## What is the largest star? (Beginner)

What is the largest star in the universe and how many of our suns would it take to fill the largest star up? Thank you for your time.

In order to know what the largest star in the universe is we would have had to look at all the stars. We haven't come close to that - we haven't even looked at all the stars in our galaxy. There are about 100 billion stars in our galaxy, and about as many galaxies in the observable universe so you might understand why.

The best I can do is tell you what the largest known star is, but to do that I also need to know what you mean by largest. Do we pick the brightest, or the largest in volume, or the most massive (the one with the most mass)? More massive stars are generally less dense so take up a proportionally bigger volume. The most massive known is generally accepted to be the Pistol Star, which has a mass about 100-150 times that of the Sun, and is about 10 million times brighter (see this picture). About 100 Suns would provide the same amount of stuff as the star, but we would need more that 100 Suns worth of volume to fill in the space it takes up.

Thank you for your response. I was looking for the largest know star volume wise. Could you help me? Thank you again.

The Pistol Star is still very large in volume. It has a mass about 100 times the mass of the Sun and a radius of about 100 million miles (comparable to the Earth-Sun distance, or about 300 times the radius of the Sun). More massive stars are also less dense so take up proportionally more space. Red giant stars (like Betelgeuse and Antares) are also very big in volume. When our Sun becomes a red giant in about 5 billion years it will expand to enclose the inner planets. Antares has a radius about 400 times that of the Sun, so is bigger than the Pistol star in volume despite being smaller in mass.

Later: I should perhaps add that Steve Eikenberry, who used to be an Astronomer at Cornell has claimed to have found a star larger than the Pistol star. The star LBV 1806-20 might have a mass more than 200 times that of the sun and is about a million times brighter than the Sun! Check out this press release.

April 2008: this question has recently been used as an inspiration for a very nice multimedia piece from Analogik entitled Giant Stars. Follow the link to explore the difference in size from the Earth right up to giant stars like Antares mentioned above.

July 2015This list is updated regularly