text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
Yes, it’s true: a rather not-so-tiny near-Earth
asteroid SKULL-SHAPED ZOMBIE COMET (see below) 2015 TB145 will make a relatively close pass by our dear planet Earth on October 31, aka Halloween — the day when certain beliefs profess that the veil separating the worlds of the living and the dead is at its thinnest, allowing spiritual and even physical interaction to occur between both.
Of course there is no scientific evidence that the latter is at all true but it makes for good scary stories around the light of a campfire. And as the first-world campfires of today are the stark lights of computer monitors and smartphone screens, some are trying to weave scary stories about the passing of this asteroid as well. Should you be afraid? Certainly not. (But there is a cautionary tale to be told.)
While there isn’t anything to be concerned about from 2015 TB145, it will pass relatively near to Earth, coming as close as about 500,000 kilometers (310,000 miles) at 17:05 UTC on Oct. 31.* And it is of considerable size — somewhere in the range of 290-650 meters (950-2,133 feet) in diameter, which isn’t enormous for asteroids BUT you certainly wouldn’t want it landing in your back yard (especially considering that it’s traveling an “unusually high” relative velocity of almost 35 km/s… that’s over 78,000 mph!)
If you’re thinking that seems like a big size range for an object like this to “possibly” be, there’s a reason (and thus the cautionary tale) — 2015 TB145 was just discovered this month.
The NEO 2015 TB145 was identified on Oct. 10, 2015 via the PanSTARRS I (Panoramic Survey Telescope & Rapid Response System) survey telescope, located atop Mount Haleakala in Hawaii. The goal of PanSTARRS is specifically to locate objects like this, so it accomplished exactly what it should. But it also reminds us that there are still as-yet undiscovered objects out there orbiting the Sun in the vicinity of our planet, and it’s important that we maintain vigilance and continue supporting global efforts to find and study them.
As it passes Earth 2015 TB145 will be observed with some of the best radar telescopes on the planet — NASA’s DSS-13 at Goldstone, California and NRAO’s Green Bank Telescope in West Virginia (and possibly also with the Arecibo Observatory in Puerto Rico.) Because TB145 is so dark (absolute magnitude currently listed as 19.8) optical observations won’t reveal much, but radar can help scientists “see” the asteroid and determine its size, shape, and rotation and better plot out its orbital trajectory into the future…especially where it concerns its encounters with our planet.
According to a news statement on NASA’s Goldstone site, “The flyby presents a truly outstanding scientific opportunity to study the physical properties of this object.”
(Who knows… they may find that it has a little moon of its own. There are plenty of asteroids that do.)
NASA won’t be the only ones watching this object’s pass either — plenty of amateur astronomers around the world will have their ‘scopes set on 2015 TB145’s path, especially in the Middle East where it will still be dark during its closest approach. Find out how to view TB145 here, and you can watch a live broadcast of the viewing on the Slooh site here starting at 12:30 p.m. ET (16:30 UTC) on Oct. 31.
There is some significance to this pass too: this will be the closest known approach by an object this large until the 800-meter asteroid 1999 AN10 approaches at about 1 lunar distance in August 2027. (Source)
And, based on TB145’s orbit and high velocity, it’s suspected that it might even actually be a comet.
“The asteroid’s orbit is very oblong with a high inclination to below the plane of the solar system,” said Lance Benner of JPL, who leads NASA’s asteroid radar research program. “Such a unique orbit, along with its high encounter velocity — about 35 kilometers or 22 miles per second — raises the question of whether it may be some type of comet. If so, then this would be the first time that the Goldstone radar has imaged a comet from such a close distance.”
So while NASA isn’t spooked by 2015 TB145 (and you shouldn’t be either) we should all still be aware that we’re certainly not the only ones traveling on this road around the Sun… there’s always the chance of running into the occasional traffic. It’s important that we spot them — especially the big ones — first.
“We as humans are living on a planet that’s in a sort of celestial shooting gallery, and there are lots of objects out in space, primarily asteroids, that come close and do hit us from time to time.”
— David Morrison, Senior Scientist at NASA Ames Research Laboratory (Ret.)
*2015 TB145 will also pass closely by our Moon, coming within about two-thirds that distance two and a half hours prior.
UPDATE 10/30: radar observations from the Arecibo Observatory have been used to create an image of the quite-dark 2015 TB145 and, if it wasn’t spooky enough that the asteroid is passing on Halloween, it even bears an uncanny resemblance to a giant skull and it might really be a comet — a dead one. Read more here.
Just for fun (whee!) I ran some of the known values for 2015 TB145 through an online impact calculator developed by Dr. Andrew Scott at the University of South Wales. Assuming that TB145 is composed of mainly porous rock (if it’s a comet it could even be less dense; if a stony/iron asteroid more) then a totally direct strike on Earth at a 90º angle in, say, New York City would leave a crater 9,767 feet (2,977 meters) wide and 2,080 feet (634 m) deep — bigger than Barringer Crater in Flagstaff, AZ. Luckily impacts of this magnitude are 1-in-75,000-plus year events (and don’t specifically target major cities!) But needless to say it would be a very bad day in the Big Apple. | 0.872726 | 3.390873 |
The Hubble Space Telescope (HST), which is running its 25th year in the space currently, spotted a little gem – a planetary nebula, there.
The planetary nebula known as “NGC 6818” or “Little Gem Nebula” is an intergalactic cloud of dust, helium, hydrogen and many other ionized gases. It is situated in the constellation of Sagittarius also called “The Archer”, and is nearly 6,000 light-years far from the Earth.
Although the powerful glow of the bolus is more than only half a light-year beyond it is enormous considered to its petite central star. However, it is still a minute gem on a celestial degree.
When sun – a form of a star goes to “retirement,” it peels off its exterior coating to foster shimmering bolus of gas known as planetary nebulae. This expulsion of mass is irregular, and planetary nebulae might end up with quite complicated shapes. Little Gem reflects difficult thread-like structures and separate layers of material apart from a shining and engulfed central bubble encompassed by a bigger, more disseminated cloud.
NASA scientists believe that the planetary wind from the central star pushes the peeled off material, molding the extended shape of Little Gem. “As this fast wind smashes through the slower-moving cloud it creates particularly bright blowouts at the bubble’s outer layers,” NASA added.
Earlier this, Hubble captured the picture of this very nebula way back in 1997 with the latter’s Wide Field Planetary Camera 2. It used an amalgamation of filters, which threw light on the discharge from ionized oxygen and hydrogen.
The new picture seized by Hubble albeit used the same camera it used back in 1997, utilized varied filters to divulge a diverse sight of the nebula. | 0.893273 | 3.428139 |
Dwayne Brown/Tabatha Thompson
Kennedy Space Center, Fla.
NASA's THEMIS Mission Launched to Study Geomagnetic Substorms
CAPE CANAVERAL, Fla. - NASA's THEMIS mission successfully launched Saturday, Feb. 17, at 6:01 p.m. EST from Pad 17-B at Cape Canaveral Air Force Station, Fla.
THEMIS stands for the Time History of Events and Macroscale Interactions during Substorms. It is NASA's first five-satellite mission launched aboard a single rocket. The spacecraft separated from the launch vehicle approximately 73 minutes after liftoff. By 8:07 p.m. EST, mission operators at the University of California, Berkeley, commanded and received signals from all five spacecraft, confirming nominal separation status.
The mission will help resolve the mystery of what triggers geomagnetic substorms. Substorms are atmospheric events visible in the Northern Hemisphere as a sudden brightening of the Northern Lights, or aurora borealis. The findings from the mission may help protect commercial satellites and humans in space from the adverse effects of particle radiation.
THEMIS' satellite constellation will line up along the sun-Earth line, collect coordinated measurements, and observe substorms during the two-year mission. Data collected from the five identical probes will help pinpoint where and when substorms begin, a feat impossible with any previous single-satellite mission.
"The THEMIS mission will make a breakthrough in our understanding of how Earth's magnetosphere stores and releases energy from the sun and also will demonstrate the tremendous potential that constellation missions have for space exploration," said Vassilis Angelopoulos, THEMIS principal investigator at the University of California, Berkeley. "THEMIS' unique alignments also will answer how the sun-Earth interaction is affected by Earth's bow shock, and how 'killer electrons' at Earth's radiation belts are accelerated."
The Mission Operations Center at the University of California, Berkeley, will monitor the health and status of the five satellites. Instrument scientists will turn on and characterize the instruments during the next 30 days. The center will then assign each spacecraft a target orbit within the THEMIS constellation based on its performance. Mission operators will direct the spacecraft to their final orbits in mid-September.
During the mission the five THEMIS satellites will observe an estimated 30 substorms in process. At the same time, 20 ground observatories in Alaska and Canada will time the aurora and space currents. The relative timing between the five spacecraft and ground observations underneath them will help scientists determine the elusive substorm trigger mechanism.
"I am proud to manage the fifth medium class mission of the Explorer Program," said Willis S. Jenkins, the THEMIS program executive. "As we seek the answer to a compelling scientific question in geospace physics, we are keeping up the tradition that began with Explorer I."
NASA's Launch Services Program at the Kennedy Space Center was responsible for the launch of THEMIS aboard a Delta II rocket. The United Launch Alliance, Denver, provided launch service.
For additional information about THEMIS, news media should contact Cynthia O'Carroll, Goddard Space Flight Center, Md., at 301-286-4647 or Robert Sanders, University of California, Berkeley, at 510-643-6998.
The Explorer Program Office at Goddard manages the NASA-funded THEMIS mission. The Space Sciences Laboratory at the University of California, Berkeley, is responsible for project management, space and ground-based instruments, mission integration, mission operations and science. Swales Aerospace, Beltsville, Md., built the THEMIS probes. THEMIS is an international project conducted in partnership with Germany, France, Austria and Canada.
For more information about the THEMIS mission and imagery on the Web, visit: http://www.nasa.gov/themis
- end -
text-only version of this release
To receive status reports and news releases issued from the Kennedy Space Center Newsroom electronically, send a blank e-mail
message to [email protected]. To unsubscribe, send
a blank e-mail message to [email protected].
The system will confirm your request via e-mail. | 0.828069 | 3.03389 |
UCI’s Charles Limoli and colleagues found that exposure to highly energetic charged particles – much like those found in the galactic cosmic rays that will bombard astronauts during extended spaceflights – causes significant long-term brain damage in test rodents, resulting in cognitive impairments and dementia.
Their study appears today in Nature’s Scientific Reports. It follows one last year showing somewhat shorter-term brain effects of galactic cosmic rays. The current findings, Limoli said, raise much greater alarm. (Link to study:www.nature.com/articles/srep34774)
“This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars,” said the professor of radiation oncology in UCI’s School of Medicine. “The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel – such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life.”
For the study, rodents were subjected to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory at New York’s Brookhaven National Laboratory and then sent to Limoli’s UCI lab.
Six months after exposure, the researchers still found significant levels of brain inflammation and damage to neurons. Imaging revealed that the brain’s neural network was impaired through the reduction of dendrites and spines on these neurons, which disrupts the transmission of signals among brain cells. These deficiencies were parallel to poor performance on behavioral tasks designed to test learning and memory.
In addition, the Limoli team discovered that the radiation affected “fear extinction,” an active process in which the brain suppresses prior unpleasant and stressful associations, as when someone who nearly drowned learns to enjoy water again.
“Deficits in fear extinction could make you prone to anxiety,” Limoli said, “which could become problematic over the course of a three-year trip to and from Mars.”
Most notably, he said, these six-month results mirror the six-week post-irradiation findings of a 2015 study he conducted that appeared in the May issue of Science Advances.
Similar types of more severe cognitive dysfunction are common in brain cancer patients who have received high-dose, photon-based radiation treatments. In other research, Limoli examines the impact of chemotherapy and cranial irradiation on cognition.
While dementia-like deficits in astronauts would take months to manifest, he said, the time required for a mission to Mars is sufficient for such impairments to develop. People working for extended periods on the International Space Station, however, do not face the same level of bombardment with galactic cosmic rays because they are still within the Earth’s protective magnetosphere.
Limoli’s work is part of NASA’s Human Research Program. Investigating how space radiation affects astronauts and learning ways to mitigate those effects are critical to further human exploration of space, and NASA needs to consider these risks as it plans for missions to Mars and beyond.
Partial solutions are being explored, Limoli noted. Spacecraft could be designed to include areas of increased shielding, such as those used for rest and sleep. However, these highly energetic charged particles will traverse the ship nonetheless, he added, “and there is really no escaping them.”
Preventive treatments offer some hope. Limoli’s group is working on pharmacological strategies involving compounds that scavenge free radicals and protect neurotransmission.
Vipan Kumar Parihar, Barrett Allen, Chongshan Caressi, Katherine Tran, Esther Chu, Stephanie Kwok, Nicole Chmielewski, Janet Baulch, Erich Giedzinski and Munjal Acharya of UCI and Richard Britten of Eastern Virginia Medical School contributed to the study, which NASA supported through grants NNX13AK70G, NNX14AE73G, NNX13AD59G, NNX10AD59G, UARC NAS2-03144 and NNX15AI22G.
Source: University of California, Irvine | 0.805175 | 3.285615 |
Earth sits between two worlds that have been devastated by climate catastrophes. In the effort to combat global warming, our neighbours can provide valuable insights into the way climate catastrophes affect planets.
Modelling Earth’s climate to predict its future has assumed tremendous importance in the light of mankind’s influence on the atmosphere. The climate of our two neighbours is in stark contrast to that of our home planet, making data from ESA’s Venus Express and Mars Express invaluable to climate scientists.
Venus is a cloudy inferno whilst Mars is a frigid desert. As current concerns about global warming have now achieved widespread acceptance, pressure has increased on scientists to propose solutions.
The key weapon in a climate scientist’s arsenal is the climate model, a computer programme that uses the equations of physics to investigate the way in which Earth’s atmosphere works. The programme helps predict how the atmosphere might change in the future.
It seems that both Mars and Venus started out much more like Earth
“To members of the public it must seem like climate models are crystal balls, but they are actually just complex equations” says David Grinspoon, Denver Museum of Nature and Science, and one of Venus Express’s interdisciplinary scientists.
The more scientists look at those equations, the more they realise just how complicated Earth’s climate system is. Grinspoon puts the predicament like this: “In fifty or a hundred years, we will know whether today’s climate models were right but if they are wrong, by then it will be too late.”
To help increase confidence in the computer models, Grinspoon believes that scientists should look at our neighbouring planets. “It seems that both Mars and Venus started out much more like Earth and then changed. They both hold priceless climate information for Earth,” says Grinspoon.
The atmosphere of Venus is much thicker than Earth’s. Nevertheless, current climate models can reproduce its present temperature structure well. Now planetary scientists want to turn the clock back to understand why and how Venus changed from its former Earth-like conditions into the inferno of today.
They believe that the planet experienced a runaway greenhouse effect as the Sun gradually heated up. Astronomers believe that the young Sun was dimmer than the present-day Sun by 30 percent. Over the last 4 thousand million years, it has gradually brightened. During this increase, Venus’s surface water evaporated and entered the atmosphere.
“Water vapour is a powerful greenhouse gas and it caused the planet to heat-up even more. This is turn caused more water to evaporate and led to a powerful positive feedback response known as the runaway greenhouse effect,” says Grinspoon.
As Earth warms in response to manmade pollution, it risks the same fate. Reconstructing the climate of the past on Venus can give scientists a better understanding of how close our planet is to such a catastrophe. However, determining when Venus passed the point of no return is not easy. That’s where ESA’s Venus Express comes in.
The spacecraft is in orbit around Venus collecting data that will help unlock the planet’s past. Venus is losing gas from its atmosphere, so Venus Express is measuring the rate of this loss and the composition of the gas being lost. It also watches the movement of clouds in the planet’s atmosphere. This reveals the way Venus responds to the absorption of sunlight, because the energy from the Sun provides the power that allows the atmosphere to move.
In addition, Venus Express is charting the amount and location of sulphur dioxide in the planet’s atmosphere. Sulphur dioxide is a greenhouse gas and is released by volcanoes on Venus.
“Understanding all of this will help us pin down when Venus lost its water,” says Grinspoon. That knowledge can feed into the interpretation of climate models on the Earth because although both planets seem very different now, the same laws of physics govern both worlds.
Understanding Mars’ past is equally important. ESA’s Mars Express is currently investigating the fate of the Red Planet. Smaller than the Earth, Mars is thought to have lost its atmosphere to space. When Martian volcanoes became extinct, so did the planet’s means of replenishing its atmosphere turning it into an almost-airless desert.
What happened on these two worlds is different but would be disastrous for Earth
“What happened on these two worlds is very different but either would be equally disastrous for Earth. We are banking on our ability to accurately predict Earth’s future climate,” says Grinspoon. Anything that can shed light on our own future is valuable. That is why the study of our neighbouring worlds is vital.
So, when planetary scientists talk of exploring other worlds, they are also increasing their ability to understand our own planet.
For more information:
David Grinspoon, Venus Express interdisciplinary Scientist and Curator of Astrobiology
Dept. of Space Sciences
Denver Museum of Nature & Science, Co. (USA)
Email: David.Grinspoon @ dmns.org
Håkan Svedhem, ESA Venus Express Project scientist
Email: Håkan.svedhem @ esa.int | 0.873636 | 3.342012 |
Marcus Leech from ccera.ca is a pioneer in using low cost software defined radios for observing the sky with amateur radio telescopes. In the past he's shown us how to receive things like the hydrogen line, detect meteors and observe solar transits using an RTL-SDR. He's also given a good overview and introduction to amateur radio astronomy in this slide show.
His recent project has managed to create a full Hydrogen sky map of the northern Canadian sky. In his project memo PDF document Marcus explains what a sky map shows:
A [sky map] shows the brightness distribution over the sky for a given set of observing wavelengths. In the case of the 21cm hydrogen line wavelength, maps show the distribution of hydrogen over the sky. For amateur observers, such maps generally show the distribution within our own galaxy, since extra-galactic hydrogen is considerably more faint, and significantly red/blue shifted relative to the rest frequency of 1420.40575 MHz, due to relative motion between the observer and the target extra-galactic hydrogen.
He was able to make this observation using his radio telescope made from a 1.8m dish antenna, a NooElec 1420 MHz SAWBird LNA + Filter, a 15dB line amplifier, another filter and two Airspy R2 software defined radios locked to an external GPSDO. The system runs his custom odroid_ra software on an Odroid XU4 single board computer, which provides spectral data to an x86 host PC over an Ethernet connection.
Over 5 months of observations have resulted in the Hydrogen sky map shown at the end of this post. Be sure to check out his project memo PDF file for more information on the project and how the image was produced. Marcus' blog post over on ccera.ca also notes that more data and different maps will be produced soon too. | 0.896956 | 3.074824 |
Approximately 800,000 years ago something changed in the Earth’s climate system that led to the climate then following a series of approximately 100,000 year cycles. Small, predictable changes in the Earth’s orbit about the Sun act as triggers for the glacial and interglacial periods, but other factors such as ice sheet volume, CO2 concentration, and biological feedback mechanisms are also involved.Read more.
Evidence from Antarctic ice cores have revealed a close correlation between surface temperature and atmospheric carbon dioxide concentration for the past 800,000 years (excluding the immediate present.) A recent analysis of Antarctic blue ice has found that the close correlation between temperature CO2 extends to 1.5 million years ago during the time when the glacial/interglacial period was 40,000 years.
A seminal book by Milankovitch in 1941 proposed that the sequence of ice ages that has characterized long term changes in the Earth’s climate over the past hundreds of thousands of years was due to changes in the amount of solar radiation reaching the Earth as a result of small variations in the Earth’s orientation and orbit with respect to the sun. Since then research has shown that Milankovitch cycles by themselves do not determine the timing of glacial and interglacial cycles and that we still lack a unified mechanism that links changes in Earth’s orbit to ice ages.
Marine cores collected in the western tropical Pacific were used to compare the chronology of Southern Ocean warming near Antarctica and rising CO2 during the last deglaciation. The results provide evidence that the Southern Ocean off Antarctica warmed by ~2°C between 19,000 and 17,000 years before the present, about 1,000 years before the rise in atmospheric CO2.
This study reports measurements from ocean floor sediments that provide the first direct evidence that not only do variations in the primary North/South Atlantic current correlate with periods of rapid warming and slower cooling in the Northern Hemisphere during the last ice age, but that the changes in the Atlantic overturning current occurred before and likely initiated these warming/cooling cycles.
In contrast to West Antarctica where several large glaciers have been losing ice for decades, East Antarctica glaciers have exhibited little evidence of ice loss but NASA’s latest detailed maps of East Antarctica ice velocity and elevation show that a number of glaciers have begun to lose ice over the past decade.
Between 2005 and 2017 the U.S. economy as measured by real GDP expanded by about 20 %. Over this same period, emissions from power generation dropped which is evidence of a decoupling between economic growth and power generation. | 0.821775 | 3.590003 |
Scientists led by the University of Birmingham have found a solar system with five Earth-sized planets dating from the dawn of the galaxy.
The discovery, published in The Astrophysical Journal, was made possible by the NASA Kepler mission. Using a technique called asteroseismology, an international team of astronomers was able to observe a Sun-like star (Kepler-444) hosting five planets with sizes ranging between that of Mercury and Venus.
Kepler-444 was formed 11.2 billion years ago, when the universe was less than 20 per cent its current age. This is the oldest known system of territorial-sized planets in the Milky Way – more than twice as old as the Earth.
Existence of Life on Earth
The team was led by Dr Tiago Campante, from the University’s School of Physics and Astronomy. He said: ‘There are far-reaching implications for this discovery.
‘We now know that Earth-sized planets have formed throughout most of the Universe’s 13.8 billion-year history, which could provide scope for the existence of ancient life in the galaxy and help to pinpoint the beginning of what we might call the ‘era of planet formation’.
First glimpses of five Earth-sized planets
Professor Bill Chaplin, Dr Campante’s colleague and lead scientist on the Kepler Mission study of solar-type stars using asteroseismology, added: ‘We are now getting first glimpses of the variety of galactic environments conducive to the formation of these small worlds.
‘As a result, the path towards a more complete understanding of early planet formation in the galaxy is now unfolding before us.’ | 0.875083 | 3.20161 |
Titania – Learn About The Largest Moon Of Uranus
A World Of Craters, Canyons & Cliffs
Titania is the largest of the five spherical moons of Uranus and the 8th largest moon in the solar system, Titania was named after the Queen of the Fairies from Shakespeare's A Midsummer Night’s Dream. Similar in appearance to several of Uranus’ other spherical moons, Titania is heavily cratered with an extensive system of enormous canyons and scarps cutting across its surface.
Fast Summary Facts About Uranus' Moon Titania
- Discovered: January 11th, 1787 by William Herschel
- Name: Named after a character in Shakespeare's ‘A Midsummer Night's Dream’
- Size: Diameter of 1,578 km (980.5 miles)
- Moon Rank: 8th Largest in the solar system
- Orbit: Prograde and Circular
- Orbit Radius: 435,910 km from Uranus
- Orbital Period: 8 days, 8 hours, 28 minutes
- Orbital Speed: 3.64 km/sec
- Orbital Inclination: 0.34° (to Uranus’ equator)
- Rotation: Synchronous (rotates once every revolution so the same side always faces Uranus – known as tidally locked)
- Density: 1.71 g/cm3
- Surface: Equally water-ice, rock and trace Carbon Dioxide
- Surface Temperature: An Icy -200 °C (60 - 90K)
More Cool Interesting Facts About The Fractured Titania!
- As with the rings and the other large moons of Uranus, Titania orbits close to its planet's equatorial plane. This means the moons share Uranus' extreme seasonal cycle on account of each pole experiencing permanent night or day for half a Uranian year – which is 42 Earth years!
- Scientists believe that Titania, like all of Uranus’ large moons, is likely composed of approximately half ice and half rocky material that is likely differentiated into a rocky core and icy mantle. It is possible that a thin liquid ocean may exist between the mantle and core if sufficient ammonia (or similar antifreeze compounds) and core heat exists.
- Titania’s surface is predominately grey with a slight red in tint (but less so than the moon Oberon), with fresh craters appearing slightly blue.
- Titania has a lower density of craters than the moons Oberon and Umbriel, implying it has a younger surface, but its largest crater called Gertrude is over 325 km in diameter.
- Besides craters, the other major geological feature of Titania is a number of colossal faults, cliffs and wide canyons the longest of which is called Messina Chasma and extends for nearly 1,500 km!
- Carbon Dioxide has been detected on the shaded or colder surfaces of Titania, meaning the moon may experience an extremely thin, seasonal atmosphere of CO2.
- There are also some relatively smooth plains which are likely younger surfaces and may have been formed by resurfacing by internal fluid (cryovolcanism) or blanketing by ejecta from nearby impact craters.
- The orbit of Titania is entirely within Uranus’ magnetosphere resulting in its surface being protected from the solar winds, but also being exposed to Uranus’ magnetic plasma believed to lead to a darkening of its trailing hemisphere.
- Every 42 years, around the equinoxes, it’s possible to capture a rare transit of Titania as the moon passes in front of Uranus, it can even occult one of the other major moons during this period.
- It is believed that Titania formed billions of years ago, from the accretion disc that surrounded the newly formed Uranus; perhaps even from debris from the colossal impact that pushed Uranus onto its side!
- The only probe to have visited the Uranus system (and its moons) was the Voyager 2 spacecraft in 1986, where it managed to photograph 40% of Titania’s surface during the probes brief flyby.
- Unfortunately, there are no plans for any future probes to visit Uranus (and its moons), but one day it’s hoped that a Uranus orbiter reaches this distant outpost! | 0.8557 | 3.619445 |
eso1317 — Photo Release
A Ghostly Green Bubble
ESO's VLT snaps a planetary nebula
10 April 2013
This intriguing new picture from ESO’s Very Large Telescope shows the glowing green planetary nebula IC 1295 surrounding a dim and dying star located about 3300 light-years away in the constellation of Scutum (The Shield). This is the most detailed picture of this object ever taken.
Stars the size of the Sun end their lives as tiny and faint white dwarf stars. But as they make the final transition into retirement their atmospheres are blown away into space. For a few tens of thousands of years they are surrounded by the spectacular and colourful glowing clouds of ionised gas known as planetary nebulae.
This new image from the VLT shows the planetary nebula IC 1295, which lies in the constellation of Scutum (The Shield). It has the unusual feature of being surrounded by multiple shells that make it resemble a micro-organism seen under a microscope, with many layers corresponding to the membranes of a cell.
These bubbles are made out of gas that used to be the star’s atmosphere. This gas has been expelled by unstable fusion reactions in the star’s core that generated sudden releases of energy, like huge thermonuclear belches. The gas is bathed in strong ultraviolet radiation from the aging star, which makes the gas glow. Different chemical elements glow with different colours and the ghostly green shade that is prominent in IC 1295 comes from ionised oxygen.
At the centre of the image, you can see the burnt-out remnant of the star’s core as a bright blue-white spot at the heart of the nebula. The central star will become a very faint white dwarf and slowly cool down over many billions of years.
Stars with masses like the Sun and up to eight times that of the Sun, will form planetary nebulae as they enter the final phase of their existence. The Sun is 4.6 billion years old and it will likely live another four billion years.
Despite the name, planetary nebulae have nothing to do with planets. This descriptive term was applied to some early discoveries because of the visual similarity of these unusual objects to the outer planets Uranus and Neptune, when viewed through early telescopes, and it has been catchy enough to survive . These objects were shown to be glowing gas by early spectroscopic observations in the nineteenth century.
This image was captured by ESO’s Very Large Telescope, located on Cerro Paranal in the Atacama Desert of northern Chile, using the FORS instrument (FOcal Reducer Spectrograph). Exposures taken through three different filters that passed blue light (coloured blue), visible light (coloured green), and red light (coloured red) have been combined to make this picture.
Even early observers such as William Herschel, who discovered many planetary nebulae and speculated about their origin and composition, knew that they weren’t actually planets orbiting the Sun as they did not move relative to the surrounding stars.
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.90554 | 3.714657 |
Proving that old data never dies, scientists have found something new about Jupiter’s moon Io using data gathered during the Galileo mission, which orbited Jupiter from 1995-2003. New analysis reveals a subsurface ocean of molten or partially molten magma beneath the surface of the volcanic moon, which is the first direct confirmation of this kind of magma layer at Io. Scientists say the molten subsurface ocean explains why the moon is the most volcanic object known in the solar system.
“Scientists are excited we finally understand where Io’s magma is coming from and have an explanation for some of the mysterious signatures we saw in some of the Galileo’s magnetic field data,” said Krishan Khurana, from the University of California, Los Angeles, and lead author of the study published in Science. Khurana was a former co-investigator on Galileo’s magnetometer team at UCLA. “It turns out Io was continually giving off a ‘sounding signal’ in Jupiter’s rotating magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface.”
Amazingly, Io produces about 100 times more lava each year than all the volcanoes on Earth, and the new study shows that a global magma ocean exists about 30 to 50 kilometers (20 to 30 miles) beneath the moon’s crust. This explains why Io’s volcanoes are distributed all around its surface, unlike Earth’s volcanoes that occur in localized hotspots like the “Ring of Fire” around the Pacific Ocean.
The volcanoes on Io were discovered in 1979 by Linda Morabito, an optical navigation engineer working on the Voyager mission. Looking at images that were to be used for navigating Voyager, Morabito noted what appeared to be a crescent cloud extending beyond the edge of Io. After conferring with her colleagues, they realized that since Io has no atmosphere, the cloud rising hundreds of kilometers above the surface must be evidence of an incredibly powerful volcano.
The energy for the volcanic activity comes from the squeezing and stretching of the moon by Jupiter’s gravity as Io orbits the largest planet in the solar system.
Galileo was launched in 1989 and began orbiting Jupiter in 1995. Scientists noticed unexplained signatures in magnetic field data from Galileo flybys of Io in October 1999 and February 2000.
“During the final phase of the Galileo mission, models of the interaction between Io and Jupiter’s immense magnetic field, which bathes the moon in charged particles, were not yet sophisticated enough for us to understand what was going on in Io’s interior,” said Xianzhe Jia, a co-author of the study at the University of Michigan.
Recent work in mineral physics showed that a group of rocks known as “ultramafic” rocks become capable of carrying substantial electrical current when melted. Ultramafic rocks are igneous in origin, or form through the cooling of magma. On Earth, they are believed to originate from the mantle. The finding led Khurana and colleagues to test the hypothesis that the strange signature was produced by current flowing in a molten or partially molten layer of this kind of rock.
Tests showed that the signatures detected by Galileo were consistent with a rock such as lherzolite, an igneous rock rich in silicates of magnesium and iron found in Spitzbergen, Norway. The magma ocean layer on Io appears to be more than 50 kilometers (30 miles thick), making up at least 10 percent of the moon’s mantle by volume. The blistering temperature of the magma ocean probably exceeds 1,200 degrees Celsius (2,200 degrees Fahrenheit).
In the animation above, Io is bathed in magnetic field lines (shown in blue) that connect the north polar region of Jupiter to the planet’s south polar region. As Jupiter rotates, the magnetic field lines draping around Io strengthen and weaken. Because Io’s magma ocean has a high electrical conductivity, it deflects the varying magnetic field, shielding the inside of the moon from magnetic disturbances. The magnetic field inside of Io maintains a vertical orientation, even as the magnetic field outside of Io dances around. These variations in the external magnetic field signatures enabled scientists to understand the moon’s internal structure. In the animation, the magnetic field lines move with Jupiter’s rotation period of about 13 hours in Io’s rest frame.
Io is the only body in the solar system other than Earth known to have active magma volcanoes, and it has been suggested both the Earth and its moon may have had similar magma oceans billions of years ago at the time of their formation, but they have long since cooled.
“Io’s volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history,” said Torrence Johnson, a former Galileo project scientist who was not directly involved in the study.
The Galileo spacecraft was intentionally sent into Jupiter’s atmosphere in 2003 to avoid any contamination of any of Jupiter’s moons. | 0.830919 | 3.998667 |
SIX years from now, a huge copper bullet will slam into the surface of a
comet, gouging out a crater seven storeys deep. The project, dubbed Deep Impact,
is one of two space missions announced by NASA last week. The other, named
Messenger, is to put a spacecraft into orbit around Mercury.
When scientists study the clouds of gas emitted by a comet as it nears the
Sun, they’re never certain what originates from the comet itself and what comes
from the dirt picked up during the comet’s travels through the Solar System.
Deep Impact, which will cost $240 million, should solve this puzzle.
When the spacecraft approaches comet P/Tempel 1 on 4 July 2005, it will
release a half-tonne projectile that should strike the comet at ten kilometres a
second, hurling cometary material out into space. “The ejecta will be pristine
material from inside the comet,” says project manager James Graf of the Jet
Propulsion Laboratory in Pasadena.
Messenger, costing $286 million, will be the first spacecraft to visit
Mercury since Mariner 10 made three flybys in 1974. After settling into orbit
around the planet in 2009, the spacecraft will photograph its surface, record
the composition of its thin atmosphere, and map its magnetic field.
An altimeter will also measure any wobbles as the planet turns, which will
help determine whether there is liquid sloshing around beneath Mercury’s crust.
“Whether there’s a fluid core or not will help us understand the origin of
Mercury’s magnetic field and its thermal history,” says project leader Sean
Solomon of the Carnegie Institution of Washington. | 0.845254 | 3.31984 |
The atmospheres of thousands of nearby stars exhibit telltale fingerprints of the first massive stars of the universe, which exploded only a few million years after they were born.
“We can learn about the chemistry of the very early universe right in our own backyard, not just from studying faint sources more than 10 billion light years away,” said Timothy Beers, professor and Notre Dame Chair in Astrophysics at the University of Notre Dame. “They are rare, precious probes.”
Beers presented a briefing about his study of these stars June 5, 2018, during the American Astronomical Society meeting in Denver. His talk was one of 19 featured in a series of five press conferences that will take place during the five-day event.
In their death throes, early short-lived massive stars produced enormous amounts of light elements such as carbon, nitrogen and oxygen. These elements were incorporated into the next generation of stars, which were formed with a significantly lower mass — less than the mass of the sun. Their nuclear furnaces burn so slowly that they can be seen today in the halo of the Milky Way galaxy.
Spectroscopic evidence for thousands of such stars was gathered from large-scale surveys of the halo of the Milky Way galaxy, starting with their discovery by Beers and colleagues in 1992. These stars have enhanced amounts of light elements and a low abundance of heavy elements like gold and platinum, and are known as carbon-enhanced, metal-poor stars with no or few s- or r-process elements (CEMP-no stars).
Some CEMP-no stars are as close as 600 light years away and are visible with binoculars. They are now being studied at high spectral resolution by the world’s largest telescopes, as well as with the Hubble Space Telescope.
During his talk, Beers shared evidence that these CEMP-no stars formed from massive-star nucleosynthesis events that took place in low-mass galaxies. These small galaxies, called ultra-faint dwarfs (UFDs), were subsequently accreted by the halo of our galaxy, and their CEMP-no stars were strewn throughout as stellar debris. This connection is being used to trace how the Milky Way was formed.
“There is increasing evidence that the UFDs are the natural birthplace for most CEMP-no stars,” said Beers.
Although researchers have been aware of the association of carbon enhancement with old, chemically primitive stars, recent work led by Notre Dame postdoctoral researcher Jinmi Yoon has demonstrated that previous estimates of the frequency of CEMP-no stars in the halo were underestimated by roughly a factor of two. Among the most chemically primitive stars, the fraction of CEMP-no stars approaches 100%.
“New larger surveys, and a reanalysis of older surveys, are needed to refine our estimates and obtain a more complete story of their formation and evolution,” Beers said. “It’s an exciting time to be a galactic archaeologist!” | 0.865099 | 4.087746 |
Dawn concludes 2011 more than 40 thousand times nearer to Vesta than it began the year. Now at its lowest altitude of the mission, the bold adventurer is conducting its most detailed exploration of this alien world and continuing to make thrilling new discoveries.
Circling the protoplanet 210 kilometers (130 miles) beneath it every 4 hours, 21 minutes on average, Dawn is closer to the surface than the vast majority of Earth-orbiting satellites are to that planet. There are two primary scientific objectives of this low altitude mapping orbit (LAMO). With its gamma ray and neutron detector (GRaND), the probe is measuring the faint emanations of these subatomic particles from Vesta. Some are the by-products of the bombardment by cosmic rays, radiation that pervades space, and others are emitted through the decay of radioactive elements. Vesta does not glow brightly when observed in nuclear particles, so GRaND needs to measure the radiation for weeks at this low altitude. This is analogous to using a long exposure with a camera to photograph a dimly lit subject. If GRaND only detected the radiation, it would be as if it took a black and white picture, but this sophisticated instrument does more. It measures the energy of each particle, just as a camera can measure the color of light. The energies reveal the identities of the elements that constitute the uppermost meter (yard) of the surface. Dawn devotes most of its time now flying over Vesta to collecting the glimmer of radiation. It requires a long time, but this spacecraft has demonstrated tremendous patience in its use of the gentle but efficient ion propulsion system that made the mission possible, so it can be patient in making these measurements.
The second motivation for diving down so low is to be close enough that Vesta's interior variations in density affect the spacecraft's orbit discernibly. We have seen before that the distribution of mass inside the protoplanet reveals itself through the changing strength of its gravitational tug on Dawn. Exquisitely sensitive measurements of the ship's course can be translated into a three-dimensional map of the mass. In the plans discussed for LAMO one year ago, the delicate tracking of the spacecraft required pointing the main antenna to Earth. That provides a radio signal strong enough to achieve the required accuracy. Since then, navigators have determined that the radio signal received from one of the craft's auxiliary antennas, although far weaker, is sufficient. The main antenna broadcasts a tight beam, whereas the others emit over a much larger angle, exchanging signal strength for flexibility in pointing.
This allows an extremely valuable improvement. The spacecraft cannot aim GRaND at the surface and the main antenna at Earth concurrently, because both are mounted rigidly, just as you cannot simultaneously point the front of your car north and the back east. Therefore, in the original plan, gravity measurements and GRaND measurements were mutually exclusive. Now, as Dawn turns throughout its orbit to keep Vesta in GRaND's sights, it can transmit a weak radio signal that is just perceptible at Earth. This enables an even greater science return for the time in LAMO.
Unlike the science camera and the visible and infrared mapping spectrometer (VIR), GRaND and gravity observations do not depend on the sun's illumination of the surface. Even as it orbits over a dark, cold, silent landscape, Dawn is fully capable of continuing to build its maps of elements and the interior structure.
The signal from the auxiliary antenna is just sufficient for the measurement of the spacecraft's motion, but it is not strong enough to carry data as well. So the spacecraft is still programmed to point its main antenna to Earth three times each week, allowing the precious GRaND observations that have been stored in computer memory to be transmitted. As always, the myriad measurements of temperatures, voltages, currents, pressures, and other parameters that engineers use to ensure the health of the ship are returned during these communications sessions as well.
Although the pictures of Vesta from survey orbit and the high altitude mapping orbit (HAMO) have exceeded scientists' expectations, not only in quality and quantity but also in the truly fascinating content, as enthusiastic explorers, the Dawn team could not pass up the opportunity for more. When GRaND is pointed at the surface, the camera is too, and already well over one thousand images have been returned, revealing detail three times finer than the spectacular images from HAMO. For readers who cannot go to Vesta on their own, go here for a selection of the best views, each showing surprising and captivating alien landscapes.
NASA / JPL / UCLA / MPS / DLR / IDA / map by Jason Perry
Vesta's place names as of January 2012 (deprecated)
In addition to the bonus photography, beginning in January VIR will take observations. Although the instrument has already acquired nearly seven million spectra in the higher orbits, this new vantage point will allow sharper resolution, just as it does for the camera.
The ultra-long-distance communication between Dawn and Earth requires extraordinary technology on both ends. Even with all the sophistication, the amount of information that can be transmitted in a given time remains very limited. The remote spacecraft sends data at speeds significantly lower than a typical home Internet connection. Engineers use that precious communications link very carefully, judiciously selecting what information to instruct the probe to return. Because of the high priority given to GRaND, which needs to be pointed at the surface as long as possible, much of the limited time spent with the main antenna aimed at Earth is devoted to transmitting that instrument's findings (and the measurements of spacecraft subsystems). This restricts how much data from the camera and VIR can be communicated.
In the next log, we will see another limitation on the number of camera images and VIR spectra in LAMO. It is a consequence of another aspect of the complex operations in this low orbit around a massive body, and that is the small but real differences between the predicted orbit and the actual orbit. We will cover the first part of the explanation here.
Navigators use their best knowledge of the many forces acting on Dawn to chart an orbital course for it. The forces can be traced to three principal sources: gravity, light, and Dawn itself. We have discussed all of these before in detail (see, for example, this explication of the last two), but let's review them here. This is an involved story, so readers are advised to be in a comfortable orbit while following it. You can safely skip the next four paragraphs and no one ever need know.
Vesta has a complicated gravity field, and that leads to a complicated orbit. The spacecraft does not follow a perfectly circular, repetitive path because the gravitational pull on it changes according to where it is as the colossus beneath it rotates and it loops around. The map of the gravity field has been improving throughout Dawn's residence there, but its completion awaits the LAMO gravity measurements. In the meantime, unknown details of the variation of mass lead to small divergences in the orbit. All the other bodies in the solar system exert gravitational pulls on the spacecraft as well (just as they do on you), but those are more easily accounted for. The distances from Dawn are so great that the variations in their gravity fields don't matter. So although the effects of the faraway objects need to be accounted for, they do not contribute much to the discrepancies.
Dawn depends on sunlight for its power, using its large solar arrays to make electricity to run all systems. The sun also propels the spacecraft, because in the frictionless conditions of spaceflight, the ship recoils slightly in response to the miniscule but persistent pressure of the light. The force depends on whether the light is absorbed (whereupon it is converted to electrical power by the arrays or to heat by whatever component it illuminates) or reflected. If it is reflected, the angle makes a difference, so smooth shiny surfaces that act like mirrors cause different effects from the materials that present a matte finish or are curved or angled. As the spacecraft rotates to keep GRaND pointed at the ground below, different parts of the ship are presented to the Sun, so the force from the light changes, and the orbit is constantly subjected to a variable disturbance.
Dawn itself adds to the complexity of its orbital path. The spacecraft carries reaction wheels, which are spun to help it control its orientation. These devices gradually spin faster, so every few days they need to be slowed down. That is accomplished by firing the small reaction control system thrusters during windows specified by mission controllers. In addition to the thrusters providing the needed torque on the craft to reduce the wheels' speeds, they impart a force that changes the orbit slightly.
The physical principles underlying all these phenomena that perturb Dawn's orbit are understood with exceptional clarity. Although the values of the myriad parameters involved are ascertained quite accurately, they are not known perfectly. As a result, navigators' prediction of the ship's course includes some degree of uncertainty. Even their ability to determine the present orbit is subject to a variety of small errors typical in sensitive physical measurements.
For all of these reasons, the craft's actual orbit departs slightly from the plan, and the deviations tend to grow, albeit gradually. As designers expected, in survey orbit and HAMO, the differences were small enough that they did not affect the complex operations plans. Analysis well before Dawn arrived at Vesta predicted that the discrepancies in LAMO would be large enough that occasional adjustments of the orbit would be necessary. Therefore, mission controllers scheduled a window every week (on Saturdays, as it turned out) to use the ion propulsion system to fine-tune the spacecraft's trajectory, bringing it back to the intended orbit. These are known as "orbit maintenance maneuvers," and succumbing to instincts developed during their long evolutionary history, engineers refer to them by an acronym: OMM. (As the common thread among team members is their technical training and passion for the exploration of the cosmos, and not Buddhism, the term is spoken by naming the letters, not pronouncing it as a means of achieving inner peace. Instead, it may be thought of as a means of achieving orbital tranquility and harmony.)
The LAMO phase began on December 12, and OMMs were performed on December 17 and 24. In contrast to the long periods of thrusting required with ion propulsion for other parts of the mission, the corrections needed were so small that each OMM needed less than 15 minutes. The whisper-like thrust changed the spacecraft's speed by less than five centimeters per second (one-tenth of a mph). But that was enough to nudge Dawn back to the planned orbit.
The ship was so close to the designated course that the OMMs for December 31 and even January 7 have already been canceled. Not executing the OMMs allows the probe to spend more time collecting neutrons and gamma rays from Vesta. The operations team productively uses the time saved in designing, checking, and transmitting the OMM commands to do other work to ensure LAMO proceeds smoothly and productively.
In the last log we discussed the complicated and dynamic spiral descent from HAMO to LAMO, which was still in progress. The flight required not only reducing the altitude from 680 kilometers (420 miles) to 210 kilometers (130 miles) but also twisting the plane of Dawn's orbit around Vesta. As with all orbiting bodies, whether around Vesta, Earth, or the Sun, the lower the orbital altitude, the shorter the orbital period. Vesta's gravitational grip strengthened as Dawn closed in, forcing the spacecraft to make faster loops around it. This meant that as the probe performed the intricate choreography to align its ion thruster with the changing direction needed to alter its orbit, it had to pirouette faster.
When engineers command Dawn to rotate, they usually instruct it to use the same stately speed as the minute hand on a clock. The spacecraft may have to move a little faster, however, as it pivots to keep its solar arrays pointed at the Sun while accomplishing the required turn. Sometimes it knows that at the end of a turn, it will have to initiate another turn. For example, it may rotate to the orientation required to begin a session of ion thrusting. But while it is thrusting and curving around its orbit, it generally needs to steer the thruster to execute the maneuver. As a result, the robot may choose to turn at a slightly different rate from what its human team members command in order to make a smooth transition from the first turn to the second.
On December 3, when preparing for one of the final thrust segments required to reach LAMO, the combination of all these factors caused the spacecraft to rotate faster than usual. That led to a temporary discrepancy between where it was pointed and where it expected to be pointed during the turn. When protective software detected the inconsistency, it interrupted the ongoing activities and put the spacecraft into safe mode.
When the safe mode signal was received by the Deep Space Network, the operations team responded with its usual calm and skill. They quickly determined that Dawn was fully healthy, diagnosed the cause of the safing, and began guiding the spacecraft back to its normal operational configuration. In addition, they devised a new flight profile that would compensate for the thrusting that was not completed. The team also determined how to prevent the same problem from recurring for subsequent maneuvers. While doing all this work, they were putting the finishing touches on the first LAMO science observation sequences. Controllers managed to complete everything flawlessly and even kept the mission on schedule, allowing LAMO to commence on December 12.
The general plan for Dawn's three-month approach plus one year in orbit around Vesta was described in logs in 2010.The time was apportioned among the different science phases and the transfers between science orbits to ensure a comprehensive and balanced exploration of this mysterious and fascinating world. Fully appreciating that in such an exceedingly ambitious undertaking, some unexpected problems are inevitable, mission planners worked hard to devise an itinerary that left 40 days uncommitted. Their strategy was that as they recovered from anomalies, they would draw from that time and still not have to compromise any of their carefully designed activities. They also planned that any unspent margin would be used to extend LAMO.
To the great delight (and, to be honest, surprise) of all, not one day of the 40-day reserve has been needed. Although there have indeed been unanticipated difficulties, from the beginning of approach on May 3 to this point, the team has been able to resolve all of them without having to withdraw from that account. This is remarkable considering that Dawn is the first visitor from Earth to Vesta, with its many unknown physical properties. This expedition is the first ever in which humankind has sent a spacecraft to orbit such a massive body without first conducting a reconnaissance with a flyby spacecraft. Dawn has maintained a rapid pace of scrutinizing its enigmatic destination. Performing all of this so successfully without needing to use even a little of the spare time they provided for themselves was considered quite unlikely. And yet the entire 40 days remain available.
More ambitious operations lie ahead, with the rest of LAMO, the spiral ascent to HAMO2, HAMO2 itself, and the escape in July to begin the long interplanetary cruise to reach Ceres on schedule in February, 2015. We will see in 2012 that each of these phases includes new challenges, and it is certain new problems will arise. Nevertheless, all 40 days are being used to extend LAMO. Therefore, the indomitable explorer will remain at this low altitude through the end of March, continuing to tease out secrets about the dawn of the solar system and revealing more startling and thrilling discoveries on behalf of everyone on distant Earth who yearns to reach out into the vastness of space.
awn is 210 kilometers (130 miles) from Vesta. It is also 2.79 AU (418 million kilometers or 260 million miles) from Earth, or 1045 times as far as the Moon and 2.84 times as far as the Sun today. Radio signals, traveling at the universal limit of the speed of light, take 46 minutes to make the round trip.
Dr. Marc D. Rayman 8:00 p.m. PST December 30, 2011 | 0.834172 | 3.955063 |
An imprint left on ancient cosmic light that was attributed to ripples in spacetime – and hailed by some as the discovery of the century – may have been caused by ashes from an exploding star.
In the most extreme scenario, the finding could suggest that what looked like a groundbreaking result was only a false alarm. Another possibility is that the stellar ashes could help bring the result in line with other cosmic observations. We should know which it is later this year, when researchers report new results from the European Space Agency’s Planck satellite.
The waves were said to be the “smoking gun” evidence for the theory of inflation, which suggests that space expanded faster than the speed of light in the first moments after the universe’s birth. The announcement sent shock waves through the physics world. “I was so excited,” recalls Philipp Mertsch of Stanford University in California.
But soon it dawned on him that his own research on galactic dust might put a damper on the result. That is because BICEP2 identified the waves based on how they appeared to polarise, or align, the electromagnetic fields of photons they came into contact with in the infant universe.
Those photons, which have been travelling through space ever since, appear in every direction in the sky as the cosmic microwave background (CMB) radiation. But other things apart from gravitational waves, such as dust, can emit polarised photons.
To minimise the chances of this effect causing a false signal, the BICEP 2 team pointed their telescope at a patch of sky far away from the Milky Way’s dusty disc. Then they used models of the dust in that part of the sky to estimate its effect on the polarisation. They found that this could account for no more than about 20 per cent of the signal that they attributed to gravitational waves last month.
But Mertsch says the models they used didn’t account for dust shells produced as the expanding remnants of supernovae slam into surrounding gas and dust. Magnetic field lines threading through those shells should get compressed and aligned, causing some of the material to line up as well. If the aligned dust contains iron, the particles’ slight vibrations due to their own heat would produce polarised microwave radiation, says Mertsch.
A handful of nearby dust shells can be seen by radio telescopes, appearing as giant loops looming above the Milky Way’s galactic disc. Mertsch and his colleagues, led by Hao Liu at the University of Copenhagen in Denmark, plotted the positions of these loops. They found that one “goes right through the BICEP field”, Mertsch says. This plot shows the patch of the sky that BICEP2 observed (multicolored patch) and the giant loops detected by radio telescopes (blue lines).
The effect of this finding on the BICEP2 result is not clear, because no thorough measurements have yet been made of how much polarised light the dust in our galaxy produces. But David Spergel of Princeton University says that if you take the dust into account, along with emissions from charged particles in the galaxy – which he says the BICEP2 team probably underestimated – it might make the gravitational wave signal disappear entirely.
“It is important to explore the possibility that the galactic signal could account for all of the signal seen by BICEP,” he says. “Given its importance, the BICEP2 team needs to make a more convincing case.”
Pressure on Planck
Another upshot of the finding could be that dust doesn’t account for all of the polarisation that BICEP2 attributed to gravitational waves – just some of it. That would help bring the BICEP2 result in line with more preliminary measurements taken by the Planck satellite last year, which hinted at weaker ripples than BICEP2 reported.
The BICEP2 team leaders did not respond to requests for comment on the new research, but upcoming observations by Planck should help settle the matter. The Planck team is currently measuring the polarisation of the CMB and is expected to report its findings in October. Unlike BICEP2, Planck observes at a range of different wavelengths. Because emissions from dust vary with wavelength, this should allow researchers to better separate out the contributions to polarised light from dust.
“For sure, this BICEP2 result will put even more pressure on Planck’s next release,” says Fabio Finelli, a Planck team leader at Italy’s National Institute for Astrophysics in Bologna.
Journal reference: arxiv.org/abs/1404.1899
More on these topics: | 0.896906 | 4.116411 |
When astronomers first discovered other planets, they were completely unlike anything we’ve ever found in the Solar System. These first planets were known as “hot jupiters”, because they’re giant planets – even more massive than Jupiter – but they orbit closer to their star than Mercury. Dr. Heather Knutson, a professor at Caltech explains these amazing objects.
“My name is Heather Knutson, and I’m a professor in the planetary science department here at Caltech. I study the properties of extrasolar planets, which are planets that orbit stars other than the sun, so mostly these are our closest exoplanetary neighbors. We’re not talking about planets in other galaxies – we’re mostly talking about planets which are in the same part of our own corner of our galaxy. So these are around some of the closest stars to the sun.”
What is a hot jupiter?
“The planets that I’ve found the most surprising, out of all of the ones I’ve discovered so far, I guess the sort of classic example, is that we’ve see these sorts of giant planets which are very similar to Jupiter, but orbit very much closer in than Mercury is to our sun, so these planets orbit their sun every two or three days and are absolutely getting roasted. We know that they couldn’t have formed there – they had to have formed farther out and migrated in, so what we’re still trying to understand are what are the forces that caused them to migrate in, whereas Jupiter seems to have migrated a little bit but more or less stayed put in our own solar system.”
What do hot jupiters mean for our understanding our own Solar System?
“The implications of these “hot jupiters” as we call them are actually huge for our own solar system, because if you want to know how many potentially habitable earthlike planets are out there, having one of these giant planets just rampage their way though the inner part of the planetary system, and it could toss out your habitable earth and put it into either a much closer orbit or a much further orbit. So knowing how things have moved around will tell you a lot about where you might find interesting planets.”
What is their atmosphere like?
“So, the atmospheres of hot jupiters are very exotic, by solar system standards. They typically have temperatures of a thousand to several thousand Kelvin, so at these temperatures these planets could have clouds of molten rock, for example. They have atmospheric compositions that would seem very exotic to us – they’re actually more similar to the compositions of relatively cool stars, so we have to adapt to describe these planets – we actually use stellar models to describe their atmospheres. We think that they’re also probably also tidally locked, which is very interesting because it means that one side of the planet is getting all of the heat and the other side is sort of in permanent night. And one thing we do is to try and understand the effect that has on the weather patterns on these planets, so you have winds that are pretty good at carrying that around the night side and mixing everything up, or do these planets have these just extreme temperature gradients between the day side and the night side.”
How’d they get there?
“So, we have a couple of theories for how hot jupiters may have ended up in their present day orbits. One theory is, that after they formed, that they were still embedded in the gas disc where they formed, and maybe they interacted with the disc as such that it kind of torqued and pulled them and so that’s kind of an early migration theory. There’s also a late migration theory version where when after the disc had gone away, these planets had interacted with a third body in the system, so maybe you had another distant massive planet or maybe you had a planet that was part of a binary star system, and those three body interactions excited a large orbital eccentricity in the innermost planet, and once it starts coming in closer to the star, the tides start to damp out the eccentricities, so what you end up with is something which is a gas giant planet in a very short period circular orbit.
So that’s kind of a more complicated story, but there are some clues in the data that might be true for at least a subset of the hot jupiters that we study.” | 0.872299 | 3.918694 |
Ripples of Gravity, Flashes of Light: The Dawn of Multi-Messenger Astrophysics
Prof Martin Hendry, University of Glasgow, UK
The first ever direct detection of gravitational waves by the LIGO and Virgo Scientific Collaborations, from the collision of two massive black holes more than a billion light years away, was widely hailed as the biggest scientific breakthrough of the decade and led to the award of the 2017 Nobel Prize for Physics to three senior LIGO scientists and pioneers: Rai Weiss, Kip Thorne and Barry Barish. Since then, LIGO and Virgo have made many more spectacular discoveries – including the first ever joint detection of gravitational waves and light from the same cosmic source: a pair of colliding neutron stars 130 million light years distant. Join LIGO scientist Professor Martin Hendry as he explores the amazing technology behind the detection of gravitational waves, and what their discovery is telling us about some of the biggest unsolved mysteries in physics and astronomy.
Martin Hendry is Professor of Gravitational Astrophysics and Cosmology at the University of Glasgow, where he is currently Head of the School of Physics and Astronomy. He is a senior member of the LIGO Scientific Collaboration (LSC), for which he chairs the LSC Education and Public Outreach Group. Martin is a Fellow of the Royal Society of Edinburgh and the Institute of Physics, and was awarded the MBE for his services to the public understanding of science.
My notes from the talk (if they don’t make sense then it is entirely my fault)
Cosmology is interested in how big the universe is, how it began and why it is expanding
Gravitational wave astronomy is interested in what black holes and neutron stars are, what happens when these collide and why Einstein’s picture of gravity is correct.
Cover Credit: PHILIPPE HALSMAN
Albert Einstein was the editor’s choice for Time magazine person of the 20th century.
Albert Einstein (14 March 1879 – 18 April 1955) was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics). His work is also known for its influence on the philosophy of science. He is best known to the general public for his mass–energy equivalence formula E= mc2, which has been dubbed “the world’s most famous equation”. He received the 1921 Nobel Prize in Physics “for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect”, a pivotal step in the development of quantum theory.
Gravity in Einstein’s universe
Gravity is a property of matter and spacetime.
Simply put, a mass of an object causes the space around it to essentially bend and curve. This is often portrayed as a heavy ball sitting on a rubber sheet, and other smaller balls fall in towards the heavier object because the rubber sheet is warped from the heavy ball’s weight.
You can demonstrate this with a taut rubber sheet and a large and small ball.
Or you can demonstrate this with the above arrangement, pulling down the centre of the cloth instead of using a ball. By pulling the cloth down by different amounts you can mimic objects of different masses.
A 2-dimensional image of how gravity works. Via NASA’s Space Place
In reality, we can’t see curvature of space directly, but we can detect it in the motions of objects. Any object ‘caught’ in another celestial body’s gravity is affected because the space it is moving through is curved toward that object.
Gravity waves are ripples in space and time caused by changing gravitational fields.
Artist’s impression a neutron star merger and the gravitational waves it creates. (Credit: NASA/Goddard Space Flight Center)
Simulations of two neutron stars rotating around each other
The most powerful gravitational waves are created when objects move at very high speeds. Some examples of events that could cause a gravitational wave are:
- when a star explodes asymmetrically (called a supernova)
- when two big stars orbit each other
- when two black holes orbit each other and merge
In other words, gravitational waves are produced when very massive objects move very quickly,
The types of objects that create gravitational waves are far away. And sometimes, these events only cause small, weak gravitational waves. The waves are then very weak by the time they reach Earth. This makes gravitational waves hard to detect.
Gravitational waves were first detected 100 years after Einstein’s prediction.
In 2015, scientists detected gravitational waves for the very first time. They used a very sensitive instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory). These first gravitational waves happened when two black holes crashed into one another. The collision happened 1.3 billion years ago. But the ripples didn’t make it to Earth until 2015!
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These can detect a change in the 4 km mirror spacing of less than a ten-thousandth the charge diameter of a proton.
The initial LIGO observatories were funded by the National Science Foundation (NSF) and were conceived, built and are operated by Caltech and MIT. They collected data from 2002 to 2010 but no gravitational waves were detected.
LIGO is the largest and most ambitious project ever funded by the NSF. In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry C. Barish “for decisive contributions to the LIGO detector and the observation of gravitational waves.”
https://en.wikipedia.org/wiki/Rainer_Weiss (bottom left)
Rainer (born September 29, 1932) is an American physicist, known for his contributions in gravitational physics and astrophysics. He is a professor of physics emeritus at MIT and an adjunct professor at LSU. He is best known for inventing the laser interferometric technique which is the basic operation of LIGO. He was Chair of the COBE Science Working Group.
He is a member of Fermilab Holometer experiment, which uses a 40m laser interferometer to measure properties of space and time at quantum scale and provide Planck-precision tests of quantum holographic fluctuation.
https://en.wikipedia.org/wiki/Kip_Thorne (above centre)
Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist and Nobel laureate, known for his contributions in gravitational physics and astrophysics. A longtime friend and colleague of Stephen Hawking and Carl Sagan, he was the Feynman Professor of Theoretical Physics at the California Institute of Technology (Caltech) until 2009 and is one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity. He continues to do scientific research and scientific consulting, most notably for the Christopher Nolan film Interstellar.
https://en.wikipedia.org/wiki/Barry_Barish (above right)
Barry Clark Barish (born January 27, 1936) is an American experimental physicist and Nobel Laureate. He is a Linde Professor of Physics, emeritus at California Institute of Technology. He is a leading expert on gravitational waves.
At Glasgow University, Prof. Sir James Hough was also involved
Sir James Hough OBE FRS FRSE FInstP FRAS (born 6 August 1945) is a British physicist and an international leader in the search for gravitational waves.
Gravitational waves are like ripples spreading out on a pond. By the time they reach the Earth they are very weak. They are an invisible (yet incredibly fast) ripple in space. Gravitational waves travel at the speed of light (300 million metres per second). These waves squeeze and stretch anything in their path as they pass by.
Gravitational waves passing through the Earth have an amplitude of about 10−20m.
LIGO is a km scale interferometer. There are two sites.
LIGO operates two gravitational wave observatories in unison: the LIGO Livingston Observatory (30°33′46.42″N 90°46′27.27″W) in Livingston, Louisiana, and the LIGO Hanford Observatory, on the DOE Hanford Site (46°27′18.52″N 119°24′27.56″W), located near Richland, Washington. These sites are separated by 3,002 kilometres straight line distance through the earth, but 3,030 kilometres over the surface. Since gravitational waves are expected to travel at the speed of light, this distance corresponds to a difference in gravitational-wave arrival times of up to ten milliseconds. Through the use of trilateration, the difference in arrival times helps to determine the source of the wave, especially when a third similar instrument like Virgo, located at an even greater distance in Europe, is added.
