The diameter of the Sun is 1.4 million kilometers or 870,000 miles.
Did that answer your homework question? Good. But let’s take a few minutes and really put this enormous number into scale.
The Sun is so massive that it accounts for 99.8% of all the mass in the Solar System. You could fit more than 1.3 million Earths inside the Sun, and still have room to spare.
But this article is about diameter, so let’s compare the diameter of the Sun to other objects in the Solar System. The diameter of the Sun is 109 times the diameter of the Earth. It’s 9.7 times the diameter of Jupiter. Really, really big.
That’s a big Sun, but it doesn’t hold a candle to some of the largest stars in the Universe. The biggest star we know of is called Canis Majoris, and astronomers think it could be 2,100 times the size of the Sun.
Want some more info?
Diameter of the Sun in kilometers: 1,392,000 km
Diameter of the Sun in miles: 865,000 miles
Diameter of the Sun compared to Earth: 109 Earths
Here’s the article where we investigate the biggest star in the Universe, and here’s an article that compares the Sun and the Moon. How old is the Sun? 4.6 billion years.
Here are some more facts about the Sun from the physics factbook, and NASA’s Worldbook page on the Sun.
We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.