News Release

Missing link found: supernovae give rise to black holes or neutron stars

Scientists have found a direct link between the explosive deaths of massive stars and the formation of black holes

Peer-Reviewed Publication

Weizmann Institute of Science

Scientists have found a direct link between the explosive deaths of massive stars and the formation of the most compact and enigmatic objects in the Universe: black holes and neutron stars. With the help of the European Southern Observatory’s Very Large Telescope (ESO’s VLT), an international team led by the Weizmann Institute of Science was able to observe the aftermath of a supernova explosion in a nearby galaxy, finding evidence of the mysterious compact object it left behind. The study is being published today in Nature.

“Researchers have long believed that a compact remnant is produced at the center of a massive star explosion,” says the study’s lead author Dr. Ping Chen, a postdoctoral fellow in the lab of Prof. Avishay Gal-Yam in Weizmann’s Particle Physics and Astrophysics Department. “But a direct link between supernova explosions and newly formed compact objects has been elusive. In this work, we establish such a direct link.”

When massive stars reach the end of their lives, they collapse under their own gravity so rapidly that a violent explosion known as a supernova ensues. Astronomers believe that after all the excitement of the explosion, what is left is the ultra-dense core, or compact remnant, of the star. Depending on how massive the star is, the compact remnant will either be a neutron star – an object so dense that a tablespoon of its material would weigh as much as Mount Everest – or a black hole, an even denser object from which nothing, not even light, can escape.  

But while astronomers had found many clues hinting at this chain of events in the past, direct evidence of a supernova leaving behind a compact remnant has been elusive.

The team’s lucky break came in May 2022, when the supernova SN2022jli was discovered in the spiral arm of a nearby galaxy, NGC 157, located 75 million light-years away. By turning their attention to the fallout of this explosion, the scientists were able to find the link connecting a supernova to the compact object it left behind — all thanks to a companion star.

Most massive stars are in orbit with a companion star in what is known as a binary system, and the star that caused SN 2022jli was no exception. Remarkably, the companion star survived the violent death of its partner, so that this star and the left-over compact object kept orbiting each other, an unusual occurrence after such a powerful explosion.

“In this work, we observed a newly formed compact object and its companion,” Chen says. “For the first time, we see how the newly formed neutron star or black hole interplays with its companion.”

This interplay was spotted in the form of periodic movements of hydrogen gas and of regular fluctuations in the system’s visible brightness, with bursts of gamma-rays also detected. The observations were made possible thanks to a fleet of instruments on the ground and in space, including X-shooter on ESO's VLT, in Chile’s Atacama Desert.

Putting these clues together, the team found that when the companion star interacted with the material thrown out during the supernova explosion, its hydrogen-rich atmosphere became puffier than usual. Then, each time the compact object zipped through the companion’s atmosphere on its orbit, it could steal hydrogen gas, forming a hot disc of matter around itself. This periodic stealing of matter, or accretion, produced lots of energy that was picked up as regular changes of brightness in the observations.

Even though the team could not observe the compact object directly, they concluded that this energy stealing could only be due to a neutron star or a black hole sucking up matter from the companion star’s puffy atmosphere. “Our research was like solving a puzzle by gathering all possible evidence,” Chen says. “All these pieces lined up, leading to the truth.”

With the presence of a black hole or neutron star confirmed, there is still plenty to unravel about this enigmatic system, including the exact nature of the compact object. Next generation telescopes such as ESO’s Extremely Large Telescope, scheduled to begin operation later this decade, will help with this, allowing astronomers to reveal unprecedented details of this important binary system. 

In addition to Chen and ​​Gal-Yam, team members includes Jesper Sollerman (The Oskar Klein Centre, Department of Astronomy, Stockholm University, Sweden [OKC DoA]), Steve Schulze (The Oskar Klein Centre, Department of Physics, Stockholm University, Sweden [OKC DoP]), Richard Post (Post Observatory, Lexington, USA), Chang Liu (Department of Physics and Astronomy, Northwestern University, USA [Northwestern]; Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, USA [CIERA]), Eran Oded Ofek (Weizmann Institute), Kaustav Kashyap Das (Cahill Center for Astrophysics, California Institute of Technology, USA [Cahill Center]), Christoffer Fremling (Caltech Optical Observatories, California Institute of Technology, USA [COO]; Division of Physics, Mathematics and Astronomy, California Institute of Technology, USA [PMA]), Assaf Horesh (Racah Institute of Physics, The Hebrew University of Jerusalem, Israel), Boaz Katz (Weizmann Institute), Doron Kushnir (Weizmann Institute), Mansi Kasliwal (Cahill Center), Shri Kulkarni (Cahill Center), Dezi Liu (South-Western Institute for Astronomy Research, Yunnan University, China [Yunnan]), Xiangkun Liu (Yunnan), Adam Miller (Northwestern; CIERA), Kovi Rose (Sydney Institute for Astronomy, School of Physics, The University of Sydney, Australia), Eli Waxman (Weizmann Institute), Sheng Yang (OKC DoA; Henan Academy of Sciences, China), Yuhan Yao (Cahill Center), Barak Zackay (Weizmann Institute), Eric Bellm (DIRAC Institute, Department of Astronomy, University of Washington, USA), Richard Dekany (COO), Andrew Drake (PMA), Yuan Fang (Yunnan), Johan Peter Uldall Fynbo (The Cosmic DAWN Center, Denmark; Niels Bohr Institute, University of Copenhagen, Denmark), Steven Groom (IPAC, California Institute of Technology, USA [IPAC]), G. Helou (IPAC), Ido Irani (Weizmann Institute), Theophile Jegou du Laz (PMA), Xiaowei Liu (Yunnan), Paolo Mazzali (Astrophysics Research Institute, Liverpool John Moores University, UK; MaxPlanck Institute for Astrophysics, Germany), Don Neill (PMA), Yu-Jing Qin (PMA), Reed Riddle (COO), Amir Sharon (Weizmann Institute), Nora Linn Strotjohann (Weizmann Institute), Avery Wold (IPAC), and Lin Yan (COO).

Prof. Avishay Gal-Yam is head of the Center for Experimental Physics and of the André Deloro Institute for Advanced Research in Space and Optics. His research is supported by the Norman E Alexander Family M Foundation ULTRASAT Data Center Fund.
Prof. Gal-Yam is the incumbent of the Arlyn Imberman Professorial Chair.


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