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What is VY Canis Majoris?

Michael Anissimov
Updated May 21, 2024
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The largest known star is VY Canis Majoris, a red hypergiant measuring between 1800 to 2100 solar radii. Its volume is almost a billion times that of the Sun, though its density is much less. Canis Majoris means big dog in Latin. If it were located in the solar system, its surface would reach all the way out to the orbit of Saturn. Another way of saying this is that this star is about 9 astronomical units (AUs) wide, nine times the distance between the Earth and the Sun. There must be larger stars located in other galaxies, but we presently lack telescopes powerful enough to resolve them. Hypertelescopes may help in this regard.

VY Canis Majoris is a star in its final death throes. It is ejecting massive amounts of material into a surrounding nebula that makes the star blocked in the visible spectrum. It must be observed in the infrared portion of the spectrum. The star's death nebula is ~4500 AU in width, about fifty times larger than the star itself and much larger than our solar system. Within the gas nebula is a smaller circumstellar dust region, which has a temperature of 760 K, and a width of approximately 260 AU. The star surface probably has a temperature around 3650 K, extremely cold for a star.

Unlike main sequence stars such as our Sun, VY Canis Majoris has no distinct photosphere and thus just trails off into space. Although it is the biggest known star, it is definitely not the most massive, partly because it has already ejected so much of its mass into the surrounding nebula.

Like all red giants and hypergiants, VY Canis Majoris is so big because it has exhausted all the hydrogen fuel in its core, and has begun fusing hydrogen on a shell outside of a helium core. In fact, VY Canis Majoris is so big that it can fuse together helium, lithium, and so on, all the way up the periodic table to iron and beyond. Eventually it will have a core made mainly of iron, just like the planets. The problem with post-iron fusion reactions is that they produce no energy, and hence cannot balance out the gravitational pressure generated by the star. When all the fusion fuel runs out, the star will collapse catastrophically in a supernova explosion and become a black hole.

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Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By anon246322 — On Feb 09, 2012

The mass of VY Canis Majoris is estimated to be around 30 solar masses, so it is very unlikely that it will produce a black hole. Most likely, the remnant of this star will be either a pulsar or magnatar.

By anon164169 — On Mar 30, 2011

Where in the constellation Canis Majoris can I find VY Canis Majoris? I have read many articles about this star but no reference as to itslocation. Is it near Tau Canis Majoris? or close to Alpha? I would like to be looking up at the right location if and when the light of its supernova reaches us. Harvey M.

By anon155562 — On Feb 23, 2011

as for religion and its fakeness; Didn't someone say that it was the priest that invented the gods so that they may prey on the fears of men.

By anon154195 — On Feb 20, 2011

VY Canis Majoris, the biggest marble in space, really humbles me, and whoever made it gets to be my Almighty God. For all U.S. Presidents, PhDs, and simpletons who believe in the Almighty, no explanation is necessary. For PhDs and simpletons who do not believe in Him, no explanation is possible.

For the dead (i.e., Harry Houdini) who get to meet God Himself, no way he can come back alive to warn you guys. Even my own blood-brothers have turned their backs against God because they've always found seemingly-good-excuses to do the utter unthinkable.

I don't expect strangers here will "click" with the Almighty God anytime soon; however, Heaven's Gate will open wide for the ex-bad-guy, i.e., Saul of Tarsus who became Saint Paul. So I will never say never when some of you guys may be redeemable like Saul of Tarsus.

By anon148118 — On Jan 31, 2011

So if God didn't create this star who did? How did it come into being? Everything needs a creator even if it started with a bang. Who created whatever it was that went "boom!". God is outside the realm of time. God is infinite. What some say is the edge of the Universe, God is well beyond that. God has no beginning and no end. Infinite!

By Visionist — On Jan 15, 2011

Well all I can add is: thank you for letting me appreciate the magnificent view!

By Visionist — On Jan 15, 2011

Well all I can say is, isn't this Universe beautiful and thank you for letting me live on this little planet near our sun (Sol)!

By anon132150 — On Dec 05, 2010

"Only God can create something that big!"

I really struggle to understand how people are able to believe in God like this, please for heaven sake ( like the pun?) realize that as we humans grow more intelligent and understanding, religion in the world drops.

It's really got to be time soon for the fakeness or religion to decease. morals and goodwill are human traits -- not something to do with a god.

By buhlfarm — On Nov 09, 2010

Stuff like this wears me out but here goes anyway. If the Earth were the size of a basketball the relative size of VY Canis Majoris would be 71 miles in diameter. If the Earth were the size of a BB the relative size of VY Canis Majoris would be 0.35 miles in diameter. And we all know there will be a discovery of yet another star even bigger. There is no end.

By anon109920 — On Sep 09, 2010

I believe it is possible for supermassive stars i >25 solar masses to form elements with protons >26+ (iron or heavier) in the short time before they turn into supernovae.

This process draws energy away from the interior of star, thus starting the supernova process. 'Electron degeneracy' in the absorption of electrons by protons to make neutrons and release neutrinos, contributing to the 'pressure' which 'holds' a star up.

When 'electron degeneracy' fails, the star collapses (depending upon mass), and the resultant infalling matter, with the intersection of the energy of neutrino release, forms elements heavier than iron, which are expelled from the outer layers of the star.

