Blogs / 80beats

In the wee hours of Tuesday morning, 2009’s edition of the Leonid meteor shower will reach peak viewing time for sky-watchers in North America. Star gazers who lift their eyes to the heavens between 2 a.m. and 4 a.m. will likely be rewarded with a good show of “shooting stars.” A second, briefer, but very intense outburst is expected about 12 hours later — during the early-morning hours of November 18th in Asia [Sky & Telescope]. But that probably won’t last long enough for North Americans to see it when night returns here.

Like other meteor showers, such as the Perseids and the Orionids, the Leonids happen when Earth plows through a trail of debris left in the wake of a comet orbiting the sun [National Geographic News]. This comet, called Tempel-Tuttle, swings through the inner solar system about every 33 years, and last did so in 1998.

On special occasions we’ll pass directly through an unusually concentrated dust trail, or filament, which can spark a meteor storm resulting in thousands of meteors per hour. That indeed is what transpired in 1999, 2001 and 2002 [MSNBC]. This year won’t supply such a bonanza, astronomers predict, but we will see more meteors than average: probably 30 to 300 per hour, depending on where you are.

To get the most spectacular views, of course, you’ll have to venture away from city lights. But you won’t need to haul a telescope. For meteor showers, the naked eye is enough to enjoy the show.

Related Content:
Bad Astronomy: Will the Leonids Roar in 2009?
Bad Astronomy: Leonids ROCK! (Check out the link to the amazing Mt. Hopkins video of a Leonid shower)
80beats: Tonight’s Orionid Meteor Shower Should Be a Beauty, from October
80beats: Study: 20-Million-Year Meteor Shower Turned Earth Warm & Wet

Image: iStockphoto

This dazzling picture of our planet, all dark but the cerulean sliver of the South Pole, was a long time coming.

Rosetta, a European Space Agency craft, captured this view of the crescent Earth from about 400,000 miles away. The unmanned probe, which is busy chasing comets, was making its third flypast since it was launched in 2004. The close approach gave it a speed boost to send it on its mission to Comet Churyumov-Gerasimenko [Scientific American].

This will be Rosetta’s final visit to its home planet, having already executed a flyby of the asteroid Steins, a gravity assist with Mars, and two previous swoops past the Earth, gathering images all the way. Now it’s off to the comet.

Rosetta is carrying a fridge-sized lab, Philae, that it will send down to the comet. Anchored by tiny hooks, Philae will look for clues about the Solar System’s primal past, exploring a theory that comets are primitive rubble left over from the making of the Solar System [AFP].

While we bid safe travels to Rosetta, it could tell us something about the Earth itself on this final pass. Scientists notice unexpected behavior in spacecraft that make gravitational assists with our planet: Rosetta itself behaved exactly as expected in 2007 flyby but picked up an extra speed boost of 1.8 millimeters per second on its initial maneuver in 2005, leading some mission scientists to speculate that the Earth’s rotation might be distorting space-time more than they thought. “Some studies have looked for answers in new interpretations of current physics. If this proves correct, it would be absolutely groundbreaking news” [MSNBC], says Rosetta flight dynamics specialist Trevor Morley.

Related Content:
Bad Astronomy: Rosetta Takes Some Home Pictures
Bad Astronomy: Earth From Rosetta, from its 2007 flyby.
Bad Astronomy: Rosetta Swings By Mars!
DISCOVER: To Catch a Comet, which anticipated Rosetta, Stardust, and other comet-chasing missions.

Image: ESA

Tonight, in the wee hours, dedicated star watchers and people just looking for a good celestial show will turn their faces up to the heavens to watch the annual Orionid meteor shower. The Orionids are so named because the meteors appear to radiate from near the constellation Orion, aka the Hunter. This easily spotted constellation “kind of looks like an hourglass with a very recognizable belt of stars,” said astronomer Mark Hammergren [National Geographic News].

