Closer look at a star turns up mysterious clumps of matter

Enlarge / Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving, wave-like features in the dusty disc around the nearby star AU Microscopii. The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011, and the bottom row VLT/SPHERE data from 2014. The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune (60 AU). The outer parts of the disc have been artificially brightened to reveal the faint structure. (credit: ESO)

A new, more detailed look at the star AU Microscopii has revealed some baffling behavior. The star was first discovered from a ground-based telescope back in the 1980s, before images from the Hubble Space Telescope showed that it was orbited by a debris disk. Some new images bring an unprecedented level of detail to the system—even more than Hubble, despite being another ground-based observation.

Previous observations of Microscopii’s debris disk, which is thought to be the remains of planet-forming material, discovered a peculiar series of variations in the intensity of the light passing through that disk. These variations were thought to be structures, clumps of stuff, all on one side of the disk as seen from Earth.

This unusual structure inspired a lot of interest in the system, as it raised suspicion that there might be planets there, perturbing the clumps. It became one of the first targets of the new SPHERE instrument on the Very Large Telescope (VLT). SPHERE specializes in high-contrast imaging, allowing the VLT to point toward a bright star and block out most of its light, revealing a more detailed view of the environment near the star.