Supernova alert! Astronomers just found a way to predict explosive star deaths
A team of astronomers has developed an early-warning system for supernovas, the dramatic explosions of massive stars.
Science & Tech
Wouldn't it be nice to know when a giant star is about to die in a cataclysmic supernova explosion? A team of astronomers has done just that. If you see a giant red star surrounded by a thick shroud of material, watch out — the star will likely explode within a few years.
When a massive star approaches the end of its life, it goes through several violent phases. Deep in the star's core, it shifts from fusing hydrogen to fusing heavier elements, starting with helium and moving up to carbon, oxygen, magnesium and silicon. At the end of the chain, the star eventually forms iron in its core. Because iron saps energy rather than releasing it, this spells the end for the star, and in less than a dozen minutes, it turns itself inside out in a fantastic explosion called a supernova.
But for all the commotion that goes on in the stars' hearts, from the outside, it's hard to tell exactly what's going on. Sure, near the end of their lives, these giant stars swell to extreme sizes. They also become intensely bright — up to tens of thousands of times brighter than the sun. But because the stars' surfaces are so distended, their outer temperatures actually drop, making them appear as red giants.
The most famous example of such a near-terminal star is Betelgeuse. If it were placed within our solar system, this star — which is only 11 times more massive than the sun — would stretch to the orbit of Jupiter. It will go supernova any day now, but "any day" for an astronomer could be a million years away. Even though we know that these kinds of stars will eventually detonate in a supernova, there's no way to get a more precise estimate than that. Or, at least, that used to be the case.
Ticking time bomb
Now, a team of astronomers has developed a way to spot supernovas that are likely to go off within a few years. They reported their results in a paper published to the preprint database arXiv and accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.
They specifically studied a few dozen of a unique type of supernova known as Type II-P supernovae. In contrast to other supernovas, these explosions remain bright long after the initial outburst.
In a few examples, astronomers have looked back at old catalogs and found images of the stars before they exploded, and they all seem to be red supergiants like Betelgeuse. That's a clear indication that those kinds of stars are supernova candidates, ready to go off at a moment's notice.
The stars that result in these kinds of supernovas are thought to have dense shrouds of material surrounding them before they explode. These shrouds are orders of magnitude denser than what's measured around Betelgeuse. It's the heating of that material from the initial shock wave that causes the brightness to linger; there's simply more stuff lying around to keep glowing well after the first sign of the explosion.