Observations by NASA’s Hubble Space Telescope have revealed a disk of gas nearly 3 trillion miles (4.8 trillion kilometers) wide surrounding Nasty 1, which is a massive, rapidly aging object known as a Wolf-Rayet star.
Wolf-Rayet stars start out big, initially containing at least 20 times more mass than the sun. But their hydrogen-dominated outer layers soon puff up and are lost, exposing the objects’ helium-burning cores to space. Astronomers aren’t exactly sure how this process unfolds, but they have a few ideas.
For example, some scientists think these massive stars’ powerful stellar winds blow away their own hydrogen envelopes. Another idea holds that the outer layers are siphoned off by a cannibalistic companion star.
“That’s what we think is happening in Nasty 1,” study lead author Jon Mauerhan, of the University of California, Berkeley, said in a statement, referring to the second hypothesis. “We think there is a Wolf-Rayet star buried inside the nebula, and we think the nebula is being created by this mass-transfer process. So this type of sloppy stellar cannibalism actually makes Nasty 1 a rather fitting nickname.”
Such a disc had never before been seen surrounding a Wolf-Rayet star, researchers said. The nebula is likely only a few thousand years old and lies about 3,000 light-years from Earth, they added.
Several other factors further bolster the cannibalism idea over the stellar-wind hypothesis, study team members said. For one thing, at least 70 percent of all massive stars belong to binary systems. And modeling work suggests that such a star’s own winds may not be strong enough to push it to Wolf-Rayet status.
“We’re finding that it is hard to form all the Wolf-Rayet stars we observe by the traditional wind mechanism, because mass loss isn’t as strong as we used to think,” co-author Nathan Smith, of the University of Arizona, said in the same statement.
“Mass exchange in binary systems seems to be vital to account for Wolf-Rayet stars and the supernovae they make, and catching binary stars in this short-lived phase will help us understand this process,” Smith added.
It’s tough to get a precise bead on Nasty 1, whose nickname is a play off its formal catalog name NaSt1 (the star was discovered in 1963 by Jason Nassau and Charles Stephenson). The star is obscured by a great deal of gas and dust, so Mauerhan and his team were not able to determine the mass of Nasty 1 or its companion, the distance between them or the amount of material the companion is ingesting, researchers said.
It’s also unclear exactly what will happen to Nasty 1 down the road, but the star’s evolutionary path “will definitely not be boring,” Mauerhan said.
Read more at Discovery News
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