Using images from the NASA/ESA Hubble Space Telescope and ESO’s Very Large Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now. Credit: ESO, NASA & ESA
Astronomers have discovered never-before-seen structures within a dusty disc surrounding a nearby star. The fast-moving wave-like features in the disc of the star AU Microscopii are unlike anything ever observed, or even predicted, before now. The origin and nature of these features present a new mystery for astronomers to explore.
AU Microscopii, or AU Mic, is a young, nearby star surrounded by a large disc of dust. Studies of such debris discs can provide valuable clues about how planets, which form from these discs, are created. Astronomers have been searching AU Mic’s disc for any signs of clumpy or warped features, as such signs might give away the location of possible planets. And in 2014 they used the powerful high-contrast imaging capabilities of ESO’s newly installed SPHERE instrument on the Very Large Telescope for their search – and discovered something unusual.
5 wave-like arches at different distances from the star show up in the new images, reminiscent of ripples in water. They were not only able to identify the features on the earlier Hubble images – but they also discovered that they had changed over time. It turns out that these ripples are moving very fast! The arches are racing away from the star at speeds of up to about 40,000 kilometres/hour!
Such high speeds rule out conventional disc features caused by objects – like planets – disturbing material in the disc while orbiting the star. They have ruled out a series of phenomena as explanations, including collision of 2 massive and rare asteroid-like objects releasing large quantities of dust, and spiral waves triggered by instabilities in the system’s gravity.
“One explanation for the strange structure links them to the star’s flares. .. it often lets off huge and sudden bursts of energy from on or near its surface,” explains Glenn Schneider of Steward Observatory, USA. “One of these flares could perhaps have triggered something on one of the planets – if there are planets – like a violent stripping of material which could now be propagating through the disc, propelled by the flare’s force.”
The team plans to continue to observe the AU Mic system with SPHERE and other facilities, including ALMA, to try to understand what is happening. But, for now, these curious features remain an unsolved mystery. http://www.spacetelescope.org/news/heic1521/
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