Substellar Objects: Not Quite Stars, Not Quite Planets!

Have you ever seen a star twinkle in the night sky? Stars are super hot and bright because they have a special power: they can make their own energy by squishing tiny bits of stuff called hydrogen together. But some things in space are a bit too small for that!

These are called substellar objects. They are like the shy cousins of stars, not quite big enough to shine on their own. Think of them as cosmic mysteries waiting to be discovered!

Substellar objects are born in the same way as stars, from giant clouds of gas and dust floating in space. When these clouds get squeezed, they can form clumps. If a clump is big enough, it becomes a star.

If it's a little smaller, it might become a substellar object. Sometimes, they can even be like giant planets that formed on their own, far away from any star. They are like the leftovers from star birth!

The coolest thing about substellar objects is that they can't make their own energy from hydrogen like stars do. Some can briefly make energy from something called deuterium, which is like a heavier kind of hydrogen, but it runs out! After that, they just slowly cool down and shrink, like a warm cookie left on the counter.

They are also cool enough to have water vapor in their skies, just like Earth!

It's a bit of both! Substellar objects are bigger than planets like Jupiter, but smaller than our Sun. Even if they are much heavier than Jupiter, they stay about the same size, like a balloon that you keep blowing into but it doesn't get much bigger. This is because they are so squished inside! They are fascinating because they help scientists understand the difference between planets and stars.