How do stars and planets form?
You live on a planet, called Earth. Together with seven other planets, Earth circles around the Sun. As far as we know, Earth is the only planet in our solar system where life exists. Life needs a planet to live on. And life needs a star to get energy from. Without the Earth or without the Sun, you wouldn’t be here!
Long ago, most people thought that the Earth was in the center of the Universe. They also thought that the Earth was the only life-bearing place in the whole Universe. But astronomers have discovered that our Earth is just one of the eight planets in the Solar System. They found that our Sun is just one of many trillions of stars in the Universe. And we also know that at least half of all these stars has planets – maybe planets like our own.
Stars and planets are important for life. Therefore, astronomers want to understand how they form. They want to know why some stars are large and others are small. Why some are single and others live in pairs. And why some stars have just one hot, giant planet in a very small orbit, while other stars have planetary systems that are more like our own Solar System.
ALMA is the best instrument to study the formation of stars and planets. That’s because stars and planets are born in dark clouds of cold gas and dust. With a normal telescope, you can’t see what’s happening within these dark clouds. You can’t peer through the dust, so you just see a dark blob in space, like a dark wall that blocks your view.
But the cold, dark clouds emit millimeter and submillimeter waves. These waves are collected and studied by ALMA. For ALMA, the dark clouds become transparent, so it is possible to see what is going on within.
ALMA will be able to see how gas and dust clumps together because of its own gravity. It will study how these clumps break apart into smaller clumps from which stars are born. And why some of these smaller clumps are much larger than others. ALMA will be able to really witness the birth of a new star. It’s like being in a nursery and seeing how a new baby is born.
And ALMA will study the birth of planets. Planets form in disks of gas and dust that swirl around newborn stars. ALMA will witness planetary formation in progress. And by looking at the birth of other solar systems, we may also learn more about the formation of our own Earth.
Finally, ALMA can also be used to study planets, asteroids and comets in our own Solar System. Astronomers even expect that ALMA will discover many new objects!