Betelgeuse is one of the brightest and best-known stars in the sky. But over the past few years, it has begun to exhibit unusual behavior that has astronomers and space enthusiasts worried. In late 2019 and 2020, Betelgeuse has become dimmer than at any time in its century-long history of observation. This event became known as the “great dimming.” But after that, the star became bright again, reaching its maximum brightness in early 2021. So what is happening to Betelgeuse and how might it affect us here on Earth?
Variable stars
In general, stars are very stable and shine with the same brightness year after year. However, there are exceptions, and these stars are called variable stars. The most famous variable star is Mira, which was discovered by the German pastor David Fabricius in 1596. This star pulsates and regularly expands and contracts. Algol is another example of a variable star that is periodically eclipsed by a companion star. About 30 such variable stars can be seen in the sky, although care is required to notice the change in their brightness.
Betelgeuse is the brightest of the variable stars and the seventh brightest star in the sky (not counting the Sun). Sometimes Betelgeuse is nearly as bright as Rigel (the blue fourth brightest star in the constellation), and sometimes it is noticeably dimmer. The variation is caused by pulsations similar to those of Myra, though not as large and regular.
Supernovae
Some stars can briefly become extremely bright. These stars are called supernovae and are formed when an entire star ends its life in a massive explosion. Supernovae can be bright enough to be seen during the day, although this has only happened a few times in the past 1,000 years. A nearby bright supernova is an event that astronomers live for, but that few of us will ever see.
The mysterious behavior of Betelgeuse
Although Betelgeuse is a variable star, the big blackout in 2021 was extreme. Within a few months, it actually dimmed by about 60%. It was eventually shown to be caused by a cloud. Stars like Betelgeuse are constantly emitting gas and dust. A blob of gas in the wind the size of the star itself covered half of the star. In fact, images of the star showed that its southern half was missing. It turns out that some stars, like Betelgeuse, have weather.
But we still don’t know what caused the sudden brightening in early 2021. An impending supernova seems unlikely, since changes in brightness are a surface phenomenon and a supernova explosion occurs in the core of the star. However, the extraordinary increase in brightness may be due to the same dust cloud that caused the dimming, now reflecting light from the star to us and making it brighter.
Impact on Earth
If Betelgeuse does explode, it could have a significant impact on Earth. A supernova explosion could produce a new star in the sky that would be visible even during the day. In addition, supernovae are a source of cosmic rays and other forms of radiation that can be dangerous to life on Earth. However, Betelgeuse is about 700 light-years away, so the explosion will not have a direct effect on our planet.
In conclusion, Betelgeuse continues to amaze us with its mysterious behavior. Although we don’t know what caused the sudden brightening in early 2021, we can be sure that astronomers will continue to study this star and give us new insights into the cosmos.
