Betelgeuse

John Herschel 1846 (cropped)

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Betelgeuse pulsating UV (HST)

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Betelgeuse AAVSO 2019

Eso2003c

Orion Head to Toe

Betelgeuse is a red supergiant star located in the constellation of Orion. It is one of the largest stars visible to the naked eye and is distinguished by its deep red color. Betelgeuse is approximately 642.5 light-years from Earth and is one of the brightest stars in the night sky, with a varying magnitude that usually ranks it as the tenth-brightest star. Its apparent magnitude varies between +0.0 and +1.3, which is an indicator of its variable nature.

Characteristics

Betelgeuse is classified as a M-type supergiant star, indicating it has a relatively low temperature but a high luminosity due to its large size. The star has a mass about 20 times that of the Sun, but its radius is over 700 times larger. This immense size means that if Betelgeuse were placed at the center of our Solar System, its surface might extend out to the orbit of Jupiter or beyond, engulfing the inner planets, including Earth.

The star is nearing the end of its life and is expected to explode as a supernova within the next million years, an event that would be visible from Earth even during the daytime. Betelgeuse's age is estimated to be around 8 to 8.5 million years old, relatively young in stellar terms, but massive stars like Betelgeuse consume their nuclear fuel at a much faster rate than smaller stars, leading to their premature demise.

Variability

Betelgeuse is a semiregular variable star, which means its brightness varies irregularly. Over the past few centuries, astronomers have recorded its magnitude fluctuating between about +0.0 and +1.3. These changes in brightness are thought to be caused by a combination of factors, including pulsations of the star's outer layers, large convective cells on the star's surface, and possibly dust expelled into space by the star.

In late 2019 and early 2020, Betelgeuse attracted significant attention from both professional and amateur astronomers due to an unprecedented dimming event, where its brightness decreased by approximately one-third. This led to speculation that the star might be about to go supernova. However, the star subsequently returned to its normal brightness, with studies suggesting that the dimming was caused by a cool, dense spot on the star's surface and a dust cloud that had formed in front of the star, rather than being a precursor to a supernova.

Observation and Significance

Betelgeuse has been observed since ancient times and holds significance in various cultures around the world. It is designated as Alpha Orionis, being the alpha star of the constellation Orion, despite not being the brightest star in the constellation (that title belongs to Rigel). Its position on the shoulder of Orion makes it easy to locate in the night sky.

Astronomically, Betelgeuse is significant not only because of its size and brightness but also because it offers scientists a rare opportunity to study the late stages of stellar evolution. Observations of Betelgeuse and its behavior provide valuable insights into the life cycle of red supergiants and the processes leading up to their eventual supernova explosions.

Future

The future of Betelgeuse remains a subject of much speculation and anticipation. When it finally explodes as a supernova, it will be one of the most spectacular events observable from Earth, potentially outshining the full moon and being visible even during the day. However, given the vast timescales involved in stellar evolution, it is impossible to predict exactly when this event will occur.