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Betelgeuse - the next supernova

If you look up at the night sky reasonably far away from a city, then chances are that you can see the Orion constellation.

This constellation is probably one of the, if not the most commonly known constellation, and it can easily be identified by looking for 3 stars close to one another that join up to make a short line.

Just above those 3 stars, is the shoulder of Orion, and this star goes by the name of "Betelgeuse".

Betelgeuse - Image credit: NASA



Betelgeuse is a massive star, coming in at over 10 times the mass of our own star, the Sun.

Not only is this star massive, but it's also huge in volume.

In fact, if Betelgeuse were to replace the Sun, it's surface would extend past Mars.... and you can see this beast with your own eyes (and of course clear skies!).

This star is also incredibly luminous which is what makes it easy to make out in the night sky, but what differentiates it the most from even its fellow bright stars such as Vega, Sirius and Rigel, is that it shines a deep reddish colour that easily stands out from the more common white light of neighbouring stars.

Try not to get it confused with Mars though if you're at that time of year!

So the obvious question is - how come it's red?

Billions of years old

Betelgeuse is far from young, and is in fact nearing the end of its life as we speak.

This star has evolved past the main sequence stage, which is what the Sun is currently in, and has become a "super red giant".

If you're not that familiar with the life cycle of a star, and would be interested in knowing more about it, then I'd definitely recommend checking out one of my other posts here, but simply put, Betelgeuse is running out of fuel to burn and it's doing anything to stay alive.

Betelgeuse could go boom any second now, and the spectacle that we would witness from Earth would be like no other....

Fortunately, while Betelgeuse is considered "close-by" in astronomical terms, the fact that it is still 540 light years away means that astronomers believe that it will not present any kind of threat to Earth when it does eventually go supernova.

When Betelgeuse does say its last words though, it will compress down to the size of a planet before imploding outward under the extreme pressure, releasing itself into the cosmos as a burst of the periodic table - the same elements that make up you and I!

Gas, dust and most abundantly extremely intense radiation would scatter throughout space.

When Betelgeuse goes supernova, it will release more radiation that it would've done over it's entire lifetime, and if we're caught in the middle of it, life on Earth would almost certainly be a thing of the past, as our atmosphere would be stripped away from the radiation, our oceans would boil into space, and even after all of that, if we did happen to survive, we would be dealing with the largest epidemic of radiation poising that we could've ever imagined.

Fortunately though, we're not that close.

However, we are close enough to receive a portion of that radiation - enough to be able to witness one of the most spectacular events in the whole of the universe (the part that we've observed, at least!)

A supernova.


A supernova is just what I described earlier - the process of a star imploding under the extreme pressure that comes from the collapse of a massive enough star.

Not all stars can go supernova though and in fact, the Sun is one of them.

To be able to produce a supernova at "death", stars need to have enough mass....

Stars rely on the intense radiation produced from fusing two atoms together to keep themselves up, and when they run out of this fuel, they collapse under their own gravity.

However, there needs to be enough mass-energy present for the pressure to become high enough for the star to explode as a supernova.

The Sun simply doesn't cut the mustard when it comes to mass.

Betelgeuse, however, most certainly does.

It's currently understood that a star needs to be at least 8 solar masses (1 solar mass = mass of the Sun), and astronomers believe that Betelgeuse is approximately 10 solar masses.

I mentioned earlier that Betelgeuse wasn't a young star, and while it definitely still isn't "young", it probably gave the misimpression that Betelgeuse is an extremely old star, which isn't really the case...

The bigger a star, the shorter it lives.

Tempting fate

Stars need to burn fuel in the form of hydrogen at their core to release enough energy to withstand their own gravity that's trying to collapse them.

Take the Sun for example.

Even though it might not look this way from Earth, the Sun is under a constant turmoil of two opposing forces...

Gravity is trying to collapse the star, and nuclear fusion at the core is releasing energy that's trying to expand the star.

The almost equilibrium of the two is what a star experiences for the longest part of their life, and it's known as the "main sequence stage", which I mentioned earlier.

For a star like the Sun, which is itself in the main sequence stage, it can stay like this for several billions of years, perhaps even longer, but for a star like Betelgeuse?

Not quite the same story....

The more massive the star, the stronger its gravity.

This increase in gravitational strength can only be combatted by one thing - an increased rate of nuclear fusion, which is the process of burning its fuel to stay alive.

Therefore, with an increased rate of nuclear fusion, the quicker it runs out of fuel and the shorter its lifespan. However, there's a bit of a domino effect to this....

Nuclear fusion is dependant on two things:

  • Pressure and;

  • Temperature.

The process of nuclear fusion releases an incredible amount of energy which is what keeps the star from collapsing, but this energy also increases the temperature at the core where nuclear fusion happens.

With an increase in temperature, the rate of nuclear fusion also increases, as more hydrogen atoms have sufficient energy to do fuse with each other.

I talk all about the process of nuclear fusion in the same article that I mentioned earlier - about the life-cycle of a star, which you can also visit here.

Mass vs Volume

That's exactly why massive stars don't live very long, at least not in comparison to relatively small stars, in terms of mass, like the Sun.

Quick piece of advice - don't get mass confused with volume, as they're two completely different things.

Some objects in the universe, such as black holes, neutron stars and white dwarfs (which is what we think the Sun will eventually become) are, relatively speaking, very small in volume but incredibly massive objects.

Mass refers to how much matter there is in an object, where as volume refers to the overall size of the object, and the amount of mass per volume is the density of that object.

I mentioned earlier that when Betelgeuse does go supernova, we would experience a "spectacle" from Earth, but what exactly did I mean by that?

What kind of spectacle?

Global firework display

Because Betelgeuse is only 540 light years away, we would receive a large amount of radiation from a supernova produced by it.

This radiation would comprise of several wavelengths of light, most of which we won't be able to see, such as infrared (heat) and radio, but some we would - visible light.

Fortunately though, the intensity of the radiation would be too low to cause any harm to life on Earth.

Our skies would be illuminated by this light for potentially weeks and even months!

Betelgeuse appears so bright in the night sky already, mostly because it's luminosity is over 125,000 times that of the Sun (although we don't receive anywhere near as much of that light as we do from the Sun, obviously!)

But the amount of light that would reach us from a supernova explosion would be incredible.

Some people estimate that Betelgeuse would become brighter than a full moon, and you'd even be able to see it in broad daylight!

What an amazing experience that would be - to observe a supernova with our own eyes.

From the supernova of a star that's been in our backyard forever....

The amazing thing about all this is that it could happen literally any second.

In fact, because the light emitted from Betelgeuse takes 540 years to reach us (hence why it's 540 light years away), Betelgeuse might have already gone supernova, and we're just waiting to receive the light from it!

So remember that the next time you look up at the shoulder of Orion - that star could seem to explode right in front of your own eyes.

I mean it would just be an experience like no other, for astronomers and everyone else alike; we've not been able to observe a supernova even in our own galaxy for 400 years, never mind a supernova from only 540 light years away!

Astronomers continue to observe Betelgeuse for tail-tail signs of a supernova, such as an influx of neutrinos, but that's a whole other story...

It's not an easy job though, as Betelgeuse belches dust from its surface that makes the luminosity of the star seem to fluctuate in cycles, as the dust partially blocks the light from getting to us.

Whether you and I will ever get to witness Betelgeuse going supernova is another question though, as it could happen at any point in time in the next millions of years! So not great odds....

But who knows!

Hopefully that was an interesting read!

As always, feel free to contact us if you have any questions and consider singing up to receive daily facts about our universe.

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