Tatooine-like planets may form in tilted rings around multiple stars

4 Sep 2020

A superimposed image of the disc taken by the various astronomical instruments. Image: ESO/Exeter/Kraus et al, ALMA (ESO/NAOJ/NRAO)

Astronomers have seen the first direct evidence that a group of stars can tear apart their planet-forming discs.

One of the most famous fictional planets surrounded by multiple stars, Tatooine from the Star Wars universe, could be closer to reality than we once thought, according to a new discovery made by astronomers.

Using the Very Large Telescope of the European Southern Observatory (ESO) and the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers examined the system known as GW Orionis. Unlike our solar system, which is remarkably flat with planets orbiting the same plane, this system – located just over 1,300 light years away – has three stars and a deformed disc surrounding them.

The astronomers, who published their findings to Science, said this is the first direct evidence that groups of stars can tear apart their planet-forming discs. According to Prof Stefan Kraus of the University of Exeter, this discovery is an extreme case where the disc is not flat, but is warped and has a misaligned ring that has broken away from the disc.

This strange, tilted ring is located in the inner part of the disc close to the three stars and is estimated to contain 30 Earth-masses of dust, which could be enough to form planets. Any planets that do form within the misaligned ring, the researchers said, would have highly oblique orbits and may become more common sights once ESO’s Extremely Large Telescope (ELT) is up and running later this decade.

11 years of work

This latest discovery is the result of 11 years of observations of GW Orionis, combining various powerful instruments to study the gravitational dance of the three stars and map their orbits.

Alison Young of the University of Exeter commented: “We found that the three stars do not orbit in the same plane, but their orbits are misaligned with respect to each other and with respect to the disc.”

Once the team of international researchers combined these observations with computer simulations, they were able to clearly link the observed misalignments to the theoretical ‘disc-tearing effect’ for the first time.

These simulations showed that the misaligned orbits of the three stars could cause the disc around them to break into distinct rings, thereby confirming astronomer’s observations. Once the ELT is operational, the researchers are hopeful that it could unravel the nature of GW Orionis and reveal young planets forming around its three stars.

Colm Gorey was a senior journalist with Silicon Republic