Anne Minard is a freelance science journalist with an academic background in biology and a fascination with outer space. Her first book, Pluto and Beyond, was published in 2007.
MESSENGER's new solar system portrait, from the inside out
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Say cheese! The MESSENGER spacecraft has captured the first portrait of our Solar System from the inside looking out. The images, captured Nov. 3 and 16, 2010, were snapped with the Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) of MESSENGER’s Mercury Dual Imaging System (MDIS).
All of the planets are visible except for Uranus and Neptune, which at distances of 3.0 and 4.4 billion kilometers were too faint to detect with even the longest camera exposure time of 10 seconds. Their positions are indicated. The dwarf-planet Pluto, smaller and farther away, would have been even more difficult to observe.
Earth’s Moon and Jupiter’s Galilean satellites (Callisto, Ganymede, Europa, and Io) can be seen in the NAC image insets. Our Solar System’s perch on a spiral arm provided a beautiful view of part of the Milky Way galaxy, bottom center.
The following is a graphic showing the positions of the planets when the graphic was acquired:
The new mosaic provides a complement to the Solar System portrait – that one from the outside looking in – taken by Voyager 1 in 1990.
These six narrow-angle color images were made from the first ever 'portrait' of the solar system taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. The spacecraft acquired a total of 60 frames for a mosaic of the solar system which shows six of the planets. Mercury is too close to the sun to be seen. Mars was not detectable by the Voyager cameras due to scattered sunlight in the optics, and Pluto was not included in the mosaic because of its small size and distance from the sun. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The background features in the images are artifacts resulting from the magnification. The images were taken through three color filters -- violet, blue and green -- and recombined to produce the color images. Jupiter and Saturn were resolved by the camera but Uranus and Neptune appear larger than they really are because of image smear due to spacecraft motion during the long (15 second) exposure times. Earth appears to be in a band of light because it coincidentally lies right in the center of the scattered light rays resulting from taking the image so close to the sun. Earth was a crescent only 0.12 pixels in size. Venus was 0.11 pixel in diameter. The planetary images were taken with the narrow-angle camera (1500 mm focal length). Credit: NASA/JPL
“Obtaining this portrait was a terrific feat by the MESSENGER team,” says Sean Solomon, MESSENGER principal investigator and a researcher at the Carnegie Institution. “This snapshot of our neighborhood also reminds us that Earth is a member of a planetary family that was formed by common processes four and a half billion years ago. Our spacecraft is soon to orbit the innermost member of the family, one that holds many new answers to how Earth-like planets are assembled and evolve.”
SUBARU Telescope image of the protoplanetary disk around the young star LkCa 15. Credit: MPIA (C. Thalmann) & NAOJ
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Chalk up a sizzling success for the HiCIAO planet-hunter camera on the Subaru Telescope in Hawaii: it’s captured this unprecedented image of a stellar disk similar in size to our own solar system, featuring rings and gaps that are associated with the formation of giant planets.
The lead image shows a bright arc of scattered light, in white, from the protoplanetary disk around the young star LkCa 15. LkCa 15 is in the center of the image, blacked out. The arc’s sharp inner edge traces the outline of a wide gap in the disk. The gap is decidedly lopsided – it is markedly wider on the left side – and has most likely been carved out of the disk by one or more newborn planets that orbit the star.
The disk gap is large enough to house the orbits of all the planets in our own Solar System. “We haven’t detected the planets themselves yet,” said Christian Thalmann, who led the LkCa 15 study while on staff at the Max Planck Institute for Astronomy.”But that may change soon.”
LkCa 15, aged a few million years, is in the Taurus constellation about 450 light years away.
The observations are part of a systematic survey called SEEDS, or the Strategic Explorations of Exoplanets and Disks with Subaru Project, with a goal to search for planets and disks around young stars using HiCIAO, a state-of-the-art high-contrast camera designed specifically for this purpose. The lead investigator on the project is Motohide Tamura at the National Astronomical Observatory of Japan, but it’s a collaborative effort with international participation. Their first significant discovery — an exoplanet candidate around a sun-like star — was announced in December.
Besides LkCa 15, the researchers have also captured a sharp images of the protoplanetary disk around the very young star AB Aur in the constellation Auriga, “the Charioteer.” Lead researcher Jun Hashimoto, of the National Observatory of Japan, and his team report nested rings of material that are tilted with respect to the disk’s equatorial plane, and whose material, intriguingly, is not distributed symmetrically around the star – irregular features that indicate the presence of at least one very massive planet.
