A one-of-a-kind star spotted by the Hubble Space Telescope has been nicknamed Nasty 1 by astronomers.
The star is located around 3,000 light-years from Earth, and astronomers believe that it is a Wolf-Rayet star. However this particular star is unique because it is surrounded by a huge flat gas disk which is around 2 trillion miles wide. Although Wolf-Rayet stars usually have twin polar lobes of burning gas, astronomers think that this particular star may be in a transition phase that has never been observed before.
Wolf-Rayet star: Hydrogen depletion caused by stellar cannibalism
The nickname, Nasty 1, was inspired by the star’s catalog name, NaSt1. However its unique appearance and the reasons for its strange nature make the nickname very fitting. Wolf-Rayet stars are large and their cores are exposed as their hydrogen-filled outer layers are stripped away, making them grow even bigger and revealing their helium-burning cores.
Astronomers previously thought that the hydrogen depletion was caused by erosion due to strong stellar winds. Nasty 1 has made scientists come up with a new theory involving hydrogen theft by companion stars, a process that they have call “mass-exchange.”
“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 study co-author Nathan Smith, an astronomer at the University of Arizona in Tucson.
Gas disk result of gravitational tug-of-war
This hydrogen theft is not always a clean process, and some of the gas is lost in the space between the two companion stars. This may provide an explanation for the existence of the huge gas disk that can be observed around Nasty 1.
“That’s what we think is happening in Nasty 1,” said study leader Jon Mauerhan, a researcher at the University of California, Berkeley. “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.”
The paper is published in the Monthly Notices of the Royal Astronomical Society.