Wednesday, July 20, 2011

NEOWISE Finds Comet Hartley 2 Leaving an "Irregular" Trail

According to NASA's NEOWISE program, which hunts for comets and asteroids (part of WISE), astronomers have noticed that Comet Hartley 2 is different from other comets. Of course, there are always misfits, but the comet is peculiar.

NEOWISE has found that Hartley leaves a 'bumpy' trail as it orbits the sun, dotting the celestial landscape with grains as big as golf balls. "We were surprised that carbon dioxide plays a significant role in comet Hartley 2's activity when it's farther away from the sun," said James Bauer, the lead author of a new paper on the result in the Astrophysical Journal.

So, it turns out to be that the comet emits carbon dioxide, still orbiting at 2.3 AU from the sun. An astronomical unit (AU) is a common measurement used in relatively close objects (like asteroids and comets). It is the 93 million miles, or the distance between the earth and sun. Hopefully, as Comet Hartley 2 continues orbiting, NEOWISE will be able to obtain more information about its "irregular" tail.

Here, you can distinguish the tail, but not the particles.

1 comment:

  1. Here's the latest info from SOHO (July 29, 11)

    On Nov. 4, 2010, NASA's EPOXI spacecraft came within 450 miles of Comet Hartley 2, a small comet not even a mile in diameter, which takes about six and a half years to orbit the sun. Designated officially as 103P/Hartley 2, the comet thus became the fifth for which scientists have collected close-up images.

    But the comet was also observed from another spacecraft: the Solar and Heliospheric Observer (SOHO), better known for its observations of the sun. Together, the two returned data about what appears to be an irregular comet, belching chunks of ice and losing water at a surprisingly fast pace.

    "By combining EPOXI's direct imaging with several months of SOHO data, we had a rare chance to see a comet in the process of shedding off large amounts of water," says Michael Combi, a space scientist at the University of Michigan in Ann Arbor, Mich., who wrote about his findings in a June 10, 2011 issue of the Astrophysical Journal Letters. "Comets always lose water as they heat up during the approach to the sun, but this was much more than usual. Something pretty dramatic happened in those weeks."

    Understanding the composition and behavior of comets intrigues scientists because they are some of the first objects that formed around our sun some 4.5 billion years ago and they've evolved little since. These chunks of ice, rock, and frozen gas hold clues to what existed in those early days of the solar system's formation, says Combi. So he uses an instrument onboard SOHO called SWAN -- for Solar Wind ANistropy -- to observe how water streams off of comets.

    SWAN's main job is to map the distribution of hydrogen atoms across the entire sky. This helps those who study the sun's magnetic environment by tracking how the interstellar wind of particles moves through our area of space. But the instrument also can help track comets, which are generally surrounded by an extremely thin atmosphere of water vapor. Under ultraviolet light from the sun, the hydrogen atoms fly off the water molecules at great speed and produce a huge cloud or "coma" of hydrogen. The coma absorbs sunlight and then re-emits it, making it detectable in SWAN images. Observing the clouds can then help determine how much water is being vaporized from the comet over time...

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