are dense clumps of stars that formed billions of years before our solar system. This age and close proximity of so many potential worlds together could give alien life both the time and resources necessary to brew complex society, reports Alexandra Witze for Nature.
Developing the technology to hop from star system to star system within a cluster would be easier than the kind of power needed for Earthlings to cross the distance to our nearest neighbors, explains Rachel Feltman for The Washington Post. That means that interstellar travel and communication would be easier in a globular cluster, which could provide many benefits—for one, if the resources of one planet were exhausted, an advanced civilization could jump to the next star system or planet more easily.
"The Voyager probes are 100 billion miles from Earth, or one-tenth as far as it would take to reach the closest star if we lived in a globular cluster,” Di Stefano says in a press statement. "That means sending an interstellar probe is something a civilization at our technological level could do in a globular cluster." Since globular clusters are so old, if a civilization exists in one, it could already be far more advanced than our own, residing on a planet that is nearly 4.5 billion years old.
So far, few researchers have looked to globular clusters to find evidence of alien life or even planets at all—only one planet has ever been spotted in a globular cluster.
The prevailing wisdom is that gravitational interactions between all of the closely grouped stars would rip apart any nascent planets before they could form. Also, since these clusters formed on an average of about 10 billion years ago, the stars they host have fewer heavy elements like iron and silicon—the building blocks for rocky planets, according to a press release.
Even so, that doesn’t mean that planets can’t form in such clusters, Di Stefano and Ray argue. Stars in clusters are longer-lived and dimmer, so any habitable planets would be those that “huddle close” to their stars in the narrow zone where temperatures are warm enough for liquid water to flow, Feltman explains. This close grouping could actually protect planets from gravitational interactions, according to De Stefano and Ray.
The team determined that there is a sweet spot for the spacing of stars within a cluster that is "stable enough for a planet to form and survive for billions of years,” Witze writes. That distance works out to be about 100 to 1,000 times the distance between the Earth and the Sun.
Di Stefano even has a list of clusters that researchers should investigate, Witze reports. Terzan 5, a cluster hanging out near the center of the Milky Way, is at the top of that list. That cluster is very dense but also carries more metal than most other documented globular clusters.
With the clusters so far away, the first discovery of life is more likely simple microbes in someplace like the subsurface ocean of Enceladus, Saturn’s geyser-spouting moon. But these Di Stefano and Ray don't think we should lose hope: There may be aliens capable of holding a conversation with us some where out there amid the stars. | 0.877187 | 3.584027 |
Are the climatic changes a sign of troubles ahead?
The title of this article may seem a little dramatic, but you have to admit, we are seeing some unusual changes just lately.
Global Warming has been a “hot” subject for some years now, yet many have rightly pointed out that some parts of the planet have seen unusually cold weather. Britain has just experienced its heaviest snow fall in 18 years, an event that has only been seen twice in almost 50 years.
Russia, where this sort of weather is more expected, has experienced relatively mild winters in the last 15 years or so. Yet in South-Eastern parts of Australia, they are witnessing some of the hottest temperatures in 100 years!
So, are we seeing Global Warming, or Global Cooling? Or is something else happening?
There has been a lot of talk about the recent lack of solar activity (no sunspots) and according to some records, this often happens when the Earth goes through a cooler period.
Others have mentioned the possibility of a magnetic pole shift, where the poles change so that North becomes South and South becomes North. The last time this happened was around 790,000 years ago. However, there seems to be no pattern to this event, which has apparently occurred 400 times in the last 330 million years, but it would seem that such a change is overdue.
Many believe the shift has already begun, but historic records have shown that this can take at least 1,000 years to complete (sometimes much longer). The last four shifts took around 7,000 years each.
According to an article in the National Geographic News, the North magnetic pole is moving at a rate of 25 miles a year. “Over the past century the pole has moved 685 miles (1,100 kilometers) from Arctic Canada toward Siberia,” says Joe Stoner, a paleomagnetist at Oregon State University.
Whilst the North magnetic pole does move around by as much as 50 miles in a day, reports clearly indicate that a much more significant magnetic change is taking place.
Quite recently it was announced that the heliosphere, the protective shield of energy that surrounds our solar system, has weakened by 25 per cent over the past decade. The heliosphere is created by the solar wind, a combination of electrically charged particles and magnetic fields that emanate at more than a million miles an hour from the Sun and meet the intergalactic gas that fills the gaps in space between solar systems.
Scientists are unsure why this protective shield (the heliosphere) has shrunk so much and so quickly, but it is certainly a serious problem for our planet if it continues to shrink at its current rate.
It is my belief that our solar system is passing through an area of our galaxy that is harmful to our planet and all the other planets in the system (including our Sun). It takes approximately 250 million years for our solar system to orbit the galaxy, and if you check the historic records to see what happened the last time we passed this area, you will see some similarities emerging.
Modern day pollution did not exist just before the dinosaurs appeared and that was clearly not the reason for the “Great Dying” and increased temperatures, and it is extremely unlikely that is the reason now.
The changes we are seeing on our planet and in the solar system are the result of something massive, to blame this on pollution would be like saying one lit cigarette can increase the planets temperature by 2 degrees (impossible!).
However, thanks to people like Al Gore, we have all been panicked into thinking man is the cause of our climatic changes, and as a result we have to live with carbon trading, and silly energy saving bulbs that make candles seem bright!
Will the magnetic poles shift? Yes (eventually). Will a climatic change cause a mass extinction on our planet? Yes (It often does). Could we see a super volcano erupt, or a large asteroid hit the Earth? That’s a guarantee! (We just don’t know when). Is it possible we will kill ourselves in some nuclear war? Very likely!
Maybe the title wasn’t so dramatic after all? THE END IS NIGH! | 0.832152 | 3.156676 |
A group of Spanish astronomers using the Liverpool and Mercator Telescopes at the Observatorio del Roque de los Muchachos have recently reported the discovery of a binary star system comprising a Be-type star and, remarkably, a black hole.
Jorge Casares of the Instituto de Astrofisica de Canarias (IAC) and La Laguna University (ULL) is lead author on a paper1, recently published in the science journal Nature, in which he and his colleagues present their exciting results.
Be-type stars are known to be fast rotators, and many find themselves to be one-half of an interacting binary system. However, their companions are usually neutron stars. This is the first time that the object orbiting the Be star has been identified as a black hole.
The newly-discovered system is located in the constellation Lacerta (the Lizard), at a distance of about 8,500 light years from the Earth. Known as MWC 656, the Be star rotates with an angular velocity of more than 1 million kilometres per hour. At this speed the star is close to being ripped apart by centrifugal forces, and is ejecting matter through an equatorial disk towards its mysterious companion. Casares' new spectroscopic observations indicate that this companion is a black hole.
A detailed analysis of the spectrum of MWC 656 suggests that its companion has a mass somewhere between 3.8 and 6.9 times that of the sun. Such an object is too massive to be a neutron star, and can only be a black hole. Matter is transferred from the Be star, though its equatorial disk, down onto the black hole via a second disk (an "accretion disk"). By analysing the emission from this second disk Casares and his team were able to measure the mass of the black hole.
In all likelihood, binary systems comprising Be-type stars and black holes are far more common than previously thought. Even so, it is notable that such a discovery was made using two relatively modest-sized telescopes, the 2.0 meter LT and the 1.2 meter Mercator telescope.
|Spectroscopic observations obtained with FRODOspec on the Liverpool Telescope showing the orbital evolution of emission lines from ionised Iron (Fe) and ionised Helium (He) atoms: (a) a sequence of spectra showing the change in line profile shape through one orbital phase; the vertical dashed line indicates the rest wavelength of each transition. (b) trailed intensity images of the same two emission lines plotted across two orbital cycles. See paper [ Nature | Astro-ph ] for further details.| | 0.801643 | 4.050133 |
If you were soaring through Jupiter’s turbid skies wearing a pair of x-ray goggles, you might get lucky and witness something incredible. Brilliant flashes of light, more luminous and powerful than the Sun, occurring every 26 minutes and stretching as far as the eye can see. That’s the essence of a massive solar storm recently witnessed for the first time near Jupiter’s north pole.
“When I first saw this, I thought I’d made a mistake,” Will Dunn, a PhD student studying astrophysics at the University College London, told Gizmodo. The northern lights Dunn observed on Jupiter are hundreds of times brighter than the aurora borealis on Earth. “We’re still not sure exactly what’s causing it.”
Jupiter’s northern lights, created when the gas giant’s prodigious magnetic field interacts with charged particles from the Sun, have long fascinated planetary scientists. But after decades of observation, many puzzles remain. Chief among Jupiter’s space weather mysteries is a bright x-ray aurora, located near the planet’s north pole. It never goes away, but since 2006, scientists have watched it brighten and fade every 45 minutes, light a lightbulb on a dimmer switch. Now, Dunn’s observations with the Chandra X-ray observatory and other telescopes have added another twist to this dazzling enigma.
Writing today in the Journal of Geophysical Research, Dunn and his co-authors describe what happened when a coronal mass ejection—a giant cloud of magnetized plasma that erupted from the surface of the Sun—struck the gas giant’s magnetosphere in 2011. When this happens on Earth, we get the northern lights. On Jupiter, the forever-aurora gets bigger and flashier.
“We saw the pulsing get much quicker: it happens about every 26 minutes during a solar storm,” Dunn said. “And we saw a bright enhancement in a region where we’d never seen it before.”
“If your eyes could see x-rays, you’d see something similar to the aurora on Earth,” Dunn continued. “Except the flashing across the the sky would be much bigger and brighter. Jupiter’s auroras cover a region larger than the entire Earth, so it would stretch as far as the eye can see.”
Why Jupiter’s northern lights flicker to a particular tempo, and why that flickering accelerated during the 2011 solar storm, are questions that planetary scientists would love to answer. “We think that when a coronal mass ejection crashes into Jupiter’s magnetosphere, it compresses it by about 2 million kilometers,” Dunn said. But for more details, we may have to wait for NASA’s Juno mission, which reaches the boundary between the Jupiter’s magnetic field and the solar wind this summer.
In addition to offering yet another mind-blowing glimpse into the meteorological events occurring in our cosmic backyard, Jupiter’s aurora provides a second benchmark for understanding how magnetic fields protect planets from powerful stellar eruptions. And that knowledge may eventually aid in the search for life beyond our solar system.
“We have a pretty good understanding of how the Earth’s magnetosphere works,” Dunn said. “But the universe is filled with magnetically active objects, including billions of exoplanets. Understanding the diversity of magnetic fields has relevance for understanding whether any of those other planets can support life.” | 0.861897 | 3.983745 |
Alaska is known as a good place for seeing the polar aurora, also known as "Northern Lights." Originally the phenomenon was named "Aurora Borealis," Latin for "northern dawn," since in the lower 48 states or in mid-Europe it may appear (on the rare occasions when it does) as a glow on the northern horizon, as if the sun was rising from the wrong direction. But the southern hemisphere has the same phenomenon, with the glow coming from the south, so scientists prefer to call it simply the "Polar Aurora."
Most visitors to Alaska never get to see an aurora, because they come in the summer, when skies are rarely dark enough. Alaskans claim that only around August 16 does the sky get dark enough to see stars, which is when aurora stands out. After that date, your best bet is to go to Fairbanks--and since the brightest auroras occur around midnight (or later, due to Alaska's time zone), you might have to stay up a long time. Perhaps it is better then to ask the night clerk at your hotel to ring you up if a good display becomes visible.
Appearance and relation to magnetism
What does it look like? Most often, you see greenish white ribbons stretching across the sky, roughly from east to west, usually with waves in them. In Fairbanks they could be overhead, in northern Norway or Sweden too, sometimes even in Winnipeg. Further south those ribbons tend to be near the northern horizon. And if you look closely at them, you will note that they contain many parallel rays, running across their width (see picture below).
Two things about those rays. One, the bright ones fade while dim ones brighten instead--a bit like flames in a fireplace, and just as mesmerizing. Some auroras are deep red, and these may be just a shapeless glow--or they may have rays, too. And second, the direction of those rays is related to the magnetism of the Earth.
|The aurora--a woodcut by Fridtjof Nansen|
Anyone who has ever used a compass knows that the Earth is a giant magnet. The needle of the compass usually points towards one of two points, the magnetic poles of the Earth, located near the geographic poles. But because the compass needle is mounted horizontally, it does not show everything. Actually, the magnetic force points not just northward but also slants down into the Earth. Compass needles carefully balanced on a horizontal axis ("dip needles") point in that slanting direction, when allowed to swing in a north-south vertical plane. In fact, the angle gets steeper the closer one gets to the magnetic pole. At the pole the force is vertical. The rays of the aurora faithfully follow that slanting direction.
The Auroral Zone
That was one clue that the aurora was related to the Earth's magnetism. The other clue was found by keeping tabs on how often aurora was seen in various locations. It turned out that the important factor was distance from the magnetic pole. That pole is separated from the geographic pole, marking the Earth's rotation axis, and currently it is in the Arctic Ocean, just north of Canadian soil. The fact it is displaced towards America means Americans do not have to go as far north to see aurora as do, say, residents of Siberia, on the other side of the globe. Locations about 1500 miles from the magnetic pole are where aurora is seen most frequently: further away or nearer to the magnetic pole, they get more rare (they are quite rare at the magnetic pole itself). Fairbanks, Alaska, at the edge of the "auroral zone, " makes a good observation post.
What you usually see there are those quiet curtains and ribbons. But not always. At some times they change shape rapidly, advance, retreat or bulge out in a violent fashion, and they also get quite bright. Scientists call such an active, violent outburst an "auroral substorm, " and satellites still study the release of energy, far in space, which causes it. If you are lucky you may also see a "corona"--a burst of rays radiating in all directions. That is a caused by perspective--like the rays of the sun setting behind a cloud--and it means it the rays of the aurora are arriving right overhead.
Is the polar aurora rare? Depends on where you are! If your home is in Fairbanks, or in Tromso, Norway, or Fort Churchill, Canada--not at all. You won't see it every evening, but it is present frequently enough. In Washington D.C., or London, or Beijing, however, it is a rare event, seen only when the Sun creates "stormy conditions." On such occasions--especially near the peak of the 11-year sunspot cycle--the Sun sends out a dense cloud of hot gas, whose arrival disturbs the Earth's magnetic environment and produces a so-called "magnetic storm" (more details, further below).
Magnetic storms expand the auroral zone to locations more distant from the magnetic pole--such as Washington, London or Beijing--and also create bright auroras. If this happens on a clear night, residents in those cities can see an aurora, but it is a rare treat for them. On the right is a satellite image of an aurora extending to the "lower 48 states" of the US (note Florida, outlined by its city lights). Later that day, in March 1989, the aurora actually spread much further southward, but no satellite was in position to photograph it then. The next picture below is of a 2001 aurora seen in Purcellville, Virginia.
Electrons of the Aurora
To early observers, and well into the 20th century, the polar aurora was a great mystery. Not everything is solved even now--but thanks largely to space satellites, we have a fair understanding of the way the aurora is produced.
First question-- how high up is it? By comparing photographs taken from separated locations, an altitude of about 60 miles was found for the green aurora, and up to about twice as much for the red one. Clues like that led scientists to conclude that "something out there" was shooting towards us beams of fast electrons, somewhat like the ones painting the picture inside a TV picture tube. In a TV, electrons hit a screen, come to a stop, and their energy is converted to light. Something similar happens with the electrons that cause the aurora: they collide with atoms in the upper fringes of the atmosphere, give up their energy to those atoms and cause them to emit light.
And what are electrons? Tiny particles with negative electric charge, contained in all matter. At the center of every atom is a nucleus, containing almost all of its mass and always carrying a positive electric charge. The positive charge attracts electrons and binds them, and jointly the two types yield an ordinary atom, electrically neutral, with no excess charge of either kind. Atoms like this build up you, me, and anything we can see on Earth.
The green and red colors are emitted by atoms of oxygen after they are hit by fast electrons. Each element emits its characteristic colors, and for rarefied oxygen, these appear to us green or red. Typically, a delay of 0.5-1 second exists between collision and the emission (in this case--not in denser surroundings!), and that is why the rays of the aurora brighten and fade so slowly. The beam of electrons which "excites" the oxygen atoms may only last a small fraction of a second, but the afterglow persists 0.5-1 seconds or more.
The Aurora and Magnetic Field Lines
And what connects the pattern of the aurora to the region of the Earth's magnetic forces--the "magnetic field" of the Earth, as that region is known? For such a region, extending far into space, a convenient method is needed to describe it there. Such a method is provided by magnetic field lines, or as they were once called, "magnetic lines of force."
Chances are you have seen a drawing of the field lines of a bar magnet. They fan out from one pole, bend around in big curves, and then converge on the other pole. The magnetic pattern near Earth is like that, too--it is as if the Earth had a small (but oh so powerful!) bar magnet in its center: the lines fan out from the region near the south magnetic pole, reach their greatest distances above the equator, then converge again near the north magnetic pole.
To define field lines more exactly, imagine you had a compass needle hanging in space, able to tell us the exact direction of the magnetic force, in 3 dimensions. Such a needle will always point in the direction of the magnetic field line at its location. North of the equator such lines converge towards the region near the north magnetic pole, just like those of a bar magnet.
Back to the aurora. Between 1895 and 1907 the Norwegian physicist Kristian Birkeland tried to study its behavior in a lab. Inside a glass vacuum chamber he mounted a sphere with a magnet inside--he called it "terrella," Latin for "little Earth"-- and directed towards it a beam of electrons. To his surprise and gratification, the magnet steered the beam right to a patch around the magnetic poles of his small sphere, producing there, as it hit, a visible glow. He probably thought-- aha, so that is how it is done!
It turned out (and I skip a lot) that negative electrons and positive ions alike are guided in space by magnetic field lines. They tend spiral around them, meanwhile sliding along them, like beads on a wire. Because Birkeland's field lines reached the terrella near its magnetic poles, that is where his electrons came down. Similarly magnetic field lines of the Earth guide electrons of the aurora to come down in the auroral zone. No wonder the rays of the aurora pointed along such lines! Each was produced by a ray of electrons, riding its own field line down to the atmosphere. But where did those electrons start from?
The Sun's Corona and the Solar Wind
Physical processes usually require a source of energy to drive them. Think of energy as a kind of money, paying for every physical process! Any object moving at great speed needs energy to do so--its "kinetic energy"--and if the aurora contains beams of electrons moving at 1/10 the velocity of light, something must have paid the price, must have provided the energy.
Not surprisingly, it is the Sun. Indeed, why not? After all, the Sun powers almost every process on Earth: the food we eat, the coal and gasoline we burn, the winds that blow and the rain which waters the land--none would exist without the energy provided by sunlight. With the aurora, however, it is not the light of the Sun, but something more subtle, the so-called solar wind.
During a total eclipse of the Sun one can see the outermost layer of its atmosphere, the corona, a glowing halo around the darkened Sun. It turns out (by examining its light) that the corona is incredibly hot--about a million degrees centigrade, nearly 2 million Fahrenheit. Such extreme heat will tear electrons off any atom, turning the corona into a "soup" of free ions and free electrons, a strange gas known as a "plasma" which (among other things) conducts electricity. If you use fluorescent tubes, or have watched neon lights--it's the plasma inside them (not as hot as the corona) which carries their electric current and produces their light.
The plasma of the corona is far too hot for the Sun's gravity to hold it captive. Instead, it constantly expands away from the Sun and is blown off as the solar wind, filling the solar system and reaching Earth, and far beyond, past Pluto's orbit. The Earth's magnetic field, however, is an obstacle which the solar wind cannot penetrate. Like a river meeting a rock, it splits up and is diverted to flow around it. Around the Earth a cavity is formed, protected from the solar wind and known as the Earth's magnetosphere. And just as a rock in a river leaves a long shielded wake behind it, the Earth's magnetic space has a long tail on the night side--some call it the Earth's "magnetotail. "
But even though the solar wind is kept out, it manages to transmit some electric energy to the magnetosphere, by brushing against it--in particular, to the tail region. Let me say here at once, the tail is where most electrons of the aurora seem to come from, which is why in Fairbanks the brightest aurora tends to occur around midnight--even in arctic winter when the sky is dark at most other times, too.
At home, energy is carried by electric currents that flow from electric outlets to lamps, appliances and TV. The energy of the solar wind also reaches the magnetosphere (at least in part) by means of electric currents. Satellites have observed those currents near Earth: they flow in and out of the auroral zone, along magnetic field lines--for the main circuit, in on the morning side of midnight, out on the evening side, the two branches connecting (since any electric circuits must be closed!) through the high atmosphere, which (as noted) conducts electricity. One might perhaps say that we are still searching where the plug is.
Maybe the situation is not quite that dark. A lot is known. But the complete picture--where we can say "it has to be so, there exists no other way"-- that we still lack.
The Radiation Belt
One more detail is needed, a process called mirroring, without which the Earth might have neither aurora nor radiation belts.
Radiation belts were discovered by the first US artificial satellites, Explorer 1 and Explorer 3. In October 1957 the Soviet Union shocked the US by unexpectedly launching its two "Sputnik" satellites, while the "Vanguard," the US entry in the "space race," crashed in flames during launch, in full view of cameras. The sagging US prestige was redeemed a bit in early 1958 when instruments aboard the above satellites, designed and operated by the University of Iowa team under James Van Allen, detected a permanent belt of trapped ions, surrounding the Earth. They turned out to be protons--atomic nuclei of hydrogen atoms stripped of their single electron.
Earlier it was claimed that electrons or protons tended to be guided by magnetic field lines, like beads on a wire. The ones which guided radiation belt particles had a typical shape--they came out of Earth's southern polar region, described a wide arc across the equator, and returned back to Earth near the northern pole.
But if the analogy with beads on a wire were complete--wouldn't trapped particles slide to the ends of those wires, then hit the Earth and get lost? Quite true--except the analogy is not perfect. The ends of those lines also experience a much stronger magnetic force, being much closer to Earth than other parts, and that can be shown to repel those "beads." By being repelled from regions of strong magnetic force, trapped electrons and ions avoid reaching the atmosphere. Instead of getting absorbed, they get "mirrored" back and forth--in some cases, for years!
Electrical Currents of the Aurora
The same process is also essential to the aurora. We already mentioned large electric currents flowing from the tail into the polar regions and back again, flowing along magnetic field lines, earthward on the morning side of midnight, outbound on the evening side (for the main circuit--a secondary one also exists). They were first mapped in 1973 by two US scientists, Al Zmuda and Jim Williamson--not with a well-supported space research mission, but using a small experiment and a bummed "piggy-back" ride with a navigational satellite of the US Navy. Those currents are now known as "Birkeland currents, " honoring the Norwegian who first shot electron beams at a magnet in vacuum.
The currents along magnetic field lines in space turn out to be carried almost entirely by electrons--descending towards Earth west of midnight, rising up again east of it (being negative, their flow opposes that of the current). In light of what was noted a little earlier about the "mirror force" which repels trapped particles from regions of intense magnetic field, one may well wonder how this force affects the flow of electrons which carry those currents.
Where electrons move upwards, the mirror force is no problem--on the contrary, it helps push the electrons away from Earth, towards weaker magnetic fields. However, it is a different story where electrons come down. With radiation belt particles, the mirror force keeps them safely away from the atmosphere--but here, those electrons better reach the upper layers of the atmosphere (where the current can continue horizontally to the other branch). If not, the electric circuit remains unclosed!
So what happens? In our homes no electric currents will not flow unless a sort of electric pressure pushes them on--a pressure we call "voltage." In the home it measures 110 volt, average value (actually it fluctuates, being AC). Space currents also have a voltage pushing them, something like 40,000 volts.
In the home, if an obstacle is placed in the circuit--an electric resistance, such as a lightbulb--the voltage concentrates there to helps push the current through the bottleneck. Same thing in space! There the bottleneck is the mirror force at the ends of the field line, and to overcome it, something like 5000-15,000 volts are concentrated there, pushing those electrons through. The voltage speeds them up to about 1/10 the velocity of light, and when they hit the top of the atmosphere, they produce a bright glow. That it the polar aurora!
Substorms and slingshots
But the bright arcs we see from the ground are usually associated with electrical currents flowing from Earth into space--to somewhere in space. (It may be confusing, but age-old convention has it that currents flow from (+) to (-). Therefore, when negative electrons come down, the currents they carry flow upwards.) To recapitulate, the electrons must overcome the "mirror force" of the strong magnetic field near Earth, which tries to keep them out, and they do so with a concentration of voltage.
And a proof exists. The mirror force is strongest near Earth, where the intensity of the magnetic field is greatest, so one expects the voltage to be greatest there, too. And since that voltage is the source of energy of auroral electrons, they should only acquire it pretty close to Earth. Indeed, satellites show that those electrons are only speeded up near Earth, in the last 2-5000 miles before they hit.
Not all such currents are directly connected to the solar wind. A very bright and violent type of auroral arcs--associated with the "auroral substorms" mentioned before--seem to be produced (in part or totally) inside the magnetotail. In such cases the tail behaves a bit like a slingshot. The solar wind pulls its field lines and stretches them to the limit. Then, when they get released and bounce back, they create (for a while--say half an hour to an hour) strong electric currents, and many, many auroral electrons.
The Sun gives out sunlight, and its hot corona produces the solar wind, the source of the aurora's energy. But the Sun is also magnetic--with a large-scale polar magnetic field (a bit like the Earth's), as well as sunspots, compact regions of concentrated magnetism. These too influence the aurora--through the interplanetary magnetic field, carried out from the Sun by the solar wind (won't go into that), and through occasional magnetic storms.
Most people have heard about sunspots--dark markings on the sun (a sunspot group is pictured on the left). Their number rises and falls with an irregular cycle of about 11 years, and some people have speculated (not too convincingly) that it matches the rise and fall of climate, the stock market, warfare and more.
That cycle was first noted by an amateur astronomer in 1843--more than two centuries after sunspots were first discovered (by Galileo and others). Astronomers had missed it completely, leaving it to Heinrich Schwabe, a German pharmacist and amateur astronomer. Schwabe searched for a planet orbiting close to the Sun inside the orbit of Mercury, tentatively named "Vulcan." You only see stars at night, so to detect one very close to the sun, you either need a total eclipse of the sun, or else you look for a dark spot crossing in front of the Sun's disk.
Schwabe looked for that spot every sunny day, and to distinguish it from sunspots (which rotate with the sun and move much more slowly), he kept tabs on sunspots as well. In 17 years he found no planet, but discovered instead that the number of sunspots rose and fell in a regular cycle.
As noted, sunspots turned out to be intensely magnetic. Associated with them are outbursts of magnetic energy, which fling fast clouds of plasma--faster than the usual solar wind--in all directions. One sign of outbursts are flares, sudden brightenings which also create a flood of x-rays. (These are not dangerous to astronauts, but the fast protons ejected at the same time can be). Another are "Coronal Mass Ejections," big bubbles of gas blown off the sun, reported in 1973 by astronauts on the space station "Skylab."
Whatever causes them, these clouds sometimes arrive near Earth and agitate its magnetosphere in a magnetic storm. The result, as noted, are bright auroras, pushed to locations much further from the poles. That is why, usually in years around the peak of the sunspot cycle, many more people get a glimpse of the polar aurora.
All the above is just a short and superficial overview of the science of the polar aurora--and I won't even try address the lore and literature. Let me conclude with two somewhat exotic aspects--artificial auroras and auroras on other planets.
Auroras, as was said, are caused by beams of electrons hitting the high atmosphere. So, if we mount an electron gun on the space shuttle or on some other spacecraft, and aim it down--can we create aurora?
In principle, yes, but in practice it's not easy to match Mother Nature. Remember, all auroras displays are at least 60 miles above our heads. It takes a lot of power to create a glow visible at that distance--especially, one as large as an auroral arc!. Experiments have been carried out--notably, the French-Soviet "Arkad" experiment above northern Russia (also some by the US), and spots of light were detected, but it took sensitive instruments to see them.
However, other more drastic ways also exist--such as exploding a nuclear bomb above the atmosphere, since a bomb produces great numbers of fast electrons. Such explosions were suggested by an unconventional Greek scientist named Nicholas Christofilos. He started out as an engineer designing elevator systems, but his real interest lay in magnetic fields and in the motion of ions and electrons in them. His interest led him to discover an important idea in the design of accelerators for nuclear research, known as "strong focusing." He wrote to Columbia University in the US, describing what he did, but scientists there did not pay enough attention to the ideas of an elevator engineer in Athens. They sent a polite reply and dropped the idea. A few years later, a Russian came up with a similar concept.
However, the US Air Force remembered Christofilos and invited him to this country. Because he was interested in the trapping of particles, Christofilos proposed creating an artificial radiation belt around Earth, by exploding a small nuclear bomb above the atmosphere.
No one suspected the existence of a permanent natural radiation belt, but some small nuclear bombs had been exploded by the US Air Force high in the atmosphere, near Hawaii. They created glows in the sky with the colors of the aurora, and people in Honolulu oohd and aahd over them--I have a dim memory that "Life" even ran a picture. So Christophilos prepared his bombs (to be flown on a rocket), while Russia prepared its Sputnik and Van Allen got ready for Explorers 1 and 3.
Sputnik was launched in October 1957, Explorer 1 was launched on the last day of January 1958, the newly discovered radiation belt was described that May, and the 3 bombs of "Project Argus" were exploded in August and September 1958, above an empty stretch of the South Atlantic. No observation broke the secrecy of the project, and no newspaper told about it at the time. But the bomb's electrons were guided by their magnetic field lines to their other end, near the Azores Islands, and produced a bright aurora which was seen by observers aboard ships deliberately stationed there. The "artificial radiation belts" from the bombs lasted about 2 weeks and were monitored by Explorer 4, built by Van Allen for that purpose.
Four years later the US Air Force decided to repeat the experiment on a grand scale west of Hawaii, using a hydrogen bomb, about 1000 times more powerful. This time the auroral electrons were guided towards Samoa--close to the equator, in a region where auroras had never been seen. But the explosion was too close to the equator, in a region where trapping was much more efficient. The radiation belt hung around for years, not weeks, and quickly destroyed 3 satellites (including a British scientific satellite NASA had just graciously launched), by degrading their solar panels and depriving them of power. The Soviet Union also exploded H-bombs in space, but the following year brought the international test ban and all such experiments ended.
NASA spacecraft have shown that the giant planets--Jupiter, Saturn, Uranus and Neptune--are all magnetic, and do have radiation belts. Jupiter, the biggest, outdoes them all--its "central magnet" is about 20,000 times stronger than ours. It also has auroras, photographed by the orbiting Hubble telescope (see here for a recent picture). Their origin (at least that of the stronger ones) is interesting.
As noted, Earth's aurora is associated with electric currents, and so is Jupiter's. Jupiter has 4 large moons (as big as ours or bigger), and the innermost one, Io, is a strange and hellish place, with its interior heated by tides, producing sulfur volcanoes and molten lakes. As a result, it (or the atmosphere around it) conducts electricity, and as Jupiter's magnetic environment rotates past it (just as the solar wind flows past Earth), electric currents are produced along the field lines linking it to Jupiter.
We know about those currents because Voyager 1 flew close to them in 1979 and observed the magnetic pattern they produced. And we know the observed auroras are due to those currents, because the structure of Jupiter's magnetic field has been mapped. Using that mapping to trace magnetic field lines from Io to the surface of the planet, one arrives exactly at the spots where auroras are seen.
One could go on and on, but even this quick tour should prove that the polar aurora is much more than a pretty show of lights. It also provides insight into the way physics and nature affect the space region around Earth.
A more extensive exposition on the magnetosphere, the origin of the aurora and the role of the Sun are found in "The Exploration of the Earth's Magnetosphere" on the world wide web. The home page (with an index of all web pages and links to them) is at
Auroras GaloreThe opening and closing shots of the aurora here were made by Dick Hutchinson. Dick lives in Circle, Alaska, on the Yukon river north-east of Fairbanks, in prime aurora territory. He enjoys photographing the aurora, and his collection of auroral images can give you a better feeling of "what the aurora looks like" than anything else I have seen on the web.
Other sites with auroral images:
Jan Curtis'es aurora images
An aurora site by the Andoya rocket range in northern Norway
Index page of "Exploration of the Earth's Magnetosphere",
an extensive overview of magnetospheric physics and its history.
Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: david("at" symbol)phy6.org .
Created 14 November 2002 | 0.823448 | 3.781175 |
Saturday, May 28, 2016
Credit: ESO/Marino et al.
Using 39 of the 66 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA), located 5000 metres up on the Chajnantor plateau in the Chilean Andes, astronomers have been able to detect carbon monoxide (CO) in the disc of debris around an F-type star. Although carbon monoxide is the second most common molecule in the interstellar medium, after molecular hydrogen, this is the first time that CO has been detected around a star of this type. The star, named HD 181327, is a member of the Beta Pictoris moving group, located almost 170 light-years from Earth.
Until now, the presence of CO has been detected only around a few A-type stars, substantially more massive and luminous than HD 181327. Using the superb spatial resolution and sensitivity offered by the ALMA observatory astronomers were now able to capture this stunning ring of smoke and map the density of the CO within the disc.
The study of debris discs is one way to characterise planetary systems and the results of planet formation. The CO gas is found to be co-located with the dust grains in the ring of debris and to have been produced recently. Destructive collisions of icy planetesimals in the disc are possible sources for the continuous replenishment of the CO gas. Collisions in debris discs typically require the icy bodies to be gravitationally perturbed by larger objects in order to reach sufficient collisional velocities. Moreover, the derived CO composition of the icy planetesimals in the disc is consistent with the comets in our Solar System. This possible secondary origin for the CO gas suggests that icy comets could be common around stars similar to our Sun which has strong implications for life suitability in terrestrial exoplanets.
The results were published in the journal Monthly Notices of the Royal Astronomical Society under the title “Exocometary gas in the HD 181327 debris ring” by S. Marino et al. | 0.883332 | 3.806425 |
For the most of the remainder of the course we will be discussing stars in one form or another. We will begin this discussion with the closest star, our Sun.
The Sun holds special significance to residents of Earth. It is our source of light, heat, and ultimately life. It is worshiped and celebrated, even to this day.
Some of the Sun's properties that have been measured are listed in Table 14.1.
We can see only the outermost part of the Sun. Scientists divide the Sun into a number of layers, both those we can't see and those we can.
The Sun is an enormous ball of hot gas held together by its gravity. At the center is the core. Around the core is a region called the radiative zone, and surrounding that is the convective zone. These are the inner parts of the Sun, mostly invisible to our instruments.
The outer atmosphere of the Sun is visible to our telescopes. The innermost layer of the atmosphere is called the photosphere. Above the photosphere is the chromosphere, and beyond that lies the corona.
The Sun is composed mostly of hydrogen and helium. The discovery that these are the primary consituents of the Sun was rather shocking initially. Today, we understand this fact, and it fits in very nicely with our understanding of what are the most abundant elements of the universe, also hydrogen and helium.
The photosphere is the opaque surface that astronomers see when they look at the Sun. (Reminder: As your mother told you, don't look directly at the Sun.) We cannot see past the photosphere, so this is what you might refer to as the "surface" of the Sun. (It is not a solid surface like the surface of the Earth, just the layer beyond which we cannot see.) The diameter of the Sun is generally taken as the diameter of the photosphere.
The photosphere is responsible for the light that we see from the Sun. Light generated inside the Sun is absorbed in the photosphere and re-emitted with a spectrum (color) determined by the temperature of the photosphere. This is "blackbody" radiation that we discussed in chapter 4. The radiation from the Sun tells us that the temperature of the photosphere is 5800K on average.
The chromosphere is a layer of gases beyond the photosphere. These gases are transparent to light, so the chromosphere is as well. Until recently, the chromosphere was only visible during a total solar eclipse. (It is a rather interesting coincidence that the Moon's size and distance is just perfectly matched to the Sun.) Observations of the chromosphere show mainly a bright red emission line due to hydrogen.
In 1868, a yellow emission line was seen in the chromosphere. This line didn't correspond to any element known at the time. Scientists realized that it must come from a new element (recall that the periodic chart had several "holes" in it from elements that had yet to be discovered) and that element was named helium after helios, the Greek word for Sun.
