The Webb telescope has unlocked a mystery in an exotic star system located approximately 8,000 light-years from Earth. Using its mid-infrared observation capabilities, the space telescope captured the first image of four swirling spirals of dust encircling two aging stars locked together in an orbital dance.
NASA released the image on Wednesday, confirming the existence of the layered shells of dust surrounding two Wolf-Rayet stars in the Apep system. Previous observations had only detected one dust spiral, while Webb was not only able to see all four, but it also narrowed down how long the binary stars take to orbit one another.
“Looking at Webb’s new observations was like walking into a dark room and switching on the light—everything came into view,” Yinuo Han, a researcher at Caltech in Pasadena, California, and lead author of a new study published in the Astrophysical Journal, said in a statement. “There is dust everywhere in Webb’s image, and the telescope shows that most of it was cast off in repetitive, predictable structures.”
One of a kind
Wolf-Rayet stars are extremely rare, with only about a thousand of them believed to exist in the Milky Way galaxy. They are massive, bright stars in late stages of their stellar evolution. Stars that big don’t last very long; Wolf-Rayets burn through their fuel rather quickly, expelling their mass into space through high-pressure winds.
The pair of stars in Apep, named after the Egyptian god of chaos, have been shedding their outer layers over the past 700 years. The two Wolf-Rayet stars are gravitationally bound to one another, along with a third companion, a massive supergiant star that carves a hole into the clouds of dust from its wider orbit.
Most Wolf-Rayet stars orbit one another within two to 10 years, with the longest recorded orbital period being 30 years. The Apep stars, however, swing by one another every 190 years. The team of researchers behind the new study was able to figure out the orbits of the stars by combining measurements of the location of the rings from Webb’s image with the speed of the shells’ expansion from observations taken by the European Southern Observatory’s Very Large Telescope in Chile over a period of eight years.
With each long orbit, the two stars remain close for 25 years, forming the expanding dust shells. As the stars approach and pass one another, their stellar winds collide and mix, forming the spirals of dust for a period that lasts a quarter of a century. The dust of other star systems lasts for a few months at a time.
Although the Webb image may inspire tranquility, there is nothing chill about the Apep stars. The two stars are emitting dust at 1,200 to 2,000 miles per second (2,000 to 3,000 kilometers per second) while speeding through the cosmos.
The Wolf-Rayet stars were initially more massive than their third companion but have shed most of their mass over the years. Scientists estimate that the two stars are between 10 and 20 times the mass of the Sun, while the supergiant is 40 or 50 times as massive as our host star.
Although scientists have known about the third star in the Apep system, Webb’s observations confirmed that it is gravitationally bound to the system by revealing it slicing through the dust shells. “Webb gave us the ‘smoking gun’ to prove the third star is gravitationally bound to this system,” Ryan White, a PhD student at Macquarie University in Sydney, Australia, and author of another paper published in the Astrophysical Journal, said in a statement.
The two massive stars are on a path to destruction and will eventually explode as supernovas. It’s possible that either of the stars may emit a gamma ray burst before becoming a black hole.
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