Recent images of AB Aur taken by HiCIAO (top left), compared with an image taken in 2004 by its predecessor instrument CIAO (top right). The new images give a much more detailed view of the inner regions (bottom left; with explanations bottom right): Intricate bright and dark patterns indicate the presence of different rings of matter. The fact that their centers do not coincide with the position of the star and the other irregularities point to the existence of a massive giant planet which is sweeping up the material between the rings. Credit: NAOJ/J. Hashimoto
The researchers point out that no other telescopes, whether ground-based or in space, have ever penetrated so close to a central star, showing the details of its disk.
Planetary systems like our own share a humble origin as mere by-products of star formation. A newborn star’s gravity gathers leftover gas and dust in a dense, flattened disk of matter orbiting the star. Clumps in the disk sweep up more and more material, until their own gravity becomes sufficiently strong to compress them into the dense bodies we know as planets.
Flocculent Spiral NGC 2841, in the constellation Ursa Major. Credit: NASA, ESA and Hubble
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The Flocculent Spiral NGC 2841, shown above, is known for its profusion of young, blue stars. And yet, until recently, astronomers haven’t been able to use those stars as windows into the still-mysterious phenomenon of star formation.
Hubble’s most recent wide-field camera upgrade is changing that.
The new Wide Field Camera 3 (WFC3) was installed on Hubble in May 2009 during Servicing Mission 4, and replaces the Wide Field and Planetary Camera 2. The new camera is optimized to observe in the infrared and ultraviolet wavelengths emitted by newborn stars, shown by the bright blue clumps in the lead image. Thus, it can peer behind the veil of dust that would otherwise hide those stars from view.
The image shows a lot of hot, young stars in the disc of NGC 2841, but in reality there are just a few sites of current star formation where hydrogen gas is collapsing into new stars. It is likely that these fiery youngsters destroyed the star-forming regions in which they were formed.
Image from NASA's Galaxy Evolution Explorer (GALEX), via the NASA/IPAC Extragalactic Database
NGC 2841 is about 46 million light years away in the constellation Ursa Major. It’s part of a common group of galaxies called flocculent spirals; flocculent means fluffy or wooly-looking. Rather than boasting well-defined spiral arms, these galaxies display patchy stellar distribution.
Star formation is one of the most important processes shaping the Universe; it plays a pivotal role in the evolution of galaxies and it is also in the earliest stages of star formation that planetary systems first appear. Yet there is still much that astronomers don’t understand, such as how the properties of stellar nurseries vary according to the composition and density of the gas present, and what triggers star formation in the first place. The driving force behind star formation is particularly unclear for flocculent spirals.
An international team of astronomers is using Hubble’s WFC3 to study a sample of nearby, but wildly differing, locations where stars are forming. The observational targets include both star clusters and galaxies, and star formation rates range from the baby-booming starburst galaxy Messier 82 to the much more sedate star producer NGC 2841.
Detailed credit information for the lead image: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O’Connell (University of Virginia), B. Whitmore (STScI) and the WFC3 Scientific Oversight Committee.
False color image of the Lockman-hole area of the sky at infrared wavelengths as imaged by the Herschel Space Observatory. Credit: ESA/SPIRE Consortium/HerMES Consortium
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When it comes to forming stars, the size of a galaxy does matter, according to research out today in the online version of Nature.
But it doesn’t have to be as massive as we once thought.
Alexandre Amblard, an astrophysicist at the University of California, Irvine, and his colleagues used new data from the Herschel Space Observatory to peer into Lockman Hole area of the sky, where extragalactic light comes from star-forming galaxies out of reach for even the world’s most powerful telescopes.
The Lockman Hole is a patch of the sky, 15 square degrees, lying roughly between the pointer stars of the Big Dipper.
Called submillimetre galaxies, the study subjects emit light at wavelengths between the radio and infrared parts of the spectrum, so studying them requires novel approaches borrowing from both radio and optical astronomy. The galaxies by themselves are too blurry to be resolved with individual far-infrared telescopes – but their average properties can be observed and analyzed, which is exactly what Amblard and his colleagues did.
The authors measured variations in the intensity of extragalactic light at far-infrared wavelengths, and derived statistics for the level of clustering of light halos. They assume that the clustering reflects the underlying distribution of dark matter, and fit the data to a halo model of galaxy formation, which connects the spatial distribution of galaxies in the Universe to that of dark matter.
