Planetary nebula

Layers drifting away like smoke

A red giant does not explode. Instead, the gas of its outer layers drifts slowly into space like smoke. It moves at about 20 km per second, around 500 times slower than supernova debris. The hot core left in the middle lights up the gas, and a colorful ring-shaped cloud glows.

Why?A light star is not heavy enough to squeeze its center all the way to iron. So the center never collapses all at once; the star just lets its outer layers go, little by little.

Learn moreA cloud like this is called a planetary nebula. The name only comes from how round it looked in old telescopes, like a planet; it has nothing to do with planets. After tens of thousands of years it spreads out and fades from view.

When

About 12 billion years old

Star we are watching

End of the Sun-like star

Size · state

Spreading at about 20 km per second