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Beta Pictoris Disk Hides Giant Elliptical Ring System

The planetary dust disk around the nearby star Beta Pictoris is dynamically "ringing like a bell," say astronomers investigating Hubble telescope images. The "clapper" is the gravitational wallop of a star that passed near Beta Pictoris some 100,000 years ago. The surprising findings show that a close encounter with a neighboring star can severely disrupt the evolution and appearance of thin disks, which are the nurseries of planetary systems. Similar fly-bys of our solar system long ago may have reshuffled the comets that now populate our Oort cloud and Kuiper belt.

1. How do the images show that Beta Pictoris was blindsided by a passing star?

Hubble astronomers carefully studied the appearance of the disk using 10 years of archival data from the Hubble telescope and from ground-based telescopes in Hawaii and Chile. Hidden within the densest part of the disk are clumps of dust that are present only on the long, thin side of the disk. (One side of the disk is 20 percent longer and thinner than the other side.) Because the disk is tilted edge-on to our line-of-sight, the astronomers inferred that the clumps might represent rings if the disk were viewed face-on. They hypothesized that these rings must be highly elliptical if they appear only on one side of the disk, and this could arise if another massive object, like a passing star, recently disturbed the entire system.