Mysterious ripples spotted racing through planet-forming disk: Wave-like arches near star are 'unlike anything ever seen before'

  • The fast-moving structures were spotted in a disk near star AU Microscopii
  • AU Microscopii, known as AU Mic, is located 32 light-years from Earth 
  • Images show structures as wave-like arches, resembling ripples in water
  • Astronomers said they are 'unlike anything ever been observed before' 

By Victoria Woollaston for MailOnline

Published: 06:36 EST, 9 October 2015 | Updated: 09:28 EST, 9 October 2015

Astronomers studying the debris disk of a nearby star have uncovered a series of fast-moving structures that have left them baffled.

The wave-like arches resemble ripples in water and are racing through the circumstellar disk around the star AU Microscopii (AU Mic).

The experts don't currently know what is causing the phenomenon but they hope it will provide valuable clues about how planets form inside these star-surrounding disks.

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Astronomers studying the debris disk of a nearby star have uncovered a series of fast-moving structures which have left them baffled. The wave-like arches (pictured) resemble ripples in water and are racing through the circumstellar disk around the star AU Microscopii (AU Mic) at 22,000 miles per hour (10km per second)

Astronomers studying the debris disk of a nearby star have uncovered a series of fast-moving structures which have left them baffled. The wave-like arches (pictured) resemble ripples in water and are racing through the circumstellar disk around the star AU Microscopii (AU Mic) at 22,000 miles per hour (10km per second)

Young planetary systems typically contain rings of debris known as protoplanetary disks. 

This debris ultimately joins together to form planets and it is thought our solar system was formed in this way.

The ripples were spotted while astronomers from the Paris Observatory and the Swiss Federal Institute of Technology were searching for signs of clumpy or warped features in AU Mic's disk.

Such features would provide clues to the formation of planets and how young planetary systems behave. 

THE RIPPLES AROUND AU MIC 

AU Mic is located 32 light-years away in the southern constellation Microscopium. 

It is a useful star to observe because its circumstellar disk is tilted edge-on to our view from Earth.

This makes certain details in the disk more visible.

According to the research, the ripples farther away from the star seem to be moving faster than those closer to it.

At least three of the features are moving so fast that they are escaping from the gravitational attraction of the star. 

Such high speeds rule out the possibility these features are caused by objects, such as planets, gravitationally disturbing material in the disk.

The team has also ruled out the theory that the waves were caused by the collision of two massive and rare asteroid-like objects releasing large quantities of dust.

Instead they believe the ripples are linked with the star's flares but admit they can't confirm this yet. 

In images captured by the European Southern Observatory's (Eso) Spectro-Polarimetric High-contrast Exoplanet Research (Sphere) instrument, mounted on the Very Large Telescope, they noticed a set of unexplained features.

These features looked like waves and ripples, but it wasn't until the same images were reprocessed using Nasa's Hubble telescope that the researchers could see how they were moving. 

The Hubble images, taken in 2010 and 2011, not only revealed a train of wave-like arches, they also helped the astronomers to see that they had changed over time as they moved 'very fast' through the disk. 

'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 22,000 miles per hour (10km per second).'

The researchers added that 'nothing like this has been observed or predicted' and they can only guess at what they are seeing. 

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. 

AU Mic (illustrated) is located 32 light-years away in the southern constellation Microscopium. It is a useful star to observe because its circumstellar disk is tilted edge-on to our view from Earth. This makes certain details in the disk more visible

AU Mic (illustrated) is located 32 light-years away in the southern constellation Microscopium. It is a useful star to observe because its circumstellar disk is tilted edge-on to our view from Earth. This makes certain details in the disk more visible

The ripples (pictured) farther away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast they are escaping from the gravitational attraction of the star. Their high speeds rule out the possibility they are caused by planets gravitationally disturbing material in the disk

The ripples (pictured) farther away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast they are escaping from the gravitational attraction of the star. Their high speeds rule out the possibility they are caused by planets gravitationally disturbing material in the disk

This makes certain details in the disk more visible. 

According to the research, published in the journal Nature, the ripples farther away from the star seem to be moving faster than those closer to it. 

At least three of the features are moving so fast that they are escaping from the gravitational attraction of the star. 

Such high speeds rule out the possibility that these features are caused by objects, such as planets, gravitationally disturbing material in the disk. 

The team has also ruled out the theory that the waves were caused by the collision of two massive and rare asteroid-like objects releasing large quantities of dust, as well as the theory that spiral waves were triggered by instabilities in the system's gravity.

The team has also ruled out the theory the waves were caused by the collision of two asteroid-like objects, as well as the theory about spiral waves being triggered by instabilities in the system's gravity. Instead, they believe the explanation is linked to the star's flares (its location in Microscopium is pictured)

The team has also ruled out the theory the waves were caused by the collision of two asteroid-like objects, as well as the theory about spiral waves being triggered by instabilities in the system's gravity. Instead, they believe the explanation is linked to the star's flares (its location in Microscopium is pictured)

'One explanation for the strange structure links them to the star's flares,' said co-author Glenn Schneider of Steward Observatory in Phoenix, Arizona

'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.'

'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.'

The team plans to continue to observe the AU Mic system to try to understand what is happening, but, for now, admit these features remain a mystery. 

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