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Briefs: Most Distant Naked-Eye Object Detected



    A powerful stellar explosion that’s shattered the record for the most distant naked-eye object visible was detected by NASA's Swift satellite. The gamma-ray burst is also the most intrinsically bright object in the universe ever observed by humans, visible to the naked eye even though its source is half-way across the universe. The afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded. The star, in Boötes, is an estimated 7.5 billion light-years away.

     Three asteroids appear to be among our solar system's oldest objects, apparently formed 4.55 billion years ago. Astronomers, observing the asteroids with infrared and visible-light scopes, measured amounts of colors of light reflected from the surface and found evidence the objects contain bits of material rich with calcium and aluminum.

     An ocean seasoned with the chemical ingredients of life may lie hidden beneath the icy surface of Titan. The size of seasonal wind shifts hints that Titan's crust and core have to be separated by a liquid ocean to allow the atmosphere to move the crust around.

     Mercury's surface is not only peppered with impact craters, but wrinkled with mysterious chains of cliffs. Scientists think the "lobate scarp" cliffs--2 miles high and hundreds of miles long--were created as Mercury’s crust bunched around its shrinking interior. But a new theory suggests rising sheets of hot-mantle rock popped out ridges, helping to create the cliffs.

     For the first time, satellite imagery reveals thick Martian salt deposits scattered across the southern surface, which could be sites of ancient life. Mats of sodium chloride serve as more evidence of Mars' watery past, and briney pools that made them could have been hospitable to life. The salt deposits are thought to be more than 3.5 billion years old.

     Scientists have found the presence of an organic molecule in the atmosphere of an extrasolar planet for the first time. The signature of the molecule methane is in the atmosphere of Jupiter-sized HD 189733b, 63 light-years away in Vulpecula. It orbits closer to its star than Mercury, so is unlikely to support life.

     Scientists have detected water vapor in spinning disks that surround two newly formed stars, where planets are born. They spotted water molecules in disks of dust and gas around DR Tau and AS 205A, 457 and 391 light-years away, one of the few times water vapor has been detected in the inner part of a protoplanetary disk.

    After months of relative quietude, a trio of new sunspot groups have appeared and are growing rapidly.  Solar Cycle 24 is based on sunspots with reversed polarity. Puzzlingly, the sunspots have magnetic polarity consistent with Solar Cycle 23 rather than the new cycle. Some scientists predict Solar Cycle 24 will be intense.

     Saturn's rings are vanishing. The wide-open rings are rapidly narrowing into a thin line, having narrowed considerably in the last year. The Cassini division, a dark gap in the rings, is getting hard to see. As Saturn orbits the Sun, it turns its rings edge-on to Earth once every 14-15 years. Because the rings are so thin, they can disappear when viewed through a small telescope. Saturn's rings will thin until, on Sept. 4, 2009, they vanish.

     Analyses of March 2007 outbursts of two giant plumes on Jupiter suggest internal heat played a major  role in generating them. The plumes moved faster than any Jovian feature and left global streaks of red-cloud particles. Scientists puzzle over whether internal heat or sunlight, or both, powers Jupiter's disturbances and jets. The plumes erupted at middle northern latitudes, 39,150 miles apart, racing at more than 375 mph. Each mushroomed from its initial diameter to 1,245 miles in a day.

     Titan has hundreds of times more natural gas and other liquid hydrocarbons than all of Earth’s known oil and natural-gas reserves. Cassini has mapped 20% of Titan's surface with radar. Hundreds of lakes and seas have been observed, with several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. Dark equatorial dunes contain organics several hundred times larger than Earth's coal reserves.

