In October 2015, astronomers working with NASA's Hubble Space Telescope and the European Southern Observatory's (ESO) Very Large Telescope located in Chile discovered never-before-seen features inside the dusty disk surrounding the young, close by star AU Microscopii (AU Mic).They discovered fast-moving, wave-like structures, which are unlike anything ever observed before, or even anticipated in a circumstellar disk. This recent, mysterious occurrence may deliver valuable hints about how planets are made inside these star-surrounding disks.
AU Microscopii is situated 32 light-years away in the southern constellation Microscopium. It is sort of an ideal star to observe because its circumstellar disk is tilted edge-on to our sight from Planet Earth. This allow for some details in the disk to be better observed. Astronomers have been probing AU Mic's disk for any signs of bulky or warped features that can deliver indication for planet formation. Instead, they discovered a very rare feature close the star by using ESO's SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) tool, mounted on the Very Large Telescope.
The images (below) disclose a sequence of wave-like arches, like ripples in water. After noticing the features in the SPHERE data the astronomers turned to previous Hubble imageries of the disk, captured in 2010 and 2011. These features were not documented in the early Hubble observations.
But once astronomers re-vised the Hubble pictures they not only recognized the features but also grasped that they had changed over time. The astronomers report that these ripples are actually moving -- and they are moving rapidly.
The ripples farther away from the star appear to be stirring faster than those nearer to it. However, three of the ripples are moving so rapid that they are actually escaping from the gravitational attraction of the star. Such high speeds exclude the likelihood that these ripples are produced by objects, like planets, gravitationally distressing material in the disk.
Astronomers has also ruled out a series of phenomena as clarifications, counting the collision of two massive and uncommon asteroid-like objects discharging large amounts of dust and spiral waves caused by uncertainties in the system's gravity.
Astronomers decide to carry on to observe the AU Mic system to try to comprehend what is really happening. But, for the time being, these questioning features remain an unexplained mystery.