Paris. Astronomers are in effervescence. Between now and September, the massive explosion of a star located 3 thousand light years from Earth is expected, a rare cosmic phenomenon that can be observed in the night sky.
It will be at least the third time that humanity will be able to witness this phenomenon known as a nova, discovered for the first time by the Irish astronomer John Birmingham in 1866, and which occurred again in 1946.
The event takes place in a binary star system, T Coronae Borealis, belonging to the Corona Borealis constellation, which is usually too faint to be visible to the naked eye.
But approximately every 80 years, the interaction between these two stars triggers a nuclear explosion that revives their luminosity.
The light from the explosion travels through 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.
In statements to the AfpSumner Starrfield, an astronomer at Arizona State University, said he was very excited at the prospect of witnessing the spectacle.
The scientist has been working on the “T Coronae Borealis” phenomenon since the 1960s.
In recent days, he has been busy putting the finishing touches on a scientific paper in which he predicts what astronomers might discover by observing the nova, which could occur any time in the next five months.
“It could happen today. But I hope not!” he says with a smile.
White dwarf and red giant
Only about ten recurring novae occur in the Milky Way and surrounding galaxies, Starrfield explains.
While normal novae explode approximately “every 100,000 years,” recurring novae repeat their explosions on a human time scale due to the particular relationship between two stars.
One of them is a cold, dying star called a red giant, which has burned up all its hydrogen and expanded enormously, the same thing that will happen to our Sun in about 5 billion years.
The other is a white dwarf, which is in an even more advanced stage of star death: the entire atmosphere has disappeared and the core is progressively contracting until it becomes ultra-compact and extremely dense.
The difference in size between the two stars is so great that the white dwarf T Coronae Borealis takes 227 days to orbit the red giant.
The pairing is so close that matter ejected by the red giant accumulates near the surface of the white dwarf.
Once this disk of matter, with a mass equivalent to that of the Earth, has accumulated on the white dwarf, which takes about 80 years, it heats up enough to trigger an uncontrolled thermonuclear reaction, explains Starrfield.
This causes “a huge explosion and, in a few seconds, the temperature increases between 100 and 200 million degrees,” adds Joachim Krautter, a retired German astronomer who has spent many years studying the nova.
After a few days, the star regains its normal luminosity.
The explosion will be analyzed by numerous instruments, including the James Webb Space Telescope.
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– 2024-04-20 12:17:16