Distribution of dark matter when the Universe was about 3 billion years old, obtained from a numerical simulation of galaxy formation. The left panel displays the continuous distribution of dark matter particles, showing the typical wispy structure of the cosmic web, with a network of sheets and filaments, while the right panel highlights the dark matter halos representing the most efficient cosmic sites for the formation of star-bursting galaxies with a minimum dark matter halo mass of 300 billion times that of the Sun. Credit: VIRGO Consortium/Alexandre Amblard/ESA
Amblard and his colleagues discovered an enormous fact: the ‘haloes’ of dark matter that surround the Universe’s most active star-forming galaxies are each more massive than about 300 billion solar masses.
What’s even more interesting is that the new threshold for star formation is actually smaller than some previous estimates.
“I think there was one prediction that put the number around 5000 billion times that of the sun, but that was just a prediction from a theory of galaxy formation.“ said Asantha Cooray, also an astrophysicist at UC Irvine and second author on the new paper. “The general consensus was that it may be between 100 to 1000 billion times the sun. We now have a more precise answer from this work.”
Cooray said he’s most excited “that we can look at a detailed image of the sky showing distant, star-forming galaxies and infer not only details about the stars and gas in those galaxies but also about the amount of dark matter needed to form such galaxies. Beyond inferring the presence, we still don’t know exactly what dark matter is.”
The results appear online ahead of print today on Nature’s website.
Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)
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Imagine a spinning black hole so colossal and so powerful that it kicks photons, the basic units of light, and sends them careening thousands of light years through space. Some of the photons make it to Earth. Scientists are announcing in the journal NaturePhysics today that those well-traveled photons still carry the signature of that colossal jolt, as a distortion in the way they move. The disruption is like a long-distance missive from the black hole itself, containing information about its size and the speed of its spin.
The researchers say the jostled photons are key to unraveling the theory that predicts black holes in the first place.
“It is rare in general-relativity research that a new phenomenon is discovered that allows us to test the theory further,” says Martin Bojowald, a Penn State physics professor and author of a News & Views article that accompanies the study.
Black holes are so gravitationally powerful that they distort nearby matter and even space and time. Called framedragging, the phenomenon can be detected by sensitive gyroscopes on satellites, Bojowald notes.
Lead study author Fabrizio Tamburini, an astronomer at the University of Padova (Padua) in Italy, and his colleagues have calculated that rotating spacetime can impart to light an intrinsic form of orbital angular momentum distinct from its spin. The authors suggest visualizing this as non-planar wavefronts of this twisted light like a cylindrical spiral staircase, centered around the light beam.
“The intensity pattern of twisted light transverse to the beam shows a dark spot in the middle — where no one would walk on the staircase — surrounded by concentric circles,” they write. “The twisting of a pure [orbital angular momentum] mode can be seen in interference patterns.” They say researchers need between 10,000 and 100,000 photons to piece a black hole’s story together.
And telescopes need some kind of 3D (or holographic) vision in order to see the corkscrews in the light waves they receive, Bojowald said: “If a telescope can zoom in sufficiently closely, one can be sure that all 10,000-100,000 photons come from the accretion disk rather than from other stars farther away. So the magnification of the telescope will be a crucial factor.”
He believes, based on a rough calculation, that “a star like the sun as far away as the center of the Milky Way would have to be observed for less than a year. So it is not going to be a direct image, but one would not have to wait very long.”
Study co-author Bo Thidé, a professor and program director at the Swedish Institute of Space Physics, said a year may be conservative, even in the case of a small rotation and a need for up to 100,000 photons.
“But who knows,” he said. “We will know more after we have made further detailed modelling – and observations, of course. At this time we emphasize the discovery of a
new general relativity phenomenon that allows us to make observations, leaving precise quantitative predictions aside.”
CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i
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Titan is just fun. Seems like every other week, another fascinating tidbit emerges about how interesting Saturn’s famous moon really is — and how compellingly similar to Earth.
A United States team of astronomers is releasing this image today in Nature. It’s an adaptive optics peek at a storm over the wild object’s parched, dry desert.
