Massive star explosion soon visible in the night sky

By September, the massive explosion of a star 3,000 light-years from Earth will be visible in the night sky.

Astronomers are in a frenzy: by September, the massive explosion of a star will be visible in the night sky, 3,000 light-years from Earth, providing an opportunity to study this rare cosmic phenomenon.B

This will be at least the third time mankind has witnessed the phenomenon known as nova, first discovered by Irish astronomer John Birmingham in 1866, then reappearing in 1946.

The event occurs in a binary star system, “T Coronae Borealis”, belonging to the constellation of the Boreal Crown, usually too faint to be visible to the naked eye.

But every 80 years or so, the exchange between these two stars, a pair bound in a deadly embrace, triggers a nuclear explosion that revives the luminosity.

The light from the explosion crosses the cosmos, giving the impression, for a few days, that a new star – as bright as the North Star, according to NASA – has just appeared in our night sky.

A beautiful sight

Sumner Starrfield, an astronomer at Arizona State University, told AFP that he was very excited to see the show. The scientist has been working on the “T Coronae Borealis” phenomenon since the 1960s.

These days, he’s rushing to complete a scientific paper predicting what astronomers might discover by observing the nova, expected in the next five months. “It could happen today… but I hope it doesn’t!” he smiles.

The white dwarf and the red giant

Only about ten recurrent novas occur in the Milky Way and surrounding galaxies, explains Sumner Starrfield.

Whereas normal novas explode roughly “every 100,000 years”, recurrent novas repeat their explosions on a human timescale.

They occur in binary star systems composed of a red giant, a cold dying star that has burned up all its hydrogen and greatly expanded – our Sun will meet the same fate in around five billion years’ time.

Its counterpart is a white dwarf, an even more advanced stage in the death of a star: the entire atmosphere is gone, and the core is gradually contracting until it becomes ultra-compact and extremely dense.

The difference in size between the two stars is so great that it takes the white dwarf of T Coronae Borealis 227 days to orbit the red giant.

The pairing is so close that the material ejected by the red giant accumulates close to the white dwarf’s surface.

Once this disk of matter, with a mass equivalent to that of the Earth, has accumulated on the white dwarf – which takes around 80 years – it heats up enough to trigger an uncontrolled thermonuclear reaction, develops Sumner Starrfield.
The result is “a big explosion and, within seconds, the temperature rises by 100 to 200 million degrees”, adds Joachim Krautter, a retired German astronomer who has studied the nova. After a few days, the star regains its normal luminosity.
The explosion will be scrutinized by numerous instruments, including the James Webb Space Telescope.