Each observatory supports an L-shaped ultra-high vacuum system, measuring 4 kilometres on each side. Up to five interferometers can be set up in each vacuum system.
The LIGO Livingston Observatory houses one laser interferometer in the primary configuration. This interferometer was successfully upgraded in 2004 with an active vibration isolation system based on hydraulic actuators providing a factor of 10 isolation in the 0.1–5 Hz band. Seismic vibration in this band is chiefly due to microseismic waves and anthropogenic sources (traffic, logging, etc.).
The LIGO Hanford Observatory houses one interferometer, almost identical to the one at the Livingston Observatory. During the Initial and Enhanced LIGO phases, a half-length interferometer operated in parallel with the main interferometer. For this 2 km interferometer, the Fabry–Pérot arm cavities had the same optical finesse, and, thus, half the storage time as the 4 km interferometers. With half the storage time, the theoretical strain sensitivity was as good as the full-length interferometers above 200 Hz but only half as good at low frequencies. During the same era, Hanford retained its original passive seismic isolation system due to limited geologic activity in Southeastern Washington.
Most Precise Ruler Ever Constructed
Animation created by T. Pyle, Caltech/MIT/LIGO Lab
This animation illustrates how the twin observatories of LIGO work. One observatory is in Hanford, Washington, the other in Livingston, Louisiana. Each houses a large-scale interferometer, a device that uses the interference of two beams of laser light to make the most precise distance measurements in the world.
The animation begins with a simplified depiction of the LIGO instrument. A laser beam of light is generated and directed toward a beam splitter, which splits it into two separate and equal beams. The light beams then travel perpendicularly to a distant mirror, with each arm of the device being 4 kilometres in length. The mirrors reflect the light back to the beam splitter, repeating this process 200 times.
When gravitational waves pass through this device, they cause the length of the two arms to alternately stretch and squeeze by infinitesimal amounts, tremendously exaggerated here for visibility. This movement causes the light beam that hits the detector to flicker.
The second half of the animation explains the flickering, and this is where light interference comes into play. After the two beams reflect off the mirrors, they meet at the beam splitter, where the light is recombined in a process called interference. Normally, when no gravitational waves are present, the distance between the beam splitter and the mirror is precisely controlled so that the light waves are kept out of phase with each other and cancel each other out. The result is that no light hits the detectors.
But when gravitational waves pass through the system, the distance between the end mirrors and the beam splitter lengthen in one arm and at the same time shorten in the other arm in such a way that the light waves from the two arms go in and out of phase with each other. When the light waves are in phase with each other, they add together constructively and produce a bright beam that illuminates the detectors. When they are out of phase, they cancel each other out and there is no signal. Thus, the gravitational waves from a major cosmic event, like the merger of two black holes, will cause the signal to flicker.
The effects of the gravitational waves on the LIGO instrument have been vastly exaggerated in this video to demonstrate how it works. In reality, the changes in the lengths of the instrument’s arms are only 1/1000th the size of a proton. Other characteristics of LIGO, such as the exquisite stability of its mirrors, also contribute to its ability to precisely measures distances. In fact, LIGO can be thought of as the most precise “ruler” in the world.
LIGO in your hands
Dr Borja Sorazu (University of Glasgow) and project student Matthew Wassell have developed a new portable interactive #STEM #Outreach demonstration: LIGO in your hands. It’s a scale model of Gravitational Wave detectors.
Some key results of our analysis of GW150914, comparing the reconstructed gravitational-wave strain (as seen by H1 at Hanford) with the predictions of the best-matching waveform computed from general relativity, over the three stages of the event: inspiral, merger and ringdown. Also shown are the separation and velocity of the black holes, and how they change as the merger event unfolds. Credit: LIGO.
We can follow the process of the gravitational wave forming.
The first stage of the life of a binary black hole is the inspiral, a gradually shrinking orbit. The first stages of the inspiral take a very long time, as the gravitation waves emitted are very weak when the black holes are distant from each other. In addition to the orbit shrinking due to the emission of gravitational waves, extra angular momentum may be lost due to interactions with other matter present, such as other stars.
As the black holes’ orbit shrinks, the speed increases, and gravitational wave emission increases. When the black holes are close the gravitational waves cause the orbit to shrink rapidly.
The last stable orbit or innermost stable circular orbit (ISCO) is the innermost complete orbit before the transition from inspiral to merger.
An example signal from an inspiral gravitational wave source. [Image: A. Stuver/LIGO]
Inspiral gravitational waves are generated during the end-of-life stage of binary systems where the two objects merge into one. These systems are usually two neutron stars, two black holes, or a neutron star and a black hole whose orbits have degraded to the point that the two masses are about to coalesce. As the two masses rotate around each other, their orbital distances decrease and their speeds increase, much like a spinning figure skater who draws his or her arms in close to their body. This causes the frequency of the gravitational waves to increase until the moment of coalescence. The sound these gravitational waves would produce is a chirp sound (much like when increasing the pitch rapidly on a slide whistle) since the binary system’s orbital frequency is increasing (any increase in frequency corresponds to an increase in pitch). https://www.ligo.org/science/GW-Overview/sounds/chirp40-1300Hz.wav
This is followed by a plunging orbit in which the two black holes meet, followed by the merger. Gravitational-wave emission peaks at this time.
Immediately following the merger, the now single black hole will “ring” – oscillating in shape between a distorted, elongated spheroid and a flattened spheroid. This ringing is damped in the next stage, called the ringdown, by the emission of gravitational waves. The distortions from the spherical shape rapidly reduce until the final stable sphere is present, with a possible slight distortion due to remaining spin.
Why does LIGO need two sites?
This enables the observer to recognise a gravitational wave if both sites “see it”.
Computer simulation of the black hole binary system GW150914 as seen by a nearby observer, during its final inspiral, merge, and ringdown. The starfield behind the black holes is being heavily distorted and appears to rotate and move, due to extreme gravitational lensing, as space-time itself is distorted and dragged around by the rotating black holes.
The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016. Previously, gravitational waves had only been inferred indirectly, via their effect on the timing of pulsars in binary star systems. The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent “ringdown” of the single resulting black hole. The signal was named GW150914 (from “Gravitational Wave” and the date of observation 2015-09-14). It was also the first observation of a binary black hole merger, demonstrating both the existence of binary stellar-mass black hole systems and the fact that such mergers could occur within the current age of the universe.
The initial LIGO observatories were funded by the National Science Foundation (NSF) and were conceived, built and are operated by Caltech and MIT. They collected data from 2002 to 2010 but no gravitational waves were detected.
This was followed by a multi-year shut-down while the detectors were replaced by much improved “Advanced LIGO” versions. Much of the research and development work for the LIGO/aLIGO machines was based on pioneering work for the GEO600 detector at Hannover, Germany. By February 2015, the detectors were brought into engineering mode in both locations.
GEO600 is a gravitational wave detector located near Sarstedt in the South of Hanover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics, Max Planck Institute of Quantum Optics and the Leibniz Universität Hannover, along with University of Glasgow, University of Birmingham and Cardiff University in the United Kingdom, and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC). GEO600 is part of a worldwide network of gravitational wave detectors. This instrument, and its sister interferometric detectors, when operational, are some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of 10−21, about the size of a single atom compared to the distance from the Sun to the Earth. GEO600 is capable of detecting gravitational waves in the frequency range 50 Hz to 1.5 kHz. Construction on the project began in 1995.
By the time the LIGO Laboratory started the first observing run ‘O1’ with the Advanced LIGO detectors in September 2015, the LIGO Scientific Collaboration included more than 900 scientists worldwide.
Simplified diagram of an Advanced LIGO detector (not to scale).
Abbott, B. P. et al. – Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration) Phys. Rev. Lett. 116, 061102 doi:10.1103/PhysRevLett.116.061102
Simplified diagram of an Advanced LIGO detector (not to scale). A gravitational wave propagating orthogonally to the detector plane and linearly polarized parallel to the 4-km optical cavities will have the effect of lengthening one 4-km arm and shortening the other during one half-cycle of the wave; these length changes are reversed during the other half-cycle. The output photodetector records these differential cavity length variations. While a detector’s directional response is maximal for this case, it is still significant for most other angles of incidence or polarizations (gravitational waves propagate freely through the Earth). Inset (a): Location and orientation of the LIGO detectors at Hanford, WA (H1) and Livingston, LA (L1). Inset (b): The instrument noise for each detector near the time of the signal detection; this is an amplitude spectral density, expressed in terms of equivalent gravitational-wave strain amplitude. The sensitivity is limited by photon shot noise at frequencies above 150 Hz, and by a superposition of other noise sources at lower frequencies. Narrow-band features include calibration lines (33–38, 330, and 1080 Hz), vibrational modes of suspension fibres (500 Hz and harmonics), and 60 Hz electric power grid harmonics.
The first observing advanced LIGO run operated at a sensitivity roughly 3 times greater than Initial LIGO, and a much greater sensitivity for larger systems with their peak radiation at lower audio frequencies.
On 11 February 2016, the LIGO and Virgo collaborations announced the first observation of gravitational waves. The signal was named GW150914. The waveform showed up on 14 September 2015, within just two days of when the Advanced LIGO detectors started collecting data after their upgrade. It matched the predictions of general relativity for the inward spiral and merger of a pair of black holes and subsequent ringdown of the resulting single black hole. The observations demonstrated the existence of binary stellar-mass black hole systems and the first observation of a binary black hole merger.
On 15 June 2016, LIGO announced the detection of a second gravitational wave event, recorded on 26 December 2015, at 3:38 UTC. Analysis of the observed signal indicated that the event was caused by the merger of two black holes with masses of 14.2 and 7.5 solar masses, at a distance of 1.4 billion light-years. The signal was named GW151226.
The second observing run (O2) ran from 30 November 2016 to 25 August 2017, with Livingston achieving 15–25% sensitivity improvement over O1, and with Hanford’s sensitivity similar to O1. In this period, LIGO saw several further gravitational wave events: GW170104 in January; GW170608 in June; and five others between July and August 2017. Several of these were also detected by the Virgo Collaboration. Unlike the black hole mergers which are only detectable gravitationally, GW170817 came from the collision of two neutron stars and was also detected electromagnetically by gamma-ray satellites and optical telescopes.
The third run (O3) began on 1 April 2019 and is planned to last one year. Future observing runs will be interleaved with commissioning efforts to further improve the sensitivity. It is aimed to achieve design sensitivity in 2021.
Above left is LIGO Hansford and above right is LIGO Livingston
Noise is a big problem so much of the design of the equipment is to reduce the effect of noise.
Design sensitivity curve
Updated Advanced LIGO noise curve
The above figure shows the effect of the different noise sources for the upgraded LIGO detector
The second observing run of Advanced LIGO, and the first observing run of Advanced Virgo, which joined O2 on the 1st of August, 2017.
The release includes over 150 days of recorded data from each of the two LIGO observatories, as well as 20 days of recorded data from Virgo, making this the largest data set of ‘advanced’ gravitational-wave detectors to date. Observations in O2 include seven binary black hole mergers, as well as the first binary neutron star merger observed in gravitational waves, all recently published in the GWTC-1 catalogue. Along with the strain data, the release contains detailed documentation and links to open-source software tools.
The figure above shows the sensitivity achieved during O2 of the three detectors in the network.
Seismic noise occurs at the low-frequency range
Thermal noise of the mirrors occurs at the middle-frequency range
Photon/quantum noise effect occurs at the high-frequency range
In physics and engineering, the quality factor or Q factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is. It is defined as the ratio of the peak energy stored in the resonator in a cycle of oscillation to the energy lost per radian of the cycle. Q factor is alternatively defined as the ratio of a resonator’s centre frequency to its bandwidth when subject to an oscillating driving force. These two definitions give numerically similar, but not identical, results. Higher Q indicates a lower rate of energy loss and the oscillations die out more slowly. A pendulum suspended from a high-quality bearing, oscillating in air, has a high Q, while a pendulum immersed in oil has a low one. Resonators with high-quality factors have low damping so that they ring or vibrate longer.
By using high-Q materials noise can be reduced.
One of the major obstacles to the detection and study of gravitational waves using ground-based laser interferometers is the effect of seismic noise on instrument sensitivity. Environmental disturbances cause motion of the interferometer optics, coupling as noise in the gravitational wave data output whose magnitude can be much greater than that of an astrophysical signal.
Due to the motion of the mirrors from ground vibrations, earthquakes, wind, ocean waves, and human activities such as vehicle traffic.
To isolate the LIGO detector’s core optics from seismic jitters, multiple layers of springs, actuators, and pendulums counteract vibrations and dissipate seismic noise. Seismic isolation begins with a spring-mounted framework resting on the ground. On it stands the second stage: a double-decker platform, with each deck suspended from springs and other controls. This stage 2 also includes three broadband seismometers and six geophones for monitoring seismic noise.
From the centre of stage 2 hang the mirrors that reflect the lasers used to detect changes in the lengths of the arms of LIGO. The mirrors dangle from the end of a quadruple pendulum, which, as its name implies, hangs in turn from a second pendulum hanging from a third pendulum, all of which are suspended from the second stage platform. Add up all those layers and pendulums, integrate them with computer controls, and you get seven stages of isolation of LIGO’s optics from the Earth’s tremors. That knocks those jitters down by a factor of more than a billion, explained Stanford University’s Brian Lantz, lead scientist for the Advanced LIGO Seismic Isolation subsystem.
Internal Seismic Isolation (ISI)
Made of two stages, and has suspension through stiff blade springs and short pendulum links
Use low noise inertial sensors and provides low-frequency active isolation (0.1 Hz)
Attenuates seismic motion above 10Hz
These also position the optics in the vacuum chambers.
The vibration of each stage is reduced by sensing its motion in 6 degrees of freedom (up/down/left/right/yaw/pitch/roll) and applying forces in feedback loops which reduces motion
Seismic noise, if not corrected, limits sensitivity to below 10Hz
The noise equivalent detector sensitivity is shown in displacement together with identified noise sources that were limiting the sensitivity. The frequency noise was suppressed well and optical shot noise was the dominant contribution in the higher frequency region above 1 kHz. In the lower frequency region below 100 Hz, seismic noise in the vertical direction which couples through the suspension system exceeded direct horizontal seismic noise and had a significant influence on the detector sensitivity.
Reduce seismic noise: Advanced (active) seismic isolation. Seismic wall moved from 40 Hz to ~ 12 Hz.
Reduce seismic and suspension noise: Quadruple pendulum suspensions to filter environmental noise in stages.
Reduce suspension noise: Fused silica fibres, silica welds
Due to the discrete nature of light (composed of photons) and the statistical uncertainty from the “photon counting” that is performed by the photodetectors.
The system is so sensitive that can pick up quantum fluctuations in empty space. A central property of quantum systems is that they can never be completely pinned down. It’s part of Heisenberg’s Uncertainty Principle. This is true even for a vacuum. This means quantum fluctuations appear within the vacuum. As photons of light travel through these fluctuations, they are jostled a bit. This makes the beams of light move slightly out of phase. Imagine a fleet of small boats sailing across a rough sea, and how difficult it would be to keep them together.
A close up of LIGO’s quantum squeezer. Credit: Maggie Tse
But quantum uncertainty is a funny thing. Although aspects of a quantum system will always be uncertain, parts of it can be extremely precise. The catch is that if you make one part more precise another part becomes less precise. For light, this means you can keep the phase of the beam more aligned by making the brightness of the light more uncertain. This is known as squeezed light because you squeeze one uncertainty smaller at the cost of another.
Animation showing a squeezed state of light. Credit: Wikipedia user Geek3
This squeezed state of light is done through an optical parametric oscillator. It’s basically a set of mirrors around a special kind of crystal. When the light passes through the crystal, it minimizes the fluctuations in phase. The fluctuations in amplitude get larger, but it’s the phase that matters most to the LIGO detectors.
With this upgrade, the sensitivity of LIGO should double. This will help astronomers see black hole mergers more clearly. It could also allow LIGO to see new kinds of mergers. Ones that are fainter or farther away than we’ve ever seen before.
Source: New Instrument extends LIGO’s reach, MIT News.
From the microscopic fluctuations of the individual atoms in the mirrors and their suspensions.
Atoms are in continuous motion even at low temperatures.
Reduce test mass thermal noise: Last pendulum stage (test mass) is controlled via electrostatic or photonic forces (no magnets).
Reduce test mass thermal noise: High-Q material (40 kg sapphire).
To handle thermal distortions due to beam heating: advanced mirror materials, coatings, thermal de-lensing compensation (heating mirror at edges)
Fluctuations in the mirror coating are due to mechanical loss in which vibrations result in heat generation, causing thermal fluctuations. The noise from the fluctuations interferes with measuring the gravity waves. For the current systems, the level of noise is acceptable, but it must be reduced significantly for more sensitive detectors.
To reduce the noise in the mirror coating, the researchers replaced the fused silica and tantalum oxide currently used with hafnium oxide and amorphous silicon, respectively. Testing showed the replacements to be 25 times less noisy than the present coatings—enough for use on the Einstein Telescope.
The first fused silica mirror suspensions for the Advanced LIGO gravitational wave detectors have been installed at the LIGO Hanford and Livingston sites. These quadruple pendulums use synthetic fused silica fibres produced using a CO2 laser pulling machine to reduce thermal noise in the final suspension stage. The suspension thermal noise in Advanced LIGO is predicted to be limited by internal damping in the surface layer of the fibres, damping in the weld regions, and the strength of the fibres.
Left: Fused silica pulling machine installed at LIGO Hanford. Right: A typical Advanced LIGO fibre.
Close-up of fused silica glass fibres attached to one of LIGO’s primary optics. The bottom of the photo shows the glass welds binding the fibres to the optic. The fibres taper to 0.4 mm. (Caltech/MIT/LIGO Lab)
Glasgow university commissioned, built and installed the fused silica suspensions
The LIGO test masses are suspended in a four-stage pendulum that uses active and passive elements to isolate the masses from ground vibration. The first three pendulums are suspended with metal chains. The last one uses fused silica fibres to help eliminate thermal noise. Image Credit: Caltech/MIT/LIGO Lab.
LIGO employs a passive/active system to hang the test masses by an assemblage of pendulums. Each pendulum has a different length, and so a different frequency of oscillation, and they are stacked, one below the other, into four stages. The test masses holding the interferometer mirrors are suspended on the lowest level. The setup keeps the test masses stable while allowing them to be in effect free-fall along the axes of the laser beams.
On February 11, 2016, the LIGO Scientific Collaboration and Virgo Collaboration announced the first confirmed observation of gravitational waves from colliding black holes. The gravitational-wave signals were observed by the LIGO’s twin observatories on September 14, 2015. This confirms a key prediction of Einstein’s theory of general relativity and provides the first direct evidence that black holes merge.
The inspiral, merger, ringdown was half the speed of light.
Simulation of GW170104
This animation shows the inspiral and merger of two black holes with masses and spins consistent with the GW170104 observation.
The top part of the movie shows the black hole horizons (surfaces of “no return”). The initial two black holes orbit each other, until they merge and form one larger remnant black hole. The shown black holes are spinning, and angular momentum is exchanged among the two black holes and with the orbit. This results in a quite dramatic change in the orientation of the orbital plane, clearly visible in the movie. Furthermore, the spin-axes of the black holes change, as visible through the coloured patch on each black hole horizon, which indicates the north pole.
The lower part of the movie shows the two distinct gravitational waves (called ‘polarizations’) that the merger is emitting into the direction of the camera. The modulations of the polarizations depend sensitively on the orientation of the orbital plane and thus encode information about the orientation of the orbital plane and its change during the inspiral. Presently, LIGO can only measure one of the polarizations and therefore obtains only limited information about the orientation of the binary. This disadvantage will be remedied with the advent of additional gravitational wave detectors in Italy, Japan and India.
Finally, the slowed-down replay of the merger at the end of the movie makes it possible to observe the distortion of the newly formed remnant black hole, which decays quickly. Furthermore, the remnant black hole is “kicked” by the emitted gravitational waves, and moves upward.
Simulation of the binary black-hole coalescence GW170104
Numerical simulation of a black-hole merger consistent with LIGO’s GW170104 observation. The strength of the gravitational wave is indicated by the elevation of the bands, as well as colour, with blue indicating weak fields and yellow, strong fields. The amplitude of the gravitational wave is rescaled during the simulation to show the signal during the entire animation. The sizes of the black holes are increased by a factor of two. The bottom panel in the video shows the gravitational waveform. Simulation Credit: S. Ossokine/A. Buonanno/T. Dietrich (MPI for Gravitational Physics)/R. Haas (NCSA)/SXS project
Analysis of the signal of GW150914 along with the inferred redshift suggested that it was produced by the merger of two black holes with masses of 35 times and 30 times the mass of the Sun (in the source frame), resulting in a post-merger black hole of 62 solar masses. The mass-energy of the missing 3.0 solar masses was radiated away in the form of gravitational waves. Einstein’s famous formula E = mc2 applies. In this case no light was produced but the energy released is equivalent to 50 times the luminosity of every star in the universe.
In physics, spacetime is any mathematical model which fuses the three dimensions of space and the one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive where and when events occur differently.
Until the 20th century, it was assumed that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was independent of one-dimensional time. However, in 1905, Albert Einstein based his seminal work on special relativity on two postulates:
The laws of physics are invariant (i.e., identical) in all inertial systems (i.e., non-accelerating frames of reference)
The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.
Space-time is unbelievably stiff and the creation of black holes are believed to break this.
Computer simulation showing the warping of space and time around two colliding black holes observed by LIGO on September 14, 2015. LIGO detected gravitational waves generated by this black hole merger—humanity’s first contact with gravitational waves and black-hole collisions. Gravitational waves are ripples in the shape of space and flow of time.
It takes a HUGE amount of stress on space-time to produce an appreciable amount of warp or curvature (‘G’). In fact, it takes objects like the Earth (all 6 trillion trillion kilograms of it) to warp space-time to a level that we’re intimately familiar with.
To produce enough warp to create an object like a black hole – with an extreme, maximal amount of space-time curvature – the universe has to concentrate mass and energy to an extraordinary degree. In other words, an immense amount of stress has to be created. For example, producing an Earth-mass black hole would involve squishing all those kilograms into a region roughly the size of a small coin to generate enough local stress. It’s analogous to how the fine point of a nail concentrates enough force to break wood fibres.
It turns out that space-time is very stiff, very resilient. But it can, and does, yield to stress. That’s fortunate, because without a little bit of warping there’d be no stars or planets, and we’d not be here to celebrate Einstein’s wonderful insights.
How LIGO got the word out about gravitational waves
the relevant hashtags got 70 million aggregate impressions,
The image below shows the signal observed by each LIGO detector. These plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. The signals came from two merging black holes, each about 30 times the mass of our sun, lying 1.3 billion light-years away.
The top two plots show data received at Livingston and Hanford, along with the predicted shapes for the waveform. These predicted waveforms show what two merging black holes should look like according to the equations of Albert Einstein’s general theory of relativity, along with the instrument’s ever-present noise. Time is plotted on the X-axis and strain on the Y-axis. Strain represents the fractional amount by which distances are distorted. As the plots reveal, the LIGO data very closely match Einstein’s predictions.
The final plot compares data from both detectors. The Hanford data have been inverted for comparison, due to the differences in orientation of the detectors at the two sites. The data were also shifted to correct for the travel time of the gravitational-wave signals between Livingston and Hanford (the signal first reached Livingston, and then, travelling at the speed of light, reached Hanford seven-thousandths of a second later). As the plot demonstrates, both detectors witnessed the same event, confirming the detection. (Image Credit: Caltech/MIT/LIGO Lab.)
The image below shows the approximate location of GW150914 on a sky map of the southern hemisphere. The coloured lines represent different probabilities for where the signal originated: the purple line defines the region where the signal is predicted to have come from with a 90 per cent confidence level; the inner yellow line defines the target region at a 10 per cent confidence level. The gravitational waves were produced by a pair of merging black holes located 1.3 billion light-years away.
A small galaxy near our own, called the Large Magellanic Cloud, can be seen as a fuzzy blob underneath the marked area, while an even smaller galaxy, called the Small Magellanic Cloud, is below it.
Researchers were able to home in on the location of the gravitational-wave source using data from the LIGO observatories in Livingston, Louisiana, and Hanford, Washington. The gravitational waves arrived at Livingston 7 milliseconds before arriving at Hanford. This time delay revealed a particular slice of sky, or ring, from which the signal must have arisen. Further analysis of the varying signal strength at both detectors ruled out portions of the ring, leaving the remaining patch shown on this map. (Image credit: LIGO/Axel Mellinger.) Trigonometry was used in the analysis.
The facility was able to pinpoint the location of the event to within a 600 square degree area of the sky. (The full moon takes up about half a degree on the sky.)
LIGO researchers were awarded a Special Breakthrough Prize in Fundamental Physics in 2016. The team that detected gravitational waves shared the $3 million prize.
The first joint catch by LIGO and VIRGO: another black hole merger detected on the 14th August 2017. It was the fourth detection of a merging binary black hole system. Three such events were detected by the twin LIGO detectors previously (first two events in 2015 and the third one in January 2017). It was the first time that such a detection was being confirmed by a third detector. The Virgo detector started collecting data on 1 August 2017, and was soon bestowed with a detection, jointly with LIGO.
The Virgo interferometer is a large interferometer designed to detect gravitational waves predicted by the general theory of relativity. Virgo is a Michelson interferometer that is isolated from external disturbances: its mirrors and instrumentation are suspended and its laser beam operates in a vacuum. The instrument’s two arms are three kilometres long and located in Santo Stefano a Macerata, near the city of Pisa, Italy.
The first detection of gravitational waves by Virgo is known as GW170814, which was announced on 27 September 2017 in a G7 science meeting conference in Turin, Italy.
The figure below shows the localizations of some of the gravitational wave detections; most were made only by the two LIGO antennae, but the two most recent, GW 170814 and GW170817, include VIRGO as well.
On December 1, 2018, the LIGO Scientific Collaboration and the Virgo Collaboration announced the full results of their searches for gravitational-waves from stellar-mass coalescing compact binaries with an advanced detector network. In addition to the six previously announced binary black hole and single binary neutron star detections, this includes four new binary black hole mergers: GW170729, GW170809, GW170818, and GW170823.
Spectrograms and waveforms for the gravitational-wave transient catalogue. The insets of this image below show the gravitational waveform (bottom) and time-frequency spectrogram for each confident detection in the gravitational-wave transient catalogue. The spectrogram colour indicates a measure of signal strength; the increase of signal frequency with time clearly shows the characteristic “chirp” signature of a binary inspiral. The waveforms shown at the bottom of each panel are produced from either a range of models based on Einstein’s theory (orange) or a wavelet decomposition of the observed signal (grey).
LIGO/Virgo Binary-Black-Hole Orrery. A visualization of the merging black holes that LIGO and Virgo have observed so far.
The evidence from gravitational waves shows that relativity really does fit.
Cataclysmic Collision Artist’s illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays that are shot out just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars are also depicted. The clouds glow with visible and other wavelengths of light. Image credit: NSF/LIGO/Sonoma State University/A. Simonnet
GW170817 Press Release
LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars
Discovery marks first cosmic event observed in both gravitational waves and light.
Neutron star merger (Credit: Christopher W. Evans/Georgia Tech)
GW 170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy NGC 4993. The GW was produced by the last minutes of two neutron stars spiralling closer to each other and finally merging, and is the first GW observation which has been confirmed by non-gravitational means. Unlike the five previous GW detections, which were of merging black holes not expected to produce a detectable electromagnetic signal, the aftermath of this merger was also seen by 70 observatories on 7 continents and in space, across the electromagnetic spectrum, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW 170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
The first electromagnetic signal detected was GRB 170817A, a short gamma-ray burst, detected 1.74±0.05 s after the merger time and lasting for about 2 seconds.
GRB 170817A was discovered by the Fermi Gamma-ray Space Telescope, with an automatic alert issued just 14 seconds after the GRB detection. After the LIGO/Virgo circular 40 minutes later, manual processing of data from the INTEGRAL gamma-ray telescope also detected the same GRB. The difference in arrival time between Fermi and INTEGRAL helped to improve the sky localization.
This GRB was relatively faint given the proximity of the host galaxy NGC 4993, possibly due to its jets not being pointed directly toward Earth, but rather at an angle of about 30 degrees to the side.
The Fermi Gamma-ray Space Telescope (FGST), formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts.
Fermi was launched on 11 June 2008 at 16:05 UTC aboard a Delta II 7920-H rocket. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden, becoming the most sensitive gamma-ray telescope on-orbit, succeeding INTEGRAL.
This animation captures phenomena observed over the course of nine days following the neutron star merger known as GW170817, detected on Aug. 17, 2017. They include gravitational waves (pale arcs), a near-light-speed jet that produced gamma rays (magenta), expanding debris from a kilonova that produced ultraviolet (violet), optical and infrared (blue-white to red) emission, and, once the jet directed toward us expanded into our view from Earth, X-rays (blue).
Credit: NASA’s Goddard Space Flight Center/CI Lab
The first sign of the Aug. 17, 2017, neutron star merger was a brief burst of gamma-rays seen by NASA’s Fermi Gamma-ray Space Telescope (top). Shortly after, LIGO scientists reported detecting gravitational waves that arrived 1.7 seconds before the Fermi burst (middle). A short time later, scientists analyzing gamma-ray data from the European Space Agency’s INTEGRAL spacecraft also reported seeing the burst (bottom).
Credit: NASA’s Goddard Space Flight Center, Caltech/MIT/LIGO Lab and ESA
On Aug. 17, 2017, gravitational waves from a neutron star merger produced a signal detected by LIGO. 1.7 seconds later, a brief burst of gamma-rays was seen by NASA’s Fermi Gamma-ray Space Telescope (top). This video contains the actual sound of the LIGO detection.
Credit: NASA’s Goddard Space Flight Center, Caltech/MIT/LIGO Lab
INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a space telescope for observing gamma rays. It was launched by the European Space Agency into Earth orbit in 2002 and is designed to detect some of the most energetic radiation that comes from space. It was the most sensitive gamma-ray observatory in space before NASA’s Fermi was launched in 2008.
INTEGRAL is an ESA mission in cooperation with the Russian Space Agency and NASA. It has had some notable successes, for example in detecting a mysterious ‘iron quasar’. It has also had success in investigating gamma-ray bursts and evidence for black holes.
Multi-messenger Astronomy with Gravitational Waves
Fermi and INTEGRAL could identify 30 possible host galaxies
NGC 4993 (also catalogued as NGC 4994) is a lenticular galaxy located about 140 million light-years away in the constellation Hydra. It was discovered on 26 March 1789 by William Herschel and is a member of the NGC 4993 Group.
NGC 4993 is the site of GW170817, the first astronomical event detected in both electromagnetic and gravitational radiation, the collision of two neutron stars, a discovery given the Breakthrough of the Year award for 2017 by the journal Science. Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts.
About 5000 scientists involved in the investigation of gravitational waves. LIGO has over 1000
GW 170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy NGC 4993. The GW was produced by the last minutes of two neutron stars spiralling closer to each other and finally merging, and is the first GW observation which has been confirmed by non-gravitational means.
The discovery and subsequent observations of GW 170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
The gravitational wave signal, designated GW 170817, had a duration of approximately 100 seconds and showed the characteristics in intensity and frequency expected of the inspiral of two neutron stars. Analysis of the slight variation in arrival time of the GW at the three detector locations (two LIGO and one Virgo) yielded an approximate angular direction to the source. Independently, a short (~2 seconds’ duration) gamma-ray burst, designated GRB 170817A, was detected by the Fermi and INTEGRAL spacecraft beginning 1.7 seconds after the GW merger signal.
An intense observing campaign then took place to search for the expected emission at optical wavelengths. An astronomical transient designated AT 2017gfo (originally, SSS 17a) was found, 11 hours after the gravitational wave signal, in the galaxy NGC 4993 during a search of the region indicated by the GW detection. It was observed by numerous telescopes, from radio to X-ray wavelengths, over the following days and weeks, and was shown to be a fast-moving, rapidly-cooling cloud of neutron-rich material, as expected of debris ejected from a neutron-star merger.
As it is a result of the merger of neutron stars it is believed to be an unknown kilonova transient.
A kilonova (also called a macronova or r-process supernova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge into each other. Kilonovae are thought to emit short gamma-ray bursts and strong electromagnetic radiation due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process.
The neutron star merger event is thought to result in a kilonova, characterized by a short gamma-ray burst followed by a longer optical “afterglow” powered by the radioactive decay of heavy r-process nuclei. Kilonovae are candidates for the production of half the chemical elements heavier than iron in the Universe. [A total of 16,000 times the mass of the Earth in heavy elements is believed to have formed, including approximately 10 Earth masses just of the two elements gold and platinum].
Scientists use two primary methods to measure the Hubble constant. One involves monitoring nearby objects whose properties scientists understand well, such as stellar explosions known as supernovas and pulsating stars known as Cepheid variables, in order to estimate their distances and then deduce the expansion rate of the universe. The other focuses on the cosmic microwave background, the leftover radiation from the Big Bang, and examines how it has changed over time to calculate how quickly the cosmos has expanded.
However, this pair of techniques has yielded two different results for the value of the Hubble constant. Data from the cosmic microwave background suggests the universe is currently expanding at a rate of about 67 kilometres per second per 3.26 million light-years, while data from supernovas and Cepheids in the nearby universe suggests a rate of about 73 km per second per 3.26 million light-years.
This discrepancy suggests that the standard cosmological model — scientists’ understanding of the universe’s structure and history— could be wrong. Resolving this debate, known as the Hubble constant conflict, could shed light on the evolution and ultimate fate of the cosmos.
In the new study, physicists suggest that future data from the ripples in the fabric of space and time known as gravitational waves might help break this deadlock.
As mentioned earlier scientists, in 2017, detected gravitational waves from colliding neutron stars, remnants of stars that perished in catastrophic explosions known as supernovas.
Neutron stars emit visible light, and so do their collisions. The gravitational waves from these mergers, dubbed “standard sirens,” will help scientists pinpoint their distance from Earth, while the light from these collisions will help determine the speed at which they were moving relative to Earth. Researchers can then use both these sets of data to calculate the Hubble constant.
However, that estimate depends on how often neutron-star collisions occur. There is considerable uncertainty in the rate of neutron star mergers as so far we have only seen one.
On 1 April 2019, the start of the third observation run was announced with a circular published in the public alerts tracker. The first O3/2019 binary black hole detection alert was broadcast on 8 April 2019. A significant percentage of O3 candidate events detected by LIGO were accompanied by corresponding triggers at Virgo. False alarm rates were mixed, with more than half of events assigned false alarm rates greater than 1 per 20 years, contingent on the presence of glitches around signal, foreground electromagnetic instability, seismic activity, and operational status of any one of the three LIGO-Virgo instruments. For instance, events S190421ar and S190425z weren’t detected by Virgo and LIGO’s Hanford site, respectively.
The detection rates and signal qualities of gravitational waves will improve when the Kamioka Gravitational Wave Detector (KAGRA) in Japan becomes operational.
The Kamioka Gravitational Wave Detector (KAGRA), formerly the Large Scale Cryogenic Gravitational Wave Telescope (LCGT), is a project of the gravitational wave studies group at the Institute for Cosmic Ray Research (ICRR) of the University of Tokyo. It will be the world’s first gravitational wave observatory in Asia, and that is built underground, and whose detector uses cryogenic mirrors. The design calls for an operational sensitivity equal to, or greater than LIGO
A proposal for a gravitational-wave detector made of two space-based atomic clocks has been unveiled by physicists in the US. The scheme involves placing two atomic clocks in different locations around the Sun and using them to measure tiny shifts in the frequency of a laser beam shone from one clock to the other. The designers claim that the detector will complement the LISA space-based gravitational-wave detector, which is expected to launch in 2034.
ESA’s potential future mission, LISA, will detect and observe gravitational waves that are emitted during the most powerful events in the universe. LISA will detect gravitational radiation from astronomical sources, observing galaxies far back in time and testing the fundamental theories of gravitation.
41 candidate O3 events – its raining gravitational waves
The document is intended for both professional astronomers and science enthusiasts who are interested in receiving alerts and real-time data products related to gravitational-wave (GW) events.
Allows you to keep track of the latest gravitational wave alerts.
This artist’s depiction illustrates a black hole devouring a neutron star. As the neutron star circles the black hole, the black hole’s immense gravity shreds it to pieces, a phenomenon called tidal disruption.
Photograph by illustration by Dana Berry, NASA
Some 900 million years ago, a black hole released a terrible burp that echoed through the cosmos. On August 14 2019, the resulting ripples in the fabric of spacetime passed through Earth—giving us the best evidence yet of a never-before-seen type of cosmic collision that could offer new insights on how the universe works.
The detection, called S190814bv, was likely triggered by the merging of a black hole and a neutron star, the ultra-dense leftovers of an exploded star. Though astronomers have long expected such binary systems to exist, they’ve never been seen by telescopes scanning the heavens for different wavelengths of light.
However, astronomers also expect such systems to create ripples known as gravitational waves if and when the black hole and neutron star merge. These spacetime ripples were predicted more than a century ago by Einstein’s general theory of relativity, which suggested that the collision of two extremely massive bodies would cause the very fabric of the universe to wrinkle.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) – India is a planned advanced gravitational-wave observatory to be located in India as part of the worldwide network, whose concept proposal is now under active consideration in India and the USA. LIGO-India is envisaged as a collaborative project between a consortium of Indian research institutions and the LIGO Laboratory in the USA, along with its international partners.
LIGO-India received the Indian Government’s in-principle approval in February 2016. Since then the project reached several milestones towards selecting and acquiring a site and building the observatory.
Sapphire mirror for the KAGRA gravitational wave detector
KAGRA, the Japanese interferometric gravitational wave detector currently under construction, will employ sapphire test masses for its cryogenic operation. Sapphire has an advantage in its higher thermal conductivity near the operating temperature 20 K compared to fused silica used in other gravitational wave detectors, but there are some uncertain properties for the application such as hardness, optical absorption, and birefringence. Test polish of sapphire substrate has especially proven that specifications on the surface are sufficiently met. Recent measurements of absorption and inhomogeneity of the refractive index of the sapphire substrate indicate that the other properties are also acceptable to use sapphire crystal as test masses.
Gravitational-wave observatory LIGO set to double its detecting power
A planned US$35-million upgrade could enable LIGO to spot one black-hole merger per hour by the mid-2020s.
New instrument extends LIGO’s reach
Technology “squeezes” out quantum noise so more gravitational wave signals can be detected.
The major improvement for ALIGO+ — requiring the 300-metre pipes — will introduce ‘frequency-dependent squeezing’. This will enable the interferometers to reduce both the pressure on the mirrors and the photon fluctuations at the same time. Other improvements will include new mirrors with state-of-the-art coatings, which is expected to reduce thermal noise fourfold.
Improvements of the ground-based detectors would increase the sensitivity by 10 times and the event rate by 1000 times.
Einstein Telescope (ET) or Einstein Observatory, is a proposed third-generation ground-based gravitational wave detector, currently under study by some institutions in the European Union. It will be able to test Einstein’s general theory of relativity in strong field conditions and realize precision gravitational wave astronomy.
The ET is a design study project supported by the European Commission under the Framework Programme 7 (FP7). It concerns the study and the conceptual design for a new research infrastructure in the emergent field of gravitational-wave astronomy.
Gravitational-wave detectors may benefit from an alternative coating material that is less noisy at low temperatures than currently used materials.
To detect the faint “chirps” of gravitational waves, researchers at the upgraded facilities of Advanced LIGO and Virgo must minimize noise as much as possible. One of the most troublesome sources of noise in these detectors is the thermal fluctuations in the mirror coatings. Iain Martin from the University of Glasgow, UK, and colleagues now propose a new coating material that could help reduce thermal noise at temperatures of around 10 K, where the next generation of gravitational-wave detectors plan to operate.
Gravitational-wave detectors use kilometre-long interferometer arms formed by laser beams bouncing off highly reflective mirrors. To maximize reflection, the mirrors are coated with alternating layers of materials that have high and low refractive indices. The coatings create an interference effect that reduces light absorption to less than 5 parts per million.
In current detectors, the coatings are made of doped tantala (Ta2O5) and silica (SiO2). But both of these materials exhibit strong mechanical losses—which means vibrations are readily converted to heat and thermal fluctuations—at the low temperatures planned for next-generation detectors, such as the Einstein Telescope.
Martin and colleagues propose replacing the silica with a low-index material called hafnia (HfO2). In tests, the team placed thin films of hafnia (doped with silica) on a cantilever and measured the material’s mechanical loss to be a factor of 2 lower than that of pure silica. They also calculated the expected performance of a coating design consisting mainly of hafnia and amorphous silicon (a tantala replacement). The researchers found that this model coating would be 25 times less noisy than current LIGO coatings for low-frequency (10-Hz) gravitational waves, the detection of which is one of the design goals for the Einstein Telescope.
Summaries of LSC scientific publications https://www.ligo.org/science/outreach.php
Gravitational Wave Open Science Center https://www.gw-openscience.org/about/
Like electromagnetic waves, gravitational waves travel at the speed of light. And like the electromagnetic spectrum, the gravitational wave spectrum is extremely broad, with the different parts classified according to frequency. In general, gravitational wave frequencies are much lower than those of the electromagnetic spectrum (a few thousand hertz at most, compared to some 1016 to 1019 Hz for X-rays). Consequently, they have much larger wavelengths – ranging from hundreds of kilometres to potentially the span of the Universe.
Gravitational waves offer a unique view into the very early universe because they can allow us to see “behind” the Cosmic Microwave Background Radiation (CMBR). The CMBR gives us an image of the universe about 380,000 years after the beginning of the universe, the ‘Big Bang’. This is because, before that time, the universe was filled with hot ionized gas (meaning the electrons and nuclei were separate, just free electrons flying around), so photons of light would be scattered wildly by these free electrons, rather like what happens on a foggy day, so they don’t carry much information about their original source. Because the universe had been expanding since the beginning, it was cooling, and at around the 380,000-year mark, the universe became cool enough that the gas stopped being ionized: the free electrons combined with protons to form neutral hydrogen (we call this recombination), which is much less effective at scattering photons — in other words the fog clears! For us, this marks the beginning of the period when photons actually can free-stream directly towards us from the early universe, with minimal scattering, so they can carry information about their origins.
Image credit: Chris Henze, NASA. Advanced Supercomputing Division, NASA Ames Research Center
2-nd ISSI Workshop on Clocks, Spacetime Metrology and Geodesy (Bern, Switzerland)
The horizontal axis shows the frequency (and the wave period, which is the inverse of frequency) on a logarithmic scale, with the colours representing the corresponding wavelengths (red = longer, blue = shorter). The detectors shown are those existing or planned, while the sources are those known to exist and expected to produce detectable gravitational waves.
On the other hand, gravitational radiation does not care about this epoch of recombination, because atoms and molecules of gas — whether ionized or not — have minimal effect on gravitational waves. This means that gravitational waves created before recombination can still stream right towards us without being disturbed along the way, and so could in principle tell us something about that very early phase in the history of the cosmos. The LIGO detectors may not be sensitive to these ‘primordial’ gravitational waves, but there are other ways we can search for their signature — e.g. by looking for polarized light in the CMBR.
Dark matter and dark energy have had a big role in the history of the universe expanding (in fact we think dark energy is now causing that expansion to speed up!) and in the formation of galaxies and clusters of galaxies. But we don’t expect dark matter to exist in nearly dense enough ‘clumps’ to produce gravitational waves that could be detected by LIGO.
In the future, however, astronomers hope to use gravitational-wave sources such as compact binary coalescence to map out the cosmos, completely independently of the methods available right now — using e.g. the CMBR or distant supernovae. So it’s possible that future gravitational wave observations could help us to better understand the effects of dark matter and dark energy on the expansion of the universe.
At the moment there is too much noise for the lower frequencies at the moment.
LISA Pathfinder, formerly Small Missions for Advanced Research in Technology-2 (SMART-2), was an ESA spacecraft that was launched on 3 December 2015 onboard Vega flight VV06. The mission tested technologies needed for the Laser Interferometer Space Antenna (LISA), an ESA gravitational wave observatory planned to be launched in 2034. The scientific phase started on 8 March 2016 and lasted almost sixteen months. In April 2016 ESA announced that LISA Pathfinder demonstrated that the LISA mission is feasible.
It paved the way for future missions by testing in flight the very concept of gravitational wave detection. It put two test masses in a near-perfect gravitational free-fall and control and measured their motion with unprecedented accuracy. LISA Pathfinder used the latest technology to minimise the extra forces on the test masses, took measurements. The inertial sensors, the laser metrology system, the drag-free control system and an ultra-precise micro-propulsion system made this a highly unusual mission. LISA Pathfinder was an ESA mission, which also carries a NASA payload.
It didn’t detect gravitational waves but the noise level could be controlled. It could see an inspiral before a merger (allowed preparation for the merger).
The Chinese are developing a space gravitational wave detector.
The TianQin Project is a proposed space-borne gravitational-wave observatory (gravitational-wave detector) consisting of three spacecrafts in Earth orbit.
Inflationary theory and pulsar timing investigations of primordial black holes and gravitational waves
A pulsar timing array (PTA) is a set of pulsars which is analysed to search for correlated signatures in the pulse arrival times. There are many applications for pulsar timing arrays. The most well-known is to use an array of millisecond pulsars to detect and analyse gravitational waves. Such a detection would result from a detailed investigation of the correlation between arrival times of pulses emitted by the millisecond pulsars as a function of the pulsars’ angular separations.
Gravitational waves are ripples in space-time, predicted by Einstein’s theory of general relativity, which stretch and compress spacetime. As pulsars emit pulses with such amazing regularity, organisations such as the European Pulsar Timing Array can use pulsars as extremely accurate clocks, at distances of light-years from the Earth. By comparing the measured pulse arrival times to the expected arrival times, the distortion of space caused by a passing gravitational wave should be detectable as a deviation from the timing model, correlated across all pulsars. Pulsar timing arrays are sensitive to extremely low-frequency gravitational radiation generated by supermassive black hole binaries, cosmic strings, and the inflationary era.
Questions at the end of the talk
1) What can we learn from the spin and mass of a black hole?
Once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, charge, and angular momentum; the black hole is otherwise featureless.
These properties are special because they are visible from outside a black hole. For example, a charged black hole repels other like charges just like any other charged object. Similarly, the total mass inside a sphere containing a black hole can be found by using a gravitational analogue.
If the spins of supermassive black holes are as high as some have found then these black holes are likely to have formed from rare, major mergers between colliding galaxies, in which a large quantity of material falls into the central black hole from one direction. If the spins are lower then the black holes may have formed from many minor mergers, with bite-sized lumps of material coming from various directions. The distribution of black hole spins could therefore inform researchers about the history of galactic evolution, particularly if astronomers can eventually chart the change in spin over cosmic time by looking at ever-more-distant black holes.
The greater the mass of black holes the more likely their behaviour could deviate from the three properties. These potential differences could help describe some mysteries of the Universe, like dark matter. At the moment there is no evidence of deviation.
The behaviour of black holes is evidence that Albert Einstein’s theory of general relativity holds true.
2) Can the work measure Newton’s gravitational constant, G more accurately?
No because there are too many uncertainties in instruments, distances etc.
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are “close enough” (within about a thousand parsecs) to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances and methods that work at larger distances. Several methods rely on a standard candle, which is an astronomical object that has a known luminosity.
The ladder analogy arises because no single technique can measure distances at all ranges encountered in astronomy. Instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung.
Gravitational waves originating from the inspiral phase of compact binary systems, such as neutron stars or black holes, have the useful property that energy emitted as gravitational radiation comes exclusively from the orbital energy of the pair, and the resultant shrinking of their orbits is directly observable as an increase in the frequency of the emitted gravitational waves. By observing the waveform, the chirp mass can be computed and thence the power (rate of energy emission) of the gravitational waves. Thus, such a gravitational wave source is a standard siren of known loudness.
In astrophysics, the chirp mass of a compact binary system determines the leading-order orbital evolution of the system as a result of energy loss from emitting gravitational waves. Because the gravitational wave frequency is determined by orbital frequency, the chirp mass also determines the frequency evolution of the gravitational wave signal emitted during a binary’s inspiral phase. In gravitational wave data analysis, it is easier to measure the chirp mass than the two-component masses alone.
Just as with standard candles, given the emitted and received amplitudes, the inverse-square law determines the distance to the source.
A standard candle is an astronomical object that has a known absolute magnitude. They are extremely important to astronomers since by measuring the apparent magnitude of the object we can determine its distance.
The most commonly used standard candles in astronomy are Cepheid Variable stars and RR Lyrae stars. In both cases, the absolute magnitude of the star can be determined from its variability period.
Discovery of Accelerating Universe Wins 2011 Nobel Prize in Physics
Dark energy wins out in the end: Three U.S. scientists have been honoured for their observations that type Ia supernovae indicate that the expansion of the universe is accelerating
3) Can the work on gravitational waves indicate dark matter?
Dark matter is believed to be five times as prevalent as visible matter. Its gravitational effects are seen throughout the universe. Scientists think they have yet to definitively see gravitational waves caused by dark matter, but they can think of numerous ways this might happen.
Scientists have seen the gravitational effects of dark matter, so they know it must be there—or at least, something must be going on to cause those effects. But so far, they’ve never directly detected a dark matter particle, so they’re not sure exactly what dark matter is like.
4) Could dark matter be primordial black holes
One idea is that some of the dark matter could actually be primordial black holes.
Imagine the universe as an infinitely large petri dish. In this scenario, the Big Bang is the point where matter-bacteria begins to grow. That point quickly expands, moving outward to encompass more and more of the petri dish. If that growth is slightly uneven, certain areas will become more densely inhabited by matter than others.
These pockets of dense matter—mostly photons at this point in the universe—might have collapsed under their own gravity and formed early black holes.
By using gravitational waves to learn about the properties of black holes, LIGO might be able to prove or constrain this dark matter theory.
Unlike normal black holes, primordial black holes don’t have a minimum mass threshold they need to reach in order to form. If LIGO were to see a black hole less massive than the sun, for example, it might be a primordial black hole.
Even if primordial black holes do exist, it’s doubtful that they account for all of the dark matter in the universe. Still, finding proof of primordial black holes would expand our fundamental understanding of dark matter and how the universe began.
5) Has LIGO seen dark matter?
The basics of gravitational wave theory
The basic physics of the binary black hole merger GW150914 https://arxiv.org/ftp/arxiv/papers/1608/1608.01940.pdf
Observational data indicates that the bodies were orbiting each other (roughly Keplerian dynamics) up to at least an orbital angular frequency.
In astronomy, Kepler’s laws of planetary motion are three scientific laws describing the motion of planets around the Sun, published by Johannes Kepler between 1609 and 1619. These improved the heliocentric theory of Nicolaus Copernicus, replacing its circular orbits with epicycles with elliptical trajectories, and explaining how planetary velocities vary. The laws state that:
The orbit of a planet is an ellipse with the Sun at one of the two foci (the orbit of one black hole is an ellipse with another black hole at one of the two foci).
A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time (A line segment joining the two black holes sweeps out equal areas during equal areas of time).
The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit (The square of the orbital period of a black hole is directly proportional to the cube of the semi-major axis of its orbit).
The discovery of gravitational waves is evidence that there is conservation of mass and energy.
Mass was lost when the two black holes collapsed. One of the black holes was 36 times the mass of our sun and the other was 29 times its mass. When they collapsed, the resulting black hole was only 62 solar masses. That means that a mass three times the mass of the sun was lost!
That mass was turned into energy, which caused the ripples in spacetime – gravitational waves – that LIGO detected 1.3 billion years later.
Gravitational-wave items for sale | 0.822833 | 3.740355 |
Study of material surrounding distant stars shows Earth’s ingredients ‘pretty normal’
The Earth’s building blocks seem to be built from ‘pretty normal’ ingredients, according to researchers working with the world’s most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth.
This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere.
“Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth”, said researcher Dr Siyi Xu of the Gemini Observatory in Hawaii, who was presenting the work at the Goldschmidt conference in Boston.
The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system.
“It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves” said Siyi Xu. “So we needed to look at other methods”.
Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense – it is anticipated that our Sun will become a white dwarf in around 5 billion years.
Dr Xu continued, “White dwarfs’ atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn. As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star’s spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected”.
The team took measurements using spectrographs on the Keck telescope in Hawaii, the world’s largest optical and infrared telescope, and on the Hubble Space Telescope.
Siyi Xu continued, “In this study, we have focused on the sample of white dwarfs with dust disks. We have been able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. We may also have found water in one of the systems, but we have not yet quantified it: it’s likely that there will be a lot of water in some of these worlds. For example, we’ve previously identified one star system, 170 light years away in the constellation Boötes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley’s Comet. In general though, their composition looks very similar to bulk Earth.
This would mean that the chemical elements, the building blocks of earth are common in other planetary systems. From what we can see, in terms of the presence and proportion of these elements, we’re normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy”.
Dr Xu continued “This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. We hope to determine the chemical compositions of extrasolar planetary material to a much higher precision”
Professor Sara Seager, Professor of Planetary Science at Massachusetts Institute of Technology, is also the deputy science director of the recently-launched TESS (Transiting Exoplanet Survey Satellite) mission, which will search for exoplanets. She said:
“It’s astonishing to me that the best way to study exoplanet interiors is by planets ripped apart and absorbed by their white dwarf host star. It is great to see progress in this research area and to have solid evidence that planets with Earth-like compositions are common–fueling our confidence that an Earth-like planet around a very nearby normal star is out there waiting to be found”.
Professor Seager was not involved in this research, this is an independent comment. | 0.939437 | 3.859603 |
Sam has always loved astronomy and the Night Sky, and helped with the Astronomy Club at his Junior School. When he left the teachers and parents gave him his own astronomical telescope as their way of saying “thank you” to him for all his work with the Astronomy Club.
He uses it a lot. He has not yet made any new discoveries but he lives in hope: most comets are first detected by amateur astronomers and named after them (these days professional astronomers are looking for things far further away from the Earth and the Sun than comets) so perhaps one day there will be Sam’s Comet! But owning his own telescope does not stop him from looking at and telling all his friends about what you can see in the Night Sky without one - after all the telescope was not invented until 1608 so for at least six thousand years before that astronomers had had to manage without, and did so very well indeed. Even the great Nicolaus Copernicus (1473 - 1543) did not have a telescope!
Often on a fine evening Sam and his friends sit outside and watch the sun set and the stars come out. They sometimes play a game, particularly if there is someone in the group who has not played it before.
They watch the Sun set, and then wait for the first “star” to appear - this could be a fixed star or a planet (these terms are explained later) but in this game it does not matter which. They might have to wait several minutes. The first person to see one shouts “star” and points to it. They all count the number of stars they can see, here it is just one, and then count them again, and then wait for the next one. Each time someone sees a new star they all count the number of stars they can see, and then count them again. This is easy - up to seven! Then they find that in the time it takes them to count the stars another one has appeared! On a clear night by the time the sky is fully dark Sam and his friends can see more than four thousand stars, far too many to count. Sam is very sad that today so many children live in towns and never see the Night Sky in all its glory because of all the street lights.
This Game is best played at the end of August, on an evening when there is no Moon in the sky. During the middle of the summer the sky is not really dark enough to see all the stars until well past Sam’s bedtime, and after the end of August the evenings are getting a little cold for sitting out of doors for a long time.
Sam and his friends like watching the way the planets move across the sky against the background of the fixed stars, but with only five planets to look at but more than four thousand stars this is not easy! One day when it is too wet to do any real star-watching Sam uses his iPad to explain how it is done.
He shows them a (made-up) map of a part of the sky showing twenty stars and one planet.
He then shows them the same part of the sky as it appears a few weeks later.
He asks them to explain how the planet has moved against the background of the stars.
They all have different ideas, but none of them work. Then he says ” Dont’t look at the stars, look only at the patterns they make” and suddenly it is easy.
The stars have kept the same positions but they have rotated, the Trapezium has moved into sight and the Parallelogram has moved out of sight, and the planet has moved from the Square to the Kite!
The Ancient Astronomers did exactly the same: they looked for the patterns the stars made: these patterns are called constellations. Orion, Pegasus, Aries, Scorpio, Cancer, Leo, Ursa Major, Gemini, Andromeda are all constellations. Originally astronomers from different parts of the World used different patterns, but all today’s astronomers use the patterns the Roman astronomers used, two thousand years ago, but making up some more names for the constellations visible only from the Southern Hemisphere which the Romans could never have seen. Here are some of the constellations - only the brightest stars are shown.
The ecliptic and celestial equator are explained on other Pages. Where they meet is called The First Point of Aries and it has its own special symbol. It moves slowly: it was in Aries when it was named but it is now in Pisces.
Sam does not think that Aries looks much like a ram but this does not prevent him from finding it in the sky.
The Plough (in America Dipper) is not actually a constellation, although many books say that it is, it is only a part of the constellation Ursa Major (The Great Bear - but a bear with a tail!).
We can only see the stars and constellations between Sunrise and Sunset, and this means that as the Earth moves round the Sun we shall see different constellations each month.
When Sam first became interested in astronomy he was given a book which gave a map of the Night Sky for each month of the year - constellations and stars only, not the planets, because the planets move through the constellations: Mars might be in Aries today but it then moves into Taurus, then Gemini, then Cancer and so on - this is described on another Page.
Today he does not often use this book, he usually uses an App (Planets) on his iPad. He holds his iPad up to the sky and it shows everything, Moon, stars and planets, even comets, he can see.
Although only a very few of the very brightest stars (Sirius, Canopus, Betelgeuse, Arcturus, Viga, Aldebaran, etc) have ever been given names, today’s astronomers have catalogued every known star (millions and millions of them) in our galaxy: the catalogue entry includes the name of the constellation it is in and a combination of Greek letters and numbers. Sam finds explaining this to his friends boring - you do not need all this for naked-eye astronomy. Many star names are Greek or Roman, but lots more are Arabic.
© Barry Gray April 2020 | 0.881082 | 3.349546 |
The Solar System formed 4. 6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system’s mass is in the Sun, with the majority of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All eight planets have almost circular orbits that lie within a nearly flat disc called the ecliptic. | 0.831132 | 3.042682 |
Over the past four years, the instrument attached to the telescope in the Chilean Andes, the Gemini Planet Imager was staring at 531 star in search of new planets. And here is the team who worked with him, published in Astronomical Journal the initial results of the study, which captured three of six planets and a brown dwarf orbiting 300 stars. And what a very strange and interesting conclusions reached by scientists.
“Over the past twenty years, astronomers have discovered all these solar systems that are really different from ours,” says Bruce Macintosh, Professor of physics at Stanford University. “The question we want to understand ultimately is: are there populated, Earth-like planet? And one way to answer it is to understand how others are formed in the solar system.
Unlike other methods of finding planets, which rely on finding signs of the planet — such as the influence of its gravity on the parent star, not the planet itself — the Gemini Planet Imager makes images straight, snatching the planet from dim to bright light of a star a million times brighter.
“The giant planets in our own Solar system are 5 to 30 times farther than Earth, and for the first time, we investigated similar region near other stars,” says lead author Erik Nielsen, a researcher from the Institute Kavli.
Most of the other search methods explore the inner solar system. But Gemini Planet Imager particularly focuses on extrasolar planets that are large, young and are far from the star around which revolve.
In our Solar system the giant planets are in the outer part of it. But although Gemini Planet Imager is one of the most sensitive seekers of the planets, still remain objects that elude his perception, and the planet that the team can see at present, must be two times the size of Jupiter.
In the first part of the study, the researchers found exoplanets smaller than expected. However, the exoplanet was found, showed something interesting: each of the six planets revolved around the big one, despite the fact that such planets are easier to find near faint stars.
This suggests that giant planets with wide orbits are more common around stars with a large mass at least 1.5 times more massive than the Sun. Meanwhile, stars like our own, not so often store older brothers Jupiter as small planets that are discovered close to their stars during missions like “Kepler”.
“Given what we and other scientists have seen so far, our Solar system is not like other solar systems,” says McIntosh. “We have not so many planets Packed so close to the Sun, like other stars, and now we have preliminary evidence that we may be rare and on the other side of the range.”
Although exoplanets the size of Jupiter are beyond the reach of their instruments, can’t find even a hint of something similar to Jupiter among 300 stars, leaves open the possibility that our Jupiter is special.
Why do you think our Earth can also be special? Tell us in our chat in Telegram. | 0.803293 | 3.93722 |
From its familiar stripes to its giant red spot Jupiter has mesmerized scientists for hundreds of years. It is the most important planet in our solar system and its icy moons could Harbor key ingredients for life. An understanding they could help us answer some of the biggest questions about our solar system like how exactly did life form.
That is precisely what the European Space Agency’s (ESA’s) Juice mission hopes to find out. European Space Agency says the satellites of Jupiter are very interesting because there is probably more liquid water inside some of the satellites than on earth. So it became a fascinating question whether around a planet like Jupiter we might have places which are maybe interesting for life.
Jupiter icy moons Explorer or juice is European Space Agency’s (ESA’s) mission to study if the icy moons around Jupiter areas habitable as scientists think about it. The one orbital spacecraft will orbit Callisto and Europa however will make historical past as it orbits Ganymede for the first time ever. Thanks to measurements collected by NASA’s Galileo probe we now have a better idea of what may lie beneath the icy crust of these moons.
The presence of salty water and Europa is believed to have the most with an ocean containing more liquid than all of Earth’s oceans combined. Then we come to the apple of Juice’s eye Ganymede it’s the primary focus for this mission since it’s Jupiter’s largest moon and has its own magnetic field. Last but not least is Callisto because of its ancient and heavily cratered surface Callisto was long believed to be geologically inactive.
