Mysterious Ripples Found Racing Through Planet-forming Disk

[n2doc]

This set of images of a 40 billion-mile diameter edge-on disk encircling the young star AU Microscopii reveals a string of mysterious wave-like features. Astronomers discovered the ripples are moving across the disk at speed of 22,000 miles per hour. The cause of the phenomenon is unknown and never-before seen in stellar gas and dust disks.
Credits: NASA, ESA, ESO, A. Boccaletti (Paris Observatory)


AU Mic is located 32 light-years away in the southern constellation Microscopium. It is an optimal star to observe because its circumstellar disk is tilted edge-on to our view from Earth. This allow for certain details in the disk to be better seen. Astronomers have been searching AU Mic’s disk for any signs of clumpy or warped features that might offer evidence for planet formation. They discovered a very unusual feature near the star by using ESO’s SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument, mounted on the Very Large Telescope.

“The images from SPHERE show a set of unexplained features in the disk, which have an arc-like, or wave-like structure unlike anything that has ever been observed before,” said Anthony Boccaletti of the Paris Observatory, the paper’s lead author.

The images reveal a train of wave-like arches, resembling ripples in water. After spotting the features in the SPHERE data the team turned to earlier Hubble images of the disk, taken in 2010 and 2011. These features were not recognized in the initial Hubble observations. But once astronomers reprocessed the Hubble images they not only identified the features but realized that they had changed over time. The researchers report that these ripples are moving — and they are moving very fast.

“We ended up with enough information to track the movement of these strange features over a four-year period,” explained team member Christian Thalmann of the Swiss Federal Institute of Technology in Zurich, Switzerland. “By doing this, we found that the arches are racing away from the star at speeds of up to 10 kilometers per second (22,000 miles per hour)! Co-investigator Carol Grady of Eureka Scientific in Oakland, California, added, “Because nothing like this has been observed or predicted in theory we can only hypothesize when it comes to what we are seeing and how it came about.”

more
http://www.nasa.gov/feature/goddard/mysterious-ripples-found-racing-through-planet-forming-disk

[leveymg]

1. Large asteroids, perhaps?

[mhatrw]

2. as the star forms, it forcibly expels clumps of heavier elements. n/t