New Hubble data from a unique star may lead to insights about some of the universe’s rarest and most massive and destructive stellar phenomena. Nicknamed “Nasty 1,” after the star’s catalogue name (NaSt1), a NASA press release calls it a “one-of-a-kind” star whose behavior has “never been seen before in our Milky Way Galaxy.”
Nasty 1 is a Wolf-Rayet star, a special class of stars that are, in a sense, all nasty. They’re the brightest, most massive stars scientists know of, at over 20 times the mass of the sun and with radiation propelling stellar winds at speeds of over ten million miles per hour. One reason astronomers find Wolf-Rayets so intriguing is that they challenge the conventional wisdom about how stars form. A prevailing theory about the birth of R136a1, a Wolf-Rayet and the most massive star known to humans, suggests that it formed not after the massive collapse of a cloud of gas and dust, but as the result of two monster stars spiraling towards each other and eventually colliding.
However, Hubble’s latest observation of “Nasty 1,” a Wolf-Rayet star in the constellation Aquila, has astronomers rethinking what they know about the lives and deaths of stars. According to NASA, where astronomers expected to see “twin lobes of gas flowing from opposite sides of the star,” Hubble’s images have revealed a flat disc of gas encircling the star (see below).
What could explain this heretofore unobserved behavior? According to the authors of a recent study on “Nasty 1,” the star is thought to have a companion star buried within its nebula. The more compact companion star could be gaining mass from the larger star through a process known as gravitational stripping: as the larger star sheds its outer layers, the ultra-hot, ultra-bright helium core is gradually exposed, making a Wolf-Rayet star. But if a significant amount of matter from the larger star simply spills out into space, it may form a nebula like the one surrounding Nasty 1.
Whatever the cause of the gas disk, scientists can be sure about one thing: Nasty 1 will not go quietly when its time comes.
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. Jon Mauerhan, LEAD STUDY AUTHOR