Dec. 30, 2011: When NASA's Dawn spacecraft entered orbit around giant asteroid Vesta in July, scientists fully expected the probe to reveal some surprising sights. But no one expected a 13-mile high mountain, two and a half times higher than Mount Everest, to be one of them.
The existence of this towering peak could solve a longstanding mystery: How did so many pieces of Vesta end up right here on our own planet? A side view of Vesta's great south polar mountain. [more]
For many years, researchers have been collecting Vesta meteorites from "fall sites" around the world. The rocks' chemical fingerprints leave little doubt that they came from the giant asteroid. Earth has been peppered by so many fragments of Vesta, that people have actually witnessed fireballs caused by the meteoroids tearing through our atmosphere. Recent examples include falls near the African village of Bilanga Yanga in October 1999 and outside Millbillillie, Australia, in October 1960.
"Those meteorites just might be pieces of the basin excavated when Vesta's giant mountain formed," says Dawn PI Chris Russell of UCLA. Russell believes the mountain was created by a 'big bad impact' with a smaller body; material displaced in the smashup rebounded and expanded upward to form a towering peak. The same tremendous collision that created the mountain might have hurled splinters of Vesta toward Earth.
"Some of the meteorites in our museums and labs," he says, "could be fragments of Vesta formed in the impact -- pieces of the same stuff the mountain itself is made of."
To confirm the theory, Dawn's science team will try to prove that Vesta's meteorites came from the mountain's vicinity. It's a "match game" involving both age and chemistry.
"Vesta formed at the dawn of the solar system," says Russell. "Billions of years of collisions with other space rocks have given it a densely cratered surface."
The surface around the mountain, however, is tellingly smooth. Russell believes the impact wiped out the entire history of cratering in the vicinity. By counting craters that have accumulated since then, researchers can estimate the age of the landscape. Cross-section of the south polar mountain on Vesta with the cross sections of Olympus Mons on Mars, the largest mountain in the solar system, and the Big lsland of Hawaii as measured from the floor of the Pacific, the largest mountain on Earth. These latter two mountains are both shield volcanoes.Credit: Russell et. al. (2011), EPSC
"In this way we can figure out the approximate age of the mountain's surface. Using radioactive dating, we can also tell when the meteorites were 'liberated' from Vesta. A match between those dates would be compelling evidence of a meteorite-mountain connection."
For more proof, the scientists will compare the meteorites' chemical makeup to that of the mountain area.
"Vesta is intrinsically but subtly colorful. Dawn's sensors can detect slight color variations in Vesta's minerals, so we can map regions of chemicals and minerals that have emerged on the surface. Then we'll compare these colors to those of the meteorites."
Could an impact on Vesta really fill so many museum display cases on Earth? Stay tuned for answers..
Comet Lovejoy is putting on an amazing show in the predawn skies of the Southern Hemisphere. Here are some beautiful images!
Comet Lovejoy surprised a lot of people when it survived a very close encounter with the sun on December 16, 2011. It skimmed through the solar corona where temperatures reach up to two million degrees Fahrenheit, about 140,000 kilometers (87,000 miles) above the sun’s surface. Comet Lovejoy is now racing away from the sun, and it’s putting on a grand predawn show in the sky visible from the Southern Hemisphere. Unfortunately, the comet is not visible from the Northern Hemisphere, so us northerners have to live vicariously through the astrophotographers who have been bringing us stunning images of Comet Lovejoy. Grahame Kelaher, an Australian astrophotographer, sent this jaw-dropping image of Comet Lovejoy to EarthSky. He took it near Perth on December 22, 2011 using a Canon 7D camera. You can clearly see streaming structures in the comet’s dust tail – that’s the bright veil-like tail making a slight graceful curve to the left in the photo. The dust tail is made of dust particles tracing the comet’s path, lit by reflected sunlight. The fainter straight tail is the ion or gas tail, pointing directly away from the sun as a result of its interaction with solar wind and the sun’s magnetic field. But where is the comet’s nucleus or core? It’s not visible, perhaps it’s shrouded in the volatiles (easily evaporated substances) surrounding it. There’s a lot of curiosity about the condition of Comet Lovejoy’s nucleus. Will it remain intact? Or will it disintegrate due to the stress of its close encounter with the sun on December 16?
Fine streamers are clearly visible in this image of Comet Lovejoy, taken on December 22, 2011 near Perth, Australia. Image credit: Grahame Kelaher. Grahame also obtained this wide-angle view of the comet over the suburbs of Perth, Australia on December 21, 2011. Anyone who has stargazed in the suburbs knows how light pollution obscures the very faintest stars. That Grahame could obtain this image over Perth indicates that this comet is pretty darned bright!
