A star nursery
What Is a Nebula?
A vast cloud of gas and dust, sometimes collapsing into brand new stars.
-
Step 1 of 5
Space between stars is not empty.
It is filled with extremely thin gas — mostly hydrogen — and fine dust. Thin, but stretched across light years it adds up to enormous mass.
-
Step 2 of 5
Sometimes the cloud clumps.
A passing shockwave, often from an exploded star, squeezes part of the cloud. Once a patch is dense enough, its own gravity takes over and keeps pulling.
-
Step 3 of 5
Squeezing gas makes it hot.
As the clump collapses it heats up, faster and faster. When the core reaches about 10 million degrees, hydrogen starts fusing and a star switches on.
-
Step 4 of 5
Some nebulae glow, some just block.
Nearby hot stars make a cloud fluoresce in reds and blues. Clouds with no star nearby show up as black silhouettes against the stars behind.
-
Step 5 of 5
Dying stars build the next ones.
When a big star explodes it flings out carbon, oxygen and iron — the stuff planets and people are made of. That enriched gas becomes the next nebula.
Every atom of iron in your blood was made inside a star that died before the Sun existed.
The short version
A nebula is a giant gas cloud — the raw material stars condense out of, and the debris they leave behind.
Try it yourself
Watch steam gather on a cold window. Scattered vapour collecting into visible drops is the same idea at a much smaller scale.
Topics