The transition region is a thin layer between the chromosphere and the corona where the temperature climbs (!) from about 10,000K to 1,000,000K.
The corona (latin for crown) has been known for centuries. It is clearly visible during a solar eclipse. The temperature in the corona is known because in the corona we see spectral lines of highly ionized atoms of iron, nickel, argon, ... It requires temperatures of a million degrees kelvin to produce these ionized states.
But the corona is very rare (low in density). It is about 10 billion times less dense than the Earth's atmosphere.
A stream of charged particles called the solar wind comes out from the Sun. The solar wind is responsible for the "blowing" of a comet's tail, and for the charged particles in the Earth's magnetosphere.
The Sun is not a static fixed object. It is constantly changing, with variable sunspots, coronal loops, and solar flares. Much of this seems to arise from the complicated dynamics going on inside the Sun. Scientists study the details of what can be seen in the photosphere of the Sun to gain a better understanding of the dynamics going on inside the Sun.
Sunspots are the most conspicuous features of the photosphere. Sunspots were noticed thousands of years ago. They appear as dark spots on the surface of the Sun. We now understand that they are dark because they are much cooler than the surrounding region, about 1500K cooler.
The number of sunspots on the Sun goes through an 11 year cycle. The changing magnetic field of the Sun drives the sunspot cycle. The connection between magnetic fields and sunspots is seen in the high magnetic fields present in sunspots (Figure 14.15).
Above the photosphere, activity is seen by looking for emission lines of atoms. A number of different types of features are seen:
Something we are most certain of is that the Sun will rise tomorrow. Yet, we now understand that the Sun is not constant from year to year. The Sun undergoes an 11 year cycle of sunspots, and on longer time scales, it undergoes changes in overall activity -- that is, the amount of light and heat produced. While these changes are small, about a tenth of a percent (0.1%), this is enough to produce periods of unusual cold or heat. The period 1645 to 1715 is documented to be a period of unusually low sunspot activity and unusually cold temperatures in Europe (the "little ice age").
Observations of other stars indicate that it is normal for their activity (measured as something called luminosity) changes by 0.3 percent, or as much as 1 percent. It may be normal for the Sun's output to vary by similar amounts. | 0.825137 | 3.838507 |
Pairs of black holes circling around each other, getting closer & closer to crashing together, may create ripples in space & time — yet new research suggests that these ripples are milder than previously thought. Â
A new paper searching for signs of these space-time ripples — known as gravitational waves — came up empty, suggesting that theorists need to rethink their models of these monster pairs. The new work affects searches for gravitational waves using pulsars — dead stars that appear to create regular pulses of light, not unlike a lighthouse.
Gravitational waves were originally predicted by Albert Einstein, yet no one has ever found direct evidence they exist. The new work will assist scientists as they move forward in their search; & down the road, these searches could illuminate details approximately merging galaxies in the universe. [The Search for Gravitational Waves (Gallery)]
A boat on the ocean
Sometimes looking for objects in the universe is like looking for boats on the ocean at night. Sitting on the shore under the stars, it can be effortless to see a boat with a spotlight, or red warning lights. But what approximately a boat that has no lights, or is hidden by a rocky outcropping? These invisible boats leave behind another bit of evidence as they pass by: The waves they make in the water. Even in the dark, someone sitting on the shore can hear or feel a sudden surge in the size of the waves, which signals the passing of a vessel.
In this same way, scientists want to detect the dark & hidden black holes that lurk throughout the universe by looking for the waves they create in space & time.
It was Einstein who said that space & time are not two independent features of the universe, yet are woven together into a single fabric. Strong gravitational forces, like two black holes spiraling toward each other, can create gravitational waves in this fabric.
Vikram Ravi is a postdoctoral fellow at the California Institute of Technology. He's moreover part of the Parkes Pulsar Timing Array, which was established to search for gravitational waves through an indirect method — the way they interrupt the light from pulsars.
Pulsars are dense remnants left behind after a star explodes into a supernova. Pulsars emit beama of light out into space in two opposite directions — just like some lighthouses. Pulsars moreover spin — like some lighthouses — which means from Earth, these pulsars often look as though their light is pulsing on & off. It turns out these compact little flashlights "pulse" with incredible regularity, so much so that they're used as cosmic clocks.
Scientists with the Parkes Pulsar Timing Array want to look for interruptions in the regular pulse of these pulsars caused by gravitational waves. Put simply, if a gravitational wave passed by a pulsar, it could warp the space-time between the pulsar & Earth. This could cause a hiccup in the timing of the otherwise extremely regular light pulses.
If there were only a few sources of gravitational waves in the universe, it might be effortless to detect a single such blip in the light from a pulsar. But according to Ravi, scientists think there are many sources of gravitational waves all over the universe. These come together to create a constant, noisy rippling in the space-time fabric.
To visualize this, consider a pond that it totally still on its surface. A single pebble dropped into the pond will cause ripples that can easily be traced back to the source. But during a rainstorm, many droplets of water disturb the pond's surface & create a minimum amount of rippling across the entire surface.
According to Ravi, a large contributor to this background would be black hole pairs orbiting each other, slowly winding down until they eventually merge together into one. Since most galaxies are thought to have black holes at their centers, this kind of black hole binary would likely occur whenever two galaxies merged together.Â
"Galaxies in the universe today we think formed from the mergers of smaller galaxies. And that's […] what we see – we see plenty of galaxy mergers," Ravi said. He added that this moreover fits with current theories approximately the evolution of the universe. "So because we think that mergers between galaxies occur all over the universe, we think that there should be many of the orbiting binary black holes. And so the gravitational waves emitted by all of them, in principle, should form a background."
Ravi & colleagues studied a group of pulsars for 11 years, eventually focusing on four of them, looking for the background gravitational wave signal. Theoretical work has suggested that the CSIRO Parkes radio telescope observatory in Australia should be sensitive enough to detect this background. Ravi said he & his colleagues reached that level of sensitivity, "but there's no signal." Meaning, if it does exist, it is quieter than what the theories predicted it should be.
"So what it means is that the theorists — including me — need to come up with better models," Ravi said. "They need to think a bit harder approximately what the gravitational wave signal may actually look like."
These models offer some insight into the physics involved with these circling black holes, such as how much of their energy goes into the gravitational waves they produce. With the new results, the models must incorporate an upper limit on how strong those space-time ripples can be, so perhaps the amount of energy put into the surrounding environment (rather than into the gravitational waves) is higher than previously thought. Improved models could donate scientists ideas for how to look for these dancing double black holes, & in the long term, they could provide an estimate of how many of these black hole pairs exist in the universe, according to Ravi. That would reveal something approximately how many galaxies in our universe are actually blended families, made from the merging of two smaller galaxies. [When Galaxies Collide: Photos of Great Galactic Crashes]
Parkes is not the only program searching for these gravitational wave hiccups in pulsars. Together, these programs collaborate as part of the International Pulsar Timing Array, & by combining data, these programs may have a better chance of finding a gravitational wave signal.
Chung-Pei Ma, a professor of astronomy at the University of California at Berkeley, who was not involved with the new research, said the work "presents the tightest yet limit on gravitational waves from merging binary black holes. This limit is now stringent enough to start constraining some models for how galaxies & black holes were assembled over the cosmic history. There is still wiggle room left for the theorists & model builders, yet the air is getting a bit thinner & everyone has to work a bit harder to explain this new upper limit."
While the researchers are hoping to find a positive gravitational wave signal soon, there is plenty of work to be done in preparation for that discovery.
"It's thrilling that we're able to actually to say something meaningful approximately the universe using gravitational waves," Ravi said.
The new work was led by Ryan Shannon at the Commonwealth Scientific & Industrial Research Organization (CSIRO) in Australia, & appeared in today's (Sept. 24) online issue of the journal Science. Ravi completed the research while working at the Swinburne University of Technology in Australia.
Follow Calla Cofield @callacofield.Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.
How Gravitational Waves Work (Infographic) Pulsar’s Dramatic Morph Caught by Space Telescope | Video Einstein's Theory of Relativity Explained (Infographic) Copyright 2015 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.810762 | 4.014011 |
Scientists hail comet water finding
Water - but not as we know it - has been found around the comet that the Rosetta probe landed on last month.
The discovery, made by an instrument on board the Rosetta spacecraft, calls into question a leading theory about how the Earth got its oceans.
The finding suggests that rocky asteroids rather than icy comets may have been chiefly responsible for bringing water to Earth early in its history.
The Rosetta mission hit the headlines when the spacecraft deployed a robot lander, Philae, that made a dramatic descent to comet 67P/Churyumov-Gerasimenko (67P) on November 12.
Data from the lander, which bounced twice before coming to rest near the wall of a crater, are yet to yield scientific results.
But an instrument on the orbiting Rosetta mothership has come up with a surprise after analysing water vapour enveloping the comet.
Unlike the Earth's oceans, the vapour largely consists of water with a different atomic flavour containing deuterium, the "heavy" isotope of hydrogen. The amount of deuterium compared with normal hydrogen in the comet's water is three times greater than it is in water on Earth.
This suggests that so-called Jupiter-family comets, such as 67P, cannot be assumed to have created the oceans on Earth.
In contrast, meteorites falling on Earth that originate from the asteroid belt between Mars and Jupiter tend to match the composition of Earth ocean water.
Professor Kathrin Altwegg, principal investigator for Rosetti's Rosina mass spectrometer that carries out chemical analysis based on light signals, said: "Our finding .. rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for the Earth's oceans."
Members of the Rosetta team reported the results in the journal Science.
The European Space Agency's British Rosetta project scientist Dr Matt Taylor said: "We knew that Rosetta's in situ analysis of this comet was always going to throw up surprises for the bigger picture of Solar System science, and this outstanding observation certainly adds fuel to the debate about the origin of the Earth's water.
"As Rosetta continues to follow the comet on its orbit around the Sun throughout next year, we'll be keeping a close watch on how it evolves and behaves, which will give us unique insight into the mysterious world of comets and their contribution to our understanding of the evolution of the Solar System."
Scientists have long wondered about the oceans because the Earth was so hot when it formed 4.6 billion years ago that all its original water should have boiled off.
Yet today, two thirds of the Earth's surface is covered in water. The most likely explanation is that after the Earth cooled down, collisions with water-bearing objects such as comets or asteroids filled up the ocean basins. | 0.85373 | 3.798538 |
Pluto was looking more and more like a goner today as astronomers meeting in Prague continued to debate the definition of a planet.
“I think that today can go down as the ‘day we lost Pluto,’ ” Jay Pasachoff of Williams College said in an e-mail message from Prague.
Under fire from other astronomers and the public, a committee appointed by the International Astronomical Union revised and then revised again a definition proposed last week that would have expanded the number of official planets to 12, locking in Pluto as well as the newly discovered Xena in the outer solar system, as well as the asteroid Ceres and Pluto’s moon Charon.
The new definition offered today would set up a three-tiered classification scheme with eight “planets”; a group of “dwarf-planets” that would include Pluto, Ceres, Xena and many other icy balls in the outer solar system; and thousands of “smaller solar system bodies,” like comets and asteroids.
The bottom line, said Owen Gingerich, the Harvard astronomer who is chairman of the I.A.U.’s planet definition committee, is that in the new definition, “Pluto is not a planet.”Continue reading the main story
“There’s not happiness all around, believe me,” he added.
The new proposal was hashed out in a couple of open meetings, the first of which was described by participants as tumultuous, and the second more congenial. Astronomers are supposed to vote on this or some other definition on Thursday, but whether a consensus is emerging depends on whom you talk to. Some astronomers expressed anger that the original definition of planet had been developed in isolation and then dropped on them only a week before the big vote. Others continued to question whether it was so important to decide the question now at all.
Among its defects, some astronomers say, the newer definition abandons any pretense of being applicable to other planetary systems beyond our own solar system.
To many astronomers, Pluto’s tiny size and unusually tilted orbit make it a better match to the icy balls floating in the outskirts of the solar system in what is known as the Kuiper Belt than to the conventional planets like Jupiter and Mars. The issue has been forced on astronomers by the discovery of such a ball even larger than Pluto, nicknamed Xena by its discoverer, Mike Brown of the California Institute of Technology.
If Pluto is a planet, so should be Xena, Dr. Brown has argued.
The committee’s original prime criterion was roundness, meaning that a planet had to be big enough so that gravity would overcome internal forces and squash it into a roughly spherical shape. But a large contingent of astronomers, led by Julio Fernandez of the University of the Republic in Montevideo, Uruguay, has argued that a planet must also be massive enough to clear other objects out of its orbital zone. Dr. Gingerich admitted, “They are in control of things.”
So the newest resolution includes the requirement for orbital dominance as a condition for full-fledged planethood, Dr. Gingerich said. That knocks out Pluto, which crosses the orbit of Neptune, and Xena, which orbits among the icy wrecks of the Kuiper Belt, and Ceres, which is in the asteroid belt.
“Vociferous objectors have said they could accept this,” Dr. Gingerich said.
Reached in his office at Caltech, Dr. Brown, who as the discoverer of Xena has the most to lose by its and Pluto’s demotion, said he thought he could live with the new proposal. “It essentially demotes Pluto to something other than a real planet, which is reasonable,” he wrote in an e-mail.
Dr. Gingerich cautioned that there were many things still to be sorted out. For example, the International Astronomical Union might consider creating a special name for Pluto and other dwarf-planets, like Xena and others yet to be discovered, that dwell out beyond Neptune. If it did, he said that “plutonians” seemed like a likelier choice than the previous suggestion, “plutons.” That term was protested by geologists, who pointed out that it was already used in earth science for nuggets of molten rock that have solidified and reached the surface.
But with two more days before the scheduled vote, there was no guarantee Pluto would not make a comeback and the definition of planethood be rewritten again.
“Some people think that the astronomers will look stupid if we can’t agree on a definition or if we don’t even know what a planet is,’’ Dr. Pasachoff said. “But someone pointed out that this definition will hold for all time and that it is more important to get it right.”Continue reading the main story | 0.872373 | 3.060903 |
Three astronomers won the Nobel Prize in Physics on Tuesday for discovering that the universe is apparently being blown apart by a mysterious force that cosmologists now call dark energy, a finding that has thrown the fate of the universe and indeed the nature of physics into doubt.
The astronomers are Saul Perlmutter, 52, of the Lawrence Berkeley National Laboratory and the University of California, Berkeley; Brian P. Schmidt, 44, of the Australian National University in Canberra; and Adam G. Riess, 41, of the Space Telescope Science Institute and Johns Hopkins University in Baltimore.
“I’m stunned,” Dr. Riess said by e-mail, after learning of his prize by reading about it on The New York Times’s Web site.
The three men led two competing teams of astronomers who were trying to use the exploding stars known as Type 1a supernovae as cosmic lighthouses to limn the expansion of the universe. The goal of both groups was to measure how fast the cosmos, which has been expanding since its fiery birth in the Big Bang 13.7 billion years ago, was slowing down, and thus to find out if its ultimate fate was to fall back together in what is called a Big Crunch or to drift apart into the darkness.Continue reading the main story
Instead, the two groups found in 1998 that the expansion of the universe was actually speeding up, a conclusion that nobody would have believed if not for the fact that both sets of scientists wound up with the same answer. It was as if, when you tossed your car keys in the air, instead of coming down, they flew faster and faster to the ceiling.
Subsequent cosmological measurements have confirmed that roughly 70 percent of the universe by mass or energy consists of this antigravitational dark energy that is pushing the galaxies apart, though astronomers and physicists have no conclusive evidence of what it is.
The most likely explanation for this bizarre behavior is a fudge factor that Albert Einstein introduced into his equations in 1917 to stabilize the universe against collapse and then abandoned as his greatest blunder.
Quantum theory predicts that empty space should exert a repulsive force, like dark energy, but one that is 10 to the 120th power times stronger than what the astronomers have measured, leaving some physicists mumbling about multiple universes. Abandoning the Einsteinian dream of a single final theory of nature, they speculate that there are a multitude of universes with different properties. We live in one, the argument goes, that is suitable for life.
“Every test we have made has come out perfectly in line with Einstein’s original cosmological constant in 1917,” Dr. Schmidt said.
If the universe continues accelerating, astronomers say, rather than coasting gently into the night, distant galaxies will eventually be moving apart so quickly that they cannot communicate with one another and all the energy will be sucked out of the universe.
Edward Witten, a theorist at the Institute for Advanced Study, Einstein’s old stomping grounds, called dark energy “the most startling discovery in physics since I have been in the field.” Dr. Witten continued, “It was so startling, in fact, that I personally took quite a while to become convinced that it was right.”
He went on, “This discovery definitely changed the way physicists look at the universe, and we probably still haven’t fully come to grips with the implications.”
Dr. Perlmutter, who led the Supernova Cosmology Project out of Berkeley, will get half of the prize of 10 million Swedish kronor ($1.4 million). The other half will go to Dr. Schmidt, leader of the rival High-Z Supernova Search Team, and Dr. Riess, who was the lead author of the 1998 paper in The Astronomical Journal, in which the dark energy result was first published.
All three astronomers were born and raised in the United States; Dr. Schmidt is also a citizen of Australia. They will get their prizes in Stockholm on Dec. 10.
Since the fate of the universe is in question, astronomers would love to do more detailed tests using supernovas and other observations. So they were dispirited last year when NASA announced that cost overruns and delays on the James Webb Space Telescope had left no room in the budget until the next decade for an American satellite mission to investigate dark energy that Dr. Perlmutter and others had been promoting for almost a decade. Indeed on Tuesday the European Space Agency announced that it would launch a mission called Euclid to study dark energy in 2019.
Cosmic expansion was discovered by Edwin Hubble, an astronomer at the Mount Wilson Observatory in Pasadena, Calif., in 1929, but the quest for precision measurements of the universe has been hindered by a lack of reliable standard candles, objects whose distance can be inferred by their brightness or some other observable characteristic. Type 1a supernovae, which are thought to result from explosions of small stars known as white dwarfs, have long been considered uniform enough to fill the bill, as well as bright enough to be seen across the universe.
In the late 1980s Dr. Perlmutter, who had just gotten a Ph.D. in physics, devised an elaborate plan involving networks of telescopes tied together by the Internet to detect and study such supernovae and use them to measure the presumed deceleration of the universe. The Supernova Cosmology Project endured criticism from other astronomers, particularly supernova experts, who doubted that particle physicists could do it right.
Indeed, it took seven years before Dr. Perlmutter’s team began harvesting supernovae in the numbers it needed. Meanwhile, the other astronomers had formed their own team, the High-Z team, to do the same work.
“Hey, what’s the strongest force in the universe?” Robert P. Kirshner of the Harvard-Smithsonian Center for Astrophysics, and a mentor to many of the astronomers on the new team, asked a reporter from this newspaper once. “It’s not gravity, it’s jealousy,” Dr. Kirshner said.
In an interview with The Associated Press, Dr. Perlmutter described the subsequent work of the teams as “a long aha.” The presence of dark energy showed up in an expected faintness on the part of some distant supernovae: the universe had sped up and carried them farther away from us than conventional cosmology suggested.
As recounted by the science writer Richard Panek in his recent book, “The 4% Universe, Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality,” neither team was eager to report such a strange result.
In January 1998, Dr. Riess interrupted preparations for his honeymoon to buck up his comrades. “Approach these results not with your heart or head but with your eyes,” he wrote in an e-mail. “We are observers after all!”
In the years since, the three astronomers have shared a number of awards, sometimes giving lectures in which they completed one another’s sentences. A Nobel was expected eventually.
“No more waiting!” Dr. Kirshner said Tuesday.
An earlier version of this article incorrectly stated the publication in which Adam G. Riess's 1998 paper on dark energy appeared. It was The Astronomical Journal, not Science. The article also stated incorrectly the amount of the prize. It is 10 million Swedish kronor ($1.4 million). | 0.806616 | 3.57432 |
January 10, 2008
Four Stars Found in Amazingly Tight Bunch
AUSTIN, Texas — A quartet of stars has been
discovered in an intimate cosmic dance, swirling around each other within a
region about the same as Jupiter's orbit around the sun.
say a gaseous disk might have once engulfed and pushed the stars into their
the stellar system was thought to be a single star dubbed BD -22°5866. Now,
research presented here today at a meeting of the American Astronomical Society
reveals the pinpoint of light is a rare system of four closely orbiting stars.
The group is located about 166 light-years from the sun. In our sky, they are
just south of the constellation Aquarius.
Each of the
stars is about half as massive as the sun and older than 500 million years. The
sun, by comparison, is 4.6 billion years old.
stars form as part of a multiple-star
system, the new findings could have implications for understanding the
evolution of stars.
Shkolnik of the University of Hawaii's Institute for Astronomy and NASA
Astrobiology Institute and colleagues spotted the foursome while surveying
hundreds of nearby low-mass stars with the Keck I telescope and the
Canada-France-Hawaii telescope, both on the summit of Mauna Kea.
At the time
of the observations, two of the stars were orbiting each other at 300,000 mph
(483,000 kilometers per hour), taking a under a mere five days to complete an
orbit. The other couple had an orbit speed of 120,000 miles per hour (193,000
kilometers per hour) and takes about 55 days for a complete jaunt around their
common gravitational midpoint in space.
pair has an orbit radius of at most .06 astronomical units (AU), where one AU
is the average distance between Earth and the sun. The second pair has a
maximum radius of .26 AU.
pairs also promenade each other in less than nine years with a maximum radius
of just 5.8 AU. Jupiter, to compare, is 5.2 AU from the sun.
researchers say that fewer than 1 in 2,000 stars observed might be involved in
extraordinarily tight configuration of this stellar system tells us that there
may have been a single gaseous disk that forced them into such small orbits
within the first 100,000 years of their evolution," Shkolnik said,
"as the stars could not have formed so close to one another."
the spin energy of the more rapidly rotating pair, mixed with the gravitational
interaction between the two pairs, has pushed the other pair farther away over
one point early in its history, it was even closer than we see now,"
Shkolnik told SPACE.com.
research has been submitted to the Astrophysical Journal Letters. | 0.928307 | 3.790952 |
The Ring Nebula (M 57) is a planetary nebula about 2300 light years away from us. This is how it looks when a star blows its outer layers at the end of the life. If the star is not big enough to explode in a supernova, it will eject some of its mass as in the case of M 57, the Ring Nebula. The star in the centre of the nebula can still be seen, but it is passing through the last stage of its stellar evolution and is soon to become a white dwarf. The star in the centre is still bright enough to illuminate the whole scene.
The colours are more or less true colours; it's a composite image from Hubble with different colour filters. The blue colour is very hot helium, green is ionised oxygen and red is ionized nitrogen. The temperature is higher close to the centre, the central star has a surface temperature of 120 000 °C (216 000 °F) and will slowly cool down in the future. Currently it still shines 200 times brighter than the Sun. M 57's inner ring (which is visible in this image) has a diameter of roughly one light year and was blown off the star 5000 to 6000 years ago. It's a perfect example of how our Sun will look in about 5 or 6 billion years. Of course, by then we have to leave the scene in time - as beautiful as it may look - and find ourselves another planet in the Milky Way.
Read more about: | 0.803555 | 3.068603 |
Goddard's Chief Scientist Talks About the 'Supermoon' Phenomenon
Dr. James Garvin, chief scientist at NASA's Goddard Space Flight Center, answers your questions about the 'supermoon' phenomenon.
Question: What is the definition of a supermoon and why is it called that?
'Supermoon' is a situation when the moon is slightly closer to Earth in its orbit than on average, and this effect is most noticeable when it occurs at the same time as a full moon. So, the moon may seem bigger although the difference in its distance from Earth is only a few percent at such times.
It is called a supermoon because this is a very noticeable alignment that at first glance would seem to have an effect. The 'super' in supermoon is really just the appearance of being closer, but unless we were measuring the Earth-Moon distance by laser rangefinders (as we do to track the LRO [Lunar Reconnaissance Orbiter] spacecraft in low lunar orbit and to watch the Earth-Moon distance over years), there is really no difference. The supermoon really attests to the wonderful new wealth of data NASA's LRO mission has returned for the Moon, making several key science questions about our nearest neighbor all the more important.
Are there any adverse effects on Earth because of the close proximity of the moon?
The effects on Earth from a supermoon are minor, and according to the most detailed studies by terrestrial seismologists and volcanologists, the combination of the moon being at its closest to Earth in its orbit, and being in its 'full moon' configuration (relative to the Earth and sun), should not affect the internal energy balance of the Earth since there are lunar tides every day. The Earth has stored a tremendous amount of internal energy within its thin outer shell or crust, and the small differences in the tidal forces exerted by the moon (and sun) are not enough to fundamentally overcome the much larger forces within the planet due to convection (and other aspects of the internal energy balance that drives plate tectonics). Nonetheless, these supermoon times remind us of the effect of our 'Africa-sized' nearest neighbor on our lives, affecting ocean tides and contributing to many cultural aspects of our lives (as a visible aspect of how our planet is part of the solar system and space). | 0.811078 | 3.365984 |
In the afternoon of Saturday, December 6, 2014, at 12 noon Pacific Standard time, the spacecraft New Horizons started the process that would wake itself from its imposed nine-year hibernation as it prepares to expand our knowledge of the most outer planet in our solar system. After an hour and a half, the spacecraft beamed a radio signal to our home planet that it had finished turning itself back on, this time for the final time. Although two-thirds of New Horizons time was spent in hibernation, a few instruments were left on in order to collect data about dust particles and solar winds as the spacecraft moved through space. A beacon had also been attached to the New Horizons, giving scientists back on Earth access to the spacecraft’s movements as it whisked through the dark emptiness.
Although the New Horizons spacecraft had taken only an hour and a half to turn itself on, and had relayed the information right away back to Earth, because of the distance of the spacecraft from Earth, 2.9 billion miles from our home planet, it took the signal four hours and 26 minutes to reach the Canberra, Australia, Deep Space Network run by NASA. The signal had been travelling at the speed of light, to put the distance into perspective. Operators of the New Horizons mission confirmed at 6:53 p.m. Pacific Standard Time that the spacecraft was in what they called “active mode.” Over the past nine years, scientists had woken up the spacecraft twice a year to check that its instruments and maneuvering were working, to ensure that the spacecraft would be able to fly around Pluto. However, this wake up was special, as it marked the last time that New Horizons would need to be put back in to hibernation as the spacecraft prepares to expand our knowledge of Pluto.
January 15, 2015 marks the day that New Horizons will start to observe Pluto. Right now, the spacecraft sits 162 million miles away from Pluto, and at its closest pass of the largely unknown planet will fly by at only 7,700 miles from the surface of Pluto. This historic event will take place in July of 2015. Scientists are hoping to get some clear, precise information from New Horizons about little known Pluto. Since its discovery in 1930, very little information about the dwarf planet has become known. During the 1990’s, astronomers began to realize that Pluto was not a lone planet in a distant orbit, but was rather part of a community of over 1,000 other bodies of objects making up what they call the Kuiper Belt. This made the classification of Pluto as a planet unclear, which astronomers are hoping to clear up with the expanding of our knowledge of the planet with the New Horizons spacecraft as it prepares itself for the mission ahead.
Since no one actually knows what Pluto will look like, scientists, astronomers and those who love the exploration of space will be excited to view the pictures that New Horizons will be sending back to Earth. As well as taking pictures of the planet, the spacecraft will also be using other various instruments to map the planets topography, study the chemical makeup of the planet, as well as look for rings among other studies. The pictures that New Horizons will be sending back as the spacecraft prepares to expand our knowledge of Pluto will be much higher resolution than those taken with the Hubble Telescope. Also, NASA announced more targets it hopes to use New Horizons to inspect after it passes Pluto and enters the rest of the Kuiper belt. Even after the work with Pluto is finished, New Horizons will still be used to explore other unknowns in our solar system.
By: Korrey Laderoute
Photo courtesy of Peter – Creativecommons Flickr License | 0.80799 | 3.51444 |
Two Families of Comets Found Around Nearby Star
The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.
Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.
Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”
For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.
To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.
The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.
This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet , and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.
The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris .
The exocomets of the second family are much more active and are also on nearly identical orbits . This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.
Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”
Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped inorbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star — close to where the planet Beta Pictoris b was discovered. | 0.892207 | 3.940798 |
By Andy Veh, for the Redoubt Reporter
Days are getting longer and nights are getting shorter, thus this will be my last column before fall. The winter constellations, Orion, Gemini, Taurus, Canis Major and Auriga with all their bright stars, are now visible in the west, setting during the late evening.
Leo, with its bright star Regulus, is speeding across the sky, so I perceive Leo as the harbinger of spring. When it appears in the east, winter’s end will soon be here, and when it reaches the western horizon, flowers are in full bloom and deciduous will have regained their leaves. In addition, the summer triangle comprised of the bright stars Vega, Deneb and Altair reappears in the Northeast.
Planets visible in the evening and all night include:
Saturn is visible all night long, forming an acute triangle with Spica and red Arcturus. Look for them near the Southeastern horizon. Saturn doesn’t stand out, as it is about as bright as the other two stars. Find them by following the Big Dipper’s handle, which curves toward red Arcturus, then beneath it find Spica on the right and Saturn on the left, completing that acute, almost right triangle. The full moon appears to Saturn’s lower right April 25.
Jupiter is visible, next to Taurus’ red giant Aldebaran and with the star cluster Pleiades nearby. It appears until late evening, moving from the south to the northwest, setting around midnight. It is joined by the waxing crescent moon April 14. Sky & Telescope’s April edition states that they “pair beautifully.”
Jupiter is the brightest wanderer in the sky. Venus is in superior conjunction (on the other side of the sun) and will not be visible again until fall of this year. Once it emerges from behind the sun (in April), it’s already late spring and the evenings are too bright for too long, so this evening planet is too close to the Alaska horizon.
All other planets — Mercury, Mars, Uranus and Neptune — appear too close to the sun, so that they can’t be seen against the bright daytime sky.
The Lyrid meteor shower can be viewed in the early morning hours of April 22. The constellation Lyra with its bright star Vega is high above the southern horizon. As the meteors seem to emanate from that spot in the sky, look all around Lyra.
Comet Panstarrs is visible after sunset in the northwest, low on the horizon. But don’t be disappointed if it doesn’t show very well. Probably binoculars are needed.
Andy Veh is an associate professor of physics, math and astronomy at Kenai Peninsula College. | 0.918518 | 3.202995 |
NASA has confirmed that Voyager 1, which was launched on September 5 1977, has finally left the Solar System. Voyager 1 becomes the first manmade object to leave the Solar System, and in 40,000 years it will come within 1.7 light years of star AC+793888, before continuing on its millions-of-years journey to the core of the Milky Way.
Before leaving the Solar System, Voyager 1 was located in the heliopause, a region of space between the heliosphere and interstellar space. In April, Voyager started to detect electron plasma oscillations with around 40 times more energy than inside the heliosphere. Basically, the universe is full of electron-dense plasma that has been ejected from supernova stars — but the heliosphere, a bubble of charged particles emitted by the Sun, stops this plasma from entering the Solar System. “The increased electron density is very close to the value scientists expected to find in the interstellar medium,” says Don Gurnett of the University of Iowa and Voyager project scientist, co-author of the research paper that finally decided that Voyager had left the Solar System. Through extrapolation of data from the fall of 2012, and the spring of 2013, the paper reports that Voyager 1 technically left the Solar System on August 25 2012.
With Voyager 1 now outside the Solar System, it should return some interesting data that will — at long last — empirically inform us about the interstellar medium. There is also some science to be gathered by Voyager 2, which also launched in 1977, and will soon leave the Solar System via a different route. Voyager 1 has a broken instrument which hindered its ability to fully study the heliosphere and heliopause; Voyager 2 has a full complement of functioning instruments. For more information on Voyager 1, see a previous story that we wrote when we thought it had left the Solar System, but actually it hadn’t.
At 36 years of age, Voyager 1 is now 11.6 billion miles away from the Sun — the most distant human-made object. Even so, 11.6 billion miles is still just 1/500th (or 0.002%) of a light year. At its current pace (38,610 mph or 62,136 kmh), it would take Voyager 1 roughly 200,000 years to reach the nearest possibly habitable planet, Tau Ceti e. If we want to colonize other planets, we either need to leave very soon, or develop a method of traveling much, much faster. | 0.828316 | 3.811291 |
LOS ANGELES (AP) — Just in time for Valentine’s Day.
After eyeing a comet for the past four years, a NASA spacecraft will finally make its move.
The Stardust craft is expected to fly within 125 miles of comet Tempel 1 on Valentine’s night, snapping pictures of the surface.
In 2005, Tempel 1 received a not-so-loving visit from another NASA probe named Deep Impact, which fired a copper bullet into the comet on the Fourth of July that sparked cosmic fireworks and excavated a crater. The high-speed crash hurled out so much dust and debris that Deep Impact failed to see the manmade hole even as it beamed back dazzling pictures of other surface features.
Scientists hope to get a second chance with Stardust, which is expected to pass near the 2005 bull’s-eye.
“I’m going to be sleepless on Valentine’s Day and sending a lot of love to this comet,” quipped mission co-investigator Pete Schultz of Brown University.
Comets, irregular bodies of ice and dust that orbit the sun, are frozen leftover building blocks of the solar system, which formed when a huge cloud of gas and dust collapsed about 4.5 billion years ago. Studying comets could yield clues to the birth of the solar system.
Tempel 1 is not the first comet that Stardust will get cozy with. In 2004, it swooped past comet Wild 2 and captured a bounty of interstellar and comet dust that it later returned it to the Utah desert — the first time that a spacecraft fetched particles from a comet back to Earth.
Stardust has traveled 3 1/2 billion miles since launching from Cape Canaveral, Fla., in 1999. Because it had ample fuel after visiting Wild 2, NASA decided to recycle it for another job. For the past four years, Stardust had its sight on Tempel 1, adjusting its path several times and even using gravity assist from Earth to put it on target for a Valentine’s date.
“It’s got some mileage on it, but it’s still working well,” said project manager Tim Larson of the NASA Jet Propulsion Laboratory, which manages the encore mission.
Unlike the trip to Wild 2, which cost $300 million, Tempel 1 at $29 million will be a cheap date by space mission standards.
Stardust will navigate autonomously during closest approach, which is expected to occur at 8:37 p.m. PST Monday. Scientists should know within 20 minutes if the flyby was successful.
During the encounter, Stardust will take dozens of high-resolution images of Tempel 1’s nucleus and coma, a fuzzy halo of gas and dust. It will also use its two dust detectors to measure the size and makeup of dust grains. The spacecraft is equipped with a protective shield to deflect potentially dangerous particles as it zips past.
Principal investigator Joe Veverka of Cornell University said he looks forward most to finally seeing the impact crater created by Deep Impact, but would be just as satisfied with seeing new surface features. One of the reasons scientists can’t guarantee that Stardust will image the crater is because they’ve had to guess which side of the comet the craft will see as it approaches.
Stardust’s antenna won’t be pointed at Earth during the mission so the public will not be able to see the encounter in real time. After passing Tempel 1, Stardust will turn toward Earth and start relaying data — a process that will take 12 hours to complete.
Unfortunately, Stardust won’t have enough fuel to flirt with another comet after this.
(© Copyright 2011 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.) | 0.857375 | 3.053123 |
Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.
- Lagrange Points – Detailed explanation including mathematics and lots of links
- The Lagrange Points – including a derivation of Lagrange’s result
- What are Lagrange Points? – ESA
- Lagrangian Points
Langranian Point Missions
- Advanced Composition Explorer (ACE) (L1)
- Genesis (L1)
- International Sun/Earth Explorer 3 (ISEE-3) (L1)
- Solar and Heliospheric Observatory (SOHO) (L1)
- Wilkinson Microwave Anisotropy Probe (WMAP) (L2)
- Herschel Space Observatory (L2)
- James Webb Space Telescope (JWST) (L2)
- Planck Satellite (L2)
Using Lagrange Points For Transportation
- The Interplanetary Superhighway – using Lagrange points to navigate the solar system
- Navigating Celestial Currents – Erica Klarreich (Science News 167 p. 250)
- Interplanetary Superhighway & The Origins Program – Lo, M.W. (2001) [PDF]
- The Lunar L1 Gateway: Portal to the Stars and Beyond – Lo, M. W., S.D. Ross (2001) [PDF]
Fraser Cain: Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.
