Stars get their discs in a twist

An international team of astronomers that includes Richard Nelson of Queen Mary University of London (QMUL) have discovered a truly unusual example of planet formation around a star.

The familiar picture is that planets form from a disc of gas and dust that circles around a star. When two stars are in orbit around each other — a system known as a binary star — we would not be surprised to see a disc around each star. But now the astronomers, using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, have discovered a binary system in which each star does indeed have a disc around it, but there is also a third, shared disc surrounding the pair of stars.

Even more strangely, the three discs are not aligned with respect to each other, whereas we would expect them all to line up and lie in the same plane. This challenges our understanding of how these systems form, so the next step is to use computer simulations to try to figure out how this can have come about. “This strange and unexpected result is just the beginning of a new trail that will lead us to a greater understanding of the process of planet formation. Further observations with ALMA will help us to improve the computer models and hopefully lead to an idea of how common this sort of system might be,” said Richard Nelson.

This intriguing result is published in the journal Astrophysical journal Letters and is also featured in the Research Highlights section of the journal Nature.

This work involved astronomers from: the Niels Bohr International Academy, University of Copenhagen, Denmark; The Centre for Star and Planet Formation, The Niels Bohr Institute & Natural History Museum of Denmark, University of Copenhagen, Denmark; Leiden Observatory, Leiden University, The Netherlands; and the Astronomy Unit, Queen Mary University of London, UK.

Image credit: Christian Brinch, NBI, KU