The “shooting stars” are really tiny fragments of debris left behind in space by Halley’s Comet, which loops through the inner solar system every 76 years and leaves a trail of dust in its wake. Most fragments are tiny, only about the size of a grain of sand–but they still go out in a blaze of glory as they vaporize in the Earth’s upper atmosphere. The best time to watch will be between 1 a.m. and dawn local time Wednesday morning, regardless of your location. That’s when the patch of Earth you are standing on is barreling headlong into space on Earth’s orbital track, and meteors get scooped up like bugs on a windshield [SPACE.com]. Tonight’s star gazers will benefit from a dark, moonless sky.

NASA scientist Bill Cooke says the Orionids have been strong in recent years. “Since 2006, the Orionids have been one of the best showers of the year, with counts of 60 or more meteors per hour” [SPACE.com].

Related Content:
80beats: For the World’s Best Stargazing, Head to Antarctica
80beats: Perseid Meteor Shower Should Dazzle Despite a Bright Moon
DISCOVER: 20 Things You Didn’t Know About… Meteors

Image: iStockphoto

According to a theory proposed in 2007, the explosion of a comet over North America killed off the Clovis people and many of the continent’s largest mammals nearly 13,000 years ago. Not so fast, says a new study published in the Proceedings of the National Academy of Sciences, fueling a WWE-style stare down between the opposing camps.

The new report explains that archaeologists have examined sediments at seven Clovis-age sites across the United States, and found that the concentration of magnetic debris was insufficient to confirm an extraterrestrial impact at that time [Nature News]. The original theory’s evidence came from magnetic microspherules, or cosmic debris, discovered in sediments at 25 locations. However, one of the new study’s authors, Todd Surovell, said that even after 18 months of sedimentary analysis and hundreds of hours peering into a microscope, he could find no evidence of microspherules to support the the exploding comet theory. Snap.

(more…)

The mighty planet Jupiter has 63 official moons, but it turns out there’s always room for more. Researchers used computer models to map the past trajectory of the comet 147P/Kushida-Muramatsu, and determined that for about 12 years it circled Jupiter as a temporary moon. At the ongoing European Planetary Science Congress, astronomers declared that the comet completed two complete orbits of the gas giant, and remained in orbit from 1949 to 1961.

The 1,300-foot-wide comet had a happier fate than other comets that got too close to Jupiter, and were dragged all the way in for a crash landing. Only one temporary satellite has been observed falling prey to a planet’s pull: comet Shoemaker-Levy 9, which broke apart and crashed into Jupiter in 1994…. Unlike [Shoemaker-Levy], comet Kushida-Muramatsu eventually escaped Jupiter’s gravity. It currently circles the sun in the solar system’s asteroid belt, between the orbits of Mars and Jupiter [National Geographic News].

(more…)

One of the building blocks of life has been found on a comet hurtling through the solar system, adding evidence to the theory that earthly biology began when comets and meteors bombarded our young planet and seeded it with the precursors of life. The amino acid, glycine, was found in a sample returned by the space probe Stardust that buzzed by the comet Wild 2 in 2004. The probe swept up particles fizzing off the object’s surface as it passed some 240km (149 miles) from the comet’s core, or nucleus. These tiny grains, just a few thousandths or a millimetre in size, were then returned to Earth in 2006 in a sealed capsule [BBC News].

Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons – a process that can take place on Earth or in space [New Scientist].

(more…)

Space aficionados are getting ready for the Perseid meteor shower, a show of shooting stars that occurs each year in the middle of August. This year, the event is expected to produce more shooting stars than usual; however, they may be slightly harder to see because of the moon’s unusual brightness due to the phase it will be in during the showers.

The Perseid Meteor Shower, which consists of debris from the Swift-Tuttle comet, became active on July 17, but have largely been so disperse and faint to see. [A] noticeable upswing in Perseid activity traditionally begins during the second week of August, leading up to their peak. They are typically fast, bright and occasionally leave persistent trains. And every once in a while, a Perseid fireball will blaze forth, bright enough to be quite spectacular and more than capable to attract attention even in bright moonlight [Space.com]. Like other meteor showers, Perseid’s fiery show is the result of particles disintegrating as they speed into the Earth’s atmosphere.

