We may have witnessed a black hole or neutron star being born from a dying star, according to analysis of an unusual rhythmic supernova.
When a star runs out of the fuel it needs for nuclear fusion, it goes supernova and collapses in on itself, falling onto the core and blasting out material in a bright explosion.
Astronomers have evidence linking extremely massive supernovae to the formation of ultra-dense remnants like neutron stars and black holes, collectively called compact objects, but this is from long after the star has exploded. A star has never been caught in the act of going supernova and birthing a dense descendant.
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Now, at Queen鈥檚 University Belfast, UK, and his colleagues think they may have glimpsed evidence of a neutron star or black hole being born from a supernova, called SN 2022jli, because it has strange undulations in the light it gives off. 鈥淲e鈥檝e never seen anything quite like this,鈥� says Moore.
Unlike normal supernova explosions, which tend to fade after they reach their peak after about a month, SN 2022jli faded before growing bright again, at 1 per cent of its maximum brightness. This continued in a pattern of periodic brightening and fading around every 12 days for more than six months, which hasn鈥檛 been seen in any other supernovae.
The supernova, which looks to have come from a massive star collapsing while in orbit around another star, has other unusual properties too. These include an extremely bright first peak to the explosion and spectroscopic measurements of it show strong light from elements that don鈥檛 fit with the normal timeline of such supernovae, says Moore.
This evidence suggests that the supernova either had an unusual parent, such as an extremely stripped-back star called a Wolf-Rayet star, or has given birth to a compact object, which is making the supernova appear unusual, says Moore. However, his team doesn鈥檛 have enough evidence to conclude either way.
Another group 鈥� at the Weizmann Institute of Science in Israel and his colleagues 鈥� has separately observed SN 2022jli and has . The team thinks these emissions come from the leftover star in the pair having material sucked away and then ejected by the neutron star or black hole that is left over. The group also detected gamma rays from the direction of the supernova, which could be from the compact object too.
While astronomers are fairly sure that supernovae form compact objects, understanding what kind of star went supernova and how it happened could give us crucial information on how black holes and neutron stars form, says at the University of Sheffield, UK.
The combination of observations suggests that we really are witnessing the birth of a compact object, says Maund. 鈥淭hey鈥檝e tried to make this complete picture, which I think is very convincing.鈥�
Astrophysical Journal Letters
