How Planets Are Born

  • Released Thursday, June 16, 2016
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Planets emerge from the dense disk of gas and dust encircling young stars.

Planets emerge from the dense disk of gas and dust encircling young stars.

Scientists think planets, including the ones in our solar system, likely start off as grains of dust smaller than the width of a human hair. They emerge from the giant, donut-shaped disk of gas and dust that circles young stars. Gravity and other forces cause material within the disk to collide. If the collision is gentle enough, the material fuses, growing like rolling snowballs. Over time, dust particles combine to form pebbles, which evolve into mile-sized rocks. As these planetesimals orbit their star, they clear material from their path, leaving tracks of space empty but for fine dust. At the same time, the star gobbles up nearby gas and pushes more distant material farther away. After billions of years, the disk will have totally transformed, much of it now in the form of new worlds. Watch the video to see this process unfold.

This animation shows how material around a young star is shaped into planets over billions of years.

Planet formation begins with a brilliant young star at the center of what’s called a protoplanetary disk, shown above.

Planet formation begins with a brilliant young star at the center of what’s called a protoplanetary disk, shown above.

Collisions within the disk form rocks that act as planetary building blocks. They settle into orbit around the star, creating gaps in the disk.

Collisions within the disk form rocks that act as planetary building blocks. They settle into orbit around the star, creating gaps in the disk.

Over time, these developing worlds consume much of the disk’s gas and dust. A faint outer ring of leftover debris is typically all that remains.

Over time, these developing worlds consume much of the disk’s gas and dust. A faint outer ring of leftover debris is typically all that remains.

Credits

Please give credit for this item to:
NASA's Goddard Space Flight Center
Video and images courtesy of NASA/JPL-Caltech

This page was originally published on Thursday, June 16, 2016.
This page was last updated on Wednesday, May 3, 2023 at 1:48 PM EDT.