Dim, explode? The legend of Betelgeuse – the immortal star in the sky

Introduction: Betelgeuse has been observed to dim since December 2019, and scientists have speculated whether Betelgeuse is about to explode. It stands to reason that its supernova explosion will last brightly for about a month, which must be a beautiful sight, but within a few months, Betelgeuse will return to its previous brightness. Although it was an empty joy, it helped scientists further understand interstellar matter.

A red supergiant star in the constellation Orion: Betelgeuse, arguably one of the most famous stars in the night sky, came as a surprise to astronomers in 2020 when it began to dim unexpectedly. In fact, it got so dark that scientists thought it was teetering on the brink of a cataclysm...until it didn't, which didn't happen.

And all this can start from December 2019-at the end of the year, the new coronavirus began to ravage the earth, and a series of legendary events about the light change of Betelgeuse also began with it.

While scientists scrambled to trace the source of the outbreak, astronomers had to be drawn to a different kind of anxiety. Betelgeuse's brightness is dimming significantly. Follow-up observations in late 2019 and the first few weeks of 2020 showed that the star had dimmed to about 36 percent of its normal brightness. This has also led some astronomers to believe that Betelgeuse's life is about to enter a countdown and may turn into a supernova explosion.

A supernova occurs when a star's "fuel" runs out and the core collapses under its own gravity. Astronomers can only observe supernovas of faint stars in distant galaxies, so the idea of ​​watching Betelgeuse explode in real time above our heads is — in some ways — far more exciting than the stars themselves.

This comparison image shows Betelgeuse before and after its unprecedented dimming, taken in January and December 2019 with the SPHERE instrument on ESO's Very Large Telescope. The results show how much the star has faded and how its apparent shape has changed.

The brightness of the explosion must be very high so that we can see the explosion from Earth. We can even see it exploding during the day as a bright spherical object, like Venus at dusk. And the light from the explosion lasts for months, then fades out within a year or two.

It's a pity that Betelgeuse is a little "stage fright". After "teasing" astronomers for months, the star began to slowly regain its former brightness in March. While astronomers don't know exactly what caused the star to dim, they have a few theories that sound like they might explain it.

A study published in June in The Astrophysical Journal Letters showed that not only was the star not on the verge of death, it actually didn't change in its luminosity at all. Instead, the paper suggests, Betelgeuse's signature bright light is temporarily blocked from our view by material shed by the star in the form of a cloud of dust.

Material is often shed during the life cycle of red supergiants like Betelgeuse. The material condenses around the star in the form of dust, the researchers say, meaning it absorbs some of the star's light and blocks our view from Earth. And observations by NASA's Hubble Space Telescope later in 2020 appear to support that theory.

In the first two small images, as seen in ultraviolet light with the Hubble Space Telescope, a large convective pool emerges from the star's surface, ejecting a jet of bright, hot plasma. In the third panel, the outgoing and outgoing gas rapidly expands outward. And it cooled to form a huge cloud of dust particles. The last image shows the massive dust cloud blocking almost a quarter of the light (as seen from Earth) on the star's surface. So, while we haven't been able to witness a giant star explode in the sky, we may have solved a cosmic age-old mystery, and perhaps this is the beginning.