* Astronomy

NASA's Swift Monitors Departing Comet Garradd

An outbound comet that provided a nice show for skywatchers late last year is the target of an ongoing investigation by NASA's Swift satellite. Formally designated C/2009 P1 (Garradd), the unusually dust-rich comet provides a novel opportunity to characterise how cometary activity changes at ever greater distance from the sun.
A comet is a clump of frozen gases mixed with dust. These "dirty snowballs" cast off gas and dust whenever they venture near the sun. What powers this activity is frozen water transforming from solid ice to gas, a process called sublimation. Jets powered by ice sublimation release dust, which reflects sunlight and brightens the comet. Typically, a comet's water content remains frozen until it comes within about three times Earth's distance to the sun, or 3 astronomical units (AU), so astronomers regard this as the solar system's "snow line."
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The magnitude 6.9 comet C/2009 P1 (Garradd) will pass 2.38° from the magnitude 10.6 galaxy IC 2574, in the constellation Ursa Major, at 11:00 UT, 21st March, 2012.

The magnitude 6.7 comet C/2009 P1 (Garradd) will pass 0.44° from the magnitude 12.8 galaxy NGC 4250, in the constellation Draco, at 01:00 UT, 14th March, 2012.

The magnitude 6.4 comet C/2009 P1 (Garradd) will pass 0.12° from the magnitude 12.8 Dwarf Spheroidal Galaxy UGC 9749, in the constellation Ursa Minor, at 11:00 UT, 2nd March, 2012.

Position (J2000): R.A. 15 09 08.5 |  Dec. +67° 13' 21''