Stars are immense objects. We toss around words like "big" and "huge" all the time, but what does this mean on a human scale?
After all, the Sun is a mind-crushing 1.4 million kilometers in diameter, wide enough that you could line 110 Earths side-by-side across it.
And there are stars much, much larger than the Sun.
The highest-resolution visible light image of the photosphere of the red supergiant Antares ever taken, using the Very Large Telescope. Credit: ESO/K. Ohnaka
Antares is a red supergiant, with a dozen or so times the mass of the Sun. Stars like that fuse elements in their core so rapidly that they blast out light, and it may radiate energy at a rate as much as 100,000 times as much as the Sun does. That's why, even though it's something like 500 light years away it's still one of the brightest stars in the night sky, an angry red beacon sometimes called "The Heart of the Scorpion" due to its location in the constellation of Scorpius.
When massive stars near the ends of their lives, they swell up and cool off; the spectrum of their light shifts to red, and they become supergiants. But ...