Comet Lovejoy graces the sky over the suburbs of Perth Australia on December 21, 2011. Image credit: Grahame Kelaher. Another Australian photographer, Colin Legg, photographed a lovely view of Comet Lovejoy on December 21, 2011, over the Mandurah Estuary near Perth, catching its ghostly reflection on the water. Fine streamers in the dust tail are also evident in this photo. For the photography enthusiasts curious about technical details, Colin obtained this image with a Canon 5D2 using a 73 mm focal length lens, a f/4 aperture opening, an ISO setting of 3200, and an exposure time of 12 seconds.
Comet Lovejoy reflected in the water of Mandurah Esturary near Perth, on December 21, 2011. Image Credit: Colin Legg. He also created a series of time-lapse wide-angle photos on December 21, 2011 with a 24 mm focal length lens, using several different exposure times, ISO, and aperture settings. Click the link below to see it. Comet Lovejoy (2011 W3) rising over Western Australia from Colin Legg on Vimeo. Currently, the constellation Sagittarius is the backdrop for Comet Lovejoy. That will gradually change as the comet moves away from the sun. What will Comet Lovejoy do next? Remain stable? Break apart? Stay relatively bright, or rapidly fade away? Stay tuned for future updates!
Dec. 16, 2011: This morning, an armada of spacecraft witnessed something that many experts thought impossible. Comet Lovejoy flew through the hot atmosphere of the sun and emerged intact.
"It's absolutely astounding," says Karl Battams of the Naval Research Lab in Washington DC. "I did not think the comet's icy core was big enough to survive plunging through the several million degree solar corona for close to an hour, but Comet Lovejoy is still with us."
The comet's close encounter was recorded by at least five spacecraft: NASA's Solar Dynamics Observatory and twin STEREO probes, Europe's Proba2 microsatellite, and the ESA/NASA Solar and Heliospheric Observatory. The most dramatic footage so far comes from SDO, which saw the comet go in (movie) and then come back out again (movie). NASA's Solar Dynamics Observatory caught Comet Lovejoy emerging from its scorching close encounter with the sun. [Entrance movie:Quicktime (22 MB), m4v (0.8 MB)] [Exit movie:Quicktime (26 MB), m4v (0.8 MB)]
In the SDO movies, the comet's tail wriggles wildly as the comet plunges through the sun's hot atmosphere only 120,000 km above the stellar surface. This could be a sign that the comet was buffeted by plasma waves coursing through the corona. Or perhaps the tail was bouncing back and forth off great magnetic loops known to permeate the sun's atmosphere. No one knows.
"This is all new," says Battams. "SDO is giving us our first look1 at comets travelling through the sun's atmosphere. How the two interact is cutting-edge research." “The motions of the comet material in the sun’s magnetic field are just fascinating,” adds SDO project scientist Dean Pesnell of the Goddard Space Flight Center. “The abrupt changes in direction reminded me of how the solar wind affected the tail of Comet Encke in 2007 (movie).”
Comet Lovejoy was discovered on Dec. 2, 2011, by amateur astronomer Terry Lovejoy of Australia. Researchers quickly realized that the new find was a member of the Kreutz family of sungrazing comets. Named after the German astronomer Heinrich Kreutz, who first studied them, Kreutz sungrazers are fragments of a single giant comet that broke apart back in the 12th century (probably the Great Comet of 1106). Kreutz sungrazers are typically small (~10 meters wide) and numerous. The Solar and Heliospheric Observatory sees one falling into the sun every few days.
At the time of discovery, Comet Lovejoy appeared to be at least ten times larger than the usual Kreutz sungrazer, somewhere in the in the 100 to 200 meter range. In light of today's events, researchers are re-thinking those numbers. This coronagraph image from the Solar and Heliospheric Observatory shows Comet Lovejoy receding from the sun after its close encounter. The horizontal lines through the comet's nucleus are digital artifacts caused by saturation of the detector; Lovejoy that that bright! [movie]
"I'd guess the comet's core must have been at least 500 meters in diameter; otherwise it couldn't have survived so much solar heating," says Matthew Knight. "A significant fraction of that mass would have been lost during the encounter. What's left is probably much smaller than the original comet."
SOHO and NASA's twin STEREO probes are monitoring the comet as it recedes from the sun. It is still very bright and should remain in range of the spacecrafts' cameras for several days to come. Researchers will be watching closely, because there a good chance for more surprises.
