The biggest stars in the universe, compared to the Sun
The Sun is 109 times wider than Earth — yet it is an ordinary, middle-sized star. Some red supergiants are so large that, placed where the Sun is, they would swallow Jupiter’s orbit.
Why nobody agrees on the biggest star
The largest stars are cool, puffy red supergiants whose outer layers fade gradually into space — there is no sharp edge to measure. Their size also depends on their distance, which is hard to pin down. UY Scuti was long quoted at about 1,700 solar radii; newer distance measurements from the Gaia space telescope shrank it to around 900. The current record-holder, Stephenson 2-18, carries similarly large error bars.
Big isn’t heavy
The most massive known star, R136a1, is “only” about 40 times wider than the Sun but around 200 times heavier. Red supergiants are the opposite: enormous but thin — their outer layers are less dense than the air you breathe.
See the Sun, planets and stars to scale →