Chandra Release - April 18, 2016

Visual Description: Comets ISON & PanSTARRS

The two-panel image features Comet ISON (left) and Comet PanSTARRS (right). Both of these comets are shown in both X-ray pull outs from full-field optical images.  The X-ray images of the two comets display a rich purple hue, while the optical image shows it as a bright greenish-white object for ISON and yellow-white for PanSTARRS.  In the X-ray images, Comet ISON appears to have an irregular shape like a 3 leaf clover, while PanSTARRS shows a slight anvil shape.  The dramatic optical images highlight the comets' brightness and tails. NASA's Chandra X-ray Observatory observed these two comets in 2013 when both were relatively close to Earth, about 90 million and 130 million miles for Comets ISON and PanSTARRS respectively. These comets arrived in the inner Solar System after a long journey from the Oort cloud, an enormous cloud of icy bodies that extends far beyond Pluto's orbit. The optical images were taken by an astrophotographer, Damian Peach, from the ground during the comets' close approach to the sun that have been combined with data from the Digitized Sky Survey to give a larger field of view. (The greenish hue of Comet ISON is attributed to particular gases such as cyanogen, a gas containing carbon and nitrogen, escaping from the comet's nucleus.) The different shapes of the X-ray emission from the two comets indicate differences in the solar wind at the times of observation and the atmospheres of each comet. Comet ISON, on one hand, shows a well-developed, parabolic shape, which indicates that the comet had a dense gaseous atmosphere. On the other hand, Comet PanSTARRS has a more diffuse X-ray haze, revealing an atmosphere with less gas and more dust.