Science

Supernova Alert! Astronomers have just found a way to predict the explosive death of stars

Wouldn’t it be nice to know when a giant star is about to die in a cataclysmic supernova explosion? A group of astronomers did just that. If you see a giant red star surrounded by a thick layer of matter, be careful – the star is likely to explode in a few years.

As a massive star nears the end of its life, it goes through several turbulent phases. Deep in the core of a star, it goes from fusing hydrogen to fusing heavy elements, starting with helium and moving on to carbon, oxygen, magnesium, and silicon. At the end of the chain, the star eventually forms iron at its core. Since iron drains energy rather than releasing it, it means the end of the star, and in less than a dozen minutes it turns inside out in a fantastic explosion called a supernova.

But with all the turmoil going on in the hearts of the stars, it’s hard to tell exactly what’s going on from the outside. Of course, towards the end of their lives, these giant stars grow to extreme sizes. They also become very bright – tens of thousands of times brighter than the Sun. But because the surfaces of stars are so stretched out, their outer temperature actually drops, making them look like red giants.

On the subject: The James Webb Space Telescope unexpectedly discovered a supernova

The most famous example of such a close to the final star is Betelgeuse. If it were placed in our solar system, this star, which is only 11 times more massive than the Sun, would stretch out to the orbit of Jupiter. It will go supernova any day now, but for an astronomer, “any day” could be a million years from now. Even though we know that such stars will eventually go supernova, there is no way to get a better estimate than this. Or at least it used to be.

time bomb

Now a team of astronomers has developed a way to detect supernovae that are likely to explode within a few years. They reported their findings in a paper published in the arXiv preprint database and accepted for publication in Monthly Notices of the Royal Astronomical Society.

They specifically studied several dozen supernovae of a unique type, known as Type II-P supernovae. Unlike other supernovae, these explosions remain bright long after the initial outburst.

In several examples, astronomers have gone through old catalogs and found images of stars before they exploded, all of which appear to be red supergiants like Betelgeuse. This is a clear sign that such stars are supernova candidates, ready to explode at any moment.

It is believed that the stars that lead to this kind of supernovae are surrounded by a dense veil of material before the explosion. These shrouds are several orders of magnitude denser than those around Betelgeuse. It is the heating of this material from the initial shock wave that causes the brightness to persist; there are simply more things around that will glow well after the first signs of an explosion.

This dense cover also causes this type of supernova to become visible faster than its more exposed cousins. When the explosion initially occurs, the shock wave hits the material around the star, causing the shock wave to lose steam as it travels. While a supernova initially has enough energy to emit high-energy radiation such as x-rays and gamma rays, once the shock wave and surrounding material mix, the emitted radiation is in optical wavelengths.

So it seems that these thick sheets of material around stars are also a sign that a supernova is about to explode.

super cocoons

But how long does it take to form this shroud of material? The researchers studied two models. In one model, a star was blown from its surface by a high-speed wind that slowly separated parts of it and spread them around, forming a shroud over decades. In the second model, the star experienced a massive pre-supernova explosion that sent gas weighing up to one-tenth the mass of the Sun into orbit in less than a year.

The researchers then simulated how all this material would affect our images of the star. In any case, once a star has built its veil, it will be heavily obscured so that our current imaging technologies can detect it.

Since we have direct images of some pre-supernovae taken less than 10 years before they exploded, astronomers have concluded that the model of slow and steady processes does not work. Otherwise, the star would be dimmed.

All of this means that once a supergiant star builds a thick veil of material around itself, it is likely to go supernova within a few years. So if you happen to travel through space and encounter this exact scenario, consider yourself warned.

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