For a long time, astronomers thought that binary star systems, where two stars orbit each other, were too chaotic for planets to form in large numbers. The competing gravitational forces seemed to disrupt solid aggregations.
Yet a team from the University of Lancashire has just overturned this perception.
Simulation of a protoplanetary disk around a binary star becoming unstable and fragmenting, forming planets.
Credit: Teasdale et al.
Computer simulations led by Matthew Teasdale and his colleagues show that near the two stars, conditions are too violent for planets to emerge—a true "forbidden zone". But beyond a certain distance, the environment changes dramatically. The gas and dust disk remains disturbed, but from this disturbance planets form through a process called gravitational instability.
This instability can fragment the disk into several clumps, quickly giving birth to giant gaseous planets, similar to Jupiter. "What we are discovering is that these systems can be extremely productive," explains Dimitris Stamatellos, co-author of the study. Once past the dangerous zone, planets can form in large numbers and very quickly.
The gravitational environment of these systems also has a spectacular effect: some planets can be completely ejected from their system, becoming rogue worlds, floating alone in interstellar space.
These results indicate that worlds with two suns, like the famous planet Tatooine from Star Wars, could be much less rare than previously imagined. More than 50 circumbinary planets—orbiting two stars—have already been discovered, several of them on very wide orbits.
Astronomers now hope to use powerful instruments like the James Webb Space Telescope or the future Extremely Large Telescope to observe these disks in the process of fragmenting, and thus witness the birth of these planets in real time.
This research was published on April 27 in the journal
Monthly Notices of the Royal Astronomical Society.