Friday, November 26, 2010

Saturn Moon Has Oxygen Atmosphere

An oxygen atmosphere has been found on Saturn's second largest moon, Rhea, astronomers announced Thursday—but don't hold your breath for colonization opportunities. For one thing, the 932-mile-wide, ice-covered moon is more than 932 million miles from Earth. For another, the average surface temperature is -292 degrees Fahrenheit. Still, the discovery implies that worlds with oxygen-filled air may not be so unusual in the cosmos.

And at less than 62 miles thick, the newfound oxygen layer is so thin that, at Earthlike temperatures and pressure, Rhea's entire atmosphere would fit in a single midsize building. At about 327,000 miles from Saturn, Rhea orbits inside the planet's magnetic field. Rhea's oxygen atmosphere is believed to be maintained by the ongoing chemical breakdown of water ice on the moon's surface, driven by radiation from Saturn's magnetosphere.

Tuesday, November 23, 2010

Brian Marsden, Tracker of Comets, Dies at 73

Brian G. Marsden, who for decades was the go-to guy for thousands of stargazers when a comet or an asteroid would streak through the heavens — or, by his calculations, was supposed to — died Thursday in Burlington, Mass. From 1968 to 2000, Dr. Marsden was director of the archaic-sounding Central Bureau for Astronomical Telegrams, which was founded by the International Astronomical Union in 1920.

In that capacity he was, in effect, the world’s central source of information about the latest astronomical discoveries. As Sky & Telescope magazine said in 1980: “Marsden presides over an international network, including both professional and amateur astronomers, that sends word of the latest discovery winging over the telegraph wires in time for observatories on the other side of the world to catch a nova still brightening, or a new-found comet. As the official certifier of such discoveries, Marsden is probably quoted in newspapers more frequently than any other astronomer in the world.”

Powerful Explosions Can Leave Black Hole Graves

When certain stars collapse, they release overwhelming blasts of energy called gamma-ray bursts – the most powerful explosion in the universe. But the cosmic leftovers of these violent outbursts have been a mystery — until now. Two new studies suggest that when gamma-ray bursts explode, some can leave behind black holes like cosmic gravestones, while others may end up as spinning neutron stars.

Gamma-ray bursts occur when some massive stars reach the ends of their lives and exhaust their supplies of fuel for nuclear fusion in their cores. Without the pressure from fusion pushing outward, gravity wins. In the ensuing dramatic collapse, a flood of high-energy, short-wavelength gamma-ray light is released. They are sometimes associated with supernovas – another explosive way stars die – but are separate events. One of the new studies found that for a certain class of the brightest, most powerful gamma-ray bursts, only black holes will do.

Thursday, November 18, 2010

Full Moons Electrified by Earth's Magnetic "Tail"

Earth's magnetic field creates a protective bubble known as the magnetosphere, which surrounds the planet and shields us from solar wind. The moon's electric charge was discovered by the Kayuga (Selene) lunar orbiter, managed by the Japan Aerospace Exploration Agency (JAXA). Scientists are now mining the data sent back by the craft's imagers and instruments, which recorded that relatively high-energy electrons are being absorbed by the lunar surface when the moon is full.

The result is an electrostatic charge building up in the first few meters above the lunar surface once a month, creating a temporary electric field. Based on Kaguya's data, the team says this lunar electrification happens when the moon passes through the region of the magnetosphere called the plasma sheet, which runs down the middle of Earth's magnetotail. Since the moon has no global magnetic field of its own, its surface remains exposed to the trapped solar particles that are gyrating inside the plasma sheet.

Wednesday, November 17, 2010

Allan Sandage, Astronomer, Dies at 84

Allan R. Sandage, who spent his life measuring the universe, becoming the most influential astronomer of his generation, died Saturday at his home in San Gabriel, Calif. He was 84. The cause was pancreatic cancer, according to an announcement by the Carnegie Observatories, where he had spent his whole professional career.

Over more than six decades, Dr. Sandage was like one of those giant galaxies that sit at the center of a cluster of galaxies, dominating cosmic weather. He wrote more than 500 papers, ranging across the cosmos, covering the evolution and behavior of stars, the birth of the Milky Way galaxy, the age of the universe and the discovery of the first quasar, not to mention the Hubble constant, a famously contested number that measures the rate of expansion of the universe.

Best Time to See the Leonid Meteor Shower

The Leonid meteor shower of 2010 is peaking this week and the best time to see the sky show is now. The annual Leonids should be at their best through Nov. 18, according to skywatching experts. Avid meteor gazers graced with clear skies may see between 15 and 20 meteors per hour.

Skywatchers should look toward the constellation Leo in the eastern sky to see "shooting stars" from the Leonids, which appear to radiate out of the constellation. The best time to try to see the Leonids are in the last two or three hours before sunrise, when the moon has set.

Tuesday, November 16, 2010

Baby Photos of a Black Hole

After watching a nearby star that exploded into a supernova in 1979, astronomers now believe the star's death wasn't an ordinary one. The star's explosion was big enough to cause a black hole to develop in its wake. They think it's a black hole because they see something steadily consuming the gassy remnants of the exploded star, which is a telltale sign of a black hole. It sucks up everything in sight.

