Astronomers at NASA have used the Hubble Space Telescope to capture a very rare event: A star, dubbed ‘Nasty 1,’ cannibalizing another star nearby, and producing a giant, pancake-shaped gas disk in the process.
The cannibal star, discovered several decades ago, was called
“Nasty 1,” not only because its catalogue name of NaSt1, but also
because of its weird behavior.
It was described as a Wolf-Rayet star, a massive rapidly evolving
star that quickly sheds its hydrogen-filled outer layers, which
leads to an explosion of its super-hot and extremely bright
helium-burning core.
However, Nasty 1 turned out to be nothing like the
well-researched Wolf-Rayet candidate, Eta Carinae, which has twin
lobes of gas flowing from opposite sides.
The NaSt1 star surprised the astronomers using NASA’s Hubble
Space Telescope by having a vast pancake-shaped gas disk of gas,
nearly 2 trillion miles wide, encircling it.
The scientists said that the disk may have formed from an unseen
companion star that snacked on the outer envelope of 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,” study
leader Jon Mauerhan, of the University of California, was cited
as saying by NASA’s website.
The nebula around Nasty 1 and its companion, located some 3,000
light-years from Earth, is believed to be just a few thousand
years old.
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“We were excited to see this disk-like structure because it
may be evidence for a Wolf-Rayet star forming from a binary
interaction,” Mauerhan said.
Observing Nasty 1 one has been a tough task even with the
capabilities provided by the Hubble Telescope.
The team is still unable to establish the mass of the stars and
the distance between them as their system is heavily cloaked by
gas and dust.
However, the effort was worth it as “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,” Mauerhan said.
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The disk around Nasty 1 will dissipate due to the Wolf-Rayet
star, eventually running out of material.
“What evolutionary path the star will take is uncertain, but
it will definitely not be boring,” Mauerhan said. “Nasty 1
could evolve into another Eta Carinae-type system.”
He added: “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.”
Mauerhan also pointed to a stellar merger as another potential
outcome, “depending on the orbital evolution of the system.”
He said: “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.”