Star debris reveal unseen planetary system

The largest and most sensitive visible-light imaging survey of dusty debris disks around other stars point towards an unseen planetary system that could be quite chaotic, astronomers who did the survey using NASA's Hubble Space Telescope reported.

A debris disk is a circumstellar disk of dust and debris in orbit around a star.

Once thought to be simply pancake-like structures, the unexpected diversity and complexity and varying distribution of dust among these debris systems strongly suggest the disks are gravitationally-affected by unseen exoplanets orbiting the star, the researchers noted.

These dusty disks, likely created by collisions between leftover objects from planet formation, were imaged around stars as young as 10 million years old and as mature as more than 1 billion years old.

"It is like looking back in time to see the kinds of destructive events that once routinely happened in our solar system after the planets formed," said survey leader Glenn Schneider of the University of Arizona's Steward Observatory.

"There is some sort of interdependence between a planet and the accompanying debris that might affect the evolution of these exoplanetary debris systems," Schneider explained.

The researchers discovered that no two "disks" of material surrounding stars look the same.

"Some of the substructures could be signposts of unseen planets," Schneider added.

Irregularities observed in one ring-like system in particular, around a star called HD 181327, resemble a huge spray of debris possibly caused by the recent collision of two bodies into the outer part of the system.

"This spray of material is fairly distant from its host star - roughly twice the distance that Pluto is from the sun," said co-investigator Christopher Stark.

"Catastrophically destroying an object that massive at such a large distance is difficult to explain, and it should be very rare. If we are in fact seeing the recent aftermath of a massive collision, the unseen planetary system may be quite chaotic," Stark pointed out.

The survey's results appeared in the The Astronomical Journal.