Just how big is VY Canis Majoris and how does its size compare to that of the Sun and planet Earth?

By Colin Stuart

Published: Friday, 14 April 2023 at 12:00 am

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The celestial beasts known as hypergiant stars are truly colossal in size.

The biggest hypergiants would be able to squeeze 10 billion of our Suns inside, or 14 quadrillion Earths.

Truly, the staggering size of these largest of stars is hard to comprehend.

To really understand just how big these stars are, we’ve taken a look at one of the most famous hypergiant stars, VY Canis Majoris, which is one the biggest stars in the Universe.

Discover more mind-blowing science in our guides to the biggest objects in the Universe and the weirdest stars in the Universe.

VY Canis Majoris is a red hypergiant that can be seen in the constellation of Canis Major, the Great Dog.

You could fit at least 1,420 Suns across the face of VY Canis Majoris, making its total diameter close to 2 billion kilometres.

Some estimates put it at over 2,000 Suns across, or almost 3 billion kilometres wide.

Earth orbits a mere 150 million kilometres from the Sun, meaning VY Canis Majoris is at least 13 times wider than the Earth–Sun distance.

It would take almost 3 billion Suns to fill up VY Canis Majoris.

Even Mercury, the smallest planet, can only fit inside the Sun 21 million times. A supergiant star like Betelgeuse would fit inside hypergiant VY Canis Majoris 8 times over.

Despite travelling at around 300,000 kilometres per second, it would take a beam of light 6 hours to travel around the circumference of VY Canis Majoris.

That’s about the same amount of time it took for photos of Kuiper Belt Object Arrokoth to travel back to Earth from NASA’s New Horizons probe.

This guide originally appeared in the May 2023 issue of BBC Sky at Night Magazine.

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