Hubble Sees a Neutron Star Alone in Space

This is the first direct look, in visible light, at a lone neutronstar, as seen by NASA/ESA Hubble Space Telescope. The Hubble results show thestar is very hot (1.2 million degrees Fahrenheit or about 670 thousand degrees Celsius at the surface), and can be no larger than 16.8 miles (28 kilometers) across. These resultsprove that the object must be a neutron star, because no other knowntype of object can be this hot, small, and dim (below 25th magnitude).

The first clue that there was a neutron star at this location came in1992, when the ROSAT (the Roentgen Satellite) found a bright X-ray source without any optical counterpart in optical sky surveys. Hubble's Wide Field Planetary Camera 2 was used in October 1996 to undertake asensitive search for the optical object, and found a stellar pinpointof light within only 2 arc seconds (1/900th the diameter of the Moon) ofthe X-ray position. Astronomers haven't directly measured the neutronstar's distance, but fortunately the neutron star lies in front of amolecular cloud known to be about 400 light-years away in the southernconstellation Corona Australis.