Free Astronomy Magazine March-April 2024

MARCH-APRIL 2024 T his artist’s impression shows the process by which a massive star within a binary system becomes a supernova. This series of events occurred in the su- pernova SN 2022jli, and was revealed to researchers through observations with ESO’s Very Large Telescope (VLT) and New Technology Telescope (NTT). After a massive star exploded as a supernova, it left behind a compact object — a neu- tron star or a black hole. The companion star survived the explosion, but its at- mosphere became puffier as a result. The compact object and its companion star continued to orbit one another, with the compact object regularly stealing mat- ter from the other’s puffy atmosphere. This accretion of matter was seen in the researchers’ data as regular fluctuations of brightness, as well as periodic move- ments of hydrogen gas. [ESO/L. Calçada] “In SN 2022jli’s data we see a re- peating sequence of brightening and fading,” says Thomas Moore, a doctoral student at Queen’s Univer- sity Belfast, Northern Ireland, who led a study of the supernova pub- lished in the Astrophysical Journal. “This is the first time that repeated periodic oscillations, over many cy- cles, have been detected in a super- nova light curve,” Moore noted in his paper. Both the Moore and Chen teams be- lieve that the presence of more than one star in the SN 2022jli system could explain this behaviour. In fact, it’s not unusual for massive stars to be in orbit with a companion star in what is known as a binary system, and the star that caused SN 2022jli was no exception. What is remark- able about this system, however, is math of this explosion and found it to have a unique behaviour. After the explosion, the brightness of most supernovae simply fades away with time; astronomers see a smooth, gradual decline in the explosion’s ‘light curve’. But SN 2022jli’s behav- iour is very peculiar: as the overall brightness declines, it doesn’t do so smoothly, but instead oscillates up and down every 12 days or so. sented at the 243 rd American Astro- nomical Society meeting in New Or- leans, USA. The researchers’ lucky break came in May 2022, when South African am- ateur astronomer Berto Monard dis- covered the supernova SN 2022jli in the spiral arm of the nearby galaxy NGC 157, located 75 million light- years away. Two separate teams turned their attention to the after-