The new research, to be published in the August 13 issue of the journal, announces the discovery of significant cloud formation (about three million square kilometers, or 1.16 million square miles) within the moon’s tropical zone near its equator. Prior to this event (in April 2008) it was not known whether significant cloud formation was possible in Titan’s tropical regions. This activity in Titan’s tropics and mid-latitudes also seems to have triggered subsequent cloud development at the moon’s south pole where it was considered improbable due to the Sun’s seasonal angle relative to Titan.
The evidence comes from astronomers using the Gemini North telescope and NASA’s Infrared Telescope Facility (IRTF), both on Hawaii’s Mauna Kea.
“We obtain frequent observations with IRTF giving us a ‘weather report’ of sorts for Titan. When the IRTF observations indicate that cloud activity has increased, we are able to trigger the next night on the Gemini telescope to determine where on Titan the clouds are located,” said team member Emily Schaller, who was at the University of Hawai‘i Institute for Astronomy when this work was done.
Saturn and Titan (six o'clock). CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i
Titan, the solar system’s second largest moon, has received considerable attention by scientists since NASA’s Cassini mission deployed the Huygens probe that descended through the moon’s atmosphere in January 2005. During its descent, the probe’s cameras revealed small-scale channels and what appear to be stream beds in the equatorial regions that seemed to contradict atmospheric models predicting extremely dry desert-like conditions near the equator. Until now these erosional (fluvial) features have been explained by the possibility of liquid methane seeping out of the ground.
“In April 2008 we observed what was a global event that shows how storm activity in one region can trigger clouds, and probably rainfall, over arid regions, such as the tropics where Huygens landed,” said team member Henry Roe, an astronomer at Lowell Observatory. “Of course these rain showers are not liquid water like here on Earth, but are instead made of liquid methane. Just like the streambeds and channels that are carved by liquid water on Earth, we see features on Titan that have been created by flowing liquid methane.”
Unlike the Earth, on Titan, where the temperature is hundreds of degrees below freezing, methane (or natural gas) is a liquid and it the dominant driver of the moon’s weather and surface erosion. Any water on Titan is frozen on or below the moon’s surface and resemble rocks or boulders on Titan’s surface.
Mid-latitude and polar cloud formations have been bserved for many years (by this team and others) but the combination of extensive monitoring at the IRTF with rapid follow-up using Gemini allowed the team to capture the process as it unfolded near the equator. The team monitored Titan on 138 nights over 2.2 years and during that time cloud cover was well under one percent. Then, mid-April of 2008, just after team member and Ph.D. candidate Schaller had handed in her doctoral dissertation focusing on Titan’s minimal cloud cover she noticed the dramatic increase in cloud cover.
During this three-week episode clouds forming at about 30 degrees south latitude were observed, followed several days later by clouds closer to the equator and at the moon’s south pole. The apparent connection between the cloud formations leads to the possibility that cloud formation in one area of the moon can instigate clouds in other areas by a process known as atmospheric teleconnections. This same phenomena occurs in the Earth’s atmosphere and is caused by what are called planetary Rossby waves which are well understood.
The high-resolution Gemini images of Titan were all obtained with adaptive optics technology which uses a deformable mirror to remove distortions to light caused by the Earth’s atmosphere and produce images showing remarkable detail in the tiny disk of the moon.
“Without this technology this discovery would be impossible from the surface of the Earth,” said Schaller. Currently the Cassini spacecraft is orbiting Saturn but only flies by Titan once every 6 weeks or so. This makes continuous ground-based monitoring important for studying features like these with shorter periods on the order of 3-weeks like this storm.
Further detail about the lead image: Gemini North adaptive optics image of Titan showing storm feature (bright area). Titan is about 0.8 arcsecond across in this 2.12 micron near-infrared image obtained on April 14, 2008 (UTC). CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i
The violent youth of solar proxies. Courtesy of IAU.
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We don’t know how lucky we are — really.
We know the interaction between Earth and Sun is a rarity in that it allowed life to form. But scientists working to understand the possibility that it could have happened elsewhere in the Universe are still far from drawing conclusions.
What is becoming clearer is that life probably shouldn’t have formed here; the Earth and Sun are unlikely hosts.
A series of presentations at this year’s meeting of the International Astronomical Union meeting, in Brazil last week, focused on the role of the Sun and Sun-like stars in the formation of life on planets like Earth.
