An worldwide group of astronomers has actually observed the very first example of a brand-new kind of supernova. The discovery, verifying a forecast made 4 years back, might cause brand-new insights into the life and death of stars. The work was released on June 28, 2021, in Nature Astronomy.
“One of the main questions in astronomy is to compare how stars evolve and how they die,” stated Stefano Valenti, teacher of physics and astronomy at the University of California, Davis, and a member of the group that found and explained supernova 2018zd. “There are many links still missing, so this is very exciting.”
There are 2 recognized kinds of supernova. A core-collapse supernova takes place when a huge star, more than 10 times the mass of our sun, lacks fuel and its core collapses into a great void or neutron star. An atomic supernova takes place when a white dwarf star — the remains of a star as much as 8 times the mass of the sun — takes off.
In 1980, Ken’ichi Nomoto of the University of Tokyo forecasted a 3rd type called an electron capture supernova.
What keeps most stars from collapsing under their own gravity is the energy produced in their main core. In an electron capture supernova, as the core lacks fuel, gravity forces electrons in the core into their atomic nuclei, triggering the star to collapse in on itself.
Supernova 2018zd, marked with a white circle on the borders of galaxy NGC2146, is the very first example of a brand-new, 3rd kind of supernova forecasted 40 years back. Composite image with information from the Hubble Space Telescope, Las Cumbres Observatory and other sources. Credit: Joseph Depasquale, STScI
Evidence from late spectrum
Supernova 2018zd was discovered in March 2018, about 3 hours after the surge. Archival images from the Hubble Space Telescope and Spitzer Space Telescope revealed a faint item that was most likely the star prior to surge. The supernova is fairly near Earth, at a range of about 31 million light years in galaxy NGC2146.
The group, led by Daichi Hiramatsu, college student at UC Santa Barbara and Las Cumbres Observatory, gathered information on the supernova over the next 2 years. Astronomers from UC Davis, consisting of Valenti and college students Azalee Bostroem and Yize Dong, contributed a spectral analysis of the supernova 2 years after the surge, among the lines of proof showing that 2018zd was an electron capture supernova.
“We had a really exquisite, really complete dataset following its rise and fade,” Bostroem stated. That consisted of really late information gathered with the 10-meter telescope at the W.M. Keck Observatory in Hawaii, Dong included.
Theory forecasts that electron capture supernovae ought to reveal an uncommon outstanding chemical spectrum years later on.
“The Keck spectra we observed clearly confirm that SN 2018zd is our best candidate to be an electron capture supernova,” Valenti stated.
The late spectrum information were not the only piece of the puzzle. The group browsed all released information on supernovae, and discovered that while some had a few of the indications forecasted for electron capture supernovae, just SN 2018zd had all 6: an evident progenitor star of the Super-Asymptotic Giant Branch (SAGB) type; strong pre-supernova mass loss; an uncommon outstanding chemical spectrum; a weak surge; little radioactivity; and a neutron-rich core.
“We started by asking ‘what’s this weirdo?’ Then we examined every aspect of SN 2018zd and realized that all of them can be explained in the electron-capture scenario,” Hiramatsu stated.
This composite picture of the Crab Nebula was put together by integrating information from 5 telescopes covering almost the whole breadth of the electro-magnetic spectrum. Credit: NASA, ESA, NRAO/AUI/NSF and G. Dubner (University of Buenos Aires)
Explaining the Crab Nebula
The brand-new discoveries likewise brighten some secrets of the most well-known supernova of the past. In A.D. 1054 a supernova happened in the Milky Way. According to Chinese records it was so intense that it might be seen in the daytime for 23 days, and during the night for almost 2 years. The resulting residue — the Crab Nebula — has actually been studied in terrific information. It was formerly the very best prospect for an electron capture supernova, however this doubted partially due to the fact that the surge occurred almost a thousand years back. The brand-new outcome increases the self-confidence that the occasion that formed the Crab Nebula was an electron capture supernova.
“I am very pleased that the electron capture supernova was finally discovered, which my colleagues and I predicted to exist and have a connection to the Crab Nebula 40 years ago. This is a wonderful case of the combination of observations and theory,” stated Nomoto, who is likewise an author on the present paper.
Read Discovery of a New Type of Stellar Explosion – An Electron-Capture Supernova – Illuminates a Medieval Mystery for more on this research study.
Reference: “The electron-capture origin of supernova 2018zd” by Daichi Hiramatsu, D. Andrew Howell, Schuyler D. Van Dyk, Jared A. Goldberg, Keiichi Maeda, Takashi J. Moriya, Nozomu Tominaga, Ken’ichi Nomoto, Griffin Hosseinzadeh, Iair Arcavi, Curtis McCully, Jamison Burke, K. Azalee Bostroem, Stefano Valenti, Yize Dong, Peter J. Brown, Jennifer E. Andrews, Christopher Bilinski, G. Grant Williams, Paul S. Smith, Nathan Smith, David J. Sand, Gagandeep S. Anand, Chengyuan Xu, Alexei V. Filippenko, Melina C. Bersten, Gastón Folatelli, Patrick L. Kelly, Toshihide Noguchi and Koichi Itagaki, 28 June 2021, Nature Astronomy.
DOI: 10.1038/s41550-021-01384-2
The research study belongs to the Global Supernova Project, led by Professor Andrew Howell at UCSB and Las Cumbres Observatory. Additional co-authors are: Curtis McCully and Jamison Burke, Las Cumbres Observatory and UCSB; Jared Goldberg and Chengyuan Xu, UCSB; Schuyler Van Dyk and Gagandeep Anand, California Institute of Technology; Keiichi Maeda, Kyoto University; Takashi Moriya, National Astronomical Observatory of Japan; Nozomu Tominaga, Konan University, Kobe, Japan; Griffin Hosseinzadeh, Center for Astrophysics, Harvard & Smithsonian; Iair Arcavi, Tel Aviv University, Israel; Peter Brown, Texas A&M University; Jennifer Andrews, Christopher Bilinski, G. Grant Williams, Paul Smith, Nathan Smith and David Sand, Steward Observatory, University of Arizona; Alexei Filippenko, UC Berkeley; Melina Bersten and Gastón Folatelli, Instituto de Astrofísica de La Plata and Universidad Nacional de La Plata, Argentina; Patrick Kelly, University of Minnesota; Toshi- conceal Noguchi, Noguchi Astronomical Observatory and Koichi Itagaki, Itagaki Astronomical Observatory, Japan. The work was partially supported by grants from the National Science Foundation and NASA.