By anon108461 — On Sep 02, 2010

To some extent, some of you are correct, while some are way off base. No, there is no energy gained from the fusion of elements beyond iron because it takes more energy to fuse those elements than you get out of the fusion process. But, elements beyond iron are clearly produced in the novae and super novae explosions. Our own sun was produced form such an explosion and it has been scientifically proven to contain elements beyond helium.

By anon108456 — On Sep 02, 2010

@ number 24, I can't believe you think something that beautiful and massive could have been created by accident.

By anon97869 — On Jul 21, 2010

"Only God can create something that big!"

How can you believe in such a petty little thing as God in the face of such sheer size, beauty and power? I am disappointed there are humans such as you.

By anon90650 — On Jun 17, 2010

man when it dies, is it going to become a black hole?

By anon84950 — On May 18, 2010

The article doesn't say it can't fuse elements heavier than iron, it just says that this type of fusion produces no energy to help keep the star burning.

By anon84833 — On May 17, 2010

If huge stars such as this cannot fuse elements heavier than iron than how are those elements created? The last time I checked the periodic table did not stop at 'fe'.

By anon83202 — On May 09, 2010

On the size: it says the diameter is 9 au, so the radius is 4.5 Au. It's 9 au from the sun to saturn, so this star would only reach half way. You use the radius to determine how far the surface reaches "out" from the center.

By anon76035 — On Apr 08, 2010

Did you know that Earth would be the size of a penny while canis majoris would be 1 and a half miles big? Imagine that. Also, if canis majoris was 90 inches big, Earth would be the size of a red blood cell 0.o

By anon74580 — On Apr 02, 2010

the life expectancy of vy canis majoris is about 2000 days which is about six or seven years,but it will take 5000 years for the light to reach earth. it will be no danger to earth if it goes nova or turn into a black hole. But a lot of other systems and stars will be, so we're lucky.

By anon74314 — On Apr 01, 2010

its radius is 2100 times that of the sun.

By anon68900 — On Mar 04, 2010

Does anyone know the life expectancy of Canis Majoris? I am hoping I won't be around when it turns into a black hole.

By anon68360 — On Mar 02, 2010

This star's size is but a mere speck of other stars in other galaxies. when VY turns into a black hole, we're screwed.

By anon64642 — On Feb 08, 2010

I presume that there are stars thousands of times bigger than this VY canis Majoris, but in a different galaxy.

By anon64493 — On Feb 07, 2010

how big is it?

By anon62942 — On Jan 29, 2010

Only God can create something that big!

By anon58399 — On Jan 01, 2010

My God I can't believe a star that large exists.

By anon54487 — On Nov 30, 2009

The collapse of a massive star like VY Canis Majoris begins when the core has fused enough of the lighter elements into iron, so that this mass of iron approaches about 1.44 solar masses, also known as the 'Chandrasekhar mass'.

When this occurs, there is insufficient outward fusion pressure to counterbalance the gravitational mass of the star. The 'bounce' that anon18182 describes in his post is the result of the matter collapse of a star and the release of neutrinos formed when protons and electrons are forced together to produce neutrons.

This process carries a significant proportion of the supernova's energy release, and temporarily halts the the collapse of the star. It is this combination of energy release and heating of infalling matter that provides the temperatures and pressures required to initiate the fusion of elements heavier than iron.

Some of this matter, along with the outer layers of the dying star are blown away from the core, which will collapse with several possible outcomes, depending upon the original mass of the dying star.

The result in the case of VY Canis Majoris is most likely to be a black hole.

By anon39439 — On Aug 01, 2009

What location can I find this star using google Earth?

By anon21268 — On Nov 13, 2008

If energy was produced after after the iron core what would happen?

By anon20033 — On Oct 24, 2008

Once the star starts fusing elements higher than helium it basically dies very quickly. The time between the first fusion of iron and supernova is under a day (the fusion is a product of the gravitational crush, and that gravitational force isn't enough that it can force-fuse iron). If it force-fused very slowly there is no supernova (or nova).

What's more interesting is a catalog of star masses, that is a better measure of star size.

By anon18194 — On Sep 17, 2008

Nuclear fusion at the stellar core will stop at iron; fusion of iron requires more energy than it can produce.

At this point, stellar death evolves rapidly. The massive iron core implodes, creating, in turn, an extremely energetic explosion that then collides with the inward-falling material from the star's outer layers. This is a supernova. The extreme energy produced in this shock wave allows the creation of elements heavier than iron, and also spreads them into interstellar space.

By anon18182 — On Sep 16, 2008

There is no beyond iron as far as fusion goes. For iron to fuse into a heavier element energy is required rather than produced. And that is antithetical of what a star is; a producer of energy. Once a star has an iron core that is it's death rattle. The core swiftly collapses and "bounces" to create a super nova.

By jsand77 — On Feb 01, 2008

In regards to the last paragraph where all the fusion is taking place. To my knowledge once helium is fused, oxygen and carbon atoms are released. Carbon will fuse at a lower temperature because of its position on the periodic table. But oxygen requires around 100,000 C before it can fuse. My question is am I correct so far? And, if this star does continue to fuse all the way up through iron and beyond then how hot will this star become to do so?

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology...
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