Edward Guinan, a professor of astronomy and astrophysics at Villanova University in Pennsylvania, and his collaegues have been studying Sun-like stars as windows into the origin of life on Earth, and as indicators of how likely life is elsewhere in the cosmos. The work has revealed that the Sun rotated more than ten times faster in its youth (over four billion years ago) than today. The faster a star rotates, the harder the magnetic dynamo at its core works, generating a stronger magnetic field, so the young Sun emitted X-rays and ultraviolet radiation up to several hundred times stronger than it does today.
A team led by Jean-Mathias Grießmeier from ASTRON in the Netherlands looked at another type of magnetic fields — that around planets. They found that the presence of planetary magnetic fields plays a major role in determining the potential for life on other planets as they can protect against the effects of both stellar particle onslaughts.
“Planetary magnetic fields are important for two reasons: they protect the planet against the incoming charged particles, thus preventing the planetary atmosphere from being blown away, and also act as a shield against high energy cosmic rays,” Grießmeier said. “The lack of an intrinsic magnetic field may be the reason why today Mars does not have an atmosphere.”
All things considered, the Sun does not seem like the perfect star for a system where life might arise, added Guinan.
“Although it is hard to argue with the Sun’s ‘success’ as it so far is the only star known to host a planet with life, our studies indicate that the ideal stars to support planets suitable for life for tens of billions of years may be a smaller slower burning ‘orange dwarf’ with a longer lifetime than the Sun — about 20-40 billion years,” he said.
Such stars, also called K stars, “are stable stars with a habitable zone that remains in the same place for tens of billions of years,” he added. “They are 10 times more numerous than the Sun, and may provide the best potential habitat for life in the long run.”
Not are planets like Earth the best places to harbor life, he said. Planets double or triple the size of Earth would do a better job of hanging onto an atmosphere and maintaining a magnetic field: “Furthermore, a larger planet cools more slowly and maintains its magnetic protection.”
Manfred Cuntz, an associate professor of physics at the University of Texas at Arlington, and his collaborators have examined both the damaging and the favorable effects of ultraviolet radiation from stars on DNA molecules. This allows them to study the effect on other potential carbon-based extraterrestrial life forms in the habitable zones around other stars. Cuntz says: “The most significant damage associated with ultraviolet light occurs from UV-C, which is produced in enormous quantities in the photosphere of hotter F-type stars and further out, in the chromospheres, of cooler orange K-type and red M-type stars. Our Sun is an intermediate, yellow G-type star. The ultraviolet and cosmic ray environment around a star may very well have ‘chosen’ what type of life could arise around it.”
Rocco Mancinelli, an astrobiologist with the Search for Extraterrestrial Life (SETI) Institute in California, observes that as life arose on Earth at least 3.5 billion years ago, it must have withstood a barrage of intense solar ultraviolet radiation for a billion years before the oxygen released by these life forms formed the protective ozone layer. Mancinelli studies DNA to delve into some of the ultraviolet protection strategies that evolved in early life forms and still persist in a recognizable form today. As any life in other planetary systems must also contend with radiation from their host stars, these methods for repairing and protecting organisms from ultraviolet damage serve as models for life beyond Earth. Mancinelli says “We also see ultraviolet radiation as a kind of selection mechanism. All three domains of life that exist today have common ultraviolet protection strategies such as a DNA repair mechanism and sheltering in water or in rocks. Those that did not were likely wiped out early on.”
The scientists agree that we do yet know how ubiquitous or how fragile life is, but as Guinan concludes: “The Earth’s period of habitability is nearly over — on a cosmological timescale. In a half to one billion years the Sun will start to be too luminous and warm for water to exist in liquid form on Earth, leading to a runaway greenhouse effect in less than 2 billion years.”
Credit: KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise
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A new black hole may not voraciously devour nearby gas — because it may kick out most of the gas in its neighborhood, a new study shows.
Marcelo Alvarez, of Stanford University, and his colleagues performed a new supercomputer simulation designed to track the fate of the universe’s first black holes. They found that, counter to expectations, young black holes couldn’t efficiently gorge themselves on nearby gas.
“The first stars were much more massive than most stars we see today, upwards of 100 times the mass of our sun,” said John Wise, a post-doctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and one of the study’s authors. “For the first time, we were able to simulate in detail what happens to the gas around those stars before and after they form black holes.”
The intense radiation and strong outflows from these massive stars caused nearby gas to dissipate. “These stars essentially cleared out most of the gas in their vicinity,” Wise said. A fraction of these first stars didn’t end their lives in grand supernovae explosions. Instead, they collapsed directly into black holes.
