Supernova ‘missing link’ between dead stars, black holes discovered

When stars much more massive than our sun reach the end of their lives, their own gravity makes them collapse so fast that it causes a violent explosion called a supernova. Astronomers are of the opinion that after the explosion, the ultra-dense core or “compact remnant” of the star is all that remains. And, depending on how much more massive the star was, the remnant will become either a neutron star or a black hole.

A neutron star is an object so dense that a teaspoon of its material would weigh around a trillion kilograms on Earth. A black hole is even more dense with gravity so strong that nothing, not even light, can escape.

This compact remnant theory is held under the many clues hinting about the chain of events as a star explodes. But astronomers have never seen direct evidence of a supernova leaving behind a compact remnant, according to ESO. But that changed in 2022 when South African amateur astronomer Berto Monard discovered the supernova SN 2022jli in the spiral arm of the nearby galaxy NGC 157. It was located about 75 million light-years away and looking at its aftermath, researches found peculiar behaviour.

Typically, the brightness of most supernovae fade away with time in a gradual decline. But SN 2022jli behaved very differently — its overall brightness decreases but not in a gradual light curve. Instead, it oscillates up and down every 12 days or so.

The researchers put together all the clues and conclude that this pattern is caused by a compact remnant interacting with the supernova’s companion star that survived the explosion.