Comet Hartley

Comet Hartley 2’s Trail

New findings from NEOWISE, the asteroid and comet-hunting portion of NASA’s Wide-field Infrared Survey Explorer mission, show that comet Hartley 2 leaves a pebbly trail as it laps the sun, dotted with grains as big as golf balls.Previously, NASA’s EPOXI mission, which flew by the comet on Nov. 4, 2010, found golf ball to basketball-sized fluffy ice particles streaming off comet Hartley 2.NEOWISE data show that the golf ball-sized chunks survive  farther away from the comet than previously known, winding up in Hartley 2’s trail of debris. The NEOWISE team determined the size of these particles by looking at how far they deviated from the trail. l

The observations also show that the comet is still actively ejecting carbon dioxide gas at a distance  of  2.3  astronomica units from the sun, which is farther away from the sun than where EPOXI detected carbon dioxide jets streaming from the comet. An astronomical unit is the average distance between Earth and the sun.