What’s the recipe for an exoplanet? | Science News


Solar systems follow a pretty generic recipe. To begin, combine hydrogen, helium, oxygen, and carbon into a cloud of gas and dust. Sprinkle with magnesium, iron and silicon. Spin until the cloud forms a star and a planetary disk. Wait 10 million years, or until lumps form in the disk. And voila! [snap] You’ve baked a solar system. But the planets we’ve found orbiting other stars are very different from the ones in our own solar system. So, the recipes for cooking up an exoplanet are probably pretty different from those for baking an Earth. Okay, so you’ve got a star. It contains a list of all the chemical ingredients that the planet has to work with. Those proportions vary from planet to planet, and astronomers are still trying to figure out what factors produce a rocky planet versus a gassy one. Mixing matters, too. Some planetary disks are more turbulent than others. And where different elements end up in the mix determines whether or not they end up in a planet. When the planet forms also makes a big difference. Gas giants need a lot of prep time. They have to form a rocky core before they can start collecting vapors, so they start baking soon after their star forms. [ringing kitchen timer] Small, rocky planets can start later. How far a planet forms in relation to its star complicates planetary recipes. Small planets that form too close to a star can lose their atmospheres to energetic winds from the star. Sometimes big planets may arise at the system’s edges but finish cooking closer to their star later on. That’s one way to make oddballs like hot versions of Jupiter or Neptune. Scientists are studying exactly how these variables influence planet formation in other systems. And NASA’s latest planet-hunting satellite TESS could reveal clues to exotic exoplanet compositions. Meanwhile, researchers are cooking up experimental planets in the lab, to try to understand how other systems formed. [music] [snap] [snap] So one day, baking an exoplanet will be a piece of cake. [ music]