But the black holes were born into a gas-depleted cavity and, with little gas to feed on, they grew very slowly. “During the 200 million years of our simulation, a 100 solar-mass black hole grew by less than one percent of its mass,” Alvarez said.
Movie, credit KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise
Starting with data taken from observations of the cosmic background radiation — a flash of light that occurred 380,000 years after the big bang that presents the earliest view of cosmic structure — the researchers applied the basic laws that govern the interaction of matter and allowed their model of the early universe to evolve. The complex simulation included hydrodynamics, chemical reactions, the absorption and emission of radiation, and star formation.
In the simulation, cosmic gas slowly coalesced under the force of gravity and eventually formed the first stars. These massive, hot stars burned bright for a short time, emitting so much energy in the form of starlight that they pushed away nearby gas clouds.
These stars could not sustain such a fiery existence for long, and they soon exhausted their internal fuel. One of the stars in the simulation collapsed under its own weight to form a black hole. With only wisps of gas nearby, the black hole was essentially “starved” of matter on which to grow.
Yet, despite its strict diet, the black hole had a dramatic effect on its surroundings. This was revealed through a key aspect of the simulation called radiative feedback, which accounted for the way X-rays emitted by the black hole affected distant gas.
Even on a diet, a black hole produces copious X-rays. This radiation not only kept nearby gas from falling in, but it heated gas a hundred light-years away to several thousand degrees. Hot gas cannot come together to form new stars. “Even though the black holes aren’t growing significantly, their radiation is intense enough to shut off star formation nearby for tens and maybe even hundreds of millions of years,” said Alvarez.
Source: NASA. The study appears in The Astrophysical Journal Letters.
A typical model has planets forming from collisions of material swirling around stars. But new laboratory experiments indicate the colliding bodies may be much smaller than most people have thought.
Lead author Oliver Tschauner, of the University of Nevada in Las Vegas, and his colleagues have synthesized a mineral called wadsleyite that naturally exists only in meteorites and deep below the Earth’s crust. It’s believed to be the most abundant mineral in the Earth between the depths of 410 and 520 km (254 to 323 miles).
The conditions where wadsleyite forms are known from long-duration, high-pressure experiments, but the only confirmed natural occurrence is in shocked meteorites, which are remnants of the early solar system. The researchers found small quantities of wadsleyite after a high-pressure laboratory collision between thin layers of magnesium oxide and fused quartz. They suggest the mineral formed in approximately one one-millionth of a second.
On the basis of their experiments, the group inferred that the wadsleyite in ancient meteorites could be generated by collisions between bodies one to five meters (three to 16 feet) in diameter, rather than one to five kilometers (.6 to three miles).
“Based on the present results we suggest that the interpretation of the high-grade shock-metamorphic record in meteorites needs a re-evaluation,” the authors write.
First results from the Kepler mission. Credit: NASA
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NASA researchers have published confirmation this week that the Kepler mission will be able to reveal the presence of Earth-sized planets around Sun-like stars. The mission’s first scientific results appear today in the journal Science.
Lead author William Borucki, of NASA Ames Research Center in Moffett Field, California, and his colleagues announced that Kepler has detected the giant extrasolar planet HAT-P-7b, one of the roughly two dozen exoplanets that have been discovered by ground-based observations and the CoRoT mission as they “transited” in front of their stars, periodically dimming the starlight.
Many more exoplanets — more than 300 now — have been detected by the so-called “wobble” or radial velocity method, where a planet’s gravitational tug influences the motion of its star.
HAT-P-7b is comparable to Jupiter in size and orbits a star analogous to our Sun. It showed up in 10 days’ worth of Kepler data on the intensity of light from over 50,000 stars.
“The detection of the occultation without systematic error correction demonstrates that Kepler is operating at the level required to detect Earth-size planets,” the authors write.
The $500 million Kepler mission launched in March 2009 and will spend three and a half years surveying more than 100,000 sun-like stars in Cygnus-Lyra.
By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles, allowing astronomers to confirm the presence of planets and use the Hubble and Spitzer space telescopes, along with ground-based telescopes, to characterize their atmospheres and orbits. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm the planets‘ presence.
Astronomers estimate that if even one percent of stars host Earth-like planets, there would be a million Earths in the Milky Way alone. If that’s true, hundreds of Earths should exist in Kepler’s target population of 100,000 stars.
