Scientists have discovered a real-life “death star” close to the Earth. The mysterious object is the remains of another sun that has collapsed into a ball just 10 kilometers or so wide.
The strange body, which is estimated to lie between 250 and 1,000 light-years away, is called a neutron star. Unusually for such an object, it has no companion star and shows no tattered remains of a supernova explosion. Neither does it emit any radio pulses.
It is only the eighth such known “isolated neutron star” and was observed using Nasa’s Swift X-ray satellite in the constellation of Ursa Minor, the Little Bear.
Its discoverers, from universities at Pennsylvania and Montreal, have named it Calvera after the villain in The Magnificent Seven. That is because they dubbed the previous seven with the title of the hit movie.
Despite its isolation, astronomers believe Calvera is the remains of a star that existed within our galaxy before exploding as a supernova. They say that to reach its current position, it must have wandered out of the Milky Ways disk of stars. Now they want to find out why.
Robert Rutledge of McGill University in Montreal, Quebec, first called attention to the object. He compared a catalogue of 18,000 X-ray sources from the German-American ROSAT satellite, which operated from 1990 to 1999, with catalogues of objects that appear in visible light, infrared light, and radio waves.
Rutledge realized that the ROSAT source – known as 1RXS J141256.0+792204 – did not appear to have a counterpart at any other wavelength. His team aimed the Swift satellite, plus other telescopes, at the mysterious source and confirmed that it was not associated with any other object.
The team believe that, although the star appears to have travelled across a large part of the sky, it is still close to its original birthplace. This means that it must be relatively close to Earth – indeed it could be the closest neutron star known.
Rutledge adds: “Either Calvera is an unusual example of a known type of neutron star, or it is some new type of neutron star, the first of its kind.” Last year, astronomers announced the discovery of a neutron star ringing like a bell.
The closest known supernova of recent times blew itself to bits in a satellite galaxy of our own Milky Way.
Picture: Casey Reed/Penn State University.