Betelgeuse illustration. Credit: NASA, ESA, and E. Wheatley (STScI)
Betelgeuse (α Orionis) is the intense reddish star situated in the shoulder of the Orion constellation and can be seen by the naked eye in the night sky.
From October 2019 to March 2020, Betelgeuse showed a strange dimming, recording the attention and creativity of both astronomers and the general public. While being a variable star that displays routine and often irregular light modification, this dimming is the most substantial observed in the last 50 years. It ended up being fainter by more than 2.5 times, which even can be observed by the naked eye in the night sky. Several situations have actually been advanced by astronomers worldwide: pre-phase of supernova surge, obscuring dust, or modifications in the photosphere of the star.
A brand-new research study led by Prof. ZHAO Gang from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) clarifies the nature of the mystical dimming of Betelgeuse. Scientists from Shandong University and the University of Missouri (U.S.A.) likewise joined this research study.
The research study was released in Nature Communications today (August 5, 2021).
During completion of 2019 and the start of 2020, Betelgeuse (α Orionis) ended up being fainter by more than 2.5 times and this is the most substantial dimming observed in the current years. Credit: Alena Alexeeva and REN Dayong
Betelgeuse is the brightest star in the night sky in the near-infrared wavelength variety. This is the most appropriate wavelength variety for examining red supergiants like Betelgeuse.
The research study group examined the high-resolution near-infrared spectra of Betelgeuse gotten at Weihai Observatory of Shandong University on January 31, March 19, April 4, and April 6, 2020, covering the dimming and post-dimming stages. “Taking our advantage in spectroscopic analysis, we aim to understand the possible cause of the mysterious dimming of Betelgeuse,” stated Prof. ZHAO Gang, the matching author of this research study.
To this end, the group established an unique strategy for figuring out the efficient temperature levels of red supergiants.
“Our method is based on the measurement of titanium oxide (TiO) and cyanide (CN) molecular lines in stellar spectra. The cooler a star is, the more these molecules can form and survive in its atmosphere and the molecular lines are stronger in the stellar spectrum. In a hotter atmosphere, these molecules dissociate easily and do not survive,” stated Dr. Sofya Alexeeva, the very first author of this research study.
“We have found that at the minimum of its luminosity, the effective temperature of Betelgeuse on January 31, 2020, was 3476 Kelvins. However, after it recovered its brightness, on April 6, 2020, the effective temperature was 3646 Kelvins. The changing of the effective temperature by 170 K is sufficient to explain this mysterious dimming,” stated Dr. Sofya Alexeeva.
What could result in a temperature level stop by 170 K? It might be brought on by a big dark star-spot on the surface area of Betelgeuse. The existence of areas on red supergiants is a popular phenomenon. These areas are likely an effect of convective circulations or cool convective cells, which are commonly thought to be present in such stars.
“Our findings offer insight into the nature of red supergiant stars, the main contributors to the enrichment of heavy elements in the Universe,” stated Prof. ZHAO Gang.
Reference: 5 August 2021, Nature Communications.
10.1038/s41467-021-25018-3