"There is still a possibility that Comet Lovejoy will start to fragment," continues Battams. "It’s been through a tremendously traumatic event; structurally, it could be extremely weak. On the other hand, it could hold itself together and disappear back into the recesses of the solar system."
"It's hard to say," agrees Knight. "There has been so little work on what happens to sungrazing comets after perihelion (closest approach). This continues to be fascinating.”
Dec. 14, 2011: On Nov. 26th, Curiosity blasted off from Cape Canaveral atop an Atlas 5 rocket. Riding a plume of fire through the blue Florida sky, the car-sized rover began a nine month journey to search for signs of life Mars.
Meanwhile, 93 million miles away, a second lesser-noticed Mars launch was underway. Around the time that Curiosity’s rocket was breaking the bonds of Earth, a filament of magnetism erupted from the sun, hurling a billion-ton cloud of plasma (a “CME”) toward the Red Planet. The two Mars launches of Nov. 26, 2011. On the left, a solar explosion hurls a CME toward the Red Planet (Credit: SOHO). On the right, the Mars Science Lab or "Curiosity" lifts off from Cape Canaveral. (Credit: Howard Eskildsen of Titusville, FL)
There was no danger of a collision—Mars rover vs. solar storm. Racing forward at 2 million mph, the plasma cloud outpaced Curiosity’s rocket by a wide margin.
Next time could be different, however. With solar activity on the upswing (Solar Max is expected in 2012-2013) it’s only a matter of time before a CME engulfs the Mars-bound rover.
That suits some researchers just fine. As Don Hassler of the Southwest Research Institute (SWRI) in Boulder, Colorado, explains, “We look forward to such encounters because Curiosity is equipped to study solar storms." Hassler is the principal investigator for Curiosity's Radiation Assessment Detector--"RAD" for short. The instrument, developed at SWRI and Christian Albrechts University in Kiel, Germany, counts cosmic rays, neutrons, protons and other particles over a wide range of energies. Tucked into the left front corner of the rover, RAD is about the size of a coffee can and weighs only three pounds, but has capabilities of Earth-bound instruments nearly 10 times its size.
Encounters with CMEs pose little danger to Curiosity. By the time a CME reaches the Earth-Mars expanse, it is spread so thin that it cannot truly buffet the spacecraft. Nevertheless, RAD can sense what happens as the CME passes by.
"RAD will be able to detect energetic particles accelerated by shock waves in some CMEs1," says Arik Posner of NASA’s Heliophysics Division in Washington DC. "This could give us new insights into the inner physics of these giant clouds."
There’s more to this, however, than pure heliophysics. Future human astronauts will directly benefit from RAD’s measurements during the cruise phase. A photo of the Radiation Assessment Detector (RAD) in the laboratory. [more]
"Curiosity is nestled inside its spacecraft, just like a real astronaut would be," notes Frank Cucinotta, Chief Scientist for NASA’s Space Radiation Program at the Johnson Space Center. "RAD will give us an idea of the kind of radiation a human can expect to absorb during a similar trip to Mars."
Of particular interest are secondary particles. Galactic cosmic rays and solar energetic particles hit the walls of the spacecraft, creating an inward spray of even more biologically dangerous neutrons and atomic nuclei. RAD will analyze the spray from the only realistic place to make such measurements—inside the spaceship.
In this way, “RAD is a bridge between the science and exploration sides of NASA,” says Hassler. “The two objectives are equally exciting.”
RAD was activated on Dec. 6th. Of the rover's ten science instruments, it will be the only one active during the cruise to Mars. Daily transmissions to Earth will let Hassler and colleagues monitor what's going on "out there."
"We're very excited about the possibility of more solar storms," he adds.
As important as RAD’s cruise phase measurements are, the instrument’s primary mission doesn’t really begin until it lands on the Red Planet.
Mars has a very thin atmosphere and no global magnetic field to protect it from space radiation. Energetic particles reaching ground level might be dangerous to life--both future human astronauts and extant Martian microbes. RAD will find out how much shielding human explorers need on the surface of Mars. RAD will also help researchers estimate how far below ground a microbe might have to go to reach a radiation “safe zone.”
GEMINID METEOR SHOWER: The Geminid meteor shower peaks on Dec. 13th and 14th. Bright moonlight will interfere with the display, but not obliterate it. Forecasters expect observers with clear skies to see as many as 40 meteors per hour. The best time to look, no matter where you live, is between 10 pm local time on Tuesday, Dec. 13, and sunrise on Wednesday, Dec. 14th. [full story] [meteor radar] [meteor app] [sky map] [Geminid images:#1]
Vesta was discovered over two hundred years ago but, until Dawn, has been seen only as an indistinct blur and considered little more than a large, rocky body. Now the spacecraft's instruments are revealing the true complexity of this ancient world.