     Cosmic sprinklers that spurt misty jets from cracks along Enceladus could hint at a vast watery lake beneath the moon’s icy shell. Data reveal there must be water beneath the surface and support the idea that Enceladus’ geysers are the source of Saturn's E-ring. Vapor in the plumes may move at 650-1,100 mph, nearly double the speed needed to escape Enceladus' gravity. The ice grains, however, move much slower. Even with a push from the vapor stream, only 10% of the ice particles have enough energy to break through Enceladus’ gravity. But the crystals are recaptured by Saturn's gravity and coalesce to form the E-ring. A test of water vapor spewing from Enceladus shows it’s gushing with organic molecules. Cassini recorded the highest temperatures detected near tiger stripe-like fissures on the southern pole, raising the possibility of liquid water beneath the exterior. The fissures are -135 degrees near their centers, 63 degrees warmer than previously observed and 200 degrees warmer than the rest of the surface.

     Astronomers have peered into a stellar disk to capture an image of material falling onto what could be a planet in early formation. The image shows a somewhat horseshoe-shaped void in the disk surrounding a young star, AB Aurigae. Within the void, a barely visible bright spot could indicate a developing object 5-37 times Jupiter’s mass. AMNH researcher Ben Oppenheimer said the image shows what's thought to be dust accreting onto the object. He and colleagues blocked out most of the stellar glare by attaching a coronagraph they’d developed to an Air Force telescope on Maui. They also used polarization filters, which show light scattered off the disk.

     How close can a giant planet get to a star before its atmosphere becomes unstable and it’s doomed to catastrophe? A study compared Jupiter to giant exoplanets. Jupiter has a thin, stable atmosphere and orbits the Sun at 5 AUs. Exoplanets, which may orbit 100 times closer to their star, have very expanded atmospheres which boil off into space. A team brought a virtual Jupiter closer to the Sun. At 0.16 AU, it would remain Jupiter-like, with a stable atmosphere. But at 0.14 AU, its atmosphere would suddenly start to expand, become unstable and escape.

     A massive whirling vortex recently discovered over Saturn's south pole has features similar to hurricanes on Earth and unlike anything astronomers have seen. Eyes and eye walls have never been observed anywhere else except on Earth. Saturn's polar vortex is much bigger than any hurricane found on Earth. Its eye alone measures about 2,500 miles in diameter.

     If Martian life existed a few billion years ago, scientists think any plant-like microbes would have left behind a stringy fuzz of fibers. That's because on Earth, researchers have found such ancient fuzz, cellulose, in chunks of salt deposited more than 250 million years ago, the oldest biological substance recovered. The samples survived because of their exceptional sturdiness and due to the salty environment. It killed off bacteria, preventing the cellulose from being chewed up as food.

     Dangerous levels of radiation in space could bar astronauts from a mission to Mars and limit prolonged activity on the Moon. Risk uncertainty means safety margins must remain high, limiting how long astronauts can stay in space. NASA's space radiation-biology research has been hit by recent funding cuts, leading to major gaps in knowledge of radiation health risks. Officials may have to trade off a safe amount of protective material with cutting weight to enter space practically.

     A pair of newfound stars orbit each other so closely that they share material, taking on the appearance of a giant peanut in space. A second freshly examined system has the same two-lobed look. The systems presage a new class of objects. The first system is 13 million light-years away inside a small galaxy called Holmberg IX. Both stars are very bright, yellow stars about 15 times the Sun’s mass. In the orbital cycle, one star moves in front of the other, blocking its light from our vantage point, so astronomers see one star, then two, then one, and so on. The other system is much closer, less than 230,000 light-years away in the Small Magellanic Cloud.

     Images of a tsunami blasting its way through the Sun's lower atmosphere have been taken for the first time. They have helped astronomers revise estimates of the waves' speeds. Speed is more than 1 million kilometers per hour. Oddly, the tsunami seemed to move just as speedily through dense layers as it did through less dense layers. What causes these giant solar waves isn't clear. They’re associated with coronal mass ejections and could be the shock wave that result from them.

     Astronomers have seen two classes of unique galaxies from the early universe. One was galaxies that looked old even when the universe was young, suggesting they were among the first galaxies to form after the universe’s birth. The other group is galaxies dating from the universe’s strongest burst of star formation. The galaxies give away their elderly and inactive status by their reddish color, indicative of old stars. The astronomers saw them as they existed 4 billion years after the Big Bang.

