New findings are in from NEOWISE, the Near Earth Object (NEO, typically a comet or asteroid) observing component of NASA’s Wide-field Infrared Survey Explorer (WISE) telescope. WISE is/was an infrared surveyor satellite set into polar orbit in 2010. The spacecraft was designed with a limited life span of approximately ten months: one month for testing and checkout, six months for a whole-sky survey, and three months for a second survey meant to identify any changes that had taken place in the sky since the first survey.
April 14, 2011 marked the date of the preliminary release of WISE data. The final release won’t happen for another ten months or so, but we already have some interesting results from released data. Today it was announced that Comet Hartley 2 is leaving a bumpy, pebbly trail behind it with grains as large as golf balls. The last time the comet was surveyed (November 2010, as part of NASA’s EPOXI mission), data showed that the comet was streaming golf ball- to basketball-sized fluffy ice particles. The NEOWISE results indicate that the smaller, golf ball-sized pieces survive farther away from the comet than scientists previously thought, comprising at least part of the comet’s debris trail. According to the NEOWISE team, larger chunks are less likely to be pushed away from the comet’s trail by radiation pressure of the sun. Since these observed particles are in the trail, they must be (relatively) small.
The team was also surprised to note that Hartley 2 is ejecting carbon dioxide gas at a distance of 2.3 AUs from the Sun. Although EPOXI had detected carbon dioxide streaming from comet, it was at a distance considerably closer to the Sun. So, that’s two new things we know about comet behavior today that we didn’t know yesterday. Money well spent.
An abstract of the paper, “WISE/NEOWISE observations of comet 103P/Hartley 2,” which has been accepted by the Astrophysical Journal, can be read online. If you have access, you download a .pdf of the entire paper.
