Sometime in the coming months, a spectacle could light up the northern skies.
There, in the constellation Corona Borealis, more than 2,500 light-years away, lurks a star called T Coronae Borealis that is about to explode, temporarily making the star one of the brightest objects in the night. sky.
Astronomers are on tenterhooks waiting for this thing to explode, not just because it’s going to be amazing, but because of the amount of data we’ll be able to gather about a type of stellar explosion called a classical nova.
The reason we know T Coronae Borealis (abbreviated T CrB) explodes is because it happens once every 80 years, for at least eight centuries.
This means that it is very close to a once-in-a-lifetime event – ​​and that the technology we have to observe it now far exceeds what we had during the last excursion, in February 1946.
“There are a few recurring novae with very short cycles, but typically in a human lifetime we don’t often see repeated flares, and rarely ones that are so relatively close to our own system,” says astronomer Rebekah Hounsell of NASA’s Goddard Space Flight. Center.
“It’s incredibly exciting to have this front row seat.”
Classical novae are smaller explosions that leave the star more or less intact, not to be confused with the near-annihilation of stars in cataclysmic explosions known as supernovae. In fact, this is far from the first time this particular space object has gone through this experience.
The reason T CrB explodes repeatedly and on schedule is because of the strangeness of the type of star it is. It is a binary star system that contains the remnants of the collapsed core of a Sun-like star called a white dwarf and a bloated red giant.
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White dwarfs are very small and very dense, between the size of the Earth and the Moon, packing as much mass as 1.4 Suns into this size. This means that they are quite gravitationally intense; and if they have a binary companion in a close enough orbit, they tend to suck up material, mostly hydrogen.
Over time, this hydrogen accumulates on the surface of the white dwarf, compressed downward by gravity. Eventually, the pressure and heat on the bottom layer of hydrogen build up enough that the whole thing ignites in an uncontrolled thermonuclear explosion, violently ejecting the excess hydrogen into space in spectacular style.
This is new; and for T CrB the time this process takes is approximately 80 years.
Over the past decade, astronomers have observed the binary system behaving much like it did before the 1946 explosion; specifically, a decrease in brightness that heralds the close approach of an eruption. Their analysis suggests that this could happen very soon – as early as September 2024.
This means that astronomers are watching very closely a small patch of sky grouped by the constellations – Lyra, Hercules, Boötes – and a small arc of stars sandwiched between them. That’s the Corona Borealis.
We expect to hear about the new pretty much as soon as it happens. It blooms in the sky to become visible to the naked eye, then gradually fades from view over the course of a week. So you should have time to get there and check it out if you can think of it.
In fact, if you can, that would be awesome. Citizen scientists are also encouraged to collect data. The more eyes on T CrB, the better we will understand his spectacular outbursts.
And, of course, as many telescopes as possible will be tuned, from the longest radio wavelengths to the strongest X- and gamma-rays.
“Recurring novae are unpredictable and contradictory,” says NASA Goddard astrophysicist Koji Mukai. “Just when you think there can be no reason why they follow a certain set pattern, they do – and once you start relying on them repeating the same pattern, they completely deviate from it. We’ll see how T CrB behaves.”