Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
February 27, 1996
X-ray Moon and X-ray Star
Credit: ROSAT, MPE, NASA
Explanation: An X-ray star winks out behind the Moon in these before and after views of a lunar occultation of the galactic X-ray source designated GX5-1. The false color images were made using data from the ROSAT orbiting observatory and show high energy X-rays in yellow (mostly from GX5-1), and lower energy X-rays in red (the Moon reflecting X-rays from the Sun). GX5-1 is a binary system consisting of a neutron star and a companion star in mutual orbit about the system's center of mass. The gas in the companion star's outer envelope falls toward the neutron star and accumulates in a disk around it. This disk material swirls deeper in to the neutron star's gravitational well, and is finally dumped onto its surface - in the process creating tremendous temperatures and generating the high energy X-rays.
Authors & editors:
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEA at NASA/ GSFC