But that might not be true this moon may also hold an underwater ocean. It’s not every day that we send a spacecraft to Jupiter so Juice will be equipped with 10 instruments all working together to try and capture as much as possible. The form will be remote sensing instruments capable of capturing ultraviolet to the submillimetre wavelengths to better study Jupiter’s clouds, atmosphere and its satellites icy surfaces.
The next batch is the geophysical instruments that will study the surface and subsurface of the moons. As well as explore the atmosphere and measured the gravitational field. Finally, we have the in situ instruments composed of sensors to study the particle environment, electric and magnetic fields. But figuring out how to power the instruments and the spacecraft was a challenge.
Since Jupiter is roughly seven hundred and seventy-seven million kilometers away from the Sun. This makes it much harder to use solar power so to capture as much sunlight as possible juice will use massive solar arrays about 85 square meters in size.
Despite being the largest solar panels ever placed on a spacecraft they’ll provide less than 1,000 watts of power which is less powerful than a home vacuum cleaner. In total, the instruments in solar arrays will account for less than half the spacecraft’s 5 metric tons size.
While the rest is a chemical propellant to help steer the spacecraft for its orbital insertions. So what can we expect when it actually launches right now juice is slated to liftoff in 2022 aboard an Ariane 5 rocket but the launch will only be the first step.
Seven and a half years after its initial launch juice will finally arrive at Jupiter. After collecting tons of images and details of the largest moon it this point that juice will make a planned crash on the Ganymede surface. Hopefully leaving us with a greater understanding of our solar system’s largest planet and its mysterious moons. And we’re juiced for the outcomes. | 0.84391 | 3.723779 |
After sixty years of space agencies sending rockets, satellites and other missions into orbit, space debris has become something of a growing concern. Not only are there large pieces of junk that could take out a spacecraft in a single hit, but there are also countless tiny pieces of debris traveling at very high speeds. This debris poses a serious threat to the International Space Station (ISS), active satellites and future crewed missions in orbit.
For this reason, the European Space Agency is looking to develop better debris shielding for the ISS and future generations of spacecraft. This project, which is supported through the ESA’s General Support Technology Programme, recently conducted ballistics tests that looked at the efficiency of new fiber metal laminates (FMLs), which may replace aluminum shielding in the coming years.
To break it down, any and all orbital missions – be they satellites or space stations – need to be prepared for the risk of high-speed collisions with tiny objects. This includes the possibility of colliding with human-made space junk, but also includes the risk of micro-meteoroid object damage (MMOD). These are especially threatening during intense seasonal meteoroid streams, such as the Leonids.
While larger pieces of orbital debris – ranging from 5 cm (2 inches) to 1 meter (1.09 yards) in diameter – are regularly monitored by NASA and and the ESA’s Space Debris Office, the smaller pieces are undetectable – which makes them especially threatening. To make matters worse, collisions between bits of debris can cause more to form, a phenomena known as the Kessler Effect.
And since humanity’s presence Near-Earth Orbit (NEO) is only increasing, with thousands of satellites, space habitats and crewed missions planned for the coming decades, growing levels of orbital debris therefore pose an increasing risk. As engineer Andreas Tesch explained:
“Such debris can be very damaging because of their high impact speeds of multiple kilometres per second. Larger pieces of debris can at least be tracked so that large spacecraft such as the International Space Station can move out of the way, but pieces smaller than 1 cm are hard to spot using radar – and smaller satellites have in general fewer opportunities to avoid collision.”
To see how their new shielding would hold up to space debris, a team of ESA researchers recently conducted a test where a 2.8 mm-diameter aluminum bullet was fired at sample of spacecraft shield – the results of which were filmed by a high-speed camera. At this size, and with a speed of 7 km/s, the bullet effectively simulated the impact energy that a small piece of debris would have as if it came into contact with the ISS.
As researcher Benoit Bonvoisin explained in a recent ESA press release:
“We used a gas gun at Germany’s Fraunhofer Institute for High-Speed Dynamics to test a novel material being considered for shielding spacecraft against space debris. Our project has been looking into various kinds of ‘fibre metal laminates’ produced for us by GTM Structures, which are several thin metal layers bonded together with composite material.”
As you can see from the video (posted above), the solid aluminum bullet penetrated the shield but then broke apart into a could of fragments and vapor, which are much easier for the next layer of armor to capture or deflect. This is standard practice when dealing with space debris and MMOD, where multiple shields are layered together to adsorb and capture the impact so that it doesn’t penetrate the hull.
An common variant of this is known as the ‘Whipple shield’, which was originally devised to guard against comet dust. This shielding consists of two layers, a bumper and a rear wall, with a mutual distance of 10 to 30 cm (3.93 to 11.8 inches). In this case, the FML, which is produced for the ESA by GTM Structures BV (a Netherlands-based aerospace company), consists of several thin metal layers bonded together with a composite material.
Based on this latest test, the FML appears to be well-suited at preventing damage to the ISS and future space stations. As Benoit indicated, he and his colleagues now need to test this shielding on other types of orbital missions. “The next step would be to perform in-orbit demonstration in a CubeSat, to assess the efficiency of these FMLs in the orbital environment,” he said.
And be sure to enjoy this video from the ESA’s Orbital Debris Office:
Further Reading: ESA
Where do they come from, those beguiling singularities that flummox astrophysicists—and the rest of us.…
Astronomers don’t know exactly when the first stars formed in the Universe because they haven’t…
Our measurements of dark energy give contradictory results. A new study confirms dark energy, but…
There's an unusual paradox hampering research into parts of the Milky Way. Dense gas blocks… | 0.81937 | 3.73808 |
Astronomy is a natural science; it is the study of celestial objects. Observational astronomy is part of the astronomical science; it includes the study of registered data, as against conceptual astrophysics. Astrophysics is mainly interested in finding out the measurable significance of physical model. In observational astronomy, celestial objects are observed by using telescopes and other astronomical apparatus.
As a science, in the study of astronomy, direct experiments aren’t possible due to the universe being distant, but astronomers can partly comprehend it by the fact that they have huge numbers of perceptible examples of data associated with stars and space that could be examined. These examined observational data; one can trace on a graph and record the general trends. Here, take the example of specific phenomenon, such as a variable star, whose brightness as seen from the earth seems to fluctuate. These can be used for deducing the behavior of remote representatives. For measuring different phenomena in that neighborhood, including the distance to the galaxy, these distant yardsticks can be employed.
Galileo Galilee turned the telescope heavenwards in the autumn months of 1609. As the telescope, technology grew, so did the advancement in observational technology.
Optical astronomy uses optical components like mirror, lenses and detectors to monitor light from near infrared to near ultraviolet wavelength and studies the measurement of the electromagnetic spectrum wavelength.
Infrared astronomy includes detection and study of the Infrared (IR) radiation (heat energy) emitted from an object in the universe. Infrared light wavelength ranges from 0.75 to 300 micrometers.
Radio astronomy includes the study of celestial objects that give off radio waves. It detects radiation in the millimeter to dekameter wavelength using a receiver similar to the one used in radio broadcast transmission, but they are more sensitive.
Ground based observatories are capable of measuring radio and optical wavelengths due to the transparency of the atmosphere for clear wavelength observation, For reduction of absorption and distortion which happens due to Earth’s atmosphere, observatories are placed at high altitudes. Since water has a habit of absorbing infra red light, some of these observatories are located at extremely dry locations or in space
For observation of distant planets, galaxies and other outer space objects an instrument (like a telescope) is used in outer space called a space observatory. The Hubble Space Telescope was the first space observatory established in 1990. Many problems of ground observatories like light pollution, filtering, distortion of electromagnetic radiation can be avoided by space observatories.
Hubble Space Telescope
The Hubble Space Telescope is one which was established, into low earth orbit in 1990. It still remains working. Near ultraviolet, visible, near infrared spectrum is observed by Hubble’s four main instruments that use a 2.4 meter (7.9 ft) mirror to observe infrared and near ultraviolet spectrums. The telescope takes its name from the astronomer, Edwin Hubble.
Chandra X-ray Observatory
The Chandra X-ray Observatory, earlier known as the Advanced X-ray Astrophysics Facility (AXAF) is a type of the space observatory first established by NASA on July 23, 1999 as STS-93. Chandra is fragile to X-ray sources when compared to earlier X-ray telescopes and is empowered by its mirror that has a high angular resolution/. Since the Earth’s atmosphere absorbs a great portion of the x-ray Earth-based telescopes prove inadequate, for which reason, only space based observatories with telescopes, can do the job. An earth satellite, Chandra on a 64-hour orbit that was programmed to work till 2015. | 0.864435 | 3.788221 |
What can unite a specialist in quantum physics, geology and mathematics? Of course, the desire to solve the riddle of the universe! Scientists have found that observing the behavior of the oceans of the Earth will help to explore even the remote corners of the galaxy.
As we all know, science is full of surprises, and sometimes it brings together phenomena and concepts that at first glance have nothing in common. It would seem that there is a connection between a certain type of oceanic waves that controls the El Niño climate cycle and quantum materials, the distinguishing feature of which is their ability to conduct a current only by the surface part? Physicists, nevertheless, assure us that both these phenomena can be explained by the same mathematical principles.
How quantum physics affects the weather in the world
Brad Marston, a physicist at Brown University, and the principal author of the new study, tried to prove a very interesting theory. In his opinion, the use of topological principles can explain both the phenomenon of the fact that oceanic and atmospheric waves on the equator fall into a kind of “trap”, and that the physics of the condensed state (a huge section of physics that studies the behavior of complex systems and argues that evolution system as a whole can not be “divided” into the evolution of its individual parts) can be equally useful both for the Earth and for explaining phenomena on other planets and moons. In simple terms: the main goal of the work is to prove that the principles of quantum physics are equally valid for our planet and for other cosmic bodies.
But how to prove such a large-scale theory? For this, Marston teamed up with Pierre Delac, a specialist in the field of condensed matter physics, and also with geophysicist Antoine Venail. Scientists have applied the theory of condensed state to two types of gravitational waves, known as waves of Kelvin and Yanai, which propagate along seas and air around the equator of the Earth. These wave-like distortions, hundreds and thousands of kilometers in length, transmit the energy pulse east of the equator, which greatly influences El Niño, the system of fluctuations in the temperature of the surface waters of the Pacific Ocean, on which the weather conditions and precipitation depend. This is due to the interaction of several physical processes. Firstly, the force of gravity comes into opposition with buoyancy, which causes cooling / heating of air and water due to independent droplets. Secondly, the rotation of the Earth to the east creates the so-called Coriolis effect, which causes the fluids to move along the Earth’s surface in opposite directions, depending on the hemisphere.
From theory to … theory
To see how the effects interact with each other and form waves, Marston and his colleagues followed the same strategy as Taro Matsuno, a scientist at the University of Tokyo, who in 1966 predicted an equatorial “trap” for the waves. Here, quantum physics enters into the matter: scientists simplify the structure of the whole ocean and focus their attention on a narrow band, during which the Coriolis effect remains approximately constant. But they do not calculate all calculations for equatorial waves, but for those that are better suited for analysis. Physicists also switch to a simpler task to demonstrate that it contains a response to the original question, albeit implicitly.
Marston and his colleagues study waves not in ordinary space, but in the abstract space of all possible waves with different wavelengths and Coriolis effects. Equations for extremely long waves show two special mathematical points, where the amplitude of the wave varies greatly with its length. These points are called “mathematical holes”, and there are two of them, since the Earth has two hemispheres with oppositely directed Coriolis forces. As a result, as the researchers note in the pages of the Science portal, the hemispheres behave like two pieces of electrical insulating material. Just as the combination of two electrical insulating materials allows the current to flow along their surface, the union of the two hemispheres leads to the appearance of waves on their boundary – the equator, which decreases with increasing latitude. And, as in the case of the material, the waves are stable or, as physicists say, “topologically protected” by the features of the abstract space.
The Future: Quantum Physics in the Hands of Astronomers
What does astronomy have to do with it? According to Marston, the principle of action of these waves is the same for any rotating planet. Scientists have established that even if it is in the form of a donut, the situation will not change it. This system in theory can be applied to other cosmic phenomena, for example, disks of dust and gas around black holes, as well as to the atmospheres of Venus and Titan, on which equatorial waves were also recorded. Thus, in the hands of scientists is a powerful topological tool that will learn about the geophysics of the planet long before they send a probe or expedition mission. | 0.866048 | 3.707422 |
Tides are one of the most reliable phenomena in the world. As the sun rises in the east and the stars come out at night, we are confident that the ocean waters will regularly rise and fall along our shores. The following pages describe the tremendous forces that cause the world’s tides, and why it is important for us to understand how they work.
Basically, tides are very long-period waves that move through the oceans in response to the forces exerted by the moon and sun. Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface. When the highest part, or crest of the wave reaches a particular location, high tide occurs; low tide corresponds to the lowest part of the wave, or its trough. The difference in height between the high tide and the low tide is called the tidal range.
A horizontal movement of water often accompanies the rising and falling of the tide. This is called the tidal current. The incoming tide along the coast and into the bays and estuaries is called a flood current; the outgoing tide is called an ebb current. The strongest flood and ebb currents usually occur before or near the time of the high and low tides. The weakest currents occur between the flood and ebb currents and are called slack tides. In the open ocean tidal currents are relatively weak. Near estuary entrances, narrow straits and inlets, the speed of tidal currents can reach up to several kilometers per hour (Ross, D.A., 1995).
Gravity is one major force that creates tides. In 1687, Sir Isaac Newton explained that ocean tides result from the gravitational attraction of the sun and moon on the oceans of the earth (Sumich, J.L., 1996).
Newton’s law of universal gravitation states that the gravitational attraction between two bodies is directly proportional to their masses, and inversely proportional to the square of the distance between the bodies (Sumich, J.L., 1996; Thurman, H.V., 1994). Therefore, the greater the mass of the objects and the closer they are to each other, the greater the gravitational attraction between them (Ross, D.A. 1995).
Tidal forces are based on the gravitational attractive force. With regard to tidal forces on the Earth, the distance between two objects usually is more critical than their masses. Tidal generating forces vary inversely as the cube of the distance from the tide generating object. Gravitational attractive forces only vary inversely to the square of the distance between the objects (Thurman, H.V., 1994). The effect of distance on tidal forces is seen in the relationship between the sun, the moon, and the Earth’s waters.
Our sun is 27 million times larger than our moon. Based on its mass, the sun’s gravitational attraction to the Earth is more than 177 times greater than that of the moon to the Earth. If tidal forces were based solely on comparative masses, the sun should have a tide-generating force that is 27 million times greater than that of the moon. However, the sun is 390 times further from the Earth than is the moon. Thus, its tide-generating force is reduced by 3903, or about 59 million times less than the moon. Because of these conditions, the sun’s tide-generating force is about half that of the moon (Thurman, H.V., 1994).
Gravity, Inertia, and the Two Bulges
Gravity is a major force responsible for creating tides. Inertia, acts to counterbalance gravity. It is the tendency of moving objects to continue moving in a straight line. Together, gravity and inertia are responsible for the creation of two major tidal bulges on the Earth (Ross, D.A., 1995).
The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer. This attraction causes the water on this “near side” of Earth to be pulled toward the moon. As gravitational force acts to draw the water closer to the moon, inertia attempts to keep the water in place. But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon (Ross, D.A., 1995).
On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away. Here, inertia exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge (Ross, D.A., 1995).
In this way the combination of gravity and inertia create two bulges of water. One forms where the Earth and moon are closest, and the other forms where they are furthest apart. Over the rest of the globe gravity and inertia are in relative balance. Because water is fluid, the two bulges stay aligned with the moon as the Earth rotates (Ross, D.A., 1995).
The sun also plays a major role, affecting the size and position of the two tidal bulges. The interaction of the forces generated by the moon and the sun can be quite complex. As this is an introduction to the subject of tides and water levels we will focus most of our attention on the effects of the stronger celestial influence, the moon.
Changing Angles and Changing Tides
As we’ve just seen, the Earth’s two tidal bulges are aligned with the positions of the moon and the sun. Over time, the positions of these celestial bodies change relative to the Earth’s equator. The changes in their relative positions have a direct effect on daily tidal heights and tidal current intensity.
As the moon revolves around the Earth, its angle increases and decreases in relation to the equator. This is known as its declination. The two tidal bulges track the changes in lunar declination, also increasing or decreasing their angles to the equator. Similarly, the sun’s relative position to the equator changes over the course of a year as the Earth rotates around it. The sun’s declination affects the seasons as well as the tides. During the vernal and autumnal equinoxes—March 21 and September 23, respectively—the sun is at its minimum declination because it is positioned directly above the equator. On June 21 and December 22—the summer and winter solstices, respectively—the sun is at its maximum declination, i.e., its largest angle to the equator (Sumich, J.L., 1996).
Frequency of Tides – The Lunar Day
Most coastal areas, with some exceptions, experience two high tides and two low tides every lunar day (Ross, D.A., 1995). Almost everyone is familiar with the concept of a 24-hour solar day, which is the time that it takes for a specific site on the Earth to rotate from an exact point under the sun to the same point under the sun. Similarly, a lunar day is the time it takes for a specific site on the Earth to rotate from an exact point under the moon to the same point under the moon. Unlike a solar day, however, a lunar day is 24 hours and 50 minutes. The lunar day is 50 minutes longer than a solar day because the moon revolves around the Earth in the same direction that the Earth rotates around its axis. So, it takes the Earth an extra 50 minutes to “catch up” to the moon (Sumich, J.L., 1996; Thurman, H.V., 1994).
Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes. High tides occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high.
Tidal Variations – The Influence of Position and Distance
The moon is a major influence on the Earth’s tides, but the sun also generates considerable tidal forces. Solar tides are about half as large as lunar tides and are expressed as a variation of lunar tidal patterns, not as a separate set of tides. When the sun, moon, and Earth are in alignment (at the time of the new or full moon), the solar tide has an additive effect on the lunar tide, creating extra-high high tides, and very low, low tides—both commonly called spring tides. One week later, when the sun and moon are at right angles to each other, the solar tide partially cancels out the lunar tide and produces moderate tides known as neap tides. During each lunar month, two sets of spring tides and two sets of neap tides occur (Sumich, J.L., 1996).
Just as the angles of the sun, moon and Earth affect tidal heights over the course of a lunar month, so do their distances to one another. Because the moon follows an elliptical path around the Earth, the distance between them varies by about 31,000 miles over the course of a month. Once a month, when the moon is closest to the Earth (at perigee), tide-generating forces are higher than usual, producing above-average ranges in the tides. About two weeks later, when the moon is farthest from the Earth (at apogee), the lunar tide-raising force is smaller, and the tidal ranges are less than average. A similar situation occurs between the Earth and the sun. When the Earth is closest to the sun (perihelion), which occurs about January 2 of each calendar year, the tidal ranges are enhanced. When the Earth is furthest from the sun (aphelion), around July 2, the tidal ranges are reduced (Sumich, J.L., 1996; Thurman, H.V., 1994).
Types and Causes of Tidal Cycles –Diurnal, Semidiurnal, Mixed Semidiurnal; Continental Interference
If the Earth were a perfect sphere without large continents, all areas on the planet would experience two equally proportioned high and low tides every lunar day. The large continents on the planet, however, block the westward passage of the tidal bulges as the Earth rotates. Unable to move freely around the globe, these tides establish complex patterns within each ocean basin that often differ greatly from tidal patterns of adjacent ocean basins or other regions of the same ocean basin (Sumich, J.L., 1996).
Three basic tidal patterns occur along the Earth’s major shorelines. In general, most areas have two high tides and two low tides each day. When the two highs and the two lows are about the same height, the pattern is called a semi-daily or semidiurnal tide. If the high and low tides differ in height, the pattern is called a mixed semidiurnal tide. Some areas, such as the Gulf of Mexico, have only one high and one low tide each day. This is called a diurnal tide. The U.S. West Coast tends to have mixed semidiurnal tides, whereas a semidiurnal pattern is more typical of the East Coast (Sumich, J.L., 1996; Thurman, H.V., 1994; Ross, D.A., 1995).
What Affects Tides in Addition to the Sun and Moon?
The relative distances and positions of the sun, moon and Earth all affect the size and magnitude of the Earth’s two tidal bulges. At a smaller scale, the magnitude of tides can be strongly influenced by the shape of the shoreline. When oceanic tidal bulges hit wide continental margins, the height of the tides can be magnified. Conversely, mid-oceanic islands not near continental margins typically experience very small tides of 1 meter or less (Thurman, H.V., 1994).
The shape of bays and estuaries also can magnify the intensity of tides. Funnel-shaped bays in particular can dramatically alter tidal magnitude. The Bay of Fundy in Nova Scotia is the classic example of this effect, and has the highest tides in the world—over 15 meters (Thurman, H.V., 1994). Narrow inlets and shallow water also tend to dissipate incoming tides. Inland bays such as Laguna Madre, Texas, and Pamlico Sound, North Carolina, have areas classified as non-tidal even though they have ocean inlets. In estuaries with strong tidal rivers, such as the Delaware River and Columbia River, powerful seasonal river flows in the spring can severely alter or mask the incoming tide.
Local wind and weather patterns also can affect tides. Strong offshore winds can move water away from coastlines, exaggerating low tide exposures. Onshore winds may act to pile up water onto the shoreline, virtually eliminating low tide exposures. High-pressure systems can depress sea levels, leading to clear sunny days with exceptionally low tides. Conversely, low-pressure systems that contribute to cloudy, rainy conditions typically are associated with tides than are much higher than predicted.
The Importance of Monitoring the Tides and Their Currents
Predicting tides has always been important to people who look to the sea for their livelihood. Commercial and recreational fishermen use their knowledge of the tides and tidal currents to help them improve their catches. Depending on the species and water depth in a particular area, fish may concentrate during ebb or flood tidal currents. In some areas, strong tidal currents concentrate bait and smaller fish, attracting larger fish. In addition, knowledge of the tides has also been of interest to recreational beachgoers and surfers.
Navigating ships through shallow water ports, intracoastal waterways and estuaries requires knowledge of the time and height of the tides as well as the speed and direction of the tidal currents. This was particularly critical to sailing ships because they had to take advantage of the tides and currents to manuever correctly. Knowledge of tides and currents is still critical because today’s vessels are much larger than the old sailing ships. The depths and widths of the channels in which they sail, and the increased marine traffic leaves very little room for error. Real-time water level, water current, and weather measurement systems now are being used in many major ports to provide mariners and port operators with the latest conditions.
Coastal zone engineering projects, including the construction of bridges, docks, etc., require engineers to monitor fluctuating tide levels. Projects involving the construction, demolition or movement of large structures must be scheduled far in advance if an area experiences wide fluctuations in water levels during its tidal cycle. Habitat restoration projects also require accurate knowledge of tide and current conditions.
Scientists are concerned with tides, water levels and tidal currents as well. Ecologists may focus on the tidal mixing of near-shore waters, where pollutants are removed and nutrients are recirculated. Tidal currents also move floating animals and plants to and from breeding areas in estuaries to deeper waters. Oceanographers or atmospheric scientists may study tidal fluctuations to better understand the circulation of the ocean and its relationship to world climatic changes.
How are Tides Measured? – The Old System
Since the early 1800s, NOAA and its predecessor organizations have been measuring, describing and predicting tides along the coasts of the United States. The longest continuous sea level records exists for the Presidio, in San Francisco, California. Records for the area date back to June 30, 1854. Today, the Center for Operational Oceanographic Products and Services (CO-OPS), which is part of NOAA’s National Ocean Service (NOS), is responsible for recording and disseminating water level data.
In the past, most water level measuring systems used a recorder driven by a float in a “stilling” well. A stilling well calms the waters around the water level sensor. A typical stilling well consisted of a 12-inch wide pipe. Inside the stilling well, an 8-inch diameter float was hung by wire from the recording unit above.
Before computers were used, water level data was recorded on a continuously running pen and ink strip chart. These records were collected by observers once a month and mailed to headquarters for manual processing. In the 1960s, data were recorded onto mechanically punched paper tape that were read into a computer for processing. Water levels were recorded at 6-minute intervals. Observers maintained and adjusted the clocks, and calibrated the gauges with the tide readings. Tide stations were visited annually to maintain the tide houses and clean biological fouling from the underwater surfaces. During these annual visits, the components and support structures also were checked for stability.
Although these systems worked well, they had their limitations. Stations were subject to recording errors and marine fouling, and were constantly in need of maintenance. In addition, the measurement and data processing equipment could not provide users with information until weeks after the data was collected.
How are Tides Measured? – The New System
Advances in technology have helped solve many of the problems associated with the old tidal recording systems. Microprocessor-based technologies allow for customized data collection and have improved measurement accuracy. While older tidal measuring stations used mechanical floats and recorders, a new generation of monitoring stations uses advanced acoustics and electronics. Today’s recorders send an audio signal down a half-inch-wide sounding tube and measure the time it takes for the reflected signal to travel back from the water’s surface. The sounding tube is mounted inside a 6-inch diameter protective well, which is similar to the old stilling well.
In addition to measuring tidal heights more accurately, the new system also records 11 different oceanographic and meteorological parameters. These include wind speed and direction, water current speed and direction, air and water temperature, and barometric pressure.
Like the old recorders, the new measuring stations collect data every six minutes. However, whereas the old recording stations used mechanical timers to tell them when to take a reading, timing is controlled on the new stations by a Geostationary Operational Environmental Satellite (GOES). The stations also use these satellites to transmit their data hourly to NOAA headquarters. In the event of a storm, the stations can be programmed to transmit their data every six minutes. Field teams can quickly check and maintain the systems using laptop computers. In addition, all of the raw and processed data are available over the Internet.
Ross, D.A. 1995. Introduction to Oceanography. New York, NY: HarperCollins. pp. 236-242.
Sumich, J.L. 1996. An Introduction to the Biology of Marine Life, sixth edition. Dubuque, IA: Wm. C. Brown. pp. 30-35.
Thurman, H.V. 1994. Introductory Oceanography, seventh edition. New York, NY: Macmillan. pp. 252-276.
Tides Roadmap to Resources
These online resources are meant to guide students and educators to topics presented in the online tides and water levels tutorial. The following links will take you to specific Web pages created and managed by NOAA�s Center for Operational Oceanographic Products and Services (CO-OPS). CO-OPS predicts, records and distributes oceanographic and meteorological data from thousands of monitoring stations in U.S. coastal and territorial waters.
Please note: The Web links provided have been checked at the time of this page’s publication, but the linking sites may become outdated or non-operational over time. If you should come across a non operational link please contact NOAA Ocean Service Education at [email protected]
“Our Restless Tides” provides comprehensive information about the astronomical and physical forces that cause and affect the world’s tides. Detailed diagrams and mathematical formulae illustrating the forces acting on the world’s oceans are presented.
http://tidesandcurrents.noaa.gov/publications/glossary2.pdf (28 pages, pdf, 600Kb)
The “Glossary of Tide and Current Terminology” is and indispensable reference tool lists and defines more than 400 terms and concepts concerned with the tidal phenomena and its measurement.
The “NOS Water Level Observation Network” lets you to access graphic presentations of predicted and observed water levels, air and water temperatures, wind speed and direction, and air pressure in real time from U.S. coastal and territorial waters. After clicking on a state, select a tidal monitoring station and click on it. Predicted readings for an area will appear in blue, and actual observations will appear in red. To view a good example of a diurnal tidal cycle, select a tidal station in Louisiana, Mississippi or Alabama. To see semi-diurnal tides, select a coastal monitoring station from a northeastern state such as Delaware or Maine. Note that the tidal range increases as you move further north. To observe mixed semidiurnal tides, select any one of the tidal stations on the west coast.
The “Physical Oceanographic Real Time System” (PORTS�) Web site provides real-time oceanographic and meteorological data for 15 major U.S. harbors. After selecting a particular harbor, you can view the types and geographic placement of different sensors in that area by clicking on the sensor locations highlighted on the area maps. To zoom in on a particular area where an instrument is stationed, click on the “plus” symbol in the upper left hand side of the image. You can reorient the image by “dragging” it with your mouse or using the arrow buttons on the upper left hand side of the image. To view specific data for a particular sensor in graphic format click on the image of data graph you wish to view. To view the data in ASCII, or text format, scroll down the page of the graphic presentation and click on the link to the data set you want to see.
The “NOS Water Level Observation Network – Great Lakes” Web site provides real-time observations of water levels for seven of the eight states bordering the five Great Lakes. You can select a particular monitoring station by choosing a state and clicking on it. A map will appear showing the geographic locations of all the monitoring stations in the state. Select one of these stations to view a graph of water levels in real time at that site for a 24-hour period. To view the data in ASCII, or text format, scroll down the page and click on the link to the data listing.
This Web site provides you with tidal predictions computed by CO-OPS for more than 3000 tidal current stations. Click on the year for which you want tidal prediction data. This opens a new page with a list of states and other areas for which there are tide stations on the left side of the page. Clicking on a state name displays a list of regions within that state. Clicking on a region name will present a list of the tidal current stations in the area. These stations are listed geographically. This will make finding the location you are interested in, or a nearby station, simpler.
Unlike tide stations, which are normally located along the shoreline, most tidal current stations are located offshore in channels, rivers, and bays. These stations are often named for the channel, river, or bay in which they are located or for a nearby navigational reference point. A map or some personal knowledge of the area may help you identify stations.
To access tidal current data from 2004 through 2006 go to: http://tidesandcurrents.noaa.gov/products.html On the left hand side of the page look beneath “Predictions” and then beneath “Published Current Tables” click the year for which you wish to view tidal current data.
Similar to the tidal current prediction Web site above, this site provides you with water level predictions for more than 3000 water level stations. The list of stations may be selected from a listing on the main part of the page, or from a sub-listing of stations broken down by state which can be accessed on the left hand side of the page. You can also use the interactive map feature accessible from the page to search for a tidal station geographically.
To access tidal data from 2004 through 2006 point go to: http://tidesandcurrents.noaa.gov/products.html On the left hand side of the page look beneath “Predictions” and then beneath “Published Tide Tables” click the year that you wish to view tidal current data for.
“About Water Levels, Tides & Currents” provides links to additional information including Tide Predicting Machines, How Does One Measure Water Levels, Why Does One Measure Water Levels, and The Challenge of Measuring Water Currents.
“Understanding Tides” is a technical publication authored by Stacy Dopp Hicks, provides in-depth explanations of many aspects of tides, including Gravitational Attraction, Sun-Earth and Moon-Earth Systems, Spring and Neap Tides, Tide-Generating Forces, Tidal Waves in Gulfs and Estuaries, Tidal Bores, and Tidal Harmonic Constituents.
Last revised 24-Jan-16 | 0.85256 | 3.629175 |
Identifying close binary central stars of PN with Kepler
Six planetary nebulae (PN) are known in the Kepler space telescope field of view, three of which are newly identified. Of the five central stars of PN with useful Kepler data, one, J193110888+4324577, is the first short-period, post-common envelope binary exhibiting relativistic beaming effects. A second, the central star of the newly identified PN Pa 5, has a rare O(He) spectral type and a periodic variability consistent with an evolved companion, where the orbital axis is almost aligned with the line of sight. The third PN, NGC 6826, has a fast rotating central star, something that can only be achieved in a merger. Fourth, the central star of the newly identified PN Kn 61, has a PG1159 spectral type and a mysterious semi-periodic light variability which we conjecture to be related to the interplay of binarity with a stellar wind. Finally, the central star of the circular PN A61 does not appear to have a photometric variability above 2 mmag. With the possible exception of the variability of Kn 61, all other variability behaviour, would not easily have been detected from the ground. We conclude, based on very low numbers, that there may be many more close binary or close binary products to be discovered with ultra-high-precision photometry. With a larger number of high-precision photometric observations, we will be able to determine how much higher than the currently known 15 per cent, the short-period binary fraction for central stars of PN is likely to be.
Marco, Orsola De; Long, J; Jacoby, George H.; and Hillwig, Todd, "Identifying close binary central stars of PN with Kepler" (2015). Physics and Astronomy Faculty Publications. 136. | 0.824672 | 3.638857 |
During the Perseid meteor shower this month I did some reminiscing on how, as a teenager, I used to watch this famous meteor display from my Aunt Irma and Uncle Ron’s house in then-rural Mahopac, New York, about 50 miles north of New York City.
In the early 1970s the northern suburbs of New York were amazingly dark — much darker then compared to now – and whenever I visited my Aunt and Uncle I always made sure to bring my binoculars or telescope with me, because their night skies provided a treasure-trove of celestial sights that I could never hope to see from my light-polluted home base in The Bronx.
And on one of those memorable midsummer nights, some 40 years ago, I stumbled across one of the most pleasing night sky sights for those using binoculars. It can be found this week nearly overhead in our late evening sky. With a bright moon currently out of the way, now is a good time to seek it out.
A coat hangar in space
Most amateur astronomers have heard of such beautiful open star clusters as the Pleiades, Hyades and the Beehive. But have you ever heard of the Coat Hanger?
Some evening this week, if you turn your binoculars east-southeast and look midway up from the horizon to the region of the sky roughly halfway between the bright stars Vega and Altair you will discover Brocchi's Cluster in the rather dim and nondescript constellation of Vulpecula, the Little Fox. [Amazing August Night Sky Photos]
During the 1920s, Dalmiro F. Brocchi, then a well-known chart maker for the American Association of Variable Star Observers, designed a star chart depicting the region of the sky around Vulpecula, revealing this cluster.
For reasons that I have never been able to fathom, Brocchi’s Cluster is rarely mentioned in most popular astronomy books. Yet, it is the brightest of all the star clusters in this part of the sky! In Swedish astronomer Per Collinder’s star catalogue, which was drawn up in 1931, it is cluster No. 399, hence its “official designation as Collinder 399.
Those who have seen it have described it as a rather curious grouping of about a dozen tiny stars looking very much like an inverted coat hanger. In a clear, dark sky you might even perceive it with the naked eye as a fuzzy patch of light imbedded within the summer star clouds of the Milky Way. This is one object that is best suited for binoculars; even a small telescope will provide too much magnification and will cause the stars to appear too widely spaced apart.
Cosmic ladle or celestial seesaw?
Forty years ago while sweeping up and down the Milky Way with 7 x 35 binoculars, this delightful little cluster first hit my eyes. But actually, because the coat hanger figure appears upside down and a bit on a tilt, my original impression of it of it resembled some sort of a ladle (and since I was visiting my Aunt Irma when I made the discovery, I unofficially christened it "Irma’s Ladle").
Interestingly, what we are seeing in this pattern of stars is an illusion of perspective. This is not a true cluster at all, but rather just a chance alignment of stars that are placed at very different distances from our earthly vantage point.
However … Collinder 399 is really a proper coat hanger only for Southern Hemisphere observers, where it appears right side up. It is for this reason, that not everyone sees Collinder 399 as a coat hanger. In fact, I once heard of one gentleman out in California who independently discovered it and later inquired as to "Why is this fulcrum never shown on star charts? It is a beautiful sight."
And indeed, now that I’ve mentioned this allusion, it may cause many to see this cluster not as a coat hanger, but as a seesaw!
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. | 0.915047 | 3.617572 |
This Year’s Meteor Showers Will Be Spectacular. Here’s How to See All of Them at Peak.
There's no solar eclipse this year, but there are still plenty of dazzling stellar displays to get excited about. Bill Cooke, who leads NASA's Meteoroid Environment Office, helped pinpoint the meteor showers that are worth getting excited about this year.
To watch any of these meteor showers, you need to get far from the city. Find an open area where you can see to the horizon and, most importantly, where the sky is dark. The Dark Sky Finder app is a useful tool to help you find a spot to set up shop. It's also recommended you give yourself about 30 minutes for your eyes to adjust to the darkness. Then the show will appear at its most brilliant.
Unfortunately, you'll have to wait until April 22 for the first peak night following the Quadrantids in early January. Until then, you can plan for a blue moon total lunar eclipse, which will take place on January 31.
Peak Date: April 22
The Lyrids come from the Comet Thatcher, which makes a trip around our sun once every 415 years. It won't be back until 2276, but you can get a glimpse of its detritus when you look up at the Lyrids, which produce between 10 and 15 meteors per hour, according to Cooke.
The Lyrids tend to lack persistent trains but occasionally produce fireballs, which are basically exceptionally bright meteors. Despite the low rate, a first quarter moon will make for solid viewing conditions after midnight.
The Eta Aquariids
Peak Date: May 6
The Eta Aquariids is one of two meteor showers that stems from Halley's Comet. The Eta Aquariids are best viewed from the southern hemisphere. In the northern hemisphere, expect around 25 meteors per hour before dawn. Unfortunately, this year, we'll be just past a full moon, which will greatly reduce the number of visible meteors.
The Southern Delta Aquariids
Peak Date: July 27-30
The Southern Delta Aquariids are similar to the Eta Aquariids in that they're best seen from the southern hemisphere. While its host comet, Comet 96P Machholz, comes around with relative frequency, Cooke says we could "maybe" see 20 meteors per hour at its peak, which is usually around 2am local time. Many of those meteors may be washed out by a moon that's just past full.
Peak Date: August 12
The Perseids are, in a year with no outbursts, the most active meteor shower that doesn't take place in December. The Perseids often produce more than 100 meteors per hour. This year, look for something a little closer to a meteor per minute. A mid-August meteor shower with tons of meteors streaking over your head? That sounds pretty damn perfect.
Peak Date: October 21
The Orionids is the second shower showcasing the refuse of Halley's Comet. There's a waxing gibbous moon, but Cooke notes that shouldn't be a problem if you go out just before dawn, which is a great time to catch the Orionids. The shower is expected to produce between 20 and 30 meteors per hour.
Peak Date: November 17
The Leonids vacillate from being a standard meteor shower to the most dazzling storm you'll ever see. When it was first spotted in an outburst year, people thought the world was ending. In those situations, it can produce more than 1,000 meteors per hour. However, that hasn't happened since 2002 and is expected to again until 2032, according to Cooke. When the shower isn't in an outburst year, a more moderate 10 to 20 meteors per hour is likely. Unfortunately, the Leonids land near a full moon this year and will be largely washed out by the moonlight.
Peak Date: December 14
The Geminids will be the best show of the year in terms of how many meteors per hour will appear at its peak. Projections range from 120 to 160 meteors per hour and the moon will be working with you if you stay up late to watch it. The Perseids have much better weather and a broad peak, but the Geminids are the main event.
Peak Date: December 22
The Ursids are often called the Cursed Ursids since they come just before Christmas and near the winter solstice. This year they are truly are cursed. Cooke says the Ursids "may outburst," producing between 30 and 40 meteors per hour. But the Ursids are not bright and they'll fall on the night of a full moon. | 0.800208 | 3.527256 |
Produces shocks that accelerate particles, illuminating the colliding material
Space news (astrophysics: relativistic jets; shock collisions inside particle jets) – Observing plasma jet blasting from supermassive black hole in core of galaxy NGC 3862, 260 million light-years from Earth toward the constellation Leo in the rich galaxy cluster Abell 1367 –
Astronomers recently made an interesting discovery while studying data collected by the Hubble Space Telescope over two decades of observing the core of elliptical galaxy NGC 3862. They were originally looking to create a time-lapse video of a relativistic jet blasting from the supermassive black hole thought to reside within its core. Instead, they discovered a rear-end collision between two separate high-speed waves of material ejected by a monster black hole whose mass astronomers have yet to measure. In this case, scientists believe the rear-end collision accelerated and heated particles which illuminated the colliding material for Hubble to see.
The relativistic jet erupting from the accretion disk of the supermassive black hole thought to reside at the core of galaxy NGC 3862 is one of the most studied and therefore best understood. It’s also one of the few active galaxies with jets observed in visible light. It appears to stream out of the accretion disk at speeds several times the speed of light, but this is just a visual illusion referred to as superluminal motion created by the combination of insanely fast velocities and our line of sight being almost on point. It forms a narrow beam hundreds of light-years in length that eventually begins to spread out like a cone, before forming clumps at around 1,000 light-years. Clumps scientists study looking for clues pointing to facts they can use to learn more about these plasma jets and the cosmos.
Astronomers have observed knots of material being ejected from dense stellar objects previously during the human journey to the beginning of space and time. This is one of the few times they have detected knots with an optical telescope thousands of light-years from a supermassive black hole. It’s the certainly the first time we have detected a rear-end collision between separately ejected knots in a relativistic jet.
“Something like this has never been seen before in an extragalactic jet,” said Eileen Meyer of NASA’s Space Telescope Science Institute (STScI). “As the knots continue merging they will brighten further in the coming decades. This will allow us a very rare opportunity to see how the energy of the collision is dissipated into radiation.”
What would cause successive jets of material to achieve varying speeds? One theory involves the idea of material falling onto the supermassive black hole being superheated and ejected along its spin axis. Ejected material is constrained by the powerful magnetic fields surrounding the monster black hole into a narrow beam. If the flow of falling material isn’t perfectly smooth, knots are ejected in a string, rather than a continuous beam or steady hose.
It’s possible knots ejected later travel through a less dense interstellar medium, which would result in varying speeds. In this scenario, a knot launched after another knot would eventually catch up and rear-end it.
Beyond learning knots of material ejected in plasma jets erupting from the accretion disk of a supermassive black hole sometimes rear-end each other, astronomers are interested in this second case of superluminal motion observed in jets hundreds, thousands of light-years from the source supermassive black hole. This indicates the jets are still moving at nearly the speed of light at distances rivaling the scale of the host galaxy and still contain tremendous energy. Understanding this could help astronomers determine more about the evolution of galaxies as the cosmos ages, including our own Milky Way.
Astronomers are also trying to figure out why galaxy NGC 3862 is one of the few they have detected jets in optical wavelengths? They haven’t been able to come up with any good theories on why some jets are detected in visible light and others aren’t.
Work goes on
Work at the institute continues. Meyer is currently working on additional videos using Hubble images of other relativistic jets in nearby galaxies to try to detect superluminal motion. This is only possible due to the longevity of the Hubble Space Telescope and ingenuity of engineers and scientists from NASA and the ESA. Hopefully, they could discover more clues to answer these questions and other mysteries gnawing at the corner of my mind.
Watch this video made by Eileen Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Maryland using archival data from two decades of Hubble Space Telescope observations of galaxy NGC 3862.
Read and learn more about how astronomers study the formation of stars in the Milky Way.
Take the space voyage of NASA.
Read and learn more about relativistic jets here.
Learn more about the discoveries made by the ESA.
Learn more about galaxy NGC 3862 here.
Learn what astronomers have discovered about supermassive black holes.
Discover and learn more about superluminal motion here.
Discover NASA’s Space Telescope Science Institute (STScI).
Take the space journey of the Hubble Space Telescope here. | 0.858843 | 3.885527 |
Titan, Saturn’s largest moon is littered with massive dunes ranging from hundreds of feet in height to hundreds of miles in length. The sheer enormity of the dunes has baffled scientists who were studying the formation of these dunes. Titan has a dense atmosphere hydrocarbon lakes filled with liquid methane and ethane. Titan is the only heavenly object in the solar system besides Venus, Mars and Earth to have wind-blown dunes on its surface. However the composition of these dunes is completely different from the ones we have on Earth, Venus or Mars. While the dunes on Earth or Mars are mainly silicates, the dunes on Titan are made of hydrocarbons or possibly water ice covered with a sooty layer of organic materials. Scientists have been able to establish this fact after analyzing loads of data obtained from the Cassini orbiter.
Titan is a moon which orbits Saturn; it has many things which are similar to Earth. It has an atmosphere which is mainly composed of Nitrogen. However there is no Oxygen in Titan’s atmosphere. Titan is also the only moon in the solar which has liquid methane on its surface. Titan also has dunes much similar to sand dunes which are seen on Earth. Titan is also lashed by heavy winds which blow on the surface of Titan’s dunes which looks as if it is facing the opposite direction of the wind.
When Cassini sent pictures of Titan’s surface littered with gigantic dunes, astronomers were amazed by the sheer size of these dunes. A team of astronomers led by the Texas A&M University geology professor Ryan Ewing found these dunes shifting places in much the same way as the sand dunes on Earth’s largest deserts. Studying the data sent by the Cassini spacecraft which makes trips across the moon, astronomers found that these dunes were 300 feet high and took almost 3000 Saturn years to form which is roughly 90,000 Earth years. The wind conditions on the Saturn’s moon are much akin to the changing seasons on Earth. The findings of the Research Team were published in the current issue of Nature Geoscience. | 0.806061 | 3.364358 |
Our Very Own Black Hole
About the Milky Way
The Milky Way is a vast spiral, similar to our neighbor the Andromeda galaxy, shown in the photo. From our perch in one of the spiral arms, we can see the Milky Way as a great band of stars across the sky (provided we are far from an urban area).
The Andromeda galaxy, similar to our own Milky Way. (image credit: NRAO/NSF)
This photo clearly shows the dust lanes looking towards the center of the Milky Way galaxy. These dust lanes obscure the center of the galaxy in visible light. (photo credit: Dave Palmer)
Where is the center of the Milky Way? Astronomers answered this question by carefully mapping the distribution of stars, and by 1930 they placed the center in the constellation Sagittarius, near its border with Scorpio. Looking in this direction with an optical telescope—all that was then available—revealed nothing of the center, which is totally obscured in the visible spectrum by broad lanes of dust, as shown in the photo. The size of these dust particles is approximately the same as the wavelength of visible light; therefore, this light is strongly scattered. Telescopes using light with a larger wavelength were clearly needed, and they were not long in coming.
This radio image, made at a wavelength of 3.6 cm, shows the extremely compact radio source-- the bright spot--at the center of the Milky Way galaxy. The spiral pattern is made by ionized gas that is orbiting the object in the center. (image credit: NRAO/NSF)
Radio astronomy began in 1930 when electrical engineer Karl Jansky, investigating radio static, found a source of radio noise in Sagittarius. At much shorter wavelengths, infrared observing technology developed as well, and both the radio and infrared results showed a highly localized energy source at the same location.
Fast forwarding to 1971, Martin Rees and Donald Lynden-Bell, both of the University of Cambridge , hypothesized that a black hole at the center of the galaxy could explain the intense radio source observed there. The mechanism is the acceleration of charged particles spiraling into the black hole, since accelerated charges produce electromagnetic radiation. Then, in 1981, Mike Watson, of Leicester University , using the Einstein X-ray Observatory, found well-defined sources of x-rays very close to the galactic center. In fact, x-ray emission is predicted to occur very close to a black hole, due to heating of the accretion disk of matter in orbit about the black hole. However, the x-ray energy was much fainter than expected—a puzzle to this day.
In a quite different approach, infrared astronomers began in about 1980 to explore the dynamics of both gas and individual stars orbiting the presumed black hole. The idea was right out of introductory physics—the orbit and period of an object moving in a gravitational field determine the mass of the object whose gravity produces the orbit. (see sidebar)
v2/r = GMc/r2
We can solve for Mc:
Mc = v2r/G
So by measuring the velocities of objects in orbit, or equivalently their periods, we can find the mass of the central object.
We have used Newton 's theory of gravity to do this calculation. For objects close to a black hole, it may be necessary to include corrections due to Einstein's theory of general relativity, but the principle is the same—measuring the orbital parameters enables one to determine the central mass.
Motion of both stars and gas about the center of the Milky Way galaxy has provided strong evidence of the existence of a black hole. We'll concentrate on the investigation of the orbits of stars. Underway since about 1980, this effort is now led by Andrea Ghez's group at UCLA, which uses the Keck telescope in Hawaii . Key to the group's success is adaptive optics (see sidebar), a technique that compensates effectively for distortions due to Earth's atmosphere.
The twin Keck telescopes-- one images in the infrared and the other in visible light-atop Mauna Kea, Hawaii. (photo credit: W. M. Keck Observatory
The image, made with infrared light, shows the region within about a tenth of a light-year of the galactic center, with the observed positions of stars for the past nine years superimposed on the most recent image (for comparison, the diameter of the Milky Way is about 100,000 light years). A yellow five-pointed star marks the center of the galaxy, which coincides with the intense, compact radio source mentioned above. This point appears to be at rest—its motion against the background of extremely distant objects (quasars) is accounted for by the Sun's rotation around the center of the galaxy.
Infrared image of stellar orbits around the object at the center of the Milky Way. The image shows approximately the innermost three light years of our galaxy. Note the short periods of these stars, which indicate a central mass of 3.7 x 10 6 suns. (This image was created by Professor Andrea Ghez and her research team at UCLA and are from data sets obtained with the W. M. Keck Telescopes.)
A radiotelescope at the National Radio Astronomy Observatory in Green Bank, West Virginia. (photo credit: NRAO/NSF)
The closest-in star, shown in various shades of red, has completed more than three-quarters of an orbit during the time of observation. At the distance of closest approach—slightly larger than the radius of Pluto's orbit—it is moving at 4% of the speed of light. To bend an object with such a huge velocity into this tight orbit requires an extraordinary central mass, which the Ghez group has determined to be 3.7 million suns.
As for the size of the black hole, results from recent radio astronomy indicate that this object is about the size of about one Earth-orbit, ruling out alternatives and establishing that it is a black hole. The data in this study came from combining the observations of ten different radio telescopes, at locations ranging from Hawaii , across the continental U.S. , and the U.S. Virgin Islands. This system, known as the Very Long Baseline Array (VLBA), provides the resolution—the ability to see fine detail—of one extremely large telescope.
Although the black hole at the center of the Milky Way is now well-established, a question remains about the stars in this region. The Ghez group has identified young stars nearby, but the strong tidal forces near a black hole make it seem an unlikely place for star formation, leading to the hypothesis that these young stars formed further out. On the other hand, x-ray astronomers, working with the satellite observatory Chandra, determined the size distribution of these young stars and ruled out the possibility that they were formed away from the center. This question is still unresolved.
Another question is how a compact object with a mass of 3.7 million suns would form. But it seems to have happened frequently, since astronomers have concluded that a supermassive black hole resides at the center of most if not all galaxies.
UCLA Galactic Center Group
National Radio Astronomy Observatory
Chandra X-ray Observatory
The intense radio source at the center of the galaxy. Its size is about the same as the orbit of Earth. (Image courtesy of NRAO/AUI) | 0.900671 | 3.938575 |
Supernovas are among the biggest blasts in the known universe. The star explosions release a burst of radiation that can outshine an entire galaxy and span across several light-years. But now, scientists have figured out how to fit supernovas in a lab ... with lasers.
Researchers have simulated these violent stellar eruptions in a scaled-down fashion to help solve a mystery about the shape of supernova leftovers.
When a star goes supernova, it leaves behind a skeleton made of expanding dust and gas that astronomers call a remnant. Some supernova remnants, like the famous Cassiopeia A, do not expand uniformly through space, but instead produce puzzling shapes filled with knots and twists. [Supernova Photos: Great Images of Star Explosions]
To investigate why these bizarre kinks form, scientists from the University of Oxford designed a method to recreate supernova explosions with lasers 60,000 billion times more powerful than a regular classroom laser pointer. Using this technique, the team of scientists, led by Gianluca Gregori, could observe the blast up close instead of from thousands of light-years away.
Supernovas can happen two different ways. The first kind occurs when one star sucks matter away from another nearby star. As the star gets bigger, it becomes unstable and explodes. Supernovas also happen near the end of a star's life. As the star's core runs out of fuel, it starts sucking in the surrounding matter. The core gets so heavy that it collapses under its own gravitational force and explodes.
"The experiment demonstrated that as the blast of the explosion passes through the grid, it becomes irregular and turbulent, just like the images from Cassiopeia," Gregori, professor of physics at the University of Oxford, said in a statement.
The researchers, who published their findings in the journal Nature Physics on June 1, also confirmed that the turbulence the blast experiences increases the strength of the magnetic fields often found in supernova remnants. The team thinks their experiments could provide some insight into how magnetic fields were first created.
The study of supernovas has already revealed valuable information about the history of the universe. The explosions have provided evidence that the universe is expanding, and they constitute a record of how materials spread around space; elements from exploded stars are found on Earth, and the material a star spews when it explodes can become the source of a new star. | 0.810716 | 3.858993 |
Venus is one of the planets in our solar system we know the most about. This is because it is very close to earth, which allowed ancient astronomers to study it early and also makes it easier to send probes to study it or use telescopes to take pictures of it.
There are many interesting things about Venus, so let’s get started.
Fun and interesting facts about Venus
1. Venus can be seen from Earth with the naked eye
You don’t need any special equipment to see Venus in the night sky. Because it is close to Earth and it is very bright, it can be seen with just your eyes, however, if you don’t know what you are looking for, it is easy to confuse it with a star. In fact, for many years, ancient people thought it was two different stars. During history, some people have even reported seeing Venus during daylight.
2. Venus and Earth are almost equal in length
It is surprising how similar in size are Venus and Earth. Venus diameter is barely a few miles shorter than Earth’s and its mass is about 81% that of Earth’s. These similarities have earned Venus the title of “Earth’s sister planet”
3. On Venus, one day is longer than one year
Venus rotation is very slow and it takes it 243 of our earth days to complete one single rotation (a day). Meanwhile, the planet still moves around the sun and it takes 225 earth days to do so, meaning that Venus years are longer than it’s days.
4. Venus is the hottest planet in the solar system
The average temperature on Venus’ surface is 462°C (863°F). Because of these high temperatures, all the water molecules that Venus might have had many millions of years ago have now evaporated and the planet is now inhabitable.
5. Venus rotates in a different direction compared to other planets
Most planets in the solar system rotate counter-clockwise, but Venus rotates in the other direction. Some scientists think this could have happened because of an object that impacted Venus a long time ago and changed its rotation. The only other planet that rotates in the same direction is Uranus.
6. The Romans named Venus after a goddess
It is known that Romans knew of the existence of at least four planets besides Earth. Because of its brightness, they decided to name Venus after their goddess of love and beauty. It is the only planet that was named after a female goddess.
7. Venus could have looked like Earth in the past
Astronomers have the theory that at some point in the past Venus could have been even more similar to Earth and even had an ocean full of water. Because it’s climate changed, Venus went through transformations that turned it into the inhabitable planet that is today and all the water it once had has now evaporated.
8. Venus doesn’t have a moon
Venus is one of the two planets in the solar system that do not have a moon. The other is Mercury. It is possible their closeness to the sun is the reason why neither of these planets could hold a moon.
9. All craters and mountains on Venus have female names
Following the female naming convention for the planet, all the geological places that have been located and categorized on Venus have female names. Mountains are named after female goddesses while craters are named after famous women or simple use a female first name.
Venus Fact Sheet
|Radius||6,051.8±1.0 km (0.9499 Earths)|
|Surface area||4.6023×108 km2 (0.902 Earths)|
|Volume||9.2843×1011 km3 (0.866 Earths)|
|Mass||4.8675×1024 kg (0.815 Earths)|
|Gravity||8.87 m/s2 or 0.904g|
|Rotational period (One Venusian day)||243.025 earth days|
|Orbital period (Time it takes to go around the sun)||224.701 earth days (1.92 Venus solar day)|
|Surface temperature||462°C (737 K)|
|Atmospheric composition||96.5% carbon dioxide|
0.015% sulfur dioxide
Frequently asked questions about Venus
Is Venus the closest planet to Earth?
Because orbits around the sun are elliptical, planets don’t maintain a constant distance from each other. Sometimes they can be closer and sometimes they are farther away. Venus closest distance to Earth is 38 million kilometers (24 million miles) and it’s farthest it is 261 million kilometers (162 million miles) away. When you compare that to our other neighbor, Mars, whose distance is 56 million kilometers (35 million miles) when it is closest and 401 million kilometers (249 million miles) at its farthest and you could say that on average Venus is the closest planet to Earth.
Why is Venus brown/red/orange?
Venus gets its color from a combination of factors. First, the surface is covered with volcanic rocks which give Venus a brownish/orange background. On top of that, the atmosphere is composed mostly of carbon dioxide and sulphuric acid, giving it a light yellow tone. Most of the pictures you see have been retouched to emphasize some of the planet’s characteristics. If you were to see it with your own eye, you would see a light-yellow planet.
How long would it take to get to Venus?
The travel distance between two planets constantly changes because they are moving and they are at different points in their respective orbits. It is difficult to say how much time it would take to get to Venus because it depends on when you launch and where the planets are located at that time, but the latest spacecraft that was sent, the ESA Venus Express, took five months to get there. In 1961, a Soviet spacecraft made the trip in only 97 days (about three months).
Have humans ever traveled to Venus?
No. A manned mission to Venus has never been attempted, however, several unmanned probes have been sent to orbit and explore Venus successfully.
Why is Venus called the “morning star”/”evening star”?
Because of its brightness, ancient civilizations thought Venus was a star. In fact, because Venus sometimes appears at sunset and sometimes at sunrise depending on where it is in its orbit, they thought it was two different stars. The Greeks named them Phosphoros and Hesperus (star of the evening) and the name of the “morning star” and “evening star” stuck from there even after scientists realized it was a single object and it was a planet instead of a star.
Why is Venus hotter than Mercury?
Since Mercury is closer to the Sun than Venus, it would be easy to assume the first would be hotter, but that’s not true. The atmosphere in Venus is thick and made of carbon dioxide. This creates an effect called greenhouse effect, containing the heat and therefore raising the planet’s temperature.
How many craters does Venus have?
Venus is one of the objects with the most craters in the Solar System. Currently, there are 900 named craters on Venus, all of them have been named using female names. The biggest crater on Venus is Mead, named after anthropologist Margaret Mead. It has a diameter of 280 kilometers (174 miles).
What’s the biggest mountain on Venus?
The tallest mountain on Venus is Skadi Mons, with an approximate height of 6.4 km (4.0 miles) from base to peak. In comparison, that is 1.8 km (1.12 miles) taller than Mount Everest (also from base to peak). | 0.821884 | 3.113491 |
|Ceres is a dwarf planet located in the Asteroid belt, between the orbits of Mars and Jupiter. It is the only object in the Asteroid belt which is rounded by its own gravity, being the largest object of the Asteroid belt it is one-third of the total mass of the Asteroid belt. The diameter is 945km, which makes it the 33rd largest object in our solar system and the largest object in the Asteroid belt.|
Ceres was discovered by Giuseppe Piazzi in 1801 and after being spotted it became the first object in the asteroid belt to be discovered. Later, in 2015, Ceres became the first dwarf planet to receive a visit from a spacecraft(Dawn spacecraft).
When Ceres was discovered it was classified as a planet but later scientists called it a dwarf panet, A planet is an object that orbits the Sun in an elliptical orbit, has compounded its matter in a spherical shape, and has cleared its orbit of other debris. While, a dwarf planet also orbits the Sun, has compounded its matter in a spherical shape, but has not cleared its orbit of other debris. Ceres has not cleared the orbit of other debris, that’s why it is a dwarf planet.
It take 4.6 Earth year to make a trip around the Sun, however, its rotation period is 9 hours which makes it’s day length shortest in the solar system.
Ceres was formed along with the rest of the solar system about 4.5 billion years ago,and it is a embryonic planet. Embyonic planet means that it was forming but didn’t finish, this happened probably due to huge Jupiter,it prevented it to becoming a fully formed planet.
Ceres probably has a solid core and a mantle made of water ice. It is believed that Ceres is composed of 25 percent water, and if it is true Ceres have more water than the Earth.
It doesn’t have any moon and it is only dwarf panet with no Moons, other dwarf planet like Pluto and other dwarf panet have atleast one Moon.
Ceres is one of the few places in our solar system where scientists would like to search for possible signs of life. Ceres has water, and water is essential for life, so it’s possible that with this immensely important stuff and a few other conditions met, life could maybe exist there. Living things on Ceres, if they are there at all, would likely be very small microbes similar to bacteria. And while Ceres might not have living things today, there could be signs it harbored life in the past. | 0.864794 | 3.739427 |
The Sun is just one of countless stars that exist in our universe. But it’s one of the most prominent because it’s so close to us, and that’s what makes it so influential over Earth’s time of day and temperature, among other things.
Given just how bright the Sun is in our sky compared to the plethora of other stars in our universe, it can be difficult to conceptualize the thought that our Sun is far from the largest and hottest star in existence. Outer space is just so unimaginably large that some of the brightest and largest stars are incredibly distant from us, and this makes them appear dim in the night sky.
The Sun, just like any other star, is a hot, swirling ball of gas and plasma in which a process called fusion takes place. The explosive forces happening in the Sun’s core are continuously pressing outward, while the forces of gravity fight against that same explosive force. As these forces fight one another, it creates pressure, and scientists say the Sun’s pressure equates to 260 billion times that of the Earth’s atmospheric pressure. All that pressure generates heat, and that’s what helps the Sun reach its blistering 15 million decrees Celsius.
So what’s happening in the Sun’s core as fusion takes place? Essentially, it’s so hot that hydrogen atoms become completely ionized. Their electrons are ripped from their atoms and protons, creating a dense glob of subatomic particles that, under the excruciating pressure, fuse together to form helium atoms. In fact, the Sun transforms around 700 million tons of hydrogen into 695 tons of helium every day, with the remaining 5 tons being released as energy.
The Sun is also comprised of high intensity magnetic fields. If you’ve ever seen those beautiful NASA solar observatory images, then you’ll witnessed those mind-boggling loops that feed out of the Sun’s surface. These are essentially magnetic fields, and they can sometimes short-circuit, sending a blast of energy equating up to 10% of the Sun’s total power output out in the form of a solar flare.
Given just how essential the Sun is to life on Earth, this is just one reason why NASA studies is to vividly. We still have many questions about the Sun, and with a little luck, perhaps we’ll answer them soon enough. | 0.804803 | 3.445753 |
« ՆախորդըՇարունակել »
utmost importance to know the position of a cape, with all the accuracy which astronomical means admit of. In a hydrographical chart all the points should be equally well determined; for every one of them may serve as a point of departure or ob. servation; and there is none which is not connected with others: while, on the contrary, the maps which represent the interior of a country possess great merit, when they offer a certain number of places whose position has been astronomically fixed.
