What is the Biggest Star in the Universe?

In this short explainer video, Universe Today's publisher Fraser Cain researches what is the biggest star in the Universe, as well as the most massive star, and explores the limits that stars can reach.

Based on this article in Universe Today

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My name is Fraser Cain, I'm the publisher of Universe Today.

My daughter is a question asking machine, and she hit me with this puzzler when she was just 6 years old:

What is the biggest star in the Universe?

My answer was that the Universe is a big place, and we can't possibly know what the biggest star is.

But that's not a real answer.

So I did some research to learn what is the biggest star is - that we know of - and just how big could a star get... theoretically.

Let's consider our own Sun for a sense of scale.

The Sun measures 700,000 km from the center to its surface.

This distance is known as a solar radius.

The mass of the Sun is two times ten to the power of thirty (pause) kilograms, and this is what we call "one solar mass".

We use a solar mass and a solar radius to give us relative terms to describe the size of other stars in our Universe.

This makes it much easier for us to wrap our heads around just how incomprehensibly gigantic these things are.

When we think of "big" stars, there are both massive stars, and large stars.

Astronomers theorized that the most massive star you could possibly have is 150 solar masses, or 150 times the mass of our Sun, and they would only have existed in the early Universe, when stars were made of pure hydrogen and helium and trace metals leftover from the Big Bang.

The most massive star we currently know of is R136-a1. This star is located in the large Magellanic Cloud's Tarantula Nebula, 165,000 light years from Earth.

Here's the best part... this star is more than 265 solar masses, breaking the original theoretical limit.

What's going on? Scientists believe it was likely created when several supermassive stars merged together.

They predict that R136a1 is soon nearing the end of its life. And when it does, it will become a hypernova, one of the most powerful explosions in the Universe, and collapse into a black hole.

Another massive star, located closer to Earth is Eta Carinae, only 7,500 light-years away.

The radius of Eta Carinae is about 250 times the size of the Sun, and it contains about 120 solar masses.

It produces a million times as much energy as the Sun and it's expected to explode as a supernova any day now.

But there are much much bigger stars out there - less massive, but bigger.

Betelguese in Orion, is a red supergiant star, nearing the end of its life. It has a radius of 950 to 1,200 times the size of the Sun.

If there was someway to magically summon Betelguese to the centre of our Solar System, all of the inner planets - as well as Jupiter - would be orbiting inside it.

There's some controversy, but the biggest known star is VY Canis Majoris, a monster located almost 3,900 light-years away.

Good thing it's so far away, because it's huge.

It measures 1,300 to 1,540 times wider than the Sun, and if it was located in the Solar System, it would engulf the orbit of Saturn.

We can't see and measure every star in the Universe, so what's the biggest possible star?

According to Roberta Humphreys from the University of Minnesota, the researcher who calculated the size of VY Canis Majoris, the largest possible star is about 2,600 times the size of the Sun.

Stars that big are out there, somewhere...

[frasercain]

Great suggestion, it would be cool to link to all the sources I'm using.

[MrIasson]

Your videos are amazing. Thank you very much for the big effort. keep it going.

[frasercain]

We talked a bit about this in Astronomy Cast 303: Equilibrium. Once a star has too much gravity, and even the neutrons can't hold up against it, there's nothing to keep it in balance and it becomes a singularity. There might be some exotic stages within the black hole (breakdown of quarks, etc), but we can't observe it beyond the event horizon.

[frasercain]

Yeah, but it's a variable star. That's why I mentioned that there's some controversy.

[littlejoe]

trading in your hair remnants for that walter white goatee was definitely the way to go

[demonlink]

Thank you for this video, I was wondering about this question when I was small

[NoMoreForeignWars]

Your speed delivery has improved vastly compared to this old video.

[TheJlook]

these videos are a great idea . if you could post a link giving us all the facts that flash upon the screen - that'll be great

[crazykailash]

Good one Fraser thanks
Keep posting short n sweet videos.
It'll increase subs.
Been listening to astronomy cast for about an year now :)

[agp]

Cant help but wonder what is the surface temperature of vy canis

[taskik]

Can you give me an exact date when did it broke the record?

[frasercain]

Or Westerlund? Which apparently is tearing itself apart.

[camm]

Side note, the larger a star is, usually the less dense it is. So while VY Canis is very large without a doubt, it's not as dense as some of it's small star counterparts like Betelgeuse or an Antares Red Supergiant

[julianpasco]

just had to look twice to see why you look different here!! hehehe

thanks for the content you and Pamela create xD

[frasercain]

If the Sun did explode, it would certainly be visible during the daytime. :-)

[Uhmu]

Didn't almost recognize you without the headphones from the podcast. Great video though.

[TheCaptainKeyes]

So, what you forgot to mention is that observation of the stars isn't in real-time, it is limited by the speed of light. So, assuming that it takes light one year to travel one lightyear, then that star you said is 3, 900 lightyears away, we are seeing that many years in the past. so, when you say a star is due to explode "any day now, " what you mean is that it could very well have exploded two thousand years ago, or yesterday, and we are just waiting for the DVR to finish recording the movie so we can play it back. :)

[erwin]

Hey Fraser! I've got a Q&A: whenever I see probes and Tesla's being sent into space, I've always get this sense that we just sent parts of our earth into space. So my question is: how many probes can we sent into space before we run out of the necessary resources?

[odinfaaborg]

Have you planned an explainer about that? how small a star can be. :-)

[frasercain]

The biggest star is going to be constantly changing. Maybe I'll keep putting in new annotations.