Astronomers Detect Mysterious Ripples Moving Across Planet Forming Region of AU Microscopii

Unlike anything seen during the human journey to the beginning of space and time

October 15, 2015 – 32 light-years toward the southern constellation Microscopium 

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.
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. Image credit NASA and Hubble.

Astrophysicists viewing four years of data provided by NASA’s Hubble Space Telescope and the European Southern Observatory’s (ESO) Very Large Telescope in Chile have discovered something unlike anything is ever seen before. Fast-moving, wave-like structures hidden within the dusty disk orbiting young star AU Microscopii (AU Mic), where they have been looking for clues to the processes leading to the formation of young planets.

Moving across the 40 billion-mile wide disk orbiting young star AU Microscopii at 22,000 mph, the string of ripples in the images above are moving at different speeds. Astronomers believe the features further away from AU Microscopii are moving faster than the ones closer to the star. At least, three are moving at a velocity which will result in them leaving the gravitational influence of the young star.  

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. These odd structures are unlike anything ever observed, or even predicted, before now. 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 black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically. The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU). Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.
These odd structures are unlike anything ever observed, or even predicted, before now. The top row shows a Hubble image of the AU Mic disk from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically. The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU). Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.

“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.

“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.”

Velocities reaching 22,000 miles per hour rule out the possibility of proto-planets within the dusty disk causing the gravitational disturbance detected. Calculations also indicate this phenomenon isn’t related to a collision between two massive bodies or unknown gravitational instabilities in the system of AU Mic. This team of astronomers is currently testing other theories in order to rule out other possibilities, but at this time, they’re just as mystified as the rest of us.

“One explanation for the strange structure links them to the star’s flares. AU Mic is a star with high flaring activity — it often lets off huge and sudden bursts of energy from on or near its surface,” said co-author Glenn Schneider of Steward Observatory in Phoenix, Arizona. “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 disk, propelled by the flare’s force.”

What’s next?

Astronomers now plan on additional observations of the AU Mic system using the Hubble Space Telescope, the European Southern Observatory’s (ESO) Very Large Telescope and other ground and space-based telescopes. To look for answers to the mystery surrounding fast-moving, wave-like structures hidden within the dusty disk surrounding young star AU Microscopii.

You can read more about this in the Oct. 8 edition of the British science journal Nature.

You can discover more about AU Microscopii and the Hubble Space Telescope here.

Journey across the cosmos with the European Southern Observatory’s Very Large Telescope here.

You can learn about NASA’s mandate to travel to the stars here.

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