"We're seeing enormous mountains, valleys, hills, cliffs, troughs, ridges, craters of all sizes, and plains," says Chris Russell, Dawn principal investigator from UCLA. "Vestais not a simple ball of rock. This is a world with a rich geochemical history. It has quite a story to tell!" Like Earth and other terrestrial planets, Vesta has ancient basaltic lava flows on the surface and a large iron core. It also has tectonic features, troughs, ridges, cliffs, hills and a giant mountain. False colors in this montage represent different rock and mineral types. [more] [video]
In fact, the asteroid is so complex that Russell and members of his team are calling it the "smallest terrestrial planet."
Vesta has an iron core, notes Russell, and its surface features indicate that the asteroid is "differentiated" like the terrestrial planets Earth, Mercury, Mars, and Venus. Differentiation is what happens when the interior of an active planet gets hot enough to melt, separating its materials into layers. The light material floats to the top while the heavy elements, such as iron and nickel, sink to the center of the planet.
Researchers believe this process also happened to Vesta.
The story begins about 4.57 billion years ago, when the planets of the Solar System started forming from the primordial solar nebula. As Jupiter gathered itself together, its powerful gravity stirred up the material in the asteroid belt so objects there could no longer coalesce. Vesta was in the process of growing into a full-fledged planet when Jupiter interrupted the process. Like Earth and other terrestrial planets, Vesta is differentiated into layers.
Although Vesta’s growth was stunted, it is still differentiated like a true planet.
"We believe that the Solar System received an extra slug of radioactive aluminum and iron from a nearby supernova explosion at the time Vesta was forming," explains Russell. "These materials decay and give off heat. As the asteroid was gathering material up into a big ball of rock, it was also trapping the heat inside itself."
As Vesta’s core melted, lighter materials rose to the surface, forming volcanoes and mountains and lava flows.
"We think Vesta had volcanoes and flowing lava at one time, although we've not yet found any ancient volcanoes there," says Russell. "We're still looking. Vesta's plains seem similar to Hawaii's surface, which is basaltic lava solidified after flowing onto the surface.
Vesta has so much in common with the terrestrial planets, should it be formally reclassified from "asteroid" to "dwarf planet"?
"That's up to the International Astronomical Union, but at least on the inside, Vesta is doing all the things a planet does."
If anyone asks Russell, he knows how he would vote.
Kepler Confirms First Planet in Habitable Zone of Sun-like Star
Dec 5, 2011: NASA's Kepler mission has confirmed its first planet in the "habitable zone" of a distant sun-like star.
This artist's conception illustrates Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. [larger image]
The newly confirmed planet, Kepler-22b, is about 2.4 times the radius of Earth. Scientists don't yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets1.
The "habitable zone" of a planetary system refers to the band of orbits where liquid water could exist on a planet’s surface. Kepler has recently discovered more than 1,000 new planet candidates. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.
"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington.
Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290 days around a sun-like star resembles that of our world. The planet's host star belongs to the same class as our sun, called G-type, although it is slightly smaller and cooler.
Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or "transit," the stars. Kepler requires at least three transits to verify a signal as a planet.
"Fortune smiled upon us with the detection of this planet," said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. "The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season." This diagram compares our own solar system to Kepler-22, a star system containing the first "habitable zone" planet discovered by NASA's Kepler mission. The habitable zone is the sweet spot around a star where temperatures are right for water to exist in its liquid form. Liquid water is essential for life on Earth. [more]
The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.
Of the 54 habitable zone planet candidates reported in February 2011, Kepler-22b is the first to be confirmed. This milestone will be published in The Astrophysical Journal.
The Kepler team is hosting its inaugural science conference at Ames Dec. 5-9, announcing 1,094 new planet candidate discoveries. Since the last catalog was released in February, the number of planet candidates identified by Kepler has increased by 89 percent and now totals 2,326. Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter.
The findings, based on observations conducted May 2009 to September 2010, show a dramatic increase in the numbers of smaller-size planet candidates. Earth-size and super Earth-size candidates have increased in number by more than 200 and 140 percent since February, respectively. These new data suggest that planets one to four times the size of Earth may be abundant in the galaxy.
So far, there are 48 planet candidates in their star's habitable zone. While this is a decrease from the 54 reported in February, the Kepler team has applied a stricter definition of what constitutes a habitable zone in the new catalog, to account for the warming effect of atmospheres, which would move the zone away from the star, out to longer orbital periods.
