These two newly discovered stars locked in a death spiral are a throwback to something not seen since the early universe. A new of the spectacular find, via researchers at the Netherlands Institute for Radio Astronomy, appears today in Nature Astronomy.
The stars, located about 7,800 light years away, are in what's called a stage. That's when massive stars begin to shed their hydrogen, burning certain elements in their atmosphere like carbon and nitrogen. A sort of nebula that forms around the stars makes them easy to spot.
But something peculiar is happening here: These two Wolf-Rayet stars are causing the nebula to move a bit like a pinwheel in interactions that are also producing gamma ray bursts—high energy events usually generated by massive objects like black holes. By finding a source of the particular kinds of gamma ray bursts produced in these stars, astronomers have a laboratory right in our backyard to test long duration gamma ray bursts.
This is important because most examples are so old and far away that they're not an easy study. We don't know for sure if, perhaps, this rotating behavior is more common than we expect or a normal step in every Wolf-Rayet's behavior or if these are truly acting out some ancient behaviors for some bizarre reason. It also means that we can understand the origin of some of the most energetic events in the universe.
What's strange is that this kind of Wolf-Rayet behavior is typically seen in some of the first generations of stars, ones considered "metal poor" because they're low in atoms of heavier elements.
"All the massive stars in our galaxy are materials from stars that have come and gone," says Joseph Callingham, a Netherlands Institute for Radio Astronomy researcher. This means that the stars we see today, for the most part, are metal-rich and shouldn't be exhibiting such behavior—especially because O-type stars (which these Wolf-Rayets both are) have a lifespan of a few million years before they explode into a supernova.
These stars are, "As big as you get … the big boys on the block," Callingham says. "They don’t get much bigger than this." The stars are powerful enough to emit in X-ray, infrared, and visible spectra, marking a particularly energetic star. But ... they'd somehow gone virtually undiscovered until now. "This object should have been discovered in the 1980s, it’s so bright," Callingham says.
Given how bright they'll burn, these stars (given the easy-to-remember name 2XMM J160050.7–514245) will prove a perfect case study in the sort of pinwheel death spiral usually seen billions—not millions—of light years away, and should provide insight into why these relatively young stars are acting like ones much, much older.
"It’s kind of throwing a lot of odd balls of us," Callingham says before comparing it to Eta Carinae, another binary of giant stars whose behavior is so bizarre that it keeps scientists constantly on their toes. "We’re thinking that it’s an like object in that it’s throwing everything you know in your face."