What Is Causing The Mysterious Dimming Of Supergiant Star Betelgeuse? Mystery Solved!

According to scientists, a cloud of stardust caused Betelgeuse, one of the brightest stars in the night sky, to become noticeably darker nearly two years ago.

Astronomers were perplexed when, in late 2019, they noticed the red supergiant had lost more than two-thirds of its brightness — enough to be seen with the naked eye, prompting speculation that the decrease in brightness was a sign of its impending death in a spectacular supernova explosion.

However, the dimming lasted only a few months, and Betelgeuse returned to its original brightness in April 2020.

Betelgeuse is a red supergiant — a more massive star and has a much shorter lifespan than the Sun — and it is expected to die in a spectacular supernova explosion within the next 100,000 years.

This event would provide a spectacle unlike anything seen by Earthlings in centuries: the last supernova in the Milky Way that could be observed from Earth was in 1604, and Betelgeuse is so close to our planet that its supernova will be bright enough to be visible during the day for weeks.

Many astrophysicists, however, cautioned that the supernova speculation was speculative. They noted that the dimming was most likely caused by more mundane mechanisms, such as a blob of unusually cold matter appearing on the star's surface in what's known as a convective cell or a cloud of dust crossing the star's line of sight.

Now, astrophysicist Miguel Montargès of the Paris Observatory and his colleagues have discovered that the ‘great dimming' was most likely caused by a combination of both of these factors.

An international team of researchers investigated the mysterious “great dimming” using the Very Large Telescope in Chile's Atacama Desert; the team captured a series of high-resolution images of the star in January 2019, December 2019, January 2020, and March 2020. Betelgeuse is more than 16 times the mass of the Sun and 764 times its width — so large that if it were located in the center of the Solar System, it would engulf all of the planets' orbits up to Mars.

This makes it one of the few stars that astronomers can resolve as a disk rather than a single dot of light, according to Montargès, who has been studying Betelgeuse for a decade.

The scientists discovered the dimming was caused by the formation of stardust, which partially obscured the star, in a study published in the journal Nature.

According to scientists, the surface of Betelgeuse changes regularly as giant bubbles of the gas move, shrink, and swell within the star, a phenomenon known as pulsation.

When a portion of the surface cooled down shortly after the ejection, the temperature drop was sufficient for the heavier elements in the gas, such as silicon, to condense into solid dust.

Montargès and his colleagues say in the journal Nature about their new study."Our results confirm that the Great Dimming is not an indication of Betelgeuse’s imminent explosion as a supernova," 

However, "some red supergiants may show little or no sign of their impending core collapse, years to weeks before it happens," "Therefore, although the current mass-loss behavior of Betelgeuse does not appear to forebode its demise, it remains possible that it may explode without warning."