This artists impression reveals the brilliant core of a Wolf– Rayet star surrounded by a nebula of product that has been expelled by the star itself. Credit: ESO/L. Calçada
We often think of supernova surges as inevitable for big stars. Astronomers have long believed at least one type of large star didnt end with a supernova.
Wolf-Rayet stars are amongst the most huge stars understood. They are at the end of their brief lives, however instead of simply running out of fuel and blowing up, they press out their external layers with an extremely effective excellent wind. This produces a surrounding nebula abundant in ionized helium, carbon, and nitrogen, but almost no hydrogen. The surface area temperature of the staying star can be over 200,000 K, making them the most luminous stars understood. But due to the fact that many of that light remains in the ultraviolet range, they are not especially intense to the naked eye.
Wolf-Rayet star. Credit: Hubble Legacy Archive, NASA, ESA– Processing & & Licence: Judy Schmidt
Even with the outer layers of a Wolf-Rayet star cast off, the central star is still a lot more massive than the Sun. You d figure its just a matter of time before it ends up being a supernova. No matter how far up the routine table fusion happens, it will ultimately lack fuel, leading to a core-collapse supernova. However we can see the spectra of components within a supernova, and we d never seen a spectrum that matched a Wolf-Rayet star. As our discovery of supernovae became prevalent, some astronomers started to wonder if Wolf-Rayet stars had a quiet death instead. The idea was that they would abandon sufficient external layers that the staying core would eventually just collapse directly into a black hole. No giant explosion needed. A silent death to a massive star.
Wolf-Rayet stars are amongst the most massive stars understood. The surface temperature level of the staying star can be over 200,000 K, making them the most luminescent stars known. Even with the external layers of a Wolf-Rayet star cast off, the main star is still much more enormous than the Sun. We can see the spectra of aspects within a supernova, and we d never seen a spectrum that matched a Wolf-Rayet star. Due to the fact that this supernova was recognized by spectra of the surrounding nebula, it isnt clear whether the explosion was an easy supernova, or whether it was a more intricate hybrid process where the upper layer of the star took off while the core collapsed directly to a black hole.
In a big star, different elements remain in layers prior to the star explodes. Credit: Itai Raveh
This most current study shows that at least some Wolf-Rayet stars do end up being supernovae. The team looked at the spectrum of a supernova understood as SN 2019hgp, which was found by the Zwicky Transient Facility (ZTF). The supernovas spectrum had bright emission light suggesting the existence of oxygen, neon, and carbon, however not hydrogen or helium. When the group took a look at the information more closely, they found these particular emission lines werent brought on by aspects of the supernova straight. Instead, they belonged to a nebula broadening far from the star at more than 1,500 km/s.
A spectra from SN 2019hgp. Credit: Itai Raveh
In other words, prior to the supernova took place, the progenitor star was surrounded by a nebula abundant in carbon, nitrogen, and neon, while lacking the lighter elements of hydrogen and helium. This matches the structure of a Wolf-Rayet star very well.
Due to the fact that this supernova was identified by spectra of the surrounding nebula, it isnt clear whether the explosion was a simple supernova, or whether it was a more complicated hybrid procedure where the upper layer of the star took off while the core collapsed directly to a great void. It will take more observations to determine the information. Whats clear is that a minimum of some Wolf-Rayet stars do not go quietly into the night.
Initially published on Universe Today.
Reference: “A WC/WO star exploding within a broadening carbon– oxygen– neon nebula” by A. Gal-Yam, R. Bruch, S. Schulze, Y. Yang, D. A. Perley, I. Irani, J. Sollerman, E. C. Kool, M. T. Soumagnac, O. Yaron, N. L. Strotjohann, E. Zimmerman, C. Barbarino, S. R. Kulkarni, M. M. Kasliwal, K. De, Y. Yao, C. Fremling, L. Yan, E. O. Ofek, C. Fransson, A. V. Filippenko, W. Zheng, T. G. Brink, C. M. Copperwheat, R. J. Foley, J. Brown, M. Siebert, G. Leloudas, A. L. Cabrera-Lavers, D. Garcia-Alvarez, A. Marante-Barreto, S. Frederick, T. Hung, J. C. Wheeler, J. Vinkó, B. P. Thomas, M. J. Graham, D. A. Duev, A. J. Drake, R. Dekany, E. C. Bellm, B. Rusholme, D. L. Shupe, I. Andreoni, Y. Sharma, R. Riddle, J. van Roestel and N. Knezevic, 12 January 2022, Nature.DOI: 10.1038/ s41586-021-04155-1.
