Scientists have discovered mysterious "ripples" in dusty disc surrounding a nearby star.
The researchers discovered the never-before-seen phenomenon using images from ESO's Very Large Telescope and the NASA/ESA Hubble Space Telescope. They also took advantage of the powerful high-contrast imaging capabilities of ESO's newly installed SPHERE, the European Southern Observatory reported. The findings were made in the atmosphere surrounding the star AU Microscopii.
Scientists have been studying AU Mic's disc and dust discs surrounding other stars in hopes of gaining insight into how planets are formed. The research team was scouring AU Mic's disc for clumping or warping that could indicate the presence of a planet when they stumbled upon the strange wave-like feature.
"Our observations have shown something unexpected," said Anthony Boccaletti, CNRS researcher at LESIA (Observatoire de Paris/CNRS/UPMC/Paris-Diderot), France, and lead author on the paper. "The images from SPHERE show a set of unexplained features in the disc which have an arch-like, or wave-like, structure, unlike anything that has ever been observed before."
Five wave-arches were observed at different distances in the new images. By looking at sets of images over time the researchers observed the ripples were rapidly changing, meaning they were moving extremely quickly.
"We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period," said team member Christian Thalmann (ETH Zürich, Switzerland). "By doing this, we found that the arches are racing away from the star at speeds of up to about 40,000 kilometers/hour!"
The waves were moving so quickly that some may have even been able to escape the gravitational attraction of the star. The ripples' incredible speed rules out the idea that they are conventional disc features caused by planets.
"Everything about this find was pretty surprising!" said co-author Carol Grady of Eureka Scientific, USA. "And 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."
The researchers are unsure of what caused the ripples, but suggested they could be linked to the collision of two massive asteroid-like objects. Another possible explanation is that the ripples are triggered by the star's flares.
"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," said co-author Glenn Schneider of Steward Observatory.
In the future, the researchers plan to continue to observe the AU Mic system with SPHERE in hopes of solving the mystery of the unusual ripples.
The findings were published in a recent edition of the journal Nature.