Before we get on to it, let’s talk about pronunciation. I said it Lagr-ahunge points. Is that okay?
Dr. Pamela Gay: I have heard it said Lagr-ahunge points, Lagr-ahungian points, Lug-range points and Lug-range-ian points. So you know – go with it. Say whatever your local dialect dictates is correct.
Fraser: They’re acceptable.
Pamela: They’re all acceptable.
Fraser: All right. Maybe someone from France can jump in and give us the most correct pronunciation.
So, where do these come from?
Pamela: The basic idea is if you have a two-body system with two giant things – where giant can be defined on small scales, such as the Moon and the Earth would qualify, the Earth and the Sun would qualify – then you throw in something small (a test particle, a frozen pea, a satellite), you can look to see how the smaller object is going to gravitationally interact with the larger object.
Fraser: The point being this object isn’t going to be pulling at the other two objects with its gravity. Its gravity is negligible in the situation.
Pamela: Yeah. It has no pull on the Earth or the Sun – no pull on the two giant objects that we’re worried about.
When you start to probe all the different places you can stick this test particle, there are some places that when you stick it there, it stays. In general, if you take an object and you put it on an orbit around the Sun that’s bigger than the Earth’s orbit, it’s going to go around the Sun a little bit more slowly. When you stick it on an orbit that’s inside of the Earth’s orbit from the Sun, it’s going to go around the Sun more quickly than the Earth.
Fraser: If you have an object, which you’ve got the Sun and the Earth, the interaction of the Earth is going to mess with it, right?
Pamela: That’s where the magic happens. There are a few specific points – five of them to be exact – that if you stick an object exactly in one of these five points, the combined gravitational attraction of the Earth and the Sun gang up on this object to keep it moving in lockstep with the Earth as it goes around the Sun. If you’re dealing with the Moon-Earth system, you can stick things in the five specific spots that come from the combination of the Earth and the Moon so that it sticks there, following the Moon in its orbit around the Earth in lockstep.
Fraser: Hold on, so you’re already said places where its stable. What if you’re not in one of those places?
Pamela: if you’re not in one of those places, you’re happily going to end up in some sort of orbit going around the object, but you’re not going to be synced up with anything. For instance, the space shuttle at the space station right now is zipping around the planet every 90-100 minutes. The moon, on the other hand, takes 20-some-odd days to go around the planet.
If I move the space shuttle and the space station its attached to, out into gradually further and further orbits, and position it in just the right orbit in just the right period of time, even though it’s not as far away from the Earth as the moon, it would still go around the Earth with the same orbital period as the moon. It’s in one of these magical Lagrangian spots where the potential and kinetic energies of the systems balance out just right to keep it there.
Fraser: Right. If you slowly move it out and don’t necessarily have it in a perfect circular orbit, it might get caught into some weird, gravitational dance, and get thrown out of the system or hurled into the Earth or sent into orbit around the Sun, or…
Pamela: Most likely it will just end up in a very elliptical orbit around the Earth.
Fraser: Right, get turned into very elliptical orbits. So if you have a little space rock that comes into our system, in most situations it’s going to crash into the Earth, crash into the Moon, get skewed away into an elliptical orbit or…
Pamela: It’s just going to be another satellite.
Fraser: Yeah. It’s not going to stop and pause and stick around. Let’s talk, then, about these Lagrange points. How do they work?
Pamela: There are five of them that are ever so creatively named: L1, L2, L3, L4 and, well, L5.
Fraser: And that’s Lagrange-1, etc. Right?
Pamela: Right. So Lagrange-1 is the point between the two masses that stays in sync with the smaller object. For instance with the Earth-Sun system, this is the point in space nearer the Earth that, if an object is plunked down in L1, it goes around the Sun in the same just about 365 day period that the Earth has. We will always have this constant line going Sun-object-Earth lined up like little soldiers.
Fraser: So if we take that object and put it closer to the Sun, it’s going to be travelling at a faster orbit like Venus, so it will go around the Sun faster than the Earth will.
Fraser: Yeah. If we move a little more toward the Earth from that point, it will still be going faster than the Earth will, but it will actually be going slower than that point. Right? If that makes any sense. You’re saying it goes in lockstep with the planet, so…
Pamela: Here’s a different way of looking at it that’s a little bit weird. If I take an object and put it the exact same distance from the Sun as L1, but I plunk it down so the Earth, Sun and this object form a right angle from above, that object is going to start going around the Sun with its own period that is way shorter than one Earth year.
Pamela: It’s just going to be heading around following Kepler’s laws.
Pamela: Now if I take that object and take it at that specific distance from the Sun at just the right moment so that you have Earth, Sun and this object in a straight line with the object between the Earth and the Sun, and then I give it just the right amount of momentum, it’s going to travel around the Sun with the exact same orbital period as the Earth.
Fraser: Right. I’m going to make a guess here, but the point is the Earth is tugging on it and providing just that extra little bit of oomph to keep it going around at that speed.
Pamela: The Earth is giving it that extra pull. Well, not so much an oomph as it’s combating the Sun’s pull. It’s because of the Sun’s mass that the object would normally be zipping around so quickly. If you have the Earth pulling in the exact opposite direction, in a way philosophically, it’s like you removed a chunk of the Sun. if you make the Sun smaller you can orbit it more slowly.
By having the Earth there, pulling away with its own gravitational pull, it slows down the velocity that’s needed to stay in a nice stable orbit around the Sun.
Fraser: I’ve got an analogy. If you’re diving and you’re going to wear a weight belt to keep yourself perfectly stable, then if you want to go back up you could attach a balloon behind you that would start pulling you back up. You could balance it out with weights and balloons, with the Sun being the weights and the balloons being the Earth. The right spot is your Lagrange point. 1
Pamela: Just like with the weights and the balloons, you have to get it exactly right or you’re either constantly floating or constantly sinking. With the Lagrange points, especially with the first three, you have to get it exactly right, or you’re going to go flying out of it. These aren’t stable locations to be. The spaceships we stick there have to have their own engines and they’re constantly making their own corrections to stay in these places.
Fraser: Okay, so these spots, although you can keep going at that same orbital speed, they’re not stable. It’s almost like you’re at the top of the point of a needle, and you can fall any direction and have to fall out of that Lagrange point. The only way to stay there is to keep using your rockets.
Pamela: Mathematically they’re what we call saddle-points. In certain directions, you’re going to fall right back down to the Lagrange space. If you’re taking a marble and trying to balance a marble on a western saddle, if you move it toward the head or butt of the horse, the marble will roll right back to the centre of the horse’s back. If you bump the marble left or right, it’s fallen off the horse. I know people (including myself) who have had the same experience of falling off the horse.
These are semi-stable positions. The spaceships we stick there have engines that make corrections to stay put. At the same time, it’s so convenient to have something that isn’t in the Earth’s orbit, and is following us around the Sun. it makes communications easier. It’s worth the expenditure of energy.
Fraser: Right, if you wanted to put a spacecraft there and didn’t have the help of the Earth’s gravity, you’d have to fire your rockets non-stop, using tremendous amounts of fuel. Even though you’ve got to do minor corrections to stay at that sweet spot, it beats having to fire your rockets non-stop o stay in that kind of position.
Pamela: So with the L1 spot, which is between the Sun and the Earth, that’s someplace we stick things that are observing the Sun for us. What’s cool is they’re just enough closer to the Sun that in a lot of cases, when there’s a particle spray – a bunch of electrons headed our way from the Sun – they might hit SOHO that’s hanging out at L1 a little bit before they hit Earth, about an hour earlier. That gives us extra time to protect our astronauts and put satellites into safety mode, because SOHO can send us radio signals at the speed of light that these electrons are coming toward us at less than the speed of light.
Fraser: Right. Okay, so that’s L1. What’s L2?
Pamela: If you have a position between the Earth and the Sun, there’s also a point that’s on the same line but it’s beyond the Earth. So you go Sun-Earth-object, and that we call L2 (ever so creatively).
Normally if you stick an object on an orbital path bigger than the Earth’s orbit, it will orbit a little bit slower. Since you have the added pull of the Earth, it’s like making the Sun a little bit bigger, so an object can orbit faster and still be stable at that greater distance. It’s not entirely stable: just like L1, it’s saddle shaped and you can fall off the Lagrange point. It’s still a great place to stick things that have to make corrections because it makes the communications easy.
For instance, the Herschel satellite, the Planck satellite, the James Webb Space Telescope are all candidates for the Lagrange-2 point. WMAP, the microwave anisotropy probe that has given us such wonderful information about the cosmic microwave background is hanging out at the Lagrange-2 point.
This is a good place to put things that is protected a little bit from the Sun’s light, by the Earth hanging out there. It’s in a nice safe place beyond the Earth, following us around an orbit, and because it’s not orbiting us, instead orbiting the Sun, all the random junk that orbits the Earth is not in any danger of hitting these things in the Lagrange points. The radiation doesn’t get there. It’s a nice safe place to stick things that work in the infrared and radio that need it a little bit quieter and a little bit darker.
Fraser: So you wouldn’t necessarily want to have one of those satellites orbiting the Earth, because of our radio static.
Pamela: Our heat.
Fraser: Our heat. Right. That would actually cause them some problems. So if you keep them away from the Earth, they’ll be cold, and will have fewer radio waves blasting them. They’ll have a chance to observe better the state of what the universe really is. At the same time, you want to put them some place where you’re not going to have them firing their engines non-stop. You also don’t want them somewhere you can’t communicate with them.
Yeah, I can imagine if you pushed one of those telescopes out to a larger orbit than the Earth, it’ll slip behind us in orbit and there will be times like when we’re trying to communicate with the rovers on Mars, right? They’re on the other side of the Sun and there’s no way to communicate with the rovers. If we put them in the L2 point, then it’s there in the exact same spot in the sky – which probably makes communication a lot simpler, less power on the spacecraft than the kind of thing the rovers need to communicate with (though they relay stuff through satellites).
So I can see it makes a lot of sense. Okay. What’s the next point?
Pamela: Then there’s L3, and we don’t have anything hanging out there. L3 is the one that’s opposite us, so that it goes Earth-Sun-object. If you can imagine an object that has an orbit on the exact opposite side of the Sun from us where it’s getting pulled on by both the Sun’s gravity and the Earth’s gravity. Even though it’s not the same distance as the Earth from the Sun, it’s orbiting with the same period, constantly staying in lockstep with us, always out of sight.
Fraser: So if I imagine this right, you’ve got the Sun and the Earth and I guess the combined gravitational force is pulling on this object. That feels to me like it would fall into the Sun.
Pamela: Here we’re talking about an object that has an orbit that’s again, a snert bigger than the Earth’s orbit. It’s trying to head off in a line to get away from the Sun, but it’s the combined gravity of the Earth and Sun that’s keeping it on its circular orbit, chewing around in lockstep with the Earth. This is very similar to L2, but it’s beyond the Sun from us.
Fraser: So if you were to look at the line from above it would be like this object will be almost the same distance from the Sun as the Earth…
Fraser: Hard to calculate or see, but a little bit more. Instead of just going into a larger orbit, the way it should if it’s further away from the Sun, the Earth is almost increasing the mass of the Sun and keeping it at that exact same orbit.
Okay. Is it stable?
Pamela: Again, it’s a saddle point. The objects are going to want to fall out of that spot. If it can balance just right, or has engines to keep it balanced, it will stay there.
Fraser: There are no spacecraft planned for that, are there?
Pamela: No, because the communications isn’t possible.
Fraser: But I can imagine it would be great. If you ever had SOHO, you could put another SOHO on the other side of the Sun and observe it at all times.
Pamela: The trick is you start needing to have things at the right angles between the Earth, Sun and the object so that you can relay the communications around the Sun, just like we have satellites that allow us to relay communications around the planet Earth. We can’t talk directly to a satellite that’s through the planet, on the opposite side of the Earth in its orbit. Instead, satellites can relay communications from one satellite to the next to get from Australia to Washington DC.
Fraser: Right, so if we had other satellites going around Venus or in some of the other Lagrange points, you could actually get this communication. So you could always observe the front and backside of the Sun at the same time.
Pamela: Then just relay the information all the way around and put it together in the lab later.
Fraser: There might be uses for those. Would they be useful going around the Moon, in the Earth-Moon system?
Pamela: This is where you start to get into space elevators and other crazy stuff. Let’s talk about L4 and L5 to get them out of the way first.
Fraser: Sure, yeah.
Pamela: There are two more Lagrange points left, just two. These are the most stable. They are points that lag behind the Earth in its orbit and ahead of the Earth, such that if you drew an angle from the Earth to the Sun to either L4 or L5, both of those angles are 60-degree angles.
There are these hills that it’s capable to stand on top of and just hang out there and be gravitationally balanced.
Fraser: So it’s the combination of the gravity from the planet pulling you forward, and you’re still going around the star, keeping you in that orbit. If you fall too far back, the gravity of the planet pulls you back in. this is the opposite of that saddle. It’s very stable – it requires energy to get out of this orbit.
Pamela: The objects are hanging out here. They’re getting tugged forward by the Earth, or pulled back from the Earth, because their natural inclination is going to have different periods than what they are. It’s really neat that if you have a map of your potential of hanging out in any particular point, these are actually at the tops of hills. They’re fairly flat tops of hills. Once you’re up on top, you have to take effort to fall off. What’s cool is you can actually end up with things inside these larger L4 and L5 points on little tiny circular orbits, where they’re going around within the L4 or L5 point and also going around the Sun. that’s just kind of neat.
Fraser: So it’s like a volcano. You’ve got a mountain where it’s quite hard to get into that point, but once you’re at the top, there’s actually a crater inside that’s easy to roll down into.
Pamela: Sort of like that, yeah.
Fraser: Not that there’s actually volcanoes in space, but that’s the way the gravity works.
So if we were to put a spacecraft into one of these L4 or L5 points, same deal – they’d just sit there, no energy required, right?
Pamela: What’s cool is there are asteroids hanging out in the L4 and L5 points of Jupiter. We call these the Trojan asteroids. It looks like Neptune also has its own Neptunian version of Trojan asteroids that may even be more populated than Jupiter’s. Mars is tugging on asteroids as well, holding them locked in its Trojan points. These are places where the solar system likes to store its rocks.
Fraser: We don’t have any going around the Earth?
Pamela: Not as much as these bigger things like Jupiter and Neptune.
Fraser: I wonder, if you could fly some asteroid observing telescope out to the Earth L4 Lagrange point and place it there, would it see rocks and debris and stuff in a cloud?
Pamela: I’m sure the density of rocks and pebbles and pea-sized bits of gravel in the Earth’s Lagrange points is probably higher than they are elsewhere in the solar system. These are just good places to store things.
Fraser: If you were sitting on Jupiter’s orbit, maybe standing still on Jupiter’s orbit while it and its Trojans go around, you’d be standing there and a whole pile of asteroids would go past you, then Jupiter, then a whole pile more asteroids.
Pamela: Oh yeah. That’s the really cool thing. If you look at a plot of where rocks are in the solar system, if you look at a plot of where all the asteroids are located, there are just piles of them in Lagrange points for Jupiter, Saturn and Neptune. That’s just neat to look at.
Fraser: We talked a bit about spacecraft we might put in some of those Lagrange points. I’ve heard ideas of putting spacecraft into the L4 and L5 points as well – space colonies, space stations. It’s so stable it doesn’t require energy once you put it in there.
Pamela: That’s one of the places they have at various points talked about, with the Earth-Moon system, sticking space stations.
What’s also cool is with the not particularly stable, but we have engines to fix it L1 and L2 points in the Earth-Moon system, you can start to think about building space elevators with regard to the Moon.
The moon is facing the Earth the exact same way all the time. It’s going around the Earth at the same rate that it’s rotating about its axis. So if you have something in the Earth-Moon system’s L1 or L2 point, it’s essentially in geostationary orbit around the Moon. It maintains the same orientation with the same plot of land on the surface of the Moon all the time.
It’s not the same way with the Earth. The Earth rotates about its axis fairly quickly. There are specific geostationary orbits that we stick communications satellites in. With the Moon, you can use the L1 and L2 points. So you can conceive of potentially some day sticking some sort of space station in geosynchronous orbit above some point on the equator where there’s land and building a carbon nanotube space elevator tether and dropping it down to the surface of the Earth.
You could have an elevator to get to geosynchronous orbit (which is pretty high up). Then you fly your little rocket from that craft to something that is in the L1 orbit between the Earth and the Moon and you take a different elevator down to the surface of the Moon. Hang around, walk to the exact opposite side (you’d probably actually want a vehicle of some sort) and then take an elevator up to the L2 point which is pointed away from the Earth-Moon system and could be pointed away from or toward the Sun, or at right angles. You could use that as a jumping off point to escape the Earth-Moon gravitational system.
Fraser: that would be awesome. Like heaven! How cool would that be?
Pamela: It’s a brave new sci-fi universe.
Fraser: Let’s get on that, people!
Pamela: It’s a bit expensive.
Fraser: I want my space travel!
I actually did an article on that space elevator concept. The advantage is since you attach the elevator to the surface of the Moon, you don’t have the problem with the instability of the L1 point, because it’s tied to the ground. Just like a balloon really wants to float away, you’d be able to tie your ribbon down to the Moon and even though it’d be trying to get out of that orbit, it would be continuously held there.
Pamela: The only thing that’s a bit scary, and anyone who’s read Kim Stanley Robinson’s Red Mars series has read about this, is what if the cable breaks?
Fraser: It would come toward the Earth.
Pamela: Yeah, and you can end up with a ribbon of destruction wrapping itself around the planet. That’s a rather bad thing. So yeah, there are all sorts of safety things to be figured out. It’s still a cool plot point and a cool thing to dream about and imagine. The future has so many possibilities. It’s fascinating to think about what’s possible thanks to these neat gravitational holes in space.
Fraser: So now hopefully, if you hear someone bring up Lagrange points, or if you read it in an article, you’ll know what they’re talking about. Thanks Pamela!
This transcript is not an exact match to the audio file. It has been edited for clarity. | 0.85898 | 3.308522 |
Observatory reveals storms on Neptune, oceans on Titan
Image of Neptune taken with the Keck II Telescope in infra-red light. A prominent storm system can be seen on the lower right of Neptune's disk.
January 18, 2000
Web posted at: 5:56 p.m. EST (2256 GMT)
LIVERMORE, California -- The best ever Earth-based images of
two distant celestial bodies reveal giant storms on Neptune
and possible landmasses separated by chilled hydrocarbon
oceans on Titan, scientists with the Lawrence Livermore National Laboratory said this week.
The infrared light images were captured with the W.M. Keck II telescope in Hawaii using adaptive optics
technology and were presented last week at a meeting of the American Astronomical Association.
Their unprecedented clarity exceeds even the capability of the Hubble Space Telescope, according to scientists with the
Neptunian winds reach 600 mph
The images of Neptune, a large gaseous planet 2.8 billion
miles from Earth, exhibit giant tempests driven by prevailing
winds of 600 miles per hour.
| IMAGE GALLERY|
Keck's infrared detectors penetrated into the deep layers of
the planet's roiling atmosphere, where heat from its
contracting core generates the storms.
As Neptune whirls through its 16-hour day, storm features are
pulled completely across the face of the planet. At the north
pole, a mysterious haze crowns the planet.
Keck's adaptive optics images of Neptune are helping
scientists study the planet's storms and their evolution, a
first step toward understanding Neptune's weather and
"Neptune is one of the most dynamic of the giant planets,"
said Dr. Bruce Macintosh of the Livermore Lab. "It's always
changing. Being able to study it from the ground on a
continuous basis, rather than waiting for a spacecraft to fly
by, is a huge advantage."
Titan could sport highlands, great basin
The Titan images will offer clues about the complex surface
composition of the Saturnian moon, a frigid world some 800
million miles from the sun.
Titan has a nitrogen-rich atmosphere similar to that of the
early Earth. Sunlight shining on this atmosphere produces a
deep orange haze that obscures Titan's surface from view at
Keck's new adaptive optics images, taken in infrared light,
offer much greater sensitivity than past observing
techniques. They pick out features "that may be cold
hydrocarbon seas and lakes," said Dr. Seran Gibbard, a
Livermore scientist. Other features might be highlands, and
one dark area appears to be a large impact crater or great
New technologies unravel distant mysteries
In 2004 the Cassini spacecraft, built by NASA and the
European Space Agency, is scheduled to land the Huygens probe
on Titan. Keck's new images will help researchers determine
beforehand whether the probe will plunge into an
extra-terrestrial sea or land on a solid surface.
The images are among the first taken
with Keck's new adaptive optics technology, which uses rapid
mirror adjustments to remove Earth's atmospheric turbulence
from the telescope's images.
In coming months, a new spectrograph will be added to the
Keck adaptive optics system. This will help answer questions
about the chemical composition and physical state of the
features newly seen on Neptune and Titan.
The team of researchers investigating the images includes scientists from the Keck Observatory and the University of California at
Berkeley and Los Angeles. The team was led by Dr. Claire Max of the Livermore Lab.
Huge NASA telescope may be headed for fiery descent to splash landing
January 14, 2000
First spacewalk to repair Hubble Telescope begins Wednesday
December 21, 2000
Palomar observation reveals clouds on Neptune
October 18, 1999
NASA announces missions to seek planets, study gamma rays
October 15, 1999
Commercial satellite's launch from sea is a first
October 10, 1999
Lawrence Livermore Laboratory
W.M. Keck Observatory
Note: Pages will open in a new browser window
External sites are not endorsed by CNN Interactive. | 0.812649 | 3.6253 |
‘Supermoon’ to make mischief with sun and sea
Norse legend has it that two giant wolves roam the sky — with Skoll chasing the moon and its brother Hati going after the sun.
If either manages to sink its teeth into its prey and hold it back, an eclipse occurs, the story goes.
Tales of cosmic wolves may once have been a useful way of explaining the weird and scary interval when the sun, the source of life on Earth, is briefly extinguished.
For astronomers, though, total eclipses occur when the moon sneaks between Earth and the sun, and the three bodies align precisely.
By quirky celestial symmetry, the moon as seen from Earth is just broad enough to cover the solar face, creating a breath-taking silver halo in an indigo sky pocked by daytime stars.
The moon will do this trick again on Friday for the only total solar eclipse of 2015, with a dramatic backdrop provided by Nordic islands on the roof of the world.
Then on Saturday the lunar magician will bemuse us again, this time with exceptional tides.
The reason: Earth’s satellite will be a “supermoon,” which happens at its closest point to our planet, called a perigee.
This, and the moon’s alignment with the sun, will add to the gravitational pull on the seas — creating what is literally a high point in the 18-year lunar cycle.
“The eclipse and the tide are linked,” says Kevin Horsburgh, head of the Marine Physics and Ocean Climate research group at Britain’s National Oceanography Centre (NOC).
“For an eclipse to take place, the sun, the Earth and the moon need to be in a straight line, which is also an essential condition for high tides.
“And for particularly big tides, the moon needs to be directly overhead at the equator at the time.”
On Friday, the moon’s shadow will alight on Earth’s surface at 0741 GMT in the eastern central Atlantic, according to Britain’s Nautical Almanac Office. (//astro.ukho.gov.uk/eclipse/0112015/)
By 0913 GMT, seen from a point about 700 kilometres (440 miles) south of Greenland, the sun’s face will be completely obscured.
This “path of totality” will follow a 5,800-kilometre curve across the farther north Atlantic, into the Arctic Ocean.
It will cross land in the Faroe Islands, a Danish archipelago halfway between Iceland and Norway, and the Norwegian island group of Svalbard.
“The path (of totality) ends at the North Pole at 1018 GMT,” veteran astronomer Fred Espenak says on the specialist website EclipseWise.
Partial eclipses — which resemble a bite taken out of the sun — will be visible from Iceland, Greenland, Europe, North Africa, western and eastern Asia, ending at 1150 GMT.
London will have its deepest eclipse since 1999, with 85 percent of the sunlight blotted out.
The celestial ballet will on Saturday result in major tides most perceptible in Canada’s Bay of Fundy, on the French Atlantic coast, in the Channel and North Sea — but even the Mediterranean will feel the difference.
France’s Navy Oceanic and Hydrological Service (SHOM) has warned thrill-seekers to beware when the tide sweeps around Mont Saint-Michel, the ancient abbey-island located on the coast of Normandy.
Saturday’s tide on the long, sloping estuary of the River Couesnon at the popular tourist spot will be a whopping 14.15 metres (46 feet) — the height of a four-storey building. The average tide there is 10.5 metres.
– ‘Faster than a running man’ –
“It’s going to be spectacular,” says SHOM tide specialist, Nicolas Weber.
Locals say the incoming tide at Mont Saint-Michel outstrips a galloping horse.
While this is incorrect, said Weber, “it will come in faster than a running man. It will be dangerous to venture out too far.”
Horsburgh, from Britain’s National Oceanography Centre, said Saturday’s tide would be several centimetres (inches) above last year’s maximum overall, and in some places may even be slightly surpassed this September, which will also be an equinox, when high water occurs.
Weather is a big influence on a tide’s fierceness — gales can whip up surges able to test the mighty barriers that protect the Netherlands and London from flooding.
“A storm surge can elevate water levels by around four metres in the North Sea on the Dutch coast and tend on the east coast of Britain and the Thames estuary to be around two, two-and-a-half metres in the event of a bad storm,” Horsburgh told AFP by telephone.
In 2010, a sea surge, driven by a storm called Xynthia, flooded parts of the Vendee coast on France’s Atlantic seaboard, killing 41 people. | 0.82724 | 3.441832 |
Next stop the ocean worlds of Enceladus and Europa
Space news (planetary science: water worlds of the solar system; Enceladus and Europa) –planets and moons around the solar system and exoplanets across the universe covered with water–
The solar system’s awash in water! NASA missions have provided verifiable facts showing ocean worlds and moons exist in our solar system and beyond,other than Earth. Planetary bodieswhere water is locked in a frozen embrace and even flowing beneath miles of ice. Liquid water exobiologists are keen to explore for life forms they would love to meet and get to know a little better during the next phase of the human journey to the beginning of space and time. Watch this YouTube video on NASA’s search for life on the ocean worlds of the solar system.
Papers published bythe journal Science and written by Cassini mission scientists and researchers working with the Hubble Space Telescope indicate hydrogen gas believed pouring from the subsurface ocean of Enceladus could potentially provide chemical energy life could use to survive and evolve. Watch this YouTube videocalled “NASA: Ingredients for Life at Saturn’s moon Enceladus“, itshowsthe proof scientists used to come to these conclusions. Their work provides new insights concerning possible oceans of water on moons of Jupiter and Saturn and other ocean moons in the solar system and beyond.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. ”These results demonstrate the interconnected nature of NASA’s science missions that are getting us closer to answering whether we are indeed alone or not.”
Researchers believe they have found evidence indicating hydrogen gas could be pouring out of hydrothermal vents on the floor of Saturn’s moon Enceladus and into these oceans of water. Any microbes existing in these distant waters could use this gas as a form of chemical energy to operate biological processes. By combining hydrogen with carbon dioxide dissolved in this ocean of water in a chemical reaction called methanogenesis, geochemists think methane could be produced which could act as the basis of a tree of life similar to the one observed on Earth.
On Earth, this process is thought to be at the root of the tree of life, and could even be essential, critical to the origin of life on our little blue dot. Life existing on our planet requires three main ingredients, liquid water, a source of energy for metabolic processes, and specific chemical ingredients to develop and continue to thrive. This study shows Enceladus could have the right ingredients for life to exist, but planetary scientists and exobiologists are looking for evidence of the presence of sulfur and phosphorus.
Previous data shows the rocky core of this moon is similar to meteorites containing these two elements, so they’re thought to be chemically similar in nature, and scientists are looking for the same chemical ingredients of life found on Earth, primarilycarbon, nitrogen, oxygen, and of course hydrogen, phosphorus, and sulphur.
“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
Cassini detected hydrogen in plumes of gas and frozen matter spewing from Enceladus during the spacecraft’s deepest pass over its surface on October 28, 2015. This combined with previous data obtained by Cassini’s Ion and Neutral Mass Spectrometer (INMS) during earlier flybys around 2005,helped scientists determine that nearly 98 percent of the material spraying from the surface of the moon is water. The remaining two percent is thought to be around 1 percent hydrogen with some carbon dioxide, methane,ammonia and assorted unknown molecules in the mix.
Cassini has shown us two independent detections of possible water spewing from the surface of Enceladus. NASA and its partners are currently looking over proposals to send spacecraft to determineif there is an ocean of water beneath its surface by taking a sample. The Europa Life Finder (ELF)is the proposal NASA’s seriously looking at undertaking at this point, but reports indicate a few other proposals are also being discussed.We’ll provide additional information on other proposals as they’re released to media outlets.
“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” said Hunter Waite, lead author of the Cassini study.
Two different observations of possible plumes of water spraying from the icy surface of Saturn’s moon Enceladus provides proof hydrothermal activity is occurring beneath. Geophysicists believe hot water is combining chemically with rock and other matter at the bottom of an ocean of water underneath its icy surface to produce hydrogen gas. Hydrogen gas exobiologists think could be used as energy, food of a sort, to sustain life forms exobiologists want to meet and learn more about. A meeting that would change our place in the cosmos, the way we think about the universe, and reality.
Astronomers and researchers working with the Hubble Space Telescope in 2016 reported on an observation of a possible plume erupting from the icy surface of Europa in the same general location Hubble observed a possible plume in 2014. This location also corresponds to the unusually warm region with cracks in the icy surface observed by NASA’s Galileo spacecraft back in the 1990s.This provides evidence this phenomenon could be periodic, intermittent in this region of the moon. Mission planners are looking at this region as a possible location to obtain a sample ofwater erupting from a possible ocean of water beneath its icy surface. Watch this video on Europa.
Estimates of the sizeof this most recently observed plume indicate it rose about 62 miles (~100 kilometers) from the surface of Europa, while the plume in 2014 only reached a height of around 30 miles (50 kilometers).
“The plumes on Enceladus are associated with hotter regions, so after Hubble imaged this new plume-like feature on Europa, we looked at that location on the Galileo thermal map. We discovered that Europa’s plume candidate is sitting right on the thermal anomaly,” said William Sparks of the Space Telescope Science Institute in Baltimore, Maryland. Sparks led the Hubble plume studies in both 2014 and 2016.
One interesting thought’s the plumes and the hot spot is somehow linked. If this is the case, it could mean the vented water’s falling onto the surface of the moon, which would change the structure and chemistry of the surface grains and allow them to retain heat longer than the surrounding region. This location would be a great place to search for the ingredients of life and a possible entry point into an ocean of water beneath.
These observations by the Hubble Space Telescope and future looks enable future space missions to Europa and other ocean worlds in the solar system. Specifically, laying the groundwork for NASA’s Europa Clipper mission, which is setfor a launch sometime in the 2020s.
“If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them,” said Jim Green, Director of Planetary Science, at NASA Headquarters.
NASA has indicated they’re looking to identify a possible site with persistent, intermittent plume activity as a target location for a mission to Europa to explore using its powerful suite of science instruments. Another team’s currently at work on a powerful ultraviolet camera to add to the Europa Clipper that would offer data similar to that provided by the Hubble Space Telescope, while some members of the Cassini team areworking on a very sensitive, next generation INMS instrument to put on the spacecraft.
Water’s the story of life on Earth! Science has shown it played and plays the main part in the birth,evolution, and sustenance of life on Earth.
NASA’s planning on taking the human journey to the beginning of space and time to the ocean worlds of the solar system during the decades ahead. To search for the ingredients of life and even possibly simple one-celled life forms, of an unknown type. We plan on going along for the ride to have a look for ourselves and we hope to see your name on the ship manifest. We’ll save a seat for you.
Join the human journey to the beginning of space and time by taking part in NASA’s Backyard Worlds: Planet 9. Participants take part in the search for hidden worlds between Neptune and Proxima Centauri.
NASA and FEMA scientists tracking asteroid using ground and space-based telescopes to refine estimates
Space news Sept. 20, 2020 ( NASA Planetary Defense Office: joint NASA and FEMA operation; emergency response to future asteroid impact) – Jet Propulsion Laboratory in El Segundo, California; conducting emergencyresponse exercise forpossible future asteroid impact –
NASA Planetary Defense Officer Lindley Johnson spoke today at a simulated emergency response exercise to a possible future asteroid impact estimated for some time around Sept. 20, 2020. The exercise provided a forum for the planetary science community to prepare emergency managers by collecting, analyzing, and sharing data about such an event should it occur. It also provided the chance for emergency response personnel, the asteroid science community, and emergency managers across the country and the world to begin forming the strong working relationshipsrequired to protect humanity from an asteroid strike.
This particular exercise wasthe third in a series hosted jointly by NASA and the Federal Emergency Management Agency (FEMA). It was conducted to prepare emergency services in the event of an asteroid impact becomes more likely during the years ahead and strengthen bonds between their partnership.At this point, NASA and FEMA officials say an asteroid impact is very unlikely, but we need to be ready in case of an emergency.
“It’s not a matter of if — but when — we will deal with such a situation,” said Thomas Zurbuchen, Associate Administrator for NASA’s Science Mission Directorate in Washington. “But unlike any other time in our history, we now have the ability to respond to an impact threat through continued observations, predictions, response planning, and mitigation.”
During the emergency response exercise, planetary science community representatives showed how data concerning a possible future asteroid impact would be collected, analyzed, and shared. Emergency response managers talked about the way the information would be used to consider the challenges and options during an asteroid impact. They also talked about the way to prepare, respond, and tell the public about the crisis.
“It is critical to exercise these kinds of low-probability but high-consequence disaster scenarios,” FEMA Administrator Craig Fugate said. “By working through our emergency response plans now, we will be better prepared if and when we need to respond to such an event.”
This possible asteroid impact in four years time was first discovered in the fall and was at that time estimated at 2 percent. NASA assets will continue to track the asteroid for the next three months, before updating the chances of a possible impact. But at this point, NASA and its partners are preparingto launch a possible mission to deflect or otherwise intercept the asteroid. Exercise attendees were left with the challenge of preparing for a mass evacuation of a major US metropolitan city and region in the worst case scenario. They went over possible impact scenarios, looked at possible population displacement estimates, discussed infrastructure that would be affected, and all data that could realistically be known concerning a possible asteroid impact in four years time.
“The high degree of initial uncertainty coupled with the relatively long impact warning time made this scenario unique and especially challenging for emergency managers,” said FEMA National Response Coordination Branch Chief Leviticus A. Lewis. “It’s quite different from preparing for an event with a much shorter timeline, such as a hurricane.”
They also looked at ways to pass on accurate, timely, and useful information to the general public, while still addressing the possible issue of false rumors and information emerging during the years leading up to an impact.
“These exercises are invaluable for those of us in the asteroid science community responsible for engaging with FEMA on this natural hazard,” said NASA Planetary Defense Officer Lindley Johnson. “We receive valuable feedback from emergency managers at these exercises about what information is critical for their decision making, and we take that into account when we exercise how we would provide information to FEMA about a predicted impact.”
Study and planning for a possible asteroid impact continues
NASA’s continuing to provide expert input to FEMA about the asteroid through the Planetary Coordination Office. The partners will continue to assess the asteroid and conduct asteroid impact exercises in preparation for a worst case scenario. They also intend to start reaching out to other representatives from local and state emergency management agencies and the private sector in future emergency exercises.
NASA’s looking for a few good firms and private individuals to form meaningful, useful business partnerships with, check it out here. | 0.911919 | 3.255762 |
You may or may not know someone named Luca, but you owe your life to a Luca all the same. What's more, so do we all.
That vital Luca is better known as LUCA—for "last universal common ancestor," the very first, single-celled organism off the biological assembly line some four billion years ago that gave rise to everything that ever followed: bugs, birds, trees, kangaroos, and eventually big-brained mammals who wonder where they came from and invent acronyms to sort it all out.
LUCA has always been a broadly accepted theory, even if nobody could ever define just what our greatest of great grandaddies was like. Now, in a paper published in Nature Microbiology, a research team headed by biologist William F. Martin of Heinrich Heine University in Düsseldorf Germany, announced that it may have reconstructed a rough genetic blueprint of that long-vanished organism.
