Protoplanetary Disk Gaps may NOT Indicate Exoplanets

When astronomers study protoplanetary disks of gas and dust that surround young stars, they sometimes spot a dark gap like the Cassini division in Saturn's rings. It has been suggested that any gap must be caused by an unseen planet that formed in the disk and carved out material from its surroundings. However, new research shows that a gap could be a sort of cosmic illusion and not the sign of a hidden planet after all.

"If we don't see light scattered from the disk, it doesn't necessarily mean that nothing is there," says lead author Til Birnstiel (Max Planck Institute for Astronomy), who conducted the research while at the Harvard-Smithsonian Center for Astrophysics (CfA).

The researchers studied disks that shine in visible or near-infrared wavelengths due to scattered, or reflected, light. (In contrast, radio or millimeter telescopes pick up emission directly from the disk itself.)

Scattered light comes from starlight that bounces off tiny particles about the size of cigarette smoke. Those particles initially suffuse the protoplanetary disk, but undergo changes over time.

link.