'Once-in-a-lifetime event': What is the rare nova explosion and how can I see it?

Stargazers across the globe may get the chance to see a "once-in-a-lifetime" cosmic event this summer when an exploding star system could light up the night sky.

A nova explosion of the binary star system T Corona Borealis (T CrB) is predicted to take place any time from until September and will be so bright will be visible from Earth with the naked eye.

This is an extremely rare event: the T Coronae Borealis nova was last seen from Earth in 1946.

What exactly is a nova explosion, and when and where will we be able to spot it?

What's going to cause the nova explosion?

Within the Northern Crown constellation is a star system called T Coronae Borealis, also known as the "Blaze Star".

It is 3,000 light years away from Earth, and is made up of two types of star. One, a white dwarf, is an earth-sized dead star, and the other is an ancient red giant.

The gravitational pull of the white dwarf gradually strips away hydrogen from the red giant.

Eventually, this build up of gas triggers a huge thermonuclear explosion, known as a nova explosion.

Is it a supernova?

This is a different event to a supernova, which involves a final explosion of a dying star.

In a nova event such as this, the star stays intact. The cycle of explosions, which send the buildup of material hurtling off into space, can carry on for hundreds of thousands of years.

Why is it so rare?

T Coronae Borealis' nova explosions are on a shorter cycle than average. It is uncommon to see a repeated outburst within our lifetime, especially one so close to our solar system, NASA said.

The first recorded sighting of the explosion was from Germany in 1217. The T Coronae Borealis nova was last seen from Earth in 1946.

“It’s a once-in-a-lifetime event that will create a lot of new astronomers out there, giving young people a cosmic event they can observe for themselves," said Dr. Rebekah Hounsell, a NASA assistant research scientist.

"It's incredibly exciting to have this front row seat," Dr Hounsell said.

When can it be seen?

Researchers say the star's behaviour over the past decade mirrors the lead-up to the 1946 nova explosion.

If the pattern continues, it is likely we will see the blast by September 2024 - but we don't know exactly when.

When it does happen, it will only be visible for a week.

What should we look out for?

T Coronae Borealis is found in the Northern Crown, a horseshoe-shaped curve of stars west of the Hercules constellation.

Stargazers should look between Arcturus and Vega, the two brightest stars in the Northern Hemisphere.

Dr Elizabeth Hays, chief of the Astroparticle Physics Laboratory at NASA Goddard, said those from across the world will be monitoring the star's behaviour.

She said: “Citizen scientists and space enthusiasts are always looking for those strong, bright signals that identify nova events and other phenomena.

“Using social media and email, they’ll send out instant alerts, and the flag goes up. We’re counting on that global community interaction again with T Coronae Borealis."

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