Martin and his colleagues started their work by studying the six million or so genes common to both bacteria and other single-celled organisms known as archaea—which are similar to bacteria but differ in shape, membrane chemistry, metabolism and more. Grouping those genes into categories defined by age, function and other characteristics, they came up with just 335 sequences that are thought to have the deepest routes in the bacteria and archaea lines—and, by extension, in all of the multi-celled organisms that followed. It was those 335, then, that formed the basis of LUCA.
It's a perfectly reasonable conclusion so far, though that hasn't stopped an academic cat-fight—a healthy if sometimes snarky part of scientific progress—from breaking out, with most of the debate centering on whether the organism had enough genetic robustness to qualify as a living thing yet or was only sort of quasi-alive. And no one knows either if this really is the LUCA, or just a LUCA, an early life form that was followed by something a tiny bit later.
But a larger and more important point has been lost in that kerfuffle, one that has implications not just for life on Earth but elsewhere in the universe. The 335 gene groups in the new paper show that the organism likely thrived in a gassy, metal-rich environment and may have had a high tolerance for heat—pointing to a survival niche in the vicinity of boiling sea vents on the ocean floor, which are known to be home to some modern species too. The temperatures there reach scalding highs of roughly 660° F (350° C), and while that's too hot for any known type of life form to survive, any organism that did settle down in a place like that would not have to feel the full force of the heat.
"The organisms that live there are playing a careful dance," said exobiologist Tori Hoehler of the NASA Ames Research Center in Moffett Field, Calif., in an earlier conversation with TIME about extreme life forms. "In those systems the temperature gradient between the water that’s coming out of the vent and the surrounding ocean water drops off so rapidly that things can associate themselves closely anyway."
That matters a lot for people looking for life in space. Solar systems throughout the universe may well be filled with water worlds that are frozen solid on the outside, but warm and churning inside. Even without sunlight to warm the worlds' interiors, the water remains liquid thanks to tidal flexing caused by the gravitational tugging of other planets or moons as they orbit nearby. Jupiter's moon Europa is all-but certain to be home to such an ocean. Its sister moons Ganymede and Callisto might be as well, as may be Pluto, according to evidence gathered by the recent flyby of the New Horizons probe.
If the newly identified LUCA made its home around hot vents on Earth, similar things could happen on Europa and elsewhere. And life being as adaptive as it is, the other organisms wouldn't even have to have the precise biochemical processes Earthly ones do in order to survive.
"Do they use light, do they breathe oxygen or hydrogen sulfide or things like that?" asks Hoehler. "They differ at the level of adaptations that allow them to survive that specific extreme."
Chemistry, in other words, is chemistry, and while the ingredients vary dramatically throughout the universe, they interact in the same way no matter where you go. What happened on Earth, it's increasingly likely, could easily happen anywhere. | 0.810907 | 3.543506 |
Using a distant spacecraft and a giant telescope, astronomers have unmasked the full ire of a storm so big that it encircles Saturn, a planet nearly ten times bigger than Earth.
(See Saturn pictures.)
Astronomers have been watching this northern-hemisphere storm since December 2010, when a bright plume of gas and ice bubbled up to the surface of the gaseous sphere that makes up Saturn.
The disturbance has since expanded by riding easterly winds blowing at up to about 220 miles an hour (100 meters a second). But until now very little has been known about the workings of the storm, its depth, and how it affects the ringed planet.
Now a new study, released Thursday by the journal Science, says the Saturn storm's effects reach about 370 miles (600 kilometers) into the stratosphere, according to observations made both by NASA's Cassini probe and the European Southern Observatory's Very Large Telescope array in Chile.
By comparison, thunderstorms on Earth usually top out at a height of 12.5 miles (20 kilometers)—and none of them circle our entire planet, despite its comparatively small size.
"It's hard to compare this storm to anything on Earth. It's simply gigantic," said study leader Leigh Fletcher, a planetary scientist at the University of Oxford in England. "The head met the tail in February of this year."
Saturn Storm Billions of Years in the Making
The Cassini probe, which has orbited Saturn and observed its motley system of moons for nearly seven years, sounded the first alarms of a brewing storm in December 2010. That's when unusual radio chatter—a sign of spiked lightning activity—emanated from the emerging plume of methane, ethane, and other material that make up the storm.
At the time, though, the probe wasn't able to analyze the storm's deeper layers—the necessary instrument, called the composite infrared spectrometer, must be programmed months in advance.
A second chance appeared in January 2011, however, so Fletcher brought in the cavalry. He convinced the Very Large Telescope's operators to monitor the storm's temperatures in high-resolution at the same time as Cassini observed the tempest in infrared, which allowed experts to infer wind speeds and the structure of the storm.
The combined observations suggest the storm was spawned by a layer of water clouds about 190 miles (300 kilometers) beneath the outer edge of the gas-giant planet. The cloud layer fueled an upwelling of gas and ice, followed by downwelling flanks that were about 20 degrees Celsius (36 degrees Fahrenheit) warmer than usual.
(Related: "Spring Rains Darken Saturn's Moon Titan.")
When Saturn formed about 4.6 billion years ago, it retained some heat from its formation. Fletcher said it's this warmth—not the sun's—that powers the planet's infrequent weather. In effect, the storm has been billions of years in the making.
Saturn's gaseous surface rotates every ten hours, but the planet takes about 30 years to orbit the sun. And because Saturn tilts toward the sun, like Earth, it has seasons—each lasting about 7.5 years.
The monster storm happened to usher in the second largest planet's latest spring—and an unprecedented opportunity.
"During the last spring on Saturn, we didn't have this kind of instrumentation available to us," Fletcher said. "It will be interesting to follow this storm and see if its dynamics apply to [other gas-giant] planets, like Jupiter, Uranus, and Neptune." | 0.851227 | 3.949569 |
Original URL: http://www.theregister.co.uk/2006/11/27/nasa_spitzer/
NASA spies bursting supermassive blackholes
Holy belching quasars, Batman
NASA astronomers think they have identified a pair of supermassive black holes, or quasars, that look like they are teetering on the brink of huge explosions.
Using the infrared camera on the Spitzer space telescope, the astronomers have been able to peer through obscuring dust and take a peek at the quasars at work.
Astronomers have suspected for some time that when galaxies collide, the supermassive black holes at their cores consume huge quantities of material; dust, gas and stars. The material is produced by violent periods of star formation, triggered by the galactic collisions.
It is normally very difficult to see the quasars at work on their intergalactic all-you-can-eat sessions because, as you might expect, two galaxies smashing into one another throws out a lot of dust and gas, blocking the view.
However, scientists now think that at some stage, the quasars get full. Once this happens, it will emit a huge burst of energy (NASA is describing this as a cosmic burp...) that could blow away a lot of the obscuring material.
Dr Maria del Carmen Polletta of the University of California at San Diego explains that black holes all emit radiation as they accrete matter. At some point, the amount of energy they emit is sufficient to destroy the surrounding dust.
Polletta used the Spitzer telescope to measure the amount of energy being absorbed by the dust surrounding suspected supermassive black holes. This gave her an indication of how luminous the quasars are, and from that, the research team can calculate how much material is being consumed.
She suggests that two quasars she has identified in a study (published in the May 2006 issue of Astrophysical Journal) are on the verge of just such an expulsion. One of the quasars is three billion times more luminous than our sun, suggesting it is gobbling up matter at a rate of around 68 solar masses per year; more than one of our suns per week.
"Black holes that are this heavily obscured and with this luminosity are very difficult to find and have not been extensively studied," says Polletta. "The belch of a black hole has never been verified with observations, so the explosion may not happen.
"The role that supermassive black holes play in the development of a galaxy is still unclear, there are still a lot of missing pieces. What we are seeing here is a very specific moment in the life of a black hole.
"According to astronomical models, black holes at this luminosity should destroy their surrounding material pretty soon." ® | 0.906906 | 3.521334 |
Cassini is no more. In the early hours of the morning, the long-lived spacecraft plunged into Saturn (intentionally) and broke apart, ending its 13-year run of exploring the sixth planet and it moons. Now the outer solar system is a lonelier place—and NASA is a decade out from having another visitor.
The Juno spacecraft at Jupiter set to crash into that world next year. Everything else out beyond the asteroid belt is hastily departing, too. In 2019, the New Horizons probe the captured Pluto will turn its attention to a small, primitive body called 2014 MU69 on its way out of the solar system. By 2025, our intrepid senior citizen space probes, Voyager 1 and 2, will be too weak to send back any data to Earth. The longest-traveled human-made objects will go quiet after nearly 50 years in space.
And then? Well, there's a gap. Despite everything Cassini discovered, the plucky explorer has no direct Saturn successor, and the outlook isn't great for the rest of the region.
The Europa Clipper—a mission to explore Jupiter's icy moon that might be the best place to look for life—may launch in 2022, but that date hinges on the success of the Space Launch System, NASA's enormous and yet-to-be-tested rocket that has had its share of problems. If everything works, the clipper could arrive within two years of launch. But if it has to use an ordinary United Launch Alliance Atlas V rocket instead, then that journey could take six years, meaning it wouldn't arrive until 2028.
Elsewhere, there's the possible 2021 launch of the Lucy spacecraft, which would travel among a group of asteroids that follow behind (but don't orbit) Jupiter. The European Space Agency has one planned outer solar system mission: the Jupiter Icy Moons Explorer, set to launch the same year as the Europa Clipper. It wouldn't arrive for eight years. As far as Saturn, Uranus, and Neptune are concerned, there are hopes and dreams but not official plans on the books just yet.
Such space missions take years and years of planning. So if you want to understand why there's no follow-up to an amazing mission like Cassini, you can look back to NASA's attitudes decades ago. In the 1990s, for example, NASA under then-administrator Daniel Goldin moved towards a "faster, cheaper, better" approach that largely focused in on Mars, de-emphasizing outer solar system exploration. That approach led to the excellent rovers that have explored the Red Planet, but on the flip side of that coin, Goldin nearly cancelled Cassini prior to launch despite more than a decade of development.
It was a major shift in focus for NASA's planetary science. Up until Cassini, there had been a continuous clip of outer solar system missions. The Pioneer 10 and 11 probes launched in 1972 and performed flybys of Jupiter and Saturn, and the Voyager program followed five years later. While the 1986 Challenger disaster set back many NASA missions, Cassini and Galileo (which visited Jupiter in 1994) were both well under way at the time. After the Voyager flybys of Uranus and Neptune, there were talks of sending Cassini-like probes to each. Such talk virtually disappeared in the 1990s. The New Horizons mission team fought hard to bring the Pluto mission to life after experiencing setback after setback.
This isn't to say NASA isn't planning some cool new missions. The tennis court-sized James Webb Space Telescope will blow away the already impressive Hubble Space Telescope. Asteroid exploration is about to experience a major boon: Lucy will be joined by the already-launched OSIRIS-REx mission, and NASA will send a probe to the protoplanet core Psyche. The Mars InSight lander will drill into Mars looking for present seismic activity, and the Mars 2020 rover will improve on the work of Curiosity and Opportunity. And NASA will send the Parker Solar Probe into the Sun, which is metal as hell.
But if looking back on Cassini's major discoveries at Saturn, Titan, and Enceladus have left you thirsty for more, we have some bad news: That thirst is going to go unquenched for a while. Talks of Uranus and Neptune missions are tentative at best. The best hope for Saturn now comes from NASA's New Frontiers program, which looks for excellent medium-cost missions has spawned spacecraft including Jupiter's Juno and Pluto's New Horizons. This round of New Frontiers missions must launch by 2024, and there are two Enceladus proposals, a Titan proposal, and a Saturn atmospheric probe under consideration. We may hear word about those proposals by the end of the year
"Hang tight, we're going through the evaluations now and we'll be announcing at the end of the year what some of the finalists will be," Jim Green, NASA Planetary Science Director, said at the Cassini press conference Friday morning.
Out in the far reaches of the solar system, there are hundreds of worlds beckoning visitations. The quartet of giant gas planets have 168 confirmed moons, and of those, we have yet to learn much about the 29 moons of Uranus or 12 moons of Neptune. Neptune's largest moon, Triton, is a backwards-orbiting captured Kuiper Belt object. It has geysers and an ocean, and is a patchwork world half cut with rock and ice. Uranus' moon Miranda has 6-mile cliff drop-offs—imagine a daring Death Star run through that treacherous terrain. Ariel may have had recent geologic activity, giving us a chance to see a world possibly just past its ocean moon phase. Umbriel is a dark world cut through with patches of bright ice and is battered by meteor bombardment. Titania, a fairly large moon, may have an ocean, as may its smaller sibling Oberon.
With Cassini gone, Juno on its own march toward destruction, and the outer solar system probes losing power by 2026, Cassini may be a sad ending to the 40+ year book on the outer solar system exploration. The rest is just slowly fading epilogue. | 0.882148 | 3.471573 |
OTTAWA — Voyager-1 celebrates its 35th anniversary in space by opening a new controversy about where our solar system really ends. Almost everyone thought the tiny NASA spacecraft had found the edge of the solar system after travelling 17.8 billion kilometres from Earth. Now new evidence suggests the edge might still lie ahead, and no one can tell how far.
Launched on Sept. 5, 1977, Voyager-1 is actually the second-oldest working spacecraft. Its identical twin Voyager-2 launched two weeks earlier, and is racing away from Earth in a different direction.
Both have photographed planets and moons on the way, and are now hunting for the ends of the solar system, a place never observed by humans, where the solar wind — charged particles flowing from the sun — stops flowing.
Instead the two Voyagers are expected to find the “interstellar medium,” space literally between the stars of our galaxy, the Milky Way.
Through the summer, analysts kept finding tantalizing hints that Voyager-1 had reached this interstellar space. Next stop: Another star, in a few million years.
Not so fast, says a study published in this week’s issue of the research journal Nature. Four scientists at Johns Hopkins University say the solar wind should be deflected in a new direction if the edge is near. And Voyager, measuring the solar wind, has found no change.
Still, experts feel the edge is close.
NASA has renamed Voyager’s task as “the interstellar mission,” and two months ago one of its scientists announced: “The laws of physics say that some day Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be. The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the solar system’s frontier.”
But when, exactly?
“It’s sort of like saying, ‘When do you get to the edge of town?’” said Queen’s University astronomer David Hanes. Someone can draw a neat line on a map, but the reality is that the town fades away gradually, he noted.
Space is the same. But he’s excited that soon Voyager will enter a new kind of space that’s far from empty.
“It’s even dirtier and smoggier than air in Toronto,” he said. There’s so much floating matter that if distant space were compressed to become as dense as air on Earth, “you wouldn’t be able to see your hand in front of your face.”
Hanes believes we owe a debt to Voyager for showing us our place, a very small one, in the expanse of space. Soon Voyager will enter the interstellar region and start fresh exploration — frozen, nearly out of energy and running on 1970s computer technology, but still able to amaze us. | 0.851253 | 3.533971 |
Pluto is a Dwarf Planet in the Kuiper Belt. It used to be classed a planet and used to be the farthest known planet from the Sun. It has five moons including called Charon moon.
Pluto was discovered in 1930 by Clyde W. Tombaugh. The planet is named Pluto after the God of the Underworld in Roman mythology. In Greek mythology the equivalent god is Hades.
Facts about Planet Pluto
* Diameter: 2324 km (1444 miles).
* Surface composition: Nitrogen, carbon monoxide, methane and water ices
* Average surface temperature: -233ºC (-382ºF)
* Mass: 0.002 (Earth = 1)
* Gravity: 0.07 (Earth = 1)
* Average distance from the Sun: 5.9 billion kilometres.
* Rotation Period: 6.39 Earth days (length of day)
* Orbital period around the sun: 248 Earth years (length of year)
* Rings = 0
* Moons = 5
* Average distance between Pluto and Charon: 19,600 Kms
The Orbit of Planet Pluto
Pluto’s orbit from the Sun varies from 4.4 to 7.7 billion kms and for the most of its orbit it is the outer most planet. Between 1979 and 1999 Pluto was actually closer to the Sun than Neptune and the closest approach to the sun (perihelion) was in September 1989.
Due to the changes in orbit in time, Pluto has a unique atmosphere that transforms at various stages of its orbit. As its orbit approaches the Sun, its atmosphere begins to form. The frozen atmosphere melts as it comes closer. As Pluto moves further out its atmosphere will freeze.
Is Pluto a Planet
In August 2006, Pluto was demoted from a planet to a dwarf planet by the International Astronomical Union (IAU). It official name became ‘134340 Pluto’.
Features a large heart-shaped region known unofficially as Tombaugh Reggio which is about 1000 miles (1600km) wide.
Pluto is smaller than Planet Mercury and seven other moons including Callisto, Earth’s Moon, Europa, Ganymede, Io, Titan, and Triton.
It’s thin and almost entirely nitrogen.
Pluto rotates backward compared to Earth and most other planets. Pluto goes from east to west like Venus and Neptune. It also rotates on its side like Neptune.
A single day on Pluto is equal to 6.4 Earth days.
There are five Moons of Pluto: Charon, Hydra, Kerberos, Nix and Styx. Charon is the largest moon and has a diameter just over half that of Pluto.
Charon was discovered in 1978. Its diameter is 1212 km (753 miles) which is more than half as wide in size as Pluto and the Pluto-Charon system is like a double planet. Charon orbits Pluto every 6.4 days and has a synchronous orbit (the pair show the same face to each other all the time). To an observer on the planet, Charon appears to be stationary in the sky like a geostationary satellite orbiting the Earth.
Pluto and its moon Charon are actually a binary system. They are both orbiting around around a centre which is located between the two bodies.
NASA has for at least a decade been planning a fly-by of the solar systems most distant planet. The latest version, called New Horizons will be launched in 2006.
In the mid 1990’s NASA began a development of the Pluto-Kuiper Express spacecraft. In mid-September, 2000, however, NASA issued a stop-work order on the project. NASA then began to talk of a plan which would have a probe arrive before 2020 and that would cost less than $500 million (2002 dollars).
As a result Nasa started a competition and it chose a team called New Horizons to build a spacecraft that will study Pluto, Charon and several Kuiper Belt objects during a series of flybys. It will be launched in 2006 and will arrive in 2015.
What was Pluto-Kuiper Express?
NASA was developing a robotic reconnaissance mission to Pluto called Pluto-Kuiper Express. The Pluto mission would have used lightweight advanced-technology hardware components and advanced software technology. The Pluto mission plan called for launch when this technology was ready. It was scheduled for launch in 2004 and to arrive at Pluto in 2012.
In 2000 a website was started to save the Pluto-Kuiper Program (External Link).
The Planet Pluto Links:
- New Horizons:
- StarChild: The planet Pluto
- Is Pluto a giant comet?
- Astronomy for kids – learn about the planet Pluto with …
- Pluto-Kuiper Express
- HST Images of the Surface of Pluto
- Buie: Pluto Research
- The Planet Pluto
Any comments or suggestions on Planet Pluto, then click on Contact Info. | 0.835755 | 3.379281 |
It appeared, momentarily, like a 50-km tall banded flag. In mid-March, an energetic Coronal Mass Ejection directed toward a clear magnetic channel to Earth led to one of the more intense geomagnetic storms of recent years. A visual result was wide spread auroras being seen over many countries near Earth’s magnetic poles. Captured over Kiruna, Sweden, the image features an unusually straight auroral curtain with the green color emitted low in the Earth’s atmosphere, and red many kilometers higher up. It is unclear where the rare purple aurora originates, but it might involve an unusual blue aurora at an even lower altitude than the green, seen superposed with a much higher red. As the Sun continues near its top level of surface activity, colorful nights of auroras over Earth are likely to continue.
What if you saw your shadow on Mars and it wasn’t human? Then you might be the Opportunity rover currently exploring Mars. Opportunity has been exploring the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above in 2004, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity is continuing on its long trek exploring unusual terrain in Meridiani Planum which continues to yield clues to the ancient history of Mars, our Solar System, and even humanity.
Near the March 20 equinox the cold clear sky over Longyearbyen, Norway, planet Earth held an engaging sight, a total eclipse of the Sun. The New Moon’s silhouette at stages just before and after the three minute long total phase seems to sprout glistening diamonds and bright beads in this time lapse composite of the geocentric celestial event. The last and first glimpses of the solar disk with the lunar limb surrounded by the glow of the Sun’s inner corona give the impression of a diamond ring in the sky. At the boundaries of totality, sunlight streaming through valleys in the irregular terrain along the Moon’s edge, produces an effect known as Baily’s Beads, named after English astronomer Francis Baily who championed an explanation for the phenomenon in 1836. This sharp composition also shows off the array of pinkish solar prominences lofted above the edge of the eclipsed Sun.
Magnificent island universe NGC 2403 stands within the boundaries of the long-necked constellation Camelopardalis. Some 10 million light-years distant and about 50,000 light-years across, the spiral galaxy also seems to have more than its fair share of giant star forming HII regions, marked by the telltale reddish glow of atomic hydrogen gas. The giant HII regions are energized by clusters of hot, massive stars that explode as bright supernovae at the end of their short and furious lives. A member of the M81 group of galaxies, NGC 2403 closely resembles another galaxy with an abundance of star forming regions that lies within our own local galaxy group, M33 the Triangulum Galaxy. Spiky in appearance, bright stars in this colorful galaxy portrait of NGC 2403 lie in the foreground, within our own Milky Way.
As spring comes to planet Earth’s northern hemisphere, familiar winter constellation Orion sets in early evening skies and budding trees frame the Hunter’s stars. The yellowish hue of cool red supergiant Alpha Orionis, the great star Betelgeuse, mingles with the branches at the top of this colorful skyscape. Orion’s alpha star is joined on the far right by Alpha Tauri. Also known as Aldebaran and also a giant star cooler than the Sun, it shines with a yellow light at the head of Taurus, the Bull. Contrasting blue supergiant Rigel, Beta Orionis, is Orion’s other dominant star though, and marks the Hunter’s foot below center. Of course, the sword of Orion hangs from the Hunter’s three blue belt stars near picture center, but the middle star in the sword is not a star at all. A slightly fuzzy pinkish glow hints at its true nature, a nearby stellar nursery visible to the unaided eye known as the Orion Nebula.
It quickly went from obscurity to one of the brighter stars in Sagittarius — but it’s fading. Named Nova Sagittarii 2015 No. 2, the stellar explosion is the brightest nova visible from Earth in over a year. The featured image was captured four days ago from Ranikhet in the Indian Himalayas. Several stars in western Sagittarius make an asterism known as the Teapot, and the nova, indicated by the arrow, now appears like a new emblem on the side of the pot. As of last night, Nova Sag has faded from brighter than visual magnitude 5 to the edge of unaided visibility. Even so, the nova should still be easily findable with binoculars in dark skies before sunrise over the next week.
Birds don’t fly this high. Airplanes don’t go this fast. The Statue of Liberty weighs less. No species other than human can even comprehend what is going on, nor could any human just a millennium ago. The launch of a rocket bound for space is an event that inspires awe and challenges description. Pictured above, an Atlas V rocket lifts off carrying NASA’s Magnetospheric Multiscale Mission into Earth orbit 10 days ago to study the workings of the magnetosphere that surrounds and protects the Earth. From a standing start, the 300,000 kilogram rocket ship left to circle the Earth where the outside air is too thin to breathe. Rockets bound for space are now launched from somewhere on Earth about once a week. | 0.881715 | 3.823448 |
In a little over a month, scientists could be one step closer to understanding fundamental questions about the origins of our planet and the human race — and they will be learning from an asteroid that could threaten to destroy us.
The OSIRIS-REx Mission, headed by NASA and the University of Arizona, plan to launch an unmanned spacecraft on September 8 in the efforts to reach Bennu, a large near-Earth asteroid in August 2018, according to a website devoted to the mission.
The spacecraft will survey Bennu until a small vacuum-like device is capable of hovering above the asteroid and sucking up somewhere between 60 and and 400 grams of "gravel and soil" to bring back to Earth in the year 2023, according to Dante Lauretta, a professor of planetary science and cosmochemistry at the University of Arizona's Lunar and Planetary Laboratory, and the principal investigator on the OSIRIS-REx mission, who spoke to ABC News by phone from Cape Canaveral, Florida, where he is preparing for the final stages of the mission.
"We believe Bennu is a time capsule from the very beginnings of our solar system," Lauretta said. "So the sample can potentially hold answers to the most fundamental questions human beings ask, like 'Where do we come from?'"
As well as helping us understand how life on Earth began, the soil sample will also bring us closer to determining whether life occurred on Mars or Europa, a moon of Jupiter that scientists believe may be habitable due to the likelihood of lakes of liquid water lying beneath its frozen crust.
Lauretta said that as a near-Earth asteroid, Bennu once existed in what he described as a main asteroid belt, located between Mars and Jupiter. There, it was likely dislodged by a gravitational pull towards Saturn, sending it closer to us.
He said that the asteroid could indeed strike Earth, and cause tremendous destruction, but that we shouldn't be too frightened by it.
"Don't run out and buy asteroid insurance," he joked.
Bennu has a one in 2,700 chance of hitting Earth, and such an event wouldn't take place for 150 years, he said. People living in the year 2135 would know whether the asteroid posed a threat to hit Earth, he said. In such an instance, Bennu would enter what Lauretta described as a "keyhole" located between the Earth and the moon that would send it in the direction of Earth.
A one in 2,700 chance isn't too insignificant, however. Your chance of being killed by "firearms discharge" is roughly one in 7,944, according to the National Safety Council.
Lauretta said that by the time that it would strike, we would likely have the technology to destroy Bennu, although he acknowledged that we don't have that capacity right now. He mentioned "nukes" as a potential means to protect Earth from Bennu, as well as what he described as a "gravity tractor," or a space craft that would disrupt Bennu's gravitational pull and send it careening off course from Earth.
"I wish I could be around in 2135 to see what happens," Lauretta said.
Lauretta, who started the OSIRIS-REx Mission in research form in 2004, said he's feeling "anxious and proud" in the days preceding its takeoff. His team, which had as many as 450 full time employees, is now scaling down as the launch approaches.
"It's a tense moment for all of us," he said.
In addition to preparing for the mission, Lauretta is trying to get a younger generation interested in his subject. "Xtronaut," a board game he created to teach children about space exploration, retails on Amazon for $35. | 0.85796 | 3.017675 |
Earth to Mars: Come closer
Jupiter may be king of the mythological gods. But, among the planets, it's Mars' time to shine. When it draws closer to Earth than it has in some 60,000 years next Wednesday, it will be brighter than any planet except Venus. And, since Venus makes only a fleeting appearance at sundown, it won't steal the Red Planet's show.
At 5.52 a.m. eastern daylight time Aug. 27, Mars will be a "mere" 34,848,754 miles (55,758,006 kilometers) away. That's 1,188 miles (1,900 km) closer to Earth than Mars came in 1924.
As the Observer's Handbook of the Royal Astronomical Society of Canada points out, the opportunity to study Mars from Earth will be "as good
as it gets" over the next few weeks. The planet will reach its maximum possible angular diameter on the sky of 25.1"
Located 25 degrees south of the celestial equator, it will rise high enough above the horizon for easy viewing in many locations - 30 degrees for an observer at 45 degrees north latitude and higher up farther to the south. Mars will not come closer until Aug. 28, 2287. So grab the children on a clear evening for a rare opportunity to see Mars at its best.
You don't need a telescope to enjoy the show. Just watching the progress of the brilliant red disk through the stars in coming weeks can be fascinating. Mars has been moving backward relative to the stars. It will halt this westward motion Sept. 29 and begin to move eastward like the Moon, stars, and other planets as the relative motion of Earth and Mars changes.
The view through even a modest telescope or binoculars should be stunning. Mars is presenting much of its southern hemisphere. It's summer there, so there won't be much of a southern polar cap.
However, many prominent markings should be easily seen. You'll be looking at desert. Even the darker features - once mistakenly thought to be vegetation - are dry.
There is a caveat. Martian haze and thin ice clouds - to say nothing of a dust storm - can dim the view. So far, there's no sign of the kind of dust pall that ruined viewing during Mars' 2001 close approach.
There's help for observers with Internet access. Space.com has posted a complete viewer's guide on its website: www.SPACE.com/spacewatch/where_is_mars.html. NASA promises to make Hubble Space Telescope images available through its nasa.gov website beginning shortly after Aug. 27.
NASA expects the Hubble images to be "the sharpest views of Mars ever taken from Earth," showing details as small as 17 miles (24 km) across. Such detail can help you identify what you see with your own small telescope or binoculars.
And yes, there are other things to see in the sky - the usual stellar objects and some of the other planets. Jupiter, now dimmer than it has been, will become a morning object next month. Venus is beginning to emerge again as the "evening star." Yet this time really belongs to Mars. Look for it rising late in the evening.
• Skywatch is an occasional column. | 0.808284 | 3.031994 |
Also found in: Dictionary, Wikipedia.
Dione(dīō`nē), in astronomy, one of the named moons, or natural satellites, of SaturnSaturn,
in astronomy, 6th planet from the sun. Astronomical and Physical Characteristics of Saturn
Saturn's orbit lies between those of Jupiter and Uranus; its mean distance from the sun is c.886 million mi (1.
..... Click the link for more information. . Also known as Saturn IV (or S4), Dione is 695 mi (1,120 km) in diameter, orbits Saturn at a mean distance of 234,500 mi (377,400 km), and has an orbital period of 2.737 earth days—the rotational period is unknown but is assumed to be the same as the orbital period. It was discovered in 1684 by the Italian-French astronomer Gian Domenico CassiniCassini
, name of a family of Italian-French astronomers, four generations of whom were directors of the Paris Observatory. Gian Domenico Cassini, 1625–1712, was born in Italy and distinguished himself while at Bologna by his studies of the sun and planets,
..... Click the link for more information. . Aside from TitanTitan
, in astronomy, the largest of the named moons, or natural satellites, of Saturn. Also known as Saturn VI (or S6), Titan is 3,200 mi (5,150 km) in diameter, orbits Saturn at a mean distance of 759,209 mi (1,221,830 km), and has equal orbital and rotational periods of 15.
..... Click the link for more information. , Dione is the densest of Saturn's satellites; it is believed to be composed primarily of water ice with a considerable fraction of denser material, such as silicate rock. The trailing hemisphere is more heavily cratered than the leading hemisphere, which is the reverse of the cratering on most of the other Saturnian satellites. Another moon, HeleneHelene
, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XII (or S12), Helene is an irregularly shaped (nonspherical) body measuring about 22 mi (36 km) by 20 mi (32 km) by 18 mi (30 km); it orbits Saturn at a mean distance of 234,500
..... Click the link for more information. , is co-orbital with Dione; that is, it orbits Saturn at the same distance as Dione, and precedes Dione by about 60°. Dione also forms a satellite pair with EnceladusEnceladus
, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn II (or S2), Enceladus is 310 mi (500 km) in diameter, orbits Saturn at a mean distance of 147,900 mi (238,020 km), and has equal orbital and rotational periods of 1.
..... Click the link for more information. ; that is, the two moons interact gravitationally.
Dione,in Greek religion and mythology, earth goddess. In some legends she is the daughter of Oceanus and Tethys; in others she is a Titaness, born to Uranus and Gaea. In yet another version she is the mother of Aphrodite. Her name is the feminine form of Zeus. Her cult was associated with the oracle at DodonaDodona
, in Greek religion, the oldest oracle, in inland Epirus, near modern Janina, sacred to Zeus and Dione. According to Herodotus, an old oak tree there became an oracle when a black dove, from Egyptian Thebes, settled on it.
..... Click the link for more information. .
Dione(dÿ-oh -nee) A satellite of Saturn, discovered in 1684 by Giovanni Domenico Cassini. It has a diameter of 1118 km and density of 1.4 g cm–3, and is slightly larger than the satellite Tethys. An important characteristic of Dione is the nonuniformity of its brightness. The trailing hemisphere is dark, with an albedo of approximately 0.3, whereas the brightest features of the leading hemisphere have an albedo of approximately 0.6. Only Iapetus, of the Saturn system, displays a greater variation of brightness between the hemispheres. The surface shows evidence of a number of craters of 30–40 km, with a few large craters 165 km or more in diameter. There are some broad ridges in the southern part of the heavily cratered plains, with a long linear valley more than 500 km in length near the south pole. Dione's relatively high density compared with the neighboring satellites indicates a higher rock content of the interior. The most prominent feature is Amata, a crater 240 km in diameter associated with a system of bright wispy features that extend over the trailing hemisphere. The bright streaks on the surface first imaged by the two Voyager probes have been shown by the Cassini probe to be a vast system of linear features scarring the satellite's surface. A minor satellite, Helene, has been discovered to share the orbit of Dione. See also Table 2, backmatter.
A satellite of Saturn that orbits at a mean distance of 2.35 × 105 miles (3.78 × 105 kilometers) and has a diameter of about 700 miles (1120 kilometers). | 0.815863 | 3.160672 |
The bright stars in this constellation are not greater than the fourth magnitude. It has several binary stars; the notable ones include:
- α Chamaeleontis or Alpha Chamaeleontis: It is the brightest star of this constellation. Its apparent visual magnitude is about 4.066 and is approximately 63.5 light years distant from the earth.
- β Chamaeleontis or Beta Chamaeleontis: It is the third brightest star in the constellation. A main sequence star, its magnitude varies from 4.24 to 4.30 and is about 270 light years distant from the earth.
- δ1 Chamaeleontis or Delta Chamaeleontis: This is a binary star that consists of two similar stars separated by 0.6”.
- ε Chamaeleontis: The star is similar to Delta Chamaeleontis but the similar stars are separated by 0.9”.
- R Chamaeleontis: It is a Mira–type variable star with a period of 334 days. Its apparent magnitude is about 7.5 to 14.
- CT Chamaeleontis: It is a T Tauri star and is believed to be a brown dwarf. Its apparent magnitude varies between 12.31 and 12.43 and is approximately 540 light years distant from the earth.
- HD 63454: it is a K–type main sequence star with an apparent magnitude of about 9.40. Lying near the south celestial pole, it is 116.7 light years away from the earth and can be seen in a small telescope.
A few notable deep sky objects are:
- Eta Chamaeleontis Cluster: It is an open star cluster centered on the star Eta Chamaeleontis. Also known as Mamajek, it was discovered in 1999 and was the first one to be discovered due to the X–ray emissions from its member stars. It is estimated to be around eight million years old and consists of about 12 relatively young stars. It lies approximately 316 light years away from the earth.
- Chamaeleon cloud complex: It contains numerous molecular clouds located between 400 and 600 light years from the solar system that are forming a low–mass T Tauri type stars.
- NGC 3195: A bright planetary nebula, it lies halfway between the stars Delta and Zeta Chamaeleontis. The southernmost bright nebula known, it is not visible from the northern hemisphere at all. Its magnitude is about 11.6 and is approximately 5,500 light years away from the earth.
Seen at latitudes between 0° and –90°, it lies in the second quadrant of the southern hemisphere.
It occupies an area of 132 square degrees, making it one of the smallest and 79th in size among all the other constellations. The closest star is 63.1 light years distant from the earth and hence, it can be said that Chamaeleon is 270 light years distant from the earth.
There are no myths associated with this constellation as it was created for scientific reasons. Jodocus Hondius, the Dutch cartographer depicted this constellation as a chameleon that was sticking its tongue out to catch a fly. The fly is represented by its neighbouring Musca constellation.
Chamaeleon is surrounded by the constellations like Apus, Carina, Mensa, Musca, Octans and Volans. | 0.815202 | 3.692299 |
The sun’s magnetic field will reverse polarity at some point in the coming weeks, sending ripples to the edge of interstellar space
The sun is set to “flip upside down” within weeks as its magnetic field reverses polarity in an event that will send ripple effects throughout the solar system.
Although it may sound like a catastrophic occurrence, there’s no need to run for cover. The sun switches its polarity, flipping its magnetic north and south, once every eleven years through an internal mechanism about which little is understood.
The swap could however cause intergalactic weather fronts such as geomagnetic storms, which can interfere with satellites and cause radio blackouts.
Nasa said in August that the change would happen in three to four months time, but it is impossible to give a more specific date. Scientist won’t know for around another three weeks whether the flip is complete.
The impact of the transfer will be widespread as the sun’s magnetic field exerts influence well beyond Pluto, past Nasa’s Voyager probes positioned near the edge of interstellar space.
