The 10th brightest star in the sky that has been in the spotlight for a sudden dimming, Betelgeuse, Orionis, or HIP 27989. Astronomers believe the red supergiant is nearing the end of its life, and when a star older than 10 times the mass of the Sun, it burns out in spectacular fashion. With its brightness at its lowest point in the last hundred years, it is believed that Betelgeuse will soon go supernova, exploding in a dazzling display that could be visible even in daylight.

The phenomenon has been studied ever since, and while some dismissed its impending explosion, astronomers mostly concluded that Betelgeuse’s dimming was the result of its surface cooling, the formation of a new dust lane around it, or both. All these results have been studied through data collected by ground-based optical telescopes.

Now, however, astronomers have a new way to study the stars: harness weather satellites orbiting Earth.

That’s what scientists showed in reference to a Japanese weather satellite that happened to observe Betelgeuse during its inexplicable darkening period.

The chance observations could mean a new tool for astronomers trying to understand how a red supergiant star loses mass and ultimately explodes as a supernova.


Great blackout

From October 2019 to February 2020, it dipped sharply to about two-thirds of its normal brightness. This so-called great dimming event led to speculation that it was about to explode as what scientists call a Type IIP supernova, which will undoubtedly happen within the next 100,000 years.

Ground-based telescopes can’t see through the dust and gas in the cosmos, because they need infrared vision. This is because the Earth’s atmosphere blocks radiation and X-rays, gamma rays, and most ultraviolet rays. Only space observatories and meteorological satellites can visualize aspects of this type, such as Himawari-8 of the Japan Meteorological Agency.

Daisuke Taniguchi, an astronomy student at the University of Tokyo and the paper’s first author, said he discovered that Betelgeuse is in Himawari-8’s field of view. “I realized that perhaps the Great Dimming of Betelgeuse could be investigated with this satellite,” said the scientist, according to the Emirates Herald news site.

Himawari-8 orbits since 2015 at 35,786 kilometers above the Earth’s equator since 2015 to study climate and natural disasters. Although the satellite is designed to obtain images of the Earth every 10 minutes, its field of action also allows it to observe stars.

Taniguchi and colleagues were able to see Betelgeuse in images taken during Himawari-8’s lifetime and measured its brightness approximately every 1.7 days between January 2017 and June 2021. With these data they concluded that the “great dimming” in 2019 and 2020 was caused by two factors in almost equal proportion: the star’s temperature dropped to about 140°C, and dust condensed from the hot gas around the star.

His conclusion is in broad agreement with what astronomers using ground-based telescopes concluded. For example, a study led by the Chinese Academy of Sciences cited giant sunspots and temperature fluctuations, while results from the European Southern Observatory’s Very Large Telescope in Chile and the Hubble Space Telescope suggested that Betelgeuse ejected a huge cloud of gas which was cooled and condensed to powder.

New scientific discoveries suggest that weather satellites could be used as space telescopes for astronomy. “It allows us to obtain high-rate time series of images in the mid-infrared, which are difficult to achieve with the usual astronomical instruments”, shows the study by Japanese astronomers. In addition to not being able to record near-infrared data, ground-based telescopes lose sight of some stars for a few months as the sun passes in front of them.

The authors have started using the Himawari-8 data for other stellar projects. “I think our concept of using a weather satellite as a space telescope is a great help for astronomy projects, notably in time-domain stellar astrophysics,” Taniguchi said, referring to the emerging area focused on how astronomical objects transform with time. time. His group is now using the Himawari-8 data to catalog how older stars vary in infrared brightness over time and also to look for fleeting infrared signals.


Bright as the full moon.

At about 548 light-years away, Betelgeuse is the closest red supergiant star to the Solar System. It has between 15 and 20 times the mass of the sun and is almost 900 times larger. If it were at the center of our Solar System, then Mercury, Venus, Earth, Mars, and the asteroid belt would all be inside Betelgeuse.

Once the star goes supernova, its brightness could be as bright as the full Moon for several months. The end result will be a neutron star in the center of a beautiful bubble of glowing material created by the explosion.

However, scientists still don’t know exactly how a red supergiant star behaves in the weeks before it explodes. Reported Emirates Herald, news and information agency.

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