Could WR 104 Threaten Earth?

By Greg Bryant

January 7, 2008 : The binary system known as WR 104, which consists of a Wolf-Rayet star and an OB companion, is well known for its spectacular dusty “pinwheel” nebula, which was revealed in spectacular detail by a team of astronomers lead by Peter Tuthill (now at Sydney University) in 1999. The nebula is formed by material contained within a wind that is driven away from the binary stars. As the material moves away from the stars, it curves as it rotates around the system.

That same team, expanded to include others from Australia and the United States, has now compiled observations (taken with the 10 metre Keck Telescope in Hawaii) of WR 104 spanning six years (their study is to be published in the Astrophysical Journal). Wolf-Rayet stars are candidates for turning into supernovae, and so their mass-loss history is of considerable interest.

Recent studies of supernovae have explored whether there is a link between these exploding stars and gamma-ray bursts (the most energetic events known in the Universe). In the case of WR 104, it is possible that when the Wolf-Rayet star explodes, much of the energy and matter will be ejected at the polar ends – and Earth is virtually pole-on to the system.

Our understanding of the connection between supernovae and gamma-ray bursts is still in its infancy, but Tuthill and his colleagues suggest that there is a possibility that WR 104 might produce a gamma-ray burst – one that would be only 7,000 light-years from us (as good as on our doorstep).

The good news is that we probably have several hundred thousand years before the Wolf-Rayet star in question does explode.