If it is desirable that the Spanish possessions in .
the interior of America should not be for some time surveyed with the same minute accuracy which has been displayed on the coast; if in the actual state of things it would be more useful merely to execute a provisory undertaking, founded on the use of sextants and chronometers, on lunar distances, on observations of satellites, and eclipscs, it would be of no less importance to unite to these purely astronomical means such other means as are furnished by the nature of the country and the great elevation of its insulated summits. When we know exactly the absolute height of these summits, whether by means of the barometer, or by geometrical operations, angles of altitudes and azimuths taken with the rising or setting sun may serve to connect these mountains with points whose latitude and longitude have been sufficiently verified. This method
furnishes perpendicular bases; and in estimating how much we may be deceived in the measurement of each base, it is easy to conclude by false suppositions what influence this error may have on the astronomical position either of the mountain itself, or of the other points which depend on it. An exact knowledge of the inferior limit of perpetual snow will often afford the same advantages as the measurement of an insulated summit. This is the method employed by me to verify the difference of longitude between the capital of Mexico and the port of Vera Cruz. Two great volcanos, that of la Puebla, called Popocatepetl, and the peak of Orizava, both visible from the platform of the ancient pyramid of Cholula, serve to connect two places distant from one another more than 16,000 * toises. The union of two geometrical measurements of the mountains, of the azimuths and angles of altitudes calculated by M. Oltmanns, have given the port of Vera Cruz 0 1 1/ 32” to the west of Mexico, while from purely astronomical observations there results a difference of meidians of 0 1 1' 47". In modifying the former
result by several secondary operations at the py-,
ramid of Cholula, we find even 0° 1 1/41, 37; so that in this particular case, on a distance of three degrees, the method of azimuths was only 7" false in timef.
* About 102,400 feet English, Trans. t Mémoire astronomique sur la différence des meridiens
These same insulated summits, situated in the midst of a vast plain, offer a still surer method of determining in a short space of time, to within a few seconds, the longitude of a great number of neighbouring places. Luminous signals, produced by the deflagration of a small quantity of gunpowder, may be observed at great distances by persons provided with proper means for finding and preserving the true time. Cassini de Thury and Lacaille were the first who successfully employed this method of luminous signals. M. de Zach has recently proved by his operations in Thuringia, that in favourable circumstances it will furnish in a few minutes positions comparable for accuracy to the results of a great number of observations of satellites of solar eclipses. In the kingdom of New Spain the signals might be given at Iztaccihuatl, or Siera Nevada of Mexico; on the rock called The Monk, an insulated summit of the volcano of Toluca, which I reached 29th September, 1803; on la Malriche near Tlascalar; on the Coffre de Perotte; and on other mountains whose summits are accessible, and which are all elevated more than from three to four thousand metres* above the level of the sea.
entre Mexico et Vera Cruz, par MM. Oltmanns et Hum-
p. 445, 454, 458.) -
s & -* - — — —
The Spanish government having with extraordinary liberality made the most important sacrifices for the perfection of nautical astronomy, and for accurate surveys of the coast, we may expect that its next concern will be the geography of its vast American dominions, for which the royal marine would furnish both instruments, and astronomers skilled in observations. The school for mines of Mexico, in which mathematics are studied in a solid manner, spreads over the surface of this vast empire a great number of young men animated with the noblest zeal, and capable of using the instruments with which they might be entrusted. It is by analogous means that the English East India Company have surveyed a territory whose surface equals that of England and France united *. We live no longer in times when governmentsdread to expose to foreign nations their territorial wealth in the Indies. The present king of Spain gave orders to publish, at the expense of the state, the survey of the coasts and ports; without fearing that the most minute plans of the Havannah, of Vera Cruz, and the mouth of the Rio Plata, should fall into the hands of the foreign nations whom events have made enemies of Spain. One of the finest maps, drawn up by the Deposito Hydrografico of Madrid, contains the most valuable details regarding the interior of Paraguay; details founded on the operations of the officers of the royal marine employed to settle the boundaries between the Portuguese and Spaniards. With the exception of the maps of Egypt and of some parts of the East Indies, the most accurate work which exists, of any European continental possession out of Europe, is the map of the kingdom of Quito, drawn up by Maldonado. Every thing proves, that for these fifteen years past the Spanish government, far from dreading the progress of geography, has published all the interesting materials which it possessed on the colonies in the two Indies. Having indicated the means, apparently the most proper, for speedily completing the maps of the kingdom of New Spain, I shall give a succinct analysis of the materials employed by me in the geographical work which I offer to the public. The general map of the kingdom of New Spain is drawn up, as all the other maps drawn up by me in the course of my expedition are, according to the projection of Mercator, with increasing latitudes. This projection has the advantage of shewing at once the true distance of one place from another; it is at the same time the most agreeable to the navigators who visit the colonies, and who, in fixing the position of their vessel by two mountains seen without difficulty, would wish their survey to correspond with the map. If I had had to choose among the stereographic projections,
* Rennel's Hindostan, vol. i. p. 17. | 0.867467 | 3.056463 |
A new born standing in water
HERSCHEL focused on TW Hydrae, a star which is only approximately ten million years old. Located at approximately 170 light years away from Earth in the Hydra constellation, the star is still surrounded by a disk composed of dust and gas which could give rise to a whole planetary system in the next millions years.
HERSCHEL detected great quantities of cold water vapour (approximately -170ºC) in this disk. This vapour could have been produced by the star's strong radiations by spraying ice which covered the dust orbiting the star.
“The water vapour changes the star's light detected by HERSCHEL, thus revealing the presence of ice which would have been undetectable in the disk” Olivier La Marle, astrophysics program scientist at CNES, explained.
Double hit for comets
The data were obtained thanks to the HERSCHEL's HIFI spectrometer which was recently very successful confirming that some comets of the Solar System contain water ice similar to the Earth's water.
HIFI, in which CNES is participating through different institutes, supports the theory that our planet could come from a specific type of comets, formed in the outer areas of our solar system.
However, thanks to simulations, astronomers admitted that there is around TW Hydrae enough ice water to build a real stock of comets, enough to fulfil several thousands of terrestrial oceans.
“This theory started out with the HERSCHEL recent results and suggested that the water on Earth could result from a ice comet bombardment coming from the original disk” Olivier concluded.
The next step for the team: study 3 other young systems in which planets could form to also detect water ice in significant quantity. | 0.911451 | 3.526917 |
China’s Chang’e 3 landed on Mare Imbrium (Sea of Rains) just east of a 450 m diameter impact crater on 14 December 2013. Soon after landing, a small rover named Yutu (or Jade Rabbit in English) was deployed and took its first tentative drive onto the airless regolith.
At the time of the landing LRO’s orbit was far from the landing site so images of the landing were not possible.
Ten days later on 24 December, LRO approached the landing site, and LROC was able to acquire a series of six LROC Narrow Angle Camera ( NAC ) image pairs during the next 36 hours (19 orbits). The highest resolution image was possible when LRO was nearly overhead on 25 December 03:52:49 UT (24 December 22:52:49 EST). At this time LRO was at an altitude of ~150 km above the site, and the pixel size was 150 cm.
The rover is only about 150 cm wide, yet it shows up in the NAC images for two reasons: the solar panels are very effective at reflecting light so the rover shows up as two bright pixels, and the Sun is setting thus the rover casts a distinct shadow (as does the lander). Since the rover is close to the size of a pixel, how can we be sure we are seeing the rover and not a comparably sized boulder? Fortuitously, the NAC acquired a “before” image (M1127248516R) of the landing site, with nearly identical lighting, on 30 June 2013. By comparing the before and after landing site images, the LROC team confirmed the position of the lander and rover, and derived accurate map coordinates for the lander (44.1214°N, 340.4884°E, 2640 meters elevation ).
The lander set down about 60 meters east of the rim of a 450 meter diameter impact crater (40 meters deep) on a thick deposit of volcanic materials. A large scale wrinkle ridge (~100 km long, 10 km wide) cuts across the area and was formed as tectonic stress caused the volcanic layers to buckle and break along faults. Wrinkle ridges are common on the Moon, Mercury and Mars.
Lunar mare basalts are divided into two main spectral (color) types: “red” and “blue” (blue is perhaps a misnomer, think “less red”). Basalts on the Moon (same on Earth) are composed mainly of two minerals, pyroxene and plagioclase, though olivine and ilmenite can sometimes occur in significant amounts. The presence of ilmenite (FeTiO 3 ) results in lower reflectance and a “lessred” color thus the blue basalts. The landing site is on a blue mare (higher titanium) thought to be about 3.0 billion years old. The boundary (black arrows in above WAC mosaic) with an older (3.5 billion years) red mare is only 10 km to the north. | 0.820972 | 3.659492 |
It stands to reason that if there are exoplanets orbiting stars in our own galaxy, then there would also be exoplanets in other galaxies. However, other galaxies are too far away to detect exoplanets by any of the means we currently have. Now researchers from the University of Oklahoma claim to have spotted exoplanets in another galaxy using a technique called gravitational microlensing. These planets seem to have rather odd behavior, though.
In our galaxy, we look for exoplanets by observing the stars they orbit. We can detect small wobbles in the star as planets move around them, but this only works for larger planets. The transit method monitors stars for small dips in luminance from planets passing in front of them. This can detect smaller planets, but not all solar systems are oriented in such a way that planets pass in front of the star from our perspective. Gravitational microlensing is a completely different approach, predicted by general relativity. Just like a glass lens can magnify an object, the bending of space by gravity can amplify distant energy sources.
The lensing comes from an active galaxy with a black hole (known as a quasar) about 3.8 billion light years away. The intense gravity from the quasar bends light toward the Milky Way, bringing previously unseen objects into view. The team used the Chandra X-ray Observatory to scan the galaxy (called RXJ1131-1231, in the center of the above image), finding signals that could be planets.
Astrophysicist Xinyu Dai says the technique can detect objects as small as Earth’s moon or as large as Jupiter. Gravitational microlensing is the only technique known that has any hope of detecting planets at such a great distance, even in “science fiction” scenarios, according to the researchers.
The data from the team’s x-ray observations paints a picture of a galaxy very unlike ours. They estimate there are 2,000 planets for every star, and that many of the planets don’t remain bound to individual stars. Instead, they drift through space or hop from one star to another. Could there be trillions of “rogue” planets in this galaxy? That would be wild, to say the least.
The scientific community is still skeptical of the interpretation of this data, but everyone agrees it’s very interesting. Some alternative explanations of the data include clusters of brown dwarf stars or dust clouds. Other experts will be pouring over the data in an attempt to either validate or refute these claims. Either way, there’s clearly something to see in RXJ1131-1231. | 0.843814 | 3.941465 |
Rare supernova extinguishes star at record speed — Using data collected by the Kepler space telescope, an international team of astronomers led by Brad Tucker from Australian National University has documented the death throes of a star located 1.3 billion light-years away. Known as KSN 2015K, this unprecedented FELT reached its maximum brightness in just 2.2 days, which is 10 times faster than standard supernovae.
~ Or it’s a pretty full-on war in a distant galaxy …
Brown planet reopens debate — Scientists have discovered a planet a lot like Jupiter orbiting a dim star, if you can even call it a star – it’s nothing like our Sun. The finding once again makes us wonder: what is a planet, anyway?
~ I’m going with ‘big round thing in space that orbits and is not on fire’.
Alien DNA — If an alien life form is alien, how will we know what it is? DNA and RNA are the building blocks of life on Earth, but the molecules of life might differ substantially on another planet. So if scientists combing, say, the potentially habitable waters of Jupiter’s moon Europa were to stumble across a new life form, how could they know what they had discovered? Aha – scientists at Georgetown University suggest a method for identifying alien life using modern genome sequencing technology.
~ Please open your carapace, sir and/or madam, we would like to take a swab.
Slippery-rough engineered surface harvests water — A slippery rough surface (SRS) inspired by both pitcher plants and rice leaves outperforms state-of-the-art liquid-repellent surfaces in water harvesting applications, according to a team of researchers at Penn State and the University of Texas at Dallas.
~ Then we can bottle the water and add the little bits of plastic.
Cat-like ‘hearing’ with device tens of trillions times smaller than human eardrum — Researchers are developing atomically thin ‘drumheads’ tens of trillions of times thinner than the human eardrum able to receive and transmit signals across a radio frequency range far greater than what we can hear with the human ear. Their work will likely contribute to making the next generation of ultralow-power communications and sensory devices smaller and with greater detection and tuning ranges.
~ Have to go – I just heard my cat.
NVIDIA’s 2 Petaflop DGX-2 AI Supercomputer with 32GB Tesla V100 and NVSwitch Tech — NVIDIA CEO Jensen Huang recently announced a number of GPU-powered innovations for machine learning, including a new AI supercomputer and an updated version of the company’s powerful Tesla V100 GPU that now sports a hefty 32GB of on-board HBM2 memory. NVIDIA claims NVSwitch is five times faster than the fastest PCI Express switch and offers an aggregate 2.4TB per second of bandwidth.
~ All the better to monitor us with.
Terahertz chips — Following three years of extensive research, physicists have created technology that will enable our computers – and all optic communication devices – to run 100 times faster through terahertz microchips.
Bionic wheelbot — Using eight reconfigurable legs, the BionicWheelBot can creepily crawl along the ground, but then transform into a wheel and roll at an alarming speed.
~ It can tiptoe through tricky terrain then quickly roll through the flat bits.
A paperlike LCD is thin, flexible, tough and cheap — Optoelectronic engineers have manufactured a special type of LCD that is paper-thin, flexible, light and tough. With this, a newspaper could be uploaded onto a flexible paperlike display that could be updated as fast as the news cycles. It sounds futuristic, but scientists reckon it will be cheap to produce, perhaps only costing US$5 for a 5-inch screen.
~ I can almost guarantee the last word in its description will be gone by the time this becomes available.
Sewage sludge leads to biofuels breakthrough — Researchers have discovered a new enzyme that will enable microbial production of a renewable alternative to petroleum-based toluene, a widely used octane booster in gasoline that has a global market of 29 million tons per year.
~ Isn’t toluene also carcinogenic?
13,000-year-old human footprints found off Canada’s Pacific coast — Human footprints found off Canada’s Pacific coast may be 13,000 years old, according to a new study. The finding adds to the growing body of evidence supporting the hypothesis that humans used a coastal route to move from Asia to North America during the last ice age.
~ So that rules out flying.
Secrets of famous Neanderthal skeleton La Ferrassie 1 revealed — Anthropologists have provided new insights on one of the most famous Neanderthal skeletons, discovered over 100 years ago: La Ferrassie 1. Nearly all of the fractures were made post-mortem. La Ferrassie 1 was an old man (likely over 50 years old) who suffered various broken bones during his lifetime and had ongoing respiratory issues when he died. The skeleton was found in a burial pit and dated to between 40,000 and 54,000 years old.
~ The weight of sediments snapped the bones. | 0.870677 | 3.319848 |
A large dip in the star’s brightness suggests something massive is orbiting the fiery body.
Over the weekend a call went out to astronomers to point their telescopes toward star KIC 8462852, which is also known as Tabby’s Star or the “Alien Megastructure” star. That’s because researchers suspected the star was beginning to dim—something astronomers have been waiting to observe since 2015, reports Sarah Fecht at Popular Science.
Dips in brightness of stars usually represent some type of body—like a planet—orbiting a distant star. Since Kepler Spacecraft’s launch in 2009, the mobile observatory trained its sights on the brightness of stars to catch these blips of light, reports Marina Koren at The Atlantic. But after the Kepler data was released to the public in 2011, volunteers discovered that Tabby’s star was different than the 150,000 other stars in the survey. When it dimmed, its brightness dropped by 20 percent (for reference, a Jupiter-sized planet would drop the brightness by around one percent), reports Fecht. Something massive must be circling Tabby’s star.
Researchers have been eagerly waiting for the brightness on Tabby’s star to dip again so they can get closer readings. And they’re finally getting their chance. As Loren Grush reports for The Verge, last Thursday night, astronomer Matt Muterspaugh at Tennessee State University who has been watching the star, noticed its brightness was dipping. On Friday, when it dipped further, he put the call out to the astronomy community. “As far as I can tell, every telescope that can look at it right now is looking at it right now,” he tells Grush.
The cause of that drop in dimness has long been debated. Some researchers have suggested that something massive is orbiting the star, such as a cluster of comets. In 2015, astronomer Jason Wright at Penn State suggested that the dip could be caused by a Dyson Sphere—a hypothetical alien megastructure proposed physicist Freeman Dyson in 1960. A Dyson Sphere is a massive solar-power collecting structure that Dyson suggested could have been created by advanced civilizations that, during its construction, would orbit its sun and occasionally block out its light. Dyson suggested astronomers look for these spheres to help find alien civilizations.
But before you get riled up: aliens are on the bottom of the list of plausible causes for natural phenomena.
These latest observations, however, could help researchers finally come to an answer. As Grush reports, if the cause is a comet storm, then the comets will orbit very close to the star, heating them up enough to show up in infrared images. If it is an alien megastructure, well, we’re not sure what the would look like. “That theory is still a valid one,” Muterspaugh tells Grush. “We would really hate to go to that, because that’s a pretty major thing. It’d be awesome of course, but as scientists we’re hoping there’s a natural explanation.”
Earlier this year, a team of astronomers came up with another compelling idea. They suggest that Tabby’s star ate one of its own planets sometime in the last ten millennia, an event that caused the star to shine more brightly. And now, the star is dimming down as it digests its cosmic lunch. | 0.927878 | 3.620971 |
What is space weather?
Space weather is determined largely by the variable effects of the Sun on the Earth’s magnetosphere. The basic geometry of this relationship is shown in the following diagram, with the solar wind always impinging on the Earth’s magnetic field and transferring energy into the magnetosphere. Normally, the solar wind does not change rapidly, and Earth’s space weather is relatively benign. However, sudden disturbances on the Sun produce solar flares and coronal holes that can cause significant, rapid variations in Earth’s space weather.
A solar storm, or geomagnetic storm, typically is associated with a large-scale magnetic eruption on the Sun’s surface that initiates a solar flare and an associated coronal mass ejection (CME). A CME is a giant cloud of electrified gas (solar plasma.) that is cast outward from the Sun and may intersect Earth’s orbit. The solar flare also releases a burst of radiation in the form of solar X-rays and protons.
The solar X-rays travel at the speed of light, arriving at Earth’s orbit in 8 minutes and 20 seconds. Solar protons travel at up to 1/3 the speed of light and take about 30 minutes to reach Earth’s orbit. NOAA reports that CMEs typically travel at a speed of about 300 kilometers per second, but can be as slow as 100 kilometers per second. The CMEs typically take 3 to 5 days to reach the Earth and can take as long as 24 to 36 hours to pass over the Earth, once the leading edge has arrived.
If the Earth is in the path, the X-rays will impinge on the Sun side of the Earth, while charged particles will travel along magnetic field lines and enter Earth’s atmosphere near the north and south poles. The passing CME will transfer energy into the magnetosphere.
Solar storms also may be the result of high-speed solar wind streams (HSS) that emanate from solar coronal holes (an area of the Sun’s corona with a weak magnetic field) with speeds up to 3,000 kilometers per second. The HSS overtakes the slower solar wind, creating turbulent regions (co-rotating interaction regions, CIR) that can reach the Earth’s orbit in as short as 18 hours. A CIR can deposit as much energy into Earth’s magnetosphere as a CME, but over a longer period of time, up to several days.
Solar storms can have significant effects on critical infrastructure systems on Earth, including airborne and space borne systems. The following diagram highlights some of these vulnerabilities.
Effects of Space Weather on Modern Technology. Source: SpaceWeather.gc.ca
Characterizing space weather
The U.S. National Oceanic and Atmospheric Administration (NOAA) Space Weather Prediction Center (SWPC) uses the following three scales to characterize space weather:
- Geomagnetic storms (G): intensity measured by the “planetary geomagnetic disturbance index”, Kp, also known as the Geomagnetic Storm or G-Scale
- Solar radiation storms (S): intensity measured by the flux level of ≥ 10 MeV solar protons at GEOS (Geostationary Operational Environmental Satellite) satellites, which are in synchronous orbit around the Earth.
- Radio blackouts (R): intensity measured by flux level of solar X-rays at GEOS satellites.
Another metric of space weather is the Disturbance Storm Time (Dst) index, which is a measure of the strength of a ring current around Earth caused by solar protons and electrons. A negative Dst value means that Earth’s magnetic field is weakened, which is the case during solar storms.
A single solar disturbance (a CME or a CIR) will affect all of the NOAA scales and Dst to some degree.
As shown in the following NOAA table (click on table to enlarge), the G-scale describes the infrastructure effects that can be experienced for five levels of geomagnetic storm severity. At the higher levels of the scale, significant infrastructure outages and damage are possible.
There are similar tables for Solar Radiation Storms and Radio Blackouts on the NOAA SWPC website at the following link:
Another source for space weather information is the spaceweather.com website, which contains some information not found on the NOAA SWPC website. For example, this website includes a report of radiation levels in the atmosphere at aviation altitudes and higher in the stratosphere. In the following chart, “dose rates are expressed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x.”
You’ll also find a report of recent and upcoming near-Earth asteroids on the spaceweather.com website. This definitely broadens the meaning of “space weather.” As you can seen the in the following table, no close encounters are predicted over the next two months.
In summary, the effects of a solar storm may include:
- Interference with or damage to spacecraft electronics: induced currents and/or energetic particles may have temporary or permanent effects on satellite systems
- Navigation satellite (GPS, GLONASS and Galileo) UHF / SHF signal scintillation (interference)
- Increased drag on low Earth orbiting satellites: During storms, currents and energetic particles in the ionosphere add energy in the form of heat that can increase the density of the upper atmosphere, causing extra drag on satellites in low-earth orbit
- High-frequency (HF) radio communications and low-frequency (LF) radio navigation system interference or signal blackout
- Geomagnetically induced currents (GICs) in long conductors can trip protective devices and may damage associated hardware and control equipment in electric power transmission and distribution systems, pipelines, and other cable systems on land or undersea.
- Higher radiation levels experienced by crew & passengers flying at high latitudes in high-altitude aircraft or in spacecraft.
For additional information, you can download the document, “Space Weather – Effects on Technology,” from the Space Weather Canada website at the following link:
Historical major solar storms
The largest recorded geomagnetic storm, known as the Carrington Event or the Solar Storm of 1859, occurred on 1 – 2 September 1859. Effects included:
- Induced currents in long telegraph wires, interrupting service worldwide, with a few reports of shocks to operators and fires.
- Aurorea seen as far south as Hawaii, Mexico, Caribbean and Italy.
This event is named after Richard Carrington, the solar astronomer who witnessed the event through his private observatory telescope and sketched the Sun’s sunspots during the event. In 1859, no electric power transmission and distribution system, pipeline, or cable system infrastructure existed, so it’s a bit difficult to appreciate the impact that a Carrington-class event would have on our modern technological infrastructure.
A large geomagnetic storm in March 1989 has been attributed as the cause of the rapid collapse of the Hydro-Quebec power grid as induced voltages caused protective relays to trip, resulting in a cascading failure of the power grid. This event left six million people without electricity for nine hours.
A large solar storm on 23 July 2012, believed to be similar in magnitude to the Carrington Event, was detected by the STEREO-A (Solar TErrestrial RElations Observatory) spacecraft, but the storm passed Earth’s orbit without striking the Earth. STEREO-A and its companion, STEREO-B, are in heliocentric orbits at approximately the same distance from the Sun as Earth, but displaced ahead and behind the Earth to provide a stereoscopic view of the Sun.
You’ll find a historical timeline of solar storms, from the 28 August 1859 Carrington Event to the 29 October 2003 Halloween Storm on the Space Weather website at the following link:
Risk from future solar storms
A 2013 risk assessment by the insurance firm Lloyd’s and consultant engineering firm Atmospheric and Environmental Research (AER) examined the impact of solar storms on North America’s electric grid.
U.S. electric power transmission grid. Source: EIA
Here is a summary of the key findings of this risk assessment:
- A Carrington-level extreme geomagnetic storm is almost inevitable in the future. Historical auroral records suggest a return period of 50 years for Quebec-level (1989) storms and 150 years for very extreme storms, such as the Carrington Event (1859).
- The risk of intense geomagnetic storms is elevated near the peak of the each 11-year solar cycle, which peaked in 2015.
- As North American electric infrastructure ages and we become more dependent on electricity, the risk of a catastrophic outage increases with each peak of the solar cycle.
- Weighted by population, the highest risk of storm-induced power outages in the U.S. is along the Atlantic corridor between Washington D.C. and New York City.
- The total U.S. population at risk of extended power outage from a Carrington-level storm is between 20-40 million, with durations from 16 days to 1-2 years.
- Storms weaker than Carrington-level could result in a small number of damaged transformers, but the potential damage in densely populated regions along the Atlantic coast is significant.
- A severe space weather event that causes major disruption of the electricity network in the U.S. could have major implications for the insurance industry.
The Lloyds report identifies the following relative risk factors for electric power transmission and distribution systems:
- Magnetic latitude: Higher north and south “corrected” magnetic latitudes are more strongly affected (“corrected” because the magnetic North and South poles are not at the geographic poles). The effects of a major storm can extend to mid-latitudes.
- Ground conductivity (down to a depth of several hundred meters): Geomagnetic storm effects on grounded infrastructure depend on local ground conductivity, which varies significantly around the U.S.
- Coast effect: Grounded systems along the coast are affected by currents induced in highly-conductive seawater.
- Line length and rating: Induced current increases with line length and the kV rating (size) of the line.
- Transformer design: Lloyds noted that extra-high voltage (EHV) transformers (> 500 kV) used in electrical transmission systems are single-phase transformers. As a class, these are more vulnerable to internal heating than three-phase transformers for the same level of geomagnetically induced current.
Combining these risk factors on a county-by-county basis produced the following relative risk map for the northeast U.S., from New York City to Maine. The relative risk scale covers a range of 1000. The Lloyd’s report states, “This means that for some counties, the chance of an average transformer experiencing a damaging geomagnetically induced current is more than 1000 times that risk in the lowest risk county.”
Relative risk of power outage from geomagnetic storm. Source: Lloyd’s
You can download the complete Lloyd risk assessment at the following link:
In May 2013, the United States Federal Energy Regulatory Commission issued a directive to the North American Electric Reliability Corporation (NERC) to develop reliability standards to address the impact of geomagnetic disturbances on the U.S. electrical transmission system. One part of that effort is to accurately characterize geomagnetic induction hazards in the U.S. The most recent results were reported in the 19 September 2016, a paper by J. Love et al., “Geoelectric hazard maps for the continental United States.” In this report the authors characterize geography and surface impedance of many sites in the U.S. and explain how these characteristics contribute to regional differences in geoelectric risk. Key findings are:
“As a result of the combination of geographic differences in geomagnetic activity and Earth surface impedance, once-per-century geoelectric amplitudes span more than 2 orders of magnitude (factor of 100) and are an intricate function of location.”
“Within regions of the United States where a magnetotelluric survey was completed, Minnesota (MN) and Wisconsin (WI) have some of the highest geoelectric hazards, while Florida (FL) has some of the lowest.”
“Across the northern Midwest …..once-per-century geoelectric amplitudes exceed the 2 V/km that Boteler ……has inferred was responsible for bringing down the Hydro-Québec electric-power grid in Canada in March 1989.”
The following maps from this paper show maximum once-per-century geoelectric exceedances at EarthScope and U.S. Geological Survey magnetotelluric survey sites for geomagnetic induction (a) north-south and (b) east-west. In these maps, you can the areas of the upper Midwest that have the highest risk.
The complete paper is available online at the following link:
Is the U.S. prepared for a severe solar storm?
The quick answer, “No.” The possibility of a long-duration, continental-scale electric power outage exists. Think about all of the systems and services that are dependent on electric power in your home and your community, including communications, water supply, fuel supply, transportation, navigation, food and commodity distribution, healthcare, schools, industry, and public safety / emergency response. Then extrapolate that statewide and nationwide.
In October 2015, the National Science and Technology Council issued the, “National Space Weather Action Plan,” with the following stated goals:
- Establish benchmarks for space-weather events: induced geo-electric fields), ionizing radiation, ionospheric disturbances, solar radio bursts, and upper atmospheric expansion
- Enhance response and recovery capabilities, including preparation of an “All-Hazards Power Outage Response and Recovery Plan.”
- Improve protection and mitigation efforts
- Improve assessment, modeling, and prediction of impacts on critical infrastructure
- Improve space weather services through advancing understanding and forecasting
- Increase international cooperation, including policy-level acknowledgement that space weather is a global challenge
The Action Plan concludes:
“The activities outlined in this Action Plan represent a merging of national and homeland security concerns with scientific interests. This effort is only the first step. The Federal Government alone cannot effectively prepare the Nation for space weather; significant effort must go into engaging the broader community. Space weather poses a significant and complex risk to critical technology and infrastructure, and has the potential to cause substantial economic harm. This Action Plan provides a road map for a collaborative and Federally-coordinated approach to developing effective policies, practices, and procedures for decreasing the Nation’s vulnerabilities.”
You can download the Action Plan at the following link:
To supplement this Action Plan, on 13 October 2016, the President issued an Executive Order entitled, “Coordinating Efforts to Prepare the Nation for Space Weather Events,” which you can read at the following link:
Implementation of this Executive Order includes the following provision (Section 5):
“Within 120 days of the date of this order, the Secretary of Energy, in consultation with the Secretary of Homeland Security, shall develop a plan to test and evaluate available devices that mitigate the effects of geomagnetic disturbances on the electrical power grid through the development of a pilot program that deploys such devices, in situ, in the electrical power grid. After the development of the plan, the Secretary shall implement the plan in collaboration with industry.”
So, steps are being taken to better understand the potential scope of the space weather problems and to initiate long-term efforts to mitigate their effects. Developing a robust national mitigation capability for severe space weather events will take several decades. In the meantime, the nation and the whole world remain very vulnerable to sever space weather.
Today’s space weather forecast
Based on the Electric Power Community Dashboard from NOAA’s Space Weather Prediction Center, it looks like we have mild space weather on 31 December 2016. All three key indices are green: R (radio blackouts), S (solar radiation storms), and G (geomagnetic storms). That’s be a good way to start the New Year.
See your NOAA space weather forecast at:
Natural Resources Canada also forecasts mild space weather for the far north.
You can see the Canadian space weather forecast at the following link:
4 January 2017 Update: G1 Geomagnetic Storm Approaching Earth
On 2 January, 2017, NOAA’s Space Weather Prediction Center reported that NASA’s STEREO-A spacecraft encountered a 700 kilometer per second HSS that will be pointed at Earth in a couple of days.
“A G1 (Minor) geomagnetic storm watch is in effect for 4 and 5 January, 2017. A recurrent, polar connected, negative polarity coronal hole high-speed stream (CH HSS) is anticipated to rotate into an Earth-influential position by 4 January. Elevated solar wind speeds and a disturbed interplanetary magnetic field (IMF) are forecast due to the CH HSS. These conditions are likely to produce isolated periods of G1 storming beginning late on 4 January and continuing into 5 January. Continue to check our SWPC website for updated information and forecasts.”
The coronal hole is visible as the darker regions in the following image from NASA’s Solar Dynamics Observatory (SDO) satellite, which is in a geosynchronous orbit around Earth.
Source: NOAA SWPC
SDO has been observing the Sun since 2010 with a set of three instruments:
- Helioseismic and Magnetic Imager (HMI)
- Extreme Ultraviolet Variability Experiment (EVE)
- Atmospheric Imaging Assembly (AIA)
The above image of the coronal hole was made by SDO’s AIA. Another view, from the spaceweather.com website, provides a clearer depiction of the size and shape of the coronal hole creating the current G1 storm.
You’ll find more information on the SDO satellite and mission on the NASA website at the following link: | 0.820007 | 4.002132 |
Newswise — The spectacular new camera installed on NASA's Hubble Space Telescope during Servicing Mission 4 in May has delivered the most detailed view of star birth in the graceful, curving arms of the nearby spiral galaxy M83.
Nicknamed the Southern Pinwheel, M83 is undergoing more rapid star formation than our own Milky Way galaxy, especially in its nucleus. The sharp "eye" of the Wide Field Camera 3 (WFC3) has captured hundreds of young star clusters, ancient swarms of globular star clusters, and hundreds of thousands of individual stars, mostly blue supergiants and red supergiants.
The image at right is Hubble's close-up view of the myriad stars near the galaxy's core, the bright whitish region at far right. An image of the entire galaxy, taken by the European Southern Observatory's Wide Field Imager on the ESO/MPG 2.2-meter telescope at La Silla, Chile, is shown at left. The white box outlines Hubble's view.
WFC3's broad wavelength range, from ultraviolet to near-infrared, reveals stars at different stages of evolution, allowing astronomers to dissect the galaxy's star-formation history.
The image reveals in unprecedented detail the current rapid rate of star birth in this famous "grand design" spiral galaxy. The newest generations of stars are forming largely in clusters on the edges of the dark dust lanes, the backbone of the spiral arms. These fledgling stars, only a few million years old, are bursting out of their dusty cocoons and producing bubbles of reddish glowing hydrogen gas.
The excavated regions give a colorful "Swiss cheese" appearance to the spiral arm. Gradually, the young stars' fierce winds (streams of charged particles) blow away the gas, revealing bright blue star clusters. These stars are about 1 million to 10 million years old. The older populations of stars are not as blue.
A bar of stars, gas, and dust slicing across the core of the galaxy may be instigating most of the star birth in the galaxy's core. The bar funnels material to the galaxy's center, where the most active star formation is taking place. The brightest star clusters reside along an arc near the core.
The remains of about 60 supernova blasts, the deaths of massive stars, can be seen in the image, five times more than known previously in this region. WFC3 identified the remnants of exploded stars. By studying these remnants, astronomers can better understand the nature of the progenitor stars, which are responsible for the creation and dispersal of most of the galaxy's heavy elements.
M83, located in the Southern Hemisphere, is often compared to M51, dubbed the Whirlpool galaxy, in the Northern Hemisphere. Located 15 million light-years away in the constellation Hydra, M83 is two times closer to Earth than M51.
Credit for Hubble image: NASA, ESA, R. O'Connell (University of Virginia), B. Whitmore (Space Telescope Science Institute), M. Dopita (Australian National University), and the Wide Field Camera 3 Science Oversight Committee
Credit for ground-based image: European Southern Observatory
Images and more information about M83 are available at:
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. Goddard manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, and is an International Year of Astronomy 2009 program partner. | 0.846301 | 3.976223 |
You've seen the movie. A weary radio astronomer is sitting in a control room full of complex electronics, with an earphone held sleepily against her ear. She hears a crackle, then another and another, until the unmistakable sound of a radio transmission is heard. Jolted alert, she checks known frequencies and finds that nothing should be there.
And yet it is. She grabs the red telephone and calls the President, telling him that the first radio transmission from an extraterrestrial intelligence has been received. Usually the plot unfolds with invasions and explosions.
So, that sort of just happened.
But that "sort of" is important, because it's rare that real science neatly follows a script that can be packed into a two-hour movie. Let me tell you the real story.
Astronomers working at a Canadian radio telescope have reported the observation of fast radio bursts or FRBs. Even more exciting, one FRB has been reported to repeat six times at the same location. This is uncommon and is why those who believe in the existence of extraterrestrial civilizations are so excited.
But it would be hasty to jump from this scientific triumph to the conclusion that ET is trying to contact us.
Here's what we do know.
FRBs are very short and extremely high-power bursts of radio energy that we detect in our telescopes here on Earth. They typically last only a few milliseconds and are usually broadband (which means they cover a range of frequencies). The burst is generally a single spike of energy, which is stable and constant over its brief duration.
FRBs are also a relatively recently-discovered phenomenon, first observed in 2007. They are observed everywhere in the sky and are not concentrated in the plane of our Milky Way galaxy. Combined with some technical observations of the precise time of arrival of different frequencies, this uniformity heavily points to an extragalactic origin. Whatever is causing FRBs, it is unlikely that they are emitted from within our galaxy.
The most recent announcement has been made by the CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope, located in the hills of British Columbia. Prior to the announcement, 50-60 FRBs had been observed and only one that had repeated itself. CHIME added 13 additional FRBs and a second repeater.
The low number of observed FRBs is probably due to limitations of the instrumentation. Earlier FRBs were observed at somewhat higher frequencies, while the CHIME telescope was able to look at frequencies in the range of 400 MHz. The next lowest one was at 700 MHz.
It's also worth noting that the CHIME observatory is in the commissioning phases and is not operating at full sensitivity. When the facility is performing according to expectations, it is likely that it could observe many dozens of FRBs per day.
In spite of some of the more breathless media reports that you will encounter, astronomers do not believe that FRBs are attempts by aliens to contact us. First, they appear spread across the entire sky -- with individual sources sometimes located billions of lightyears away from one another.
Second, it's just far more likely that FRBs have a natural origin. Because of the short (few millisecond) duration, it seems likely that the source is no larger than a few hundred kilometers in size. If the sources are of extragalactic origin and hundreds of millions of light hears away, they must be incredibly energetic, perhaps releasing in a few milliseconds the same amount of energy our sun releases in 10 to 100 years.
So, what are they? Frankly, we don't know. Some astronomers have proposed that they are due to the merging of neutron stars. Others have proposed that they are the result of the flares emitted by magnetars, which are highly magnetic neutron stars. This idea is similar to familiar solar flares, but much more energetic. Others have suggested that perhaps FRBs are due to a black hole converting into a white hole and exploding. Even more exotic explanations involve the collision of cosmic strings -- proposed remnants of the Big Bang.
At this point, the scientific community doesn't have a firm answer, but this most recent measurement adds critical information to the conversation. Most proposed explanations for FRBs are things that happen just once (like the merging of two stars).
The existence of two FRB sources that seem to be repeaters suggests a different origin. Something that happens again and again is more like the magnetar hypothesis. But it's going to take more data (and more thinking) to figure out just what the source is.
Because CHIME is just getting started, our understanding of FRBs is in the preliminary stages. This is always the case when new scientific facilities begin operations. Data and knowledge start with a trickle, with the flow increasing until scientists are deluged with information. It's likely that in a few years we will have a new appreciation of an interesting astronomical phenomenon.
And for those who really like the idea that FRBs are of extraterrestrial origin, it's probably worth remembering the cautionary tale of Jocelyn Bell Burnell, who discovered a different source of extraterrestrial radio waves back in 1967. She also heard a radio source in her instrumentation, and people didn't know what to make of it. Because of the uncertainty, her radio sources were briefly called LGM, short for "little green men." But, in the fullness of time, she had discovered pulsars, which are quickly rotating neutron stars.
Speculation is fun, but real science is far more informative. Let's give the astronomers a bit more time to discover how our universe works. | 0.879757 | 3.777458 |
eso1031 — Képrovat
Brilliant Star in a Colourful Neighbourhood
2010. július 28.
A spectacular new image from ESO’s Wide Field Imager at the La Silla Observatory in Chile shows the brilliant and unusual star WR 22 and its colourful surroundings. WR 22 is a very hot and bright star that is shedding its atmosphere into space at a rate many millions of times faster than the Sun. It lies in the outer part of the dramatic Carina Nebula from which it formed.
Very massive stars live fast and die young. Some of these stellar beacons have such intense radiation passing through their thick atmospheres late in their lives that they shed material into space many millions of times more quickly than relatively sedate stars such as the Sun. These rare, very hot and massive objects are known as Wolf–Rayet stars , after the two French astronomers who first identified them in the mid-nineteenth century, and one of the most massive ones yet measured is known as WR 22. It appears at the centre of this picture, which was created from images taken through red, green and blue filters with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. WR 22 is a member of a double star system and has been measured to have a mass at least 70 times that of the Sun.
WR 22 lies in the southern constellation of Carina, the keel of Jason’s ship Argo in Greek mythology. Although the star lies over 5000 light-years from the Earth it is so bright that it can just be faintly seen with the unaided eye under good conditions. WR 22 is one of many exceptionally brilliant stars associated with the beautiful Carina Nebula (also known as NGC 3372) and the outer part of this huge region of star formation in the southern Milky Way forms the colourful backdrop to this image.
The subtle colours of the rich background tapestry are a result of the interactions between the intense ultraviolet radiation coming from hot massive stars, including WR 22, and the vast gas clouds, mostly hydrogen, from which they formed. The central part of this enormous complex of gas and dust lies off the left side of this picture as can be seen in image eso1031b. This area includes the remarkable star Eta Carinae and was featured in an earlier press release (eso0905).
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Telefon: +49 89 3200 6759
ESO, Survey Telescopes PIO
Garching Telefon: +49 89 3200 6655 | 0.825253 | 3.669676 |
By John Palka — Posted May 29, 2016
A tree’s form is one of the characteristics that a skilled naturalist uses to identify it, to answer the basic question What is it? Together with the bark, the leaves or needles, and the flowers or cones, the form proclaims I am a Douglas fir, or I am an alder, or I am a grandmother cedar. But notice something that, once you think of it, is rather startling. Like these ghostly Sitka spruce in the silver forest bordering Rialto Beach on the Olympic Peninsula, most trees grow pretty much straight up.
You can specify the differences among various tree species, but if you focus on properties that they share, rather than on properties that distinguish them, you quickly realize that vertical growth characterizes the vast majority of trees, and indeed the vast majority of all plants. Upward growth is so common that we usually take it for granted and don’t think of asking any questions about it.
Biologists, however, have been intrigued by this ubiquitous characteristic of plants at least since the 1700s. They have repeatedly asked, how is it that the shoot of a plant typically grows upward, the root grows downward, and the branches grow sideways? In other words, how does a plant “know” which way is up and which way is down? And if it knows which direction is which, what mechanisms direct its growth in the appropriate direction?
I have taken an informal survey of my friends, asking them how it comes about that trees grow upward. The hesitant answer I have most often received is that trees grow upward because they grow toward the light. This is a reasonable hypothesis, because it is common experience that plants do grow toward the light. You can easily see that many garden bushes grow more abundantly toward the sunlight than they do toward the shade, and that many house plants grow better toward the window than away from it.
But here’s the rub. Unless you are in the tropics, the Sun is never directly overhead. Even at noon on the summer solstice, north of the Tropic of Cancer the Sun is southerly and south of the Tropic of Capricorn it is northerly. If sunlight were the dominant guiding factor in plant growth, all plants in our northern climes should lean toward the equator rather than growing straight up!
So, light manifestly does affect plant growth, but the path of the Sun across the sky does not account for the predominantly vertical growth patterns of plants that we actually observe all over the planet. What is another reasonable explanation?
Let us consider gravity.
In classical physics, gravity is a force that draws all objects to each other. According to Newton’s Law of Universal Gravitation, the greater the mass that objects have and the closer together they are, the greater is the force between them. Reciprocally, the less mass they have and the further apart they are, the lesser is the force. As Newton first recognized, and as we now know from not only from Newtonian classical but also from Einsteinian relativistic physics, gravity is what holds objects to the surface of the Earth, the Earth in its orbit around the Sun, and the solar system in its path around the center of our galaxy. Indeed, gravity underlies the physical structure of the entire Universe. What’s more, its effect is not limited to interactions between large objects. Our atmosphere—the very air we breathe—would drift away were it not for the pull of gravity between its tiny molecules and our relatively massive Earth.
So, is it possible that growing plants use gravity as their cue to which way is up? Let’s explore this idea with a simple experiment that we can perform right on the front porch. All we need is a plant that is actively growing, and a simple way of changing its orientation in the field of gravity. In my own version of the experiment, I went to the nearest nursery, bought three 4-inch pots of herbs, and set them on the porch railing to grow. I used photographs to record what they looked like before, during, and after reorientation with respect to gravity. To reorient, I simply laid each pot on its side. This meant that instead of being oriented up/down relative to the Earth’s gravitational field, the growing stems were oriented sideways.
Here’s the outcome of the experiment, illustrated by the growth pattern of a marjoram plant. As you can see in the picture below, taken at noon on day 1, its stems were vertical. There was a slight curvature, but nothing that would confuse the experiment.
As soon as I took this picture, I placed the pot on its side. Just twenty-four hours later the plant looked like this.
The stems had already redirected their growth and once again were growing nearly vertically in the field of gravity. The response was more dramatic than I had expected, and was even clear within four hours!
Being curious about whether this was a repeatable behavior, I waited another day and then turned all the plants back into their original orientation. Twenty-four hours after being turned upright, this is what the marjoram looked like.
Its stems had reverted to growth in the usual upward direction, but retained a visible “memory” of their experience of being placed sideways.
In this demonstration the distribution of light was not controlled, so I took one additional simple step. Once again, I laid the plants on their sides, but this time I placed them in a tightly closed cardboard box in our basement. Thus, they were in uniform darkness where light could provide no cues. A few hours later the outcome was the same as it had been in daylight—bending and upward-directed growth.
The shape of the plant once again revealed its history: The first upward bend in each stem had developed while the plant was growing on its side in daylight, while the second, just as vigorous, developed as the plant later grew in the dark. Once these manipulations had been completed I transferred the marjoram plant to a large pot in our front garden, where it is now happily growing upward with no further disturbance!
So, everything we have seen thus far is consistent with our initial hypothesis that the upward growth of a plant stem is guided by gravity. Reorientation in the field of gravity causes the plant to redirect its growth so it once again grows upward, away from the center of the Earth, even when there is no light to direct it. Light certainly affects the growth pattern of many plants, but gravity is the main factor guiding them upwards.
A plant’s form reflects its growth over time not only under experimental conditions, but also in nature. Look at these western hemlocks (Tsuga heterophylla) growing in a wonderful preserve on Whidbey Island close to Seattle called the Saratoga Woods.
Most of the trees are growing vertically. The one in front, however, was evidently bent over at some point in its history. It then grew in such a way that over a period of years it, too, produced a vertical trunk, just like its neighbors.
Having established that the growth pattern of plants is, indeed, responsive to the pull of gravity, it is natural to ask how this happens—how plants recognize the direction of gravity’s pull, and how they translate this information into the direction of growth. This will be the subject of another post. In the meantime, as you walk reflect on how gravity ties both trees and us inexorably to our Earth, and indeed to the entire Universe! | 0.856778 | 3.325794 |
Dark matter map of KiDS survey region (region G12)
This map of dark matter in the Universe was obtained from data from the KiDS survey, using the VLT Survey Telescope at ESO’s Paranal Observatory in Chile. It reveals an expansive web of dense (light) and empty (dark) regions. This image is one out of five patches of the sky observed by KiDS. Here the invisible dark matter is seen rendered in pink, covering an area of sky around 420 times the size of the full moon. This image reconstruction was made by analysing the light collected from over three million distant galaxies more than 6 billion light-years away. The observed galaxy images were warped by the gravitational pull of dark matter as the light travelled through the Universe.
Some small dark regions, with sharp boundaries, appear in this image. They are the locations of bright stars and other nearby objects that get in the way of the observations of more distant galaxies and are hence masked out in these maps as no weak-lensing signal can be measured in these areas.Autorska prava:
Kilo-Degree Survey Collaboration/H. Hildebrandt & B. Giblin/ESO
|Datum objavljivanja:||7. decembar 2016. 12:00|
|Veličina:||9152 x 3377 px|
|Tip:||Early Universe : Cosmology : Phenomenon : Dark Matter| | 0.842748 | 3.387546 |
Bakersfield Night Sky – April 18, 2015
By Nick Strobel
Well, the tax returns are now all done, so we can now relax under a starry sky and enjoy the sights. April is Global Astronomy Month and one of the ways to participate is Globe at Night. This program is an international citizen-science campaign to measure the night sky brightness from all over the globe and, in the process, raise public awareness of the impact of light pollution.
This month you can use the constellation Leo to determine how dark is our sky. Go outside more than a hour after sunset (so tonight, observe after 8:45 PM). Make sure the Moon is not up and give your eyes about ten minutes or so to get used to the dark. Match your observation of Leo with one of the star brightness (magnitude) charts on the Globe at Night website (www.globeatnight.org) and note the amount of cloud cover. The "Report" link on the website will automatically enter the date, time, and location of your observation if you allow it to use the location feature of your computer, tablet or phone.
An easy way to locate Leo is to use the Big Dipper part of Ursa Major. The Big Dipper is always somewhere in the northern sky and the asterism is bright enough to see even from most of Bakersfield. The star chart below shows the Big Dipper and Leo. The two end stars in the bowl part of the Big Dipper will point to the North Star, Polaris. Going in the opposite direction, those pointer stars will point you to the middle of Leo.
Look for a backward question mark on the sky. (It was known as "the Sickle" in past decades.) That is the head and chest part of the Lion. The bright star, Regulus, is at the bottom of the question mark, so perhaps it is the heart of the lion. The name means "the little king". Regulus is a blue-white star only 79 light years away. The star is near the end of its healthy adult stage of its life, fusing hydrogen to make helium in its core.
Regulus shines with a luminosity of about 360 times the Sun and it has a mass about 3.4 times the Sun. Because its mass is more than the Sun, it will have a shorter life than the Sun. The more massive stars are the gas-guzzling SUVs of the cosmos. Regulus is roughly 250 million years old, much shorter than the 4.6 billion year age of the Sun and much less than the 10 billion year lifetime of the Sun.
Regulus is actually a quadruple star. The easiest-to-see companion orbits the main star at about 100 times the distance that Pluto orbits the Sun with a period of at least 125,000 years. That companion is actually a double-star system! Those stars orbit each other from a distance of a little over twice Pluto's distance from the Sun. Both stars are smaller and dimmer than the Sun, one an orange-warm star and the other a cooler red star.
The fourth star of the system orbits very close to Regulus in a time of just 40 days. It appears to be a white dwarf, the dead remains of a star that used to be slightly more massive than the main star. We know it once was more massive than Regulus because more massive stars live shorter lives than lower mass stars and the former star very, very likely formed at the same time as Regulus. When the former star went through its dying red giant phase, it dumped gas onto Regulus which is why Regulus is spinning so fast today and is also why the white dwarf has such an unusually low mass, just 30% of the Sun.
In the middle of the question mark (Sickle) part of Leo is Algieba, a double giant with at least one planet orbiting the brighter giant. The giants are 131 light years away and orbit each other at an average distance of more than four times the distance between Pluto and the Sun. The two stars are in the dying stages of their lives having bloated outward to diameters of 29 and 12 times the diameter of the Sun. They have masses of 3.0 and 2.5 times the mass of the Sun.
To the left of the question mark (Sickle) part of Leo is a triangle of brighter stars. The top right star of the triangle is Zosma which means "girdle" and it is at the hip of the lion. Zosma is only 58 light years away and has a luminosity of 23 times the Sun. It has 2.2 times the mass of the Sun and it is over halfway through its billion-year long lifespan.
The far left star of Leo is Denebola, which appropriately means "tail of the lion". Denebola is a white-hot star just 36 light years away. It is in its healthy adult stage fusing hydrogen in its core. Denebola has a luminosity of 14 times the Sun and is surrounded by a dusty disk that could be forming planets.
Another easy way to find Leo that will work for the next several months is to look for Jupiter high up in the southern sky at 9 PM. Jupiter shines brighter than any star in the night sky, so you'll have no trouble finding it. Leo will be to the left of Jupiter. To the right of Jupiter, see if you can spot the Beehive Cluster at the heart of the dim zodiac constellation, Cancer. Jupiter had almost reached the Beehive Cluster when Jupiter was doing its retrograde motion earlier this year but now Jupiter is moving toward Leo, reaching Regulus in August. "Reaching Regulus" is not literal, of course, since Jupiter is about 1.25 million times closer to us than Regulus.
The next couple of nights will be good nights for the Globe at Night observations (depending on the weather) because the Moon is at New Phase today. Tomorrow the very thin Waxing Crescent will already have set by the time the sky is dark enough for the observations. The First Quarter Moon will pass beneath the Beehive Cluster on April 25th.
Further west you'll spot the only planet that outshines Jupiter, our nearest neighbor, Venus. Venus is now at the head of Taurus and by the end of the month you'll see it at the tip of the horns.
Another thing to do in this coming week of Astronomy month is to enter your ideas for names of features on Pluto and its moon Charon. Go to www.ourpluto.org to submit your suggestions and to vote for your favorites. The ballot will close on Friday, the 24th. On July 14th, the New Horizons spacecraft will fly past Pluto and Charon, snapping pictures and madly taking hundreds of measurements as it flies past at 31,300 mph.
Right now, Pluto is just a fuzzy blob in New Horizon's cameras but the New Horizons team wants to have a ready list of names to give the craters, cracks, cliffs, plains, etc. that will be visible by the end of June. New Horizons will be the first spacecraft to get to Pluto. NASA launched New Horizons on its fastest rocket nine years ago. It reached the orbit of the Moon in just nine hours. If there had been a delay in its launch, it would not have been able to swing by Jupiter to get a gravity boost that shaved six years off its journey.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com | 0.879753 | 3.274436 |
Jan 10, 2012
El Gordo is so called because it is the biggest, brightest, and hottest pair of colliding galaxy clusters known to astronomers.
Astronomers “know” that El Gordo is over 7 billion light-years from Earth. This knowledge derives from the amount by which El Gordo’s light is shifted toward the red end of the visual spectrum, called redshift. That redshift is an indicator of distance is an indisputable fact. It is indisputable because, ever since Halton Arp was driven from the field in 1983 for disputing it, anyone who tries to dispute it is denied telescope time, refused publication, and blacklisted from employment.
Of course, if redshift were intrinsic, as Arp proposed, El Gordo would likely be nearby, small, faint, and cool.
Seeing (the sensation) is absolute and ambiguous: You can be sure that you see patches of blue in the image, but you can’t be sure what they mean. Seeing (understanding) depends on assumptions about fundamentals, which are necessarily preconceptions. Nevertheless, conclusions don’t have to be preconceptions: If astronomy were a rational science instead of a preconceptual science, alternative hypotheses would be investigated and compared.
Astronomers with preconceptions about gravity (that it’s the primary force that gives structure in the universe) will see in this image “normal matter, mainly composed of hot, X-ray bright gas, [that] has been wrenched apart from the dark matter….”
Electric Universe advocates with preconceptions about plasma (that the empirically discovered electrical properties of plasma overwhelm gravity in most situations in space) will see the two tails as the braided filaments of Birkeland currents: The cluster may be the pinch point at closest approach of two intergalactic Birkeland currents. Or it could be the beginning stage of a galaxy forming according to Anthony Peratt’s computer simulation, and the “hot” galaxy at the center is the sump. Or it could be a “comet” galaxy, composed of fragments of a few stars, in the sheath of some nearby galaxy.
A baker will see the Pillsbury Doughboy falling on his head.
I recommend not taking our theories too seriously. | 0.849948 | 3.545887 |
NASA has selected two robotic missions to visit asteroids in the early 2020s from a field of proposed interplanetary probes, approving projects to explore a metallic relic from the early solar system and a half-dozen so-called Trojan objects left over from the formation of the outer planets.
The Lucy and Psyche spacecraft will join NASA’s line of cost-capped Discovery missions, a program under which the agency’s Mars Pathfinder rover, the Messenger mission to orbit Mercury, and the Dawn probe currently orbiting the dwarf planet Ceres were developed, built and launched.
Picked from a slate of 28 proposals submitted to NASA in 2015, Lucy and Psyche will visit worlds never before seen close-up as scientists seek to sort out the violent early history of the solar system, in which proto-planets coalesced from mergers and collisions between rocks and boulders in a disk around the sun.
Lucy will launch in October 2021 on a preliminary trajectory to escape the bonds of Earth’s gravity, then return for flybys to use the planet’s gravity to slingshot toward the mission’s targets in the asteroid belt and beyond.
The probe’s first destination in April 2025 will be the asteroid DonaldJohanson, named for the paleoanthropologist who discovered the fossil of Lucy, a human ancestor whose partial skeleton was discovered in Ethiopia in 1974. The Lucy spacecraft will then head as far as 500 million miles (800 million kilometres) from the sun on a series of high-speed passes through groups of Trojan asteroids, primitive worlds trapped by Jupiter’s gravity in swarms ahead of and behind the giant planet’s path.
Lucy will fly by at least six Trojan asteroids at close range from August 2027 through March 2033, the first time a spacecraft has visited a member of the Trojan population, which some scientists estimate may number in the hundreds of thousands of objects.
“Lucy is a flyby mission,” said Harold Levison, the mission’s principal investigator from the Southwest Research Institute in Boulder, Colorado. “Lucy fits in with NASA’s history of exploration — first you do flybys, then you do rendezvous and then you do landings. In our case, in order to cover the diversity that we need to cover, we need to move quickly through the Trojan swarms to cover a lot of real estate, and that means that we’re doing flybys only.”
The Jupiter Trojans may hold clues about the evolution of the solar system, especially the outer planets and the formation of Jupiter and its moons, scientists said. The frozen mini-worlds could be time capsules, keeping the characteristics they had more than 4 billion years ago, before scientists believe the immense pull of Jupiter’s gravity trapped them in their current locations.
Because of their distance from Earth, fragments from the Jupiter Trojans have never fallen to the ground as meteorites, robbing scientists of any insight into their history and make-up.
“These objects are totally unknown,” Levison said. “Not only are they unknown because we’ve never really visited them with a spacecraft, unlike almost every other small body population in the solar system, these objects do not contribute to the meteorite record on Earth. Comets, main belt asteroids, near-Earth asteroids, all are contributing, but not Trojans because of their proximity to Jupiter’s orbit.”
The Psyche mission, named for its destination, will depart Earth in October 2023. Its trajectory will take the spacecraft on gravity assist flybys around Earth and Mars in 2024 and 2025, then to the asteroid Psyche in 2030, where the probe will enter orbit for at least 12 months of detailed measurements and observations.
“Psyche is a small world that’s made entirely of iron-nickel metal,” said Linda Elkins-Tanton, the Psyche mission’s principal investigator from Arizona State University. “Humankind has visited rocky worlds, and icy worlds, and worlds made of gas, but we have never seen a metal world. Psyche has never been visited or had a picture taken that was more than a point of light, so it’s apperance remains a mystery. This mission will be true exploration and discovery.”
Asteroid Psyche resides in the outer part of the main asteroid belt between the orbits of Mars and Jupiter, with an average distance of around 270 million miles (430 million kilometres) from the sun, three times farther than the Earth. Telescopic observations indicate Psyche is about 186 miles (300 kilometres) in diameter, but its topography and shape remain a mystery.
Astronomical observations show that Psyche’s metallic composition is much like Earth’s super-dense, super-heated inner core, an environmental unreachable by humans or modern research tools.
“We think that Psyche is the metal core of a small planet that was destroyed in the high-energy, high-speed first one-one hundredth of the age of our solar system,” Elkins-Tanton said. “By visiting Psyche, we can literally visit a planetary core the only way that humankind ever can.”
The Lucy and Psyche missions come with strict cost constraints imposed by NASA.
The space agency’s cost cap for the missions is $450 million each, a figure that does not include launch costs.
Levison said the Lucy spacecraft will be built by Lockheed Martin in Denver and will be based on the company’s design of previous interplanetary probes, most recently the OSIRIS-REx asteroid sample return mission launched in September 2016.
Space Systems/Loral of Palo Alto, California, will manufacture the Psyche spacecraft with a suite of ion thrusters to steer the probe toward its destination. Based on the company’s 1300-series design for commercial communications satellites, Psyche is the first spacecraft SSL will build for a NASA Discovery-class interplanetary mission.
Lucy will fly with conventional chemical rocket thrusters, relying primarily on gravity assists to bend its trajectory toward the Trojan swarms, Levison said.
To be managed by NASA’s Goddard Space Flight Center and Jet Propulsion Laboratory, respectively, Lucy and Psyche came out on top in NASA’s evaluation of five finalists culled from a list of 28 initial proposals submitted to the agency in early 2015.
The winning missions beat out two robotic probes that would have flown to Venus — an orbiter with a radar mapping instrument and a craft that would have studied Venus’s atmosphere during an hour-long parachute-assisted descent.
A fifth finalist was called NEOCam, an observatory planned to search for asteroids that could threaten Earth. While NASA did not approve NEOCam for full development, officials plan to continue funding the mission’s team at JPL for at least another year, aiming to reduce risk and keep the project alive for a possible future selection.
NASA picks Discovery missions in competitions among scientists with interests in the planets, asteroids, comets. Researchers are charged with assembling broad scientific and industrial teams that include developers of science instruments, spacecraft builders and project management experts.
“In that competition, we’re looking for top science, top scientific implementation, and minimizing our technical risk,” said Jim Green, director of NASA’s planetary science division. “Each of the principal investigators have a cost cap they must be able to stay under. All these factors are folded into a comprehensive evaluation.
“It would be wonderful if we could have selected more than two, but of course, obviously we’re delighted with the two selections, and our ability to move forward with two,” Green said during the Jan. 4 announcement of Lucy and Psyche. “Our budget in the past hasn’t enabled us to always do that.”
Green on Jan. 11 told NASA’s Small Bodies Assessment Group, a committee of scientists specializing in research on asteroids, comets and dwarf planets, that the launch dates for Lucy and Psyche are staggered to fit within the agency’s planetary science budget and based on orbital mechanics.
“These are the two that were the most technically ready, with top science,” Green said.
“One of the charges we gave them was to look for optimal launch windows,” he said. “That gives us the greatest flexibility to make a selection of two, where we have staggered launch windows.”
Lucy will get a head start on its development, with its launch date set for October 2021. Psyche will follow a couple of years later.
NASA has typically picked just one Discovery mission during each competition.