The event will be watched closely by researchers at Stanford University’s Wilcox Solar Observatory, which monitors the sun’s magnetic field on a daily basis.
Todd Hoeksema, director of the Wilcox Solar Observatory, said the polarity change is built up throughout the eleven year cycle through areas of intense magnetic activity known as sunspots which gradually move towards the poles, eroding the existing opposite polarity.
Eventually, the magnetic field reduces to zero, before rebounding with the opposite polarity. “It’s kind of like a tide coming in or going out,” Hoeksema said. “Each little wave brings a little more water in, and eventually you get to the full reversal.”
One of the most noticeable effect on Earth will be a boost in the occurrence, range and visibility of auroras – the Northern Lights. “It’s not a catastrophic event, it’s a large scale event that has some real implications, but its not something we need to worry about,” added Hoeksema. | 0.86708 | 3.446516 |
CAMBRIDGE, Mass., July 21 (UPI) -- Earth's aurorae, or Northern and Southern Lights, are spectacular, but on a distant "hot Jupiter" they could be 1,000 times brighter, U.S. astronomers say.
Researchers at the Harvard-Smithsonian Center for Astrophysics said new research suggests they also would ripple from equator to poles due to the planet's proximity to any stellar eruptions, bathing the entire planet in an otherworldly spectacle.
"I'd love to get a reservation on a tour to see these aurorae!" said lead author Ofer Cohen.
Earth's aurorae are created when energetic particles from the Sun slam into our planet's magnetic field, which guides them to the poles to collide with molecules in the atmosphere that begin to glow like a neon sign.
Cohen and his colleagues used computer models to study what would happen if a gas giant in a close orbit, just a few million miles from its star, were hit by such a solar eruption.
A "hot Jupiter" would feel a stronger and more focused blast, they said.
"The impact to the exoplanet would be completely different than what we see in our solar system, and much more violent," said co-author Vinay Kashyap.
Over the course of about 6 hours, the aurora would ripple up and down from the equator toward the planet's north and south poles before gradually fading away, the researchers said. | 0.881784 | 3.231877 |
The zodiacal constellation of Sagittarius resides on the ecliptic plane and was one of the original 48 constellations charted by Ptolemy to be later adopted as a modern constellation by the IAU. It spans 867 square degrees of sky and ranks 15th in constellation size. It has 7 primary stars in its main asterism and 68 Bayer Flamsteed designation stars within its confines. Sagittarius is bordered by the constellations of Aquila, Scutum, Serpens Cauda, Ophiuchus, Scorpius. Corona Australis, Telescopium, Indus, Microscopium and Capricornus. It is visible to all observers located at latitudes between +55° and ?90° and is best seen at culmination during the month of August.
The easily recogniged “tea pot” shape of Sagittarius was well known in mythology as being represented by the half-man, half-horse – the Centaur. According to some legends, he was the offspring of of Philyra and Saturn. Named Chiron, he turned himself into a horse to hide from his jealous wife and was eventually immortalized in the stars. He is often depicted as an archer as well, with his arrow pointed directly at the red heart of the Scorpion – Antares. Sagittarius may represent the son of Pan, who invented archery and was sent to entertain the Muses who threw a laurel wreath at his feet. No matter what identity you choose, one thing is for certain – there’s no mistaking the presence of the nearby Sagittarius arm of the Milky Way!
(Since the constellation of Sagittarius is simply slopping over with deep sky objects, creating a small, workable chart here would be very confusing. For this reason, I have only chosen a few of my favorite objects to highlight and I hope you enjoy them, too!)
Let’s begin our binocular tour of Sagittarius with its alpha star – the “a” symbol on our map. Located far south in the constellation, Alpha Sagittarii is far from being the brightest of its stars and goes by the traditional name of Rukbat – the “knee of the Archer”. It’s nothing special. Just a typical blue, class AB dwarf star located about 170 light years from Earth, but it often gets ignored because of its position. Have a look at Beta while you’re there, too. It’s the “B” symbol on our map. That’s right! It’s a visual double star and its name is Arkab – the “hamstring”. Now, power up in a telescope. Arkab Prior is the westernmost and it truly is a binary star accompanied by a 7th magnitude dwarf star and seperated by about 28 arcseconds. It’s located about 378 light years from Earth. Now, hop east for Arkab Posterior. It is a spectral type F2 giant star, but much closer at 137 light years in distance.
Now turn your attention towards Epsilon Sagittarii – the backwards “3” symbol on our chart. Kaus Australis is actually the brightest star in the bottom righthand corner of the teapot and the brightest of all the stars in Sagittarius and the 36th brightest in the night sky. Hanging out in space some 134 light years from our solar system, this A-class giant star is much hotter than most of its main sequence peers and spinning over 70 times faster on its axis than our Sun. This rapid movement has caused a shell to form around the star, dimming its brightness… But not nearly as dim as its 14th magnitude companion! That’s right… Epsilon is a binary star. The disparate companion is well seperated at 32 arc seconds, but will require a larger telescope to pick away from its bright companion!
Ready for more? Then have a look at Gamma – the “Y” symbol on our map. Alnasl, the “arrowhead” is two star systems that share the same name. If you have sharp eyes, you can even split this visual double star without aid! However, take a look in the telescope… Gamma-1 Sagittarii is a Cepheid 1500 light year distant variable star in disguise. It drops by almost a full stellar magnitude in just a little under 8 days! Got a big telescope? Then take a closer look, because Gamma-1 also shows evidence of being a close binary star, as well has having two more distant 13th magnitude companions, W Sagittarii B, and C separated by 33 and 48 arcseconds respectively. How about Gamma-2? It’s just a regular type-K giant star – but it’s only 96 light years from Earth!
Located just slightly more than a fingerwidth above Gamma Sagittarii and 5500 light-years away, NGC 6520 (RA 18 03 24 Dec -27 53 00) is a galactic star cluster which formed millions of years ago. Its blue stars are far younger than our own Sun, and may very well have formed from what you don’t see nearby – a dark, molecular cloud. Filled with dust, Barnard 86 literally blocks the starlight coming from our galaxy’s own halo area in the direction of the core. To get a good idea of just how much light is blocked by B 86, take a look at the star SAO 180161 on the edge. Behind this obscuration lies the densest part of our Milky Way! This one is so dark that it’s often referred to as the “Ink Spot.” While both NGC 6520 and B 86 are about the same distance away, they don’t reside in the hub of our galaxy, but in the Sagittarius Spiral Arm. Seen in binoculars as a small area of compression, and delightfully resolved in a telescope, you’ll find this cluster is on the Herschel “400” list and many others as well.
Are you ready for a whirlwind tour of the Messier Catalog objects with binoculars or a small telescope? Then let’s start at the top with the “Nike Swoosh” of M17.
Easily viewed in binoculars of any size and outstanding in every telescope, the 5000 light-year distant Omega Nebula was discovered by Philippe Loys de Chéseaux in 1745-46 and later (1764) cataloged by Messier as object 17 (RA 18 20 26 Dec -16 10 36). This beautiful emission nebula is the product of hot gases excited by the radiation of newly born stars. As part of a vast region of interstellar matter, many of its embedded stars don’t show up in photographs, but reveal themselves beautifully to the eye at the telescope. As you look at its unique shape, you realize many of these areas are obscured by dark dust, and this same dust is often illuminated by the stars themselves. Often known as “The Swan,” M17 will appear as a huge, glowing check mark or ghostly “2” in the sky – but power up if you use a larger telescope and look for a long, bright streak across its northern edge with extensions to both the east and north. While the illuminating stars are truly hidden, you will see many glittering points in the structure itself and at least 35 of them are true members of this region, which spans up to 40 light-years and could form up to 800 solar masses. It is awesome…
Keeping moving south and you will see a very small collection of stars known as M18, and a bit more south will bring up a huge cloud of stars called M24. This patch of Milky Way “stuff” will show a wonderful open cluster – NGC 6603 – to average telescopes and some great Barnard darks to larger ones. M24 is often referred to as the “Small Sagittarius Star Cloud”. This vast region is easily seen unaided from a dark sky site and is a stellar profusion in binoculars. Telescopes will find an enclosed galactic cluster – NGC 6603 – on its northern border. For those of you who prefer a challenge, look for Barnard Dark Nebula, B92, just above the central portion.
Now we’re going to shift to the southeast just a touch and pick up the M25 open cluster. M25 is a scattered galactic cluster that contains a cephid variable – U Sagittarii. This one is a quick change artist, going from magnitude 6.3 to 7.1 in less than seven days. Keep an eye on it over the next few weeks by comparing it to the other cluster members. Variable stars are fun! Head due west about a fist’s width to capture the next open cluster – M23. From there, we are dropping south again and M21 will be your reward. Head back for your scope and remember your area, because the M20 “Triffid Nebula” is just a shade to the southwest. Small scopes will pick up on the little glowing ball, but anything from about 4″ up can see those dark dust lanes that make this nebula so special. The “Trifid” nebula appears initially as two widely spaced stars – one of which is a low power double – each caught in its own faint lobe of nebulosity. Keen eyed observers will find that the double star – HN 40 – is actually a superb triple star system of striking colors! The 7.6 magnitude primary appears blue. Southwest is a reddish 10.7 magnitude secondary while a third companion of magnitude 8.7 is northwest of the primary.
Described as “trifid” by William Herschel in 1784, this tri-lobed pattern of faint luminosity broken by a dark nebula – Barnard 85 – is associated with the southern triple. This region is more brightly illuminated due to the presence of the star cluster and is suffused with a brighter, redder reflection nebula of hydrogen gas. The northern part of the Trifid (surrounding the solitary star) is fainter and bluer. It shines by excitation and is composed primarily of doubly ionized oxygen gas. The entire area lies roughly 5000 light-years away. What makes M20 the “Trifid” nebula, are the series of dark, dissecting dust lanes meeting at the nebula’s east and west edges, while the southernmost dust lane ends in the brightest portion of the nebula. With much larger scopes, M20 shows differences in concentration in each of the lobes along with other embedded stars. It requires a dark night, but the Trifid is worth the hunt. On excellent nights of seeing, larger scopes will show the Trifid much as it appears in black and white photographs!
You can go back to the binoculars again, because the M8 “Lagoon Nebula” is south again and very easy to see. Easily located about three finger-widths above the tip of the teapot’s spout (Al Nasl), M8 is one of Sagittarius’ premier objects. This combination of emission/reflection and dark nebula only gets better as you add an open cluster. Spanning a half a degree of sky, this study is loaded with features. One of the most prominent is a curving dark channel dividing the area nearly in half. On its leading (western) side you will note two bright stars. The southernmost of this pair (9 Sagittarii) is thought to be the illuminating source of the nebula. On the trailing (eastern) side, is brightly scattered cluster NGC 6530 containing 18 erratically changing variables known as “flare stars.” For large scopes, and those with filters, look for small patches of dark nebulae called “globules.” These are thought to be “protostar” regions – areas where new stars undergo rapid formation. Return again to 9 Sagittarii and look carefully at a concentrated portion of the nebula west-southwest. This is known as the “Hourglass” and is a source of strong radio emission.
This particular star hop is very fun. If you have children who would like to see some of these riches, point out the primary stars and show them how it looks like a dot-to-dot “tea kettle.” From the kettle’s “spout” pours the “steam” of the Milky Way. If you start there, all you will need to do is follow the “steam” trail up the sky and you can see the majority of these with ease.
At the top of the “tea kettle” is Lambda. This is our marker for two easy binocular objects. The small M28 globular cluster is quite easily found just a breath to the north/northwest. The larger, brighter and quite wonderful globular cluster M22 is also very easily found to Lambda’s northeast. Ranking third amidst the 151 known globular clusters in total light, M22 is probably the nearest of these incredible systems to our Earth, with an approximate distance of 9,600 light-years. It is also one of the nearest globulars to the galactic plane. Since it resides less than a degree from the ecliptic, it often shares the same eyepiece field with a planet. At magnitude 6, the class VII M22 will begin to show individual stars to even modest instruments and will burst into stunning resolution for larger aperture. About a degree west-northwest, mid-sized telescopes and larger binoculars will capture the smaller 8th magnitude NGC 6642 (RA 18 31 54 Dec -23 28 34). At class V, this particular globular will show more concentration toward the core region than M22. Enjoy them both!
Now we’re roaming into “binocular possible” but better with the telescope objects. The southeastern corner of the “tea kettle” is Zeta, and we’re going to hop across the bottom to the west. Starting at Zeta, slide southwest to capture globular cluster M54. Keep heading another three degrees southwest and you will see the fuzzy ball of M70. Just around two degrees more to the west is another globular that looks like M70’s twin. The small globular M55 is out there in “No Man’s Land” about a fist’s width away east/south east of Zeta .
Ready for a big telescope challenge? Then try your hand at one the sky’s most curious galaxies – NGC 6822. This study is a telescopic challenge even for skilled observers. Set your sights roughly 2 degrees northeast of easy double 54 Sagittarii, and have a look at this distant dwarf galaxy bound to our own Milky Way by invisible gravitational attraction…
Named after its discoverer (E. E. Barnard – 1884), “Barnard’s Galaxy” is a not-so-nearby member of our local galaxy group. Discovered with a 6″ refractor, this 1.7 million light-year distant galaxy is not easily found, but can be seen with very dark sky conditions and at the lowest possible power. Due to large apparent size, and overall faintness (magnitude 9), low power is essential in larger telescopes to give a better sense of the galaxy’s frontier. Observers using large scopes will see faint regions of glowing gas (HII regions) and unresolved concentrations of bright stars. To distinguish them, try a nebula filter to enhance the HII and downplay the star fields. Barnard’s Galaxy appears like a very faint open cluster overlaid with a sheen of nebulosity, but the practiced eye using the above technique will clearly see that the “shine” behind the stars is extragalactic in nature.
Now look less than a degree north-northwest to turn up pale blue-green NGC 6818 – the “Little Gem” planetary. Easily found in any size scope, this bright and condensed nebula reveals its annular nature in larger scopes but hints at it in scopes as small as 6″. Use a super wide field long-focus eyepiece to frame them both!
Be sure to get a good star chart and enjoy the constellation of Sagittarius to its fullest potential – there’s lots more out there! | 0.886207 | 3.450567 |
Astronomers are getting a close-up look at a cosmic eating machine: a spinning black hole that devours the mass equivalent of two Earths per hour, verging on the limit of its feeding ability.
Supermassive black holes can weigh as much as a billion suns or more and are thought to reside at the centers of most, if not all, large galaxies. Their gravity is so powerful it traps even light, making black holes invisible. Their presence is inferred by watching the motions of stars and gas around them, along with the radiation that’s generated in their frenzied vicinities.
The behemoth of interest in the new close-up study, which will be published in the May 28 issue of the journal Nature, lies at the center of a distant active galaxy known as 1H0707-495. Using data from the European Space Agency’s XMM-Newton observatory, astronomers analyzed X-rays emitted during the black hole’s feeding frenzy.
As matter swirls in toward a black hole, gravity makes it travel at significant fractions of light-speed. That generates X-rays and other radiation that can give astronomers information about the spin of the black hole and its size, among other details.
In this case, the astronomers say they are tracking matter that’s within twice the radius of the black hole itself.
Specifically, the XMM-Newton detections suggested the galaxy’s core is much richer in iron than the rest of the galaxy. In addition, there was a time lag of 30 seconds between changes in the X-ray light observed directly and those seen in its reflection from the disk. From this delay, the astronomers estimate the black hole weighs about 3 million to 5 million solar masses – modest by supermassive black hole standards.
The team will continue to track the galaxy and map out the accreting process of this supermassive black hole. Far from being a steady process, like muddy water slipping down a plughole, a feeding black hole is a messy eater.
“Accretion is a very messy process because of the magnetic fields that are involved,” said study scientist Andrew Fabian of the University of Cambridge.
via Close-up Look at Black Hole Reveals Feeding Frenzy – Yahoo! News. | 0.843616 | 3.745945 |
|GRAIL primary mission global gravity map, centered on 0°N, 355°E, from animation released Dec. 5, 2012. Science Visualization Studio (SVS), GSFC [NASA/JPL/MIT].|
Beneath its heavily pockmarked surface, the moon’s interior bears remnants of the very early solar system. Unlike Earth, where plate tectonics has essentially erased any trace of the planet’s earliest composition, the moon’s interior has remained relatively undisturbed over billions of years, preserving a record in its rocks of processes that occurred in the solar system’s earliest days.
Now scientists at MIT, NASA, the Jet Propulsion Laboratory and elsewhere have found evidence that, beneath its surface, the moon’s crust is almost completely pulverized. The finding suggests that, in its first billion years, the moon — and probably other planets like Earth — may have endured much more fracturing from massive impacts than previously thought.
The startling observations come from data collected by NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission. Since March, the mission’s twin spacecraft, named Ebb and Flow, have been orbiting the moon and measuring its gravitational field.
From GRAIL’s measurements, planetary scientists have now stitched together a high-resolution map of the moon’s gravity — a force created by surface structures such as mountains and craters, as well as deeper structures below the surface. The resulting map reveals an interior gravitational field consistent with an incredibly fractured lunar crust.
“It was known that planets were battered by impacts, but nobody had envisioned that the [moon’s] crust was so beaten up,” says MIT’s Maria Zuber, who leads the GRAIL mission and is the E.A. Griswold Professor of Geophysics in the Department of Earth, Atmospheric and Planetary Sciences. “This is a really big surprise, and is going to cause a lot of people to think about what this means for planetary evolution.”
Zuber and her colleagues detail their findings from GRAIL in three papers published this week in Science.
GRAIL’s lunar gravity map has also revealed numerous structures on the moon’s surface that were unresolved by previous gravity maps of any planet, including volcanic landforms, impact basin rings, and many simple, bowl-shaped craters. From GRAIL’s measurements, scientists have determined that the moon’s crust, ranging in thickness from 34 to 43 kilometers, is much thinner than planetary geologists had previously suspected. The crust beneath some major basins is nearly nonexistent, indicating that early impacts may have excavated the lunar mantle, providing a window into the interior.
To generate the gravity map, GRAIL’s two probes measure the changing distance between themselves as they orbit in tight formation around the moon. As one of the probes flies over a large mass, such as a mountain or dense, underground rock, the stronger local gravity will pull that probe ahead, widening the space between the two spacecraft. Scientists can translate this changing distance into a gravitational map, representing the gravity produced by both the surface structures and the interior.
To find the gravitational field for the moon’s interior alone, Zuber’s team used topographic measurements from another of their instruments, a laser altimeter aboard the Lunar Reconnaissance Orbiter, a separate spacecraft in orbit around the moon. The scientists calculated the gravitational field expected to be produced by the moon’s topography — its surface structures alone — then subtracted that field from the field measured by GRAIL.
“It’s essentially like removing a veil to reveal the gravity due to the inside of the planet,” Zuber says. “And when we saw those maps, we were just speechless.”
|The GRAIL primary science mission also succeeded in definitively mapping the thickness of the Moon's outer crust, shown in another global animation centered over the thickest zones on the lunar farside. The South Pole-Aitken basin, oldest and largest identified impact at 4.1 billion years, hosts some of the thinnest outer crust. The mission has increased the likelihood that fragments of the Moon's deeper zones will eventually be found on the surface, excavated by complex craters located on or near the basin's rim [NASA/JPL/MIT].|
The interior map did reveal long, linear structures of denser material, which Zuber and her team believe to be buried lunar dikes — formed from magma that seeped into large fractures in the crust, and then solidified into dense walls of rock. These dikes represent evidence for expansion of the moon in its earliest history. But overall, 98 percent of the lunar crust is fragmented — a clear remnant of very early, very massive impacts.
“This is interesting for the moon,” Zuber says. “But what it also means is that every other planet was being bombarded like this.” The resulting fractures, she says, affect the way a planetary body loses heat and also provide a pathway for the transport of interior fluids.
David Kring, a senior staff scientist at the Lunar and Planetary Institute in Houston, says knowing the extent of pulverization in the moon’s crust is an essential detail needed to determine the moon’s bulk composition. Such information would go a long way toward identifying the processes the formed the moon and other planets.
“The staggering quality of the data reported by Professor Zuber and her colleagues is amazing,” says Kring, who was not involved in the research. “The data are exciting because they foretell far more insights than are captured in these initial three papers.”
NASA has scheduled a news conference to discuss the planned deorbiting and impact of the GRAIL spacecraft, December 13.
In addition to GRAIL’s discoveries, Zuber says another major accomplishment has been the performance of the spacecraft themselves. To achieve the mission’s science goals, the two probes, which can travel more than 200 kilometers apart, needed to be able to measure changes in the distance between them to within a few tenths of a micron per second. But GRAIL actually outperformed its measurement requirements by about a factor of five, resolving changes in spacecraft distance to several hundredths of a micron per second — one twenty-thousandth the velocity that a snail travels.
“On this mission, with two spacecraft, everything had to go perfectly twice,” Zuber says, adding proudly: “Imagine you’re a parent raising a twins, and your children sit down at the piano and play a duet perfectly. That’s how it feels.” | 0.898573 | 3.825333 |
Scientists analyzing recent data from NASA's Voyager and Cassini spacecraft have calculated that Voyager 1 could cross over into the frontier of interstellar space at any time and much earlier than previously thought. The findings are detailed in this week's issue of the journal Nature.
Data from Voyager's low-energy charged particle instrument, first reported in December 2010, have indicated that the outward speed of the charged particles streaming from the sun has slowed to zero. The stagnation of this solar wind has continued through at least February 2011, marking a thick, previously unpredicted "transition zone" at the edge of our solar system.
"There is one time we are going to cross that frontier, and this is the first sign it is upon us," said Tom Krimigis, prinicipal investigator for Voyager's low-energy charged particle instrument and Cassini's magnetospheric imaging instrument, based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. | 0.833326 | 3.058925 |
NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space. Data obtained from Voyager over the last year reveal this new region to be a kind of cosmic purgatory. In it, the wind of charged particles streaming out from our sun has calmed, our solar system's magnetic field has piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space.
"Voyager tells us now that we're in a stagnation region in the outermost layer of the bubble around our solar system," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "Voyager is showing that what is outside is pushing back. We shouldn't have long to wait to find out what the space between stars is really like."
Although Voyager 1 is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years. | 0.849493 | 3.323373 |
Several studies have claimed to have found periodic variations, with the probability of giant impacts increasing and decreasing in a regular pattern. Now a new analysis by Coryn Bailer-Jones from the Max Planck Institute for Astronomy (MPIA), published in the Monthly Notes of the Royal Astronomical Society, shows those simple periodic patterns to be statistical artifacts. His results indicate either that the Earth is as likely to suffer a major impact now as it was in the past, or that there has been a slight increase impact rate events over the past 250 million years.
Barringer Crater, also known as Meteor Crater, in Arizona. This crater was formed around 50,000 years ago by the impact of a nickel-iron meteorite. Near the top of the image, the visitors center, complete with tour buses on the parking lot, provides a sense of scale.
Credit: National Map Seamless Viewer/US Geological Service
Giant impacts by comets or asteroids have been linked to several mass extinction events on Earth, most famously to the demise of the dinosaurs 65 million years ago. Nearly 200 identifiable craters on the Earth's surface, some of them hundreds of kilometers in diameter, bear witness to these catastrophic collisions.
Understanding the way impact rates might have varied over time is not just an academic question. It is an important ingredient when scientists estimate the risk Earth currently faces from catastrophic cosmic impacts.
Since the mid-1980s, a number of authors have claimed to have identified periodic variations in the impact rate. Using crater data, notably the age estimates for the different craters, they derive a regular pattern where, every so-and-so-many million years (values vary between 13 and 50 million years), an era with fewer impacts is followed by an era with increased impact activity, and so on.
One proposed mechanism for these variations is the periodic motion of our Solar System relative to the main plane of the Milky Way Galaxy. This could lead to differences in the way that the minute gravitational influence of nearby stars tugs on the objects in the Oort cloud, a giant repository of comets that forms a shell around the outer Solar System, nearly a light-year away from the Sun, leading to episodes in which more comets than usual leave the Oort cloud to make their way into the inner Solar System – and, potentially, towards a collision with the Earth. A more spectacular proposal posits the existence of an as-yet undetected companion star to the Sun, dubbed “Nemesis”. Its highly elongated orbit, the reasoning goes, would periodically bring Nemesis closer to the Oort cloud, again triggering an increase in the number of comets setting course for Earth.
For MPIA's Coryn-Bailer-Jones, these results are evidence not of undiscovered cosmic phenomena, but of subtle pitfalls of traditional (“frequentist”) statistical reasoning. Bailer-Jones: “There is a tendency for people to find patterns in nature that do not exist. Unfortunately, in certain situations traditional statistics plays to that particular weakness.”
That is why, for his analysis, Bailer-Jones chose an alternative way of evaluating probabilities (“Bayesian statistics”), which avoids many of the pitfalls that hamper the traditional analysis of impact crater data. He found that simple periodic variations can be confidently ruled out. Instead, there is a general trend: From about 250 million years ago to the present, the impact rate, as judged by the number of craters of different ages, increases steadily.
There are two possible explanations for this trend. Smaller craters erode more easily, and older craters have had more time to erode away. The trend could simply reflect the fact that larger, younger craters are easier for us to find than smaller, older ones. “If we look only at craters larger than 35 km and younger than 400 million years, which are less affected by erosion and infilling, we find no such trend,” Bailer-Jones explains.
On the other hand, at least part of the increasing impact rate could be real. In fact, there are analyses of impact craters on the Moon, where there are no natural geological processes leading to infilling and erosion of craters, that point towards just such a trend.
Whatever the reason for the trend, simple periodic variations such as those caused by Nemesis are laid to rest by Bailer-Jones' results. “From the crater record there is no evidence for Nemesis. What remains is the intriguing question of whether or not impacts have become ever more frequent over the past 250 million years,” he concludes.
Contact informationCoryn Bailer-Jones
Dr. Markus Pössel | Max-Planck-Institut
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
26.09.2017 | Life Sciences
26.09.2017 | Physics and Astronomy
26.09.2017 | Information Technology | 0.923452 | 4.031994 |
What ever happened to the Manned Space Stations? (Feb, 1965)
What ever happened to the Manned Space Stations?
By Dr. Wernher von Braun
Director of NASA’s George C. Marshall Space Flight Center, Huntsville, Ala.
DURING the years before Sputnik, several writers, including myself, predicted that one of the first objectives of manned space flight would be to establish one or more orbiting space stations.
Today we’re busy building rockets and spacecraft to take men to the moon. We have been fabulously successful with Project Mercury, and our Saturn I rockets have shown that they can reliably haul more than 10 tons of payload into orbit. Yet little is heard of manned space stations. Why is that so?
Actually the manned-space-station concept is just as exciting today as it was 15 years ago. There is absolutely no doubt that this country will have one or several such stations in orbit within a very few years. The reason a project for a space station hasn’t been pushed more aggressively is simply that we don’t know, yet, exactly how to build one best suited to the purposes it will serve.
Gemini to point way. As long as our manned-space-flight experience is limited to a total of about 53 hours logged by our astronauts, we cannot possibly specify the layout of a space station and all its many-faceted equipment in enough detail. Orbital flights by Gemini astronauts, in their two-man spacecraft, soon will help close this gap in our experience. And, if the Air Force receives a long-awaited go-ahead, so will its Manned Orbiting Laboratory, designed to study man’s ability to perform useful military tasks in space.
The Gemini astronauts, for the first time, will try orbital rendezvous and docking—a maneuver necessary to the operation of any space station. Inside and outside of their spacecraft, they will perform a whole slew of scientific observations and experiments. All this will give us a better idea of how much more can be accomplished by a manned space station than by an automatic observatory in space.
Using our space stations. Already we can foresee many tasks for which manned space stations can be immensely useful:
• Astronomical and astrophysical studies of sun, moon, planets, and the surrounding universe. Advantages of a space station would be freedom from atmospheric turbulence, and from the filtering effects of the earth’s atmosphere on ultraviolet and other radiation.
• Observations of the earth’s surface, for many purposes: weather forecasting, storm and flood warning, iceberg patrol, snowfall and water-resource management, prediction of volcanic eruptions and landslides, detection of forest fires, military reconnaissance, and navigational aid for ships and aircraft.
• Physical, medical, and life-sciences research. A space station is the ideal place for research on the effects of a number of conditions impossible to simulate on earth: prolonged weightlessness, space radiation of various types, a near-perfect vacuum of unlimited size.
• Maintenance of complex space installations. Consider a TV broadcasting satellite in a synchronous orbit—a station, seemingly standing still in the sky, to which anyone on earth below can tune his receiver. Several hundred kilowatts of transmitting power would be required. It may well prove to be economical to furnish a station so complex and powerful with a permanent maintenance crew, which would be exchanged at periodic intervals.
• A deep-space assembly site and jump-off platform for manned expeditions setting out to land on other planets. Such missions will require nuclear-powered spaceships, assembled and fueled in a low earth orbit from sections and propellants brought up by chemical earth-to-orbit freighters.
When we set out to design a space station, however, we face a strange paradox. To keep a man alive in outer space we have to put a barrier between him and space—a pressurized cabin or suit—but it must not deprive him of the very gains he sought in space. If he cannot effectively observe the earth beneath him or the universe about him, he’ll be like a man trying to study undersea life from a windowless submarine.
A related problem is raised by the question of possible ill effects from a long period of weightlessness.
Early space-station designs called for doughnut- or dumbbell-shaped stations rotating slowly about their hubs, so that centrifugal force would replace at least part of the missing gravity. But a spinning platform would handicap observers of the heavens and the earth, since telescopes re-quire a steady aim.
Must space stations spin? We still do not know whether artificial gravity will be necessary from the medical point of view— and, if so, whether a daily five-minute spin in a small centrifuge built into a non-rotating space station might not suffice to make both the astronaut and the doctor happy. But the coming Gemini orbital flights, of up to two weeks’ duration, will tell us a great deal about man’s ability to endure weightlessness for longer periods.
In any case, artificial gravity undoubtedly would add to the comfort of everyday life in a space station. So a rotating design looks attractive for a manned TV station in space, and for the crew quarters of an assembly station for expeditions to other planets. For such long tours of duty, comfortable living quarters for the crews will probably take precedence over suitability for scientific observations.
Space stations thus may differ in design according to their respective purposes. Likewise, their uses may dictate orbits of widely different types.
Unless the mission specifically calls for a high orbit, a low one offers the general advantage of lower earth-to-orbit transportation cost. A low west-east orbit, only slightly inclined to the equatorial plane, is particularly economical: It gives a rocket ship, at launching, full advantage of the “boost” resulting from the earth’s west-east rotation. Such an orbit would best suit a space station intended as an astronomical observatory— or as a physical and life-science laboratory. A relatively low polar orbit, in contrast, seems advantageous for earth surveillance, since it would enable an observer to see every point on earth at least twice in 24 hours.
For an assembly site for deep-space expeditions, a low orbit in the equatorial plane offers certain advantages. And a TV station “fixed” in space automatically calls for an equatorial orbit, with the added requirement of a 24-hour orbital period (which, in turn, sets the required orbital height at about 23,000 miles).
The answer: many stations. To sum up, manned space stations are bound to come. Because of their varied potential uses, and different requirements, it seems likely that we shall have not one but a number of space stations—and that, in due time, other countries will have theirs, too.
It may well be, however, that several mission assignments for future manned space stations can be combined and served by one central station, when all participants can agree on an identical orbit. To reconcile the missions’ different needs as to design, the orbiting space center may consist of a group of small free floating “mission” stations, clustered about a spinning doughnut or dumbbell that will serve as a combination hotel, restaurant, and office for the entire complex. | 0.817618 | 3.310153 |
|This artist's impression shows the magnetar in |
the very rich and young star cluster Westerlund 1.
This remarkable cluster contains hundreds of very
massive stars, some shining with a brilliance of almost
one million suns. European astronomers have for the
first time demonstrated that this magnetar -- an unusual
type of neutron star with an extremely strong magnetic
field -- was formed from a star with at least 40 times as
much mass as the Sun. The result presents great challenges
to current theories of how stars evolve, as a star as
massive as this was expected to become a black
hole, not a magnetar. (Credit: ESO/L. Calçada)
To reach their conclusions, the astronomers looked in detail at the extraordinary star cluster Westerlund 1, located 16 000 light-years away in the southern constellation of Ara (the Altar). From previous studies, the astronomers knew that Westerlund 1 was the closest super star cluster known, containing hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two thousand times the diameter of the Sun (as large as the orbit of Saturn).
"If the Sun were located at the heart of this remarkable cluster, our night sky would be full of hundreds of stars as bright as the full Moon," says Ben Ritchie, lead author of the paper reporting these results.
Westerlund 1 is a fantastic stellar zoo, with a diverse and exotic population of stars. The stars in the cluster share one thing: they all have the same age, estimated at between 3.5 and 5 million years, as the cluster was formed in a single star-formation event.
A magnetar is a type of neutron star with an incredibly strong magnetic field -- a million billion times stronger than that of the Earth, which is formed when certain stars undergo supernova explosions. The Westerlund 1 cluster hosts one of the few magnetars known in the Milky Way. Thanks to its home in the cluster, the astronomers were able to make the remarkable deduction that this magnetar must have formed from a star at least 40 times as massive as the Sun.
As all the stars in Westerlund 1 have the same age, the star that exploded and left a magnetar remnant must have had a shorter life than the surviving stars in the cluster. "Because the lifespan of a star is directly linked to its mass -- the heavier a star, the shorter its life -- if we can measure the mass of any one surviving star, we know for sure that the shorter-lived star that became the magnetar must have been even more massive," says co-author and team leader Simon Clark. "This is of great significance since there is no accepted theory for how such extremely magnetic objects are formed."
The astronomers therefore studied the stars that belong to the eclipsing double system W13 in Westerlund 1 using the fact that, in such a system, masses can be directly determined from the motions of the stars.
By comparison with these stars, they found that the star that became the magnetar must have been at least 40 times the mass of the Sun. This proves for the first time that magnetars can evolve from stars so massive we would normally expect them to form black holes. The previous assumption was that stars with initial masses between about 10 and 25 solar masses would form neutron stars and those above 25 solar masses would produce black holes.
"These stars must get rid of more than nine tenths of their mass before exploding as a supernova, or they would otherwise have created a black hole instead," says co-author Ignacio Negueruela. "Such huge mass losses before the explosion present great challenges to current theories of stellar evolution."
"This therefore raises the thorny question of just how massive a star has to be to collapse to form a black hole if stars over 40 times as heavy as our Sun cannot manage this feat," concludes co-author Norbert Langer.
The formation mechanism preferred by the astronomers postulates that the star that became the magnetar -- the progenitor -- was born with a stellar companion. As both stars evolved they would begin to interact, with energy derived from their orbital motion expended in ejecting the requisite huge quantities of mass from the progenitor star. While no such companion is currently visible at the site of the magnetar, this could be because the supernova that formed the magnetar caused the binary to break apart, ejecting both stars at high velocity from the cluster.
"If this is the case it suggests that binary systems may play a key role in stellar evolution by driving mass loss -- the ultimate cosmic 'diet plan' for heavyweight stars, which shifts over 95% of their initial mass," concludes Clark.
The open cluster Westerlund 1 was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970-74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100 000, and this is why it has taken so long to uncover the true nature of this particular cluster.
Westerlund 1 is a unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Milky Way live and die. From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100 000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way galaxy.
All stars so far analysed in Westerlund 1 have masses at least 30-40 times that of the Sun. Because such stars have a rather short life -- astronomically speaking -- Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a "newborn" cluster in our galaxy.
The research will soon appear in the research journal Astronomy and Astrophysics ("A VLT/FLAMES survey for massive binaries in Westerlund 1: II. Dynamical constraints on magnetar progenitor masses from the eclipsing binary W13," by B. Ritchie et al.). The same team published a first study of this object in 2006 ("A Neutron Star with a Massive Progenitor in Westerlund 1," by M.P. Muno et al., Astrophysical Journal, 636, L41).
The team is composed of Ben Ritchie and Simon Clark (The Open University, UK), Ignacio Negueruela (Universidad de Alicante, Spain), and Norbert Langer (Universität Bonn, Germany, and Universiteit Utrecht, the Netherlands).
