Astronomers have discovered four stars that could explode into supernovas

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An international team of astronomers has published their findings in Nature Astronomy today (May 13) that a quadruple star system discovered in 2017 and recently observed at the University of Canterbury Mt. John Observatory could represent a new channel through which thermonuclear supernova explosions can occur in the universe.

To find HD74438, researchers used Gaia-survey ESO’s of more than 100,000 Milky Way stars in 2017 to find the uncommon double-binary star system.

Over the course of several years, further observations of HD 74438 were made in order to determine the exact positions of the four stars in the system. In New Zealand and South Africa, high-resolution spectrographs were used to obtain measurements of the astronomical object.

For this stellar quadruple, astronomers were able to identify that it is composed of a short-period binary orbiting another short-period binary with a longer orbital period (2+2 configuration).

Due to its young age (just 43 million years old), the quadruple system was found to be among those with the shortest outer orbital period in the Milky Way Galaxy. It is also a component of the young open star cluster IC 2391. (six years).

An article published today in the journal Nature Astronomy claims to have discovered that the outer binary system is gravitationally altering its younger twin, which is making it more eccentric. Gravitational dynamics can lead to numerous collisions and mergers, resulting in white dwarfs with masses slightly below Chandrasekhar’s limit, according to state-of-the-art models. These white dwarf stars are capable of producing a thermonuclear supernova explosion as a result of their mass transfer or mergers.

University of Canterbury Mt. John Observatory Director Associate Professor Karen Pollard of the School of Physical and Chemical Sciences, University of Canterbury; Dr. C. Clare Worley and Professor Gerry Gilmore, both of the Institute of Astronomy, Cambridge University, U.K.; and UC alumni Dr. C. Clare Worley and Professor Gerry Gilmore.

At the University of Canterbury Mt. John Observatory, Associate Professor Pollard claims that high-precision and high-resolution spectroscopic observations were made using the Hercules spectrograph on the 1.0m McLellan telescope.

A star like our sun will become a white dwarf at the end of its existence and its mass cannot exceed the so-called Chandrasekhar limit (approximately 1.4 times the mass of the sun),” she says. White dwarfs can’t exceed this limit. “A thermonuclear supernova can occur if mass transfer or merging processes lead it to collapse. Interestingly, 70% to 85% of all thermonuclear supernovae are currently thought to have been caused by white dwarfs with sub-Chandrasekhar masses exploding.. These white dwarf stars can explode as a thermonuclear supernova explosion if they merge or transfer mass.”

According to Associate Professor Pollard, star quadruples such as HD 74438 indicate a new avenue for forming thermonuclear supernova explosions in the Universe.

Recent gravitational wave emission detections can be attributed to binary star mergers, which are now known to play a significant role in a wide variety of astronomical processes. It is possible to extract fundamental stellar properties like mass, radius, and luminosity more accurately from binary stars than from single stars. As such, they serve as the foundation upon which other branches of astrophysics rest.

Fewer than a tenth of all multiple systems have stellar quadruples. When these high-order multiples merge, they may also be the source of thermonuclear supernovae because of the mass transfer and collisions that take place in the process. Even though the evolutionary pathways leading to the progenitors of such supernova explosions are still hotly contested, these supernovae serve as standard candles for correcting the universe’s distance scale.

Nature Astronomy has released an article titled, “A spectroscopic quadruple as a putative progenitor of sub-Chandrasekhar type Ia supernovae.

Further information: Thibault Merle et al, A spectroscopic quadruple as a possible progenitor of sub-Chandrasekhar type Ia supernovae, Nature Astronomy (2022). DOI: 10.1038/s41550-022-01664-5

Journal information: Nature Astronomy

Source: Canterbury Christ Church University