In other years, stargazers have been able to see up to 200 meteors per hour. But because the moon will be at last quarter the night of Aug. 13 and it will be at a rather bright waning gibbous phase a night or two earlier, seriously hampering observation of the peak of the Perseids, predicted to occur late on the nights of Aug. 11 and 12. [Space.com].  Still, although the moon’s brightness could hamper visibility, astronomers say the meteor shower should still be exciting to watch. 

(more…)

A comet from the deep space far beyond Pluto probably won’t smash into the Earth and obliterate all life, reassuring researchers said today. New calculations have determined that most extinction events that have occurred over our planet’s history probably weren’t caused by killer comet showers, which bodes well for the future, too. The findings are both welcome and well-timed since only last week an object dramatically smashed into Jupiter; many researchers believe the culprit was a comet.

In the new study, published in Science, researchers focused on long-period comets, which are among the wild cards in a thick deck of cosmic threats. In contrast with short-period comets, such as Comet Halley and Comet Tempel-Tuttle, long-period comets trace insanely eccentric orbits that range out beyond Neptune, Pluto and the Kuiper Belt to a little-understood region on the solar system’s edge known as the Oort Cloud [MSNBC]. The Oort cloud, which contains billions of small, icy objects, may extend from about 93 billion miles from the sun to as far as 9 trillion miles away.

(more…)

Jupiter is sporting a new, Earth-sized scar near its south pole, and NASA has confirmed that the gas giant was thumped by a massive impact over the past few days. The discovery was made Sunday night by a Australian computer programmer who uses his spare time to stargaze with his backyard telescope, and today NASA declared that the dark spot is definitely not a weather system, and is indeed evidence of a collision. It’s not yet known exactly what smacked into Jupiter; astronomers say it could have been an unknown comet, or a stray piece of ice.

This is only the second time such an impact has been observed. The first was almost exactly 15 years ago, when more than 20 fragments of comet Shoemaker-Levy 9 collided with the gas giant. “This has all the hallmarks of an impact event, very similar to Shoemaker-Levy 9,” said Leigh Fletcher, an astronomer at NASA’s Jet Propulsion Lab…. “We’re all extremely excited” [New Scientist].

(more…)

As of tomorrow, 101 years will have passed since the Tunguska Event, the mysterious explosion that flattened 800 square miles of Siberian forest. Just in time for the anniversary researchers have come up with yet another explanation for what may have caused the baffling blast. Previously, researchers best hypothesis was that a meteor struck the forest, but scientific expeditions failed to turn up an impact crater or any fragments of rock. The new hypothesis, which will be published in the journal Geophysical Research Letters, suggests that the Earth was hit by the icy core of a comet, which exploded in the atmosphere.

Researchers say that a comet strike would have released huge volumes of water vapour at very high altitude, creating highly reflective clouds that may explain why the sky was lit up for days after the collision, with people as far away as London saying that they could read newspapers outdoors at midnight, the scientists said [The Independent]. In an unusual twist, the evidence for the new theory comes from studies of the water vapor exhaust created by space shuttle launches.

(more…)

Minuscule diamond fragments found in a sediment layer dating from thousands of years ago are bolstering the theory that a catastrophic comet impact wiped out many forms of life in North America, including what are thought to have been the first human settlers of the continent, the so-called Clovis people. The nano-diamonds are buried at a level that corresponds to the beginning 12,900 years ago of the Younger Dryas, a 1,300-year-long cold spell during which North American mammoths, saber-toothed cats, camels and giant sloths became extinct. The Clovis culture of American Indians also appears to have fallen apart during this time [Reuters].

