Worlds collide in double star systems

By Howard Falcon-Lang
Science reporter, BBC News

  • Published
Worlds collide around double star
Image caption,
Astronomers record massive planetary collisons around distant binary stars

Astronomers have uncovered evidence for massive planetary collisions around binary stars.

Binary systems comprise two stars that orbit closely around one another.

The erratic behaviour of these twin suns can fling orbiting planets into devastating head-on collisions.

In the new study, the pulverised remains of former worlds have been spotted around four different binary stars using Nasa's Spitzer Space Telescope.

The double stars that are the subject of present attention orbit only 3.2 million km apart (two million miles). This is a mere 2% of the distance between the Earth and our own Sun.

As they twirl around one another every few days, their powerful magnetic fields cause them to move closer together. This results in gravitational changes that disrupt the trajectory of orbiting planets.

These changes can send planets smashing into one another.

Evidence for such colliding worlds is reported by Dr Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and his US team, and published in Astrophysical Journal Letters.

The stuff of science fiction

Dr Drake said, "This is real-life science fiction. [Such planetary] collisions could be common."

The double stars studied are about a billion years old, about the same age as our Sun when life evolved on Earth.

Dr Drake continued: "It's theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it would be doomed."

The discovery was made when astronomers spotted the infrared glow of hot dusty disks - about the temperature of molten lava - around several double stars.

Normally such dust would have been blown away as the stars matured. Its persistence in this case indicated to astronomers that something - most likely planetary collisions - must be kicking up fresh dust.

If any unfortunate life forms did exist in these star systems, they would have had one very minor consolation.

The view would have been terrific, with the sky filled with two huge suns as it is on the desert planet Tatooine in Star Wars.