The astronomers used the FLAMES instrument on ESO's Very Large Telescope at Paranal, Chile to study the stars in the Westerlund 1 cluster. | 0.916583 | 3.886527 |
If you live in or near or have access to a dark place at night, preferably when the moon is new or below the horizon, you may be able to see twin bands of stars surrounding a band of relative darkness. The band of darkness is the galactic plane, where most of our galaxy’s dust, debris and non-stellar gas is found, and the twin bands of light are stars that are slightly outside of the galactic plane. The estimated diameter of the Milky Way Galaxy is about 100,000 light-years. For scale comparison, if the galaxy and everything in it were scaled down to be one kilometer across, the solar system including the hypothetical Oort comet cloud, would be less than a centimeter across. The Milky Way Galaxy is made of two main arms, two minor arms and at least two smaller spurs. The two main arms are the Scutum-Centaurus and Perseus arms, the two minor arms are the Carina-Sagittarius and the Norma-Cygnus/Outer arms. The Solar System resides in a smaller spur between the Carina-Sagittarius and Perseus arms called the Orion spur. The entire Milky Way galaxy moves around a radio emitting object at the center of the galaxy called Sagittarius A* (the * is pronounced “star”), the current explanation for the object is that Sagittarius A* is a supermassive black hole containing more than 4 million solar masses.
Tag Archives: black hole
If Earth were to be replaced by an Earth-mass black hole, almost nothing in the universe would change. It wouldn’t start sucking things up, there would be no major gravitational disturbances, nothing. All that would happen is that anything that passed through a region the size of a peanut would be absorbed into the black hole, and anything that passed nearby would be distorted. All objects have an event horizon (the surface of a black hole), but most objects are far larger than their event horizon (a black hole with Earth’s mass is about the size of a peanut). Black holes also have something called a photon sphere, where photons (light waves/particles) orbit the black hole. Finally, if you were to try and fall into a black hole (for science of course) you would experience a process known as spaghettification. Since, as you approach the black hole, the parts of your body closest to the black hole are being pulled harder by gravity than those far away, you will be stretched, slowly are first but then more quickly, until all of your body is within the event horizon. What happens then? Nobody knows. The current mathematical models used in physics cannot describe what happens within the event horizon of the black hole. | 0.870112 | 3.776042 |
Nasa's Juno mission to Jupiter successfully launched on Friday on a five-year journey to the solar system's largest and oldest planet.
Hundreds of scientists and their families and friends watched from just a few miles away, cheering and yelling, "Go Juno!", as the spacecraft soared into a clear midday sky atop an unmanned rocket.
"It's fantastic!" said Dr Fran Bagenal, a planetary scientist at the University of Colorado at Boulder, who is part of the project. "Just great to see the thing lift off."
It was the first step in Juno's 1.7bn-mile (2.7bn km) voyage to the gas giant Jupiter, just two planets away but altogether different from Earth and next-door neighbour Mars.
Juno is solar powered, a first for a spacecraft meant to roam so far from the sun. It has three huge solar panels that were folded for launch. Once opened, they should each stretch as long and wide as a tractor-trailer. Previous spacecraft to the outer planets have relied on nuclear energy.
With Juno, scientists hope to answer some of the most fundamental questions on our solar system.
"How Jupiter formed. How it evolved. What really happened early in the solar system that eventually led to all of us," said Juno's chief investigator Scott Bolton, an astrophysicist at Southwest Research Institute in San Antonio.
Bolton said Jupiter is like a time capsule. It got most of the leftovers from the sun's creation nearly 5bn years ago, hence the planet's immense size. Its enormous gravity field has enabled it to hold on to that original material.
Jupiter is so big it could hold everything in the solar system, apart from the sun, and still be twice as massive. Astronomers say it probably was the first planet in the solar system to form.
Juno will venture much closer to Jupiter than any of the eight spacecraft that have visited the planet since the 1970s. Juno represents the next step, Bolton said.
"We look deeper. We go much closer. We're going over the poles. So we're doing a lot of new things that have never been done, and we're going to get all this brand-new information," Bolton said.
If all goes well, Juno will go into orbit around Jupiter's poles – a first – on 4 July 2016.
The oblong orbit will bring Juno within 3,100 miles of the cloudtops and right over the most powerful auroras in the solar system. In fact, that's how the spacecraft got its name – Juno peered through clouds to keep tabs on her husband, Jupiter.
Juno will circle the planet 33 times, each orbit lasting 11 days for a grand total of one year.
With each orbit, the spacecraft will pass over a different longitude so that by mission's end, "we've essentially dropped a net around the planet with all of our measurements," Bolton said. That's crucial for understanding Jupiter's invisible gravity and magnetic force fields, he noted.
The $1.1bn mission will end with Juno taking a fatal plunge into Jupiter in 2017.
Unlike many other Nasa missions, this one came in on budget and on time. It's relatively inexpensive: the Cassini probe, launched in 1997 to Saturn by way of Jupiter, cost $3.4bn. | 0.85297 | 3.519301 |
250 pages, 186 colour & b/w photos
The Milky Way galaxy is perhaps the grandest structure of which we are a part (along with the galaxy of neurons which is the human brain itself). Long perceived as the milky path across the night-sky and first revealed, in all its beauty and detail, in the wide-angle photographs of the American astronomer Edward Emerson Barnard in the late 19th and early twentieth century, we have now mapped it in detail and begun to explore its strange contents – from spiral arms in which new stars are being born from dust clouds to the Monster Black Hole that lies in its center.
More than almost anything else knowable to man, the view of the Milky Way stretching across the Cave of the Night as seen from a dark and pristine site suggests an image of eternity. Indeed, the Milky Way's vast system of 100,000 million stars is ancient – some 13 billion years old. But it is not a static and unchanging system; it is an evolving system. We have now begun to excavate – like archaeologists – the wreckage of star systems assimilated into it; we have learned that it is not a closed system – its gas is being replenished from the intergalactic medium – and this influx of gas sustains structures like the spiral arms that would otherwise be evanescent and revives the bursts of new star clusters. We realize that the familiar and mathematically idealized forms of the Hubble classification system – elliptical galaxies through barred and Grand Design spirals – though they provide a reasonable fit to the objects in the nearby universe do not describe well the violently disturbed exotica of the early universe. Drawing on the insights gleaned from a host of space telescopes probing galaxies across the electromagnetic spectrum and to the edge of the universe, the authors provide a map of our own star-system in space and unfold the stages of its development across time. The view is one of the Galaxy – and its place in the universe – as never before.
"With many great photographs – from Edwin Hubble to the Hubble Space Telescope – a robust approach to the science which is (usually) very well explained, and detailed footnotes, this is a history of galactic astronomy that should definitely find space on your bookshelf."
– Andy Sawers, Astronomy Now, September, 2015
"There are 186 illustrations, including many not often seen, and the production is of high quality. Sheehan & Conselice have produced a meticulously researched masterpiece on the talented individuals who first explored the extragalactic Universe."
– Simon Mitton, The Observatory, Vol. 135 (1247), August, 2015
"Galactic Encounters consists of three distinct parts, each with its own voice. [...] the material is written at a level accessible to enthusiasts looking for a narrative introduction. [...] If you enjoy reading stories about astronomers, or if you want an excellent introduction to galaxies and cosmology, then much of Galactic Encounters is perfect: fun to read and full of information."
– Louise Edwards, Physics Today, June, 2015
"Sheehan (astronomy historian/writer;psychiatrist) and Conselice (astronomer, Univ. of Nottingham, UK) do this in an informative and engaging style by choosing prominent scientists who made significant contributions and then giving biographical information about these individuals. In this way, the authors not only maintain the scientific standard of the writing at a high level but also convey a flavor of how research is undertaken. [...] Summing Up: Recommended. Lower-division undergraduates and general readers."
– D. E. Hogg, Choice, Vol. 52 (8), April, 2015
"Galactic Encounters [...] is a beautifully written and illustrated compilation of our progressive understanding of the cosmos since Galileo first pointed his telescope at the Milky Way and saw multitudes of stars. [...] Galactic Encounters is an informative and enjoyable read [...] ."
– Klaus Brasch, The Journal of the Royal Astronomical Society of Canada, Vol. 109 (1), February, 2015
"The book follows a roughly chronological timeline from the late eighteenth century to the present day. [...] The text is aimed at the general reader, though there are plenty of references to scholarly sources for those who want to explore further. [...] All in all, Galactic Encounters is an excellent work that will appeal to everyone interested in the deep sky, as well as to historians of astronomy."
– Lee Macdonald, Journal of the British Astronomical Association, Issue 3, 2015
"The book is written starting from the earliest observations and scientists and continues all the way to twenty first century. [...] The book is also suitable for general readers with maybe less background in physics or astronomy, as you don't need any mathematics to fly through the book and observations described within. [...] 'Galactic Encounters' is very interesting, thorough and well-illustrated."
– Kadri Tinn, AstroMadness.com, December, 2014
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William Sheehan is an American astronomical historian and writer, who has written the authoritative (and much-acclaimed) biography of Milky Way photographer and pioneering astronomer E. E. Barnard, The Immortal Fire Within. A regular scholar-in-residence at leading observatories including Yerkes, Lick, Lowell, and Mt. Wilson, he is currently working on a biography of stellar spectroscopist and galaxy morphologist W. W. Morgan, who discovered the spiral-arm structure of the Milky Way in 1951. As a professional psychiatrist as well as an astronomer, he has a unique insight into the personalities of the pioneering figures of the history of science. He has published a number of books on the history of Solar System studies, especially on the Moon and Mars, and is a consulting editor of Sky & Telescope, a 2001 fellow of the John Simon Guggenheim Memorial Foundation (for his research on the Milky Way), recipient of the Gold Medal of the Oriental Astronomical Association (the first Caucasian to receive that award), etc., etc. Asteroid no. 16037 is named in his honor (Sheehan).
Christopher Conselice, an astronomer at the University of Nottingham, is one of the world's leading experts on galaxy formation and evolution. He was educated at the University of Chicago and the University of Wisconson-Madison, and has held post-doctoral positions at the California Institute of Technology and the Space Telescope Science Institute. He was a regular contributor to Mercury, the magazine of the Astronomical Society of the Pacific. He has published his research in the leading professional journals of astronomy, including Science, Nature, and the Astrophysical Journal.
Julian Baum is one of the world's most highly regarded astronomical artists. His work was featured in Heather Couper and Nigel Henbest, The Guide to the Galaxy. He lives in Chester, England. | 0.906727 | 3.777236 |
A new NASA video has captured two cosmic wonders — a comet and a massive solar storm — with the Earth in the background as seen by a sun-watching spacecraft.
In the video, the Comet Pan-STARRS can be seen streaking through the inner solar system, orbiting the sun over the course of five days (March 10-15). As Pan-STARRS makes its ways into view, a coronal mass ejection (CME) — an explosion of plasma from the surface of the star — shoots towards Earth.
"The bright light on the left comes from the sun and the bursts from the left represent the solar material erupting off the sun in a CME," officials with NASA's Goddard Space Flight Center Scientific Visualization Studio wrote in a video description.
The dramatic video of Comet Pan-STARRS and the sun stormwas captured by one of NASA's twin Stereo spacecraft ( the name is short for Solar Terrestrial Relations Observatory) .. Launched in 2006, the two Stereo probes work together to provide a constant watch on the sun's solar weather events. One Stereo probe orbits just ahead of the Earth while the other trails behind. [How to see the comet]
"While it appears from Stereo's point of view that the CME passes right by the comet, the two are not lying in the same plane, which scientists know since the comet’s tail didn’t move or change in response to the CME's passage," NASA officials wrote.
Comet Pan-STARRS put on a brilliant show in the Southern Hemisphere before becoming visible to stargazers in the North during the first part of March. Astronomers using the Panoramic Survey Telescope and Rapid Response System (or Pan-STARRS) atop a volcano in Hawaii initially spotted the comet in June 2011.
Pan-STARRS is one of two comets expected to put on a show this year. Since reaching its maximum brightness earlier in March, Comet Pan-STARRS has been getting steadily dimmer, but it should be visible low on the western horizon, just after sunset, to stargazers with binoculars or small telescopes, NASA officials have said.
Comet ISON should make its first appearance in April, and some astronomers think it could be the brightest comet in a generation.
NASA's Stereo spacecraft are one of several missions that constantly monitor the sun for signs of solar flares and eruptions. The sun is currently in an active phase of its 11-year solar weather cycle. The current cycle is known as Solar Cycle 24 and is expected to reach its peak this year.
Editor's note: If you snap an amazing photo of Comet Pan-STARRS, or any other celestial object, and you'd like to share it for a possible story or image gallery, please send images and comments, including location information, to Managing Editor Tariq Malik at [email protected].
- Sun Fires CME Past Comet Pan-STARRS From Spacecraft's Viewpoint | Video
- Comet Pan-STARRS in Night Sky Explained (Infographic)
- Amazing Comet Photos of 2013 by Stargazers
- Sunset Comet Pan-STARRS Survives Brush With Sun | Video
Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.874848 | 3.556668 |
NASA / JPL-Caltech / UCLA
NASA's Wide-field Infrared Survey Explorer produced this infrared view of the entire sky.
How would the sky look through infrared eyes? The scientists behind NASA's Wide-field Infrared Survey Explorer mission have served up that kind of view with an all-sky map of infrared wavelengths, centered on the glowing Milky Way.
The map was unveiled this week to mark the completion of WISE's infrared sky atlas, more than two years after the $320 million mission was launched. The telescope collected more than 2.7 million images in four infrared wavelengths and sent down more than 15 trillion bytes of data. The WISE spacecraft was shut down a year ago, after surveying the entire sky one and a half times, but scientists needed still more time to analyze and organize the data.
The images were combined into an atlas of more than 18,000 images. The atlas is accompanied by a catalog listing the infrared properties of more than 560 million individual objects, ranging from near-Earth asteroids to far-flung galaxies. Wednesday's release of the catalog meets the fundamental objective of a mission that was conceived in 1998.
"Today, WISE delivers the fruit of 14 years of effort to the astronomical community," UCLA astronomer Edward Wright, the mission's principal investigator, said in a NASA news release.
NASA / JPL-Caltech / UCLA
This annotated version of the all-sky infrared map points out some of the main attractions. In addition, Saturn, Mars and Jupiter can be seen as stretched-out red spots far off the galactic plane, at roughly the 1 o'clock, 2 o'clock and 7 o'clock, respectively.
Over the past two years, WISE's science team has discovered the first examples of an ultra-cool class of stars known as Y-dwarfs, found the first Trojan asteroid to share Earth's orbit, and came up with a downsized estimate of the number of asteroids with a chance of threatening our planet. But the WISE team isn't done yet: Scientists will spend years poring over the data contained in the newly released catalog. And you can try your hand as well, although for most people, this gallery of WISE highlights should suffice.
WISE's all-sky image served as this week's "Where in the Cosmos" picture quiz on the Cosmic Log Facebook page, and it didn't take more than a few minutes for Eloid Ruiz to report what the picture showed. Eloid will be receiving a pair of 3-D glasses with my compliments (and an assist from Microsoft Research's World Wide Telescope project). Stay tuned next week for the next "Where in the Cosmos" puzzler — and while you're waiting, tune in the Weekly Space Hangout, a week-in-review webcast hosted by Universe Today's Fraser Cain.
In the March 15 episode of the Weekly Space Hangout, we talk about SpaceX, deflecting asteroids with nukes, and sighting Russian artifacts on the moon.
More wonders from WISE:
- Space bubbles offer peek at sun's evolution
- Pacman Nebula bares its teeth
- A gathering of glorious galaxies
- Star goes through shocking transformation
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds. | 0.947467 | 3.542 |
Enormous asteroid Vesta is the second-largest body in the asteroid belt. It’s so big, in fact, that many consider it to be more of a planet than just another rocky lump. There are good reasons to consider it planet-like: But for two massive impacts that nearly blew the thing apart (we’ll come back to that later), Vesta would be roughly spherical; and among other things, its innards are differentiated – it has a core, mantle, and crust. Just like Earth and Mars and Venus.
If Jupiter hadn’t formed, and its massive gravity hadn’t stirred the asteroid belt into perpetual crumbliness, it’s possible Vesta may have grown up and become a real planet of its own. But Jupiter did come along, and Vesta froze in a sort of embryonic planet-seed stage. It’s a relic from the beginning of the solar system, and a valuable target for scientists seeking to learn more about how our planetary neighborhood took shape.
Until recently, though, we didn’t know very much about Vesta except that it was big, appeared to be missing a chunk from its south pole, and had donated bits and pieces of itself to the good planet Earth (something like one-sixth of the meteorites that have fallen on Earth are fragments of Vesta).
It wasn’t until 2011 that the full image of the protoplanet began to emerge (even the best Hubble images were blurry collections of pixels). That was when NASA’s intrepid Dawn spacecraft, tasked with exploring two of the asteroid belt’s worlds, zoomed in for a close look. Dawn spent more than a year orbiting the 525-kilometer wide protoplanet. It mapped Vesta’s surface, measured its gravity field, and took detailed images before heading for its next target.
Almost as soon as the spacecraft arrived at Vesta, it relayed images to Earth that puzzled scientists. Running along Vesta’s equator were humongous troughs comparable in size to the Grand Canyon. It looked as if something had grabbed the rock, put one hand on the north pole and the other on the south, and pressed the protoplanet between its palms. Later, the Dawn team would learn that a massive impact had reverberated so mightily through Vesta that it was indeed deformed, and now wears the scars along its equator.
That impact, which occurred more than a billion years ago, was the second of two cataclysmic collisions at Vesta’s south pole. The first, about two billion years ago, created the Veneneia basin, which measures about 400 kilometers across. The second obliterated that bruised crater, carving the 500-kilometer wide Rheasilvia impact basin into the first.
When the dust from the collisions had settled, Vesta’s smashed up south pole had grown an enormous mountain. Stretching 180 kilometers across, and rising 25 kilometers from the base of the crater, the Vestal peak is truly huge.
How Vesta survived such violence isn’t clear. But the scars of the impacts are all over it – including those equatorial fractures – and here on Earth, in the form of fragments that have fallen as meteorites.
Smaller, less intrusive impacts created pockmarks on much of Vesta’s surface, which is remarkably varied in shade and texture. Coal-dark spots parked next to bright white areas have intrigued scientists, who wondered how the asteroid came to be painted with such variegated shades. And how did that mysterious, dark material end up on lighter-colored Vesta anyway?
Turns out, it was left there by other asteroids – dark asteroids known as carbonaceous chondrites. Scientists solved this riddle recently by characterizing the minerals present in Vesta’s dark splotches (part of this work involves generating images like the one above, where the colors correspond to different chemical compositions). In those dark splotches, they detected the mineral serpentine, which only forms under specific conditions. Things like volcanic eruptions and the heating, melting, and recongealing of Vesta as it formed would have destroyed serpentine – but an asteroid impact would not. Furthermore, the team suspects that most of Vesta’s dark marks originated from the asteroid that created the Veneneia crater (this work confirms an earlier hypothesis implicating asteroids).
There are other perplexing features on Vesta’s surface, including small gullies that may have been carved by water.
While scientists work on solving these remaining mysteries, Dawn is busy speeding toward its next target, Ceres. The largest of all the worlds in the asteroid belt, Ceres is a bona fide dwarf planet, an icy chunk that’s very different from dry, dusty Vesta. When Dawn arrives in spring 2015, it will be the first spacecraft sent to orbit two distinct bodies in the solar system – and the first to peer at Ceres.
“After more than two centuries of telescopic study, the largest body between the Sun and Pluto not yet visited by a spacecraft is about to be unveiled,” says Dawn chief engineer and mission director Marc Rayman of the Jet Propulsion Laboratory.
Dawn will map Ceres’ surface and search for clues about how this icy world formed, before ending its mission in 2016.
The spacecraft’s final act won’t be a dramatic plunge to the surface of its target planet, as some of Earth’s other spacecraft have done. Ceres is potentially a wet, mineral-rich world – one that could, in theory, support life. Contaminating Ceres with anything from Earth would be exceptionally irresponsible.
So, when Dawn’s fuel runs out and its messages to Earth cease, it will forever stay in orbit around Ceres.
“The spacecraft will remain a silent celestial monument to human curiosity, creativity, ingenuity, and passion for adventure and knowledge,“ Rayman says. “It will stay in orbit around Ceres as surely as the moon stays in orbit around Earth or Earth stays in orbit around the sun.” | 0.864284 | 3.841264 |
'Extreme Universe' puzzle deepens
The mystery surrounding the source of the highest-energy particles known in the Universe has grown deeper.
The particles, known as cosmic rays, can show up with energies a million times higher than the biggest particle accelerators on Earth can produce.
Astrophysicists believed that only two sources could make them: supermassive black holes in active galaxies, or so-called gamma ray bursts.
A study in Nature has now all but ruled out gamma ray bursts as the cause.
Gamma ray bursts (GRBs) are the brightest events we know of, though their sources remain a matter of some debate. They can release in hours more energy than our Sun will ever produce.
Computer models predict that GRBs could be the source of cosmic rays - mostly subatomic particles called protons, accelerated to incredibly high speeds.
But they were also predicted to produce a stream of neutrinos, the slippery subatomic particles in claims of faster-than-light travel.
So researchers at the IceCube neutrino telescope went looking for evidence of neutrino arrival that coincided with measurements of gamma ray bursts detected by the Fermi and Swift space telescopes.
But it found none - suggesting that active galactic nuclei, where supermassive black holes reside, are likely to be the source.
Given that neutrinos have such a low probability of interacting with matter as we know it, IceCube is a neutrino detector of immense proportions.
Situated at the South Pole, it consists of more than 5,000 optical sensors buried across a cubic kilometre of glacial ice, each looking for the brief blue flash of light produced when a neutrino happens to bump into atomic nuclei in the ice.
Over the course of measurements taken between mid-2008 and mid-2010, some 300 GRBs were recorded - but IceCube scientists detected none of the eight or so neutrinos that they predicted would be associated with those events.
The models that lead to such predictions are making guesses about the most violent, highest-energy processes of which physics can conceive.
Because those models include a few educated guesses, GRBs are not completely out of the running as the source of the highest energy cosmic rays we see; perhaps neutrinos are not produced in the numbers that physicists expect.
Nevertheless, Julie McEnery, a project scientist on the Fermi space telescope who was not involved with the research, said it was a "huge breakthrough for IceCube to make an astrophysically meaningful measurement".
"This is the question," she told BBC News. "The origin of cosmic rays is in general one of the longest-standing questions in astrophysics, and the ultra-high-energy rays are particularly interesting.
"They're just completely cool however you think about them, but they're also pointing to something extraordinary that can happen in some astrophysical sources - and it's key to understanding not only where but how they are produced." | 0.874054 | 4.146072 |
Astronomers have discovered a cosmic one-two punch unlike any ever seen before. Two of the most powerful phenomena in the universe, a supermassive black hole, and the collision of giant galaxy clusters, have combined to create a stupendous cosmic particle accelerator.
By combining data from NASA’s Chandra X-ray Observatory, the Giant Metrewave Radio Telescope (GMRT) in India, the NSF’s Karl G. Jansky Very Large Array, and other telescopes, researchers have found out what happens when matter ejected by a giant black hole is swept up in the merger of two enormous galaxy clusters.
“We have seen each of these spectacular phenomena separately in many places,” says Reinout van Weeren of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts. “This is the first time, however, that we seen them clearly linked together in the same system.”
This cosmic double whammy is found in a pair of colliding galaxy clusters called Abell 3411 and Abell 3412 located about two billion light years from Earth. The two clusters are both very massive, each weighing about a quadrillion — or a million billion — times the mass of the Sun.
The comet-shaped appearance of the X-rays detected by Chandra is produced by hot gas from one cluster plowing through the hot gas of the other cluster. Optical data from the Keck Observatory and Japan’s Subaru telescope, both on Mauna Kea, Hawaii, detected the galaxies in each cluster.
First, at least one spinning, supermassive black hole in one of the galaxy clusters produced a rotating, tightly-wound magnetic funnel. The powerful electromagnetic fields associated with this structure have accelerated some of the inflowing gas away from the vicinity of the black hole in the form of an energetic, high-speed jet.
Then, these accelerated particles in the jet were accelerated again when they encountered colossal shock waves — cosmic versions of sonic booms generated by supersonic aircraft — produced by the collision of the massive gas clouds associated with the galaxy clusters.
“It’s almost like launching a rocket into low-Earth orbit and then getting shot out of the Solar System by a second rocket blast,” says Felipe Andrade-Santos, also of the CfA. “These particles are among the most energetic particles observed in the universe, thanks to the double injection of energy.”
This discovery solves a long-standing mystery in galaxy cluster research about the origin of beautiful swirls of radio emission stretching for millions of light years, detected in Abell 3411 and Abell 3412 with the GMRT.
The team determined that as the shock waves travel across the cluster for hundreds of millions of years, the doubly accelerated particles produce giant swirls of radio emission.
“This result shows that a remarkable combination of powerful events generate these particle acceleration factories, which are the largest and most powerful in the universe,” says William Dawson of Lawrence Livermore National Lab in Livermore, California. “It is a bit poetic that it took a combination of the world’s biggest observatories to understand this.” | 0.908414 | 4.119474 |
September 12, 2012
Strange Exoplanet Environments May Be Suitable For Extreme Lifeforms
April Flowers for redOrbit.com - Your Universe Online
In the hunt for the elusive "blue dot" exoplanet — a planet with roughly the same characteristics as Earth — astronomers have discovered a veritable rogue's gallery of oddballs. From scorching hot worlds with molten surfaces to frigid ice balls, the planets outside our solar system are vastly different.New research, published in the Astrobiology journal, reveals that life might actually be able to survive on some of the many strange exoplanetary bodies.
"When we're talking about a habitable planet, we're talking about a world where liquid water can exist," said Stephen Kane, a scientist with the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena. "A planet needs to be the right distance from its star -- not too hot and not too cold." Determined by the size and heat of the star, this temperature range is commonly referred to as the "habitable zone" around a star.
Kane and colleague, Dawn Gelino, have created a resource called the "Habitable Zone Gallery," which calculates the size and distance of the habitable zone for each exoplanetary system that has been discovered. It also shows which exoplanets orbit in this "goldilocks" zone.
But not all exoplanets have Earth-like orbits that remain at a fairly constant distance from their stars. One of the unexpected revelations of planet hunting has been that many planets travel in very oblong, eccentric orbits that vary greatly in distance from their stars.
"Planets like these may spend some, but not all of their time in the habitable zone," Kane said. "You might have a world that heats up for brief periods in between long, cold winters, or you might have brief spikes of very hot conditions."
Though planets like these would be very different from Earth, this might not preclude them from being able to support alien life. "Scientists have found microscopic life forms on Earth that can survive all kinds of extreme conditions," Kane said. "Some organisms can basically drop their metabolism to zero to survive very long-lasting, cold conditions. We know that others can withstand very extreme heat conditions if they have a protective layer of rock or water. There have even been studies performed on Earth-based spores, bacteria and lichens, which show they can survive in both harsh environments on Earth and the extreme conditions of space."
The team's research suggests that the habitable zone around stars might be larger than previously thought, and that planets that might be hostile to human life could be perfect for extremophiles, like lichens and bacteria.
"Life evolved on Earth at a very early stage in the planet's development, under conditions much harsher than they are today," Kane said.
Many life-harboring worlds might not be planets at all, but rather moons of larger, gas-giant planets like Jupiter in our own solar system.
"There are lots of giant planets out there, and all of them may have moons, if they are like the giant planets in the solar system," Kane says. "A moon of a planet that is in or spends time in a habitable zone can be habitable itself."
Titan, for example, is the largest moon of Saturn, which despite its thick atmosphere, is far too distant from the Sun and too cold for life as we know it to exist on its surface. If you move Titan closer to the sun, however, it would have lots of water vapor and be very favorable for life.
Kane is quick to point out that there are limits to what scientists can presently determine about habitability on already-discovered exoplanets. "It's difficult to really know about a planet when you don't have any knowledge about its atmosphere," he said.
For example, both Earth and Venus experience an atmospheric "greenhouse effect" -- but the runaway effect on Venus makes it the hottest place in the solar system. "Without analogues in our own solar system, it's difficult to know precisely what a habitable moon or eccentric planet orbit would look like."
Still, the research suggests that habitability might exist in many forms in the galaxy -- not just on planets that look like our own. Kane and Gelino are hard at work determining which already-discovered exoplanets might be candidates for extremophile life or habitable moons.
"There are lots of eccentric and gas giant planet discoveries," Kane says. "We may find some surprises out there as we start to determine exactly what we consider habitable." | 0.872071 | 3.603895 |
This journal entry is dedicated to planetary atmospheres, since this is probably the most difficult part of a worldbuilder’s journey. Of course, you can have things easier way, say, if you have earthlike conditions or you have additional data laid out for you in case of a standard star. But what if things were different?
I’m going to explain each step, adding some theoretical info as well. The Four Elements series will cover topics such as the atmosphere, the ocean, geological activity, insolation and planetary climate. And maybe something else I’ll find necessary to add.
The quest doesn’t start where one might think it does – not on a planet, but on a star. So, long before we can model our planetary atmosphere or anything else related to it, first we should consider stellar spectrum. There are several ways of getting it: taking a real detailed spectrum for existing star or computing a synthetic stellar spectrum. It all depends on your star of choice and how deep you are willing to go into details.
Why is this important? To design your own exclusive and unique planetary atmosphere model: maybe the air is so thin at altitude of 5 km, so your local people will never go to the mountains, for example. Whatever it is, you’ll get the full set of necessary parameters, some of which you might have had imagined, and some of which you probably didn’t expect at all. Anyway, you will get to know your planet better.
Don’t be afraid of experimenting with things. They are not as hard or incomprehensible as might appear to be.
The atmosphere is an envelope of gas mixture around the planet. It is held down by gravity, and the weight of that gas is pressure (as in mass times g). The total pressure is the sum of partial pressures of gasses in the mixture. The partial pressure is the contribution of a particular gas constituent to the total pressure, and is found as the total pressure times the volume fraction of gas component.
The proportion of gases found in the atmosphere changes with altitude. Distinct layers (such as troposphere, stratosphere, etc.) are identified using thermal characteristics, chemical composition, molecule movement, and density.
Individual molecules are moving freely in gas and if their motion velocity exceeds the planet’s escape velocity, the molecules will escape into space from the outer edge of the atmosphere. A certain amount will always exceed escape velocity, and if that percentage is too high, the atmosphere will leak away in a geologically short term. Thus, enough gravity is necessary to hold the atmosphere. The outer atmosphere temperature plays a vital role in this process as well, since gas molecules travel faster with increasing temperature. The hotter the exosphere is, the greater gravity must be. To keep things in balance, worlds closer to their stars must be larger to hold atmospheres equivalent to those around cooler worlds. Thus, atmospheric composition is also important, because lighter molecules move faster at the same temperature. Same surface gravity can keep one molecules, but can’t hold others; in case of Earth hydrogen and helium are too light for our gravity.
Composition and pressure are not completely free parameters, though. They are influenced and modified by chemical reactions with the surface of the planet (e.g. atmosphere interaction with crustal rocks over time in the carbonate-silicate cycle), living things and photodissociation (stellar UV light breaks up the hydrogen-bearing compounds like water, ammonia and methane) at the outer edge of the atmosphere. The atmosphere changes over geological time along with the evolution of the star, life and loss of lighter gasses.
Terrestrial-like planets may obtain atmospheres from three primary sources: capture of nebular gases, degassing during accretion, and degassing from subsequent tectonic activity. While capture of gases is vital for gas giants, low-mass terrestrial planets are unable to capture and retain nebula gases, which also may have largely dissipated from the inner solar system by the time of final planetary accretion. Atmospheric mass and composition for terrestrial planets is therefore closely related to the composition of the solid planet (Elkins-Tanton & Seager, 2008a).
In case of humans and animals the atmosphere has limits on its composition. To be breathable, it must have levels of molecular oxygen (O2) between 0.16 and 0.5 atm; higher concentrations of oxygen are toxic (severe cases can result in cell damage and death), lower than minimum are not enough to support human life. Hypoxia (oxygen deprivation) and sudden unconsciousness becomes a problem with an oxygen partial pressure of less than 0.16 atm. Hyperoxia (excess oxygen in body tissues), involving convulsions, becomes a problem when oxygen partial pressure is too high. Our present atmosphere contains 21% molecular oxygen (partial pressure of 0.21 atm).
Also, to prevent nitrogen narcosis under high pressures (the diver’s “rapture of the deep”) the partial pressure of nitrogen (N2) must be less than 3 atm.
As for other toxic stuff, the level of carbon dioxide must be less than 0.02 atm to breathe indefinitely, and less than 0.005 atm to avoid physiological stresses. In case of CO2 concentration above normal levels the only habitable places for humans might be high regions, like mountains. But then again, too little oxygen higher up can be troublesome.
Many plants, however, can survive and thrive in low oxygen-high CO2 environment. Earth’s plants will grow in many atmospheres that are unbreathable to humans and animals, unless the runaway greenhouse ruins the place completely (like Venus).
By building planet atmosphere and climate models you can see what are the boundaries for life under different stars and atmospheres. How fast the atmosphere thins upward? What are the properties of layers (altitudes, temperatures, pressures, composition, ozone layer (ozone is also toxic), gravitational pull, etc.)? What is the climate and weather pattern? The broader applications for the model include your planet aerospace or colonization/terraforming history, if applicable. The thickness of the atmosphere has some consequences. The thicker it is (and/or the lower the gravity), the easier flight is. Sound also travels better in a denser medium. Storms can be more intense if mass of moving air is greater.
More detailed description of atmospheres is beyond the scope of this article, but can be found on the Internet or in textbooks. In fact, if you know little about how atmospheres work, further reading into subject is required before building anything. Some useful book titles are listed in my LibraryThing catalogue, which is constantly growing. My goal here is to describe the tools: what data for models is required and how those models can be used to produce desirable results.
Climate dynamics model
The MITgcm (MIT General Circulation Model) is a numerical model designed for study of the atmosphere, ocean, and climate dynamics. MITgcm is freely available to all and can be run on a home pc or laptop, and is enough to play with your planet in detail.
Running the NASA/GISS model requires a significant investment in time and money, and it is designed to run on multiprocessor machines. It can reproduce the seasonal and regional mean values and variations of climate quantities such as temperature, pressure, precipitation, cloud cover, and radiation with reasonable degrees of precision, and many other things. I do not recommend this one for our purpose (though, if you own a multiprocessor workstation, you can try).
The CESM is also designed for simulating Earth’s climate system, but, as with the NASA/GISS, it is not simple at all. It is a coupled climate model composed of five separate models simultaneously simulating atmosphere, ocean, land, land-ice, and sea-ice.
However, before you can model weather and climate, an atmospheric layered model is required. You can take earthlike model (e.g. Standard Atmosphere) or you can make your own. For the latter purpose you’ll need another piece of code, described in the section below.
Photochemical and radiative/convective atmosphere models
The coupled photochemical and radiative/convective atmosphere model was used to study earthlike planets around different types of stars: F2V, G2V (Sun), K2V (Segura et al., Astrobiology, 2003) and M stars (Segura et al., Astrobiology, 2005); Grenfell et al. 2006, 2011; Kasting et al. 1996.
This model requires stellar spectrum, which can be taken from the database or synthesized. Some spectra are hard to find. The ones used by Segura et al. can be taken from the VPL site.
Stellar flux greatly influences chemical processes in the atmosphere and biological processes on the planet. Each star has its individual flux “signature”.
In Segura’s model the “Earth” is assumed to be at a distance equivalent to 1 AU in the extrasolar planet system. The orbital radius is scaled according to stellar luminosity, and the planet is then moved inward or outward until its calculated surface temperature is 288 K. Also, the term “mixing ratio” has the same meaning as “mole fraction”.
The planet around the F star develops a thicker ozone layer because of the abundance of short-wavelength UV radiation (lambda < 200 nm) that can dissociate molecular oxygen.
The surface UV flux increases with decreasing partial pressure of O2, but the behavior is very nonlinear. Good UV shield develops above 10^-2 of present atmospheric level of O2.