And in this case it's a lot. In the past 30 years since this star exploded, this baby black hole has eaten about the equivalent of the Earth in mass, which is about as big as black hole appetites can get, said Harvard astrophysicist Avi Loeb. He's co-author of a new paper in the journal New Astronomy and he discussed the findings at a NASA news conference Monday.

Monday, November 15, 2010

Danish Astronomer's Remains Exhumed in Prague

Astronomer Tycho Brahe uncovered some of the mysteries of the universe in the 16th century — and now modern-day scientists are delving into the mystery of his sudden death. On Monday, an international team of scientists opened his tomb in the Church of Our Lady Before Tyn near Prague's Old Town Square, where Brahe has been buried since 1601. After eight hours of work, they lifted from the tomb a tin box like a child's coffin in which Brahe's remains were placed after the only previous exhumation, in 1901.

Brahe's extraordinarily accurate stellar and planetary observations, which helped lay the foundations of early modern astronomy, are well documented but the circumstances surrounding his death at age 54 are murky. It has been long thought that he died of a bladder infection, but tests conducted in 1996 in Sweden, and later in Denmark, on samples of his mustache and hair obtained in the 1901 exhumation, showed unusually high levels of mercury. That led to a theory of mercury poisoning — even, possibly, murder.

Friday, November 12, 2010

Formation of Bulge on Far Side of Moon Explained

A bulge of elevated topography on the far side of the moon -- known as the lunar far side highlands -- has defied explanation for decades. But a new study led by researchers at the University of California, Santa Cruz, shows that the highlands may be the result of tidal forces acting early in the moon's history when its solid outer crust floated on an ocean of liquid rock.

The paper describes a process for formation of the lunar highlands that involves tidal heating of the moon's crust about 4.4 billion years ago. At that time, not long after the moon's formation, the crust was decoupled from the mantle below it by an intervening ocean of magma. As a result, the gravitational pull of the Earth caused tidal flexing and heating of the crust. At the polar regions, where the flexing and heating was greatest, the crust became thinner, while the thickest crust would have formed in the regions in line with the Earth.

Hubble's Successor May Be Delayed for Years

The James Webb Space Telescope, already billions of dollars over budget and several years behind schedule, will be delayed by at least another year, to 2015, and will cost $1.5 billion more than current estimates, an independent review panel says. Costs and delays could escalate even further if funding for the project does not increase substantially in 2011 and 2012.

Cost estimates have risen for the ambitious mission, billed as the Hubble Space Telescope's heir, since the idea for the telescope was floated in the late 1980s. At that time, proponents estimated that the project would cost about $1 billion. In 2008, NASA officials upped that amount to $5 billion. Though Congress approved all requested funding for JWST in 2009 and 2010, NASA came back asking for an additional $95 million and $20 million in each respective year.

Thursday, November 11, 2010

Mysterious Structures Balloon from Galaxy's Core

Two huge bubbles that emit gamma rays have been found billowing from the center of the Milky Way galaxy, astronomers have announced. The previously unseen structures, detected by NASA's Fermi Gamma-ray Space Telescope, extend 25,000 light-years north and south from the galactic core. For now the source of all that energy is unclear, said study co-author Doug Finkbeiner, an associate professor of astronomy at the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA.

The newfound bubbles are made of hot, charged gas that's releasing the same amount of energy as a hundred thousand exploding stars. One possible answer is that the gamma-ray bubbles are evidence of an ancient burst of star formation at the center of the galaxy. If a huge cluster of massive stars formed millions of years ago, the giants could now be dying together, creating an outbreak of supernovae. "Another hypothesis, which is perhaps even more dramatic, is that the [mostly dormant] black hole at the center of the galaxy is active for a little bit," he said.

Friday, November 5, 2010

Deep Impact Spacecraft Flies by Small Comet

A NASA spacecraft sped past a small comet Thursday, beaming pictures back to Earth that gave scientists a rare close-up view of its center. Mission controllers burst into applause upon seeing images from the flyby that revealed a peanut-shaped comet belching jets of poisonous gases. The close encounter occurred 13 million miles from Earth when the Deep Impact craft, hurtling through space, flew within 435 miles of comet Hartley 2. It's only the fifth time that a comet's core has been viewed up close.

Scientists are interested in comets because they're icy leftovers from the formation of the solar system about 4.5 billion years ago. Studying them could provide clues to how Earth and the planets formed and evolved. Thursday's flyby is actually an encore mission for Deep Impact. It set off cosmic fireworks on July 4, 2005, when it fired a copper probe that crashed into comet Tempel 1. The high-speed collision spewed a cloud of debris into space, giving scientists their first peek of the interior.

Tuesday, November 2, 2010

Robot's Space Debut "Giant Leap for Tinmankind"

Space is about to get its first humanoid from planet Earth. Robonaut 2 — affectionately known as R2 — is hitching a one-way ride to the International Space Station this week aboard the final flight of space shuttle Discovery. It's the first humanoid robot ever bound for space, a $2.5 million mechanical and electrical marvel that NASA hopes one day will assist flesh-and-bone astronauts in orbit.

Imagine, its creators say, a future where Robonaut could take over space station cleaning duties; spend hours outside in the extreme heat and cold, patiently holding tools for spacewalking astronauts; and handle emergencies like toxic leaks or fires. For now, R2 — a collaboration between NASA and General Motors — exists only from the waist up. It measures 3 feet 4 inches tall and weighs 330 pounds. Each arm is 2 feet 8 inches long. Legs are still in the works.