Astronomers closing on a complete picture for how planets form

Newborn stars are surrounded only by a featureless disk. Debris disks persist for hundreds of millions of years. So when do planets form? And do planets form around all stars.

When we look at the planets in our Solar System, including our own planet Earth, we find that they formed nearly at the same time as the Sun: all are ~4.5 billion years old. But around newborn stars, the situation evolves rapidly: from protostars to stars with circumstellar disks to planet-rich systems with debris disks to mature planetary systems. With so much data about circumstellar and debris disks now collected, a complete picture for the formation of planets is finally starting to emerge. Here’s what the cosmic story of planet birth looks like today.

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