M stars emit very little near-UV radiation (200-300 nm), but active M (and, in fact, early K) stars emit lots of UV radiation shortward of 200 nm (chromospheric emission). One can therefore split molecular oxygen (and, hence, make ozone), but the ozone photochemistry is very different. Methane in Earth’s atmosphere is mostly destroyed in chemical reactions triggered by UV-flux at 310 nm. In atmospheres near M stars the lifetime for methane is long.
Synthetic stellar spectrum
If you have a star type that is not on the VPL list of spectra, acquiring a synthetic spectrum is where you’ll have to start building your model. There are numerous ways and software packages to compute a synthetic spectrum, but the easiest one is to use the BaSeL interactive server: it saves time and sanity. This tool presents a user-friendly interface of an interpolation engine, that allows on-line computations of synthetic stellar spectra for any given set of fundamental parameters Teff, log g and [Fe/H]. More info about BaSeL is found in “The BaSeL interactive web server: a tool for stellar physics”. Please note that fundamental parameters are taken from the real star’s data or computed stellar evolution model.
# Have fun and more modeling to follow. | 0.811236 | 3.777722 |
Caption: An artist’s rendering of galaxy BX442 and its companion dwarf galaxy (upper left). Credit: Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron
Ancient starlight traveling for 10.7 billion years has brought a surprise – evidence of a spiral galaxy long before other spiral galaxies are known to have formed.
“As you go back in time to the early universe, galaxies look really strange, clumpy and irregular, not symmetric,” said Alice Shapley, a UCLA associate professor of physics and astronomy, and co-author of a study reported in today’s journal Nature. “The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?”
Galaxies today come in a variety of unique shapes and sizes. Some, like our Milky Way Galaxy, are rotating disks of stars and gas called spiral galaxies. Other galaxies, called elliptical galaxies, resemble giant orbs of older reddish stars moving in random directions. Then there are a host of smaller irregular shaped galaxies bound together by gravity but lacking in any visible structure. A great, diverse population of these types of irregular galaxies dominated the early Universe, says Shapely.
Light from this incredibly distant spiral galaxy, traveling at nearly six trillion miles per year, took 10.7 billion years to reach Earth; just 3 billion years after the Universe was created in an event called the Big Bang.
According to a press release from UCLA, astronomers used the sharp eyes of the Hubble Space Telescope to spy on 300 very distant galaxies in the early Universe. The scientists originally thought their galaxy, one of the most massive in their survey going by the unglamorous name of BX442, was an illusion, perhaps two galaxies superimposed on each other.
“The fact that this galaxy exists is astounding,” said David Law, lead author of the study and Dunlap Institute postdoctoral fellow at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics. “Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe.” A ‘grand design’ galaxy has prominent, well-formed spiral arms.
To understand their image further, astronomers used a unique, state-of-the-art instrument called the OSIRIS spectrograph at the W.M. Keck Observatory atop Hawaii’s dormant Mauna Kea volcano. The instrument, built by UCLA professor James Larkin, allowed them to study light from about 3,600 locations in and around BX442. This spectra gave them the clues they needed to show they were indeed looking at a single, rotating spiral galaxy.
While spiral galaxies are abundant throughout the current cosmos, that wasn’t always the case. Spiral galaxies in the early Universe were rare because of frequent interactions. “BX442 looks like a nearby galaxy, but in the early universe, galaxies were colliding together much more frequently,” says Shapely. “Gas was raining in from the intergalactic medium and feeding stars that were being formed at a much more rapid rate than they are today; black holes grew at a much more rapid rate as well. The universe today is boring compared to this early time.”
Shapely and Law think the gravitational tug-of-war between a dwarf galaxy companion and BX442 may be responsible for its futuristic look. The companion appears as just a small blob in their image. Computer simulations conducted by Charlotte Christensen, a postdoctoral student at the University of Arizona and co-author of the paper, lends evidence to this idea. Eventually, BX442 and the smaller galaxy likely will merge.
Shapley said BX442 represents a link between early galaxies that are much more turbulent and the rotating spiral galaxies that we see around us. “Indeed, this galaxy may highlight the importance of merger interactions at any cosmic epoch in creating grand design spiral structure,” she said.
Studying BX442 is likely to help astronomers understand how spiral galaxies like the Milky Way form, she added.
Caption 2: HST/Keck false color composite image of galaxy BX442. Credit: David Law/Dunlap Institute for Astronomy & Astrophysics | 0.828883 | 4.015303 |
Astronomers earlier this month (April 6, 2012) announced evidence for a record-breaking nine planets around the nearby sun-like star HD 10180. Results from 2010 had shown that the star has at least five planets, and possibly as many as seven. The new results – proposing a nine-planet model for this solar system – would make HD 10180 the first star to surpass the number of planets in our own solar system and suggest that our sun is not alone in hosting a large family of diverse worlds.
The planets encompass a wide range of sizes and environments. The smallest planet is only 30% more massive than Earth making it most likely a rocky world like our own. It is also the closest planet to its star, orbiting once every 29 hours. Such a close orbit means its surface is blasted by intense stellar radiation thus making it completely inhospitable to any life we would recognize. The most distant planet has about two-thirds the mass of Saturn. Completing one trip around the star every six years, its orbit would fit entirely within our own system’s asteroid belt – the rocky debris field between Mars and Jupiter. One planet orbits well within HD 10180’s “habitable zone”. In other words, it is just the right distance from the star for liquid water to exist on it surface. Unfortunately, its Neptune-like mass means the planet is probably a gas giant and therefore lacks the solid surface needed for rivers, lakes, and oceans to form.
Two years ago, the star gained noteriety when astronomers announced the discovery of six planets all roughly the mass of Neptune with hints of a seventh. These new results, described in a paper accepted to the journal Astronomy and Astrophysics on April 6, 2012, have subjected that data to a more rigorous statistical analysis which not only confirms and refines the properties of the six known planets, but also reveals the subtle signatures of three more planets all just a few times the mass of Earth.
The planets were discovered by looking for wobbles in the star’s motion caused by gentle tugging from the orbiting worlds. The star’s wobble is too small to allow astronomers to directly observe the star’s motion on the sky. Researchers instead rely on the Doppler effect: the compressing and stretching of light waves caused by the star moving towards and away from our telescopes. This is the same principle that causes a train horn to apparently change pitch as it races past you. By observing a star whose light waves get repeatedly stretched and compressed, astronomers can infer not only the motion of the star, but also the mass of the object pulling on it. This technique has led to the discovery of over 90% of the 763 known planets around other stars.
The planets were discovered using the High Accuracy Radial Velocity Planet Searcher (HARPS) on the European Southern Observatory’s (ESO) 3.6-meter La Silla telescope. Sitting 2400 meters (7800 feet) above sea level in the southern part of Chile’s Atacama Desert, HARPS works much like a prism, allowing astronomers to split star light into its component wavelengths. The incredible precision of this remarkable instrument has uncovered a wealth of diverse planets since it started operations in 2003.
HD 10180 is star pretty similar to our sun. It’s slightly larger and brighter, though human visitors would probably find comfort in its familiar yellow glow. Astronomers estimate that HD 10180 is pretty old: born approximately 7 billion years ago, it has been around for about half the age of the universe. Too faint to be seen without the aid of a telescope, the star sits about 127 light-years away in the southern constellation of Hydrus, the water snake. This means the light that we currently see started its journey to Earth roughly the same time the Statue of Liberty arrived in New York City and Mark Twain published “The Adventures of Huckleberry Finn”.
Bottom line: Astronomers now believe that nine planets move in orbit around the sun-like star HD 10180. This star now holds the record for the largest number of planets, surpassing our own sun. This discovery supports the hypothesis that large, diverse planetary systems are common in the universe.
Christopher has a Ph.D. in astronomy from the University of California, Los Angeles. After eight years of searching for exoplanets, probing distant galaxies and exploring comets, Chris realized he enjoyed talking about astronomy a lot more than actually doing it. After being awarded a 2013 AAAS Mass Media Fellowship to write for Scientific American, he left a research career at the U.S. Naval Observatory to pursue a new life writing about anything and everything within the local cosmological horizon. Since 2014, he's been working with Science News. | 0.930002 | 3.914135 |
On a clear Christmas morning atop Mount Wilson, before the first tentacles of dawn struck the Los Angeles sprawl 5,700 feet below, George Willis Ritchey was capturing the most spectacular view of the “Great Nebula of Orion” anyone had ever seen. For close to four hours, he had been standing at the base of an enormous, steel-framed telescope, making minute adjustments as the machine tracked the nebula across the night sky.
The year was 1908, and the 60-inch reflector, which Ritchey had engineered and newly built, was the largest and most powerful in the world. As its huge curved mirror collected the nebular light, the incoming photons slowly exposed the emulsion on a photographic glass plate roughly the size of an iPad. Later, an assistant would develop the negative and label it “Ri-0”—the inaugural scientific image from Ritchey’s state-of-the-art scope.
Today, Ri-0 is one of more than 200,000 astronomical plates archived at the main offices of the Carnegie Observatories, in Pasadena, California. Made between 1892 and the early 1990s using telescopes at Mount Wilson, Palomar (near San Diego), Las Campanas (in Chile), and Kenwood (in Chicago) observatories, the plates range in size from centimeter-square slivers to pieces as large as a desktop computer screen.1
This collection, the second largest in the United States, includes some of the most important observations in astronomy in the last century. It’s these images, for instance, that sparked Edwin Hubble’s realization of the expanding universe, that led George Ellery Hale to discover the sun’s magnetic field, and that provided the empirical basis for theories of how stars and galaxies form.
Here is a sampling of the most famous, and most striking, shots.
The sun’s magnetic field
In early 1908, the solar astronomer and telescope engineer George Ellery Hale began tinkering with specialized photographic plates that were sensitive to red (long) wavelengths of light. He was particularly interested in observing the sun in the red wavelength known as H-alpha, an important signature of a star’s atmosphere. It took him a month to perfect the technique. The plate above was his first clear image, which revealed strange swirls surrounding sunspots, which Hale called flocculi. Although he (wrongly) hypothesized that the flocculi were gas tornadoes full of whirling electrons, the discovery led him to (rightly) conclude that the sun generated a magnetic field.
Hale went hunting for direct evidence of the sun’s magnetic field using a spectrograph, which separates light into a frequency spectrum, as represented by a series of vertical lines. To spread out these lines so that he could see them in detail, Hale placed an enormous, 30-foot spectrograph in a concrete well beneath the brand new 60-foot solar telescope at Mount Wilson. He captured the projected spectra on a 17-inch-long glass plate, like the one depicted above by an unknown photographer, possibly Hale. When he compared the spectral lines from the surface of the sun with lines from its sunspots, he saw that the sunspots split some of the lines into multiples while also polarizing the light. (In the above plate, the split spectral lines are labeled K and H.) This splitting, known as the Zeeman effect, provided the first confirmation of a magnetic field beyond Earth.
Hubble’s famous “VAR!” revelation
One night in the fall of 1923, Edwin Hubble took a 45-minute exposure of what was then called the Andromeda nebula. At the time, astronomers were debating whether the spiral smudges, or “nebula,” they were seeing in their telescopes were small star clusters within our own galaxy, the Milky Way, or much larger, distant “island universes.” Hubble hoped to settle the debate once and for all.
When he developed the plate, he thought he saw a “nova,” or stellar explosion, on the outskirts of one of Andromeda’s spiral arms. He labeled the tiny black dot “N.” But when he compared the plate with other photographs taken on different dates, he realized that the star was actually a Cepheid variable, a kind of star that brightens and dims on a regular schedule. By measuring its period and luminosity relative to other known variables, Hubble could then calculate its distance, thus revealing that Andromeda was a huge stellar system far outside the Milky Way. In his excitement, Hubble crossed out the “N” and wrote “VAR!” in its place.
Hubble devoted dozens of plates to observing Andromeda in search of more Cepheid variables that would confirm his original discovery. Like many astronomers of his time, he adorned these plates with colorful notations—circles and arrows that identify candidate Cepheid variables, reference stars, and other notable objects. He numbered each confirmed Cepheid variable in order, often followed by exclamation points, as if he couldn’t contain his excitement. In this digital print of a plate made in early 1924, you can make out the notation “V4!!!” in the lower left corner.
“My god, it’s full of stars!”
Although Hubble had proven that Andromeda was a massive galaxy, likely full of hundreds of billions of stars, it took two decades for astronomers to finally resolve the stars in its dense, central region. The first image [above], taken on a 5-by-7 inch plate, came about under unusual circumstances.
In 1943, at the height of World War II, the astronomer Walter Baade was at work on Mount Wilson. Being a German national, Baade was barred from war duties, and so spent his nights peering at the sky above Los Angeles, which was delightfully dark due to wartime brownouts. One night, he aimed the observatory’s 100-inch telescope at Andromeda, capturing for the first time individual stars in its nucleus. This shot laid the groundwork for Baade’s classification of stars into two types: young, hot stars that occupy a galaxy’s spiral arms, and their older, cooler relatives in the galaxy’s heart.
Nearly a century later, the image still astounds. When NASA astronomer Jane Rigby visited the Carnegie archive last year, she examined the plate under a loupe. “My god, it’s full of stars!” she exclaimed.
A supernova in a strange galaxy
The late astronomer Halton “Chip” Arp is best known for his 1966 Atlas of Peculiar Galaxies, for which he photographed hundreds of galaxies with strange shapes and behaviors. Among these was Stephan’s Quintet, five closely interacting galaxies undergoing violent collisions as far away as 300 million light-years. In one remarkable shot, taken five years after the Atlas’s publication at Palomar Observatory, in San Diego, he identified a supernova [labeled “SN” in the right image], which had exploded a month before. (The other arrows on this plate point to reference stars, which Arp used to calculate the supernova’s coordinates in space.) In an earlier shot [left], taken in 1964, this brilliant blast is noticeably absent.
A sweeping galactic survey
In the late 1970s and early 1980s, Allan Sandage, a onetime assistant to Hubble, and his collaborators conducted the first exhaustive survey of the Virgo Cluster, a bundle of galaxies that comprise the heart of the supercluster containing our own Milky Way. To do this, the astronomers made 67 enormous, 20-inch-square photographic plates, which together produced a catalogue of 2,096 galaxies. The image above shows just a small fraction of one plate, which Sandage made at Las Campanas Observatory, in Chile, in 1980. He painstakingly located and measured each galaxy one-by-one, noting their catalog number and magnitude directly onto the plate in red and green ink.
Cynthia Hunt is the Social Media Strategic Coordinator for the Carnegie Observatories. Since receiving her Ph.D. from the California Institute of Technology, she has worked on a variety of projects, including cosmology detectors and rocket propulsion. | 0.911749 | 3.941445 |
From: Particle Physics and Astronomy Research Council
Posted: Sunday, June 2, 2002
Scientists at the University of Leicester's Space Research Centre are recreating the hostile environment found on Mars in their laboratory, with a device known as the Martian Environment Simulator (MES). The machine reproduces the temperature, air pressure and unbreathable atmosphere known to exist on Mars. The MES is currently being used to test equipment on the Beagle 2 lander, part of the European Space Agency's Mars Express Spacecraft and due to arrive on Mars during Christmas 2003. The chance of Beagle 2 finding life, either current or past, on the red planet has increased recently due to the discovery of ice beneath the planet's surface. The MES will be used to test all future instruments for planetary science being developed at the Space Research Centre.
Instruments that work in space need to be thoroughly tested to ensure that they will work in the extreme conditions found there and also to calibrate the readings that will be transmitted back to Earth. Researchers need to be sure that the gases in the atmosphere of another planet will not cause electrical arcing that damages the instruments. The MES creates an environment where the air is made mostly of carbon dioxide and the temperature can vary between a freezing minus 10 degrees Celsius (Martian daytime temperature) and a deadly minus 80 degrees (Martian night). The Martian air pressure at the surface is only 6mbar compared to an average pressure of 1bar on Earth. This means that the air pressure at surface level is lower than that at which the highest altitude commercial flights can travel at on Earth!
The MES incorporates a special sample wheel where geological materials can be attached, making it possible to test instruments designed to analyse rocks or soil on the surface of Mars.
Images of the MES, Mars Express and Mars are available at www.pparc.ac.uk or from Gill Ormrod in the PPARC press office.
Credit: MES - University of Leicester
Mars1 - Copyright NASA, Picture taken using the Hubble Space Telescope
Features - Copyright Jim Bell, Cornell University
Mars Express1 - Artists impression, Copyright ESA/Medialab
University of Leicester, Physics and Astronomy Department
Tel: (+ 44) (0) 116 223 1045
Fax: (+ 44) (0) 116 252 2464
Mobile: 07740 646 413
PPARC Press Office
Tel: 01793 442012
Fax: 01793 442002
The Particle Physics and Astronomy Research Council (PPARC) is the UK's strategic science investment agency. It funds research, education and public understanding in four areas of science - particle physics, astronomy, cosmology and space science.
PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), and the European Space Agency. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank observatory.
PPARC`s Public Understanding of Science and Technology Awards Scheme funds both small local projects and national initiatives aimed at improving public understanding of its areas of science.
// end // | 0.819378 | 3.027996 |
The South Pole of Enceladus
Enceladus is a medium-sized, icy moon of Saturn. The South Pole of Enceladus is one of the oddest places in the Solar System. Temperatures near the pole are far warmer than anywhere else on the moon, huge cracks criss-cross the region, and geysers spew ice crystals hundreds of kilometers into the sky.
Several huge gouges, averaging 130 km long by 2 km wide and 500 meters deep, run across the region of Enceladus's southern pole. These giant cracks have been nicknamed "tiger stripes". Scientists can tell, by counting meteorite craters, that this region around the South Pole is geologically younger than the rest of the moon's surface. They have also discovered that the South Pole is by far the warmest place on the moon, especially near the tiger stripes. This cannot be the case if Enceladus is heated by sunlight alone. The young surface, enormous "tiger stripe" cracks, and high temperatures all indicate that Enceladus (or at least the area around its South Pole) is geologically active.
The Cassini spacecraft discovered direct evidence of this geologic activity - it captured images of ice geysers erupting from the southern polar region of Enceladus! This moon of Saturn is one of only four bodies in our Solar System on which we have observed eruptions (the three others being Jupiter's volcanic moon Io, Neptune's moon Triton, and of course Earth). Scientists aren't quite sure yet how the ice geysers on Enceladus work, nor are they certain what supplies the heat to drive them. Perhaps there are subsurface reservoirs or aquifers of liquid water on Enceladus; this possibility piques the interest of astrobiologists. In any case, the ice geysers are an area of active research.
Scientists have spotted multiple plumes of ice from geysers, possibly emanating from more than one of the tiger stripe cracks. The ice crystals are flung hundreds of kilometers above Enceladus's surface; some even leave the moon altogether, contributing material to one of Saturn's rings. Ice that falls back to the moon's surface coats it with a bright layer akin to newfallen snow, making Enceladus the most reflective (highest albedo) body in the Solar System. The bright surface reflects away sunlight, keeping the moon cold; the average temperature on Enceladus is a chilly -200° C (-328° F). | 0.816683 | 3.947355 |
Today, Nature published the landmark discovery of a system of seven planets around a star named TRAPPIST-1 about 40 light years away. This star is a red dwarf that is much cooler and smaller than our yellow sun; it is about the size of Jupiter. This is the first time that several planets the size of Earth have all been found within the habitable zone, suggesting the possibility that liquid water–and perhaps life–could exist on one of these worlds.
The temperature of a planet is related to how close or how far away it is from it’s star. Our planet is 93 million miles from our star, the Sun, and because we exist, we can be sure that the conditions here on Earth support life. The habitable zone is the region around a star where an orbiting planet is able to sustain the presence of liquid water on its surface. In a way, the habitable zone is the “Goldilocks zone,” where a planet is neither too hot nor too cold for life.
What is particularly exciting about this discovery is that three of the seven planets are in the habitable zone, all of which are very close to the size of Earth. So far, none of these planets have been confirmed to have water on them, but NASA scientists say that the three planets in the habitable zone could be able to support to liquid water, so it is worth a look.
How do astronomers know all of this information? The observations were confirmed by multiple ground-based telescopes, the TRAPPIST–South telescope, the Very Large Telescope (VLT) at Paranal, and a space telescope known as the NASA Spitzer space telescope. Scientists use multiple instruments to observe the same system to be sure it is significant, and this discovery is big news.
Telescopes aren’t what they were in the days of Isaac Newton. Scientists no longer need to look through a lens to see celestial bodies. Those types of telescopes would not have the resolution or power to detect the presence of planets around stars that are so far away. In fact, Spitzer is not actually “seeing” the planets themselves. Carefully measuring the brightness of the star system for lengthy periods of time allows Spitzer to measure dimming in the star’s light as each planet passes in front of the star along its orbit, like a solar eclipse. The amount of dimming in light corresponds to the size of the planet. Astronomers are able to analyze the number of dimming events, which showed a pattern of seven different bodies passing by the star.
The telescopes were then able to determine the distance that each planet orbits the star by measuring the timing of each dimming event. The less frequent events represented planets that were further away from the star and the more frequent events indicated closer planets. The six inner planets orbit their sun in 1 ½, 2 ½, 4, 6, 9, and 12 Earth days. This is very quick compared to the length of time it takes Earth to orbit the Sun, which is 365 days.
We have come a long way in our ability to detect planets outside of our solar system. The field of exoplanet research is booming. NASA scientists say that it is not a matter of if we discover a habitable planet, but only when. | 0.893625 | 3.832619 |
Astronomy, which etymologically means laws of the stars, is the science whose subject is the observation and explanation of events outside the earth. Astrophysics was born as the application of physics to the phenomena observed by astronomy, this was only possible once it was understood that the elements that made up the "celestial objects" were the same that made up the Earth, and that the same laws of physics applied. Nearly all astronomers now have a strong background in physics, and the results of observations are always put in an astrophysical context, so the distinction between astronomy and astrophysics almost doesn't exist anymore.
In the early part of its history, Astronomy involved only the observation and predictions of the motions of the objects in the sky that could be seen with the naked eye. Astronomers were also usually priests, and for a long time it was believed that celestial phenomena had an influence on events on earth. Greeks made some important contributions to astronomy, but the progress almost stopped during the middle ages, except for the work of some Arabic astronomers. The renaissance came to astronomy with the work of Copernicus, who proposed a heliocentric system. His work was defended, expanded and corrected by the likes of Galileo and Kepler. Newton created celestial dynamics with his law of gravitation, that finally explained the motions of the planets. Stars were found much later to be far away objects, and with advent of spectroscopy it was proved that they were similar to our own sun, but with a range of temperatures, masses and sizes. The existence of our Galaxy, the Milky Way, as a separate group of stars was only proven 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. Cosmology, a discipline that has a large intersection with astronomy, made huge advances during the 20th century, with the model of the hot big bang heavily supported by the evidence provided by astronomy and physics.
For a more detailed history of astronomy, see the history of astronomy.
Division by way of obtaining information
Given its huge scope, astronomy is divided into different branches. The divisions are not unique, however, and the intersections, as well as astronomers who work in several areas, are the rule more than the exception.
In astronomy, the main way of obtaining information is through the detection and analysis of electromagnetic radiation. A traditional division of astronomy is given by the region of the electromagnetic spectrum observed:
- Optical Astronomy refers to the techniques used to detect and analize light in and slightly around the wavelengths than can be detected with the eyes (about 400 - 800 nm). The most common tool is the telescope.
- Infrared Astronomy deals with using infrared radiation (wavelengths longer than the red light). Again, the most common tool is the telescope, but at longer wavelengths. Space telescopes are also used to eliminate noise ( electromagnetic interference) from the atmosphere.
- Radio Astronomy uses completely different instruments to detect radiation of wavelengths of mm to cm. The receivers are similar to those used in radio broadcast transmission (which uses those wavelengths of radiation). See also Radio Telescopes.
Optical and radio astronomy can be done using ground-based observatories, because the atmosphere is transparent at those wavelengths. Infrared light is heavily absorbed by water vapor, so infrared observatories have to be located in high, dry places or in space.
The atmosphere is opaque at the wavelengths used by X-ray Astronomy, gamma-ray Astronomy, UV Astronomy and Far Infrared Astronomy, and so observations can be carried out only from balloons or space observatories.
All the previous disciplines are based on the detection of photons, but we also receive information from outside the earth carried by cosmic rays, neutrinos, and, in the near future, gravitational waves (see LIGO).
Division by subject
Astronomers study many objects including planets, stars, novae, star clusters, galaxies, nebulae, etc. but not every astronomer observes every kind of object. A different division can be made using the regions of space and problems addressed; among them
- Galactic Astronomy
- Extragalactic Astronomy
- Galaxy Formation and Evolution
- Star formation
- Stellar evolution
- Stellar Astronomy
Also, there are other disciplines that may be considered part of astronomy, or are interdisciplinary sciences with astronomy one of the disciplines:
Astronomy is one of the few sciences where amateurs still play an active role.
If your favorite area of research is not mentioned, feel free to add it.
(wikipedia is not a dictionary. Do not add a new page unless the subject deserves one)
- obliquity of the ecliptic
- retrograde orbit
- prograde orbit
- Lagrangian points
- apparent magnitude
- absolute magnitude
- astronomical unit
- H-R diagram
- Stellar classification
- cosmic distance ladder
- planetary nomenclature
See also space science.
What are our priorities for writing in this area? To help develop a list of the most basic topics in Astronomy and Astrophysics, please see Astronomy and Astrophysics basic topics. | 0.817885 | 3.702655 |
Saturn’s icy 246-mile-wide moon Mimas (near lower left) appears tiny by comparison to the planet’s rings, but scientists think the all of the small, icy particles spread over a vast area that comprise the rings are no more than a few times as massive as Mimas. The view was obtained by NASA’s Cassini spacecraft at a distance of approximately 564,000 miles from Saturn.
Researchers using NASA’s Mars Reconnaissance Orbiter have determined that frozen beneath a region of cracked and pitted plains on the Red Planet there lies about as much water as fills Lake Superior, largest of the Great Lakes. Scientists examined part of Mars’ Utopia Planitia region with the orbiter’s ground-penetrating instrument, revealing a deposit more extensive in area than the state of New Mexico.
A thrilling ride is about to begin for NASA’s Cassini spacecraft. Engineers have been pumping up the probe’s orbit around Saturn this year to increase its tilt with respect to the planet’s equator and rings. And on 30 November, following a gravitational nudge from Saturn’s moon Titan, Cassini will enter the first phase of the mission’s dramatic endgame.
The brightest area on Ceres stands out amid shadowy, cratered terrain in a dramatic new view from NASA’s Dawn spacecraft, taken as it looked off to the side of the dwarf planet. Dawn snapped this image from about 920 miles (1,480 kilometres) above Ceres in its fifth science orbit, in which the angle of the Sun was different from that in previous orbits.
In a first-of-its-kind collaboration, NASA’s Spitzer and Swift space telescopes joined forces to observe a microlensing event, when a distant star brightens due to the gravitational field of at least one foreground cosmic object. This technique is useful for finding low-mass bodies orbiting stars, such as planets. In this case, the observations revealed a brown dwarf.
The Moon’s Orientale basin is an archetype of “multi-ring” basins found throughout the solar system. New research has enabled scientists to reconstruct Orientale’s formation using data from NASA’s GRAIL mission. It is now thought that the 580-mile-wide feature was created 3.8 billion years ago by an impacting object some 40 miles across travelling at about 9 miles per second.
The NASA/ESA Hubble Space Telescope has detected superhot blobs of gas, each twice as massive as the planet Mars, being ejected near a dying red giant star in the V Hydrae binary system. The plasma balls are zooming so fast through space it would take only 30 minutes for them to travel from Earth to the Moon. | 0.894828 | 3.782755 |
Like finding buried treasure, this new image of the Carina Nebula has uncovered details not seen before. This vibrant image, from ESO’s Very Large Telescope shows not just the brilliant massive stars, but uncovers hundreds of thousands of much fainter stars that were previously hidden from view. Hundreds of individual images have been combined to create this picture, which is the most detailed infrared mosaic of the nebula ever taken and one of the most dramatic images ever created by the VLT.
Although this nebula is spectacular when seen through telescopes, or in normal visible-light pictures, many of its secrets are hidden behind thick clouds of dust. Using HAWK-I infrared camera along with the VLT, many previously hidden features have emerged from the murk. One of the main goals of the astronomers, led by Thomas Preibisch from the University Observatory, Munich, Germany, was to search for stars in this region that were much fainter and less massive than the Sun. The image is also deep enough to allow the detection of young brown dwarfs.
The dazzling but unstable star Eta Carinae appears at the lower left of the new picture. This star is likely to explode as a supernova in the near future, by astronomical standards. It is surrounded by clouds of gas that are glowing under the onslaught of fierce ultraviolet radiation. Across the image there are also many compact blobs of dark material that remain opaque even in the infrared. These are the dusty cocoons in which new stars are forming.
The Carina Nebula lies about 7,500 light-years from Earth in the constellation of Carina.
This video zooms in on the new infrared view of the Carina Nebula: | 0.802146 | 3.417937 |
A spinning gas halo discovered around the Milky Way
Astronomers have been surprized to discover that a halo of hot gas surrounding the Milky Way galaxy is spinning in the same direction and at a comparable speed to the galaxy’s disk. Scientists had thought this enormous reservoir of hot gas remained stationary while the Milky Way spins inside it.
The Square Kilometer Array reaches another milestone
Scientists have completed another key step in their efforts to build what will be the world’s largest radio telescope, the SKA or Square Kilometer Array. Researchers have successfully tested astronomical verification of a critical sub-system for the giant telescope known as the frequency synchronisation system.
Farewell to Rosetta’s Philae lander
European Space Agency mission managers have formally switched off the system on the Rosetta spacecraft which provides communications links between the orbiter and its tiny Philae lander. Switching off the system is part of the preparations for Rosetta's end of mission which is slated for September 30.
Scientists figured out last common ancestor of all living things
Scientists think they’ve worked out the genetic make-up of the last common ancestor of all living things. Researchers found our earliest common ancestor probably consisted of just 355 genes and made its living around superheated deep sea hydrothermal vents about four billion years ago.
The annual Delta Aquariid Meteor shower underway
The annual Delta Aquariid Meteor shower is at its peak with the best viewing about now because it coincides with a new moon providing darker skies. The shower is best for observed from the Southern hemisphere.
Clues to one of the largest asteroid impacts in Earth’s history discovered in Western Australia
Evidence for one of the largest asteroid impacts to ever have hit the Earth has been discovered in Western Australia. The impact – which occurred about 3.46 billion years ago -- is the second oldest dated collision in the planet’s history.
Why galaxies stop making stars
A new study has determined why galaxies stop making new generations of stars. Astronomers found two separate processes are involved in ending star formation.
The hunt for dark matter continues following another failed search for the elusive particle
A 20 month long search for a mysterious particle which makes up 80 percent of all the matter in the universe has failed to uncover the elusive identity of dark matter. The Large Underground Xenon dark matter experiment yielded no trace of a candidate particle despite the most sensitive search even conducted.
A new type of sand dune discovered on Mars
Scientists have discovered a new type of sand dune on the surface of the red planet Mars which is unlike anything seen on Earth.
The newly identified dune appears to be intermediate in size between tiny ripples and larger wavier dunes.
A bounty of Brown Dwarfs and planets discovered deep in the Orion Nebula
New technology allowing astronomers to peer deeper into the heart of the Orion Nebula than ever before, has revealed a massive population of previously unseen planets and brown dwarfs. The discovery shows that the Orion Nebula may be forming proportionally far more low-mass objects than closer and less active star formation regions.
Astronomers produce the most detailed map yet of the visible universe.
Astronomers have produced the largest-ever, three-dimensional map yet of the visible universe -- showing some 1.2 million galaxies -- covering over a quarter of the sky and mapping out the structure of the universe over a volume of 650 cubic billion light-years. The new map allows scientists to make the best measurements so far of the effects of a mysterious force called dark energy on the expansion of the universe and consequently the ultimate fate of the cosmos.
Astronomers discover how the fabled man in the moon got his right eye
A new study has discovered that a huge asteroid or protoplanet which crashed into the Moon 3.8 billion years ago was responsible for giving the fabled man in the moon his right eye. The massive 250 kilometre wide space rock created the Moon’s iconic Imbrium Basin as a result of the impact. This new size estimate means the Imbrium impactor was at least two times larger and 10 times more massive than previous estimates.
NASA’s mission to touch the Sun
NASA’s first mission to “touch” the Sun has passed a critical development milestone keeping it on track for launch in July 2018. The Solar Probe Plus mission will send a spacecraft on a series of data-collecting runs through the Sun’s atmosphere.
Ancient supernovae affected life on Earth
Two ancient supernovae which erupted within 300 light years of Earth likely exposed biology on our planet to a long-lasting cosmic radiation. The findings are based on new computer simulations of the impact the two exploding stars had on surrounding space.
Solving the mystery of the Martian moons
Astronomers may have finally solved the mystery of how the two Martian moons -- Phobos and Deimos -- were formed. Two separate and independent studies have both concluded that the moons were formed by collision events early in the red planet’s history.
Newly discovered planet has three Suns
If you thought Luke Skywalker’s home planet, Tatooine, was a strange world with its two Suns in the sky, imagine a planet where you’d either experience constant daylight or enjoy triple sunrises and sunsets every day. This isn’t the opening scene for some future episode of Star Wars but rather the vista seen from the surface of the distant exoplanet, HD 131399Ab.
Flying Dragon targets International Space Station
A SpaceX Falcon 9 rocket has blasted into orbit from the Cape Canaveral Air Force base -- lighting up the early morning skies of the Florida Atlantic coast – on a two day flight bound for the International Space Station. The Falcon 9 is carrying a Dragon cargo ship loaded with two tonnes of fresh supplies, scientific experiments, and space station equipment as part of a SpaceX contract with NASA to supply the orbiting outpost.
We turn our eyes to the skies as Jonathan Nally -- the editor of Australian Sky and Telescope Magazine -- takes us on a journey through this month’s night skies with Skywatch.
First evidence explaining how supermassive black holes are formed
Astronomers have discovered evidence for an unusual kind of black hole which would have been born in the very early universe and could have been the seeds for today’s supermassive black holes.
While astronomers have a good handle on how stellar mass black holes are formed – mystery has always surrounded their larger counterparts -- the supermassive black holes found at the centre of most if not all galaxies.
New dwarf planet discovered beyond Neptune
It’s not the long sort after mysterious planet 9 – but a new dwarf planet has been discovered orbiting the Sun beyond Neptune.
Astronomers spotted the distant frozen world using the Canada-France-Hawaii Telescope on Mauna Kea. The new object -- designated 2015 RR245 is about 700 kilometres in diameter and has one of the largest orbits of any known dwarf planet.
Rosetta’s mission to end on September 30
The European Space Agency has announced that its Rosetta spacecraft will complete its mission on September 30 performing a controlled descent to the surface of Comet 67P/Churyumov-Gerasimenko.
The pioneering probe made history in August 2014 becoming the first spacecraft to enter orbit around a comet.
Citizen scientists discover a massive galaxy cluster
Two volunteer participants in an international citizen science project have discovered a rare galaxy cluster which has now been named in their honour. The pair pieced together the huge C-shaped structure -- located some 1.2 billion light years away -- from much smaller images of cosmic radio waves shown to them as part of the web-based Radio Galaxy Zoo project.
New Type of Meteorite Linked to Ancient Asteroid Collision
Scientists have discovered a new type of meteorite never before seen on Earth. The space rock, appears to be from the missing partner in a massive asteroid collision 470 million years ago.
Physicists discover family of tetraquarks
Physicists have confirmed the existence of a new group of sub atomic particles called tetraquarks.
Scientists at Syracuse University confirmed the existence of the rare exotic particle as well as three siblings using the Large Hadron Collider beauty LHCb detector at CERN theEuropean Organization for Nuclear Research.
Curiosity Mars rover unexpectedly shuts down
NASA's Mars Curiosity rover shut down unexpectedly over the weekend. The car sized six wheel robot suddenly put itself into safe standby mode on July second.
Virgin Galactic to start test flights of its newest spaceship
Virgin Galactic is about to start test flying its newest space plane The Unity which replaces the original SpaceShipTwo Enterprise which crashed into the Mojave Desert back in January 2014. Test fights will begin next month with full suborbital space flights beginning in 2017.
