Tags: Star.
RX J0720.4-3125 is a neutron star in the constellation Canis Major. It was discovered in 1997 in the ROSAT All-sky survey. Measurement of its parallax leads to an estimate of around 360 parsecs (1174 light-years) for its distance from Earth. It is a member of the Magnificent Seven a group of neutron stars that are relatively near to our Solar System. RX J0720.4-3125 has a radius of around 5 km. Its spectrum and temperature appear to be mysteriously changing over several years.