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Red supergiants are a class of stars that end their lives in supernova explosions. Their life cycles are not understood, partly due to difficulties in measuring their temperature. For the first time, astronomers are developing a correct method to determine the surface temperature of a red surface.

Stars come in a wide range of sizes, dimensions and inscriptions. Our sun is thought to be a relatively small sample, especially compared to something like Betelgeuse called supergiant red. The red supergiants of the stars are more than nine times the size of our solar system, and all of this mass means that when they die they do so with great fury in a massive explosion called a supernova, in particular something called a supernova Type-II.

Type II supernovae seed the cosmos with essential elements for life; therefore, researchers are willing to find out more about them. At this time, there is no way to accurately predict supernova explosions. One piece of this puzzle lies in understanding the nature of the red supergiants that precede supernovae.

Despite the fact that red supergiants are extremely bright and visible at great distances, it is difficult to detect important features about them, including their temperature. This is due to the complex structures of the upper atmosphere leading to inconsistencies in temperature measurement that may work with other types of stars.

“To measure the temperature of red supergiants, we had to find a visible, or spectral, building that was not affected by their complex high aromas,” said graduate student Daisuke Taniguchi from the Department of Astronomy at the University of Tokyo. The individual candidates’ chemical lines were called signature lines, but there was not a single line that expressed the temperature on its own. However, by looking at the ratio of two different but related lines – iron ones – we found that the ratio itself was related to temperature. And he did so in a consistent and predictable manner. “

Taniguchi and his team saw candidate stars with an instrument called WINERED that connects to telescopes to measure the celestial properties of distant objects. They measured the iron absorption lines and calculated the ratios to estimate the individual temperature of the stars. Combining these temperatures with accurate distance measurements obtained by the European Space Agency’s Gaia space observatory, the researchers calculated the brightness, or power of the stars, and found their results theoretically.

“We still have a lot to learn about supernovae and related objects and onions, but I think this research will help astronauts fill some gaps,” said Taniguchi. “The giant star Betelgeuse ( on the shoulders of Orion) to go to supernova in our lives; in 2019 and 2020 it decreased unexpectedly. It would be interesting if we could make a prediction and when it might go to supernova. I hope our new approach contributes to this effort and more. “

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Journal article

Daisuke Taniguchi, Noriyuki Matsunaga, Mingjie Jian, Naoto Kobayashi, Kei Fukue, Satoshi Hamano, Yuji Ikeda, Hideyo Kawakita, Sohei Kondo, Shogo Otsubo, Hiroaki Sameshima, Keiichi Takenaka and Chikako Yasui. Effective temperature of red supergiants measured from line depth ratios of iron lines in the YJ bands, 0.97–1.32 μm. Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa3855.

http: // doi.org /10.1093 /mnras /staa3855

Funding

The WINERED was developed by the University of Tokyo and the High-resolution Infrared Spectroscopy (LiH) Laboratory, Kyoto Sangyo University under the financial support of Grants-In-Aid, KAKENHI, from the Japan Society for the Advancement of Science (JSPS; Nos .; 16684001, 20340042, and 21840052) and the MEXT-supported Program for the Strategic Research Foundation of Private Universities (nos. S0801061 and S1411028). This work has been supported by the Masason Foundation. DT acknowledges financial support from Toyota / Dwango AI scholarship and Iwadare Scholarship Foundation in 2020. NM, NK and HK acknowledge financial support for KAKENHI No. 18H01248. NK also acknowledges support through the Japan-India Science Cooperation Program between 2013 and 2018 under an agreement between the JSPS and the Department of Science and Technology (DST) in India. KF acknowledges financial support from KAKENHI No. 16H07323. HS acknowledges financial support from KAKENHI No. 19K03917.

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