An exploding star that will be visible to the naked eye for the first time in 80 years is running late, with astronomers keenly looking out for the rare event.
The explosion T Corona Borealis, also known as T Cor Bor, is a phenomenon caused by two stars that orbit one another 3,000 light years away.
A tiny white dwarf star is orbiting a much bigger star and the smaller of the dyad is slowly sucking matter from its companion and accruing a thin hydrogen skin around its barren surface.
This flammable blanket of gas will ignite in a nuclear explosion when the layer is heavy enough that the pressure creates a temperature able to set the hydrogen alight.
The process of accretion and ignition usually takes around 80 years and last occurred in 1946. The resulting blast, or nova, will be visible with the naked eye in the constellation of Corona Borealis, also known as the Northern Crown, and will be roughly as bright as Polaris.
“The white dwarf star is gathering material from the surface of the red giant, and this material is swirling around the white dwarf before being pulled down to the surface,” Jessica Lee, Astronomer at Royal Observatory Greenwich, told The Telegraph.
“This creates a layer of material on the surface of the smaller star, and when the temperature and pressure have built up just right a runaway thermonuclear explosion, or nova, occurs.
“This nova clears away the surface material but doesn’t destroy the star, so the process starts again and re-occurs approximately every 80 years.”
Michael Woodman, 94, from Newport, was the first person in the UK to see the nova in the night sky the last time it happened was when the then-teenage amateur astronomer saw the bright star emerge.
He wrote to the then-astronomer royal about his sighting, which he said felt like hitting the jackpot and received a letter back confirming he was the first person to see the event.
‘Slightly overdue’
The current Astronomer Royal, Lord Martin Rees, the former president of the Royal Society and a fellow of Trinity College at Cambridge University, told The Telegraph that the process should be coming around once more, and is perhaps “slightly overdue”.
Astronomers earlier in 2024 noticed dips in activity in the binary system, which was heralded as a sign the explosion was imminent, with a timeline of before September expected.
But the blast has yet to occur, with astronomers now keeping a keen eye trained on the night sky.
“The amount of hydrogen is gradually accumulating on the surface of the white dwarf as it goes round and round the other star and when there is enough, there is an explosion,” Lord Rees said.
“But it’s not going to be all that spectacular. The star is normally about magnitude 10, which is too faint to be seen without a telescope. But when it’s flaring, it’s going to be second magnitude, so one of the hundreds or so bright stars in the sky, no more than that.
“It’s not going to be like a supernova or anything spectacular. One would expect this sort of thing, just on basic physical grounds to happen roughly with the same frequency all the time.
“If the gap between the second and third appearance is the same as between the first and second that we saw, then it is slightly overdue.
“But there’s no particular reason to expect this sort of event to be completely regular. People bet it will happen in the next year or two, and I doubt that we can be confident of any more precise forecast.”
‘10 known ones in our galaxy’
When it does happen, the flare from the explosion will be a once-in-a-lifetime event for astronomers, both professional and amateur.
“Nova are not rare. However recurrent Novae, ones that happen over and over again, are rare with only 10 known ones in our galaxy,” Dr Daniel Brown, associate professor in astronomy and science communication at Nottingham Trent University, told The Telegraph.
“It is even rarer to have one that is then visible to the naked eye and this one specifically will be very bright indeed, rivalling the brightest star in its constellation: Corona Borealis.
“It will remain visible to the naked eye for about 5 days only, even less if you live in light polluted areas, while it rapidly dims. Then it will only be observable with binoculars or telescopes.”
Astronomers are preparing already for the event, with equipment trained on the spot in the sky likely to light up because modern tools have never been able to study the event before.
“With more detailed observations including spectroscopy, X-ray and gamma-ray telescopes we will be able to understand more how such stars behave,” Dr Brown added.
“It is always a treat when something doesn’t happen as predicted. That’s always a sign that we are about to explore something new and expand our current understanding.”
