Betelgeuse is a red supergiant star around 400-700 light years from Earth, though this distance has been difficult to measure. If you find a clear night (good luck in London!) it is the deep reddish star on the top right shoulder of the constellation Orion. To find the constellation, it helps to look for the three stars in a line that make up Orion’s belt. Though this star is far away, its sheer size makes it appear very bright and prominent, with a relative luminosity of about 8000-14000 times that of our sun.
Betelgeuse is a relatively young star, being 10 million years old compared to our sun’s 5 billion. However, it has a mass of about 15 times that of our sun and, if it were placed where the sun is now, it would stretch all the way to Jupiter’s orbit nearing Saturn, engulfing all the rocky planets.
Because of this, Betelgeuse burns through its fuel much faster and it is already in its final stages of life. The star has also been classed as a semi-regular variable star, which essentially means that the brightness periodically increases and decreases and sometimes breaks its patterns. This usually happens in a 400 day cycle but, about 5 years ago, something strange happened.
In 2019, the star fell to 40% its usual brightness and, for a while, there was a theory that the star was about to go supernova in a matter of weeks. This caused a huge buzz in the astronomical community as they thought that the star was entering a pre-supernova phase. However, by 2020 the star had returned to normal, much to the shame of astronomers eager to catch a glimpse of the explosion. There was an explosion – just not the one people were expecting.
What had happened was the star had a ‘surface mass ejection’, which is pretty much exactly what is sounds like. A huge cloud of material and dust spewed from the star, obscuring its light to Earth. While these events happen on our sun all the time, Betelgeuse’s one was 400 billion times greater. While this was an interesting development, it was a little anticlimactic as ‘’the great dimming’’ that was supposed to occur did not, in fact, dim.
Scientists debate when the star will go supernova. Initial predictions placed it at some time in the next 100,000 years, but more recent research suggests that its increasing irregular brightness patterns could be a sign of fusing carbon to neon. The time frame from fusing carbon to fusing to create iron is less than a few hundred years. This puts the predictions to the near future and even tomorrow! Despite how difficult it is to track the supernovae of a star, you are sure to notice it when it does happen.
When Betelgeuse goes supernova, you will be able to look up at the night sky and see something you could describe as a second sun. A full moon has an absolute magnitude of -12.6, while the supernova is estimated to have an absolute magnitude of around -18. This means that it would by far be the brightest object in the night sky, far brighter than the moon, and it would even be visible during the day. It wouldn’t appear as a disk either, as you would expect.
Betelgeuse would contain superheated gas exploding outwards, which would make it a brilliant point of light expanding over a couple weeks. This event is amazing as Betelgeuse will be the closest supernova to Earth and the first – possibly the only – supernova seen, recorded and documented by humans. Over the next month or so it would eventually die out, leaving either a neutron star or the closest black hole to earth by over 1000 light years.
So keep your eyes to the skies – you do not want to miss this!
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