You might have heard that Betelgeuse, pronounced beetle-juice, has been in the news lately. That’s because this well-known star, part of the Orion constellation – which we mention in the ‘The Sky at Night’ magazine in our Planetarium Tinkerer box – has been going through some significant changes lately.


Betelgeuse is Dimming

Since the beginning of December 2019, Betelgeuse’s brightness has dropped by a third (34% to be precise), making it fall from the 9th brightest star in the night sky to the 23rd brightest. Something truly colossal is happening. To get a feel for the scale of the changes taking place within Betelgeuse, you have to know that it is one of the biggest stars you can see in the night sky, at approximately 900 times the size of our sun. As another comparison, it is so monstrous that if you replaced our Sun by Betelgeuse, it would engulf all four inner planets; Mercury, Venus, Earth and Mars, and nearly reach Jupiter as well.

Source: ESO

Thanks to its size, Betelgeuse is the only star other than our own whose surface we can directly picture in detail, despite being 640 light-years away!


So, what is really going on with Betelgeuse? 

In addition to being a supergiant red star, it is also a type of star called a variable star, which goes through cycles of increasing and decreasing brightness due to changes in its size and temperatures. These changes occur because internal forces within the star such as gravity and the energy released by the burning of its core (fusion power), constantly fight to balance each other out. Sometimes gravity takes the upper hand and squeezes the star, and sometimes the core releases a lot of energy, making the star expand once again.

Thanks to centuries of observations, we know that Betelgeuse goes through brightness cycles, some lasting 420 days superimposed on longer cycles of 5-6 years, in addition to a smaller one that is around half a year. What is unique though about the current dimming is that it has dropped to levels not seen for over 125 years, and done so in a matter of a few weeks. Needless to say, astronomers all over the world are excited!


Is Betelgeuse going to explode?

The significant drop in brightness might be just a lesser-known phenomenon linked to the variability cycles that we haven’t encountered yet.

But another, more exciting possibility, exists. Betelgeuse might be coming to the end of its life and finish off in a spectacular way, in a supernova. This is when massive stars explode and unleash tremendous amounts of material and energy into space. Don’t worry, though, Betelgeuse is very far away from us so we will not feel a thing. If it goes bang, it will become very bright and outshine for a few weeks everything in the sky at night as well as during the day. What will be left after that will most likely be a neutron star or a black hole, a place where gravity collapses on itself and where not even light can escape.

Crab Nebula (also known as Messier 1) is the remnant of a supernova explosion observed almost 1,000 years ago, in the year 1054. It contains a neutron star near its centre that spins 30 times per second around its axis. Source : ESO

Can I see Betelgeuse in the night sky?

Yes! What is really cool is that you can see Betelgeuse’s change in brightness by yourself. No telescope is required. Simply go out in a place where there is low light pollution and find the Orion constellation – using our star wheel provided in our Planetarium box – which is observable during the first half of the night well into February. Compare Betelgeuse to other stars of different brightness to determine how bright it is. Check it out in the coming weeks and see if it has dropped in brightness. The image below gives several other stars in Orion that can be used for comparison.



So, will Betelgeuse explode anytime soon? No one knows. It might blow tonight, or it might explode in the next 10,000 years. The best thing to do is to watch the sky and see what happens.


Written by,

Tinkerer’s Science Team



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