The last Discovery competition resulted in the approval of the InSight Mars lander in August 2012, with a target launch date in March 2016. InSight’s seismic research mission to the Martian surface has been delayed due to technical issues, with launch now scheduled in May 2018.
NASA is trying to reduce the time between Discovery-class missions, after the National Research Council recommended the agency mount competitions every two years, close to the cadence achieved earlier in the Discovery program in the late 1990s and early 2000s.
But NASA’s planetary science funding waned over the last decade, and the agency’s relatively low-cost Discovery program suffered. More costly flagship-level science missions like the Curiosity rover also took up a large slice of NASA’s remaining planetary science budget.
Green said NASA’s current budget allows for a new Discovery competition within three years, down from the four-and-a-half years between the selections of InSight and Lucy and Psyche.
“The administration and Congress have approved a healthy program that can’t quite get us to 24 months, but gets it now closer to 32-36 months,” Green said Jan. 11.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1. | 0.892921 | 3.660483 |
HUBBLE DETECTS GAS STREAMER ECLIPSES SUPERMASSIVE BLACK HOLE
From the FMS Global News Desk of Jeanne Hambleton
Embargo expired: 19-Jun-2014 2:00 PM EDT
Source Newsroom: Space Telescope Science Institute (STScI)
Citations Science Express, Jun-2014
Newswise — An international team of astronomers, using data from several NASA and European Space Agency (ESA) space observatories, has discovered unexpected behavior from the supermassive black hole at the heart of the galaxy NGC 5548, located 244.6 million light-years from Earth. This behavior may provide new insights into how supermassive black holes interact with their host galaxies.
Immediately after NASA’s Hubble Space Telescope observed NGC 5548 in June 2013, this international research team discovered unexpected features in the data. They detected a stream of gas flowing rapidly outward from the galaxy’s supermassive black hole, blocking 90 percent of its emitted X-rays.
“The data represented dramatic changes since the last observation with Hubble in 2011,” said Gerard Kriss of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “I saw signatures of much colder gas than was present before, indicating that the wind had cooled down due to a significant decrease in X-ray radiation from the galaxy’s nucleus.”
The discovery was made during an intensive observing campaign that also included data from NASA’s Swift spacecraft, Nuclear Spectroscopic Telescope Array (NuSTAR), and Chandra X-ray Observatory, as well as ESA’s X-ray Multi-Mirror Mission (XMM-Newton) and Integral gamma-ray observatory (INTEGRAL).
After combining and analyzing data from all six sources, the team was able to put together the pieces of the puzzle. Supermassive black holes in the nuclei of active galaxies, such as NGC 5548, expel large amounts of matter through powerful winds of ionized gas. For instance, the persistent wind of NGC 5548 reaches velocities exceeding 621 miles (approximately 1,000 kilometers) a second. But now a new wind has arisen, much stronger and faster than the persistent wind.
“These new winds reach speeds of up to 3,107 miles (5,000 kilometers) per second, but is much closer to the nucleus than the persistent wind,” said lead scientist Jelle Kaastra of the SRON Netherlands Institute for Space Research.
“The new gas outflow blocks 90 percent of the low-energy X-rays that come from very close to the black hole, and it obscures up to a third of the region that emits the ultraviolet radiation at a few light-days distance from the black hole.”
The newly discovered gas stream in NGC 5548 — one of the best-studied of the type of galaxy know as Type I Seyfert — provides the first direct evidence of a shielding process that accelerates the powerful gas streams, or winds, to high speeds. These winds only occur if their starting point is shielded from X-rays.
It appears the shielding in NGC 5548 has been going on for at least three years, but just recently began crossing their line of sight.
“There are other galaxies with similar streams of gas flowing outward from the direction of its central black hole, but we’ve never before found evidence that the stream of gas changed its position as dramatically as this one has,” said Kriss. “This is the first time we’ve seen a stream like this move into our line of sight. We got lucky.”
Researchers also deduced that in more luminous quasars, the winds may be strong enough to blow off gas that otherwise would have become “food” for the black hole, thereby regulating both the growth of the black hole and that of its host galaxy.
These results are being published online in the Thursday issue of Science Express.
For images and more information about Hubble, visit:
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. STScI conducts Hubble science operations and is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
NEW BRAIN PATHWAYS FOR TYPE 2 DIABETES AND OBESITY
UT SOUTHWESTERN RESEARCHERS UNCOVER NEURAL PATHWAYS
From the FMS Global News Desk of Jeanne Hambleton
Released: 25-Jul-2014 2:00 PM EDT
Source Newsroom: UT Southwestern Medical Center
Citations Nature Neuroscience 17, 911–913 (2014)
Newswise — DALLAS – July 25, 2014 – Researchers at UT Southwestern Medical Center have identified neural pathways that increase understanding of how the brain regulates body weight, energy expenditure, and blood glucose levels – a discovery that can lead to new therapies for treating Type 2 diabetes and obesity.
The study, published in Nature Neuroscience, found that melanocortin 4 receptors (MC4Rs) expressed by neurons that control the autonomic nervous system are key in regulating glucose metabolism and energy expenditure, said senior author Dr. Joel Elmquist, Director of the Division of Hypothalamic Research, and Professor of Internal Medicine, Pharmacology, and Psychiatry.
“A number of previous studies have demonstrated that MC4Rs are key regulators of energy expenditure and glucose homeostasis, but the key neurons required to regulate these responses were unclear,” said Dr. Elmquist, who holds the Carl H. Westcott Distinguished Chair in Medical Research, and the Maclin Family Distinguished Professorship in Medical Science, in Honor of Dr. Roy A. Brinkley.
“In the current study, we found that expression of these receptors by neurons that control the sympathetic nervous system, seem to be key regulators of metabolism. In particular, these cells regulate blood glucose levels and the ability of white fat to become ‘brown or beige’ fat.”
Using mouse models, the team of researchers, including co-first authors Dr. Eric Berglund, Assistant Professor in the Advanced Imaging Research Center and Pharmacology, and Dr. Tiemin Liu, a postdoctoral research fellow in Internal Medicine, deleted MC4Rs in neurons controlling the sympathetic nervous system.
This manipulation lowered energy expenditure and subsequently caused obesity and diabetes in the mice. The finding demonstrates that MC4Rs are required to regulate glucose metabolism, energy expenditure, and body weight, including thermogenic responses to diet and exposure to cold. Understanding this pathway in greater detail may be a key to identifying the exact processes in which type 2 diabetes and obesity are developed independently of each other.
In 2006, Dr. Elmquist collaborated with Dr. Brad Lowell and his team at Harvard Medical School to discover that MC4Rs in other brain regions control food intake but not energy expenditure.
The American Diabetes Association lists Type 2 diabetes as the most common form of diabetes. The disease is characterized by high blood glucose levels caused by the body’s lack of insulin or inability to use insulin efficiently, and obesity is one of the most common causes.
Future studies by Dr. Elmquist’s team will examine how melanocortin receptors may lead to the “beiging” of white adipose tissue, a process that converts white adipose to energy-burning brown adipose tissue.
Other UT Southwestern researchers involved in the study include Dr. Philipp Scherer, Director of the Touchstone Center for Diabetes Research, Professor of Internal Medicine and Cell Biology, and holder of the Gifford O. Touchstone, Jr. and Randolph G. Touchstone Distinguished Chair in Diabetes Research; Dr. Kevin Williams, Assistant Professor of Internal Medicine; Dr. Syann Lee, Instructor of Internal Medicine; Dr. Jong-Woo Sohn, postdoctoral research fellow; and Charlotte Lee, senior research scientist.
The study was supported by the National Institutes of Health, the American Diabetes Association, and the American Heart Association.
About UT Southwestern Medical Center
UT Southwestern, one of the premier academic medical centers in the nation, integrates pioneering biomedical research with exceptional clinical care and education. The institution’s faculty includes many distinguished members, including six who have been awarded Nobel Prizes since 1985. Numbering more than 2,700, the faculty is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide medical care in 40 specialties to nearly 91,000 hospitalized patients and oversee more than 2 million outpatient visits a year.
NEW CLUE HELPS EXPLAIN HOW BROWN FAT BURNS ENERGY
Investigators identify a major transciption fact that drives brown fat’s thermogenic process
From the FMS Global News Desk of Jeanne Hambleton
Embargo expired: 3-Jul-2014 12:00 PM EDT
Source Newsroom: Beth Israel Deaconess Medical Center
Newswise — BOSTON – The body contains two types of fat cells, easily distinguished by color: White and brown. While white fat serves to store excess calories until they are needed by the body, brown adipocytes actually burn fat by turning it into heat.
Ever since it was discovered that adult humans harbor appreciable amounts of brown fat, investigators have been working to better understand its thermogenic fat-burning properties with the ultimate goal of developing novel therapies to combat obesity and diabetes.
Now, research led by investigators at Beth Israel Deaconess Medical Center (BIDMC) adds another piece to the puzzle, demonstrating that the transcription factor IRF4 (interferon regulatory factor 4) plays a key role in brown fat’s thermogenic process, regulating energy expenditure and cold tolerance. The findings appear in the July 3 issue of the journal Cell.
“The discovery several years ago that brown fat plays an active role in metabolism suggested that if we could manipulate the number or activity of these fat cells, we could force our bodies to burn extra calories,” explains the study’s senior author Evan Rosen, MD, PhD, an investigator in the Division of Endocrinology, Diabetes and Metabolism at BIDMC and Associate Professor of Medicine at Harvard Medical School.
“Now that we have identified a major factor driving this process, we can look for new approaches to exploit this for therapeutic benefit.”
Turned on by cold temperatures and by certain hormones and drugs, including epinephrine, brown fat generates heat through the actions of a group of genes collectively termed the thermogenic gene expression program, the best known of which encodes uncoupling protein 1 (UCP1). UCP1 dissipates, or wastes, energy in the mitochondria of brown fat cells, causing heat generation as a byproduct.
“There has been intense interest in how the UCP1 gene is regulated, with most attention focused on a molecule called PGC1-alpha,” explains Rosen.”PGC1-alpha was discovered 15 years ago in the lab of coauthor Bruce Spiegelman, and is a transcriptional co-factor, which means that it indirectly drives the transcription of genes like UCP1 because it lacks the ability to bind to DNA itself. This suggested that there must be a bona fide transcription factor, or DNA binding protein, that was mediating the effects of PGC-1alpha, but despite years of work and several promising candidates, no clear partner for PGC-1alpha had been discovered to increase thermogenesis. It turns out that IRF4 is that partner.”
Interferon regulatory factors (IRFs) play important roles in the regulation of the immune system. Rosen’s group had previously identified IRF4 as a key element in adipocyte development and lipid handling, having discovered that IRF4 expression is induced by fasting in fat and that animals that lack IRF4 in adipose tissue are obese, insulin resistant and cold intolerant.
In this new work, led by first author Xingxing Kong, PhD, a postdoctoral fellow in the Rosen lab, the scientists hypothesized that in addition to serving as a key regulator of lipolysis, IRF4 might also play a direct thermogenic role in brown fat.
Experiments in mouse models confirmed their hypothesis, demonstrating that IRF4 is induced by cold and cAMP in adipocytes and is sufficient to promote increased thermogenic gene expression, energy expenditure and cold tolerance. Conversely, loss of IRF4 in brown fat resulted in reduced thermogenic gene expression and energy expenditure, obesity and cold intolerance. Finally, the researchers showed that IRF4 physically interacts with PGC-1 alpha to promote UCP1 expression and thermogenesis.
“We’ve known a lot about how these genes are turned on by cold or when stimulated by catelcholamine drugs such as epinephrine,” explains Rosen.
“But we did not know what was turning on this gene program at the molecular level. With this new discovery of IRF4’s key transcriptional role, perhaps we can identify new drug targets that directly affect this pathway, which might be more specific than simply giving epinephrine-like drugs, which drive up heart rate and blood pressure.”
In addition to Rosen and Kong, coauthors include BIDMC investigators Tiemin Liu (now at the University of Texas Southwestern Medical Center), Songtao Yu (now at Northwestern University Feinberg School of Medicine), Xun Wang and Sona Kang; Alexander Banks, Lawrence Kazak, Rajesh R. Rao, Paul Cohen, James C. Lo, Sandra Kleiner and Bruce M. Spiegelman of Dana-Farber Cancer Institute; and Yu-Hua Tseng, Aaron M. Cypess and Ruidan Xue of Joslin Diabetes Center.
This study was funded, in part by National Institutes of Health grants R01 DK31405 and R01 DK085171 and an American Heart Association postdoctoral fellowship to Xingxing Kong.
Beth Israel Deaconess Medical Center is a patient care, teaching and research affiliate of Harvard Medical School, and currently ranks third in National Institutes of Health funding among independent hospitals nationwide.
The BIDMC health care team includes Beth Israel Deaconess Hospital-Milton, Beth Israel Deaconess Hospital-Needham, Beth Israel Deaconess Hospital-Plymouth, Anna Jaques Hospital, Cambridge Health Alliance, Lawrence General Hospital, Signature Health Care, Commonwealth Hematology-Oncology, Beth Israel Deaconess HealthCare, Community Care Alliance, and Atrius Health. BIDMC is also clinically affiliated with the Joslin Diabetes Center and Hebrew Senior Life and is a research partner of Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the Boston Red Sox. For more information, visit http://www.bidmc.org.
Back tomorrow with more news. Jeanne | 0.846353 | 3.680682 |
Fancy a cup of cosmic tea? This one isn't as calming as the ones on Earth. In a galaxy hosting a structure nicknamed the "Teacup," a galactic storm is raging.
The source of the cosmic squall is a supermassive black hole buried at the center of the galaxy, officially known as SDSS 1430+1339. As matter in the central regions of the galaxy is pulled toward the black hole, it is energized by the strong gravity and magnetic fields near the black hole. The infalling material produces more radiation than all the stars in the host galaxy. This kind of actively growing black hole is known as a quasar.
Located about 1.1 billion light years from Earth, the Teacup's host galaxy was originally discovered in visible light images by citizen scientists in 2007 as part of the Galaxy Zoo project, using data from the Sloan Digital Sky Survey. Since then, professional astronomers using space-based telescopes have gathered clues about the history of this galaxy with an eye toward forecasting how stormy it will be in the future. This new composite image contains X-ray data from Chandra (blue) along with an optical view from NASA's Hubble Space Telescope (red and green).
The "handle" of the Teacup is a ring of optical and X-ray light surrounding a giant bubble. This handle-shaped feature, which is located about 30,000 light-years from the supermassive black hole, was likely formed by one or more eruptions powered by the black hole. Radio emission — shown in a separate composite image with the optical data — also outlines this bubble, and a bubble about the same size on the other side of the black hole.
Previously, optical telescope observations showed that atoms in the handle of the Teacup were ionized, that is, these particles became charged when some of their electrons were stripped off, presumably by the quasar's strong radiation in the past. The amount of radiation required to ionize the atoms was compared with that inferred from optical observations of the quasar. This comparison suggested that the quasar's radiation production had diminished by a factor of somewhere between 50 and 600 over the last 40,000 to 100,000 years. This inferred sharp decline led researchers to conclude that the quasar in the Teacup was fading or dying.
New data from Chandra and ESA's XMM-Newton mission are giving astronomers an improved understanding of the history of this galactic storm. The X-ray spectra (that is, the amount of X-rays over a range of energies) show that the quasar is heavily obscured by gas. This implies that the quasar is producing much more ionizing radiation than indicated by the estimates based on the optical data alone, and that rumors of the quasar's death may have been exaggerated. Instead the quasar has dimmed by only a factor of 25 or less over the past 100,000 years.
The Chandra data also show evidence for hotter gas within the bubble, which may imply that a wind of material is blowing away from the black hole. Such a wind, which was driven by radiation from the quasar, may have created the bubbles found in the Teacup.
Astronomers have previously observed bubbles of various sizes in elliptical galaxies, galaxy groups and galaxy clusters that were generated by narrow jets containing particles traveling near the speed of light, that shoot away from the supermassive black holes. The energy of the jets dominates the power output of these black holes, rather than radiation.
In these jet-driven systems, astronomers have found that the power required to generate the bubbles is proportional to their X-ray brightness. Surprisingly, the radiation-driven Teacup quasar follows this pattern. This suggests radiation-dominated quasar systems and their jet-dominated cousins can have similar effects on their galactic surroundings.
A study describing these results was published in the March 20, 2018 issue of The Astrophysical Journal Letters and is available online. The authors are George Lansbury from the University of Cambridge in Cambridge, UK; Miranda E. Jarvis from the Max-Planck Institut für Astrophysik in Garching, Germany; Chris M. Harrison from the European Southern Observatory in Garching, Germany; David M. Alexander from Durham University in Durham, UK; Agnese Del Moro from the Max-Planck-Institut für Extraterrestrische Physik in Garching, Germany; Alastair Edge from Durham University in Durham, UK; James R. Mullaney from The University of Sheffield in Sheffield, UK and Alasdair Thomson from the University of Manchester, Manchester, UK.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. | 0.868151 | 4.092217 |
- Frontier letter
- Open Access
AKATSUKI returns to Venus
Earth, Planets and Space volume 68, Article number: 75 (2016)
AKATSUKI is the Japanese Venus Climate Orbiter that was designed to investigate the climate system of Venus. The orbiter was launched on May 21, 2010, and it reached Venus on December 7, 2010. Thrust was applied by the orbital maneuver engine in an attempt to put AKATSUKI into a westward equatorial orbit around Venus with a 30-h orbital period. However, this operation failed because of a malfunction in the propulsion system. After this failure, the spacecraft orbited the Sun for 5 years. On December 7, 2015, AKATSUKI once again approached Venus and the Venus orbit insertion was successful, whereby a westward equatorial orbit with apoapsis of ~440,000 km and orbital period of 14 days was initiated. Now that AKATSUKI’s long journey to Venus has ended, it will provide scientific data on the Venusian climate system for two or more years. For the purpose of both decreasing the apoapsis altitude and avoiding a long eclipse during the orbit, a trim maneuver was performed at the first periapsis. The apoapsis altitude is now ~360,000 km with a periapsis altitude of 1000–8000 km, and the period is 10 days and 12 h. In this paper, we describe the details of the Venus orbit insertion-revenge 1 (VOI-R1) and the new orbit, the expected scientific information to be obtained at this orbit, and the Venus images captured by the onboard 1-µm infrared camera, ultraviolet imager, and long-wave infrared camera 2 h after the successful initiation of the VOI-R1.
Venus is our nearest neighboring planet with a size very similar to that of the Earth. It has been explored by the USSR, the USA, and Europe since the 1970s. The USSR VENERA series probes (Moroz 1981) landed on the surface of Venus and revealed that the temperature at the surface is 740 K and the pressure is 92 bars, which is quite different from our terrestrial environment (Colin 1983). The atmosphere consists mainly of CO2. A striking finding is that the atmosphere rotates westward around the planet with a period of 4 d at an altitude of 50–60 km, while the planet itself rotates westward more slowly with a period of 243 days; this is called superrotation (Schubert 1983). The USA’s Pioneer Venus orbiter studied Venus over 12 years by remote sensing techniques (Lellouch et al. 1997; Taylor et al. 1997). Moreover, the Venusian atmosphere was studied during the Venus Express mission of the European Space Agency (Svedhem et al. 2007), which had an operational period ranging from 2006 to 2014. This mission was a modified version of the Mars Express mission (Chicarro et al. 2004) that was dedicated to investigations of the Martian atmosphere solely by the use of spectroscopic techniques. Venus Express also employed several spectroscopic instruments.
AKATSUKI was also designed to study the Venusian atmosphere, but in contrast to the Venus Express strategy, five cameras with narrowband filters will image Venus at different wavelengths to track the distributions of clouds and minor gaseous constituents at different heights (Fig. 1). In other words, we aim to study the Venusian atmospheric dynamics in three dimensions, while Venus Express collected mainly spectroscopic observations of the atmosphere. These two spacecraft are capable of revealing complementary aspects of the Venusian atmosphere. On Venus Express, the Venus monitoring camera (VMC) (Markiewicz et al. 2007) with four narrowband filters from ultraviolet (UV) to near infrared (IR) made similar observations, but as Venus Express was in a polar orbit, it could not track the cloud patterns appearing on Venus. AKATSUKI is on a westward equatorial orbit and is capable of taking successive images in the low- and midlatitudes of Venus, which is advantageous for studies of the atmosphere.
AKATSUKI has started collecting observations, and the first images of Venus taken by the onboard 1-µm infrared camera (IR1), ultraviolet imager (UVI), and long-wave infrared camera (LIR) are presented in “First images of Venus by the cameras” section. The scientific background for this research and data processing procedures are described in detail by Nakamura et al. (2011, 2014).
The development of the Japanese Venus Climate Orbiter AKATSUKI was first proposed to the Institute of Space and Astronautical Science (ISAS) in 2001, and this initiative was strongly supported by the international Venus science community as an interplanetary mission (Nakamura et al. 2007, 2011). The main goal of AKATSUKI is to shed light on the mechanism driving the fast atmospheric circulation of Venus. The systematic imaging sequencing capability of AKATSUKI is advantageous for detecting meteorological phenomena on various temporal and spatial scales. AKATSUKI has following five photometric sensors as mission instruments for imaging (Fig. 1): IR1, a 2-μm infrared camera (IR2), UVI, LIR, and a lightning and airglow camera (LAC). Except for the LIR, these photometers have changeable filters in the optics to allow for imaging at different wavelengths. AKATSUKI’s long, elliptical orbit around Venus is suitable for obtaining cloud-tracked wind vectors continuously in the low- and midlatitudes. With these instruments, we expect to be able to characterize the meridional circulation, midlatitude jets, and their various wave activities.
IR1 is designed to monitor the dayside of Venus at 0.90 μm and the nightside at 0.90, 0.97 and 1.01 μm, which are located in atmospheric windows (Iwagami et al. 2011). The measurements at 0.90 and 1.01 μm will yield information about the surface material (Baines et al. 2000; Hashimoto and Sugita 2003; Hashimoto et al. 2008). IR2 utilizes atmospheric windows at wavelengths of 1.73, 2.26 and 2.32 μm (Satoh et al. 2015). With these wavelengths, IR2 is most sensitive to thermal radiation originating from altitudes of 35–50 km. IR2 also employs two more wavelengths, namely one at 2.02 μm to detect variations of cloud top altitudes as intensity variations of reflected sunlight (Satoh et al. 2015) and an astronomical H-band centered at 1.65 μm. The UVI is designed to measure ultraviolet radiation scattered from the cloud top altitudes in two bands centered at 283 and 365 nm (Nakamura et al. 2011). The LIR detects thermal radiation emitted from the cloud tops over a rather wide wavelength region of 8–12 μm, and this enables mapping of the cloud top temperatures (Taguchi et al. 2007; Fukuhara et al. 2011). Unlike other imagers onboard AKATSUKI, LIR takes images of both the dayside and nightside equally. The corresponding cloud top temperature maps will reflect the cloud height distributions, whose detailed structures are unknown except for in the northern high latitudes at areas observed by Pioneer Venus (Taylor et al. 1980). The map data will also reflect the atmospheric temperature distribution. LAC is a high-speed imaging sensor that measures lightning flashes and airglow emissions on the nightside of Venus (Takahashi et al. 2008). In addition to the photometric observations mentioned above, radio occultation experiments obtain vertical profiles of the temperature, sulfuric acid density, and ionospheric electron density with high resolution (Imamura et al. 2011). For this particular experiment, the spacecraft has been equipped with an ultra-stable oscillator, which is identical to the one on Venus Express; thus, comparisons of the results from the two spacecraft are possible.
The Japan Aerospace Exploration Agency (JAXA) successfully launched AKATSUKI at 06:58:22 (JST) on May 21, 2010, with the H-IIA F17 launch vehicle. After the successful cruise from Earth to Venus, which took about half a year, the propulsion system malfunctioned during the Venus orbit insertion (VOI) maneuver on December 7, 2010 (Nakamura et al. 2011; Hirose et al. 2012). The orbital maneuvering engine (OME) was shut down at 158 s during VOI, while 12 min of operation had been planned. Consequently, the spacecraft did not enter Venus’s orbit; instead, it entered an orbit around the Sun with a period of 203 days.
The cause of the malfunction was determined to be an obstruction of the fuel-side check valve, which restricted the passage of fuel into the OME, and hence, the ratio of oxidizer to fuel gradually increased. Eventually, the combustion temperature became too high to operate the OME. The obstruction turned out to be a solid salt that was generated in the check valve during the mixing of fuel and oxidizer vapors along with helium gas, which was needed for pressurization. The vapor of the oxidizer reached the fuel-side check valve because it was able to penetrate through the seal material (polymer) of the valves. At the design phase of the spacecraft, four valves were intentionally installed to avoid the migration of vapor and the potential for unexpected explosions in the pressurized gas line. However, the possibility of vapor transmission through the seal material also should have been carefully considered.
The OME was ultimately found to be broken and unusable, but most of the fuel still remained. Thus, a decision was made to use the reaction control system (RCS) for orbital maneuvers in November 2011, which were successfully executed so that AKATSUKI would re-encounter Venus in 2015.
After the orbital maneuvers in November 2011, the orbital period became 199 days and the encounter with Venus was set for November 22, 2015. This specific date was originally chosen to achieve the shortest encounter time given the spacecraft’s now limited expected lifetime. However, a detailed trajectory analysis revealed that the orbit around Venus after insertion on November 22, 2015, would be unstable. Therefore, to achieve a more stable orbit, another orbital maneuver was performed in July 2015 to set the spacecraft on a trajectory to meet Venus on December 7, 2015.
Figure 2 shows the trajectory of AKATSUKI in relation to the orbits of Venus and Earth. After December 1, 2015, the spacecraft’s orbit was just outside of Venus’s orbit and the velocity of the spacecraft relative to the Sun was less than that of Venus, which allowed Venus to catch up to the spacecraft from the back end. On December 7, 2015, the spacecraft approached the planet from outside of Venus’s orbit and VOI-Revenge 1 (R1) procedure was implemented by using four 23 Newton class thrusters of the RCS.
Figure 3 shows the observed two-way Doppler residuals at the Usuda Deep Space Center 64-m antenna with no-burn trajectory. VOI-R1 burn (1228 s) was successfully achieved from 23:51:29 on December 6 through 00:11:57 on December 7 (UTC, onboard time). On the ground, the burn was observed at an 8-min 19-s delay (radio wave travel time between Venus and the Earth on December 7, 2015). Each colored line shows the case when the injection was interrupted at a certain percentage of the burn duration (e.g., “015” indicates 15 % of the burn duration). This graph shows that, even if the burn was interrupted, the inclination of the Doppler residuals did not become flat because of the spacecraft’s velocity changes caused by Venus. During the burn, the time-series variation of the Doppler residuals provided unique information and was monitored very carefully with the telemetry data sent from the spacecraft.
AKATSUKI is the first Japanese satellite to orbit a planet. After the VOI-R1, the apoapsis altitude was ~440,000 km with an inclination of 3° and orbital period of 13 days and 14 h. Figure 4 shows the VOI-R1 geometry depicted with the Venus center coordinate. For the dual purposes of decreasing the apoapsis altitude and avoiding a long eclipse during the orbit, a trim maneuver was performed at the first periapsis. The apoapsis altitude is now ~360,000 km with a periapsis altitude of 1000–8000 km, and the period is 10 days and 12 h.
New observation plan
To understand the atmospheric dynamics and cloud physics of Venus, onboard science instruments are used to sense multiple height levels of the atmosphere, which enables visualization of the three-dimensional structure and dynamics. Although the new orbit around Venus is much more elongated than the original plan, the science goals and the observation strategy are basically unchanged from the original ones (Nakamura et al. 2011). The spatial resolution to be achieved around the apoapsis was degraded by a factor of 5–6 (“Global imaging” section), which had an influence on the quality of cloud tracking measurements. However, planetary-scale winds are still expected to be retrievable from such images, and high-resolution images obtained at close distances can be used to complement them. Although the frequencies of LAC operations and radio occultation observations became much lower, the lightening observations by LAC are still very unique, and the scientific value of radio occultation observation can be maximized by coordination with the imaging observations. The observation modes are roughly classified into the groups described below in the following four subsections; these observations are conducted sequentially in each orbital revolution (Fig. 5).
Global imaging observations are conducted by using the IR1, IR2, UVI, and LIR in the portion of the orbit where the typical camera field of view (FOV) of 12° exceeds the apparent Venus disk; this condition is satisfied over 96 % of the time in one orbital revolution except for in the near periapsis region. From this portion of the orbit, cloud images will be obtained every 1–2 h for each observation wavelength. The pixel resolution at the Venusian surface from the apoapsis altitude of ~360,000 km is 74 km for UVI, IR1, and IR2 and 300 km for LIR, while it is 12 km for UVI, IR1, and IR2 and 50 km for LIR from the altitude of 58,000 km where the apparent Venus disk fits into the FOV of 12°. Because the orbital period in the original plan would have allowed observations of the full global disk only during 60 % of each orbit (Nakamura et al. 2011), the new orbit enables more continuous global monitoring. Another merit of the new orbit is that the observation geometry is stable over several days at the expense of the lower spatial resolution on average. By using the obtained global images, development of the atmospheric structure can be monitored, and wind vectors can be derived by tracking small-scale cloud features (Kouyama et al. 2012, 2013; Ogohara et al. 2012a, b; Ikegawa and Horinouchi 2016). This continuous and long-term monitoring of Venus will also provide unprecedented life cycle details of the most prominent cloud structure of Venus, the dark Y-feature, which has been interpreted to be a planetary wave that may explain the zonal wind variability and provide key hints about the nature of the mysterious UV absorber (Peralta et al. 2015). Monitoring of surface features on the nightside by IR1, including searches for active volcanism (Hashimoto and Imamura 2001), is also conducted primarily in this observation mode.
The camera pointing direction for this type of observation is not always nadir, but it can be shifted to the sunlit side for dayside imaging and to the dark side for nightside imaging. The purposes of this angular offset are (1) to include the planetary limb in the image so that the pointing direction can be determined accurately from the limb position, (2) to maximize the area of the atmosphere or the surface observable with each filter, and (3) to avoid stray light when observing the nightside.
In this observation mode, a particular point on the cloud layer is continuously monitored by using the UVI, IR1, IR2, and LIR from distances shorter than ~50,000 km for the purpose of observing the temporal development of mesoscale processes and also for stereo-viewing of the cloud tops. The pixel resolution at the Venusian surface is 0.2–1.6 km for UVI, IR1, and IR2 and 0.9–7.0 km for LIR from the periapsis altitude of 1000–8000 km. During this observation sequence, the spacecraft attitude is controlled so that the camera FOV continuously captures roughly the same region of the cloud tops.
The vertical distribution of aerosols that extend up to ~100 km altitude is observed with the limb-viewing geometry around the dayside periapsis passages by using UVI, IR1 (0.90 μm), and LIR. The layered distribution of aerosols seen in the limb images taken by the Galileo solid-state imager (SSI) (Belton et al. 1991) and Venus Express VMC (Titov et al. 2012) suggests that unknown chemical/dynamical processes are at work in aerosol formation; extensive observations covering wider regions with multiple wavelengths should provide clues to the mechanism. When the periapsis altitude is 1000 km, the minimum distance to the tangential point is 3500 km, and this gives a vertical resolution of 0.7 km for UVI and IR1 and 3 km for LIR.
The eclipse (umbra) region along the orbit is allocated to lightning observations by LAC. Eclipses occur mostly near the periapsis with a typical duration of 30 min. LAC is operated in nadir-pointing geometry and waits for lightning flashes to collect data with an event trigger method. LAC can also observe night airglows by continuously recording the brightness along swaths scanned by the attitude maneuver or the orbital motion of the spacecraft.
Radio occultation experiments (RS) that use an ultra-stable oscillator (USO) are performed when the spacecraft is hidden by Venus as viewed from the tracking station (Imamura et al. 2011). Venus Express radio occultation has revealed vertical temperature profiles at various locations and local times (Tellmann et al. 2009); one merit of the AKATSUKI’s observation system is that the location probed by RS can be observed by the cameras a short time before the ingress or short time after the egress because of the equatorial orbit, thus enabling quasi-simultaneous observations. Since the dense Venusian atmosphere causes considerable ray bending exceeding several tens of degrees, spacecraft steering is required to compensate for this effect while the occultation geometry changes from ingress occultation to egress occultation.
First images of Venus by the cameras
AKATSUKI took images of Venus immediately after the VOI-R1 with the following three instruments: IR1, UVI, and LIR. The other two instruments (IR2 and LAC) were not operated at this time because their functions had not been checked before the VOI-R1. The first images of Venus were taken at the positions of ~67,000 km for IR1 and ~72,000 km for UVI and LIR, far from the Venus disk. The solar phase angle at the sub-observer point was ~45° with the evening terminator in view (Fig. 4). Figure 6a–c shows the images taken by IR1, UVI, and LIR, respectively, and Table 1 presents a summary of the observations. No data reduction procedures have been performed for the images except for several onboard processing steps (i.e., median filtering and subtraction of the dark current for IR1 and UVI, desmearing for UVI, and accumulation of 32 images and subtraction of a shutter image for LIR).
The IR1 image shows the 0.90-μm solar radiation scattered by the upper clouds (Iwagami et al. 2011). This channel is centered on the continuum. Although the area near the eastern limb was not visible because of the limited operation of the discrete attitude control (in spite of the quick orbital motion of AKATSUKI), it was confirmed that Venus has a faint appearance over the entire disk in this channel. Belton et al. (1991) showed from the 0.986-μm images obtained by the Galileo SSI that Venus has a contrast of 3 % after the removal of terminator and limb brightness gradients. The contrast sources for the IR1 images, together with those for the IR2 and LIR images, are discussed in Takagi and Iwagami (2011). The continuous IR1 images with such contrast will be used to sound horizontal cloud-tracked velocities near the base of the upper clouds (58–64 km) (e.g., Peralta et al. 2007; Sánchez-Lavega et al. 2008).
The UVI image at a wavelength of 283 nm reflects the spatial distribution of SO2, which attenuates solar radiation scattered by clouds at cloud level, and that of the upper haze, which enhances scattering. This is the first time a snapshot of Venus has been captured at this wavelength. Relatively bright cell-like structures exist in the low latitudes. Dark and bright streaky structures, which form part of the bow shape, become prominent in the midlatitudes. Bright polar bands are also clearly seen in the high latitudes. Although this channel is outside of the band of the unknown UV absorber, which was measured by previous spacecraft (Pioneer Venus, Galileo, and Venus Express), the morphology at 283 nm was found to be similar to those seen in previous UV images. Together with the other UVI image at a wavelength of 365 nm, the continuous UVI images will be used to derive horizontal cloud-tracked velocities near the cloud top altitudes of 62–70 km (e.g., Kouyama et al. 2012, 2013; Ogohara et al. 2012a, b; Ikegawa and Horinouchi 2016). The spatial resolution of the IR1 and UVI images shown in Fig. 6a, b is ~15 km/pixel, which is three or four times better than that (~50 km/pixel) of the images obtained by the Venus Express VMC near the apocenter (Titov et al. 2012). Comparisons between the time series of the images at the two channels (283 and 365 nm) will also shed light on their relationship with the cloud top structure. The solar phase angle dependence of aerosol scattering and dark-bright contrasts will be used to develop an aerosol model and determine the vertical distribution of UV absorbers, SO2, and the unknown UV absorber (Lee et al. 2015; Petrova et al. 2015; Satoh et al. 2015). This aerosol model will be taken into account in albedo calculations, and the optical depth of the UV absorbers can be estimated in a similar manner to method used by Molaverdikhani et al. (2012). Ground-based observations will also be useful for evaluating the gaseous SO2 distribution over the planet; an example can be found in Encrenaz et al. (2013).
The LIR image shows the thermal radiation emitted from the cloud top altitudes with a single band-pass filter of 8–12 μm (Taguchi et al. 2007; Fukuhara et al. 2011). This is a composite image that was made by superimposing 32 raw images to improve the signal-to-noise ratio. A shutter image was subtracted from the Venus image to correct a pixel-to-pixel variation in offset. No correction for thermal radiation from the LIR itself was performed. The spatial resolution of the LIR image is ~60 km/pixel, which is the highest spatial resolution image of Venus ever obtained in the mid-infrared wavelengths. The southern polar region is the brightest (highest in temperature) region, which corresponds to the polar dipole. Even after considering that the sub-observer latitude is at ~7°S, it is apparent that north–south asymmetry in the brightness of the polar regions exists. The streaky structures seen in the UVI image are also visible in the midlatitudes. Of particular interest is the bright bow-like structure extending toward high latitudes near the evening terminator, which was not seen in the previous LIR images captured just after the VOI failure in December 2010 (Taguchi et al. 2012). Such a bow-like structure is also evident in the ground-based mid-infrared images, but it appeared as a dark feature (Sato et al. 2014). Continuous monitoring of the cloud top morphology will provide clues for understanding what mechanism causes such an interesting feature.
In 2010, Japan’s first trial to put the spacecraft AKATSUKI into orbit around Venus was unsuccessful. Since that time, ISAS has investigated the cause of the malfunction during the first orbit insertion and made a second challenging attempt at Venus orbit insertion in 2015 with the injured spacecraft. The second orbit insertion was executed flawlessly, and AKATSUKI will be able to achieve all science objectives in the new science orbit. All AKATSUKI instruments are working well, and the first images have already provided new and intriguing observations of Venus. AKATSUKI will continue to send data for two or more years, and planetary exploration by Japan will enter a new era when AKATSUKI continuously delivers data to the world on the changing planet.
field of view
1-μm infrared camera
2-μm infrared camera
Institute of Space and Astronautical Science
Japan Aerospace Exploration Agency
lightning and airglow camera
long-wave infrared camera
orbital maneuver engine
reaction control system
radio occultation experiments
Venus monitoring camera
Venus orbit insertion on December 7, 2010
Venus orbit insertion-revenge 1
Baines KH et al (2000) Detection of sub-micron radiation from the surface of Venus by Cassini/VIMS. Icarus 148:307–311
Belton MJS et al (1991) Imaging from Galileo of the Venus cloud deck. Science 253:1531–1536
Chicarro A, Martin P, Traunter R (2004) The Mars Express mission: an overview. In: Wilson A (ed) Mars Express. European Space Agency Publication Division, Noordwijk, pp 3–16
Colin L (1983) Basic facts about Venus. In: Hunten DM, Colin L, Donahue TM, Morozet VI (eds) Venus. University of Arizona Press, Tucson, pp 10–26
Encrenaz T, Greathouse TK, Richter MJ, Lacy J, Widemann T, Bézard B, Fouchet T, deWitt C, Atreya SK (2013) HDO and SO2 thermal mapping on Venus. II. The SO2 spatial distribution above and within the clouds. Astron Astrophys 559:A65. doi:10.1051/0004-6361/201322264
Fukuhara T, Taguchi M, Imamura T, Nakamura M, Ueno M, Suzuki M, Iwagami N, Sato M, Mitsuyama K, Hashimoto GL, Ohshima R, Kouyama T, Ando H, Futaguchi M (2011) LIR: longwave infrared camera onboard the Venus orbiter Akatsuki. Earth Planets Space 63:1009–1018
Hashimoto GL, Imamura T (2001) Elucidating the rate of volcanism on Venus: detection of lava eruptions using near-infrared observations. Icarus 154:239–243
Hashimoto GL, Sugita S (2003) On observing the compositional variability of the surface of Venus using nightside near-infrared thermal radiation. J Geophys Res 108:5109. doi:10.1029/2003JE002082
Hashimoto GL, Roos-Serote M, Sugita S, Gilmore MS, Kamp LW, Carlson RW, Baines KH (2008) Felsic highland crust on Venus suggested by Galileo near-infrared mapping spectrometer data. J Geophys Res 113:E00B24. doi:10.1029/2008JE003134
Hirose C, Ishii N, Kawakatsu Y, Ukai C, Terada H (2012) The trajectory control strategies for Akatsuki re-insertion into the Venus orbit. In: Proceedings of the 23rd international symposium on space flight dynamics
Ikegawa S, Horinouchi T (2016) Improved automatic estimation of winds at the cloud top of Venus using superposition of cross-correlation surfaces. Icarus 271:98–119
Imamura T, Toda T, Tomiki A, Hirahara D, Hayashiyama T, Mochizuki N, Yaamoto Z, Abe T, Iwata T, Noda H, Futaana Y, Ando H, Häusler B, Pätzold M, Nabatov A (2011) Radio occultation experiment of the Venus atmosphere and ionosphere with the Venus orbiter Akatsuki. Earth Planets Space 63:493–501
Iwagami N, Takagi S, Ohtsuki S, Ueno M, Uemizu K, Satoh T, Sakanoi T, Hashimoto GL (2011) Science requirements and description of the 1 μm camera onboard the Akatsuki Venus Orbiter. Earth Planets Space 63:487–492
Kouyama T, Imamura T, Nakamura M, Satoh T, Futaana Y (2012) Horizontal structure of planetary-scale waves at the cloud top of Venus deduced from Galileo SSI images with an improved cloud-tracking technique. Planet Space Sci 60:207–216
Kouyama T, Imamura T, Nakamura M, Satoh T, Futaana Y (2013) Long-term variation in the cloud-tracked zonal velocities at the cloud top of Venus deduced from Venus Express VMC images. J Geophys Res 118:37–46. doi:10.1029/2011JE004013
Lee YJ, Imamura T, Schröder SE, Marcq E (2015) Long-term variations of the UV contrast on Venus observed by the Venus monitoring camera on board Venus Express. Icarus 253:1–15. doi:10.1016/j.icarus.2015.02.015
Lellouch E, Clancy T, Crisp D, Kliore AJ, Titov D, Bougher SW (1997) Near-infrared sounding of the lower atmosphere of Venus. In: Bougher SW, Hunten DM, Phillips RJ (eds) Venus II. University of Arizona Press, Tucson, pp 295–321
Markiewicz WJ et al (2007) Venus monitoring camera for Venus Express. Planet Space Sci 55:1701–1711
Molaverdikhani K, McGouldricK K, Esposito LW (2012) The abundance and vertical distribution of the unknown ultraviolet absorber in the Venusian atmosphere from analysis of Venus Monitoring Camera images. Icarus 217:648–660
Moroz VI (1981) The atmosphere of Venus. Space Sci Rev 29:3–127
Nakamura M, Imamura T, Ueno M, Iwagami N, Satoh T, Watanabe S, Taguchi M, Takahashi Y, Suzuki M, Abe T, Hashimoto GL, Sakanoi T, Okano S, Kasaba Y, Yoshida J, Yamada M, Ishii N, Yamada T, Uemizu K, Fukuhara T, Oyama K (2007) Planet-C: Venus climate orbiter mission of Japan. Planet Space Sci 55:1831–1842
Nakamura M, Imamura T, Ishii N, Abe T, Satoh T, Suzuki M, Ueno M, Yamazaki A, Iwagami N, Watanabe S, Taguchi M, Fukuhara T, Takahashi Y, Yamada M, Hoshino N, Ohtsuki S, Uemizu K, Hashimoto GL, Takagi M, Matsuda Y, Ogohara K, Sato N, Kasaba Y, Kouyama T, Hirata N, Nakamura R, Yamamoto Y, Okada N, Horinouchi T, Yamamoto M, Hayashi Y (2011) Overview of Venus orbiter, Akatsuki. Earth Planets Space 63:443–457
Nakamura M, Kawakatsu Y, Hirose C, Imamura T, Ishii N, Abe T, Yamazaki A, Yamada M, Ogohara K, Uemizu K, Fukuhara T, Ohtsuki S, Satoh T, Suzuki M, Ueno M, Nakatsuka J, Iwagami N, Taguchi M, Watanabe S, Takahashi Y, Hashimoto GL, Yamamoto H (2014) Return to Venus of the Japanese Venus climate orbiter AKATSUKI. Acta Astronaut 93:384–389
Ogohara K, Kouyama T, Yamamoto H, Sato N, Takagi M, Imamura T (2012a) A newly developed cloud tracking system for the Venus climate orbiter Akatsuki and preliminary results using Venus Express data. Theor Appl Mech Jpn 60:195–204
Ogohara K, Kouyama T, Yamamoto H, Sato N, Takagi M, Imamura T (2012b) Automated cloud tracking system for the Akatsuki Venus climate orbiter data. Icarus 217:661–668. doi:10.1016/j.icarus.2011.05.017
Peralta J, Hueso R, Sánchez-Lavega A (2007) A reanalysis of Venus winds at two cloud levels from Galileo SSI images. Icarus 190:469–477
Peralta J, Sánchez-Lavega A, López-Valverde MA, Luz D, Machado P (2015) Venus’s major cloud feature as an equatorially trapped wave distorted by the wind. Geophys Res Lett 42:705–711. doi:10.1002/2014GL062280
Petrova EV, Shalygina OS, Markiewicz WJ (2015) UV contrasts and microphysical properties of the upper clouds of Venus from the UV and NIR VMC/VEx images. Icarus 260:190–204. doi:10.1016/j.icarus.2015.07.015
Sánchez-Lavega A et al (2008) Variable winds on Venus mapped in three dimensions. Geophys Res Lett 35:L13204. doi:10.1029/2008GL033817
Sato TM, Sagawa H, Kouyama T, Mitsuyama K, Satoh T, Ohtsuki S, Ueno M, Kasaba Y, Nakamura M, Imamura T (2014) Cloud top structure of Venus revealed by Subaru/COMICS mid-infrared images. Icarus 243:386–399
Satoh T, Ohtsuki S, Iwagami N, Ueno M, Uemizu K, Suzuki M, Hashimoto GL, Sakanoi T, Kasaba Y, Nakamura R, Imamura T, Nakamura M, Fukuhara T, Yamazaki A, Yamada M (2015) Venus’ clouds inferred from the phase curves acquired by IR1 and IR2 on board Akatsuki. Icarus 248:213–220
Schubert G (1983) General circulation and dynamical state of the Venus atmosphere. In: Hunten DM, Colin L, Donahue TM, Morozet VI (eds) Venus. University of Arizona Press, Tucson, pp 681–765
Svedhem H et al (2007) Venus Express—the first European mission to Venus. Planet Space Sci 55:1636–1652
Taguchi M, Fukuhara T, Imamura T, Nakamura M, Iwagami N, Ueno M, Suzuki M, Hashimoto GL, Mitsuyama K (2007) Longwave infrared camera onboard the Venus climate orbiter. Adv Space Res 40:861–868
Taguchi M, Fukuhara T, Futaguchi M, Sato M, Imamura T, Mitsuyama K, Nakamura M, Ueno M, Suzuki M, Iwagami N, Hashimoto GL (2012) Characteristic features in Venus’ nightside cloud-top temperature obtained by Akatsuki/LIR. Icarus 219:502–504
Takagi S, Iwagami N (2011) Contrast sources for the IR images taken by the Venus mission AKATSUKI. Earth Planets Space 63:435–442
Takahashi Y, Yoshida J, Yair Y, Imamura T, Nakamura M (2008) Lightning detection by LAC onboard the Japanese Venus climate orbiter. Planet-C Space Sci Rev 137:317–334
Taylor FW, Beer R, Chahine MT, Diner DJ, Elson LS, Haskins RD, McCleese DJ, Martonchik JV, Reichley PE (1980) Structure and meteorology of the middle atmosphere of Venus: infrared remote sensing from the Pioneer Orbiter. J Geophys Res 85:7963–8006
Taylor FW, Crisp D, Bezard B (1997) Near-infrared sounding of the lower atmosphere of Venus. In: Bougher SW, Hunten DM, Phillips RJ (eds) Venus II. University of Arizona Press, Tucson, pp 325–352
Tellmann S, Pätzold M, Häusler B, Bird BM, Tyler GL (2009) Structure of the Venus neutral atmosphere as observed by the Radio Science experiment VeRa on Venus Express. J Geophys Res 114:E00B36. doi:10.1029/2008JE003204
Titov DV et al (2012) Morphology of the cloud tops as observed by the Venus Express monitoring camera. Icarus 217:682–701
For the AKATSUKI project of ISAS/JAXA, NM was the project manager, IT was the project scientist, and IN was the project engineer. KY, HC, NJ, IT, IK, TT, TH, TS, NS, HT, HA, and KY were core members of the engineering team. AT, ST, SM, UM, YA, IN, WS, TM, FT, TY, YM, IM, OS, UK, HGL, TM, MY, OK, SN, KY, KT, HN, NR, YY, HT, YM, HY-Y, KH, SK, ST, AH, MS, STM, TS, NK, PJ, and LYJ were core members of the science team. Some members of the science team served as principal investigators (PIs) of the scientific instruments; specifically, WS, IN, ST, TM, TY, and IT were PIs for the work involving the UVI, IR1, IR2, LIR, LAC, and RS, respectively. All authors read and approved the final manuscript.
We gratefully thank NEC corporation, Fujitsu Limited, Sumitomo Heavy Industries, Ltd., Nikon Corporation, Mitsubishi Heavy Industries, Ltd., IHI AEROSPACE Co., Ltd., Meisei Electric Co., Ltd., Mitsubishi Electric Corporation, Hamamatsu Photonics K.K., NEC Space Technologies, Ltd., Space Engineering Development Co., Ltd., FUJITOK Corporation, K. K. MAGOSHI, and TimeTech GmbH for their contribution to the design, manufacturing, and operation of AKATSUKI since 2001.
The authors declare that they have no competing interests.
About this article
Cite this article
Nakamura, M., Imamura, T., Ishii, N. et al. AKATSUKI returns to Venus. Earth Planet Sp 68, 75 (2016). https://doi.org/10.1186/s40623-016-0457-6 | 0.834749 | 3.661483 |
After making numerous discoveries beyond Neptune's orbit, astronomer Scott Sheppard of the Carnegie Institute for Science, returned to the news with the announcement of the existence of 12 new moons around Jupiter. The communiqué was made today (July 17) by the International Astronomical Union. To make the discovery, Sheppard and his team used the telescope of the Dark Energy Camera (DECam), an extremely sensitive instrument built at the observatory of Cerro Tololo, Chile.
e) accustomed to the equipment since 2012, when they began to search cosmic objects beyond Neptune, the researchers decided to innovate and not focus only on the distant stars, but take advantage to also detect events Closer, like Jupiter's, for example. "We just wanted to be the most efficient possible," explains Sheppard in an interview with Wired magazine. With years of experience, Sheppard knew that the DECAM telescope was able to find smaller and darker objects, unlike other instruments that had already scoured that part of space. Since the beginning of last year, astronomers have found about two dozen stars that would appear to behave like satellites. That is, they had a predictable orbit around Jupiter. But only in May this year that came confirmation: 12 of them actually have a regular orbit and can now be called Jupiter's moons — which now oozes in the sky 79 known satellites.
One of the ways to understand the origin and to classify Jupiter's moons is through its distance from the planet. The closest ones are also the largest and are called Galileo's moons. Far from them, about 10 million miles away, are the "Prógradas" moons, which move in the same direction as the planet rotates. At a distance twice as long as the prógradas, we can find the smaller, retrograde satellites that orbit in the opposite direction to Jupiter's rotation. Why the existence of these three distinct regions of satellites around Jupiter is still unknown, but astronomers have a chance. Most of them believe that they can indicate that millions of years ago, a trio of celestial bodies approached the planet and, for reasons also unknown, were disintegrated and formed the layers observed today. The most accepted assumption is that these objects collided with a fourth body of uncertain identity (could have been an asteroid or a comet, for example). Another theory is that the collision has occurred between satellites, but it is somewhat discredited, since the distance between Prógradas and retrograde moons is too great for there to be a collision. That's where the cat jump comes in: Astronomers have discovered two Prógradas moons, nine retrogrades and a Prógrada moon that crosses the path of the retrograde region. "She's basically driving down the road in the wrong direction," Sheppard says. "And that makes the situation very unstable." The moon "The Border" was baptized by the astronomers of Valetudo, name of the granddaughter of the Roman god Jupiter. It is the smallest and weakest satellite of Jupiter ever found, measuring less than a kilometer wide. For astronomers, it originally had a much larger size, but because it collided with other celestial bodies in the retrograde region, it was reduced to this size. With 12 more objects discovered in the curriculum, Sheppard states that the group's next step is to discover the composition of the new moons. They, however, are difficult to observe and a trip to Jupiter to analyze them is out of the question. "That's probably never going to happen," says the astronomer. It remains to be hoped that some of the next missions to the largest planet in the Solar system crosses the unexpected path of Valetudo. with information from Wired. | 0.911018 | 3.82974 |
Scientists on Wednesday revealed the first image ever made of a black hole, depicting a fiery orange and black ring of gravity-twisted light swirling around the edge of the abyss.
The picture, assembled from data gathered by eight radio telescopes around the world, shows the hot, shadowy lip of a supermassive black hole, one of the light-sucking monsters of the universe theorized by Einstein more than a century ago and confirmed by observations for decades. It is along this edge that light bends around itself in a cosmic funhouse effect.
"We have seen what we thought was unseeable. We have seen and taken a picture of a black hole. Here it is," said Sheperd Doeleman of Harvard, leader of a team of about 200 scientists from 20 countries.
University of Waterloo physicist Avery Broderick, a co-discoverer, declared: "Science fiction has become science fact."
In fact, Jessica Dempsey, a co-discoverer and deputy director of the East Asian Observatory in Hawaii, said the fiery circle reminded her of the flaming Eye of Sauron from the "Lord of the Rings" trilogy.
Unlike smaller black holes that come from collapsed stars, supermassive black holes are mysterious in origin. Situated at the centre of most galaxies, including ours, they are so dense that nothing, not even light, can escape their gravitational pull. This one's "event horizon" — the precipice, or point of no return, where light and matter begin to fall inexorably into the hole — is as big as our entire solar system.
Three years ago, scientists using an extraordinarily sensitive observing system heard the sound of two much smaller black holes merging to create a gravitational wave, as Albert Einstein predicted. The new image, published in the Astrophysical Journal Letters and announced around the world, adds light to that sound.
Outside scientists suggested the achievement could be worthy of a Nobel Prize, just like the gravitational wave discovery.
The image helps confirm Einstein's general theory of relativity, Dempsey said. Einstein a century ago even predicted the symmetrical shape that scientists just found.
The black hole depicted is about 6 billion times the mass of our sun and is in a galaxy called M87 that is about 53 million light years from Earth. One light year is 5.9 trillion miles, or 9.5 trillion kilometres.
While much of the matter around a black hole gets sucked into the vortex, never to be seen again, the new picture captures gas and dust that are lucky to be circling just far enough to be safe and to be seen millions of years later on Earth.
The measurements were taken at a wavelength the human eye cannot see, so the astronomers added colour to the image, choosing gold and orange because the light and gas are so hot, heated to millions of degrees by the friction of gravity.
That gravity creates a funhouse effect where you can see light from both behind the black hole and behind you as the light curves and circles around the black hole.
The project cost $50 million to $60 million, with $26 million of that coming from the National Science Foundation.
Johns Hopkins astrophysicist Ethan Vishniac, who was not part of the discovery team but edits the journal where the research was published, pronounced the image "an amazing technical achievement" that "gives us a glimpse of gravity in its most extreme manifestation."
He added: "Pictures from computer simulations can be very pretty, but there's literally nothing like a picture of the real universe, however fuzzy and monochromatic."
"It's just seriously cool," said John Kormendy, a University of Texas astronomer who wasn't part of the discovery team. "To see the stuff going down the tubes, so to speak, to see it firsthand. The mystique of black holes in the community is very substantial. That mystique is going to be made more real."
Myth says a black hole would rip you apart, but scientists said that because of the particular forces exerted by an object this big, someone could fall into it and not be torn to pieces. But the person would never be heard from again.
Black holes are "like the walls of a prison. Once you cross it, you will never be able to get out and you will never be able to communicate," said astronomer Avi Loeb, who is director of the Black Hole Initiative at Harvard but was not involved in the discovery.
The telescope data was gathered two years ago, over four days when the weather had to be just right all around the world. Completing the image was an enormous undertaking, involving an international team of scientists, supercomputers, hundreds of terabytes of data.
"We've been hunting this for a long time," Dempsey said. "We've been getting closer and closer with better technology."
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
Seth Borenstein, The Associated Press | 0.875006 | 3.841086 |
Scientists have obtained their best measurement yet of the size and contents of a neutron star, an ultra-dense object containing the strangest and rarest matter in the Universe.
This measurement may lead to a better understanding of nature’s building blocks — protons, neutrons and their constituent quarks — as they are compressed inside the neutron star to a density trillions of times greater than on Earth.
Dr. Tod Strohmayer of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleague, Adam Villarreal, a graduate student at the University of Arizona, present these results today during a Web-based press conference in New Orleans at the meeting of the High Energy Astrophysics Division of the American Astronomical Society.
They said their best estimate of the radius of a neutron star is 7 miles (11.5 kilometers), plus or minus a stroll around the French Quarter. The mass appears to be 1.75 times that of the Sun, more massive than some theories predict. They made their measurements with NASA’s Rossi X-ray Timing Explorer and archived X-ray data
The long-sought mass-radius relation defines the neutron star’s internal density and pressure relationship, the so-called equation of state. And this, in turn, determines what kind of matter can exist inside a neutron star. The contents offer a crucial test for theories describing the fundamental nature of matter and energy and the strength of nuclear interactions.
“We would really like to get our hands on the stuff at the center of a neutron star,” said Strohmayer. “But since we can’t do that, this is about the next best thing. A neutron star is a cosmic laboratory and provides the only opportunity to see the effects of matter compressed to such a degree.”
A neutron star is the core remains of a star once bigger than the Sun. The interior contains matter under forces that perhaps existed at the moment of the Big Bang but which cannot be duplicated on Earth. The neutron star in today’s announcement is part of a binary star system named EXO 0748-676, located in the constellation Volans, or Flying Fish, about 30,000 light-years away, visible in southern skies with a large backyard telescope.
In this system, gas from a “normal” companion star plunges onto the neutron star, attracted by gravity. This triggers thermonuclear explosions on the neutron star surface that illuminate the region. Such bursts often reveal the spin rate of the neutron star through a flickering in the X-ray light emitted, called a burst oscillation. (Refer to Items 1 – 6 for an artist’s concept of this process. A movie and a detailed caption can be found in the blue column on the right.)
The scientists detected a 45-hertz burst oscillation frequency, which corresponds to a neutron star spin rate of 45 times per second. This is a leisurely pace for neutron stars, which are often seen spinning over 300 times per second.
The scientists next capitalized on EXO 0748-676 observations with the European Space Agency’s XMM-Newton satellite from 2002, led by Dr. Jean Cottam of NASA Goddard. Cottam’s team had detected spectral lines emitted by hot gas, similar in look to the lines of a cardiogram. These lines had two features. First, they were Doppler shifted. This means the energy detected was an average of the light spinning around the neutron star, moving away from us and then towards us. Second, the lines were gravitationally redshifted. This means that gravity pulled on the light as it tried to escape the region, stealing a bit of its energy.
Strohmayer and Villarreal determined that the 45-hertz frequency and the observed line widths from Doppler shifting are consistent with a neutron star radius between 9.5 and 15 kilometers, with the best estimate at 11.5 kilometers. The relationship among burst frequency, Doppler shifting and radius is that the velocity of gas swirling around the star’s surface depends on the star’s radius and its spin rate. In essence, a faster spin corresponds to a wider spectral line (a technique similar to how a state trooper can detect speeding cars).
Cottam team’s gravitational redshift measurement offered the first measure of a mass-radius ratio, albeit without knowledge of a mass and radius. This is because the degree of redshifting (strength of gravity) depends on the mass and radius of the neutron star. Some scientists had questioned this measurement, for the spectral lines detected seemed too narrow. The new results strengthen the gravitational redshift interpretation of the Cottam team’s spectral lines (and thus the mass-radius ratio) because a slower-spinning star can easily produce such relatively narrow lines.
So, ever more confident of the mass-radius ratio and now knowing the radius, the scientists could calculate the neutron star’s mass. The value was between 1.5 and 2.3 solar masses, with the best estimate at 1.75 solar masses.
The result supports the theory that matter in the neutron star in EXO 0748-676 is packed so tightly that almost all protons and electrons are squeezed into neutrons, which swirl about as a superfluid, a liquid that flows without friction. Yet the matter isn’t packed so tightly that quarks are liberated, a so-called quark star.
“Our results are really starting to put the squeeze on the neutron star equation of state,” said Villareal. “It looks like equations of state which predict either very large or very small stars are nearly excluded. Perhaps more exciting is that we now have an observational technique that should allow us to measure the mass-radius relations in other neutron stars.”
A proposed NASA mission called the Constellation X-ray Observatory would have the ability to make such measurements, but with much greater precision, for a number of neutron star systems.
Original Source: NASA News Release | 0.93207 | 3.969525 |
Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered and is the largest known plutoid (or ice dwarf).
Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union (IAU) to define the term "planet" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet.
Pluto is the largest and second-most-massive (after Eris) known dwarf planet in the Solar System, and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.5 AU).
Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra. Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.
The New Horizons spacecraft performed a flyby of Pluto on July 14, 2015, becoming the first ever spacecraft to do so. During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons. In September 2016, astronomers announced that the reddish-brown cap of the north pole of Charon is composed of tholins, organic macromolecules that may be ingredients for the emergence of life, and produced from methane, nitrogen and other gases released from the atmosphere of Pluto and transferred about 19,000 km (12,000 mi) to the orbiting moon. | 0.825481 | 3.873047 |
Mapping dark matter in galaxies
A multitude of faint galaxies, small luminous dots scattered over the dark sky, was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. Images such as this one are powerful tools to understand how dark matter is distributed in galaxies.
