Tag Archives: comet

From Mercury to Morocco, and onward to Yale: a meteorite’s tale

Talk about a precious stone — the largest piece of the only known meteorite from the planet Mercury has found its way to Yale, where it is now on display at the Peabody Museum of Natural History.

Known as NWA 7325, the fist-size, greenish space rock is a rarity among rarities:  there just aren’t many verified planetary meteorites. Scientists know of about 70 from Mars and, until now, none from any of the other planets in Earth’s solar system. There are about 180 known meteorites from the moon. NWA 7325 is the first believed to be from Mercury. (more…)

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Hungry Black Hole

Astronomers poised for galactic chow-down

The super-massive black hole at the center of the Milky Way Galaxy has a healthy appetite, frequently snacking on asteroids and comets. Now, a cloud of gas and dust called G2 is on a dangerous course to become its next meal.

Even though Sagittarius A* (pronounced “Sagittarius A-star”) hasn’t been easy to see through the cosmic dust, sitting 25,000 light years away at galaxy central, scientists know it is a black hole — and a hungry one at that. Its weight has been estimated to be more than that of 4 million suns. (more…)

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NASA Releases Images of Man-Made Crater on Comet

PASADENA, Calif. — NASA’s Stardust spacecraft returned new images of a comet showing a scar resulting from the 2005 Deep Impact mission. The images also showed the comet has a fragile and weak nucleus.

The spacecraft made its closest approach to comet Tempel 1 on Monday, Feb. 14, at 8:40 p.m. PST (11:40 p.m. EST) at a distance of approximately 178 kilometers (111 miles). Stardust took 72 high-resolution images of the comet. It also accumulated 468 kilobytes of data about the dust in its coma, the cloud that is a comet’s atmosphere. The craft is on its second mission of exploration called Stardust-NExT, having completed its prime mission collecting cometary particles and returning them to Earth in 2006. (more…)

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Primordial Dry Ice Fuels Comet Jets

*Initial science results on comet released from University of Maryland, much more to come UMD scientists say.* 

 

Jets Galore. This enhanced image, one of the closest taken of comet Hartley 2. Image credit: University of Maryland

COLLEGE PARK, Md. – One of the biggest comet findings coming out of the amazing images and data taken by the University of Maryland-ledEPOXI mission as it zipped past comet Hartley 2 last week is that dry ice is the ‘jet’ fuel for this comet and perhaps many others. 

Images from the flyby show spectacular jets of gas and particles bursting from many distinct spots on the surface of the comet. This is the first time images of a comet have been sharp enough to allow scientists to link jets of dust and gas with specific surface features. Analysis of the spectral signatures of the materials coming from the jets shows primarily CO2 gas (carbon dioxide) and particles of dust and ice. 

“Previously it was thought that water vapor from water ice was the propulsive force behind jets of material coming off of the body, or nucleus, of the comet,” said University of Maryland Astronomy Professor Jessica Sunshine, who is deputy principal investigator for the EPOXI mission. “We now have unambiguous evidence that solar heating of subsurface frozen carbon dioxide (dry ice), directly to a gas, a process known as sublimation, is powering the many jets of material coming from the comet. This is a finding that only could have been made by traveling to a comet, because ground based telescopes can’t detect CO2 and current space telescopes aren’t tuned to look for this gas,” Sunshine said.  (more…)

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UMD-Led Team Begins Imaging Comet Hartley 2 with Deep Impact Spacecraft

COLLEGE PARK, Md. — Some five years after its July 4th 2005 ‘comet shot’ was seen around the world, the Deep Impact spacecraft has begun regular imaging of a second comet target, Hartley 2. The spacecraft will continue imaging Hartley 2 during and after its closest approach on November 4, providing an extended look at the comet. However, there won’t be any fireworks this time as Deep Impact’s probe craft was destroyed in its deliberate 2005 collision with comet Tempel 1.

(more…)

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