Where are the Largest Stars in the Sky?

Stars are immense balls of burning plasma that are held together by their own gravity. The star that we are most familiar with is our Sun. However, compared to many of the other stars in the universe, its not the biggest nor the smalles. Technically, it's called a yellow dwarf, big enough to dwarf all the planets, but not even medium-sized by the standards of all stars. There are many stars much more massive and larger than the Sun. Many stars in our galaxy are much more massive and extensive than the Sun. Some are larger because they've evolved that way from the time they were formed. Others are larger because they are getting older and expanding as they do.  

Let's take a look at the 10 largest (by diameter) stars astronomers have explored.

A few caveats: First, this is only a sampling of known giant stars. There could be larger ones out there. Second, some of these stars are variable, meaning that they regularly expand and shrink as their brightness changes. And lastly, there is, like virtually all astronomy measurements, an inherent bit of error.  

Edited and revised by Carolyn Collins Petersen.

01
of 10

VY Canis Majoris

Bright star surrounded by clusters of smaller stars
Tim Brown/ The Image Bank/ Getty Images

This red hypergiant is among the largest known stars in our galaxy. It has an estimated radius between 1,800 and 2,100 times the radius of the Sun. At this size it would reach nearly to the orbit of Saturn if placed in our solar system. VY Canis Majoris is located roughly 3,900 light-years from Earth in the direction of the constellation Canis Majoris.

02
of 10

VV Cephei A

Our Sun compared to the giant star VV Cephei A.
Our Sun compared to the giant star VV Cephei A. Foobaz/Wikimedia Commons

Also located in the direction of the constellation Cepheus, about 6,000 light-years from Earth, this red hypergiant star is estimated to be around a thousand times the radius of the Sun. It's actually part of a binary star system; its companion is a smaller blue star. The two orbit each other in a complex dance. No planets have been detected at this star. 

03
of 10

Mu Cephei

Mu Cephei
Artist's conception of what Mu Cephei might look like. Wikimedia Commons

This red supergiant in Cepheus is about 1,650 times the radius of our Sun. It is also one of the brightest stars in the Milky Way galaxy, with more than 38,000 times the Sun's luminosity.

04
of 10

V838 Monocerotis

V838 Monocerotis in its outburst mode, as seen by Hubble Space Telescope.
V838 Monocerotis in its outburst mode, as seen by Hubble Space Telescope. NASA and STScI

This red variable star located in the direction of the constellation Monoceros, is about 20,000 light-years from Earth. It may be larger than either Mu Cephei or VV Cephei A, but because of its distance from the Sun its actual size is difficult to determine. Also, it pulsates in size, and after its last outburst in 2009, its apparent size was smaller. Therefore a range is typically given of between 380 and 1,970 solar radii. 

The Hubble Space Telescope has observed this star several times, documenting the shroud of dust that is moving away from it.

05
of 10

WOH G64

WOH G64
An artist's conception of what WOH G64 and its debris disk might look like. European Southern Obervatory.

This red hypergiant located in the constellation Dorado (in the southern hemisphere skies) is about 1,540 times the radius of the Sun. It is actually located outside of the Milky Way Galaxy in the Large Magellanic Cloud. It's a nearby companion galaxy to our own and lies about 170,000 light-years away. 

06
of 10

V354 Cephei

WOH G64
An artist's conception of what WOH G64 and its debris disk might look like. European Southern Obervatory.

Slightly smaller than WOH G64, this red hypergiant is 1,520 solar radii. At a relatively close 9,000 light-years from Earth, V354 Cephei is located in the constellation Cepheus. 

07
of 10

KY Cygni

KY Cygni is at least 1,420 times the radius of the Sun, but some estimates make it more like 2,850 solar radii. It's likely closer to the smaller size. It is located about 5,000 light-years from Earth in the constellation Cygnus. There is not a good image available for this star at this time.

08
of 10

KW Sagittarii

Representing the constellation Sagittarius, this red supergiant is no slouch at 1,460 times the radius of our Sun. It lies about 7,800 light-years away from us. There is not a good image available for this star at this time.

09
of 10

RW Cephei

RW Cephei
A view of RW Cephei (upper right) from the Sloan Digital Sky Survey. SSDS

Here's another entry from the constellation Cepheus, in the northern hemisphere sky. This star may not seem all that large in its own neighborhood, but there aren't many others in our galaxy or nearby that can rival it. This red supergiant's radius is somewhere around 1,600 solar radii. If it were in place of our Sun, its outer atmosphere would stretch beyond the orbit of Jupiter.

10
of 10
Betelgeuse as seen by Hubble Space Telescope.
Image Credit: NASA, ESA

Our final entry, and the last star known to have a radius in excess of  thousand times that of our Sun, is Betelgeuse. It's the most well-known of the red supergiants. This is partially due to the fact that at roughly 640 light-years from Earth, Betelgeuse is very close compared to the other stars on this list. Also, it lies in perhaps the most famous of all the constellations, Orion. This massive star is somewhere between 950 and 1,200 solar radii and is expected to go supernova any time. More »

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Your Citation
Millis, John P., Ph.D. "Where are the Largest Stars in the Sky?" ThoughtCo, Jun. 23, 2017, thoughtco.com/the-largest-star-in-the-universe-3073629. Millis, John P., Ph.D. (2017, June 23). Where are the Largest Stars in the Sky? Retrieved from https://www.thoughtco.com/the-largest-star-in-the-universe-3073629 Millis, John P., Ph.D. "Where are the Largest Stars in the Sky?" ThoughtCo. https://www.thoughtco.com/the-largest-star-in-the-universe-3073629 (accessed January 20, 2018).