This is the first direct look, in visible light, at a lone
neutron star, as seen by NASA's Hubble Space Telescope. The
Hubble results show the star is very hot (1.2 million degrees
Fahrenheit at the surface), and can be no larger than 16.8 miles
(28 kilometers) across. These results prove that the object must
be a neutron star, because no other known type 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 in 1992,
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 a sensitive search for the optical object, and
found a stellar pinpoint of light within only 2 arc seconds
(1/900th the diameter of the Moon) of the X-ray position.
Astronomers haven't directly measured the neutron star's
distance, but fortunately the neutron star lies in front of a
molecular cloud known to be about 400 l