Friday, August 28, 2015

The Comet is Still There, Waiting for the Perihelion Time Update

This morning we should get better information about the orbit of the incoming comet. The orbit from last night is shown at left (times are in UTC). The plus signs are spaced 5 minutes apart. They get a little farther apart as the comet moves from lower right to the upper left. This means the comet is speeding up. At perihelion (the closest it gets to the Sun) the comet will be moving at about 600 km/s (1.3 million mph).

We see comets because they evaporate ices and other compounds from their surface. This cools the comet, but makes it disappear. The water ice that comes off the comet quickly turns into Hydrogen and Oxygen atoms. SDO sees comet tails when the oxygen atoms hit the electrons in the corona. We can use the tails to explore the Sun's magnetic field and corona.

Most Kruetz sungrazing comets are too small to make it to perihelion (Comet Lovejoy in December 2012 was the only exception). We can only watch as this comet goes behind the LASCO occulter disks and hope it continues to evaporate and be seen in SDO/AIA images.