Black hole discovered hiding in plain sight
Astronomers have detected a previously unseen black hole that’s been hiding in plain sight. The findings indicate the newly discovered black hole is located about 7,200 light years away, well within our own Milky Way galaxy. Because the study only covered a very small patch of sky, the findings imply that there should be tens of thousands to millions of these unseen black holes in the Milky Way -- thousands more than previous studies suggested.
Water found on Brown dwarf
Astronomers have -- for the first time -- found evidence of water in the clouds around a nearby brown dwarf. The discovery represents the strongest evidence yet for the existence of clouds of water or water ice, outside of our solar system.
New Soyuz capsule launches to Space Station
Roscosmos has launched its newly upgraded Soyuz MS series capsule on its maiden flight to the International Space Station.
The Soyuz MS-01 spacecraft blasted off from the Baikonur Cosmodrome in the central Asian republic of Kazakhstan carrying three Expedition 48 crew members to the orbiting outpost.
2016 will be a second longer
On December 31, 2016, a “leap second” will be added to the world’s clocks at 23 hours, 59 minutes 59 seconds Greenwich mean time. Historically, time was based on the mean rotation of the Earth relative to celestial bodies, and the second was defined in this reference frame. However, the invention of atomic clocks defined a much more precise “atomic” timescale and a second that is independent of Earth’s rotation
Juno orbit insertion
After a journey lasting almost five years and 2.7 billion kilometres, NASA’s Juno spacecraft has successfully entered orbit around Jupiter the largest planet in the Solar System. The spacecraft will spend at least 20 months circling the Jovian world 37 times, skimming to within 4100 kilometres above the planet’s pink and salmon coloured cloud tops. During these flybys, Juno will probe beneath this obscuring cloud cover to try and understand the gas giant’s composition and the extent of its mysterious metallic hydrogen mantle which is thought responsible for Jupiter’s powerful radiation field.
Origin of unusual supernova discovered
Astronomers may have finally worked out why some supernovae explosions known as 'extraordinary supernovae' are brighter than others.
The discovery reported in the Publications of the Astronomical Society of Japan will help improve measurements of the Universe's expansion, and consequently the strength of Dark Energy which controls the ultimate final fate of the cosmos.
Studying the relics of the Milky Way’s first ever stars
Astronomers have moved a step closer to studying the first stars in the universe. These primordial stars were very different from today’s stars because they were made just a hundred million years after the big bang -- out of the pure hydrogen and helium produced in that event. That unique composition made these first stars blue giants from twenty to over a hundred times the mass of our Sun.
New Horizons gets green light for planned second Kuiper Belt flyby
Following its historic first-ever flyby of Pluto, NASA’s New Horizons mission has received the green light to fly onward to an object deeper in the Kuiper Belt, known as 2014 MU69. The spacecraft’s planned rendezvous with the ancient object -- considered one of the early building blocks of the solar system -- is January first 2019.
Mercury’s surface arose from deep inside
Scientists have found that several volcanic deposits on Mercury's surface require mantle melting to have started close to the planet's core-mantle boundary. NASA’s MESSENGER mission to Mercury has shown that the surface of the planet is very heterogeneous, but it can be classified into two main types of regions.
Planet 9 could be an alien world
A new study claims that the recently inferred hypothetical planet 9 could be an exoplanet that originally formed around another star and was later captured by our Sun billions of years ago. The findings are based on new computer simulations.
Most detailed view yet of the black hole at the centre of our galaxy
Astronomers have used the new GRAVITY instrument on the European Southern Observatory’s Very Large Telescope to obtain the most detailed observations yet of the supermassive black hole at the centre of our galaxy. The observations will allow scientists to test predictions of Albert Einstein's general theory of relativity.
Potential habitats for life found on Mars
Astronomers have found evidence of carbonates beneath the surface of Mars -- pointing to a warmer and wetter environment capable of fostering the emergence of life -- in the red planet’s past. The new findings include evidence for widespread buried deposits of iron and calcium rich Martian carbonates, which suggests a wetter past for the Red Planet.
Private missions to Mars
The Netherlands based Mars One organization says it’s continuing with its plans to send people on a one way mission to establish the first permanent human colony on the red planet by 2027. The project is one of several plans by non-government organisations to fly to Mars in the near future. Another – by SpaceX – is planning to launch a scientific satellite based on its Dragon capsule to the red planet in 2018.
Evidence for recent hydrothermal activity found on Ceres
A new study has found that those mysterious bright spots on the dwarf planet Ceres have the highest concentration of carbonate minerals ever seen beyond Earth. The findings indicate recent hydrothermal activity is the most likely cause for the bright spots which were detected by NASA’s Dawn spacecraft in Ceres Occator Crater.
Chinese conduct surprise launch of Long March 4B rocket
Beijing has carried out a surprise launch of a Long March-4B rocket from the Jiuquan Launch Centre in the Gobi Desert of north-western China's Gansu Province. The mission carried the second Shijian-16 experimental satellite which will be used for studying the effects of radiation and the orbital space environment on new equipment and technology.
The show notes for SpaceTime with Stuart Gary podcast | 0.949227 | 3.370117 |
Hidden beneath a thick atmosphere, volcanoes may still be erupting on the surface of Venus, a new study finds.
The findings, described in the journal Geophysical Review Letters, reveal that our nearest planetary neighbor could be far more active than previously thought.
Scientists often look to our neighboring planets to learn more about Earth’s past. Just next door, Mars is thought to have had water and perhaps an atmosphere thick enough to support life; tiny, sun-scorched Mercury still has a liquid outer core that powers a magnetic field, rather like Earth’s.
Venus, our closest planetary companion, could provide insights of its own, but it’s shrouded in thick clouds of sulfuric acid that block out visible light. And that’s too bad, said study coauthor James Head, a planetary geoscientist at Brown University, because in many ways it would be the best planet to study to learn more about Earth and its history.
“Venus – in terms of its size, its density, position in the solar system (which is important in its formative years) – is literally the most Earth-like planet,” Head said. “And I think that if we could see what was going on in the formative years of Earth, that would be really incredible.”
Russian landers in the 1970s and '80s revealed features that looked somewhat familiar: plateaus, features that looked like mountain belts, but surprisingly few craters on the surface. The terrain indicated that the surface had been active, undergoing the kind of geophysical churn seen on Earth.
Venus, like Mars, had clearly had volcanic activity in the distant past – but could it have some today?
“People were thinking, ‘Well, is it like the Earth, which is very active, or is it like the moon and Mars, which are like a bunch of craters?’” Head said.
Data from NASA’s Magellan spacecraft, which entered Venusian orbit in 1990, seemed to say that Venus was geophysically dead. But if it had been inactive for a very long time, then it should be heavily cratered, which is clearly not the case.
To get at that question, the scientists turned to the European Space Agency’s Venus Express spacecraft, using data from its Venus Monitoring Camera to look for bright spots that signaled local lava flows. They focused on the planet's rift zones, with the idea that any hot spots of geologic activity would be there.
Sure enough, the scientists found bright spots that indicate temperature spikes caused by flowing lava, a sign that Venus is still active. These spots don’t cover the planet, but pop up only along the rift lines crossing the planet’s surface.
The rift zones with these hot spots are somewhat reminiscent of the East African rift zone on Earth, Head said. While the dynamics on Venus are clearly very different than the ones on Earth today, Venus’ current activity could hint at what Earth looked like before its tectonic plates were formed.
“That’s why Venus is so important.... Maybe this is what the Earth looks like before plate tectonics got started," Head said. "Maybe we’re looking at the beginning of plate tectonics on Venus.”
Follow @aminawrite for more interplanetary science news. | 0.88808 | 3.999903 |
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to obtain spectra of the 2500 Å region in eight stars with metallicities ranging from [Fe/H] = -0.4 to -3.0, including the most metal-poor star ever observed for boron. Spectrum synthesis utilizing latest Kurucz model atmospheres has been used to determine the B abundance for each star, with particular attention paid to the errors of each point, to permit judgment of the quality of the fit of models of Galactic chemical evolution. Previous observations were combined with new ones, bringing the number of stars analyzed to 11.
The Evolution of Galactic Boron and the Production Site of the Light ElementsThe Astrophysical Journal
PublisherThe American Astronomical Society
Citation InformationPlease use publisher's recommended citation. | 0.856685 | 3.118251 |
Quasars are the brightest and most distant objects in the known universe. In the early 1960's, quasars were referred to as radio stars because they were discovered to be a strong source of radio waves. In fact, the term quasar comes from the words, "quasi-stellar radio source". Today, many astronomers refer to these objects as quasi-stellar objects, or QSOs. As the resolution of our radio and optical telescopes became better, it was noticed that these were not true stars but some type of as yet unknown star-like objects. It also appeared that the radio emissions were coming from a pair of lobes surrounding these faint star-like objects. It was also discovered that these objects were located well outside our own galaxy. Quasars are very mysterious objects. Astronomers today are still not sure exactly what these objects are. What we do know about them is that they emit enormous amounts of energy. They can burn with the energy of a trillion suns. Some quasars are believed to be producing 10 to 100 times more energy than our entire galaxy. All of this energy seems to be produced in an area not much bigger than our solar system.
A pulsar is a rapidly spinning neutron star
. A neutron star is the highly compacted core of a dead star, left behind in a supernova explosion. This neutron star has a powerful magnetic field. In fact, this magnetic field is about one trillion times as powerful as the magnetic field of the Earth. The magnetic field causes the neutron star to emit strong radio waves and radioactive particles from its north and south poles. These particles can include a variety of radiation, including visible light. Pulsars that emit powerful gamma rays are known as gamma ray pulsars
. If the neutron star happens to be aligned so that the poles face the Earth, we see the radio waves every time one of the poles rotates into our line of sight. It is a similar effect as that of a lighthouse. As the lighthouse rotates, its light appears to a stationary observer to blink on and off. In the same way, the pulsar appears to be blinking as its rotating poles sweep past the Earth. Different pulsars pulse at different rates, depending on the size and mass of the neutron star. Sometimes a pulsar may have a binary companion. In some cases, the pulsar may begin to draw in matter from this companion. this can cause the pulsar to rotate even faster. The fastest pulsars can pulse at well over a hundred times a second.
What is a Quasar?
We still do not know exactly what a quasar is. But the most recent evidence points to the possibility that quasars are produced by super massive black holes
consuming matter in an acceleration disk. As the matter spins faster and faster, it heats up. The friction between all of the particles would give off enormous amounts of light other forms of radiation such as x-rays. The black hole would be devouring the equivalent mass of one Sun per year. As this matter is crushed out of existence by the black hole, enormous amounts of energy would be ejected along the black hole's north and south poles. Astronomers refer to these formations as cosmic jets. Another possible explanation for quasars is that they are very young galaxies. Since we know very little about the evolutionary process of galaxies, it is possible that quasars, as old as they are, represent a very early stage in the formation of galaxies. The energy we see may be ejected from the cores of these very young and very active galaxies. Some scientists even believe that quasars are distant points in space where new matter may be entering our universe. This would make them the opposite of black holes. But this is only conjecture. It may be some time before we really understand these strange objects.
The first identified quasar was called 3C 273 and was located in the constellation Virgo. It was discovered by T. Matthews and A. Sandage in 1960. It appeared to be associated with a 16th magnitude star like object. Three years later, in 1963, It was noticed that the object had an extremely high red shift. The true nature of this object became apparent when astronomers discovered that the intense energy was being produced in a relatively small area. Today, quasars are identified primarily by their red shift. If an object is discovered to have a very high red shift and appears to be producing vast amounts of energy, it becomes a prime candidate for quasar research. Today more than 2000 quasars have been identified. The Hubble space telescope has been a key tool in the search for these elusive objects. As technology continues to enhance our windows to the universe, we may one day fully understand these fantastic lights. | 0.902595 | 3.877722 |
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The Venera (Russian: Венера, pronounced [vʲɪˈnʲɛrə]) series space probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus. As with some of the Soviet Union's other planetary probes, the later versions were launched in pairs with a second vehicle being launched soon after the first of the pair.
Ten probes from the Venera series successfully landed on Venus and transmitted data from the surface of Venus, including the two Vega program and Venera-Halley probes. In addition, thirteen Venera probes successfully transmitted data from the atmosphere of Venus.
Among the other results, probes of the series became the first human-made devices to enter the atmosphere of another planet (Venera 4 on October 18, 1967), to make a soft landing on another planet (Venera 7 on December 15, 1970), to return images from the planetary surface (Venera 9 on June 8, 1975), and to perform high-resolution radar mapping studies of Venus (Venera 15 on June 2, 1983). The later probes in the Venera series successfully carried out their mission, providing the first direct observations of the surface of Venus. Since the surface conditions on Venus are extreme, the probes only survived on the surface for durations varying between 23 minutes (initial probes) up to about 2 hours (final probes).
The Venera probesEdit
Venera 1 and 2Edit
The first Soviet attempt at a flyby probe to Venus was launched on February 4, 1961, but failed to leave Earth orbit. In keeping with the Soviet policy at that time of not announcing details of failed missions, the launch was announced under the name Tyazhely Sputnik ("Heavy Satellite"). It is also known as Venera 1VA.
Venera 1 and Venera 2 were intended as fly-by probes to fly past Venus without entering orbit. Venera 1 was launched on February 12, 1961. Telemetry on the probe failed seven days after launch. It is believed to have passed within 100,000 km (62,000 mi) of Venus and remains in heliocentric orbit. Venera 2 launched on November 12, 1965, but also suffered a telemetry failure after leaving Earth orbit.
Several other failed attempts at Venus flyby probes were launched by the Soviet Union in the early 1960s, but were not announced as planetary missions at the time, and hence did not officially receive the "Venera" designation.
Venera 3 to 6Edit
The Venera 3 to 6 probes were similar. Weighing approximately one ton, and launched by the Molniya-type booster rocket, they included a cruise "bus" and a spherical atmospheric entry probe. The probes were optimised for atmospheric measurements, but not equipped with any special landing apparatus. Although it was hoped they would reach the surface still functioning, the first probes failed almost immediately, thereby disabling data transmission to Earth.
Venera 3 became the first human-made object to impact another planet's surface as it crash-landed on March 1, 1966. However, as the spacecraft's dataprobes had failed upon atmospheric penetration, no data from within the Venusian boundary were retrieved from the mission.
On 18 October 1967, Venera 4 became the first spacecraft to measure the atmosphere of another planet. While the Soviet Union initially claimed the craft reached the surface intact, re-analysis including atmospheric occultation data from the American Mariner 5 spacecraft that flew by Venus the day after its arrival demonstrated that Venus's surface pressure was 75-100 atmospheres, much higher than Venera 4's 25 atm hull strength, and the claim was retracted.
Realizing the ships would be crushed before reaching the surface, the Soviets launched Venera 5 and Venera 6 as atmospheric probes. Designed to jettison nearly half their payload prior to entering the planet's atmosphere, these craft recorded 53 and 51 minutes of data, respectively, while slowly descending by parachute before their batteries failed.
The Venera 7 probe was the first one designed to survive Venus surface conditions and to make a soft landing. Massively overbuilt to ensure survival, it had few experiments on board, and scientific output from the mission was further limited due to an internal switchboard failure which stuck in the "transmit temperature" position. Still, the control scientists succeeded in extrapolating the pressure (90 atm) from the temperature data with 465 °C (869 °F), which resulted from the first direct surface measurements. The Doppler measurements of the Venera 4 to 7 probes were the first evidence of the existence of high-speed zonal winds (up to 100 metres per second (330 ft/s) or 362 kilometres per hour (225 mph)) in the Venusian atmosphere (super rotation).
Venera 7's parachute failed shortly before landing very close to the surface. It impacted at 17 metres per second (56 ft/s) and toppled over, but survived. Due to the resultant antenna misalignment, the radio signal was very weak, but was detected (with temperature telemetry) for 23 more minutes before its batteries expired. Thus, it became, on 15 December 1970, the first human-made probe to transmit data from the surface of Venus.
Venera 8 was equipped with an extended set of scientific instruments for studying the surface (gamma-spectrometer etc.). The cruise bus of Venera 7 and 8 was similar to that of earlier ones, with the design ascending to the Zond 3 mission. The lander transmitted data during the descent and landed in sunlight. It measured the light level but had no camera. It continued to send back data for almost an hour.
Venera 9 to 12Edit
The Venera 9 to 12 probes were of a different design. They weighed approximately five tons and were launched by the powerful Proton booster. They included a transfer and relay bus that had engines to brake into Venus orbit (Venera 9 and 10, 15 and 16) and to serve as receiver and relay for the entry probe's transmissions. The entry probe was attached to the top of the bus in a spherical heat shield. The probes were optimized for surface operations with an unusual looking design that included a spherical compartment to protect the electronics from atmospheric pressure and heat for as long as possible. Beneath this was a shock absorbing "crush ring" for landing. Above the pressure sphere was a cylindrical antenna structure and a wide dish shaped structure that resembled an antenna but was actually an aerobrake. They were designed to operate on the surface for a minimum of 30 minutes. Instruments varied on different missions, but included cameras and atmospheric and soil analysis equipment. All four landers had problems with some or all of their camera lens caps not releasing.
The Venera 9 lander operated for at least 53 minutes and took pictures with one of two cameras; the other lens cap did not release.
The Venera 10 lander operated for at least 65 minutes and took pictures with one of two cameras; the other lens cap did not release.
The Venera 11 lander operated for at least 95 minutes but neither cameras' lens caps released.
The Venera 12 lander operated for at least 110 minutes but neither cameras' lens caps released.
Venera 13 and 14Edit
The descent craft/lander contained most of the instrumentation and electronics, and was topped by an antenna. The design was similar to the earlier Venera 9–12 landers. They carried instruments to take scientific measurements of the ground and atmosphere once landed, including cameras, a microphone, a drill and surface sampler, and a seismometer. They also had instruments to record electric discharges during its descent phase through the Venusian atmosphere.
The two descent craft landed about 950 km (590 mi) apart, just east of the eastern extension of an elevated region known as Phoebe Regio. The Venera 13 lander survived for 127 minutes, and the Venera 14 lander for 57 minutes, where the planned design life was only 32 minutes. The Venera 14 craft had the misfortune of ejecting the camera lens cap directly under the surface compressibility tester arm, and returned information for the compressibility of the lens cap rather than the surface. The descent vehicles transmitted data to the buses, which acted as data relays as they flew by Venus.
Veneras 15 and 16Edit
Venera 15 and 16 were similar to previous probes, but replaced the entry probes with surface imaging radar equipment. Radar imaging was necessary to penetrate the dense cloud of Venus.
The Vega probes to Venus and comet 1/P Halley launched in 1985 also used this basic Venera design, including landers but also atmospheric balloons which relayed data for about two days. "Vega" is an agglutination of the words "Venera" (Venus in Russian) and "Gallei" (Halley in Russian).
There were many scientific findings about Venus from the data retrieved by the Venera probes. For example, after analyzing the radar images returned from Venera 15 and 16, it was concluded that the ridges and grooves on the surface of Venus were the result of tectonic deformations.
Venera camera successes and failuresEdit
The Venera 9 and 10 landers had two cameras each. Only one functioned because the lens covers failed to separate from the second camera on each lander. The design was changed for Venera 11 and 12, but this change made the problem worse and all cameras failed on those missions. Venera 13 and 14 were the only landers on which all cameras worked properly; although unfortunately, the titanium lens cap on Venera 14 landed precisely on the area which was targeted by the soil compression probe.
The external link at the bottom of the page shows all lander imagery.
Flight data for all Venera missionsEdit
|Name||Mission||Launch||Arrival||Survival time min||Results||Orbiter or probe (flyby, atmospheric)||Lander coordin.|
|1VA (proto-Venera)||Flyby||February 4, 1961||N/A||N/A||Failed to leave earth orbit||N/A|
|Venera 1||Flyby||February 12, 1961||N/A||N/A||Communications lost en route to Venus||N/A|
|Venera 2MV-1 No.1||Atmospheric probe||August 25, 1962||N/A||N/A||Escape stage failed; Re-entered three days later||N/A|
|Venera 2MV-1 No.2||Atmospheric probe||September 1, 1962||N/A||N/A||Escape stage failed; Re-entered five days later||N/A|
|Venera 2MV-2 No.1||Flyby||September 12, 1962||N/A||N/A||Third stage exploded; Spacecraft destroyed||N/A|
|Venera 3MV-1 No.2||Flyby||February 19, 1964||N/A||N/A||Did not reach parking orbit||N/A|
|Kosmos 27||Flyby||March 27, 1964||N/A||N/A||Escape stage failed||N/A|
|Venera 2||Flyby||November 12, 1965||N/A||N/A||Communications lost just before arrival||N/A|
|Venera 3||Atmospheric probe||November 16, 1965||N/A||N/A||Communications lost just before atmospheric entry. This was the first manmade object to land on another planet on March 1966 (crash). Probable landing region: -20° to 20° N, 60° to 80° E.||N/A|
|Kosmos 96||Atmospheric probe||November 23, 1965||N/A||N/A||Failed to leave Earth orbit and reentered the atmosphere. Believed by some researchers to have crashed near Kecksburg, Pennsylvania, USA on December 9, 1965, an event which became known as the "Kecksburg Incident" among UFO researchers. All Soviet spacecraft that never left Earth orbit, were customarily renamed "Kosmos" regardless of the craft's intended mission. The name is also given to other Soviet/Russian spacecraft that are intended to—and do reach Earth orbit.||N/A|
|Venera 4||Atmospheric probe||June 12, 1967||October 18, 1967||N/A||The first probe to enter another planet's atmosphere and return data. Although it did not transmit from the surface, this was the first interplanetary broadcast of any probe. Landed somewhere near latitude 19° N, longitude 38° E.||
|Kosmos 167||Atmospheric probe||June 17, 1967||N/A||N/A||Escape stage failed; Re-entered eight days later||N/A|
|Venera 5||Atmospheric probe||January 5, 1969||May 16, 1969||53*||Successfully returned atmospheric data before being crushed by pressure within 26 kilometres (16 mi) of the surface. Landed at 3° S, 18° E.||N/A|
|Venera 6||Atmospheric probe||January 10, 1969||May 17, 1969||51*||Successfully returned atmospheric data before being crushed by pressure within 11 kilometres (6.8 mi) of the surface. Landed at 5° S, 23° E.||N/A|
|Venera 7||Lander||August 17, 1970||December 15, 1970||23||The first successful landing of a spacecraft on another planet, and the first broadcast from another planet's surface. Survived for 23 minutes before succumbing to heat and pressure.|
|Kosmos 359||Lander||August 22, 1970||N/A||N/A||Escape stage failed; Ended up in an elliptical Earth orbit||N/A||N/A|
|Venera 8||Lander||March 27, 1972||July 22, 1972||50||Landed within a 150 kilometres (93 mi) radius of 10.70° S, 335.25° E.|
|Kosmos 482||Probe||March 31, 1972||N/A||N/A||Escape stage exploded during Trans-Venus injection; Some pieces re-entered and others remained in Earth orbit||N/A||N/A|
|Venera 9||Orbiter and Lander||June 8, 1975||October 22, 1975||53||Sent back the first (black and white) images of Venus' surface. Landed within a 150 kilometres (93 mi) radius of 31.01° N, 291.64° E.|
|Venera 10||Orbiter and Lander||June 14, 1975||October 25, 1975||65||Landed within a 150 kilometres (93 mi) radius of 15.42° N, 291.51° E.|
|Venera 11||Flyby and Lander||September 9, 1978||December 25, 1978||95||The lander arrived, but the imaging systems failed.|
|Venera 12||Flyby and Lander||September 14, 1978||December 21, 1978||110||The lander recorded what is thought to be lightning.|
|Venera 13||Flyby and Lander||October 30, 1981||March 1, 1982||127||Returned the first colour images of Venus' surface, and discovered leucite basalt in a soil sample using a spectrometer.|
|Venera 14||Flyby and Lander||November 14, 1981||March 5, 1982||57||A soil sample revealed tholeiitic basalt (similar to that found on Earth's mid-ocean ridges).|
|Venera 15||Orbiter||June 2, 1983||October 10, 1983||N/A||Mapped (along with Venera 16) the northern hemisphere down to 30 degrees from North (resolution 1-2 km)||N/A|
|Venera 16||Orbiter||June 7, 1983||October 14, 1983||N/A||Mapped (along with Venera 15) the northern hemisphere down to 30 degrees from North (resolution 1-2 km)||N/A|
|Vega 1||Flyby and Lander||December 15, 1984||June 11, 1985||N/A||Part of the Vega program. The vessel was en route to Halley's Comet. During entry into atmosphere, the surface instruments began work early, and the lander failed. See Vega 1.|
|Vega 2||Flyby and Lander||December 21, 1984||June 15, 1985||56||Part of the Vega program. The vessel was en route to Halley's Comet. See Vega 2.|
- Wade, Mark. "Venera 1VA". Encyclopedia Astronautica. Retrieved 28 July 2010.
- NSSDC Chronology of Venus Exploration (NASA Goddard Space Flight Center), see also NSSDC Tentatively Identified (Soviet) Missions and Launch Failures (NASA Goddard Space Center), accessed August 9, 2010
- Ultimax Group's Venus Exploration Atlas page (accessed Aug 18 2010)
- Basilevsky, A. T.; Pronin, A. A.; Ronca, L. B.; Kryuchkov, V. P.; Sukhanov, A. L.; Markov, M. S. (1986). "Styles of tectonic deformations of Venus - Analysis of Venera 15 and 16 data (abstract only)". Journal of Geophysical Research. Journal of Geophysical Research March 30, 1986, p. D399-D411. 91: 399. Bibcode:1986JGR....91..399B. ISSN 0148-0227. doi:10.1029/JB091iB04p0D399. | 0.837212 | 3.395721 |
Billions of potentially populated planets in the galaxy
Loads of Earthlike worlds in the habitable zone around stars
There are billions of habitable planets in the Milky Way where aliens could be having their tea right now, according to a new six-year study.
"Our results show that planets orbiting around stars are more the rule than the exception. In a typical solar system approximately four planets have their orbits in the terrestrial zone, which is the distance from the star where you can find solid planets." said astronomer Uffe Gråe Jørgensen from the Niels Bohr Institute.
Turns out the galaxy is more crowded than we thought
Star-gazing boffins from PLANET, the Probing Lensing Anomalies Network, used the gravitational microlensing technique to spot the worlds lying in the habitable zone around a star, which differs from the 'transit' method used by NASA's Kepler mission.
The 'transit' way to find planets looks for dips in the brightness of a star that would show that a planet had passed in front of it. But planets that are either very far or very close to their star can be missed by this technique.
Microlensing uses one star as a 'lens' to amplify the light from a star behind it. If one star passes precisely in front of another, the gravity of the one in front bends the light from the one behind. If there's a planet orbiting the front star, that can produce additional brightening, which reveals the planet.
Microlensing events from a star alone last around a month, but if there's a planet involved, the extra brightening goes on for a few hours or days.
There's also a third method of detection, known as the radial velocity method, which measures how much a star rocks in small circular motions due to a revolving planet's gravitational force.
The microlensing process can tell boffins the mass of the planet, but unfortunately, it can't give the scientists any idea of what that world is made of. Just because a world is within the habitable zone, doesn't necessarily mean it will have the life-giving composition of our own planet.
"Together, the three methods are, for the first time, able to say something about how common our own solar system is, as well as how many stars appear to have Earth-size planets in the orbital area where liquid what could, in principle, exist as lakes, rivers and oceans - that is to say, where life as we know it from Earth could exist in principle,” said Jørgensen.
Of the 40 or so microlensing events the astronomers studied, three showed evidence for exoplanets. Statistically, the research team extrapolates that one in six stars has a Jupiter-sized planet, half have one the same mass as Neptune and two-thirds have an Earth 2.0.
Two thirds of stars could have Earth-sized planets
“This means, statistically, every star in the galaxy should have at least one planet, and probably more,” said Kailash Sahu, of the Space Telescope Science Institute in Baltimore.
“Results from the three main techniques of planet detection are rapidly converging to a common result: Not only are planets common in the galaxy, but there are more small planets than large ones,” said Stephen Kane, a co-author from NASA’s Exoplanet Science Institute. “This is encouraging news for investigations into habitable planets.”
The studies combine to tell us there are plenty of planets with the right temperature to support life, but whether the other building blocks are around or not remains to be seen.
“There are so many unique events in our solar system that have created the basis for the development of life on Earth," Jørgensen said.
"Comets brought water to our planet so that life could arise and a series of random events set in motion an evolution that lead to humans and intelligent life. It is very unlikely that the same circumstances would be present in other solar systems."
But just so we're not totally disappointed the continual absence of proof of aliens, he added; “perhaps other coincidences in other solar systems have led to entirely different and exciting new forms of life".
The research has been published in this week's Nature.® | 0.890084 | 3.625708 |
The Ring Nebula is one
of the most famous objects in the sky and perhaps the most spectacular
example of a planetary nebula. It is bright, relatively large and
most important of all, easy to find midway between two bright stars in
in a 90mm ETX at 50x with a Meade Super Wide Angle 24.5mm eyepiece.
The field of view (circle) is 79'. The two bright stars are Sulafat
(Gamma, 14 Lyr) and Sheliak (Beta, 10 Lyr). Note how the position
of M57 midway between these stars makes it very easy to find.
The Ring is visible in a
3-inch telescope as an elongated hazy spot. A 6-inch scope will reveal
the famous smoke ring structure. Many observers describe M57 as having
a slight greenish tint. Users of larger telescopes should try to
see the faint central star. The magnitude of this star is uncertain
(perhaps as faint as 14.7 magnitude) and may be variable. There is
some question concerning how large an aperture is required to see it.
Due to the surrounding nebulosity it may be more difficult to see than
another star of similar magnitude. A 14 inch may be required for
most observers on a typical night. I've seen it in my 18 inch with
little trouble. Another difficult but rewarding observation is to
see the structure in the fainter central nebula. With a 16-inch or
larger scope look for streaks or streamers.
At the end of an observing
session I often like to look up a few old friends such as M57. After
years of observing these favorites no chart is needed to find them.
I am always struck by the combination of size and brightness in the Ring,
particularly after spending the evening hunting down other tiny, faint
examples of planetary nebulae. The Ring may not be the largest planetary.
It's not even the brightest. But it is without question best.
The above image
is from the Hubble Space Telescope. The vivid colors are not visible
in the eyepiece at all. In the photograph they provide an indication
of the different types of gases and conditions throughout the nebula.
In the Hubble Space Telescope
image blue traces very hot helium gas. Green represents hot oxygen
and red indicates relatively cooler nitrogen. It first appeared that
we were viewing M57 as an irregular, spherical bubble in space about the
faint central star. The bright edges which form the apparent ring
were explained as the result of looking through more glowing material at
the edges of the shell. Some researchers pointed out as early as 1960 that
this might not be the case because the difference of brightness between
the inner nebula and outer ring was too great. In recent years evidence
has accumulated that the real shape of the Ring nebula may be a cylinder
and we are viewing it from one end. If viewed from another direction
it would probably look very different, perhaps more like the Little Dumbbell
nebula (M76). Note the dark spots that are made by small, dark clouds
superimposed on the glowing gas. Few of these clouds are found in
the middle of the nebula, suggesting that the overall structure is truly | 0.830088 | 3.912081 |
NASA published the results of processing data obtained in August 2016 by the Juno apparatus from the orbit of Jupiter. Images show that the largest planet in the solar system represents a very complex turbulent world. On this planet there are giant polar-sized cyclones with the size of the Earth with storms that go down to the heart of the planet.
In addition, the scientists found that the magnetic field of Jupiter is much stronger than previously thought.
Juno was launched on August 5, 2011. On July 4, 2016, he entered the orbit of Jupiter. August 27, he collected the first portion of data on the gas giant, flying at a distance of 4.2 thousand kilometers from the upper clouds of Jupiter.
The images taken by the JunoCam camera show that both poles of Jupiter close a storm the size of the Earth. They are very close, literally touching each other.
Scientists used to know that Jupiter possesses the strongest magnetic field among the planets of the solar system. However, according to the data obtained by the magnetometer of the apparatus, the magnetic field of Jupiter proved to be even stronger than expected. The induction of the planet’s magnetic field was 7.766 Gauss, which is 10 times greater than that of the Earth. The intensity of the magnetic field of Jupiter varies greatly: in some places it is weaker, in others it is stronger.
Juno is in polar orbit. Most of his coil he spends away from the planet, but every 53 days he approaches the north pole of Jupiter, after which he makes a two-hour transit to the south pole. During this period, all eight instruments of the probe are used. Sending 6 megabytes of data received during this flight can take 1.5 days.
The next rapprochement of Juno will take place on July 11. The device will have to capture one of the most impressive formations on Jupiter – the Great Red Spot. | 0.82364 | 3.1443 |
SkyHopper is an international collaboration to put a small robotic infrared telescope in space to observe some of the most distant and powerful explosions in the Universe, and to search and characterize planets orbiting other stars, alongside other exciting new science. Bright objects in space emit light at a wide range of frequencies, but individual telescopes can each only see a small range. Infrared light, which is at longer wavelengths than visible, is ideal for observing light from some of the most distant objects in the Universe. However, infrared telescopes on Earth are hindered by the fact that the water in our atmosphere absorbs a substantial amount of the light coming through at infrared frequencies, and glows at similar frequencies, creating an elevated background. By sending our telescope to space, we can get above that atmosphere and have a much clearer view of astronomical objects. And by employing CubeSat technology, we can do it all on a relatively small budget.
SkyHopper is optimized for “transient” science — that is, it will observe sources that change with time. The three main science targets for SkyHopper are:
- Distant gamma-ray bursts.Existing space telescopes looking at high-energy gamma radiation see hundreds of bright flashes of light every year. These are due to powerful explosions of distant stars, and are visible from across the observable universe. Optical (visible-light) telescopes can follow up on these bursts and observe the explosion “afterglow”, produced by the interaction of the shock-wave with the surrounding inter-stellar gas. However, the most distant gamma-ray bursts require follow-up in the infrared because of cosmological redshift of the light. SkyHopper will be able to quickly respond to gamma-ray burst alerts and point at the sources, letting us see the early afterglows of the most distant explosions in the Universe. Since the more distant an object, the further back in time we see it, SkyHopper’s observations will contribute to our understanding of how the first generations of stars and galaxies are formed in the youth of the Universe.
- Exoplanets around red dwarf stars.Thanks to recent observations, we now know that the Galaxy is teeming with planets — on average, each star in the night sky has at least one planet in orbit around it. The Kepler space telescope has found thousands of planets orbiting other stars by making use of the transit technique — watching as a star gets periodically dimmer due to its planet passing in front of it in its orbit. However, despite this bounty of thousands of exoplanets, we know of very few that are within their star’s “habitable zone,” the orbital distance at which the surface temperature should allow water to pool on the surface in liquid form. Some astronomers have suggested that the best approach for finding potentially habitable planets would be to look not at Sun-like stars, but at red dwarf stars. These smaller, cooler stars are far more numerous in the Galaxy and have habitable zones much closer to them than larger stars do. This improves the chance of an alignment favourable for transit studies, and vastly increases the number of targets, but infrared observations are required. SkyHopper will help us find habitable planets by looking for transits on red dwarf stars, an important step in the search for life beyond our Solar System.
- Other transient sources.The so-called “transient sky” is still wide open for exploration. Because very few telescopes at any wavelength range are optimized to look for short time-period changes in their targets, there’s a vast frontier where new space phenomena might yet be discovered. One of the most exciting astronomical discoveries in recent years has been that of Fast Radio Bursts (FRBs): short (millisecond-timescale) flashes of radio light from unknown distant sources. SkyHopper will be capable of following up FRBs to search for infrared afterglows, potentially giving us invaluable information about their origins and nature. Because of SkyHopper’s fast response and its frequency range in the infrared, it will be exploring a part of the transient sky that might contain other new phenomena yet to be imagined. In addition to the expected targets listed above, SkyHopper will make use of its fast response and unique perspective to keep an eye out for the unexpected. | 0.906394 | 4.106743 |
Subsets and Splits