Astronomers using the Hubble Space Telescope recently got a good look at the Wolf-Raynet star Nasty-1. The star was first observed decades ago, but the Hubble allowed a better view of what was going on and the observations have expanded scientist’s understanding of this particular kind of star.

Wolf-Raynet stars are in their final active stage before becoming a supernova. They are about 25 times the size of our Sun and much hotter and brighter. Despite this they are also shedding their hydrogen-filled outer layers.

When researchers looked at the star Nasty-1, a derivation of its catalog name NaSt1, they expected to see twin jets of gas flowing from opposite sides of the star similar to what has been observed from the star Eta Carinae. Instead they found a pancake-shaped disk of gas nearly 2 trillion miles wide. That disk appears to be just a few thousand years old and 3,000 light years from Earth.

The researchers think that this could indicate an unseen companion star that stole mass from Nasty-1 as it was shedding its outer layers.

“We were excited to see this disk-like structure because it may be evidence for a Wolf-Rayet star forming from a binary interaction. There are very few examples in the galaxy of this process in action because this phase is short-lived, perhaps lasting only a hundred thousand years, while the timescale over which a resulting disk is visible could be only ten thousand years or less,” said study leader Jon Mauerhan of the University of California, Berkeley in a statement.

If the researchers are correct, it means that as a massive star begins to run out of hydrogen, it swells and a nearby companion star begins to cannibalize the loosely bound gas. As the companion star gains mas, the bright helium core of the Wolf-Raynet star is exposed.

This hypothesis is gaining traction because, researchers have observed, at least 70 percent of massive stars are in double-star systems.

“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,” said Nathan Smith of the University of Arizona in Tucson, who is a co-author on the new NaSt1 paper.

During this process however, researchers expect that some of the stripped matter would spill out of of the gravitational tug of war which would account for the pancake disk.

“That’s what we think is happening in Nasty 1. 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,” said Mauerhan.

Eventually, Nasty-1 will run out of material, the gas will dissipate and astronomers will have a clear view of the binary system.

“What evolutionary path the star will take is uncertain, but it will definitely not be boring. Nasty 1 could evolve into another Eta Carinae-type system. To make that transformation, the mass-gaining companion star could experience a giant eruption because of some instability related to the acquiring of matter from the newly formed Wolf-Rayet. Or, the Wolf-Rayet could explode as a supernova. A stellar merger is another potential outcome, depending on the orbital evolution of the system. The future could be full of all kinds of exotic possibilities depending on whether it blows up or how long the mass transfer occurs, and how long it lives after the mass transfer ceases,” said Mauerhan.

The researcher appears in the Monthly Notices of the Royal Astronomical Society.