Planet Formation is Child's Play

Astronomers think they have found the two youngest solar systems ever detected, where infant planets could be sweeping up dust and creating voids in protoplanetary disks 450 light-years from Earth.

NASA's Spitzer Space Telescope observed the ring-like gaps, which could signal the earliest signs of rocky planet formation around two young stars located in the constellation Taurus—UX Tau A and LkCa 15. Both stars are about 1 million years old, which is 10 times younger than other known planet-forming systems.

"Previously, astronomers were seeing holes at the centers of protoplanetary disks," said Catherine Espaillat, an astronomer at the University of Michigan in Ann Arbor. Such holes are typically thought to be caused by photoevaporation, or stars burning dust away into light energy.

But instead of central holes, Espaillat's team saw ring-like gaps in the spinning planetary materials.

"It's more like a lane has been cleared within the disk. The existence of planets is the most probable theory that can explain this structure," she said, as the lanes are likely too distant from the star to photoevaporate.

The idea is similar to touching a dusty record as it rotates, clearing a ring in the mat of particles; planets, however, use their growing gravity to sweep up the dust.

The Dec. 1 issue of Astrophysical Journal Letters will detail Espaillat and her colleagues' findings about the infant solar systems, which they said could help explain our own planet's past.

"We are looking for our history," said University of Michigan astronomer Nuria Calvet, who worked with Espaillat on the research. "We are looking for the history of solar systems, trying to understand how they form."

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