"The tremendous growth in the number of Earth-size candidates tells us that we're honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable," said Natalie Batalha, Kepler deputy science team lead at San Jose State University in San Jose, Calif.
A total lunar eclipse, a close encounter between Mercury and the moon, and a planetary tour de force are just some of the amazing sights skywatchers can see this month. Here are the most exciting skywatching targets for December 2011:
The full Moon of December is usually called the Oak Moon.
In Algonquian it is called Cold Moon. Other names are Frost Moon, Winter Moon, Long Night’s Moon, and Moon Before Yule. In Hindi it is known as Margashirsha Poornima. Its Sinhala (Buddhist) name is Unduvap Poya. The Full Moon rises around sunset and sets around sunrise, the only night in the month when the moon is in the sky all night long. The rest of the month, the moon spends at least some time in the daytime sky.
Saturday, Dec. 17, 7:48 p.m. EST
Last Quarter Moon
The Last or Third Quarter Moon rises around 11 p.m. and sets around noon. It is most easily seen just after sunrise in the southern sky.
Saturday, Dec. 24, 1:06 p.m. EST
The Moon is not visible on the date of New Moon because it is too close to the sun, but can be seen low in the east as a narrow crescent a morning or two before, just before sunrise. It is visible low in the west an evening or two after New Moon.
Saturday, Dec. 10, dawn
Total Lunar Eclipse
A total lunar eclipse will be seen in its entirety in eastern Asia, Australia, Oceania, and Alaska. The moon will rise eclipsed in the early evening in Europe and Africa, and set eclipsed just before dawn in western North America. The graphic shows how it will look just before dawn in central California, surrounded by first magnitude stars. [Photos: The Long Total Lunar Eclipse of June 2011]
A total lunar eclipse will occur at dawn on Saturday, Dec. 10, 2011. The graphic shows how it will look just before dawn in central California, surrounded by first magnitude stars. CREDIT: Starry Night SoftwareView full size image
Thursday, Dec. 22, 12:30 a.m. EST
It will be winter solstice in the northern hemisphere, and summer solstice in the southern hemisphere. On this day, the sun is at its farthest southern declination, and is 6.5 degrees away from the center of the Milky Way. This is exactly the same alignment as will occur on Dec. 21 2012, yet no catastrophes have been predicted for this year, just as none will occur next year. Because of the extreme difference in brightness between the sun and the Milky Way, this alignment is observable only in a computer simulation.
The solstice will occur Thursday, Dec. 22, 2011. On this day, the sun is at its farthest southern declination, and is 6.5 degrees away from the center of the Milky Way. CREDIT: Starry Night SoftwareView full size image
Thursday, Dec. 22, and Friday, Dec. 23, dawn
Close encounter between Mercury and the moon
The moon will be just to the right of Mercury on Dec. 22 (shown here) and just to the left of Mercury on Dec. 23.
On Thursday, Dec. 22, 2011, the moon will be just to the right of Mercury. CREDIT: Starry Night SoftwareView full size image
Tuesday, Dec. 27, 10:52 p.m. EST
Jupiter satellite show
Three of Jupiter’s moons will put on a fine show tonight. Callisto will be in an unusual position due south of the planet because of the extreme tilt of the plane of Jupiter's moons this year.
Europa will be moving off from in front of Jupiter on one limb while its shadow begins a transit on the opposite limb. Ganymede, well off to the right, will still be casting its shadow just below Europa. Finally, the Great Red Spot will be perfectly placed right in the middle of all this.
Three of Jupiter’s moons will be visible on Tuesday, Dec. 27, 2011. CREDIT: Starry Night SoftwareView full size image
Mercury is well placed in the eastern sky before sunrise for the last half of the month.
Venus is low in the evening sky after sunset all month. The waxing crescent moon will pass close to Venus on Monday, Dec. 26 and Tuesday, Dec. 27.
Mars spends all of December in the morning sky in Leo. It now outshines nearby star Regulus and grows from 7 arcseconds wide to 9 arcseconds during the month, large enough to reveal its polar cap and dark surface markings in a 6-inch (150-mm) telescope. It is now approaching magnitude 0, making it one of the brightest objects in the morning sky.
Jupiter continues to be well placed in the evening sky all month on the border between the constellations Aries and Pisces. Jupiter and Venus are the brightest objects in the night sky other than the moon.
Saturn is visible before dawn in the eastern sky. It now shines brighter than nearby star Spica.
Uranus is well placed in the early evening in Pisces all month.
Neptune is well placed in the early evening in Aquarius all month.