An international team of scientists have found the reasons behind the great dimming, an astronomical event when Betelgeuse, one of the largest stars that are visible to the naked eye in the night sky, lost two-thirds of its glow for a few months between December 2019 and April 2020. According to the latest study that was published in Nature on June 16, Betelgeuse lost its brightness because a dusty gas bubble emerging from the star shaded it. The second-brightest star of the Orion constellation and the tenth brightest star in the night sky was veiled after it ejected the gas bubble, a result of its outward pulsation, which further caused a sudden drop in the temperature at its stellar surface. Scientists combined the images taken by the European Southern Observatory’s Very Large Telescope in March 2020 with the images taken in December and January 2019. Using the combination, astronomers could clearly capture the darkening and change in Betelgeuse’s stellar surface, especially in the southern region of the star.

“For once, we were seeing the appearance of a star changing in real-time on a scale of weeks," said Miguel Montargès of Observatoire de Paris, who led the study, in a news release by Harvard Smithsonian Center for Astrophysics, United States.

The surface of the outward pulsating star regularly changes as it ejects gas bubbles that swell and shrink. Scientists found that mysterious darkening was caused due to the cooling down and condensation of heavy elements such as silicon into solid dust, leading to the temperature decrease.

The findings match the predictions of Andrea Dupree, an astronomer at Harvard Smithsonian Center for Astrophysics, who used Hubble Telescope data to detect the heated dense material moving through Betelgeuse’s atmosphere in the months that preceded the great dimming. According to Dupree, the material was moving away from the stellar surface at a speed of 3.2 lakh kilometre per hour. When it was far enough, it started cooling down and formed a dust cloud blocking the star’s light. As the dust cloud parted, the star returned to its original brightness in April 2020.

Is the Orion Losing Its Glow? Scientists Finally Have Answer to Dimming Betelgeuse

According to the latest study that was published in Nature on June 16, Betelgeuse lost its brightness because a dusty gas bubble emerging from the star shaded it.