Why are many stars born together in one cloud?

On a clear night, look up and let your eyes rest on the stars. Some of them sit close together in a tiny sparkly bunch, like sugar sprinkled in one spot. Far away in space, new stars are being born right now.

When you spot a little bunch like that, you might wonder how those stars ended up so close. So let's wonder together: why are many stars born together in one cloud?

Every star starts inside a nebula, which means a giant cloud of gas and dust floating in space. A nebula is not like the fluffy rain cloud over your house. It is wider than anything you have ever seen.

And a nebula holds a huge amount of gas. One star needs only a small part of it. So one nebula has enough gas to make hundreds, even thousands, of stars.

Inside the nebula, every bit of gas gives a gentle pull on the gas around it. Where the gas is thicker, that pull is stronger. So the gas in those thicker spots starts to gather in closer.

A nebula has many thicker spots, not just one. Each spot pulls in the gas nearest to it, so the cloud breaks into many clumps, which means thick, bunched-up balls of gas. Picture a big bowl of cookie dough that you scoop into lots of little lumps.

Now each clump keeps pulling its own gas tighter and tighter. As the gas squeezes in, the middle of the clump grows hot. What do you think happens when a clump gets hot enough?

The clump begins to shine! Deep in its hot middle, it starts making its own light. A brand new star is born.

Remember, the nebula broke into many clumps all at once. So many clumps turn into stars at the same time, right next to each other. That is why a whole family of young stars glows together in one place.

Nebula. Clump. A giant nebula has gas for many stars, and its gas pulls into many clumps that each squeeze into a new star together.

Sleep well, little stargazer, and dream of new stars glowing side by side.