The new study adds evidence to the controversial theory, but some skeptics are not convinced. “The whole thing still does not make sense, and there are lots of contradictions,” said Christian Koeberl, a professor of geological sciences…. His chief reservation is that there is no crater. “A body of this size does not just blow up without a trace in the atmosphere,” Dr. Koeberl said. “Physics won’t have it” [The New York Times]. In reply, supporters of the theory say that some of the comet fragments may have exploded in midair, while others may have hit an ice sheet that was several miles thick, lessening the possibility of a crater forming.

(more…)

A supernova first observed in the 16th century by Danish astronomer Tycho Brahe has been sighted again, astronomers report. Brahe observed its direct light but “light echoes” from the supernova that took a long detour around the universe have finally made it to Earth and have been captured by the Subaru Telescope in Hawaii. The new observations confirm that the supernova was the explosion of a white dwarf star. “Using light echoes in supernova remnants is time-traveling in a way, in that it allows us to go back hundreds of years to observe the first light from a supernova event,” said Tomonori Usuda, lead project astronomer at Subaru [Space.com].

In November 1572, Brahe noted a new shimmer in the night sky and thought it was the birth of a new star. But the shimmer disappeared 16 months later and some claimed it was a comet. Only in the early 20th century did astronomers understand that the fleeting brightness was a supernova and represented not the birth but the death throes of a star. The direct light from the supernova swept past Earth long ago. But some of it struck dust clouds in deep space, causing them to brighten [AP]. These light echoes are what astronomers have now captured and reported in Nature [subscription required]. “What we have essentially done here is to use interstellar dust as a kind of a mirror,” says [co-author] Oliver Krause [Nature News].

(more…)

Researchers have gotten a close look at a lunar crater that was thought to hold “skating rinks” of ice, and have reached the disappointing conclusion that the crater does not have visible patches of water ice after all. New images from the Japanese lunar orbiter, Kaguya, reveal no traces of ice in the Shackleton crater, a cold and shadowy place near the moon’s south pole. Ice would be vital for future colonies on the Moon, providing drinking water for astronauts and hydrogen fuel for their vehicles [New Scientist].

Researchers had high hopes for the Shackleton crater because it never receives direct sunlight. The theory was that if comets have landed there (and, given the craters’ ages, the odds are that several will have), some of the ice carried by such dirty celestial snowballs might be preserved in the permanent shadow cast by the craters’ walls [The Economist]. Then NASA’s 1998 Lunar Prospector detected an excess of hydrogen at the moon’s poles, which researchers thought indicated the presence of water ice.

(more…)

In between Mars and Jupiter, the spacecraft Rosetta buzzed by an asteroid on Friday and snapped photos of the chunk of rock as it hurtled through space. The European Space Agency’s spacecraft flew to within 500 miles of the Steins asteroid, getting a close-up view of the diamond-shaped Steins asteroid, a gray, 3-mile (5-km) wide rock that appears in images as a pock-marked [rock] with multiple craters that ultimately will help determine its age [SPACE.com].

Researchers hope that the Rosetta’s observations of the asteroid will shed light on the processes that shaped our solar system. The rocks are often referred to as “space rubble” because they represent the leftovers that were never incorporated into planets when the Solar System formed 4.6 billion years ago. As with comets, they may contain very primitive materials that have not undergone the constant recycling experienced by, for example, Earth rocks. Rosetta data should therefore help researchers understand better how our local space environment has evolved over time [BBC News].

(more…)

Astronomers have spotted an icy object near Neptune that they say hails from the distant Oort Cloud, the distant reservoir of asteroids that encircles the solar system out beyond the orbit of Pluto. The object, at least 30 miles wide, is on the return leg of a 22,500-year journey around the sun, astronomers announced today [SPACE.com].

The new object is about 60 miles in diameter. “It’s basically a comet, but it never gets close enough to the Sun to develop a long, bright tail of evaporated gas and dust,” [lead researcher Andrew] Becker said in a statement [Reuters]. Researchers say the newly discovered voyager, which is currently going by the unromantic name 2006 SQ372, is the first object ever sighted from the inner Oort Cloud, a region that astronomers know very little about.

(more…)