     NASA scientists have identified the smallest, lightest black hole yet found, 3.8 times the mass of our Sun and only 15 miles in diameter. The black hole sits in a binary system in our galaxy, XTE J1650-500, in the southern hemisphere constellation Ara. Some unknown threshold, possibly between 1.7 and 2.7 solar masses, marks the boundary between a star that generates a black hole upon its death and a star that produces a neutron star.

     A shower of shooting stars has been recorded on Mars for the first time. Meteors have been spotted before by Mars rovers, but no device has detected a full shower until now. Just as on Earth, Mars meteor showers can occur when a planet passes through the dusty trail of a comet. Scientists think four times as many comets dust Mars with their tails compared to Earth, as a high proportion of comets are near Jupiter.

     Astronomers have found an embryonic star younger than any seen before. They saw the 100,000-year-old planet 520 light-years away in Taurus. It’s 1% percent as old as a young planet found around the star TW Hydrae last year.

     A new discovery of a middleweight black hole suggests black holes come in all sizes. Astronomers have long debated the existence of middleweight black holes, which could be a missing link in the evolution of the universe's first stellar black holes to supermassive black holes that anchor most major galaxies. The sky's largest star cluster, Omega Centauri, might harbor an elusive intermediate-mass black hole in its center. Researchers suspect missing mass comes from a black hole weighing 40,000 solar masses at the center of the cluster. 

     Astronomers have tracked down the missing starting point of one of the two types of solar wind. The parts of the solar wind that emanate from the Sun's equatorial region originate at the edges of bright regions in the Sun's atmosphere and are released when the magnetic fields of two bright regions link up. The fast solar wind originates from coronal hole regions near the Sun's poles. The slow one flows from the equatorial region.

     Triple black-hole mergers are a real possibility, according to a supercomputer calculation. Astrophysicists used a computer model to predict what would happen if several black holes were to orbit each other. Often the trio would merge into one giant black hole. Last year, astronomers found the first triple quasar. That could be the first observed supermassive black-hole triplet.

     Astronomers have discovered possibly the smallest extrasolar planet yet, a rocky world orbiting a star in Leo. The planet weighs about five Earth masses and is 30 light-years away. Its radius is estimated to be about 50% greater than Earth's radius of 4,000 miles. GJ 436c orbits GJ 436 in 5.2 Earth days, and is thought to complete a revolution about its axis in 4.2 Earth days. Astronomers predicted the small exoplanet due to its gravitational effects on the orbit of an inner planet. Researchers found that for every two orbits of that planet, the new planet completes one.

     One of the best close-ups of the Martian moon Phobos reveals fresh details. The Stickney impact crater is Phobos’ largest feature with a diameter of almost 6 miles. Crater-wall textures come from landslides that formed as materials fell in the weak gravity. Grooves seem to radiate from the crater, although studies have shown the cracks didn’t come from the crater. Some scientists believe the grooves are related to the origin of Stickney, but others speculate they came with space debris from Martian impacts that later pelted Phobos. 

     Clues to the size of ancient asteroids have come from the chemistry of ancient seawater. Impactors may leave behind chemical traces in ancient ocean-floor sediments that can signal their impact and record what was floating around in the seawater in the distant geologic past. A new study has found higher levels of an isotope of the element osmium in ocean sediment layers that correspond to the timing of known impacts. They can also utilize the isotope levels to estimate the size of impactors.

     Astronomers have found the coldest brown dwarf to date. The failed star might represent a new class of objects that are a missing link between planets and stars. The cold brown dwarf floats freely in space, not bound to a star. Its mass is 15-30 times Jupiter’s. It’s about 660 degrees, cooler than any known object in its class. The brown dwarf is about 40 light-years away. The mass of brown dwarfs is usually less than 70 Jupiter masses. The brown dwarf looks much more like a giant planet than known classes of brown dwarfs because of its low temperature and the presence of ammonia. ■