One of the most famous constellations in the night sky is Orion. Easily recognized by the “belt” it is also possible to notice the rest of the constellation as they are all relatively bright stars. If you look at the top left corner, you will notice a red star.
At a distance of approximately 640 light years, we can find one of the biggest and brightest orange/red stars in our night sky. It is known as alpha-Orionis, or, more famously, Betelgeuse. Located in the Orion constellation, it represents the shoulder of the hunter. Despite being so far away, it is very bright because of its incredible size.
Where to see the Star?
It is effortless to spot it in the sky from both hemispheres of the planet and, because of this, it has fascinated astronomers for millenniums, becoming one of the most studied stars by astronomers and, as a result, we know a lot about it such as its size, its composition, and its atmosphere. It is visible from almost everywhere on the globe, except for some very remote regions in Antarctica.
We are not sure where it was born as it is a single isolated star which has probably been flung out from its star cluster by the gravitational influence of some other object. It is also moving way faster than expected, and this confirms the Gravitational Slingshot Theory.
The speed at which it is moving is not the only impressive thing about this star. It is also incredibly large with a radius of 3-6 astronomical units (AU). It means that, if placed inside of our solar system it would completely cover the orbits of Mercury, Venus, Earth, Mars, and part of the asteroid belt.
Another interesting fact about Betelgeuse is that its luminosity changes over time. It is usually the 9th brightest star in our sky but, occasionally, it becomes the 7th. There are even periods where it is brighter than Rigel which is a blue supergiant and is, normally, the brightest star in the constellation. This is caused by the irregular surface of the star and by its spin. The surface of Betelgeuse is far from circular.
Betelgeuse Vs Sun
When it was born, it used to be relatively similar to our Sun in size, but it also had 10-20 times more mass. Having more fuel to burn (i.e., mass) does not mean it will live longer; in fact, it means the opposite. This is because it will reach higher temperatures in the core and burn the elements at a much higher rate.
A star like Sun can fuse hydrogen for 10 billion years but, a star with twice the mass of the Sun will stop fusing hydrogen in only 2 billion years. Betelgeuse fused the hydrogen very rapidly and subsequently started fusing helium which made it significantly grow in size and, in the future, it will burn increasingly heavier elements.
Every step takes less time than the previous one, and when Iron starts to fuse, the star will become unstable. This is because all of the other fusion reactions provide energy for the star. Iron, on the other hand, sucks up energy instead of creating it. This accelerates the shrinking, compresses the core and heats it even more. This all takes a fraction of a second and the core does not simply shrink; it collapses.
This creates an immense gravitational pull which sucks in all of the outer parts at a significant fraction of the speed of light. The whole core shrinks from being several hundreds of kilometres across to only a dozen in a few thousandths of a second. At this point, two things can happen.
The star could become a neutron star or, if the mass is larger than 20 times that of our sun, the collapse will not be stopped by anything: the star will become a black hole! Luckily for us, this is not going to happen to Betelgeuse as its mass is not large enough. This does not mean it will not be spectacular.
How much energy can Betelgeuse produce?
Moments after the collapse of the core, a monster shock wave is released in a fraction of a second. This is comparable to 100 times the energy that our Sun will produce over its entire lifetime. Stop reading for a minute and let that sink it.
100 times the energy our Sun will produce Over Its Entire Lifetime! This is an incredible amount of energy, so large, that the human brain cannot comprehend it. The material blasts out of the core creating an explosion. This is called a Supernova, and it is one of the most violent events in the universe.
The energy produced is so huge, that they can literally be seen halfway across the universe and outshine all of the stars in a galaxy. No astronomer is entirely sure when Betelgeuse will go supernova, but estimates have put it somewhere between now and the next million years which, in astronomical terms, is very soon.
We are at a safe distance away. Therefore, we do not have to worry about the explosion. We are also quite lucky to be “close” to it though because, when this happens, the star will shine incredibly bright. Brighter than a full moon. For a few weeks, it will look to us like we have two Suns. Do not worry though.
Apart from maybe not having the night time, nothing else will happen as we are at a safe distance away. A very similar event was observed by astronomers in 1006AD when ancient astronomers observed a supernova all over the world. This is currently the brightest observed stellar event in recorded history but, when Betelgeuse explodes, it is expected to be even brighter than this.
Betelgeuse has fascinated people since we first started looking up at the sky and it will continue to do so. When it goes, it will leave behind a beautiful supernova remnant which could look like the Crab Nebula which is one of the most beautiful objects in the sky. Hopefully, I will be able to see this spectacular event in my lifetime.