New pinwheel star system discovered

New York: Scientists have discovered a new, massive star system in the Milky Way galaxy that challenges existing theories of how large stars eventually die. "This system is likely the first of its kind ever discovered in our own galaxy," said Benjamin Pope, a NASA Sagan fellow at New York University in the US. The scientists detected a gamma-ray burst progenitor system -- a type of supernova that blasts out an extremely powerful and narrow jet of plasma and which is thought to occur only in distant galaxies. "It was not expected such a system would be found in our galaxy -- only in younger galaxies much further away," said Pope. "Given its brightness, it is surprising it was not discovered a lot sooner," Pope said. 

The system, described in the journal Nature Astronomy, and has been dubbed "Apep". An estimated 8,000 light years away Earth, the system is adorned with a dust "pinwheel" -- whose strangely slow motion suggests current theories on star deaths may be incomplete. When the most massive stars in our universe near the end of their lives, they produce fast winds -- typically moving at more than 1,000 kilometers per second -- that carry away large amounts of a star's mass. These fast winds should carry away the star's rotational energy and slow it down long before it dies.

"These massive stars are often found with a partner, in which the fast winds from the dying star can collide with its companion to produce a shock that emits at X-ray and radio frequencies and produces exotic dust patterns," said Joseph Callingham, a postdoctoral fellow at the Netherlands Institute for Radio Astronomy. "Apep's dust pinwheel moves much slower than the wind in the system," he said. "One way this can occur is if one of the massive stars is rotating so quickly that it is nearly tearing itself apart. "Such a rotation means that when it runs out of fuel and begins to explode as a supernova, it will collapse at the poles before the equator, producing a gamma-ray burst," Callingham said.