The picture is part of the COMBO-17 survey (Classifying Objects by Medium-Band Observations in 17 Filters), a project dedicated to recording detailed images of small patches of the sky through filters of 17 different colours. The area covered in this image is only about the size of the full Moon, but thousands of galaxies can be identified just within this small region.
The image was taken with an exposure time of almost seven hours, which allowed the camera to capture the light from very faint and distant objects, as well as those that are closer to us. Galaxies with clear and regular structures, such as the spiral specimen viewed edge-on near the upper left corner, are only up to a few billion light-years away. The fainter, fuzzier objects are so far away that it has taken nine or ten billion years for their light to reach us.
The COMBO-17 survey is a powerful tool for studying the distribution of dark matter in galaxies. Dark matter is a mysterious substance that does not emit or absorb light and can only be detected by its gravitational pull on other objects. Some of the closer galaxies pictured act as lenses that distort the light coming from more distant galaxies placed along the same line of sight. By measuring this distortion, an effect known as gravitational lensing, astronomers are able to understand how dark matter is distributed in the objects that act as lenses.
The distortion is weak and, therefore, almost imperceptible to the human eye. However, because surveying the sky with 17 filters allows extremely precise distance measurements, it is possible to determine if two galaxies that appear to lie close to each other are actually at very different distances from the Earth. After identifying the galactic lensing systems, the distortion can be measured by averaging over thousands of galaxies. With more than 4000 galactic lenses identified, this COMBO-17 survey is an ideal method to help astronomers to understand the dark matter better.
This image was taken with three of the 17 filters from the project: B (blue), V (green), and R (red). Data through an additional near-infrared filter was also used.
About the Image
|Release date:||9 January 2012, 10:00|
|Size:||7664 x 6961 px|
About the Object
|Type:||Early Universe : Galaxy : Grouping : Cluster|
|Position (RA):||11 42 55.95|
|Position (Dec):||-1° 42' 41.29"|
|Field of view:||30.41 x 27.62 arcminutes|
|Orientation:||North is 0.1° right of vertical|
Colours & filters
|440 nm||MPG/ESO 2.2-metre telescope|
|550 nm||MPG/ESO 2.2-metre telescope|
|650 nm||MPG/ESO 2.2-metre telescope| | 0.888096 | 4.055183 |
This Month’s Hobby: Make Your Own Telescope!
Based on super popular demand from all you young space enthusiasts, this month’s hobby is Amateur Astronomy! People all over the world have been studying the sky for centuries. While everyone knows a little about astronomy, there’s a popular misconception associated with it – astronomy is difficult and complicated.
This is not true at all! You can take up amateur astronomy right from your terrace!
And guess what? Amateur astronomers can even help space institutes like NASA find new planets and stars!
Step 1: Getting the time and place right
Find a spot where you can see a large patch of the sky and check the sky at different times of the night to see when you can see the stars and celestial bodies clearly.
Step 2: Noticing Patterns
Notice if you can spot any patterns of shiny objects in the sky, and familiarise yourself with these patterns. See if the positions of these patterns change over time and make a note.
Step 3: A Map for the stars!
Find a star map/chart for your location. There are various websites where you can get this information easily. You will need to enter your city, time (when you will be viewing the sky) and the date. Once you get a map of the stars, try spotting the patterns you’ve noticed in the sky on the map! This will help you identify the planets, stars, and constellations.
To get started right away, here is a list of celestial objects that can be seen all around the world with the naked eye:
- Venus: This bright planet can be found near the sun during sunset or sunrise.
- Big Dipper: A famous constellation that is made of up seven stars and looks like a cup with a long handle.
- North Star: This star is in the direction of the geographic North Pole. It is near the Big Dipper and is the brightest start in the night sky.
- Orion The Hunter: Another famous constellation made up of 7 stars, the easiest way to spot Orion is to look for 3 stars in an almost straight line that form Orion’s “belt”.
- Moon: The size and shape of the moon change every day and tracking the phases of the moon are basics in astronomy!
Once you’re familiar with the celestial bodies in the sky, to help you observe them better, you can make your own telescope! Here’s how:
The sky that we live under, is full of interesting objects. You just need a little curiosity and the spirit to keep learning to understand it’s secrets.
What did you learn about amateur astronomy from this article? Will you take it up as a hobby?
Deepthi is an ambivert who is on a steady diet of good food, filter coffee, and self-improvement. Being an ardent reader, storytelling has been her first love and she enjoys exploring how to convey stories compellingly. Having studied psychology and experienced the learning and development field, Deepthi is driven to understand human behavior and to know what makes each of us unique. You are most likely to find her tucked into a cozy corner at a local cafe with a Kindle or a book in hand. If you find her there, stop by and say hello, she’d be eager to learn your story too. Until then, you can ping her at [email protected] for anything you may like to share. | 0.831128 | 3.058721 |
Astronomers using the Hubble Space Telescope have discovered a planet where it may be raining, just like on Earth. They detected clouds of water vapour in the alien world’s atmosphere, increasing chances that it could be home to life.
The planet, dubbed K2-18b, lies 111 light-years away. It orbits in the habitable zone of its red dwarf star and so enjoys temperatures similar to those on our own world.
Björn Benneke, of the University of Montreal, who led the discovery team, said: “This represents the biggest step yet taken towards our ultimate goal of finding life on other planets, of proving that we are not alone.
“Thanks to our observations and our climate model of this planet, we have shown that its water vapour can condense into liquid water. This is a first.”
The planet where it may be raining, which lies in the constellation of Leo, was discovered by NASA’s Kepler Space Telescope in 2015. Early observations indicated that it was nine times the size of Earth. Since then, astronomers have been eager to learn more about it.
Professor Benneke’s team used Hubble data to monitor the planet as it orbits its star every 33 days. The planet passes in front of the star so that, for a brief moment, the star’s light shines
through the planet’s atmosphere.
Hubble made eight observations of these transits, each lasting 6.5 hours. Further observations were made with another NASA space telescope, Spitzer.
This allowed the astronomers to find signatures in the light that showed what the atmosphere is made of. It has previously been near impossible to probe the atmospheric conditions on alien planets, but Hubble’s powerful eye came up trumps.
The team’s results, published yesterday online, show that planet K2-18b’s similarities to Earth suggest that it may have a similar water cycle where water condenses into clouds allowing liquid water rain to fall.
The paper’s conclusions say: “The discovery of water absorption in the atmosphere of the habitable-zone exoplanet K2-18b represents a milestone in our search for habitable worlds outside the Solar System.
“Given the relatively low irradiation by the star, K2-18b’s temperature is low enough that the detected water vapor can plausibly condense to form liquid droplets. It is therefore possible that liquid water rain precipitates in the mid-atmosphere of K2-18b.”
The star, K2-18, is of the type M3 and much cooler than our own Sun, but the planet lies closer to it, and so enjoys very similar warmth.
The planet where it may be raining will be a prime candidate for study by NASA’s next space telescope, the James Webb, which will be much more powerful than Hubble, and will be able to study its atmosphere in more detail.
Dr Josh Lothringer, of Johns Hopkins University, was part of Benneke’s discovery team. He told Skymania via Twitter: “Based on the planet’s known mass and radius, we know it has a low bulk density, which tells us it has an envelope of H and He. The only other gas we can detect is H2O, but JWST should tell us about CO2, CO, CH4, NH3, and maybe more!
“And when we say its atmosphere is too thick for life, we mean that it likely doesn’t have an observable surface and any surface pressure would be tens of thousands (or more) times the pressure at Earth’s sea level.”
One potential fly in the ointment is that the planet’s atmosphere is much denser than Earth’s, which probably rules out life as we know it from existing on the surface.
Other astronomers have cautioned that K2-18b is unlikely to be a rocky world, and is probably more like a mini-Neptune than a super-Earth.
Red dwarf stars are also prone to emitting violent flares which could bombard the planet with dangerous radiation.
A second study has also just been published using the same data, by scientists at University College London, confirming the discovery of water vapour in planet K2-18b’s atmosphere.
The paper is titled Water Vapor on the Habitable-Zone Exoplanet K2-18b.
★ Keep up with space news and observing tips. Click here to sign up for alerts to our latest reports. No spam ever - we promise! | 0.841335 | 3.798696 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 October 16
Explanation: Edge-on spiral galaxy NGC 3079 is a mere 50 million light-years away toward the constellation Ursa Major. Shown in this stunning false-color Hubble Space Telescope image, the galaxy's disk - composed of spectacular star clusters in winding spiral arms and dramatic dark lanes of dust - spans some 70,000 light-years. Still, NGC 3079's most eye-catching features are the pillars of gas which tower above a swirling cosmic cauldron of activity at the galaxy's center. Seen in the close-up inset at lower right, the pillars rise to a height of about 2,000 light-years and seem to lie on the surface of an immense bubble rising from the galactic core. Measurements indicate that the gaseous pillars are streaming away from the core at 6 million kilometers per hour. What makes this galaxy's cauldron bubble? Astronomers are exploring the possibility that the superbubble is formed by winds from massive stars. If so, these massive stars were likely born all at once as the galactic center underwent a sudden burst of star formation.
Authors & editors:
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U. | 0.859204 | 3.189687 |
First Light Images from Ultraviolet Imaging Telescope (UVIT) payload onboard AstroSat in Orbit
Ultraviolet Imaging Telescope (UVIT) is the long wavelength eye of the multi-wavelength satellite AstroSat, which carries telescopes giving a spectral coverage from hard X-rays to ultraviolet. The satellite was launched on September 28, 2015. Soon after the launch testing of the X-ray telescopes followed. The subsystems of UVIT, e.g. the detectors, were also checked with the doors closed to isolate the optics from degassing of the S/C. The doors of UVIT opened on November 30 and it was pointed to a relatively bright field at high declination and images were taken. This note describes the impressions from these images regarding performance of the payload.
The Performance Parameters of UVIT
UVIT is configured as two Cassegrain-telescopes each of ~ 375 mm aperture. One of the telescope images in 130-180 nm (FUV) and the other images in 200-300 nm (NUV) and 320-550 nm (VIS). A suit of filters allow further selection of a narrower wavelength band for all the three detectors. The field is ~ 28’ in diameter and the most important specifications for imaging are: a) spatial resolution (FWHM) of the ultraviolet images <1.8”, b) sensitivity in 130-180 nm ~ AB mag 20 in 200 s of exposure.
For the first light observations an open cluster of stars in our Galaxy, NGC 188, was chosen. This selection was based on the need to have the first pointing in a direction well away from the equatorial plane to keep the operations of pointing simple, and to have a source which has a variety of stars but not a very high density of stars. This open cluster (a group of stars which are gravitationally bound) is many billion years old and contains ~ 1500 stars. It is located at a distance of ~ 6000 light years in the constellation Cepheus. The cluster has several bright stars which are easily recognisable and are suitable for a first light exposure. Though this source is not a primary standard, it has been studied in details by the past missions so that a good idea of the performance of UVIT can be obtained from these images. Imaging of weak sources, with the proposed resolution of 1.8”, requires corrections for the small drift of the S/C (<0.5”/s) by images obtained with the visible detector. Therefore, in order to keep the analysis simple, it was important to have bright sources so that sensible images could be obtained in a few seconds in the ultraviolet and used for self-correction of the drift.
Preliminary Impressions on the Performance
The images were taken for several minutes with all the three detectors; the UV detectors worked in photon-counting mode to detect each individual photon, while the visible detectors worked in integration mode (like a typical CCD-camera). As the pointing has some drift, the images are taken in short (<~ 1s) exposures and are added together after correcting for the drift. This procedure is easily implemented for this field as bright stars (mag < 15) are available in the field. The final images are presented in the figure below.
Figure: Final images from the FUV (top), NUV (middle), and VIS (bottom) detectors are shown. Please note that axes in the three images are not aligned but the angular coverage is nearly identical. While the UV images have been processed to correct for the drift, the VIS image has not been processed for this.
Detailed view of the bottom-most star in the FUV image is shown below. This is a very bright star and the image suffers from effects of saturation in the detector. The central peak is immediately surrounded by a moat (which is almost devoid of any photons) and an outer ring which is outer part of the wings in PSF: this structure can be explained by the effects of saturation when the average photon rate exceeds one per exposure.
Distribution along X-axis in the Central peak of the image is shown below. Each division on the X-axis is ~ 1.6” wide, and scale on the Y-axis shows brightness on a linear scale.
The recorded counts of the photons in the FUV detector show that sensitivity of the FUV channel is as per the expectation.
This analysis of the first light images suggests that the most important performance-parameters of UVIT (PSF and FUV-sensitivity) meet the expectations. More observations for the calibrations and more rigorous analysis of the data would follow for full characterisation of the payload. We look forward to flood of excellent results on ultraviolet astronomy of stars, clusters, galaxies etc.
UVIT project is a collaborative effort of IIA (Bengaluru), IUCAA (Pune), TIFR (Mumbai), and ISRO from India, and CSA of Canada. | 0.849618 | 3.901402 |
NASA’s Dawn spacecraft has returned the first close-up image after beginning its orbit around the giant asteroid Vesta. On Friday, July 15, Dawn became the first probe to enter orbit around an object in the main asteroid belt between Mars and Jupiter.
The image taken for navigation purposes shows Vesta in greater detail than ever before. When Vesta captured Dawn into its orbit, there were approximately 16,000 kilometers between the spacecraft and asteroid. Engineers estimate the orbit capture took place at 10 p.m. PDT Friday, July 15.
Vesta is 530 kilometers in diameter and the second most massive object in the asteroid belt. Ground- and space-based telescopes have obtained images of Vesta for about two centuries, but they have not been able to see much detail on its surface.
“We are beginning the study of arguably the oldest extant primordial surface in the solar system,” said Dawn principal investigator Christopher Russell from the University of California, Los Angeles. “This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta’s history, as well as logging the onslaught that Vesta has suffered in the intervening eons…”
Although orbit capture is complete, the approach phase will continue for about three weeks. During approach, the Dawn team will continue a search for possible moons around the asteroid; obtain more images for navigation; observe Vesta’s physical properties; and obtain calibration data…
Rock on, folks! Keep us ordinary folks up with what we need to keep our space curiosity bump happy. | 0.833904 | 3.1416 |
In the field of science, it is a common knowledge that nothing can ever surpass the speed of light, as what Albert Einstein theory of special relativity suggests. However, only small particles can get near the speed of light.
On May 29, 1919, after confirming Einstein’s work, NASA offered ways in accelerating particles in an amazing speed including electromagnetic field, magnetic explosion, and wave-particle interactions. These fundamental ways can be observed in the Sun. It’s a kind of real laboratory that allows scientists to even watch how nuclear reactions occur. Electromagnetic and magnetic fields have the ability to accelerate particles near the speed of light by electric charges. Examples, where this process can be done, are the particle accelerator at the Department of Energy Fermi National Accelerator Laboratory and Large Hadun Collides at the European Organization for Nuclear Research. The accelerators are able to pulse electromagnetic fields. Also, the particles are often crashed to find out what kind of energy they release.
Above the Sun interface is a tangle of magnetic fields. The magnetic field can send plums of solar material off the surface when it intersects and snaps. This kind of interaction also gives the particles its charge, according to Space.
“When tension between the crossed line becomes too great, the lines explosively snap and realign in a process known as “magnetic reconnection”,” explained NASA officials.
“The rapid change in a region’s magnetic field creates electric fields, which causes all the attendant charged particles to be flung away at high speeds,” they explained. The magnetic reconnection also happens to planets such as Jupiter and Saturn. The earth’s magnetic field can be measured using NASA’s Magnetospheric Multiscale Mission with the aid of four spacecrafts. Their results indicate that the magnetic field will help in understanding how particles in the universe accelerate. For instance, a magnetic connection can be observed with the solar wind specifically the constant stream of charged particles emitted by the Sun into the solar system.
Aside from the magnetic reconnection, other factors which are also capable of accelerating particles near the speed of light is the wave-particle interactions. The wave-particle interaction phenomena are driven when electromagnetic waves collide. “When electromagnetic waves collide, their fields can become compressed. Charged particles bouncing back and forth between the waves can gain energy similar to a ball bouncing between two merging walls,” stated NASA’s officials.
Another factor which can create an environment for a wave-particle interaction is the explosion of stars like supernovas. According to scientists, when a star explodes, it creates a blast wave shell of hot, dense compressed gas that can zoom away at a great speed from the stellar core. The process ejects high energy cosmic rays which are composed of particles at velocities close to the speed of light. | 0.8129 | 3.864068 |
An image of the heavily-cratered far side of the Moon.
The Moon's Geological History
Scientists have studied the ages of rocks in regions with craters and
determined when in the Moon's past the craters were forming most
quickly. By studying the light-colored regions, called highlands
, they found that from about 4.6 to 3.8
billion years ago rocky debris rained down
on the surface of the young
Moon, forming craters very quickly. Then the rocky rain subsided, and
fewer craters have formed since then.
Rock samples from very large craters (called basins) showed that about
3.8 to 3.1 billion years ago several huge, asteroid-like objects
struck the Moon, just as the rocky rain was ending. This was shortly
followed by lava flows which filled in the basins and formed the dark
maria. This explains why there are so few
craters on the maria, but dense, overlapping craters in the highlands.
No lava flows occurred on the highlands to erase the original blanket
of craters from the time when the Moon's surface was showered with the
debris of the early solar system.
The far side of the Moon has only one small maria. So lunar
geologists believe that the far side is very representative of how the
Moon looked 4 billion years ago.
You might also be interested in:
This picture of the Earth surface was taken from high above the planet in the International Space Station. In this view from above, we can see that there are lots of different things that cover the Earth....more
Like the other creatures of the desert, birds come up with interesting ways to survive in the harsh climate. The sandgrouse has special feathers that soak up water. It can then carry the water to its...more
Deserts are full of interesting questions. How can anything survive in a place with hardly any water? Why is it so dry to begin with? You can find at least one desert on every continent except Europe....more
You can find insects almost anywhere in the world. So it should be of no surprise that there are plenty of insects in the desert. One of the most common and destructive pests is the locust. A locust is...more
There are several species of mammals in the desert. They range in size from a few inches to several feet in length. Like other desert wildlife, mammals have to find ways to stay cool and drink plenty...more
Biomes are large regions of the world with similar plants, animals, and other living things that are adapted to the climate and other conditions. Explore the links below to learn more about different biomes....more
The temperate forest biome is found in regions where winters are cold and summers are warm. Regions with this climate are common in the mid-latitudes, far from both the equator and the poles. Tropical...more | 0.829984 | 3.372944 |
Posts Tagged ‘plasma’
This video is ten minutes of coolness.
This cool time-lapse video shows the Sun (in ultra-high definition 3840×2160 – 4k on YouTube) during the entire year, 2015. The video captures the Sun in the 171-angstrom wavelength of extreme ultraviolet light. Our naked, unaided eyes cannot see this, but this movie uses false-colorization (yellow/gold) so that we can watch in high definition.
The movie covers a time period of January 2, 2015 to January 28, 2016 at a cadence of one frame every hour, or 24 frames per day. This timelapse is repeated with narration by solar scientist Nicholeen Viall and contains close-ups and annotations. The 171-angstrom light highlights material around 600,000 Kelvin and shows features in the upper transition region and quiet corona of the sun.
The first half tells you a bit about the video and the Sun, and you can see the entire year 2015 rotate by. The second half is narrated by a NASA scientist. It is worth watching all ten minutes. And, then, sharing!
The sun is always changing and NASA’s Solar Dynamics Observatory is always watching.
Launched on Feb. 11, 2010, SDO keeps a 24-hour eye on the entire disk of the sun, with a prime view of the graceful dance of solar material coursing through the sun’s atmosphere, the corona. SDO’s sixth year in orbit was no exception. This video shows that entire sixth year–from Jan. 1, 2015 to Jan. 28, 2016 as one time-lapse sequence. Each frame represents 1 hour.
SDO’s Atmospheric Imaging Assembly (AIA) captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 Kelvin (about 1 million degrees F.) In this wavelength it is easy to see the sun’s 25-day rotation.
During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits Earth at 6,876 mph and the Earth orbits the sun at 67,062 miles per hour.
Why This is Important
Scientists study these images to better understand the complex electromagnetic system causing the constant movement on the sun, which can ultimately have an effect closer to Earth, too: Flares and another type of solar explosion called coronal mass ejections can sometimes disrupt technology in space. Moreover, studying our closest star is one way of learning about other stars in the galaxy. NASA’s Goddard Space Flight Center in Greenbelt, Maryland. built, operates, and manages the SDO spacecraft for NASA’s Science Mission Directorate in Washington, D.C.
For us radio enthusiasts, the study of the Sun helps us understand the dynamics of radio signal propagation. And, that aids us in communicating more effectively and skill.
Thanks for sharing, voting, and watching. More information and live Sun content can be accessed 24/7 at http://SunSpotWatch.com
You can also get the Space Weather and Radio Propagation Self-study Course at http://SunSpotWatch.com/swc
Well, thankfully, this is not happening during this contest weekend: one of the largest sunspot regions during this Sunspot Cycle 24, and one of the biggest in several decades, gave us quite a show, back in October 2014.
Five major X-class (very strong) and a number of moderate and “mild” solar x-ray flares erupted from a single sunspot region – this video covers the time period of October 19-27, 2014, as captured by NASA’s SDO spacecraft. This is from what has been one of the biggest sunspot regions in a number of decades.
Between October 19 and October 27, 2014, a particularly large active region on the Sun dispatched many intense x-ray flares. This region, labeled by NOAA as Active Region (AR) number 12192 (or, simply, NOAA AR 12192, and shortened as AR 2192), is the largest in 24 years (at that point in Solar Cycle 24).
The various video segments track this sunspot region during this period (Oct. 19 – Oct.27, 2014), during which we can see the intense explosions. There are five X-class flares during this time, and NASA’s Solar Dynamics Observatory (SDO), which watches the sun constantly, captured these images of the event.
Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
When referring to these intense solar eruptions, the letter part of the classification, ‘X’, means, ‘X-class’. This denotes the most intense flares, while the number, after the classification letter, provides more information about its strength. For example, an X2 is twice as intense as an X1, an X3 is three times as intense, and so forth.
Solar Images Credit: NASA’s Goddard Space Flight Center & SDO
73 de NW7US
While many are talking about how Solar Cycle 24 is the weakest since the Maunder Minimum (the period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare, as noted by solar observers of the time — see this Wiki entry), there are moments when activity on the Sun strongly increases, providing brief moments of excitement.
Here is a case in point, witnessed by the Solar Dynamics Observatory (SDO; see SDO Mission) on June 7, 2011, when the Sun unleashed a magnitude M2 (a medium-sized) solar flare with a spectacular coronal mass ejection (CME). The large cloud of particles mushroomed up and fell back down looking as if it covered an area almost half the solar surface.
SDO observed the flare’s peak at 1:41 AM ET. SDO recorded these images in extreme ultraviolet light that show a very large eruption of cool gas. It is somewhat unique because at many places in the eruption there seems to be even cooler material — at temperatures less than 80,000 K.
This video uses the full-resolution 4096 x 4096 pixel images at a one minute time cadence to provide the highest quality, finest detail version possible. The color is artificial, as the actual images are capturing Extreme Ultraviolet light.
It is interesting to compare the event in different wavelengths because they each see different temperatures of plasma.
Credit: NASA SDO / Goddard Space Flight Center
Video: http://g.nw7us.us/1aOjmgA – Massive Solar Eruption Close-up (2011-06-07 – NASA SDO) | 0.813287 | 3.449541 |
<!--intro-->The next time a distant supernova glitters in the night sky, scientists may be able to solve a mystery about subatomic particles here on Earth. An Ohio State University astrophysicist and his colleagues have devised a way to use the speed of material streaming outward from a supernova to measure the mass of an elusive subatomic particle known as the neutrino.<!--/intro--> Knowing the mass of this particle may help scientists better understand nuclear reactions inside stars, as well as the so-called missing dark matter of the universe, said Richard Boyd, professor of physics and astronomy at Ohio State. Scientists currently believe that three types of neutrinos exist, each with a different mass some ten thousand times less than the mass of an electron, Boyd explained. If so, then heavier neutrinos ejected from a supernova will take longer to reach Earth than lighter neutrinos, Boyd and his coauthors wrote in a recent issue of Physical Review Letters. Boyd's collaborators include John Beacom, formerly a postdoctoral researcher at the California Institute of Technology and now a research fellow at Fermi National Accelerator Laboratory; and Anthony Mezzacappa, head of the Supernova Theory Group at Oak Ridge National Laboratory. Boyd described neutrinos as the key to scientists' understanding of the nuclear reactions that take place in stars. According to current theories, millions of neutrinos should be radiating out of our sun, or other stars, every second. "If we don't know the mass of neutrinos, then we can't use that information to test our theories," Boyd said. "These extremely small masses are hard to measure here on Earth, but if we could measure the differences in flight time of neutrinos from a supernova, we could improve our measurements a million times over." Neutrinos are the most penetrating subatomic particles known, Boyd said. They pass easily through stars, the Earth -- and very often through solid lead. Scientists have built giant underground water tanks to catch neutrinos that pass through. While many neutrino-induced events have been observed, no one has succeeded in measuring the masses of neutrinos, despite decades of effort. At the same time, scientists have been working to explain certain gravitational effects that indicate much of the mass of the universe may be made of unseen, or "dark," matter. If neutrinos exist in the numbers scientists expect, even with a tiny mass, then they make an ideal candidate for dark matter, because they are both abundant and nearly invisible. The researchers' new technique for measuring neutrino mass hinges on the idea that about half of the supernovas that occur in the future -- at least, the ones we can observe from Earth -- will spawn black holes. Only a small portion of stars end their lives in supernovas -- cataclysmic explosions so bright that the star may temporarily outshine its home galaxy. While only a handful of supernovas have been recorded in the Milky Way Galaxy since the early 17th century, all have occurred close to Earth. This suggests that most galactic supernovas are hidden from astronomers' view. But they would not be at all hidden from the supernova neutrino detectors, Boyd said. Boyd explained that as an exploding star collapsed to form a black hole, the star could release 99 percent of its final energy in the form of neutrinos. The very last neutrinos released would all have to leave the star at the same time -- just before the black hole formed. Like the crack of a starting pistol before a race, the instant when a black hole forms could give researchers a definite starting point for timing a neutrino's journey from a supernova to Earth. As the neutrinos raced to Earth, heavier neutrinos should fall behind lighter neutrinos, if only by a second or two in tens of thousands of years of travel, Boyd said. "It's a very small time shift, but one we can measure," he added. "And it would allow us the most precise way we've ever had of detecting the masses of neutrinos." Boyd estimates that Earth will witness at least a few supernovas in the next hundred years. Ohio State is one of a team of institutions collaborating on the design of a new detector, the Observatory for Multiflavor Neutrinos from Supernovae (OMNIS). The word "multiflavor" refers to scientists' dubbing of the three different types of neutrinos as different "flavors" of the particle. If OMNIS secures the funding it plans to request from the National Science Foundation (NSF) and the Department of Energy, the member institutions will construct a lead and iron detector in a salt mine in New Mexico. Today's detectors can only detect one type of neutrino, but the OMNIS detector will be able to detect the other two, Boyd said. Scientists expect all three types of neutrinos to be emitted from a supernova. The challenge is to determine which type has been detected, Boyd said. OMNIS will be able to detect the two types other detectors would see only very faintly. Boyd's part of the collaboration was funded by the NSF. Mezzacappa received support from Oak Ridge National Laboratory, managed by the non-profit company UT-Battelle, LLC, for the U.S. Department of Energy. Beacom's work was funded by the California Institute of Technology. | 0.825403 | 4.131368 |
Astronomers have discovered a black hole in the Milky Way so huge that it challenges existing models of how stars evolve, researchers said Thursday.
LB-1 is 15,000 light years from Earth and has a mass 70 times greater than the Sun, according to the journal Nature.
The Milky Way is estimated to contain 100 million stellar black holes but LB-1 is twice as massive as anything scientists thought possible, said Liu Jifeng, a National Astronomical Observatory of China professor who led the research.
"Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution," he added.
Scientists generally believe that there are two types of black holes.
The more common stellar black holes -- up to 20 times more massive than the Sun -- form when the centre of a very big star collapses in on itself.Supermassive black holes are at least a million times bigger than the Sun and their origins are uncertain.
But researchers believed that typical stars in the Milky Way shed most of their gas through stellar winds, preventing the emergence of a black hole the size of LB-1, Liu said.
"Now theorists will have to take up the challenge of explaining its formation," he said in a statement.
Astronomers are still only beginning to grasp "the abundance of black holes and the mechanisms by which they form," David Reitze, a physicist at the California Institute of Technology (Caltech) who was not involved in the discovery, told AFP.
The Laser Interferometer Gravitational-Wave Observatory at Caltech, overseen by Reitze, had previously detected ripples in spacetime that suggested the possibility of black holes in distant galaxies that were much bigger than what was thought possible.
Stellar black holes are usually formed in the aftermath of supernova explosions, a phenomenon that occurs when extremely large stars burn out at the end of their lives.
LB-1's large mass falls into a range "known as the 'pair instability gap' where supernovae should not have produced it", Reitze said.
"That means that this is a new kind a black hole, formed by another physical mechanism!"
LB-1 was discovered by an international team of scientists using China's sophisticated LAMOST telescope.
Additional images from two of the world's largest optical telescopes -- Spain's Gran Telescopio Canarias and the Keck I telescope in the United States -- confirmed the size of LB-1, which the National Astronomical Observatory of China said was "nothing short of fantastic".
Scientists have tended to find black holes by detecting the X-rays they emit.
But this method has limited usefulness because only a small number of black hole systems where the companion star orbits very close to the black hole would emit detectable X-rays, Liu said at a press conference.
Instead, the team that discovered LB-1 tracked the movements of "huge numbers of stars over a long period of time", before identifying LB-1 based on the motion of its companion star, Liu said.
This method has been used for decades without much success due to the limitations of the available equipment, Liu added.
But LAMOST, constructed between 2001 and 2008 in north China's Hebei province, allows researchers to detect up to 4,000 stars simultaneously with each exposure, making it one of the world's most powerful ground-based telescopes.
Liu told AFP the method used to discover LB-1 could help scientists identify many more black holes in the future.
Out of the 100 million black holes believed to exist in our galaxy, Liu said, only 4,000 "can give you X-rays that can be detected by us".
Beijing, China | AFP | 0.871697 | 3.707176 |
If you were living in an area affected by the polar night this might not seem like a big deal. If you were situated in a slightly more temperate region where one would expect to see something besides pitch-black, your spider-sense might start tingling as you started to realize that something just wasn’t right.
But what if the above scenario you unwittingly found yourself in was caused by the Sun (that fiery 4.6 billion-year-old yellow dwarf star that could bake 960,00 Earths inside its 15 million degree Celsius core) ceasing to exist?
First, the good news: you’d never need to buy sunscreen again.
The Sun is more than just a pretty face
But here’s the problem, and it’s a very obvious one: our planet needs the sun to survive. Period. It’s not like the Sun only acts like an older sibling who always has your back in the schoolyard when somebody’s looking to snatch your lunch money; heaven forbid that sibling meets an unfortunate demise, but you can still fight the good fight in their name for decades despite their absence. If the Sun goes away the first thing you best do is take that lunch money you’re packing and start looking for a Han Solo-esque Hoth parka and a tauntaun, because things are going to get cold. Fast.
The Sun’s mass also keeps planets in orbit, but if that mass were to suddenly disappear the universe would become like a giant pool table with no bumpers-everything would just fly off in a straight line until it collides with something. Earth could become the proverbial ‘eight ball in the corner pocket’ of the Universe as it careens along at the blistering pace of 67,000 miles per hour for potentially billions of years.
It would take the last ray of sunlight to hit the Earth approximately 8 and-a-half minutes after the Sun officially called it a night, and from that exact moment we could all start saying goodbye to outdoor crops and plant life that we rely on for food since photosynthesis would no longer be occurring.
Is it chilly in here, or is it just me?
Theories surmise global surface temperatures would drop to 0°F within a week of the Sun disappearing, which may seem quick but consider this: the eruption of only one volcano in 1883 (Krakatoa) lowered average global temperatures as much as 2.2°F (1.2°C) for almost five years. Krakatoa was an impressive display, but it doesn’t hold a candle to the Sun.
It’s also safe to assume humans around the world would be hitting the panic button with no sun or moon in the sky (the Moon is only visible because of the sun’s rays reflecting off of it) and the forward-thinking advocates of solar energy might begin to regret their decision to go completely off-grid. Human life on Earth would carry on, but it becomes a question of for how long and what you actually consider ‘living’.
Initially most of us would have electricity, there would be flushing toilets and we’d still have access to our favorite online streaming services. But as we moved on from that first 24 hours of absolute darkness and the days began to pass into weeks temperatures would continue to drop; as low as -100°F (-73°C) within the first year. And even though Earth has a molten core that essentially acts like a nuclear reactor it still wouldn’t be enough to fight off the planet-wide freeze.
It’s not like Earth hasn’t seen extreme cold weather conditions before (the lowest recorded temperature is -128°F or -89°C recorded in 1985 in Antarctica), but that was one region of the planet and it wasn’t a constant, year-round reading. Antarctica residents are also used to the cold and ready for it when it comes. People in warmer weather climates? Not so much.
Damn you, science!
Our Achilles’ heel in all of this is being a heterotroph-a creature that eats other organisms in order to survive. The food chain would crumble from the soil up as the plants die off first (thanks to the one-two punch of bitter cold and no photosynthesis occurring), ending things for the vegetable lovers. Most of the animals we eat survive on plant life, so as the greenery disappears the meat eaters won’t be far behind.
So what would survive on an Earth with no sun? Look to the oceans for the answer. Organisms that live near the bottom of the ocean floor would be close to geothermal vents that emit heat from the Earth’s core, allowing them to carry on with nary a care in the world as it literally freezes above them. The surface of the planet’s oceans would be frozen, but it could take billions of years of extreme temperatures for the freeze to reach depths found in areas like the Mariana Trench’s 36,070 feet (10,994 meters).
Now, if humankind managed to organize itself in such a manner that we were able to launch submarines into the deepest depths of the ocean, we might have a chance. There’d be no windows to look out of, but if we’re lucky we might still be able to stream something decent to watch on television while we waited things out. | 0.803791 | 3.259726 |
When you dive into it, scientific research isn’t as much a quest for the right answer as it is for one theory that can explain existing observations. As instruments and techniques improve in sensitivity and accuracy, new observations challenge our pre-existing models and allow us to find better, more accurate explanations.
The Hubble constant – a number that denotes how fast the universe is expanding – is going through a similar phase of disagreement. Scientists who used different ways to measure the constant have calculated different values, which is not supposed to happen and suggests we’re missing something. Indeed, many wonder if this might be occasion to revise our current understanding of the early universe, dark matter, particle physics, even the shape of the universe.
In 1927, an American astronomer named Vesto Slipher observed different frequencies of light, a.k.a. spectra, from 46 galaxies. He found that the spectra were all shifted towards the red end of the electromagnetic spectrum. The faster an object recedes from an observer, the more its spectrum appears red-shifted. Ergo, the galaxies were all moving away from Earth.
In 1929, Edwin Hubble calculated how fast each galaxy was moving away at a given distance. What he found was in line with the deduction of one of his peers in Belgium, Georges Lemaître: that the farther away a galaxy was, the faster it was moving away. This can be represented in a simple formula: v = Ho d. Ho is called the Hubble constant; the larger it was, the faster the universe would be expanding. However, the exact value of Ho has been hard to pin down since.
It is relatively easy to measure how fast the galaxies are receding. The problem lies with measuring the distances to galaxies. Objects that are farther away appear dimmer, so if we know the intrinsic brightness of an object, we can compare that with the observed brightness and figure out how far away it is.
When Hubble calculated his eponymous constant, he obtained a value of 500 km per second per megaparsec (km/s/Mpc) – that is, objects 1 megaparsec away were moving away at 500 km/s.
In his time, astronomers used a type of stars called Cepheid variables, discovered by Henrietta Swan Leavitt in 1912, as distance indicators. The brightness of these stars varied in periodic fashion, so astronomers could deduce their current brightness simply by measuring the time elapsed between two brightness peaks.
Later, another class of objects presented itself as distance indicators. These were the Type Ia supernovae – a kind of end-of-life star explosion that had the same brightness irrespective of which star had died this way. When astronomers used these objects to calculate Ho, they found it to be only 50-90 km/s/Mpc. Initially, the instruments used to make these measurements weren’t very accurate, so people hoped the discrepancy would vanish with more sensitive instruments.
In 1998, other astronomers made a major discovery: that the universe’s expansion was accelerating. This was attributed to dark energy, an intrinsic energy of the vacuum of space, about which we know very little, that was pushing the universe apart. In 2015, scientists used data from the Planck satellite, which studied the radiation left over from the Big Bang, together with a popular theory that accounts for the effects of dark energy on the universe to calculate Ho to be 67.8 ± 0.9 km/s/Mpc.
This caused confusion: two precise techniques had two different values of a number that had to be the same throughout the universe.
In April 2016, an American astronomer named Adam Riess, one of the three scientists who had made the accelerating expansion discovery, and his team set out to try and resolve the issue. They studied Cepheid variables and Type Ia supernovae in nearby galaxies with great precision to calculate the value of Ho in the local universe, and then compare that to data from the Planck satellite.
Riess & co. obtained 73.85 1.96 km/s/Mpc. In 2018, the Planck collaboration improved their calculations to establish Ho as 67.4 ± 0.5 km/s/Mpc. In March 2019, Riess’s team further constrained the value to 74.3 ± 1.42 km/s/Mpc. In July 2019, yet another team studied gravitational lensing by quasars to obtain a value of 73.3 + 1.7 – 1.8 km/s/Mpc.
It is as if we are not able to agree on how fast the universe is expanding.
Wendy Freedman, an astronomer at the University of Chicago, is known for her work on calculating the value of the Hubble constant. She used data from the July 2019 paper in a new attempt to stem the proliferation of Ho values. Ironically, she and her team ended up with a new number: her paper, due to appear in the Astrophysical Journal, presents Ho to be 69.8 0.8 km/s/Mpc.
These multiple distinct values are all very precise, and prompt us to consider modifying our current theories in cosmology and particle physics, among others, to explain them and offer potential sources of difference.
A robust scientific theory is one that successfully explains current observations and measurements as well as makes testable predictions. Scientific research is ultimately a process involving numerous checkpoints: each new discovery that disagrees with the current framework of our understanding of the world prompts us to modify it. So while the different values of the Hubble constant are frustrating, it is also an exciting time to be a cosmologist.
Sakhee Bhure graduated with a BS in astronomy and astrophysics from the Florida Institute of Technology. She is interested in writing about science. | 0.833278 | 4.136325 |
Highlight: Spin-orbit angle measurements for six southern transiting planets [...] (vol. 524)
- Published on 17 November 2010
Spin-orbit angle measurements for six southern transiting planets. New insights into the dynamical origins of hot Jupiters
When an exoplanet transits its parent star, one should be able to determine the angle between the stellar spin axis and the axis of the planetary orbital plane by careful analysis of the radial velocity signal: this is called the Rossiter-Mac Laughlin effect. In our Solar System, this angle is at most 7° for all 8 planets. In the first transiting systems for which this measurement had been possible, the angles were found to be small, which is consistent with the situation in our Solar System. This picture slowly changed with the discovery of several highly inclined and even retrograde systems. Triaud et al. present six new observations of 3 systems that are highly inclined and three that are compatible with 0°. But accounting for the degeneracy in the inclination of the stellar spin axis determination, they show that between 45 and 85% of all hot Jupiters have inclinations of 30° or more. This implies that standard migration alone cannot explain the observations. They also show that the observations are explained by a model in which the planets are sent close to their star through a so-called Kozai mechanism (see figure). | 0.887808 | 3.602661 |
Liquid water has flowed on the surface of Mars within the past five years, suggest images by the now lost Mars Global Surveyor (MGS). The results appear to boost the chances that Mars could harbour life.
In 1999, MGS spotted gullies carved on the sides of Martian slopes. Thousands of gullies have been imaged since then, most recently by the Mars Reconnaissance Orbiter (MRO) (see Stunning snaps from the best camera ever sent to Mars).
The gullies appear to have formed sometime in the past several hundred thousand years, since impact craters have not accumulated on top of them. But exactly how long ago material flowed through them has not been clear.
Now, new flows have appeared in two of the gullies monitored by MGS, showing that they have been active within the past several years. The research was led by Michael Malin of Malin Space Science Systems in San Diego, California, US. That company operates the Mars Orbiter Camera on MGS, which acquired the images.
One gully on a crater wall that was imaged in 2001 was found to have filled with light-coloured material when it was re-imaged in 2005. A similar new light-coloured deposit appears in a 2004 image of crater gullies previously imaged in 1999.
The researchers suggest the deposits were made by liquid water flowing out from beneath the surface. The researchers estimate that each flow would have involved 5 to 10 swimming pools’ worth of water.
It would have been similar to a flash flood in the desert, says team member Ken Edgett of Malin Space Science Systems. “If you were there and this thing was coming down the slope, you’d probably want to get out of the way,” he says.
Any liquid water exposed to Mars’s atmosphere would quickly freeze, but Malin’s team says even if the exterior of the flow rapidly freezes, water could continue flowing much farther inside this ice shell, developing into a thick mixture of ice and sediment that would eventually freeze completely.
In Mars’s thin atmosphere, ice left on the surface would quickly sublimate, changing from a solid to a gas, and disappear. But water vapour diffusing out from deeper in the mixture of ice and sediment could repeatedly coat the surface with frost, maintaining its light colour long enough for MGS to spot it, the researchers say.
Alternatively, salt deposited from salty water or sediment placed there by water flow may be responsible for the light colour.
MGS team member Phil Christensen of Arizona State University in Tempe, US, who was not involved in this study, says he is convinced that the gullies were formed by the action of liquid water.
“It says something is actively going on today in at least some of these gullies and one intriguing possibility is that water was released,” he told New Scientist.
“I think they make a pretty good case that these aren’t simply dust avalanches or some wind-related process,” he says. He adds that the sublimating carbon dioxide scenario is even less likely, because temperatures in the regions where the gullies are found – between 30° and 60° from the equator – are too high for the gas to get frozen in the first place.
Allan Treiman of the Lunar and Planetary Institute in Houston, Texas, US, agrees that something flowed recently to make the observed changes.
But he is not convinced that water was involved. “There is no direct evidence of water in the images – only that something flowed downhill. My money is on sand and dust, because there’s lots and lots of sand and dust on Mars.”
Streaks on slopes have been observed before and interpreted as the result of dust avalanches. But these appear to be a separate phenomenon from the new light-coloured gully deposits, the researchers say.
Newly formed dust streaks have been observed, but are always dark. The dust streaks are also usually observed in areas where the surface clearly has a thick coating that could be dust, unlike the two craters in question. And dust streaks have never been observed on the same slopes where gullies carve into the surface.
The formation of new gullies has been observed before also, but these were on the sides of sand dunes, and were more clearly related to avalanching sand (see Landslips, impacts and eroding ice revealed on Mars).
If the deposits are the result of liquid water flow, the source of the water is not clear. Malin’s team suggests it comes from underground aquifers, perhaps kept liquid at low temperatures with the help of high salt concentrations.
Christensen says it could result from the removal of dust from a hypothetical layer of snow, which would then melt when exposed to sunlight.
The SHARAD radar on MRO is potentially capable of detecting any underground pockets of water that the flows might have come from, Malin says. “We’re hopeful that as SHARAD flies of over these locations it may be able to detect these subsurface aquifers,” he says.
The new evidence that liquid water may flow on Mars today boosts the chances that life could be present, Christensen says. “I believe that we have found places on Mars where you could take terrestrial life forms that live on snow or in aquifers and put them there and they would survive,” he says.
Malin’s team also reports in the same study the formation on Mars of 20 new craters between 2 and 150 metres across since 1999, confirming the previously estimated rate of crater formation and reinforcing the view that crater-free areas of Mars must truly be young or recently modified.
The discovery may be one of the last from MGS, which went silent shortly before its 10th launch anniversary in early November, and has not been heard from since (see Europe joins hunt for missing Mars probe).
Journal reference: Science (vol 314, p 1573) | 0.820659 | 3.950698 |
Mars (pronounced /- m- rz/) is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance, due to iron oxide prevalent on its surface. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It is the site of Olympus Mons, the highest known mountain in the Solar System, and of Valles Marineris, the largest canyon. Furthermore, in June 2008 three articles published in Nature presented evidence of an enormous impact crater in Mars' northern hemisphere, 10,600 km long by 8,500 km wide, or roughly four times larger than the largest impact crater yet discovered, the South Pole-Aitken basin. In addition to its geographical features, Mars' rotational period and seasonal cycles are likewise similar to those of Earth. Until the first flyby of Mars by Mariner 4 in 1965, many speculated that there might be liquid water on the planet's surface. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, of all the planets in the Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life. Radar data from Mars Express and the Mars Reconnaissance Orbiter have revealed the presence of large quantities of water ice both at the poles (July 2005) and at mid-latitudes (November 2008). The Phoenix Mars Lander directly sampled water ice in shallow martian soil on July 31, 2008 Mars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and the Mars Reconnaissance Orbiter. With the exception of Earth, this is more than any planet in the Solar System. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity) and several inert landers and rovers, both successful and unsuccessful. The Phoenix lander recently completed its mission on the surface. Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred during the past decade. Observations by NASA's Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches - 2.9, a brightness surpassed only by Venus, the Moon, and the Sun, although most of the time Jupiter will appear brighter to the naked eye than Mars. Physical characteristics Mars has approximately half the radius of Earth. It is less dense than Earth, having about 15% of Earth's volume and 11% of the mass. Its surface area is only slightly less than the total area of Earth's dry land. While Mars is larger and more massive than Mercury, Mercury has a higher density. This results in a slightly stronger gravitational force at Mercury's surface. Mars is also roughly intermediate in size, mass, and surface gravity between Earth and Earth's Moon (the Moon is about half the diameter of Mars, whereas Earth is twice; the Earth is about ten times more massive than Mars, and the Moon ten times less massive). The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as hematite, or rust. Geology Volcanic plateaus (red) and impact basins (blue) dominate this topographic map of Mars. Rock strewn surface imaged by Mars Pathfinder Based on orbital observations and the examination of the Martian meteorite collection,
După plată vei primi prin email un cod de download pentru a descărca gratis oricare alt referat de pe site.Vezi detalii. | 0.857117 | 3.92023 |
Photographing the Full Moon with a Digital Camera
About once a month, it's Full Moon, and our nearest celestial neighbour rises at sunset and remains visible throughout the night, setting at daybreak the next morning.
Popular wisdom has it that crazy people ("lunatics") go even crazier at the time of Full Moon, and werewolves skulk in the shadows, pouncing on and devouring unsuspecting astronomers as they peer through their telescopes. In the real world, however, reliable reports of such events are rare.
The most obvious change the Moon undergoes during the 28 day lunar month is the sequence of phases, from a slender crescent to a half Moon, swelling to the bright full phase, and then waning to a crescent again.
A more subtle change, that requires a bit more effort to notice, is the change in the angular size of the Moon. Of course, the Moon's actual size doesn't change: it's about a 10,900 km round-trip if you took a walk around its equator. The angular size (how large a patch of sky it covers) as seen from Earth, does change, because the Moon isn't always at the same distance from us. By photographing the Full Moon at different times during the year you can see for yourself how its angular size changes.
The diameter of the Full Moon varies from around 29.5 arcmin to 33.5 arcmin. The diameter thus increases by about 13% from minimum to maximum, but in area, this is a 29% increase!
Check out Carol Botha's article "Moon Photography Tips" for more lunar digital photography lessons.
DISCLAIMER: There are many, many makes and models of digital cameras on the market, and their capabilities differ markedly. Some cameras work only in fully automatic mode, and do not allow the user to change settings. This article, however, focuses on those cameras that do allow changes to be made to exposure time and aperture. Usually, such cameras will have a dial (as in the photo below) or an option that can be selected from a menu.
Nevertheless, the basics of photography remain the same irrespective of a particular camera's features. Play with whatever settings your camera offers, and don't be disappointed if the images aren't as good as what the guys at SALT or the Hubble are taking. Have fun!
Modern digital cameras are excellent for photographing the Moon. You don't need a telescope, either – in fact all you need is a tripod. The tripod doesn't need to be an elaborate affair – as the accompanying image shows, they can be quite humble; this one cost me R40 at my local camera shop (match not included).
In a pinch, you could also try using a detachable tripod head (or scavange one from a cheap tripod) and fix it to something sturdy, like a fence post. Keep in mind, though, that a good sturdy tripod (something you could use to bash down a door, say) is nevertheless important – the cute mini-tripod should be used for emergency photography only.
In a traditional camera, the detector is film, a strip of plastic coated with light-sensitive chemicals. In a digital camera, the detector is a CCD, a light-sensitive electronics component (a distant cousin of those gadgets that automatically turn on an outdoor light when it gets dark). A CCD consists of a grid of tiny sensors, like the compound eye of an insect, each capable of sensing a small portion (a pixel, or "picture element") of the image. Each pixel converts light into electrons; the electrons are counted ("digitized") and the values stored in a data file. The data file can then be transferred to a computer for display.
When taking a photograph (film or digital), there are basically only two variables you can control: how much light the lens lets through, and for how long it falls on the detector.
After discussing these basic ideas, I will briefly summarize a few other concepts and, with a dose of practical tips, you'll be on your way.
The first variable, how much light you allow to pass through the lens to the CCD, is the aperture setting (or lens aperture, F-number, focal ratio, Av). It is numerically expressed as an f-ratio, with a value from, say, 1.6 up to, say, 22. The bigger the number, the more light is blocked. A lens set to f/16 gives an image four times dimmer than a lens set to f/8. For astrophotography, because things are generally faint, it is best to "open up" the lens, i.e. use a smaller f/number. The Moon, on the other hand, is bright enough so you can safely try a range of f/stops.
The second variable is the exposure time (shutter speed, Tv), which is the duration, in seconds, that the CCD is exposed. Longer exposures means more light gets through, so fainter objects are recorded. Exposure times range from many seconds, to thousands of a second. For astrophotos, long exposures are typical, because most astronomical objects are faint.
The trick in any photo is to know how to match these two: size of opening and exposure time. Too small an aperture, or too short an exposure time, may let through too little light. Too much light, and the image is over-exposed.
Fortunately, cameras have a built-in light meter which balances the relationship between aperture and exposure. However, light meters can be unreliable when you're taking astrophotos – they are mostly designed for "normal" daylight photography.
The joy of a digital camera, though, is that it is easy to get it right – just take a photo, look at the result, and decide if it needs more or less light. Look at the following three images:
All were taken with the lens set to f/8. The first image, exposed for a thirtieth of a second, is obviously overexposed.
The last image was only exposed for 1/250th of a second, 8 times shorter than the first. It looks a bit dull, the whites appear gray, so is a bit underexposed. The middle one looks a bit better. It would be a simple matter to have taken another image, at 1/60th of a second, to see if it was an improvement. This technique of taking multiple shots with different exposures is called bracketing, and it can be your best friend!
What is the correct setting? That's up to you to decide. Look at these two images:
The left one shows the sunlight portion of the Moon well, so that you can make out craters and lunar seas. The second image, exposed almost 200 hundred times longer, heavily over-exposes the sunlight portion, but allows detail to be seen in the shadowed portion. The "correct" exposure thus depends on what you want to show. In general, a well-balanced exposure will show white as white, and black as black, with a full range of grays in-between.
Table 1. Exposure guidelines for the Moon (assuming ISO 400 at f/8)
|thin crescent Moon||1/60th|
|bright features on the terminator||1/250th|
|dim features on the terminator||1/125th|
|partial lunar eclipse||half-second|
|total lunar eclipse at maximum||6 to 135 seconds|
The exposure times in Table 1 are for a camera set at f/8 and ISO 400.
For different aperture and/or ISO settings, use the following rules:
Each time you halve the ISO, then double the exposure time, and vice versa: for each doubling of the ISO, halve the exposure time. (Full Moon example: [f/8, ISO 400, 1/1000th] = [f/8, ISO 200, 1/500th] = [f/8, ISO 800, 1/2000th]).
Each time you halve the f/ratio, then divide the exposure time by four; double the f/ratio and you need to expose four times longer. (Full Moon example: [f/8, ISO 400, 1/1000th] = [f/4, ISO 400, 1/4000th] = [f/16, ISO 400, 1/250th]).
When changing both ISO and f/ratio, apply the first rule, then the second. (Full Moon example: [f/8, ISO 400, 1/1000th] = [f/4, ISO 200, 1/2000th]).
The bottom line: bracket your exposures, examining each image after you've taken it to see if things looks good. When in doubt, take another image.
Digicams that don't give you direct control over exposure time, need a slightly different approach. In addition to the usual "Auto" exposure mode (which is fully automatic; you just point and shoot), other modes are usually available, often with creative names, such as "High Sensitivity", "Twilight", "Soft Snap", "Beach", "Fireworks", and so on. Try all the modes your camera offers and note which work. Dr Philip van Heerden, for example, discovered that "High Speed Shutter" mode on his camera worked perfectly (see example images).
Another tactic is to fool the camera's light meter into using a different exposure time than what it thinks is necessary. Hans van der Merwe has had success by shining a bright torch into the camera lens while pressing the shutter release trigger half-way, to prompt the camera to take a light reading. The bright torch-light tricked the camera into choosing an exposure time that worked perfectly for the Moon. Willie Koorts has pointed out that (crazy as it sounds) forcing the camera to use its flash can also do the trick. The flash isn't used to illuminate the Moon – in flash-mode, a camera will almost always fix the exposure time at 1/60th of a second (some models may use 1/125th). To avoid air-borne dust from being picked up by the flash, cover the flash with your hand (and close your eyes!).
With film cameras, you can use film rated at different speeds, or light sensitivity. Numerically this is expressed as an ISO number: ISO 100 is "slow", while ISO 1600 is "fast". The bigger the number, the more light-sensitive the film is.
The same is true for digital cameras. If you can change the ISO setting on your camera, you can select how light-sensitive it will be. If your camera has a fixed ISO setting, then things just got a whole lot simpler!
It seems obvious that one would always want to set your camera at its highest sensitivity. This makes good sense, but there's a hitch. Look at these two images:
Both images were taken with the same aperture setting (f/2.7) and exposure time (15 seconds). The left-hand image, though, was taken with the camera set to ISO 200, while the right-hand one was at ISO 1600.
Although fainter stars can be seen in the right-hand image, there's also a massive amount of background dots, or "noise". Instead of a nice black night sky like in the left-hand image, the high-speed image shows random speckles, almost swamping the stars. This noise is an unwanted side-effect of the high-sensitivity setting.
Different digicams have different ways of dealing with noise; some cameras are good, others are bad, at high ISO settings. High-end digital cameras, for example, often have a useful "noise reduction" setting. Experiment with your camera and choose a speed that works for you. As a rule, if the object is bright, use a slower setting because it will have less noise. There is always noise – you can't always see it, though.
A fundamental thing that a lens has to do, is focus the light. Some cameras have a "fixed-focus" lens, which means you can't change the focus, and that's that. Fixed-focus lenses are common in low-end cameras.
The majority of digicams have an auto-focus setting, in which the camera does the focusing for you. Sometimes you have to try a few times before the camera gets it right. Some cameras struggle to focus in low-light conditions, so it's best to go to "manual focus" mode.
With manual focus selected, you are in charge of focusing the image. For astronomy, this simply means setting the lens to be focused at "infinity". Fiddle with the setting, before taking the image, until the view on the display is sharp. You're set.
All compact digital cameras today have a built-in zoom lens, allowing you to magnify the image, or zoom out for a wider view. The amount of zoom is numerically given as the focal length (usually in millimetres), where a big number means a closer zoom.
Digicams have two kinds of zoom: "optical" and "digital". Using "optical zoom" is like changing eyepieces in your telescope.
Unlike film cameras, digicams also have "digital zoom". If your camera allows you to download a "raw" image, then digital zoom is a gimmick, and you'll achieve the same result by just sitting closer to you computer monitor or pressing the "magnify/zoom" icon in your graphics program.
However, if you can't download "raw" images, then you will get slightly better results using digital zoom (rather than enlarging the image on your computer). The two images below show the magnificent crater Langrenus. The right-hand image was taken with 48x zoom (12x optical plus 4x digital). The left-hand image was taken at 12x optical zoom, and then enlarged in Paint Shop Pro. The blocky appearance is caused by the image compression used by the camera. If the right-hand image is enlarged, it too will be seen to have a blocky appearance. A "raw" setting does not create this artefact.
When photographing the Moon, by all means use as much zoom as you have. Experiment with the "digital zoom" and see how it works for your camera.
This is the big number quoted on the box, the megapixels. An image which is 3,000 pixels wide, and 2,000 pixels high, has 3,000 x 2,000 = 6,000,000 pixels, or 6 Mega pixels. The more the megapixels, the more the detail. And the more hard drive space you need to eventually store all those megapixels. If you can change the image resolution on your camera, choose the highest setting (mega mostpixels).
When you press the shutter release button to take the picture, you may slightly bump or nudge the camera, causing the image to jitter. To avoid this, some cameras use a remote control (on film cameras, called a "cable release"). Fortunately, there is an easy solution if you don't have such a cable. Simply use the camera's self-timer function, which waits for a number of seconds after you press the shutter release button before taking the image. All this atop a tripod, remember.
Sometimes, no matter what you do, despite your best efforts, the image looks bleary. The craters aren't sharp, and the edges of lunar seas are fuzzy. If you've made sure that the camera is focusing properly, the most probable cause is the atmosphere. The two images below, taken a mere fraction of a second apart, shows this.
If the skies are hazy, or there is (unseen) cloud, your images will be correspondingly blurry. Sometimes, particularly when you notice the stars twinkling rapidly, it helps to change your settings so that the exposure time is as brief as possible, hopefully catching a sharp image at the instant the flickering is frozen. Mostly, blurry images mean a blurry atmosphere, and there isn't much you can do about it.
Do keep in mind, though, that the higher above the horizon your target is, the clearer the image will be (because you're looking through less murky atmosphere).
Also consider local factors that could be disturbing your view. Turbulence caused by heating can be minimised if you set up on a grassy patch (a lawn, rugby field, etc), as opposed to a tar road, parking lot or too near a building. And wind, too, can give you the jitters.
Having taken your photos and transferred them to your computer for viewing, sort the good from the bad, and make a note of which settings worked best for you.
When the Full Moon comes around again, use the same settings to image it – in particular, pay attention to the degree of zoom (focal length) you used, because this determines the size of the Full Moon on your image.
Digital cameras afford a luxury unheard of to conventional photographers: you can instantly review the image you've just taken, and if you're not happy, change settings, and try again. The Moon is a patient subject, and will hang around sedately while you change settings, compose the shot, or search for your spare set of batteries in the dark. "Experiment" is the key word; try, and try again – it only costs you a few photons & electrons.
To get cool Full Moon pics with your compact digitical camera:
If you've tried to photograph the Full Moon, I'd love to hear from you. By sharing your experiences, advice and photos, others who are just starting out can learn from you. My contact details are on the "Contact" page.
2007 Jan 31 @ 10:54, via Chris; Jan 31 @ 16:22; Feb 02 @ 21:00 via Willie; Feb 04 @ 02:27, via Hans & Carol; Feb 06 @ 19:12 via Pat; Oct 31 @ 10:32.
2007 October 31: The largest Full Moon for 2007 has come and gone; now you can compare the April and October Full Moon sizes here.
2007 February 05: The February Full Moon has come and gone. Carol Botha (Cape Town), Dr Philip van Heerden (Cape Town) and Lerika Cross (Johannesburg) have kindly sent in their Full Moon images, which are presented, along with my image, in the gallery. Note that the images haven't been manipulated or fiddled with in any way, other than to crop away the surrounding negative space to reduce file size.
2007 Feburary 07: Chris Stewart has provided some comments on Lerika's Full Moon image.
nothing more to see. please move along. | 0.826201 | 3.566089 |
Carbonado Diamond: A Review of Properties and Origin
Carbonado diamond is found only in Brazil and the Central African Republic. These unusual diamond aggregates are strongly bonded and porous, with melt-like glassy patinas unlike any conventional diamond from kimberlites-lamproites, crustal collisional settings, or meteorite impact. Nearly two centuries after carbonado’s discovery, a primary host rock compatible with the origin of conventional diamond at high temperatures and pressures has yet to be identified. Models for its genesis are far-reaching and range from terrestrial subduction to cosmic sources.
Discovered in 1841 in Brazil, carbonado was named by Portuguese diamond prospectors for its resemblance to charcoal (Leonardos, 1937; Dominguez, 1996). Carbonado was found later in the Central African Republic. These two localities, now separated by the Atlantic Ocean and situated on the São Francisco and the Congo cratons, respectively, previously shared a common geological setting for more than a billion years (De Waele et al., 2008) on the supercontinent of Rodinia (figure 1) and its precursor Nuna, also known as Columbia.
Carbonado was prized by the French as a superior polishing material. It was used for drilling during the construction of the Panama Canal and formed part of the U.S. strategic mineral stockpile as recently as 1990. At the height of alluvial mining in Brazil (1850–1870), some 70,000 carats were produced by an estimated 30,000 artisanal miners (Svisero, 1995). A conservative estimate of the recovery from Brazil and the Central African Republic is approximately 2 metric tons (Haggerty, 2014). Four of the five largest diamonds reported from Brazil, ranging in weight from 726 to 3,167 ct, are carbonado (Svisero, 1995). The largest of the five, the Sergio, recovered in 1905, is 61 ct heavier than the largest single-crystal diamond ever reported (the 3,106 ct Cullinan rough).
