ESO spots a circumstellar disk warped by a triple-star system

Hyperaxion Sep 4, 2020

The GW Orionis system is located about 1,300 light-years away from Earth, in the Orion constellation.

Astronomers at the European Southern Observatory (ESO) have identified the first direct evidence that groups of stars can warp a circumstellar disk.

The research, recently published in the journal Science, also used data from the ALMA Observatory in Chile.

ESO spots a circumstellar disk warped by a triple-star system
(Credit: ESO / L. Calçada, Exeter / Kraus et al.).

The Solar System is remarkably flat, with all the planets orbiting in the same plane, but this is not always the case. When the protoplanetary disk orbits more than one star, that disk can be warped and shattered, which affects the process of planet formation.

In the new study, scientists spotted GW Orionis, a system consisting of three stars and a fragmented planet-forming disk located about 1,300 light-years away, in the Orion constellation.

Simulation of stars' movement and the planet-forming disc surrounding them.
Simulation of stars’ movement and the planet-forming disc surrounding them. (Credit: European Southern Observatory (ESO)).

“Our images reveal an extreme case where the disc is not flat at all, but is warped and has a misaligned ring that has broken away from the disc,” said Stefan Kraus, the study’s leader and professor of astrophysics at the University of Exeter.

According to the astronomers, this inner ring contains 30 Earth-masses of dust, more than enough to form planets. If they form, these objects will orbit one of the system’s stars in extremely oblique orbits.

“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,” explained Alison Young, one of the researchers.

Since more than half of the stars in the sky belong to a binary or multiple star system, scientists are excited to continue investigating the matter.

According to them, there may be a vast and unknown population of exoplanets orbiting their stars in very oblique and long trajectories.

GW Orionis images, taken by two different telescopes.
GW Orionis images, taken by two different telescopes. (Credit: ALMA (ESO / NAOJ / NRAO), ESO / Exeter).

Methodology

The team included specialists from the United Kingdom, Belgium, Chile, France, and the United States. They combined their observations with computer simulations to understand what brought the GW Orionis system to its “current” state – and it worked.

For the first time, astronomers were able to link the observed misalignments to the disc-tearing effect.

The disc-tearing effect is the idea that conflicting gravitational pull from stars on different planes can warp and tear apart their planet-forming disc.

Interestingly, another group of scientists who studied the same system using ALMA believes that one more variable is needed to explain the state of GW Orionis.

“We think that the presence of a planet between these rings is needed to explain why the disc tore apart,” said Jiaqing Bi, leader of previous research on GW Orionis, published in May in The Astrophysical Journal Letters.

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