The star Betelgeuse, a red supergiant among the largest known stars, with a radius that is about 800 times that of the Sun, was captured by surprise by the Japanese weather satellite Himawari-8: researchers from the University of Tokyo , in fact, they realized that the star appeared in the background of the photos taken of the Earth by the satellite, which also managed to immortalize the phenomenon known as the ‘Great Darkening’, i.e. the significant decrease in brightness of the star which took place between 2019 and 2020 which leads to hypothesize its imminent explosion as a supernova. The observations collected were published in the journal Nature Astronomy.
The Himawari-8 satellite operates in the wavelengths of visible light and infrared, ideal for studying the phenomenon, and is located outside the Earth’s atmosphere, a privileged point of view that allows it to have an advantage over the large telescopes located on the ground. The researchers led by Daisuke Taniguchi collected four and a half years of observations, including the six months in which the dimming of Betelgeuse took place: the data obtained show that the decrease in brightness was caused in equal parts by the cooling of about 140 degrees occurred on the star and from the condensation of dust due to the hot gas that surrounds it.
The results confirm the conclusions obtained by observers on the ground who have analyzed the phenomenon. The authors of the study also collected data on four other stars captured by the meteorological satellite, suggesting that these devices could become precious astronomical resources: this is because, according to the researchers, satellites exceed some of the limits of ground-based telescopes, for example by offering the possibility of more frequent observations.
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