While earlier investigations of carbonado focused on physical and chemical properties and synthesis, more recent studies have introduced dating techniques, high-resolution microscopy, spectroscopy, and an emphasis on origin (see Haggerty, 2014, for a more comprehensive view). The present study offers a detailed examination of about 800 carbonados from Brazil and the Central African Republic (figure 2), ranging from <1 to 730 ct. These samples showed no significant differences in their texture, superficial appearance, and physical and chemical properties (Haggerty, 2014). This article describes the unusual textural features of carbonado, namely their pores and the presence of glassy diamond as a surface patina, with the aim of assessing the origin of carbonado.
CHARACTERISTICS OF CARBONADO
Carbonado is typically found in five major size categories: >200 ct, 75–95 ct, 25–35 ct, 8–15 ct, and 0.25–1.25 ct (see figure 5 of Haggerty, 2014). Sand-sized particles (<1 mm) also occur, and melon-size objects larger than the Sergio are reported but unconfirmed (M. Ozwaldo, pers. comm., 1996). Carbonados are typically equidimensional (in millimeter to centimeter sizes), although some are elongated (figure 3); they are seldom rounded.
Carbonado is opaque, composed of randomly oriented diamond crystallites that impede light refraction and increase absorption. Color varies from black and putty gray to shades of brown (figure 3), deep purple to pink, rusty red, and the occasional olive green. Pores (figure 4), an unusual glassy patina (figure 5), highly irregular surfaces (figures 6 and 7), and polycrystallinity (figures 8 and 9) distinguish carbonado from conventional diamonds.
Porosity. As the porosity of an object increases, its apparent density decreases, because the voids take up more and more of the volume. In carbonado, the number of exposed microdiamond cutting points increases with porosity. This was a sought-after property that made carbonado more expensive by weight than diamond at the turn of the twentieth century (Haggerty, 2014). Densities as low as 2.8 g/cm3 and as high as 3.45 g/cm3, with most around 3.05 g/cm3 (Trueb and De Wys, 1969; Haggerty, 2014), are in contrast to gem diamond at 3.52 g/cm3. Calculated pore concentrations vary between 5% and 15% in volume. The pores persist into the interior of the carbonado and are either spherical or oblate. Some are inferred to be interconnected (Ketcham and Koeberl, 2013), but the material’s permeability is very low because the pores are free of infiltrating hydrothermal precipitates that abound in surface pores (again, see figure 4). The spherical pores in carbonado are unlike those in other polycrystalline diamond such as framesite, where the open spaces are at adjoining crystal faces and the shapes are irregularly polyhedral. In other polycrystalline diamonds, the open spaces are microns in width and either radial (in non-gem-quality ballas) or parallel (in fibrous cubes).
Patina. In carbonado, patina surfaces are pervasive (figure 5). Pores in contact with surface patinas are reduced in size, and at 50× magnification they can no longer be distinguished. Glass-like in appearance and similar to synthetic carbon glass (de Heer et al., 2005), these veneers may be dimpled or furrowed, with mounds and flow structures (figures 5 and 6). These textures are akin to those seen in melts in volcanic rocks or in slags from metal processing. But in carbonado, the veneers are diamond that appear to have formed directly from the underlying porous substrates, although diamond coating at a later time is also possible. Contact boundaries between pore-present and pore-absent surfaces are poorly defined, except in cases where patina crusts have splintered off where the contact is sharp, as seen in the lower-right images of figure 6 and in figure 7. Secondary pits and microcraters are pervasive and, in many cases, younger than the patina (figure 7). While pores tend to have sharp outlines (figure 4), craters are rounded with bubbly surfaces or rimmed by smooth ridges (again, see figures 6 and 7). The evidence of flow in both types of voids implies differences in origin. Solid melt marbles are typical. Microcraters, free of ornamentation, grade into texturally soft plastic walls (figures 5 and 6). Slickensides, the striated surfaces known to form on rocks that have been forced to slide along a fracture surface at high pressure as in a fault (figure 7), are of interest because these could only have developed on frictional contact with a body whose hardness was equivalent to another diamond. On the other hand, the patina itself may represent frictional melting (e.g., de Heer et al., 2005; Mitchell et al., 2016; Shumilova et al., 2016a,b; Shiell et al., 2016). Standard diamond testers that measure thermal conductivity give a sharp response to glassy diamond surfaces, less so to the ridges and mounds. The pore-rich surfaces are distinctly sluggish and erratic in response, possibly due to crystal discontinuities of microdiamond grain boundaries.
PHYSICAL AND CHEMICAL PROPERTIES
Octahedra, dodecahedra, tetrahexahedra, and fibrous cubes, all typical of conventional diamond (e.g., Orlov, 1977), are not observed in carbonado. Polycrystalline cubes measuring 5 to approximately 20 µm are common. Encased in very fine diamond (<1–5 µm), the matrix is tightly fused with angular interstices and rounded pores (figure 8). Scanning electron microscopy (SEM) images illustrate the distribution of diamond cleavage surfaces, hopper crystals, skeletal crystallites, re-entrant intergrowths, and layers in single crystals in the open-space pores of carbonado (figures 8 and 9). Trueb and De Wys (1969) and Petrovsky et al. (2010) suggest that the closest analogy to carbonado textures is in synthetically compressed nanodiamond aggregates. Because these structures are found in pores, a more reasonable comparison is with vapor deposition of diamond. The preferred crystal habit of these diamonds is cuboidal, either as single solid cubes or as interpenetrating twins on that follow the fluorite twin law (figure 8). The solid cubes are colorless and, although fine grained, appear to be translucent. Diamond cubes and cuboctahedra are routinely synthesized in metallic catalysts at high pressure and temperature (Burns and Davies, 1992) or by chemical vapor deposition (CVD) under high vacuum and at plasma temperatures (Sato and Kamo, 1992).
X-ray diffraction (XRD) data on crushed carbonado grains are similar to conventional diamonds. Hardness is also similar, but there are data indicating that carbonado is slightly harder (Haggerty, 2014). Its toughness and tenacity, stemming from the random orientation of microdiamonds, are clearly superior to monocrystalline gem diamond, to the point that carbonado can only be cut by lasers.
Yet another unusual feature of carbonado is the presence of an exotic array of metals (Fe, Ni, Cr, and Ti), metal alloys (Fe-Ni, Fe-Cr, Ni-Cr, and W-Fe-Cr-V), and very unusual minerals, specifically moissanite (SiC) and osbornite (TiN). These phases occur as primary intergranular inclusions or as crystal-controlled oriented intergrowths. They are only stable at the very low oxidation states (Gorshkov et al., 1996; De et al., 1998; Makeev et al., 2002; Jones et al., 2003) that would occur deep within Earth’s mantle or other reducing environments such as outer space. By contrast, surface pores and fractures are filled by secondary, low-temperature minerals such as quartz and highly oxidized magnetite, goethite, florencite, and goyazite (Trueb and Butterman, 1969), typical of a more oxidized terrestrial surface growth environment.
Relative to mantle-derived diamonds, carbonado is isotopically light, with δ13C = –24 to –31‰ (Ozima et al., 1991; Shelkov et al., 1997; De et al., 2001). Nitrogen concentrations are low (~20 to 500 ppmw), and δ15N ranges from –3.6 to 12.8‰ with an average of 3.7‰ (Shelkov et al., 1997; Vicenzi and Heaney, 2001; Yokochi et al., 2008). The coupled isotopic distribution of C and N shows that the compositional field for carbonado is distinctly different from that of conventional diamonds (figure 10).
Figure 11 shows photoluminescence (PL) spectra of carbonado, which are similar to those of irradiated and heated CVD diamond (Clark et al., 1992). The characteristic peaks at 1.945 eV and 2.156 eV are attributed to nitrogen vacancy (NV) defects in type Ib diamonds. Wang et al. (2009) report a substantial amount of nonaggregated N in type Ib diamonds with H2 and H3 defects. Hydrogen-containing defects (H1) and NV defects are also reported by Nadolinny et al. (2003).
Cathodoluminescence of large (approximately 200 µm) monocrystals of diamond in carbonado exhibit orange and green tones (Magee and Taylor, 1999; De et al., 2001; Yokochi et al., 2008). However, blue luminescence in large diamonds, embedded in an orange luminescent matrix of submicron diamond, are also reported (Rondeau et al., 2008). The range in colors is attributed to various N-V (nitrogen-vacancy) defects.
Synchrotron infrared measurements of carbonado have shown the presence of single nitrogen (type Ib) substitution and hydrogen (Garai et al., 2006), in contrast to aggregated N typical of conventional type Ia diamonds that have undergone prolonged high P-T annealing in the mantle.
Carbonado has been dated by Ozima and Tatsumoto (1997) and Sano et al. (2002), on samples derived from conglomerates (again, see figure 2) that have been reworked over a period from at least 1.7 Ga to approximately 3.8 Ga (Pedreira and De Waele, 2008). It is relevant to note that, unlike the dating of conventional diamond, which is based on trapped mineral inclusions (garnet, pyroxene, and sulfides), the age of carbonado discussed in this review was determined directly on diamond. Following a robust chemical protocol of acid dissolution to remove all nondiamond material, the cleansed carbonado was subjected to two different instrumental methods of analyses. Ozima and Tatsumoto (1997) used high-resolution mass spectrometry on carat-sized samples from the Central African Republic, while Sano et al. (2002) employed an ion probe that allowed for micron-sized spot analyses on larger samples from Brazil. Both studies report ages of 2.6–3.8 Ga on implanted radiogenic lead. Although this method of age determination is unconventional, it is important to note that the Archean result is consistent with trapped crustal inclusions (Sano et al., 2002) of zircon (1.7–3.6 Ga), rutile (3.9 Ga), and quartz (3.2 Ga), and with the antiquity of the basement in the São Francisco craton, which is 3.3–3.7 Ga (Barbosa and Sabate, 2004).
In summary, the chemical and physical characteristics of carbonado point to marked similarities with rapidly quenched type Ib diamonds and CVD diamond, both of which contain significant hydrogen. But there are also major differences: carbonado has pores and patinas with distinctions in C and N isotopes, an absence of mantle minerals, and the presence of exotic metal inclusions. Carbonado is unquestionably one of the most unusual forms of diamond ever reported. Because it has never been found in typical diamond-bearing rocks, the many proposed origins are varied, and none are uniformly accepted.
Theories on the genesis of carbonado fall into five categories:
- Meteoritic impact (Smith and Dawson, 1985)
- Growth and sintering in the crust or mantle (Burgess et al., 1998; Ishibashi et al., 2012; Chen and Van Tendeloo, 1999; Heaney et al., 2005; Kagi and Fukura, 2008; Ketcham and Koeberl, 2013)
- Subduction (De Carli, 1997; Irifune et al., 2004)
- Radioactive ion implantation of carbon substrates (Kaminsky, 1991; Ozima et al., 1991; Shibata et al., 1993; Kagi et al., 1994; Daulton and Ozima, 1996; Ozima and Tatsumoto, 1997)
- Extraterrestrial (Haggerty, 1996, 2014)
Meteoritic Impact. This model was based on a correlation with the Bangui magnetic anomaly in the Central African Republic. Originally thought to be a buried iron meteorite, it was subsequently shown to be a crustal-derived banded iron ore body (Regan and Marsh, 1982), similar to the magnetic anomaly and giant iron ore deposit in Kursk, Russia (Taylor et al., 2014). Because the C-isotopic composition of carbonado is very light (δ13C = –21 to –34‰), the presence of biologically derived organic material in the target rocks is assumed. The impact model is unlikely because the C substrate, necessarily of cyanobacteria at ~3.8 Ga, would have been inordinately large (estimated at several cubic km and uncontaminated by crustal material), to account for the estimated two metric tons of carbonado recovered to date (Haggerty, 2014). In addition, the known occurrences of meteorite-impact diamonds (Arizona, United States; Ries, Germany; and Popigai, Russia) are discrete microdiamonds rather than carbonado (Frondel and Marvin, 1967; Hough et al., 1995; Shelkov et al., 1997).
Growth and Sintering in the Crust or Mantle. Some models propose catalytically assisted C-saturated “fluids” in the crust or the mantle. Such fluids provide a source of carbon and a medium capable of drastically decreasing the P-T stability limits of diamond from the traditional 5–6 GPa and 1200–1300°C, at a depth of 200 km or more (Shirey and Shigley, 2013). These “fluids” are hydrous, supercritical (i.e., beyond the point of coexisting fluid + vapor), and intensely oxidized so that diamond crystallization is unlikely, and diamond survival even less so. An analogy with loosely aggregated framesite, found in mantle-derived kimberlites, has also been suggested, but is unsatisfactory because the diamonds are semiprecious, free of pores and patina, and lack the highly reduced mineral suite of metals, carbides, and nitrides.
Subduction. Although carbonado is present in meta-conglomerates (again, see figure 2), these robustly cemented diamonds are very different from the ultra-high-pressure, subducted, metamorphic diamonds found in continental collision zones in Norway, China, Kazakhstan, Greece, and Germany (Ogasawara, 2005). The diamonds at these localities are single crystals and are armored by zircon, garnet, pyroxene, and amphibole that acted as insulating capsules. Sintering would be necessary to form carbonado. This is possible at high pressures and temperatures in the mantle, but the process would have incorporated one or more mantle minerals such as olivine, garnet, pyroxene, and spinel, none of which are observed. Moreover, the inferred subducted plates are oceanic and basaltic in composition and on transformation at high P-T would produce large concentrations of garnet + pyroxene (namely eclogite), which again is not encountered. Transport to Earth’s surface is either not considered or is tentatively ascribed to deep mantle volcanic plumes in both the subduction and radiation models (below).
Radioactive Ion Implantation of Carbon Substrates. Radiation-induced diamond is on the scale of nanometers and cannot account for larger diamonds in the micrometer to millimeter size range found in carbonado. Once diamond is formed, low-energy implantation alters the atomic structure and turns the diamond green; high-energy ion doses produce graphite rather than additional diamond (Kalish and Prawer, 1995). There were no coal deposits at 2–3 Ga, and the radiation-induced diamonds recovered from very rare carburanium (U-rich hydrocarbon) are low in abundance and nanometer in size. Proposals of radiation sintering, and even pore formation, are equally untenable.
Extraterrestrial Origin. The extraterrestrial (ET) model was initially proposed because traditional earthbound scenarios failed to account for major characteristics of carbonado, namely diamond porosity, patina, polycrystallinity, rarity, and location (Haggerty, 2014). Pores are incompatible with high-pressure environments; therefore, carbonado cannot have formed under the same conditions in which conventional diamonds form in the mantle at depths of approximately 200 km. The pores in carbonado (again, see figures 3 and 4) are similar to vesicles in basalts that degassed at low pressures under near-surface conditions from a molten or semi-molten magma. This rules out an origin for carbonado in the crust or the mantle, because liquefaction of carbon is not readily accomplished. In fact, diamond is solid in Earth’s core (6,380 km and approximately 350 GPa and 7000 K; Bundy et al., 1996; Oganov et al., 2013). Consequently, none of the interpreted melt-like features in carbonado (figures 5–7) can possibly be of terrestrial origin. Furthermore, not a single carbonado has been reported from kimberlite-lamproite suites in the nearly 700 metric tons of diamond mined since about 1900 (Levinson et al., 1992). As noted above, carbonado differs from conventional diamond in several respects:
- Hydrogen is prominent and N is dispersed, which is the case for <1% of conventional diamonds (i.e., type Ib).
- Combined N and C isotopes are distinctly not terrestrial (figure 10).
- There are remarkable similarities to diamonds formed by carbon vapor deposition (figure 11), a process that requires vacuum conditions and plasma temperatures that cannot possibly be accomplished in any natural environment on Earth.
- Carbonado lacks the characteristic suite of diamond inclusion minerals such as Cr-garnet, Na-Al-pyroxene, Mg-olivine, Mg-chromite, and Fe-Ni-sulfides, and is instead replaced by exotic, reduced metal alloys and minerals.
The ET scenario posits that carbonado originated from carbon-rich, diamond-bearing stellar bodies and/or disrupted C-bearing planets (Haggerty, 2014). All of the characteristic features of carbonado are satisfied: CVD diamond is the sintering glue to microdiamonds in carbonado; the loss of interstellar H produced the pores, and the patina and flow textures are stellar or interstellar high-vacuum melt products. The model further proposes that carbonado was transported to Earth as a large diamond meteorite or as smaller diamond “plums” in a carbonaceous meteoritic matrix, possibly during the Late Heavy Bombardment (3.8–4.2 Ga), in which the inner solar system was pummeled by meteorites (Fassett and Minton, 2013; Abramov et al., 2013). The numerous craters on the moon are considered evidence of the bombardment (Marchi et al., 2013). The theoretical age of this event corresponds to the oldest age determined for carbonado (3.8 ± 1.8 Ga). This would account for its rarity as a single known occurrence on the São Francisco and Congo cratons, which were once joined geologically as the supercontinents of Nuna and Rodinia. Carbonado was undoubtedly widespread during the bombardment, but the carbonado falls were largely into the expansive oceans that existed at that time. Supercontinent disruption and subduction followed, leaving only the preserved remnants of carbonado on an island that is today split between Brazil and the Central African Republic.
The recent discovery of patches of sub-micron diamonds in Libyan desert glass, a high-silica natural glass that is thought to be of cometary origin (Kramers et al., 2013), lends credence to the ET model for carbonado. This view is supported by the growing lines of evidence for (1) synthetically produced diamond-like glass (Shumilova et al., 2016a, b); (2) nanodiamond encased in glassy carbon shells in the interstellar media (Yastrebov and Smith, 2009); and (3) glassy carbon and nanodiamond produced experimentally (Shiell et al., 2016) and in supernova shock waves (Stroud et al., 2011). Another supporting fact is the discovery of asteroid 2008 TC3, which was tracked upon entering Earth’s atmosphere and landed in North Sudan as a fragmented, diamond-bearing ureilite (Miyahara et al., 2015). Unusual in several respects, the meteorite contains diamonds measuring approximately 100 µm. These are exceptionally large for ureilites, whose diamonds typically measure 1–5 µm, and substantially larger than nanodiamonds of pre-solar origin in carbonaceous chondrites. These reports are complemented by the unexpected discovery that Mercury has a crust of graphite, now covered by volcanic rocks but exposed in meteorite craters (Peplowski et al., 2016), that may prove to be diamond bearing.
Carbonado (figure 12) is the most unusual form of diamond on Earth. Despite many mineralogical clues not observed in conventional diamonds, its mode of origin remains largely unexplained. Discovering the origin of carbonado would herald a whole new mode of diamond formation and could represent a remarkable form of extraterrestrial carbon delivery to Earth. The extraterrestrial model, although conceptual and supported by astrophysical data, will only be vindicated by the discovery of carbonado in the asteroid belt by remote sensing, or by an observed diamond meteorite fall that is dark in color, porous, and patinaed.
Fieldwork for this study was supported by a faculty research grant from the University of Massachusetts Amherst, and by De Beers. Laboratory work was supported by the National Science Foundation and Florida International University. Thanks to Jose Ricardo Pisani and the late Jeff Watkins, who provided enormous logistical help and hospitality during fieldwork in Brazil. Thanks also to my many colleagues and critics, from whom I’ve benefited enormously in active discussions on the controversial issues surrounding the origin of carbonado. And lastly to the reviewers for detailed and constructive comments that led to improvements in presentation. To all I express my sincere appreciation.
Abramov O., Kring D.A., Mojzsis S.J. (2013) The impact environment of the Hadean Earth. Chemie der Erde - Geochemistry, Vol. 73, No. 3, pp. 227–248, http://dx.doi.org/10.1016/j.chemer.2013.08.004
Barbosa J.S.F., Sabate P. (2004) Archean and Paleoproterozoic crust of the São Francisco craton, Bahia, Brazil: Geodynamic features. Precambrian Research, Vol. 133, No. 1-2, pp. 1–27, http://dx.doi.org/10.1016/j.precamres.2004.03.001
Bundy F.P., Bassett W.A., Weathers M.S., Hemley R.J., Mao H.U., Goncharov A.F. (1996) The pressure-temperature phase and transformation diagram for carbon; updated through 1994. Carbon, Vol. 34, No. 2, pp. 141–153, http://dx.doi.org/10.1016/0008-6223(96)00170-4
Burgess R., Johnson L.H., Mattey D.P., Harris J.W., Turner G. (1998) He, Ar and C isotopes in coated and polycrystalline diamonds. Chemical Geology, Vol. 146, No. 3-4, pp. 205–217, http://dx.doi.org/10.1016/S0009-2541(98)00011-4
Burns R.C., Davies G.J. (1992) Growth of synthetic diamond. In J.E. Field, Ed., The Properties of Natural and Synthetic Diamond. Academic Press, London, pp. 395–422.
Cartigny P., Harris J.W., Javoy M. (1998) Eclogitic diamond formation at Jwaneng: No room for a recycled component. Science, Vol. 280, No. 5368, pp. 1421–1424, http://dx.doi.org/10.1126/science.280.5368.1421
Chen J.H., Van Tendeloo G. (1999) Microstructure of tough polycrystalline natural diamond. Journal of Electron Microscopy, Vol. 48, No. 2, pp. 121–129, http://dx.doi.org/10.1093/oxfordjournals.jmicro.a023658
Clark C.D., Collins A.T., Woods G.S. (1992) Absorption and luminescence spectroscopy. In J.E. Field, Ed., The Properties of Natural and Synthetic Diamond. Academic Press, London, pp. 35–79.
Daulton T.L., Ozima M. (1996) Radiation-induced diamond formation in uranium-rich carbonaceous materials. Science, Vol. 271, No. 5253, pp. 1260–1263, http://dx.doi.org/10.1126/science.271.5253.1260
De Carli P.S. (1997) Carbonado origin: Impact vs. subduction. Abstract, American Geophysical Union Meeting, Baltimore, Maryland, S333.
De S., Heaney P.J., Hargraves R.B., Vicenzi E.P., Taylor P.T. (1998) Microstructural observations of polycrystalline diamond: a contribution to the carbonado conundrum. Earth and Planetary Science Letters, Vol. 164, No. 3-4, pp. 421–433, http://dx.doi.org/10.1016/S0012-821X(98)00229-5
De S., Heaney P.J., Vicenzi E.P., Wang J.H. (2001) Chemical heterogeneity in carbonado, an enigmatic polycrystalline diamond. Earth and Planetary Science Letters, Vol. 185, No. 3-4, pp. 315–330, http://dx.doi.org/10.1016/S0012-821X(00)00369-1
De Waele B., Johnson S.P., Pisarevsky S.A. (2008) Palaeoproterozoic to Neoproterozoic growth and evolution of the eastern Congo Craton: Its role in the Rodinia puzzle. Precambrian Research, Vol. 160, No. 1-2, pp. 127–141, http://doi.org/10.1016/j.precamres.2007.04.020
Dominguez J.M.L. (1996) As coberturas plataformais do proterzoico medio e superior (The Middle and Upper Proterozoic). In Mapa Geologico Do Estado Da Bahia. Secretaria da Geologia E Recursos Minerais, Salvador, pp. 105–125.
Fassett C.I., Minton D.A. (2013) Impact bombardment of the terrestrial planets and the early history of the solar system. Nature Geoscience, Vol. 6, No. 7, pp. 520–524, http://dx.doi.org/10.1038/ngeo1841
Frondel C., Marvin U.B. (1967) Lonsdaleite, a hexagonal polymorph of diamond. Nature, Vol. 214, No. 5088, pp. 587–589, http://dx.doi.org/10.1038/214587a0
Garai J., Haggerty S.E., Rekhi S., Chance M. (2006) Infrared absorption investigations confirm the extraterrestrial origin of carbonado diamonds. The Astrophysical Journal Letters, Vol. 653, No. 2, pp. L153–L156, http://dx.doi.org/10.1086/510451
Gorshkov A.I., Titkov S.V., Pleshakov A.M., Sivtov A.V., Bershov L.V. (1996) Inclusions of native metals and other mineral phases into carbonado from Ubangi region (Central Africa). Geology of Ore Deposits, Vol. 38, pp. 114–119.
Haggerty S.E. (1996) Diamond-carbonado: Models for a new meteorite class of circum-stellar or solar system origin. Abstract, American Geophysical Union, Spring meeting, Baltimore, p. S143.
Haggerty S.E. (2014) Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model. Earth-Science Reviews, Vol. 130, pp. 49–72, http://dx.doi.org/10.1016/j.earscirev.2013.12.008
Heaney P.J., Vicenzi E.P., De S. (2005) Strange diamonds: The mysterious origins of carbonado and framesite. Elements, Vol. 1, No. 2, pp. 85–89, http://dx.doi.org/10.2113/gselements.1.2.85
de Heer W.A., Poncharal P., Berger C., Gezo J., Song Z., Bettini J., Ugarte D. (2005) Liquid carbon, carbon-glass beads, and the crystallization of carbon nanotubes. Science, Vol. 307, No. 5711, pp. 907–910, http://dx.doi.org/10.1126/science.1107035
Hough R.M., Gilmour I., Pillinger C.T., Arden J.W., Gilkes K.W.R., Yuan J., Milledge H.J. (1995) Diamond and silicon carbide in impact melt rock from the Ries impact crater. Nature, Vol. 378, No. 6552, pp. 41–44, http://dx.doi.org/10.1038/378041a0
Irifune T., Kurio A., Sakamoto S., Inoue T., Sumiya H., Funakoshi K. (2004) Formation of pure polycrystalline diamond by direct conversion of graphite at high pressure and high temperature. Physics of the Earth and Planetary Interiors, Vol. 143-144, pp. 593–600, http://dx.doi.org/10.1016/j.pepi.2003.06.004
Ishibashi H., Kagi H., Sakuai H., Ohfuji H., Sumino H. (2012) Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: Implication from IR spectra and microtextural observations. American Mineralogist, Vol. 97, No. 8-9, pp. 1366–1372, http://dx.doi.org/10.2138/am.2012.4097
Jones A.P., Beard A., Milledge H.J., Cressey G., Kirk C., DeCarli P. (2003) A new nitride mineral in carbonado. Eighth International Kimberlite Conference Abstracts, Victoria, Canada, p. A95.
Kagi H., Fukura S. (2008) Infrared and Raman spectroscopic observations of Central African carbonado and implications for its origin. European Journal of Mineralogy, Vol. 20, No. 3, pp. 387–393, http://dx.doi.org/10.1127/0935-1221/2008/0020-1817
Kagi H., Takahashi K., Hidaka H., Masuda A. (1994) Chemical properties of Central African carbonado and its genetic implications. Geochimica et Cosmochimica Acta, Vol. 58, No. 12, pp. 2629–2638, http://dx.doi.org/10.1016/0016-7037(94)90133-3
Kalish R., Prawer S. (1995) Graphitization of diamond by ion impact: Fundamentals and applications. Nuclear Instruments and Methods in Physics Research Section B, Vol. 106, No. 1-4, pp. 492–499, http://dx.doi.org/10.1016/0168-583X(95)00758-X
Kaminsky F.V. (1991) Carbonado and yakutite: Properties and possible genesis. In H.O.A. Meyer and O.H. Leonardos, Eds., Proceedings of the 5th International Kimberlite Conference, Araxá, Brazil, CPRM Special Publication, pp. 136–143.
Ketcham R.A., Koeberl C. (2013) New textural evidence on the origin of carbonado diamond: An example of 3-D petrography using X-ray computed tomography. Geosphere, Vol. 9, No. 5, pp. 1336–1347, http://dx.doi.org/10.1130/GES00908.1
Kramers J.D., Andreoli M.A.G., Atanasova M., Belyanin G.A., Blocke D.L., Franklyn C., Harris C., Lekgoathi M., Montross C.S., Ntsoane T., Pischedda V., Segonyane P., Viljoen K.S., Westraadt J.E. (2013) Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass strewnfield, SW Egypt: Evidence for a shocked comet fragment. Earth and Planetary Science Letters, Vol. 382, pp. 21–31, http://dx.doi.org/10.1016/j.epsl.2013.09.003
Leonardos O.H. (1937) Diamante e Carbonado no Estado da Bahia. Metallurgia Servisio De Fomento da Produccao Mineral, Vol. 19, pp. 1–23.
Levinson A.A., Gurney J.J., Kirkley M.B. (1992) Diamond sources and production: Past, present, and future. G&G, Vol. 28, No. 4, pp. 234–254, http://dx.doi.org/10.5741/GEMS.28.4.234
Magee C.W., Taylor W.R. (1999) Constraints from luminescence on the history and origin of carbonado. In J.J. Gurney et al., Eds., Proceedings of the VIIth International Kimberlite Conference, Red Roof Design Publications, Cape Town, pp. 529–532.
Makeev A.B., Ivanuch W., Obyden S.K., Saparin G.V., Filippov V.N. (2002) Mineralogy, composition of inclusions, and cathodoluminescence of carbonado from Bahia State, Brazil. Geology of Ore Deposits, Vol. 44, No. 2, pp. 87–102.
Marchi S., Bottke W.F., Cohen B.A., Wünnemann K., Kring D.A., McSween H.Y., De Sanctis M.C., O’Brien D.P., Schenk P., Raymond C.A., Russell C.T. (2013) High-velocity collisions from the lunar cataclysm recorded in asteroidal meteorites. Nature Geoscience, Vol. 6, No. 4, pp. 303–307, http://dx.doi.org/10.1038/ngeo1769
Mitchell T.M., Toy V., Di Toro G., Renner J., Sibson R.H. (2016) Fault welding by pseudotachylyte formation. Geology, Vol. 44, No. 12, pp. 1059–1062, http://dx.doi.org/10.1130/G38373.1
Miyahara M., Ohtani E., El Goresy A., Lin Y., Feng L., Zhang J.-C., Gillet P., Nagase T., Muto J., Nishijima M. (2015) Unique large diamonds in an ureilite from Almahata Sitta 2008 TC3 asteroid. Geochimica et Cosmochimica Acta, Vol. 163, pp. 14–26, http://dx.doi.org/10.1016/j.gca.2015.04.035
Nadolinny V.A., Shatsky V.S., Sobolev N.V., Twitchen D.J., Yuryeva O.P., Vasilevsky I.A., Lebedev V.N. (2003) Observation and interpretation of paramagnetic defects in Brazilian and Central African carbonados. American Mineralogist, Vol. 88, No. 1, pp. 11–17, http://dx.doi.org/10.2138/am-2003-0102
Oganov A.R., Hemley R.J., Hazen R.M., Jones A.P. (2013) Structure, bonding, and mineralogy of carbon at extreme conditions. In R.M Hazen, A.P. Jones., and J.A. Baross, Eds., Carbon in Earth. Reviews in Mineralogy & Geochemistry, Vol. 75. Mineralogical Society of America, Chantilly, VA, pp. 47–77.
Ogasawara Y. (2005) Microdiamonds in ultrahigh-pressure metamorphic rocks. Elements, Vol. 1, No. 2, pp. 91–96, http://dx.doi.org/10.2113/gselements.1.2.91
Orlov Y.L. (1977) The Mineralogy of the Diamond. John Wiley & Sons, New York, 235 pp.
Ozima M., Tatsumoto M. (1997) Radiation-induced diamond crystallization: Origin of carbonados and its implications on meteorite nano-diamonds. Geochimica et Cosmochimica Acta, Vol. 61, No. 2, pp. 369–376, http://dx.doi.org/10.1016/S0016-7037(96)00346-8 Ozima M., Zashu S., Tomura K., Matsuhisa Y. (1991) Constraints from noble-gas contents on the origin of carbonado diamonds. Nature, Vol. 351, No. 6326, pp. 472–474, http://dx.doi.org/10.1038/351472a0
Pedreira A.J., De Waele B. (2008) Contemporaneous evolution of the Paleoproterozoic-Mesoproterozoic sedimentary basins of the São Francisco–Congo craton. In R.J. Pankhurst, R.A.J. Trouw, B.B. de Brito Neves, and M.J. De Wit, Eds., West Gondwana: Pre-Cenozoic Correlations across the South Atlantic Region. Geological Society of London Special Publication 294, pp. 33–48.
Peplowski P.N., Klima R.L., Lawrence D.J., Ernst C.M., Denevi B.W., Frank E.A., Goldsten J.O., Murchie S.L., Nittler L.R., Solomon S.C. (2016) Remote sensing evidence for an ancient carbon-bearing crust on Mercury. Nature Geoscience, Vol. 9, No. 4, pp. 273–276, http://dx.doi.org/10.1038/ngeo2669
Petrovsky V.A., Shiryaev A.A., Lyutoev V.P., Sukharev A.E., Martins M. (2010) Morphology and defects of diamond grains in carbonado: Clues to carbonado genesis. European Journal of Mineralogy, Vol. 22, No. 1, pp. 35–47, http://dx.doi.org/10.1127/0935-1221/2010/0022-1978
Regan R.D., Marsh B.D. (1982) The Bangui magnetic anomaly: Its geological origin. Journal of Geophysical Research: Solid Earth. Vol. 87, No. B2, pp. 1107–1120, http://dx.doi.org/10.1029/JB087iB02p01107
Rondeau B., Sautter V., Barjon J. (2008) New columnar texture of carbonado: Cathodoluminescence study. Diamond and Related Materials, Vol. 17, No. 11, pp. 1897–1901, http://dx.doi.org/10.1016/j.diamond.2008.04.006
Sano Y., Yokochi R., Terada K., Chaves M.L., Ozima M. (2002) Ion microprobe Pb–Pb dating of carbonado, polycrystalline diamond. Precambrian Research, Vol. 113, No. 1-2, pp. 155–168, http://dx.doi.org/10.1016/S0301-9268(01)00208-X
Sato Y., Kamo M. (1992) Synthesis of diamond from the vapor phase. In J.E. Field, Ed., The Properties of Natural and Synthetic Diamond, pp. 423–469. Academic Press, London.
Shelkov D., Verkhovsky A.B., Milledge H.J., Pillenger C.T. (1997) Carbonado: A comparison between Brazilian and Ubangui sources with other forms of microcrystalline diamond based on carbon and nitrogen isotopes. Russian Geology and Geophysics, Vol. 38, No. 2, pp. 315–322.
Shibata K., Kamioka H., Kaminsky F.V., Koptil V.I., Svisero D.P. (1993) Rare earth element patterns of carbonado and yakutite: Evidence for their crustal origin. Mineralogical Magazine, Vol. 57, No. 389, pp. 607–611, http://dx.doi.org/10.1180/minmag.1993.057.389.05
Shiell T.B., McCulloch D.G., Bradby J.E., Haberl B., Boehler R., McKenzie D.R. (2016) Nanocrystalline hexagonal diamond formed from glassy carbon. Scientific Reports, Vol. 6, No. 1, article no. 37232, http://dx.doi.org/10.1038/srep37232
Shirey S.B., Shigley J.E. (2013) Recent advances in understanding the geology of diamonds. G&G, Vol. 49, No. 4, pp. 188–222, http://dx.doi.org/10.5741/GEMS.49.4.188
Shumilova T.G., Isaenko S.I., Tkachev S.N. (2016a) Diamond formation through metastable liquid carbon. Diamond and Related Materials, Vol. 62, pp. 42–48, http://dx.doi.org/10.1016/j.diamond.2015.12.015
Shumilova T.G., Tkachev S.N., Isaenko S.I., Shevchuk S.S., Rappenglück M.A., Kazakov V.A. (2016b) A “diamond-like star” in the lab. Diamond-like glass. Carbon, Vol. 100, pp. 703–709, http://dx.doi.org/10.1016/j.carbon.2016.01.068
Smith J.V., Dawson J.B. (1985) Carbonado: Diamond aggregates from early impacts of crustal rocks? Geology, Vol. 13, No. 5, pp. 342–343, http://dx.doi.org/10.1130/0091-7613(1985)13%3C342:CDAFEI%3E2.0.CO;2
Stroud R.M., Chisholm M.F., Heck P.R., Alexander C.M.O’D., Nittler L.R. (2011) Supernova shock-wave-induced co-formation of glassy carbon and nanodiamond. The Astrophysical Journal Letters, Vol. 738, No. 2, pp. L27–L32, http://dx.doi.org/10.1088/2041-8205/738/2/L27
Svisero D.P. (1995) Distribution and origin of diamonds in Brazil: An overview. Journal of Geodynamics, Vol. 20, No. 4, pp. 493–514, http://dx.doi.org/10.1016/0264-3707(95)00017-4
Taylor P.T., Kis K.I., Wittmann G. (2014) Satellite-altitude horizontal magnetic gradient anomalies used to define the Kursk magnetic anomaly. Journal of Applied Geophysics, Vol. 109, pp. 133–139, http://dx.doi.org/10.1016/j.jappgeo.2014.07.018
Torsvik T.H. (2003) The Rodinia jigsaw puzzle. Science, Vol. 300, No. 5624, pp. 1379–1381, http://dx.doi.org/10.1126/science.1083469
Trueb L.F., Butterman W.C. (1969) Carbonado: A microstructural study. American Mineralogist, Vol. 54, No. 3-4, pp. 412–425.
Trueb L.F., De Wys E.C. (1969) Carbonado: Natural polycrystalline diamond. Science, Vol. 165, No. 3895, pp. 799–802, http://dx.doi.org/10.1126/science.165.3895.799
Vicenzi E.P., Heaney P.J. (2001) The carbon and nitrogen isotopic composition of carbonado diamond: an in-situ study. Eleventh Annual VM Goldschmidt Conference, A513.
Wang W., Lu R., Moses T. (2009) Photoluminescence features of carbonado diamonds. GIA News from Research, July 21, https://www.gia.edu/gia-news-research-nr72109
Yastrebov S., Smith R. (2009) Nanodiamonds enveloped in glassy carbon shells and the origin of the 2175 Å optical extinction feature. The Astrophysical Journal, Vol. 697, No. 2, pp. 1822–1826, http://dx.doi.org/10.1088/0004-637X/697/2/1822
Yokochi R., Ohnenstetter D., Sano Y. (2008) Intragrain variation in δ13C and nitrogen concentration associated with textural heterogeneities of carbonado. Canadian Mineralogist, Vol. 46, No. 5, pp. 1283–1296, http://dx.doi.org/10.3749/canmin.46.5.1283 | 0.912591 | 3.11859 |
Sedna is a solar system body that is one of the most distant bodies found in our solar system. The object's closest approach to the sun is far greater than Pluto's distance away from Earth — at a spot where the sun is so tiny, according to NASA, that you could blot it out with a pin.
At 8 billion miles (12.8 billion kilometers) away, it's hard to figure out things such as surface features, but one thing astronomers have been able to identify is Sedna's distinct reddish color. In 2004, it was described as the second-reddest object in our solar system, after Mars.
Sedna was discovered by a team led by Mike Brown, an astronomer at the California Institute of Technology. The discovery of Sedna and other objects similar to it was a large impetus behind demoting Pluto from planetary status in 2006.
Discovery and basic statistics
Brown's team found Sedna in 2003 as part of a larger survey of the solar system that began in 2001. Using the Samuel Oschin Telescope at the Palomar Observatory (east of San Diego) as well as Palomar's QUEST camera, the astronomers would take pictures of a tiny spot in the sky — one per hour for three hours — and see if they could find something that moved, Brown said in an explanation page about the discovery.
"The many billions of stars and galaxies visible in the sky appear stationary, while satellites, planets, asteroids, and comets appear to move. Objects in the inner Oort Cloud are extremely distant and so move extremely slowly," he said.
The Oort Cloud is a theorized area far in the solar system that is supposed to contain billions of icy objects that, if they receive a gravitational push toward the sun and warm up, turn into comets as the sun's energy melts the ice. Sedna, however, was much bigger than a comet. Estimates for Sedna's size vary, but it is believed to be slightly smaller than the size of Pluto (1,400 miles or 2,250 kilometers in diameter).[Related: New Horizons' Pluto Flyby: Latest News, Images and Video]
Sedna takes some time to orbit the sun, not only because of its vast distance but also because its orbit is so elliptical or oval-shaped. The small world takes roughly 10,000 years to complete one circuit around the sun. At the time of its discovery, it was at one of the closest points of its orbit to the sun, making it easier to spot.
Rise of the dwarf planets
Sedna was not the only object close to Pluto's size to be discovered in the early 2000s. Brown's team also found Quaoar, another dwarf planet candidate, and Eris. Eris was initially thought to be even larger than Pluto, prompting some to call it the solar system's 10th planet. (Later measurements showed that it may be smaller than Pluto, but at that distance and with its relatively small size, it's hard to say for sure.)
These discoveries spurred the International Astronomical Union to examine the definition of a planet in a 2006 meeting in Prague. The astronomers present voted that a planet 1) is a body orbiting the sun without being another object's satellite, 2) has a mass large enough to be nearly round, and 3) has cleared debris from its orbit. Dwarf planets, while also in orbit around the sun and mostly round, have not cleared debris from their orbits.
"Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding," the IAU said in a statement at the time.
"This applies, in particular, to the designation 'planets.' The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information."
More about Sedna's odd orbit
Sedna's orbit is extremely elongated, which is quite different from the circular planetary orbits that feature in our solar system. Brown told Space.com in 2011 that it was likely due to a close encounter.
"So the zeroth-order piece of information is that, somewhere out there, something perturbed Sedna, and that thing is no longer there. Now, that thing could've been another planet; it could have been a star that came close to the sun; it could have been a lot of stars, if the sun was born in a cluster," Brown said.
"Somewhere in Sedna's history, it tells you about the formation of the sun and the history of the sun, and there's clearly information there. But here's the problem when you only have one [object like Sedna]: You don't know which of these many different ideas could be true."
In 2014, astronomers announced the discovery of 2012 VP113 (nicknamed "Biden") that is also believed to be in the inner Oort cloud. The new object's orbit is also extremely elongated, suggesting that perhaps the same thing perturbed both Sedna and 2012 VP113. | 0.891596 | 3.917553 |
A telescopelashed to a giant balloon is poised to lift off from Sweden as early as Mondayto study the surface of the sun.
DubbedSunrise, the balloon observatory should stay aloft for nearly a week as ittravels from the Esrange Space Center in Sweden over the arctic to a safetouchdown in Canada. The mission is part of a NASA experiment for balloonlaunches and is slated to fly up to six days to snap high-resolutionphotographs of the sun's surface.
The telescopeand its gondola of scientific instruments are a 2-ton payload that will beborne under a balloon that is larger than a sports arena, filled with nearly 34million cubic feet of helium. It should cross the arctic at an altitude ofnearly 23 miles (37 km). To track the sun while it floats above Earth, thegondola has a pointing system that allows it to rotate horizontally.
ThroughSunrise, scientists seek to demystify some of the fascinating and destructivephenomena caused by magnetic fields on the sun's surface. Those fields canbe associated with sunspots and explosive coronal mass ejections which lead tospace weather events that can affect the climate here on Earth. Space weather,like energeticsolar flares and solar winds, can damage satellites in Earth's orbit,endanger astronauts and even disrupt power grids on the ground.
Sunriseproject managers plan to launch the solar telescope on June 1, but could trythroughout early July to await pristine weather conditions.
Sunrise ispart of a NASA experiment with balloon-launched research projects, this one inconjunction with scientists and agencies from Germany, Spain and the UnitedStates. Using balloons, NASA seeks to cut the cost of launching orbitalsatellites. While Sunrise is estimated to cost $60 million to $80 million, thecost of launching a similar-sized telescope into orbit might run as high as$500 million, Michael Knolker, director of National Center for AtmosphericResearch's High Altitude Observatory in Boulder, Colo., told SPACE.com lastyear.
This is thegondola's second launch after a successful test-run over the ColumbiaScientific Balloon Facility in Fort Sumner, New Mexico, in 2007. Inthat test, the balloon launched without the telescope.
- Image Gallery - Sun Storms
- Video - Sun Storms: Havoc on Our Electronic World
- Plan to Send Hot Air Balloon to Saturn's Moon Titan | 0.840509 | 3.173052 |
Science, Tech, Math › Science Can a Planet Make a Sound in Space? Share Flipboard Email Print NASA Science Astronomy Solar System An Introduction to Astronomy Important Astronomers Stars, Planets, and Galaxies Space Exploration Chemistry Biology Physics Geology Weather & Climate By John P. Millis, Ph.D Updated July 25, 2019 Can a planet make a sound? It's an interesting question that gives us insight into the nature of sound waves. In a sense, planets do emit radiation which can be used to make sounds we can hear. How does that work? The Physics of Sound Waves Everything in the universe gives off radiation that — if our ears or eyes were sensitive to it — we could "hear" or "see". The spectrum of light that we actually perceive is very small, compared to the very large spectrum of available light, ranging from gamma-rays to radio waves. Signals that can be converted to sound make up only one part of that spectrum. The way people and animals hear sound is that sound waves travel through the air and eventually reach the ear. Inside, they bounce against the eardrum, which begins to vibrate. Those vibrations pass through small bones in the ear and cause small hairs to vibrate. The hairs act like tiny antennae and convert the vibrations into electrical signals that race to the brain through the nerves. The brain then interprets that as sound and what the timbre and pitch of the sound are. What About Sound in Space? Everyone has heard the line used to advertise the 1979 movie "Alien", "In space, no one can hear you scream." It's actually quite true as it relates to sound in space. For any sounds to be heard while someone is "in" space, there have to be molecules to vibrate. On our planet, air molecules vibrate and transmit sound to our ears. In space, there are few if any molecules to deliver sound waves to the ears of people in space. (Plus, if someone is in space, they're likely to be wearing a helmet and a spacesuit and still wouldn't hear anything "outside" because there's no air to transmit it.) That doesn't mean there aren't vibrations moving through space, only that there are no molecules to pick them up. However, those emissions can be used to create "false" sounds (that is, not the real "sound" a planet or other object might make). How does that work? As one example, people have captured emissions given off when charged particles from the Sun encounter our planet's magnetic field. The signals are at really high frequencies that our ears can't perceive. But, the signals can be slowed down enough to allow us to hear them. They sound eerie and weird, but those whistlers and cracks and pops and hums are just some of the many "songs" of Earth. Or, to be more specific, from Earth's magnetic field. In the 1990s, NASA explored the idea that emissions from other planets could be captured and processed so people could hear them. The resulting "music" is a collection of eerie, spooky sounds. There is a good sampling of them on NASA's Youtube site. These are literally artificial depictions of real events. It's very similar to making a recording of a cat meowing, for example, and slowing it down to hear all the variations in the cat's voice. Are We Really "Hearing" a Planet Sound? Not exactly. The planets don't sing pretty music when spaceships fly by. But, they do give off all those emissions that Voyager, New Horizons, Cassini, Galileo, and other probes can sample, gather, and transmit back to Earth. The music gets created as the scientists process the data to make it so that we can hear it. However, each planet does have its own unique "song". That's because each one has different frequencies that are emitted (due to different amounts of charged particles flying around and because of the various magnetic field strengths in our solar system). Every planet sound will be different, and so will the space around it. Astronomers have also converted data from spacecraft crossing the "boundary" of the solar system (called the heliopause) and turned that into sound as well. It's not associated with any planet but does show that signals can come from many places in space. Turning them into songs we can hear is a way of experiencing the universe with more than one sense. It All Began With Voyager The creation of "planetary sound" started when the Voyager 2 spacecraft swept past Jupiter, Saturn, and Uranus from 1979 to 1989. The probe picked up electromagnetic disturbances and charged particle fluxes, not actual sound. Charged particles (either bouncing off the planets from the Sun or produced by the planets themselves) travel in the space, usually kept in check by the planets' magnetospheres. Also, radio waves (again either reflected waves or produced by processes on the planets themselves) get trapped by the immense strength of a planet's magnetic field. The electromagnetic waves and charged particles were measured by the probe and the data from those measurements were then sent back to Earth for analysis. One interesting example was the so-called "Saturn kilometric radiation". It's a low-frequency radio emission, so it's actually lower than we can hear. It is produced as electrons move along magnetic field lines, and they're somehow related to auroral activity at the poles. At the time of the Voyager 2 flyby of Saturn, the scientists working with the planetary radio astronomy instrument detected this radiation, speeded it up and made a "song" that people could hear. How Do Data Collections Become Sound? In these days, when most people understand that data is simply a collection of ones and zeroes, the idea of turning data into music isn't such a wild idea. After all, the music we listen to on streaming services or our iPhones or personal players is all simply encoded data. Our music players reassemble the data back into sound waves that we can hear. In the Voyager 2 data, none of the measurements themselves were of actual sound waves. However, many of the electromagnetic wave and particle oscillation frequencies could be translated into sound in the same way that our personal music players take data and turn it into sound. All NASA had to do was to take the data accumulated by the Voyager probe and convert it into sound waves. That's where the "songs" of distant planets originate; as data from a spacecraft. | 0.921857 | 3.655138 |
Neptune’s core is composed of silicates and iron, and the temperature at its centre is probably greater than 5,000°C. The core is thought to be floating in an ocean of liquid diamond.
The core is surrounded by a hot and fluid mantle of water ice, ammonia and methane. It also contains a thin electrically charged liquid layer that is likely the source of Neptune’s magnetic field.
The outer atmosphere is composed of hydrogen, helium and trace amounts of methane, with thick clouds, high winds blowing at speeds of up to 2,200 km/h and storms.
Neptune is also encircled by a system of 5 thin, darkish dust rings whose composition is unknown.
The outermost of these rings, Adams, is in fact made up of arcs that were named Courage, Liberté, Egalité and Fraternité in honour of the French team that discovered them.
Neptune planetary data
- Mean diameter: 49,244 km
- Mass (Earth = 1): 17.1, i.e. 1.24.1023 t
- Mean density: 1,638 kg/m3
- Gravity at equator (Earth = 1): 1.14, i.e. 11.15 m/s2
- Mean distance from Sun (Earth-Sun = 1 AU): 30.1 AU, i.e. 4,504 million km
- Tilt of spin axis: 28.32°
- Rotation period (day cycle): 16.1 hrs, i.e. 16 hrs 06 min
- Revolution period around Sun: 164.8 Earth years, i.e. 60,182 Earth days
- Temperature at pressure of 0.1 bar –218°C (55 K)
- Moons: 14
The Neptunian system
Observations by the Voyager 2 probe and ground telescopes have enabled 14 moons to be identified.
The largest of these moons, Triton, spans 2,700 km and makes up 99.7% of the system’s total mass. It moves in a retrograde orbit around Neptune, meaning it is a Kuiper belt object captured by the planet. Its trajectory is also unstable due to tidal effects. It is gradually spiralling towards Neptune and will likely break up when it reaches the Roche limit1.
1 Edouard Roche was a 19th-century French astronomer who predicted that beyond a certain minimum distance from a planet, satellites would be torn apart by tidal forces. The rings of the giant planets in the solar system are beyond this limit, which explains why they can’t agglomerate into moons.
Voyager 2 is currently the only spacecraft to have flown by Neptune.
Launched on 20 August 1977, it flew past the planet on 25 August 1989.
Most of what we know about Neptune today has been deduced from the data obtained by this mission. | 0.883558 | 3.882949 |
AutoLens analysis steps up for Euclid's 100,000 strong gravitational lens challenge
The European Space Agency's Euclid satellite, due for launch in 2020, will set astronomers a huge challenge: to analyse one hundred thousand strong gravitational lenses. The gravitational deflection of light from distant astronomical sources by massive galaxies (strong lenses) along the light path can create multiple images of the source that are not just visually stunning, but are also valuable tools for probing our Universe. Now, in preparation for Euclid's challenge, researchers from the University of Nottingham have developed 'AutoLens', the first fully-automated analysis software for strong gravitational lenses. James Nightingale will present the first results from AutoLens at the National Astronomy Meeting 2016 in Nottingham on Friday, 1st July.
"AutoLens has demonstrated its capabilities with this stunning image of a strong gravitational lens system captured by the Hubble Space Telescope," said Nightingale, who developed AutoLens together with his colleague, Dr Simon Dye. "The software's reconstruction of the lensed source reveals in detail a distant pair of star-forming galaxies that are possibly in the early stages of merging. Within the lensed image of the source are small-scale distortions, which encode an imprint of how the lens galaxy's mass is distributed. AutoLens has a novel new approach to exploit this imprinted information and can accurately measure the distribution of dark matter in the lensing galaxy."
Historically, the analysis of strongly lensed images has been a very time consuming process, requiring a large amount of manual input to study just one system. To date, only around two hundred strong lens systems have been analysed. AutoLens can be run on 'massively parallel' computing architecture that uses multiple processors and requires no user input, so will be able to manage the huge amount of data delivered by the Euclid mission.
"Some of astronomy's most important results in the past five years have come from studying a handful of strong lenses. This small sample has allowed us to start to unravel the dark matter content of galaxies and the complex physics that drives their formation and evolution," said Nightingale. "It will be breathtaking to embark on a study of up to one hundred thousand such systems. We can only speculate as to what it will reveal about the nature of dark matter and its role in galaxy evolution." | 0.87963 | 3.71732 |
The NEOWISE mission uses a space telescope to hunt for asteroids and comets, including those that could pose a threat to Earth. During its planned four-year survey -- from December 2013 through 2017 -- NEOWISE will rapidly identify and characterize near-Earth objects, gathering data on their size and other key measurements.
Launched in December 2009 as the Wide-Field Infrared Survey Explorer, or WISE, the space telescope was originally designed to survey the sky in infrared, detecting asteroids, stars and some of the faintest galaxies in space. It did so successfully until completing its primary mission in February 2011. Observations resumed in December 2013, when the telescope was taken out of hibernation and re-purposed for the NEOWISE project as an instrument to study near-Earth objects, or NEOs, as well as more distant asteroids and comets.
September 2010: The frozen hydrogen cooling the Wide-Field Infrared Survey Explorer, or WISE, telescope is depleted. The survey continues as NEOWISE for an additional four months using the two shortest wavelength detectors.
February 2011: The WISE spacecraft is placed into hibernation after completing its search of the inner solar system.
December 2013: The telescope is taken out of hibernation and NEOWISE observations resume for a planned four-year mission.
During its primary mission, NEOWISE detected more than 158,000 minor planets, 34,000 of which had never been discovered previously.
NEOWISE data have been used to set limits on the numbers, orbits, sizes, and probable compositions of asteroids throughout our solar system, and enabled the discovery of the first known Earth Trojan asteroid. | 0.847189 | 3.509053 |
Helium could become the clean energy source of the 21st century. Colossal reserves could to be mined from the moon's surface and returned to Earth as a fuel for clean, green, radioactive-free power. So what are we waiting for?
Helium has a fascinating back story.
Here on Earth, helium is a rare resource derived from limited reserves of natural gas trapped in the Earth's crust. It has a handful of advanced medical and industrial applications, not to mention party balloons.
However, the Earth-shattering potential for helium lies in nuclear fusion: a technology not yet fully developed but promises abundant clean energy for centuries to come.
Scientists have long known that, despite its rarity on Earth, helium exists in abundance in space. There are thought to be vast reserves of the isotope helium-3 trapped just under the surface of the moon with a realistic potential for mining.
Its value as a nuclear power source pitches it at $3 billion per tonne, and even relatively small amounts shipped back to Earth could power entire countries year-round.
Combine the potential of lunar mining and nuclear fusion reactors and what have you got? An end to humanity's reliance on non-renewable fossil fuels and protection for life on Earth from continued shifts in the global climate.
Such a transition is not only worth trillions in economic terms, but will pave the way for the next industrial and political superpower.
The helium rush is on.
How Helium is Created
The universe is predominantly made up of hydrogen and helium as a result of the nuclear fusion that takes place inside stars.
As the two lightest elements, they are the building blocks of all heavier elements, which are simply an accumulation of more and more protons, neutrons and electrons.
Hydrogen, the most common element in the universe, makes up most of the stars in the night sky and of course our very own sun. It's usually composed of one proton and one electron (and zero neutrons; see my article Atoms 101 if you have no idea what I'm talking about).
Stars are hot. Really hot. And this energy has all the hydrogen atoms shooting around - with the eventual outcome of colliding into one another. Usually when this happens, they break apart.
However, sometimes the collision simply causes one proton to lose its positive charge and convert to a neutron, thanks to the weak nuclear force.
The result is an atom of deuterium: a stable isotope of hydrogen with one proton, one neutron and one electron. The collision also releases energy, ensuring stars stay hot, just as we puny humans like it.
But we still don't have helium yet, so how is helium created? Picture the hydrogen atoms and deuterium isotopes whizzing around inside the star (see below).
Eventually these collide too, giving us an isotope of helium-3 (by adding another proton to deuterium).
Finally, when two atoms of helium-3 smack together, we get an atom of helium-4, plus a couple of hydrogen atoms as a nice bonus.
Hundreds of billions of stars are doing this in every galaxy, which is why there is simply a lot of helium hanging around in the cosmos. Not only is it rife inside stars, but it's also ejected on a massive scale and dispersed by solar winds, which is how it ends up in excess on the moon. A lot more about this later.
Earth's magnetosphere protects us from solar winds and the accompanying helium bombardment. However, the gas is created in small quantities on Earth through a separate process in rock.
Helium is emitted as alpha particles (which Ernest Rutherford established are essentially helium nuclei - just add electrons) from the radioactive decay of heavy elements such as uranium, thorium and radium.
This process of decay, however, takes billions of years which is what makes helium such a finite resource on our planet.
The resulting helium pockets in the Earth's crust can be mined by humans, or when formed in the upper mantle, can be released by volcanic activity and lost into the atmosphere.
The helium in our atmosphere amounts to five-millionths or 0.000005% of it, to be precise. However its lightness means it escapes from our gravity with ease, so each time we deploy the stuff in party balloons or industrial applications, a little more is permanently lost to space.
You can't normally see, smell or taste helium, but it does glow in an electric field.
The Discovery of Helium
Helium was discovered in stars back in the 1800s with the use of a spectrometer. This is a tool which diffracts light, enabling the observer to measure the optical properties of any substance, near or distant.
A spectrometer exploits the fact that electrons have specific energies which differ according to their orbital. When an electron relaxes to a lower orbital it emits light which shows up as an emission spectrum.
Conversely, when an electron is excited to a higher orbital it absorbs light which shows up on the absorption spectrum.
As you can see below, different elements have different optical fingerprints, allowing us to identify them even from vast distances across space.
Prior to 1868, astronomers observed the sun during an eclipse and saw the spectral fingerprint of hydrogen, as well as a second unknown element, assumed to be sodium.
When the French astronomer, Pierre Janssen, made his own observations during an eclipse in India, he found the yellow line didn't match up with the wavelength of sodium. He went ahead an invented the spectrohelioscope, allowing him to take repeat measurements without the need for an eclipse, and confirmed the spectral fingerprint of helium - not sodium - coming from the sun.
In the same year in England, the astronomer Joseph Lockyer was working on the very same incongruity, and came to the same conclusion that the second solar element was helium.
It was a complete fluke that their letters, which stated identical findings, reached the French Academy of Sciences within a couple of hours of each other.
The previously unknown (and allegedly purely extraterrestrial element) they discovered was named helium, after the Greek god of the sun, Helios.
Fellow scientists showed a healthy scepticism about the findings and gave Lockyer and Janssen a hard time about it. But by 1881, the mysterious element helium was discovered in lava thrown up by an erupting Mount Vesuvius and the scientists hurriedly moved on with their day.
Helium's Current Applications
Helium is mined from the Earth's crust for a range of applications.
It's lighter than air which makes it ideal for inflating air ships, blimps and balloons. This gives it a reputation for fun and games, however huffing on helium gas is ill-advised as it can cut off the oxygen supply to the brain, cause embolisms, and burst the lungs, causing haemorrhage (especially if taken direct from a pressurised tank).
Why does helium make your voice go high? Helium molecules have less mass than the oxygen and nitrogen found in the air, so sound waves can travel through them three times as fast. The sped-up frequency gives you the adorable voice of a chipmunk. The opposite effect can be produced by inhaling sulphur hexachloride which is denser than air.
A mixture of 8:2 helium and oxygen is used in the air tanks of deep sea divers and for people working under pressurised conditions. Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. And the Large Hadron Collider in Switzerland uses helium to cool and strengthen its electromagnets to -271°C; these magnets keep the beams of particles on track as they race around the collision course at close to the speed of light.
A new use for helium is a helium-ion microscope (HIM) that gives better image resolution than even a scanning electron microscope (SEM).
It's also valuable as a recyclable cooling agent for super-magnets in MRI machines, and is used in space programs to displace liquid fuel in rocket tanks.
However, as a non-renewable resource we're due to run out of helium on Earth in the next two decades, and many of its medical and industrial applications have no viable alternatives.
Above: Comparison images of a 3D-fibrin matrix. For SEM, the fibrin matrix was coated with gold particles. In contrast for HIM imaging, no coating is necessary.
But here's the bright side. An estimated 25% of the universe is composed of helium, with around 1.1 million tonnes in shallow pockets just under the surface of the moon.
Unlike Earth, the moon lacks a protective magnetic field and has been bombarded with helium-3 solar winds for billions of years.
With the sufficient investment, many scientists believe we could tap into the vast quantities of extra-terrestrial helium for use on Earth... as well as our not-so-distant colonisation of other planets.
Of all the elements, helium has the lowest boiling point of -269°C. Cooled a little more, liquid helium will climb the sides of a container and remain unmoving in a spinning container. It freezes at -272°C but requires 50,000 times the air pressure in your car tyres to do so.
Helium as an Energy Source
The real value of abundant helium is as a source of nuclear power.
Today, all commercial nuclear power plants use nuclear fission to split heavy isotopes like uranium or plutonium, which generates heat to be turned into electricity.
However, nuclear fission comes with its drawbacks: accidents like those at Three Mile Island (1979), Chernobyl (1986) and Fukushima (2011) reveal the serious and long term dangers of accidentally releasing large amounts of radiation into the environment.
The heavy elements required in nuclear fission are finite and non-renewable, and produce radioactive nuclear waste as a by-product. This is not a sustainable source of energy for humanity.
