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Betelgeuse is a bright star in the winter[note 1] constellation of Orion. It's also its second brightest star after Rigel — despite having been classified as the brightest one, at least in visible light.
Ford Prefect comes from a small planet near it.
Betelgeuse is a red supergiant star, an evolved high-mass star that has exhausted all the hydrogen at its core (see also stellar evolution) and is fusing there heavier elements before its final death as a luminous, bright-as-a-galaxy, supernova, and not only is one of the brightest stars of the sky, but also a very luminous and large one.
This star lies at a distance of around 640 light-years, being up to 150,000 times more luminous than our Sun and has an ill-defined diameter (due to the fact that its mean density is very low, virtually a vacuum by Earth's standard as well as that it has both a very extended atmosphere and it's "boiling", covered by large convective cells — see images) that ranges between roughly 900 and 1,200 times the one of our daystar. This had led some astronomers to think Betelgeuse may be contracting, but that contraction could not be real and simply be caused by said large convection-induced protrusions as the star rotates.
Like many other red supergiant stars, Betelgeuse's brightness changes irregularly. However, as of late 2019-early 2020, it had abnormally faded, losing 1 magnitude (ie, becoming 2.5 times fainter), being no longer among the brightest stars in the sky, what fueled speculations of its supernova time coming soon despite astronomers thinking it still has a lot of years to shine (see further down). However, from February 2020 onwards, its brightness has stabilized and it has begun to slowly recuperate the lost one, astronomers thinking the cause of said fainting being both those brightness variations as well as large amounts of circumstellar dust produced by the star eclipsing it, until Betelgeuse became again as bright as in the past some months later.
A considerable increase of brightness of Betelgeuse in 2023 had led some astronomers to think supernova time is coming soon, as the star would be on its last legs. However, the same astronomers who have proposed that also think it could still be in an earlier nuclear burning phase, thus being destined to last for much longer as also noted in the next section.
The fact that the end is nigh for Betelgeuse has attracted a considerable amount of woo around it and the effects of its death on Earth. YouTube has quite a few videos about that, including that it would have blown up in 2012,[note 2] being as bright as a second Sun, as well as other warnings of that going to explode in any moment. Other pages are no less full of bullshit, thinking Orion is far smaller than it actually is, and that Betelgeuse can be eclipsed by the Sun (it doesn't).
However, recent (2016) calculations suggest Betelgeuse still has ~100,000 years to live before going supernova, with also the possibility of it exploding not as a red supergiant but as a smaller and hotter star instead.
The Betelgeuse supernova is expected that will have a brightness comparable to that of the full Moon, even outshining it and giving for a couple of months a spectacular light show. However, it will be
mostly harmless and it's expected that neither the neutrinos, the UV/X-Ray/Gamma radiations, or its ejecta will affect Earth in severe ways from that distance, no matter what woo-meisters may say about much nastier effects — except perhaps messing with nocturnal animals that would confound the supernova with the Moon. It's also expected that it will leave behind a neutron star and not a black hole, a gamma-ray burst being also highly unlikely.
- Betelgeuse awaiting its fiery demise at the other wiki.
- Summer for those who live in the Southern hemisphere
- Yeah, right. Of course it's not justified why it's shining as usual years later[citation NOT needed]
- Red Supergiants as Potential Type IIn Supernova Progenitors: Spatially Resolved 4.6 μm CO Emission Around VY CMa and Betelgeuse
- Evolutionary Tracks for Betelgeuse
- A Systematic Change with Time in the Size of Betelgeuse
- The Continued Unprecedented Fading of Betelgeuse
- Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse
- The evolutionary stage of Betelgeuse inferred from its pulsation periods
- Supergiant FAIL
- You fail Astronomy forever (in Spanish). Go here to save you time.
- Fundamental properties of core-collapse supernova and GRB progenitors: predicting the look of massive stars before death