Astronomers are studying "Nasty 1" — a unique star with bizarre properties befitting its "bad boy" moniker. The nickname is nevertheless a clear play on the Wolf-Rayet star's official name, NaSt1.
Wolf-Rayet stars are the dying bodies of massive stars in their last burst of glory, which are roughly 20 times the size of our own sun. They experiece a sudden surge of energy just before they collapse, eventually exploding into supernova.
Wolf-Rayet stars usually exhibit twin lobes of gas that extend from opposite ends of the star. However, Nasty 1 is different — instead of poles of gaseous material, this star is surrounded by a disk of gas, which extends 1,000 times wider than our own solar system.
Normally, the gas spreading out from Wolf-Rayet stars is captured by other nearby stars, which strip hydrogen from the dying stellar body. This leaves behind a core consisting mostly of helium — like a Tootsie Roll core of a licked lollipop.
The Hubble Space Telescope (HST) recorded images of the unusual disk surrounding NaSt1. Astronomers believe this unique feature was formed through the gravitational interactions between Nasty and a neighboring star.
"We were excited to see this disk-like structure because it may be evidence for a Wolf-Rayet star forming from a binary interaction," said Jon Mauerhan of the University of California, Berkeley. "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."
Astronomers Jason Nassau and Charles Stephenson discovered NaSt1 back in 1963, providing the first two letters of their last names for the star's catalog name. NaSt1 burns roughly 3,000 light years from Earth, and astronomers believe the disk surrounding the body first began to form around a few thousand years ago.
As stars begin to die, they shed off hydrogen gas in a shell surrounding the body. Roughly 70 percent of Wolf-Rayet stars are members of binary star systems, which supports the theory that these bodies are formed by the process of one star stripping another of this hydrogen shell. Astronomers however believe some massive stars may also drive this shell away from their cores through stellar wind, similar to the solar wind seen in our solar system.
In massive binary systems, the process can be inefficient — "leaking" material outward from the system. This process could could account for the presence of this massive disk.
"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.
This study of NaSt1 was published in the Monthly Notices of the Royal Astronomical Society.