The dream of nuclear fusion has far greater appeal and is a serious area of research among many nations, some of which have banded together for an international solution.
As opposed to splitting heavy atoms, fusion combines light atoms in high energy collisions, releasing large amounts of energy as a result. Not only is it more efficient than fission, but it's sustainable and produces virtually no waste.
Most nuclear research is geared toward the fusion of hydrogen isotopes (namely deuterium and radioactive tritium) with the former being abundant in water and the latter produced by the neutron bombardment of lithium.
However, there is a cost to supply and the issue of radioactivity (albeit much less than the heavy radioactive isotopes of nuclear fission). The nuclear fusion scenario becomes even more attractive when you bring the light and non-radioactive isotope, helium-3, to the table.
The problems with the fusion of helium are two-fold.
First, getting two protons to fuse together (regardless of whether you're using hydrogen or helium isotopes) takes an awful lot of energy in the first place. It happens easily inside stars but then they are giant balls of gas burning at millions of degrees Celsius.
But physicists are making astonishing advances on this front.
In 2016, Germany switched on its Wendelstein 7-X stellarator for the first time, creating temperatures up to 80,000,000°C to generate hydrogen plasma. Further development is ongoing to create an environment for higher temperatures and longer discharges, to reach the goal of net power generation, making nuclear fusion a reality.
In 2017, construction of the multi-billion-dollar International Thermonuclear Experimental Reactor (ITER) in France reached the halfway point, on track for completion in 2025. ITER is a partnership of 35 countries which promises to be the first fusion device to create net energy.
The race is on.
Above: The International Thermonuclear Experimental Reactor (ITER) Nuclear Fusion Reactor
It's looking like nuclear fusion reactors are no longer an impossible dream. Now the only problem with the helium energy plan is sourcing the actual helium.
As we've seen, helium exists in massive quantities on the moon thanks to the helium-3-rich solar winds. The gas is laid down in the top few metres of the moon's surface, making it a relatively easy mining operation, if you overlook the bit about it taking place on the moon.
The helium could be extracted by heating the lunar dust to 600°C before bringing it back to Earth.
If achieved, experts reckon the lunar deposits alone could power the entire Earth for the next 200 years.
A fully-loaded space shuttle could carry 25 tonnes of helium, and could power the entire US for a year. This gives it a value of $3 billion per tonne and makes that whole moon-mining escapade look pretty appealing in economic terms, if not logistical ones.
And this is why helium could be our saviour. Granted, there are obstacles we need to overcome. But nothing worth having is necessarily easy.
China's Lunar Exploration Program, called Chang'e, will send astronauts to the moon by the early 2020s, which I don't need to remind you is only two years from now and not at all as distant as it sounds.
Chang'e will explore for rich helium-3 deposits and create a sustained human outpost for mining operations. Having a monopoly on such a resource would give China economic supremacy.
Now the helium rush is on. Russian, American and Indian scientists have urged the mining of the moon for helium-3, and numerous governments have teased the idea in the past, although with little actual progress to date. Perhaps the idea is simply too ambitious to attract serious funding given the incomplete status of nuclear fusion research.
Nonetheless, as debates on peak oil, resource depletion and climate change rage on, there has never been more urgency to find abundant clean energy sources. | 0.832853 | 3.359208 |
Moon* ♍ Virgo
Moon phase on 9 September 2075 Monday is Waning Crescent, 28 days old Moon is in Virgo.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 7 days on 2 September 2075 at 08:34.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠6° of ♍ Virgo tropical zodiac sector.
Lunar disc appears visually 5.2% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1809" and ∠1905".
Next Full Moon is the Harvest Moon of September 2075 after 14 days on 24 September 2075 at 10:31.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 28 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 935 of Meeus index or 1888 from Brown series.
Length of current 935 lunation is 29 days, 13 hours and 52 minutes. It is 1 hour and 11 minutes longer than next lunation 936 length.
Length of current synodic month is 1 hour and 8 minutes longer than the mean length of synodic month, but it is still 5 hours and 55 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠218.9°. At the beginning of next synodic month true anomaly will be ∠251.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of apogee on 4 September 2075 at 19:44 in ♋ Cancer. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 10 days, until it get to the point of next perigee on 20 September 2075 at 11:42 in ♒ Aquarius.
Moon is 396 326 km (246 266 mi) away from Earth on this date. Moon moves closer next 10 days until perigee, when Earth-Moon distance will reach 367 790 km (228 534 mi).
4 days after its ascending node on 5 September 2075 at 03:09 in ♋ Cancer, the Moon is following the northern part of its orbit for the next 9 days, until it will cross the ecliptic from North to South in descending node on 18 September 2075 at 19:47 in ♑ Capricorn.
4 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the beginning to the first part of it.
4 days after previous North standstill on 5 September 2075 at 01:11 in ♋ Cancer, when Moon has reached northern declination of ∠22.823°. Next 9 days the lunar orbit moves southward to face South declination of ∠-22.947° in the next southern standstill on 18 September 2075 at 20:04 in ♑ Capricorn.
After 1 day on 10 September 2075 at 11:02 in ♍ Virgo, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.071823 |
As NASA missions explore our solar system and search for new worlds, they are finding water in surprising places. Water is but one piece of our search for habitable planets and life beyond Earth, yet it links many seemingly unrelated worlds in surprising ways.
"NASA science activities have provided a wave of amazing findings related to water in recent years that inspire us to continue investigating our origins and the fascinating possibilities for other worlds, and life, in the universe," said Ellen Stofan, chief scientist for the agency. "In our lifetime, we may very well finally answer whether we are alone in the solar system and beyond."
The chemical elements in water, hydrogen and oxygen, are some of the most abundant elements in the universe. Astronomers see the signature of water in giant molecular clouds between the stars, in disks of material that represent newborn planetary systems, and in the atmospheres of giant planets orbiting other stars.
There are several worlds thought to possess liquid water beneath their surfaces, and many more that have water in the form of ice or vapor. Water is found in primitive bodies like comets and asteroids, and dwarf planets like Ceres. The atmospheres and interiors of the four giant planets -- Jupiter, Saturn, Uranus and Neptune -- are thought to contain enormous quantities of the wet stuff, and their moons and rings have substantial water ice.
Perhaps the most surprising water worlds are the five icy moons of Jupiter and Saturn that show strong evidence of oceans beneath their surfaces: Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn.
Scientists using NASA's Hubble Space Telescope recently provided powerful evidence that Ganymede has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice.
Europa and Enceladus are thought to have an ocean of liquid water beneath their surface in contact with mineral-rich rock, and may have the three ingredients needed for life as we know it: liquid water, essential chemical elements for biological processes, and sources of energy that could be used by living things. NASA's Cassini mission has revealed Enceladus as an active world of icy geysers. Recent research suggests it may have hydrothermal activity on its ocean floor, an environment potentially suitable for living organisms.
NASA spacecraft have also found signs of water in permanently shadowed craters on Mercury and our moon, which hold a record of icy impacts across the ages like cryogenic keepsakes.
While our solar system may seem drenched in some places, others seem to have lost large amounts of water.
On Mars, NASA spacecraft have found clear evidence that the Red Planet had water on its surface for long periods in the distant past. NASA's Curiosity Mars Rover discovered an ancient streambed that existed amidst conditions favorable for life as we know it.
More recently, NASA scientists using ground-based telescopes were able to estimate the amount of water Mars has lost over the eons. They concluded the planet once had enough liquid water to form an ocean occupying almost half of Mars' northern hemisphere, in some regions reaching depths greater than a mile (1.6 kilometers). But where did the water go?
It's clear some of it is in the Martian polar ice caps and below the surface. We also think much of Mars' early atmosphere was stripped away by the wind of charged particles that streams from the sun, causing the planet to dry out. NASA's MAVEN mission is hard at work following this lead from its orbit around Mars.
The story of how Mars dried out is intimately connected to how the Red Planet's atmosphere interacts with the solar wind. Data from the agency's solar missions -- including STEREO, Solar Dynamics Observatory and the planned Solar Probe Plus -- are vital to helping us better understand what happened.
Understanding the distribution of water in our solar system tells us a great deal about how the planets, moons, comets and other bodies formed 4.5 billion years ago from the disk of gas and dust that surrounded our sun. The space closer to the sun was hotter and drier than the space farther from the sun, which was cold enough for water to condense. The dividing line, called the "frost line," sat around Jupiter's present-day orbit. Even today, this is the approximate distance from the sun at which the ice on most comets begins to melt and become "active." Their brilliant spray releases water ice, vapor, dust and other chemicals, which are thought to form the bedrock of most worlds of the frigid outer solar system.
Scientists think it was too hot in the solar system's early days for water to condense into liquid or ice on the inner planets, so it had to be delivered -- possibly by comets and water-bearing asteroids. NASA's Dawn mission is currently studying Ceres, which is the largest body in the asteroid belt between Mars and Jupiter. Researchers think Ceres might have a water-rich composition similar to some of the bodies that brought water to the three rocky, inner planets, including Earth.
The amount of water in the giant planet Jupiter holds a critical missing piece to the puzzle of our solar system's formation. Jupiter was likely the first planet to form, and it contains most of the material that wasn't incorporated into the sun. The leading theories about its formation rest on the amount of water the planet soaked up. To help solve this mystery, NASA's Juno mission will measure this important quantity beginning in mid-2016.
Looking further afield, observing other planetary systems as they form is like getting a glimpse of our own solar system's baby pictures, and water is a big part of that story. For example, NASA's Spitzer Space Telescope has observed signs of a hail of water-rich comets raining down on a young solar system, much like the bombardment planets in our solar system endured in their youth.
With the study of exoplanets -- planets that orbit other stars -- we are closer than ever to finding out if other water-rich worlds like ours exist. In fact, our basic concept of what makes planets suitable for life is closely tied to water: Every star has a habitable zone, or a range of distances around it in which temperatures are neither too hot nor too cold for liquid water to exist. NASA's planet-hunting Kepler mission was designed with this in mind. Kepler looks for planets in the habitable zone around many types of stars.
Recently verifying its thousandth exoplanet, Kepler data confirm that the most common planet sizes are worlds just slightly larger than Earth. Astronomers think many of those worlds could be entirely covered by deep oceans. Kepler's successor, K2, continues to watch for dips in starlight to uncover new worlds.
The agency's upcoming TESS mission will search nearby, bright stars in the solar neighborhood for Earth- and super-Earth-sized exoplanets. Some of the planets TESS discovers may have water, and NASA's next great space observatory, the James Webb Space Telescope, will examine the atmospheres of those special worlds in great detail.
It's easy to forget that the story of Earth's water, from gentle rains to raging rivers, is intimately connected to the larger story of our solar system and beyond. But our water came from somewhere -- every world in our solar system got its water from the same shared source. So it's worth considering that the next glass of water you drink could easily have been part of a comet, or an ocean moon, or a long-vanished sea on the surface of Mars. And note that the night sky may be full of exoplanets formed by similar processes to our home world, where gentle waves wash against the shores of alien seas.
For more information about NASA's exploration of the solar system and beyond, visit:
Jet Propulsion Laboratory, Pasadena, Calif.
NASA Headquarters, Washington | 0.891289 | 3.867268 |
New observations from NASA’s Spitzer Space Telescope indicate that the nearest planetary system to our own has two asteroid belts. Our own solar system has just one.
The star at the center of the nearby system, called Epsilon Eridani, is a younger, slightly cooler and fainter version of the sun. Previously, astronomers had uncovered evidence for two possible planets in the system, and for a broad, outer ring of icy comets similar to our own Kuiper Belt.
Now, Spitzer has discovered that the system also has dual asteroid belts. One sits at approximately the same position as the one in our solar system. The second, denser belt, most likely also populated by asteroids, lies between the first belt and the comet ring. The presence of the asteroid belts implies additional planets in the Epsilon Eridani system.
“This system probably looks a lot like ours did when life first took root on Earth,” said Dana Backman, an astronomer at the SETI Institute, in Mountain View, Calif., and outreach director for NASA’s Sofia mission. “The main difference we know of so far is that it has an additional ring of leftover planet construction material.” Backman is lead author of a paper about the findings to appear Jan. 10 in the Astrophysical Journal.
Asteroid belts are rocky and metallic debris left over from the early stages of planet formation. Their presence around other stars signals that rocky planets like Earth could be orbiting in the system’s inner regions, with massive gas planets circling near the belts’ rims. In our own solar system, for example, there is evidence that Jupiter, which lies just beyond our asteroid belt, caused the asteroid belt to form long ago by stirring up material that would have otherwise coalesced into a planet. Nowadays, Jupiter helps keep our asteroid belt confined to a ring.
Astronomers have detected stars with signs of multiple belts of material before, but Epsilon Eridani is closer to Earth and more like our sun overall. It is 10 light-years away, slightly less massive than the sun, and roughly 800 million years old, or one-fifth the age of the sun.
Because the star is so close and similar to the sun, it is a popular locale in science fiction. The television series Star Trek and Babylon 5 referenced Epsilon Eridani, and it has been featured in novels by Issac Asimov and Frank Herbert, among others.
The popular star was also one of the first to be searched for signs of advanced alien civilizations using radio telescopes in 1960. At that time, astronomers did not know of the star’s young age.
Spitzer observed Epsilon Eridani with both of its infrared cameras and its infrared spectrometer. When asteroid and comets collide or evaporate, they release tiny particles of dust that give off heat, which Spitzer can see. “Because the system is so close to us, Spitzer can really pick out details in the dust, giving us a good look at the system’s architecture,” said co-author Karl Stapelfeldt of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
The asteroid belts detected by Spitzer orbit at distances of approximately 3 and 20 astronomical units from the star (an astronomical unit is the average distance between Earth and the sun). For reference, our own asteroid belt lies at about 3 astronomical units from the sun, and Uranus is roughly 19 astronomical units away.
One of the two possible planets previously identified around Epsilon Eridani, called Epsilon Eridani b, was discovered in 2000. The planet is thought to orbit at an average distance of 3.4 astronomical units from the star — just outside the innermost asteroid belt identified by Spitzer. This is the first time that an asteroid belt and a planet beyond our solar system have been found in a similar arrangement as our asteroid belt and Jupiter.
Some researchers had reported that Epsilon Eridani b orbits in an exaggerated ellipse ranging between 1 and 5 astronomical units, but this means the planet would cross, and quickly disrupt, the newfound asteroid belt. Instead, Backman and colleagues argue that this planet must have a more circular orbit that keeps it just outside the belt.
The other candidate planet was first proposed in 1998 to explain lumpiness observed in the star’s outer comet ring. It is thought to lie near the inner edge of the ring, which orbits between 35 and 90 astronomical units from Epsilon Eridani.
The intermediate belt detected by Spitzer suggests that a third planet could be responsible for creating and shepherding its material. This planet would orbit at approximately 20 astronomical units and lie between the other two planets. “Detailed studies of the dust belts in other planetary systems are telling us a great deal about their complex structure,” said Michael Werner, co-author of the study and project scientist for Spitzer at JPL. “It seems that no two planetary systems are alike.”
Jet Propulsion Laboratory | 0.853231 | 3.861474 |
If I was to pick a single characteristic of daily (academic) life that never ceases to amaze, it would be the rate at which time flies. It has been a little over six months since the publication of the original P9 paper, and the number of follow-up studies that have been unveiled since then edge on thirty. A subset of these studies have, rather than attempting to further characterize Planet Nine’s present-day state, considered the intriguing question of Planet Nine’s origins. Having finished teaching a class on the formation and evolution of planetary systems last quarter, this question has been on my mind as well.
In essence, there are three potential scenarios for the formation of Planet Nine that have been discussed in the literature. They are (I) outward scattering (II) external capture and (III) in-situ formation. Within the framework of the first picture, P9 forms alongside other solar system planets, but is perturbed onto a highly elliptical, long-period orbit after the dissipation of the solar nebula. In other words, the extreme orbit of Planet Nine is generated through the honest labor of gravitational planet-planet interactions (with a bit of work done at the end by passing stars; see below).
|Orbit of an outward-scattered planet. Made with Super Planet Crash (http://www.stefanom.org/spc/).|
External capture, on the other hand, paints the solar system in a more conniving light. In this story, Planet Nine is kidnapped by the Sun’s gravitational pull from an unsuspecting passing star, rendering P9 a bonafide exoplanet. Finally, the in-situ formation scenario simply envisions that the solar system’s protoplanetary disk extended to ~1000AU, and over time a distant annulus of material coalesced into a ~10 Earth mass body.
Although I’m a fan of the theory of in-situ formation of giant planets in the inner nebula, in-situ formation of P9 seems to be the least likely of the three aforementioned alternatives. If we extend the classical minimum mass solar nebula to ~1000AU with a Mestel-like surface density profile, we obtain a disk mass of Mdisk ~ (2 pi) (1700 g/cm^2) (1AU) (1000AU) ~ 1.2 solar masses. In addition to being straight-up gnarly, such a disk severely violates the gravitational stability criterion, and with its sub-Jovian mass, P9 is probably not a product of direct gravitational collapse.
So if P9 didn’t form in place, it was either scattered outwards or it was stolen. Interestingly, both of these processes require the solar system to be embedded within its birth cluster to operate successfully. This is because in the capture scenario, a dense stellar environment is necessary for stars to get close enough to exchange planets, and in the outward scattering scenario, perturbations from passing stars are needed to lift Planet Nine’s perihelion from q ~ 5AU (i.e. Jupiter’s orbit) to its present-day value of q ~ 250 AU.
|The solar system embedded within a very dense birth cluster (a snapshot from a movie created by A. M. Geller http://faculty.wcas.northwestern.edu/aaron-geller/visuals.php)|
The dynamics of interactions between Planet Nine and passing stars were addressed in a paper by Li & Adams. In short, Li & Adams find that external capture (despite being dramatic and esthetically satisfying) is a fundamentally low-probability event: capture cross-sections are much smaller than ejection cross-sections in the birth cluster. Thus, the capture scenario can likely be ruled out on probabilistic grounds.
Intriguingly, the outward scattering story (the only remaining option) is not immune to external kicks either. If left alone in the birth cluster for ~100 million years, the same gravitational perturbations from passing stars that act to lift P9’s perihelion can also strip the planet away all together. Although the exact limits depend on detailed parameter choices, these calculations imply a particular timing for the successful generation and retention of Planet Nine. Specifically, Planet Nine probably formed within the first 1-10 million years of the solar system’s lifetime and acquired its orbit a few 10s of millions of years later, towards the end of the birth cluster’s lifetime.
From here, we can speculate a bit. On one hand, this timing seems inconsistent with early scattering as envisioned for example by Izidoro et al (2015), because any objects acquiring long-period orbits while the gas is still present would be stripped away by passing stars. But the nebular epoch is not the only time when the solar system could have conceivably ejected planets. The other reasonable instance is the era of transient dynamical instability associated with the Nice model. After all, N-body modeling shows that the solar system could have harbored an additional ice giant that would have been expelled at this time (see here, here and here). To this end, here is a simulation that starts out with an extra Neptune that ejects after about ten million years.
|Dynamical evolution of an initially 5-planet outer solar system (from Batygin et al 2012)|
If we subscribe to this point of view, then Planet Nine is the solar system’s original fifth giant planet. Pretty neat. But wait - by fixing the onset of giant planet instability to sometime before ~100 million years after the Sun’s birth, we have broken an attractive feature of the Nice model: the late heavy bombardment. The large-scale instability represents a natural trigger for the avalanche of debris that scarred our Moon’s surface, and this very notion served as the main motivation for rethinking how the instability gets activated in the first place. Bummer.
Now, terrestrial planets themselves require ~100 million years to form (seriously, why couldn’t all these timescales be a little more distinct from one another?!!), so in order to bombard the Moon, the instability would have had to happen after that. Moreover, a recent analysis linked Mercury’s weirdly excited orbit to a sweeping secular resonance that is associated with changes in system’s architecture during the dynamical reformation. But at the same time, another study that came out earlier this year pointed out that the terrestrial planets are unlikely to survive the Nice-model instability in the first place. So perhaps the fact that we exist to even ask these questions is evidence in itself that the instability proceeded before the formation of the terrestrial planets was complete?
At this point, my head is spinning and I want to stop speculating. With Planet Nine in the mix, the solar system’s origin story has once again began to resemble a jig-saw puzzle with pieces that don’t quite snap into place perfectly. But this is probably due to the fact that the piece that represents P9 has not yet been directly imaged, and one can only speculate as to what kind of additional constraints on the solar system’s early evolution will come to light once Planet Nine’s physical and orbital properties are revealed. But like I said, for now I want to stop speculating. | 0.878269 | 3.805182 |
- The brains of astronauts show permanent changes to volume even after returning to Earth, a new study suggests.
- Space station travelers had brain scans before and after their trips to space, and the changes in brain volume were noticeable.
- Researchers still aren’t sure how these changes may affect the astronauts over the long term.
- Visit BGR’s homepage for more stories.
It’s easy to imagine a future where humans travel freely through space, visiting places like the Moon and Mars to carry out research or perhaps even set up colonies. There are many technological hurdles to scale before such a future is even remotely possible, but what about the biological impacts on our own bodies? Scientists aimed to answer some of those questions, and a new paper published in Radiology reveals one very interesting effect of long-term spaceflight: Human brains get physically bigger.
The research has led to some very important questions about how well-suited humans are for space travel, and what kind of long-term effects travelers to the Moon, Mars, and beyond, may experience.
For the study, researchers performed MRI brain scans on 11 astronauts before they spent time on the International Space Station. After returning, the astronauts were once again scanned, and the before-and-after images were compared.
Because the International Space Station is in orbit around Earth, the gravity acting on its inhabitants is minimal. Scientists have been studying the effects of microgravity on the human body for a long time, and we know that blood flow is dramatically affected. Without gravity acting on a person’s body, organs experience changes too, and that includes the brain.
Research has shown that areas of the brains of astronauts physically expand in space. The changes aren’t dramatic, but they are measurable, and the lack of gravity is likely to blame.
“When you’re in microgravity, fluid such as your venous blood no longer pools toward your lower extremities but redistributes headward,” Dr. Larry A. Kramer, lead author of the study, said in a statement. “That movement of fluid toward your head may be one of the mechanisms causing changes we are observing in the eye and intracranial compartment.”
In this new round of research, scientists wanted to know how long this effect lasts after the astronauts returned to Earth. With the normal amount of gravity acting on their bodies, would the changes in the brain be reversed?
It doesn’t appear so. Even a full year after returning to Earth, the brains of the astronauts involved in the study remained at their postflight size, suggesting that the changes may be permanent.
It’s still unclear exactly what this means for the astronauts and future space travelers. The researchers noted changes in the shape of the pituitary gland which they attributed to the increased pressure in the brain cavity. Changes to the flow of cerebrospinal fluid were also noted, though the astronauts don’t report symptoms and would seem to be healthy.
NASA and other space agencies are working on ways to mitigate the physical effects of spaceflight on the human body, and these new techniques will be increasingly important if we hope to send humans on long-distance missions in our solar system. | 0.825618 | 3.197021 |
An orbit is the gravitationally curved path of an object around a point in space. The current understanding of orbital motion is from Albert Einstein’s general theory of relativity. This accounts for gravity due to curvature of space-time which orbits following geodesics.
There are some common ways to understand orbits:
- As objects move sideways, it falls toward the central body. However, it moves so quickly that the central body will curve away beneath it.
- A force, like gravity, pulls the object into a curved path as it attempts to fly off in a straight line.
- As the object moves tangentially, it falls toward the central body. However, it has enough tangential velocity to miss the orbited object and will continue falling indefinitely.
Our solar system there is many things which orbit the Sun, planets, dwarf planets, asteroids, comets and space debris. The Sun is called the barycenter in elliptical orbits. Some bodies, such as comets, are not gravitationally bound to the star and therefore are not considered part of the star’s planetary system.© BrainMass Inc. brainmass.com May 29, 2020, 10:10 am ad1c9bdddf | 0.864551 | 3.066682 |
Ewine van Dishoeck wins Kavli prize for astrophysics
How are stars and planets formed? Is life outside Earth possible? These questions are being researched by Professor of Molecular Astrophysics Ewine van Dishoeck at Leiden University. Her pioneering work has earned her the Kavli prize in the category of astrophysics. The prize consists of 1,000,000 dollars and a gold medal. The announcement was made today by the Norwegian Academy of Sciences and Arts.
Ewine Van Dishoeck makes a significant contribution, based on observations, theory and experiments, to the knowledge of so-called interstellar clouds, large gas and dust clouds that are the birthplace of planets and stars. She shows how molecules arise in these interstellar clouds that evolve further and clump together to form building blocks for complete planetary systems such as our own solar system.
Van Dishoeck's research is highly important in determining whether life is possible on other planets. To assess the likelihood of extraterrestrial life, we first need to know which molecules are present in such a cloud, and how they react with one another. That way you can determine which organic compounds can occur on a planet under formation and whether life can be created from them. Van Dishoeck has also conducted research on another building block for life: water. She studies water reservoirs in the precursors of planetary systems and the water vapour around young stars. Her research generates information on the origin of water on Earth.
Are we alone?
‘I'm still speechless after that unexpected telephone call from the President of the Norwegian Academy. What a fantastic honour, not only for me, but also for all my young researchers and colleagues spread throughout the world,' Van Dishoek commented. 'It is at least in part thanks to their creativity and hard work that our field is now in the Champions League of astronomy.'
‘It is not only about pure science, but also about the fact that we can deliver a contribution to one of the biggest questions that mankind can ask: are we alone in the universe?'
‘Her research has changed just about every aspect of astronomy'
The Kavli prize – that was first awarded in 2008 – is always awarded to scientists who expand 'our understanding of existence'. 'Van Dishoeck's research has changed just about every apect of astronomy,' jury member Robert Kennicutt commented. ‘Her specialist field was at one time no more than a small research area on the periphery of astrophysics, but thanks to her it is now a core theme within the totality of astronomy.'
Van Dishoeck has already won a number of important prizes and awards, including the Spinoza Prize, the top science prize in the Netherlands. She has also received an ERC Advanced Grant. In 2012 she was appointed as an Academy professor by the Royal Netherlands Academy of Arts and Sciences (KNAW). Van Dishoeck is currently President Elect of the International Astronomical Union (IAU).
About the Kavli prize
The Kavli prize is awarded every two years by the Norwegian Academy of Sciences and Arts to winners in three categories: astrophysics, nanosciences and neurosciences. The winners in each category receive a financial award of a million dollars and a gold medal. The award ceremony will take place on 4 September in Oslo, where the prize will be presented by King Harald V of Norway.
Want to know more about Van Dishoeck?
You can get to know Van Dishoeck and her specialist research field in our research dossier on exploring the galaxy. If you would like to hear Van Dishoeck speak live, come to the Museum Night on Saturday 2 June, when she will be explaining how water occurred on Earth. | 0.815171 | 3.131728 |
Comets or Aliens?
Let’s deal with the big question first. Has Planet Hunters discovered aliens?
The answer is no. But that doesn’t mean that all of the press who have written about us in the last 48 hours, sending a flood of volunteers to the site, are completely misguided. Let me backtrack…
A few weeks ago we submitted the ninth planet hunters paper to the journal, and that paper is now available on the arXiv service. Led by Tabetha Boyajian at Yale, it describes a rather unusual system (what the Atlantic called the most interesting star in the Galaxy), which was identified by Planet Hunters, four of whom (Daryll, Kian, Abe, Sam) are named on the paper*. They spotted a series of transits – which is normally what signifies the presence of a planet – but these were unusual.
The star’s light dimmed for a long period of time, loosing a fifth of its brightness for days or even months at a time. More mysteriously, the duration of the dips was not always the same, so this couldn’t possibly be a planet. This behaviour is unique amongst the more than a hundred thousand stars studied by Kepler – we have a bone fide mystery on our hands.I think the team’s immediate thoughts were that it must be the star itself that’s misbehaving, but stars aren’t known to behave like this and some careful follow up reveals it to be nothing more than a normal F-type star, slightly hotter and more massive than the Sun. So it’s not the star, and we’re sure too that it’s not Kepler itself misbehaving; something is really blocking the light from this star.One option is a disk of dust around the star. It’s from such disks that planets form (see DiskDetectives.org for more on this!) and so that wouldn’t be too surprising. Yet enough dust to cause the deep eclipses we see would glow brightly in the infrared, and there’s no sign of a strong infrared source around this star.
You can read the paper to find out what else we considered, but we think the best explanation is that there is a group of exocomets in orbit around the star. Comets are an appealing scenario to invoke because they would be faint in the infrared, and because they move on elliptical orbits, accounting for the random timing of the transits and their different lengths. Such a group of comets could have come from the breakup of a larger object, leaving a cloud of smaller remnants in similar orbits behind.
Much detailed work is needed to flesh out the details of this (pleasingly outlandish!) scenario. One possibility is that the recent passage of a nearby star triggered the cometary bombardment whose effects we’re seeing. The paper is currently in the peer review process and there is – of course – the possibility that there is a perfectly sensible solution we haven’t yet considered. However, so far over 100 professional scientists have had a look at the lightcurves and not managed to come up with a working solution.
One other proposed theory is that this pattern of behaviour is due to a fleet of alien spaceships in orbit around a star, a possibility considered by Jason Wright and collaborators here. Jason and co were tipped off about our discovery by the team, and it’s included in their paper as an object with ‘a bizarre light curve consistent with a “swarm” of megastructures’, much to the excitement of much of the internet. ‘Consistent with’ isn’t the same as ‘definitely is’, of course – and personally, my money is very firmly on the comet theory with a side bet on weird stellar behaviour – but until those models are properly investigated alien spaceships remain a possibility. The Wright paper points out this star is now a supremely interesting target for SETI (the search for extraterrestrial intelligence), and we agree – I hope radio astronomers will go and listen for signals. We need more observations of transits in action, too, and will be trying to follow-up to try and work out what’s actually going on.In the meantime, who knows what else is lurking in the Kepler data? Planet Hunters is about finding planets, but this ability to identify the weird and unusual is one of the project’s great advantages. Get clicking at www.planethunters.org, and let us know through Talk if you find anything a little odd.
* – This isn’t the final version of the paper, and we have more names to mention too before we’re done. | 0.872341 | 3.636894 |
The top panel shows the calculated electron flux, colour coded as a function of time and L*. The dashed white line shows the location of the GOES satellite at geosynchronous orbit. The solid white line shows the location of the outer boundary of the geomagnetic field.
The second panel shows a comparison between the model and the observations by GOES (for integrated electron flux only).
The third panel shows the >10 MeV proton flux. GOES electron data are unreliable when the proton flux exceeds the red line.
The fourth panel shows the solar wind velocity in red and the z component of the interplanetary magnetic field in black. Fast solar wind usually ‘pumps up’ the radiation belts. When IMF Bz is negative energy is transferred from the solar wind into the geomagnetic field.
The fifth panel shows the Dst index, colour coded, which is a measure of geomagnetic storms, and the solar wind dynamic pressure. Strong pressure usually pushes the outer boundary of the magnetic field inwards.
The bottom panel shows the Kp index, colour coded, and the AE index. Kp is a measure of geomagnetic activity and AE is a measure of substorm electron injections.
Internal charging: High energy electrons can penetrate the outer layers of a satellite and accumulate in insulators such as cables and dielectrics on circuit boards. If the charge builds up faster than it can leak away it can cause an electrostatic discharge and break down the material permanently. This has led to loss of service and in some cases total satellite loss. The periods most at risk correspond to periods of high electron flux.
Surface charging: Bursts of low energy electrons can accumulate on surfaces, particularly when the spacecraft is in the Earth’s shadow and there is no photoelectron emission. Since only half the spacecraft can ever be in sunlight large electric fields can build up across the satellite and cause an electrostatic discharge. Surface charging has led to loss of solar array strings. The periods most at risk correspond to periods of substorm injections when the satellite is in eclipse.
Single event upsets: High energy ions can penetrate electronic components and deposit charge in them. This can corrupt memory circuits. High energy ions can also dislodge ions in the crystal structure causing increased noise and degradation of performance. Periods most at risk are during solar energetic particle events when the number of high energy protons can increase a thousand fold. This has led to repeated memory corruption over a period of a few days and up to 2% loss of solar array power.
The BAS radiation belt model is used to provide a forecast of the 2 MeV electron flux in the outer Van Allen radiation belt. The model uses data from the ACE satellite and a forecast of geomagnetic activity to make the forecasts. The model solves a diffusion equation that takes into account the transport of electrons across the magnetic field towards and away from the planet (radial diffusion), electron acceleration by wave-particle interactions, electron loss into the atmosphere by wave-particle interactions and collisions with atmospheric gasses. Changes in the interplanetary magnetic field and the solar wind dynamic pressure are used to determine the outer boundary of the Earth’s magnetic field which affects radial transport. The injection of low energy electrons during substorms is represented by changes in the electron flux at the low energy boundary and by scaling the wave power by geomagnetic activity. Three types of wave-particle interactions are included in the model.
The flux of electrons can vary significantly around the geostationary arc. The GOES satellites only provide a snapshot at one or two locations. The model can be tailored to other locations.
Key features are
- The forecasts cover the three main orbit types where most commercial satellites fly
- The forecasts are based on a physical model
- The forecasts include the physics of wave-particle interactions
- The forecasts can be tailored to specific satellites at GEO or other orbits.
For more details on the model see
Glauert et al. J. Geophysical Res., : http://onlinelibrary.wiley.com/doi/10.1002/2013JA019281/abstract
Horne et al. Space Weather, : http://onlinelibrary.wiley.com/doi/10.1002/swe.20023/abstract | 0.810585 | 3.657214 |
For decades, astronomers have assumed that Earth-like planets cannot form around binary stars on account of wacky gravitational effects. Which, for Star Wars fans, was a total downer. But a new study suggests that not only is the formation of Tatooine-like planets very much possible, they may actually be quite common.
Unlike the accretion disk surrounding a young solitary star, the planet-forming environment around a binary system is subject to seriously disruptive gravitational ebbs and flows. In turn, many astronomers believed that the formation of rocky planets around binary stars is either very difficult or outright impossible. A new study by Ben Bromley from the University of Utah and Scott Kenyon of the Smithsonian Astrophysical Observatory now suggests otherwise.
"Tatooine in Star Wars was inspirational to many of us," Bromley told io9. "It was disappointing when earlier theories predicted that making Earth-like planets would be problematic or impossible. Our work shows that nature provides a clear path for making planets around binary stars, following the same recipe as for Earth."
So, along with the discovery that terrestrial planets are common, so too are Tatooines, say the researchers.
"We started our study to understand Pluto, its large moon Charon, and their family of satellites," says Bromley. "That work led us to Tatooine, an example of how learning about our own neighborhood can teach us about the Universe at large."
That Universe at large happens to contain an abundance of binary star systems. So many, in fact, that multiple star systems account for roughly half of all star systems in the galaxy. It's crucial, therefore, that astronomers understand the planetary architectures and gravitational topologies that typify these systems, especially if we're to look for life within them.
The primary finding of the new study is that, outside a region near the binary where orbits are typically unstable, planet formation — whether it be a gas giant or a terrestrial Earth-like planet — can unfold in pretty much the same way as it does in a system with a single star.
"In our scenario, planets are as prevalent around binaries as around single stars," the researchers noted in a University of Utah statement.
That's a surprising conclusion given what we thought we knew about binary stars.
What makes this possible is the presence of what astronomers call "most circular orbits."
During the protoplanetary phase of development, binary stars suck up the bits of gas and dust that would normally come together to form planets. That is unless, as the researchers point out, this debris is in the right orbit — one that happens to be "most circular."
Artistic impression of Kepler-47, the first transiting circumbinary system — multiple planets orbiting two suns. (Credit: NASA/JPL-Caltech/T. Pyle)
To be fair, these orbits are not exactly circular. More like oval-shaped orbits containing numerous smaller waves within them.
"Circular orbits are special around a single star because growing planets can settle on them, and gently collect material around them," Bromley explained to io9.
But because binary stars exert gravity differently than single stars, they generate eccentric orbits that carve out paths were growing planets can settle. These orbits can get so tangled that they cross each other's paths at high speeds, resulting in a regular onslaught of planetesimal collisions that prohibit further growth.
"These paths are distorted from a circle so that planets and neighboring particles can ebb and flow together in response to the binary's gravity, like seabirds floating on waves in a rough sea," he says. "If the binary stars are on elliptical orbits themselves, these most circular paths turns out to be elliptical, too."
But as Bromley points out, if the planetesimals are in an oval-shaped orbit instead of a circle, their orbits can be nested and they won't bash into each other.
"They can find orbits where planets can form," says Bromley.
Prior to this study, computer models developed by astrophysicist Zoe Leinhardt of the University of Bristol showed that it was possible for Tatooines to form. But her work focused exclusively on models of the Kepler-34 binary system and its gas giant Kepler-34(AB)b. Bromley and Kenyon took a more expansive approach, using complex mathematical formulas to describe how binary stars can be orbited by gas giants as well as planetesimals.
To date, NASA's Kepler space telescope has helped astronomers discover more than 1,000 extrasolar planets. Seven of these orbit either within or near the habitable zone of binary stars — but not one of them is a rocky, Earth-like planet. They're all Neptune- or Jupiter-sized giants.
That doesn't mean Tatooine-like planets aren't out there. This may be an observational selection effect whereby gas giants are simply easier to detect with the current generation of telescopic technologies. If the Bromley and Kenyon paper is of any indication, future planet-hunting missions may find these systems in abundance.
This study has been submitted to the Astrophysical Journal for review. For now, you can read it at the preprint arXiv: "Planet formation around binary stars: Tatooine made easy". | 0.906872 | 3.964845 |
At the edge of our Solar System, some unknown object is manipulating the paths of chunks of ice as they circle the Sun.
These objects' oval-shaped orbits all point in the same direction and tilt the same way, suggesting that an unseen force is herding them.
At first, scientists thought the culprit was a mysterious planet, which they dubbed Planet Nine (though some call it Planet X).
Although the existence of primordial black holes has not been confirmed, some scientists think the Universe is teeming with them. If they exist, such black holes could make up the 80 percent of the Universe that scientists can't see.
They know this "dark matter" exists because its gravity pulls on things throughout the Universe.
A new paper posted on Tuesday on arXiv, an online repository for research that has not been peer-reviewed, suggests that Planet Nine could be one of these ancient black holes. The researchers proposed new ways to hunt down this mysterious missing piece.
"Once you start thinking about more exotic objects, like primordial black holes, you think in different ways," James Unwin, a theoretical physicist and coauthor of the paper, told Gizmodo.
"We advocate that rather than just looking for it in visible light, maybe look for it in gamma rays. Or cosmic rays."
Planet 9 explains distant objects' weird orbits
At the fringes of our Solar System are thousands of small icy bodies that make up a region astronomers call the Kuiper Belt. Six of those objects appear to have bizarre orbits that indicate some unknown source of gravity is tugging on them.
In 2016, computer simulations and mathematical models revealed that the culprit could be a mysterious distant planet we've never seen: Planet Nine.
In that study, the planetary scientists Konstantin Batygin and Michael Brown calculated that Planet Nine's gravitational pull means it could have up to 10 times the mass of Earth.
On average, the mysterious body orbits the Sun at a distance 20 times farther than Neptune – about 18.6 billion miles. It could take between 10,000 and 20,000 years for it to complete one trip around the Sun. (Pluto, by comparison, takes 248 years to complete its orbit.)
Batygin and Brown suggested that Planet Nine could have formed in the same way as the gas giants we know well – Jupiter, Saturn, Uranus, and Neptune – starting as an ice core, then grabbing all the gas around it.
Planet Nine may have gotten too close to Jupiter or Saturn, they suggested, and was flung out to the edges of the Solar System, where it now follows an eccentric orbit and influences the Kuiper Belt objects.
Since the mysterious world exerts such a powerful gravitational force on a large region of the Solar System, Brown called it "the most planet-y of the planets in the whole Solar System." But that may not be the case.
Rather than a planet, it could be a primordial black hole
For the new study, researchers looked at data on the six Kuiper Belt objects' bizarre orbits and also incorporated recent observations about how light travelling through the Solar System appears to be bending because of an object (or objects) that scientist haven't accounted for.
Both of these strange phenomena are likely caused by the interference of unknown objects, each with similar mass. So a primordial black hole could be to blame for both, the study suggested. It could be one black hole the size of a bowling ball with the mass of 10 Earths, or a number of smaller primordial black holes that add up to that mass.
The researchers also said that a dense group of free-floating planets outside our Solar System could explain the light bending; by that logic, Planet Nine could be one of those free roamers that was captured by our Solar System.
Really, Batygin told Gizmodo, Planet Nine could be any kind of low-visibility object with the right mass.
"Planet Nine could be a five-Earth-mass hamburger," he said. "But a black hole the size of your wallet is a bit harder to find."
The scientists behind the new study said that direct observations of the mysterious object - if astronomers can find it - could help determine whether it's a planet or black hole.
So the hunt for Planet Nine, they suggested, should include a search for moving sources of x-rays, gamma rays, and other types of radiation, since those clues could indicate the edges of a black hole.
If scientists detect such signals, they could find out whether Planet Nine has been a black hole all along.
This article was originally published by Business Insider.
More from Business Insider: | 0.857262 | 3.824022 |
NASA's Kepler space telescope has discovered more than 700 new exoplanets, nearly doubling the current number of confirmed alien worlds.
The 715 newfound planets, which scientists announced today (Feb. 26), boost the total alien-world tally to between 1,500 and 1,800, depending on which of the five main extrasolar planet discovery catalogs is used. The Kepler mission is responsible for more than half of these finds, hauling in 961 exoplanets to date, with thousands more candidates awaiting confirmation by follow-up investigations.
"This is the largest windfall of planets — not exoplanet candidates, mind you, but actually validated exoplanets — that's ever been announced at one time," Douglas Hudgins, exoplanet exploration program scientist at NASA's Astrophysics Division in Washington, told reporters today. [Kepler's Exoplanet Bonanza Explained (Infographic)]
About 94 percent of the new alien worlds are smaller than Neptune, researchers said, further bolstering earlier Kepler observations that suggested the Milky Way galaxy abounds with rocky planets like Earth.
Most of the 715 exoplanets orbit closely to their parent stars, making them too hot to support life as we know it. But four of the worlds are less than 2.5 times the size of Earth and reside in the "habitable zone," that just-right range of distances that could allow liquid water to exist on their surfaces.
The $600 million Kepler spacecraft launched in March 2009 to determine how frequently Earth-like planets occur around our galaxy. The observatory detects alien worlds by noticing the telltale brightness dips caused when they pass in front of, or transit, their parent stars from Kepler's perspective.
Kepler's original planet-hunting mission ended last May when the second of its four orientation-maintaining reaction wheels failed, robbing the spacecraft of its ultraprecise pointing ability. Still, scientists have expressed confidence that they will be able to achieve the mission's chief goals with the data Kepler gathered during its first four years in space.
Those were very productive years. Kepler has flagged more than 3,600 planet candidates to date, and mission team members expect that about 90 percent of them will end up being the real deal.
Indeed, the 715 new planets were pulled from just the first two years of Kepler observations, so more big planet-confirmation hauls could be coming as researchers work their way through the rest of the mission's huge database.
All of the 715 newfound alien planets reside in multiplanet systems, just like Earth. Taken together, the new planets orbit a total of 305 stars, researchers said. And these systems are generally reminiscent of the inner regions of our own solar system, where planets travel around the sun in circular orbits that are more or less in the same plane, they added.
"These results establish that planetary systems with mulitple planets around one star, like our own solar system, are in fact common," Hudgins said.
Scientists validated the newly discovered worlds using a powerful and sophisticated new method called "verification by multiplicity," which works partly on the logic of probability.
During its original mission, Kepler stared continuously at more than 150,000 stars, finding planet candidates around several thousand of them. If these candidates were distributed randomly, just a few would reside in multiplanet systems. But Kepler has found hundreds of such systems, a fact that helped scientists identify the 715 bona fide new planets.
"Multiplicity is a powerful technique for wholesale validation that will be used again in the future," said Jason Rowe of the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, Calif.
The method should help researchers confirm hundreds more Kepler candidates down the road, Rowe and others said. A higher percentage of these future finds should be in the habitable zone, they added, since it takes longer for the spacecraft to detect more distantly orbiting exoplanets than ones that zip around their star in a matter of days or weeks (and researchers haven't analyzed the last two years of Kepler data using the multiplicity technique).
The studies that detail the discovery of the 715 alien worlds will be published March 10 in The Astrophyiscal Journal.
The five main exoplanet-discovery databases, and their current tallies (with the new Kepler finds included), are: the Extrasolar Planets Encyclopedia (1,790); the Exoplanets Catalog, run by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo (1,790); the NASA Exoplanet Archive (1,749); the Exoplanet Orbit Database (1,490); and the Open Exoplanet Catalog (1,714).
The different numbers reported by the databases reflect the uncertainties inherent in exoplanet detection and confirmation.
While Kepler's original mission operations have ended, the spacecraft may not be done hunting for alien planets. Team members have proposed a new mission for Kepler called K2, which would allow the observatory to search for a variety of celestial objects and phenomena, including exoplanets, supernova explosions and comets and asteroids in our own solar system.
NASA is expected to make a final decision about the K2 mission proposal by this summer, officials have said. | 0.882667 | 3.270364 |
Isaac Asimov dubbed neutrinos "ghost particles." John Updike immortalized them in verse. They've been the subject of several Nobel Prize citations, because these weird tiny particles just keep surprising physicists. And now we have a much better idea of the upper limit of what their rest mass could be, thanks to the first results from the Karlsruhe Tritium Neutrino experiment (KATRIN) in Germany. Leaders from the experiment announced their results last week at a scientific conference in Japan and posted a preprint to the physics arXiv.
"Knowing the mass of the neutrino will allow scientists to answer fundamental questions in cosmology, astrophysics, and particle physics, such as how the universe evolved or what physics exists beyond the Standard Model," said Hamish Robertson, a KATRIN scientist and professor emeritus of physics at the University of Washington. "These findings by the KATRIN collaboration reduce the previous mass range for the neutrino by a factor of two, place more stringent criteria on what the neutrino's mass actually is, and provide a path forward to measure its value definitively."
The ghostly particles are devilishly hard to detect because they so rarely interact with other particles, and when they do, they only interact via the weak nuclear force. Most neutrino hunters bury their experiments deep underground, the better to cancel out noisy interference from other sources, notably the cosmic rays continually bombarding Earth's atmosphere. The experiments usually require enormous tanks of liquid—dry-cleaning fluid, water, heavy water, mineral oil, chlorine, or gallium, for example, depending on the experimental setup. This increases the chances of a neutrino striking one of the atoms in the medium of choice, triggering the decay process. The atom changes into a different element, emitting an electron in the process, which can be detected.
Neutrinos were first proposed by Wolfgang Pauli in a 1930 letter to colleagues. He was trying to explain some baffling experimental results on radioactive beta decay in atomic nuclei, where energy appeared to be missing—something he deemed (correctly) to be impossible. He thought a new kind of subatomic particle with no charge and no mass may have carried away the missing energy; it was Enrico Fermi who later dubbed it a neutrino.
Clyde Cowan and Frederick Reines were the first to observe these ghostly particles in 1956, thanks to the fusion reactions in nuclear power plants that proliferated after World War II. Ten years later, physicists detected the first solar neutrinos from the Sun. This snagged Ray Davis Jr. and Masatoshi Koshiba a Nobel Prize in 2002, shared with Riccardo Giacconi (who was honored "for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources").
The only problem was that there were far fewer solar neutrinos being detected than predicted by theory, a conundrum that became known as the solar neutrino problem. In 1962, physicists discovered a second type ("flavor") of neutrino, the muon neutrino. This was followed by the discovery of a third flavor, the tau neutrino, in 2000.
By then, physicists already suspected that neutrinos might be able to switch from one flavor to another, thanks in large part to 1998 observations by Japan's Super-Kamiokande collaboration (Super-K). In 2002, scientists at the Sudbury Neutrino Observatory (or SNO) announced they had solved the solar neutrino problem. The missing solar (electron) neutrinos were just in disguise, having changed into a different flavor on the long journey between the Sun and the Earth. Arthur B. McDonald of SNO and Takaaki Kajita of Super-K shared the 2015 Nobel Prize in Physics for their respective breakthroughs.
If neutrinos oscillate, then they must have a teensy bit of mass after all. As Adrian Cho explained in a 2016 article for Science, "Were neutrinos massless, they would have to move at light speed, at least in a vacuum, according to Einstein's theory of relativity. If that were the case, time for them would stand still, and change would be impossible."
But determining precisely what that mass is constitutes another knotty neutrino-related problem. There are three neutrino flavors, but none of them has a well-defined mass. Rather, different kinds of "mass states" mix together in various ways to produce electron, muon, and tau neutrinos. That's quantum weirdness for you.
KATRIN's new results placing an upper limit for neutrino mass actually applies to the average of all three masses. The lower bound is 0.02 eV (electron volts); neutrinos can't have a lower mass than that. And KATRIN's data suggests they can't weigh more than 1 eV—or 1/500,000th of the mass of the electron.
The experiment uses tritium (a highly radioactive isotope of hydrogen, with one proton and two neutrons) to generate electron-neutrino pairs: an electron and a neutrino that share 18,650 eV of energy between them. Usually that energy is divided equally, but there are rare pairs—just a fraction of the roughly 25 billion electron-neutrino pairs produced every second—where the electron hogs nearly all of it, so there's only a tiny amount left for the neutrino. Those pairs are the focus of KATRIN scientists. They can't measure the neutrinos directly, so instead they subtract the electron's energy to deduce that of the neutrino and, hence, its mass (because E=mc2).
These preliminary results are based on just 28 days of data, so it doesn't constitute a definitive measurement yet; more data is needed. But it's already half the previous estimate of what physicists thought the upper limit on mass would be, and the actual value could be lower still. Or neutrinos could throw physicists another curveball and the additional data will yield a higher upper limit.
The experiment could also shed light on the possible existence of an exotic fourth type of neutrino, dubbed the "sterile" neutrino, that doesn't interact with regular matter at all, apart from, perhaps, its fellow neutrinos. That would have big implications for the nature of dark matter, although despite a tantalizing hint in 2018, sterile neutrinos have thus far proven elusive.
"There is indirect evidence that the neutrino masses are smaller than what KATRIN taught us last week," André de Gouvêa, a theoretical physicist at Northwestern University who was not involved in the measurement, told Scientific American. “The indirect evidence does not replace what KATRIN can do, however, so the result in itself is very significant. Perhaps more important is that KATRIN demonstrated that things are working and that they appear to be on track to reach much further." | 0.841794 | 4.197958 |
How hot is hot? How hot is really hot? How hot is the hottest hot that hot can get? If you said 100 billion degrees Kelvin (179 billion degrees Fahrenheit), you’re one of those sharp people who’s up on their theoretical limits – that’s the scientifically-accepted theoretical temperature limit … until now. Russian researchers have discovered a black hole that added two zeroes to the theoretical limit when it was measured at 10 trillion degrees Kelvin or 18 trillion degrees Fahrenheit. Is this quasar having the mother of all hot flashes?
This temperature record was determined at Moscow’s Lebedev Physical Institute where Yuri Kovalev worked with fellow astronomers at three other observatories to link four telescopes together – the Russian Skeptr-R satellite and three ground telescopes that were part of the RadioAstron mission which combines the signals of radio telescopes using a technique called interferometry to make one that’s the equivalent of eight Earth diameters wide.
According to the study in The Astrophysical Journal, the telescopes were pointed at the giant quasar 3C 273, which is in an elliptical galaxy in the constellation Virgo, 2.5 billion light years away. The precision of this interferometry-created telescope set the temperature of the jets shooting out of this black hole at an astonishing 18 trillion degrees F.
This result is very challenging to explain with our current understanding of how relativistic jets of quasars radiate. This means that our traditional theories about how quasars’ cores emit light are incorrect.
That understatement is from Yuri Kovalev, who must now come up with a new explanation or be kicked off the island (wait, wrong reality show). One theory for the record temperature of the black hole’s jets is that it’s actually accelerating protons instead of the generally-assumed electrons – electrons cool each other down with X-rays and gamma rays. However, because protons are so much larger than electrons, the energy needed to accelerate them is beyond comprehension. Then again, so was a temperature above 100 billion Kelvin.
Kovalev admits that this and other theories for the black hole hot flash have, well, black holes in them. That doesn’t bother him.
Obviously, for a scientist, there is nothing more pleasant, exciting and successful than to get a result that does not comply with a theory, because this is the most effective way to push the scientific research further.
Spoken like a true geek. | 0.841741 | 3.773172 |
Under the auspices of the International Ocean Discovery Program (IODP), during April and May 2016 a large team of scientists and engineers sank a 1.3 km deep drill hole into the offshore, central part of the Chicxulub impact crater, which coincided with the K-Pg mass extinction event. Over the last year work has been underway to analyse the core samples aimed at investigating every aspect of the impact and its effects. Most of the data is yet to emerge, but the team has published the results of advanced modelling of the amount of climate-affecting gases and dusts that may have been ejected (Artemieva, N. et al. 2017. Quantifying the release of climate-active gases by large meteorite imp-acts with a case study of Chicxulub. Geophysical Research Letters, v. 44; DOI: 10.1002/2017GL074879). . From petroleum exploration in the Gulf of Mexico the impact site is known to have been underlain by about 2.5 to 3.5 km of Mesozoic sediments that include substantial amounts of limestones and evaporitic anhydrite (CaSO4) – thicknesses of each are of the order of a kilometre. The impact would inevitably have yielded huge volumes of carbon- and sulfur dioxide gases, as well as water vapour plus solid and molten ejecta. The first, of course, is a critical greenhouse gas, whereas SO2 would form sulfuric acid aerosols if it entered the stratosphere. They are known to block incoming solar radiation. So both warming and cooling influences would have been initiated by the impact. Dust-sized ejecta that lingered in the atmosphere would also have had climatic cooling effects. The questions that the study aimed to answer concerns the relative masses of each gas that would have reached more than 25 km above the Earth to have long-term, global climatic effects and whether the dominant effect on climate was warming or cooling. Both gases would have added the environmental effects of making seawater more acid.
Such estimates depend on a large number of factors beyond the potential mass of carbonate and sulfate source rocks. For instance: how big the asteroid was; how fast it was travelling and the angle at which it struck the Earth’s surface determine the kinetic energy involved and the impact mechanism. How that energy was distributed between atmosphere, seawater and the sedimentary sequence, together with the pressure-temperature conditions for the dissociation of calcite and anhydrite all need to be accounted for by modelling. Moreover, the computation itself becomes extremely long beyond estimates for the first second or so of the impact. Earlier estimates had been limited by computer speeds to only the first few seconds of the impact and could not allow for other than vertical impacts. The new study, by supercomputers and improved algorithms, used a likely 60° angle of impact, new data on mineral decomposition and simulated the first 15 to 30 seconds. The results suggested that 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2 were ejected, compared with earlier estimates of 40-560 Gt of sulfur and 350-3,500 Gt of CO2. The greater proportion of sulfur release to the stratosphere pushes the model decisively towards global cooling, probably over a lengthy period – perhaps centuries. Taking dusts into account implies that visible sunlight would also have been blocked, devastating the photosynthetic base of the global food chain, in the sunlit parts of oceans as well as on land.
But we have to remember that these are the results of a theoretical model. In the same manner as this study has thrown earlier modeling into doubt, more data – and there will be a great many from the Chicxulub drill core itself – and more sophisticated computations may change the story significantly. Also, the other candidate for the mass extinction event, the flood basalt volcanism of the Deccan Traps, and its geochemical effects on the climate have yet to be factored in. The next few lines of Shakespeare’s soliloquy for Richard III may well emerge from future work
… Made glorious summer by this sun of York;
And all the clouds that lour’d upon our house
In the deep bosom of the ocean buried …
See also: BBC News comment on 31 October 201 | 0.826995 | 3.252509 |
Like Uranus, all the gas giant planets have rings
One of the most prominent of the summertime constellations is Scorpius, the scorpion. With the straight line of three bright stars that constitutes its head, a long curving arc of bright stars that represents its body, and a curve of stars that arcs back northward that constitutes its tail, Scorpius is one of the relatively few constellations that actually looks like what it is supposed to represent.
This time of year it can be seen rising in the southeast during the evening hours, and it is displayed in its full splendor above the southern horizon during the hours after midnight.
Scorpius is one of the constellations in the zodiac, i.e., the path through which the sun, the moon, and the planets travel, and it currently has a fairly bright visitor near its head. This is Saturn, our solar system's second-largest planet, and primarily known for its spectacular set of encircling rings. The rings, which collectively are made of rock-sized chunks of ice, are currently at about the widest open that they can appear from Earth, and are a rather spectacular sight when viewed through even modest backyard telescopes.
When the Italian astronomer Galileo Galilei viewed Saturn through his primitive telescope in 1610, he saw what he took to be two companion objects, one on either side of the planet. Over the next few years they shrank and eventually disappeared, in the process mystifying him. It wasn't until 1655, when the Dutch astronomer Christiaan Huygens examined Saturn with a larger and better telescope than Galileo had, that he saw that the companions Galileo saw were actually a system of rings encircling the planet. Their apparent disappearance was due to the fact that, at approximately 15-year intervals, we see Saturn's rings edge-on and they all but disappear from view for a while.
Ever since then, Saturn's rings have been extensively studied, including by spacecraft such as Pioneer 11 in 1979, the twin Voyagers 1 and 2 spacecraft during the early 1980s, and the Cassini spacecraft that has been in orbit around Saturn since 2004. There are several broad ring structures, themselves composed of hundreds of individual ringlets, along with several gaps —the largest of which are visible in backyard telescopes.
For over 300 years Saturn was the only planet known to have rings. Then, on March 10, 1977, astronomers who were watching Uranus occult, or pass in front of, a background star noticed that the star vanished and reappeared nine times before Uranus got to it, and repeated this pattern as Uranus was leaving it. The conclusion was inescapable that Uranus has a system of rings, and these were well visible when Voyager 2 passed by that planet in 1986. Uranus' rings are much thinner than Saturn's, and are apparently made up of small dark rocks.
When Voyager 1 passed by Jupiter in 1979 it observed that Jupiter has a few very thin rings, which subsequent studies have revealed are made up primarily of dust. Meanwhile, a couple of rings around Neptune had been suspected since the mid-1980s as a result of its passing in front of a background star, and these were confirmed when Voyager 2 passed by that planet in 1989. Neptune's rings are very thin and, like Jupiter's, appear to be made up primarily of dust.
It turns out, then, that all four of the gas giant planets in our solar system have rings, although these vary widely in size and composition. As for other bodies in the solar system that might have rings, in 2008 one of Saturn's larger moons, Rhea, was reported as having a possible ring system based upon circumstantial evidence, however later attempts to image these rings with a camera aboard Cassini failed to detect any such rings, so at best this is an open question.
Just last year the discovery of two rings, apparently made up at least partially of ice, was announced orbiting around the object known as Chariklo. Chariklo is what is known as a centaur, large asteroid-like objects that orbit primarily between Uranus and Saturn and at least some of which may be dormant comet nuclei. Chariklo's rings were, like Uranus', discovered when it passed in front of a background star, and it is the smallest object in our solar system around which the existence of a ring system has been confirmed.
At least one planetary object with rings has been found outside our solar system. This is a planet orbiting around a star known as 1SWASP J140747.93-394542.6, which is somewhat smaller than our sun, and located 430 light-years away in the constellation Centaurus, currently visible low above our southern horizon during the later evening hours. As a result of disappearances and reappearances of the parent star as the planet, dubbed J1407b, orbited around it, astronomers in 2012 announced that it is accompanied by a ring system that is 200 times larger than Saturn's.
This is, by far, the largest planetary ring system so far discovered, and would certainly be a spectacular sight as seen from within that planetary system. The star, and its planetary system, are quite young, however — only about 16 million years old — and thus it is rather possible that the ring system around J1407b isn't a true system of rings at all, but rather an orbiting disk of material out of which moons are forming, similar to the way that Jupiter's Galilean moons are believed to have formed.
Since most of the planets that have been discovered around other stars appear to be gas giants at least somewhat similar to those in our solar system, it would appear likely that many of these are accompanied by rings as well. Whether or not bright and spectacular ring systems like those around Saturn are common remains to be seen.
Alan Hale is a professional astronomer who resides in Cloudcroft. He is involved in various space-related research and educational activities throughout New Mexico and elsewhere. His web site is http://earthriseinstitute.org | 0.926553 | 3.864177 |
Gamma-rays and dust from periodic Comet Swift-Tuttle plowed through planet Earth's atmosphere on the night of August 11/12. Impacting at about 60 kilometers per second the grains of comet dust produced this year's remarkably active Perseid meteor shower. This composite wide-angle image of aligned shower meteors covers a 4.5 hour period on that Perseid night. In it the flashing meteor streaks can be traced back to the shower's origin on the sky. Alongside the Milky Way in the constellation Perseus, the radiant marks the direction along the perodic comet's orbit. Traveling at the speed of light, cosmic gamma-rays impacting Earth's atmosphere generated showers too, showers of high energy particles. Just as the meteor streaks point back to their origin, the even briefer flashes of light from the particles can be used to reconstruct the direction of the particle shower, to point back to the origin on the sky of the incoming gamma-ray. Unlike the meteors, the incredibly fast particle shower flashes can't be followed by eye. But both can be followed by the high speed cameras on the multi-mirrored dishes in the foreground. Of course, the dishes are MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, an Earth-based gamma-ray observatory on the Canary Island of La Palma.
< | Archive | Submissions | Search | Calendar | RSS | Education | About APOD | Discuss | >
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | 0.885683 | 3.44924 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.