For the first time, astronomers have observed a disc around a young star in a galaxy far, far away—specifically, outside of our home galaxy, the Large Magellanic Cloud. This extragalactic neighbor of ours is located almost 200,000 light-years away from Earth and could crash into our home galaxy in about two billion years. Exciting, no?
[Related: A ‘bridge of stars’ connects two of our closest galaxies.]
The remarkable observations were made with the Atacama Large Millimeter/submillimeter Array in Chile. A massive young star in the star system HH 1177 is growing and taking in matter from its surroundings, resulting in the formation of a spinning disc called an accretion disc. This is the first time that astronomers have seen an accretion disc in a galaxy outside of our own. The groundbreaking discovery was recently described in a study published in the journal Nature.
“When I first saw evidence for a rotating structure in the ALMA data I could not believe that we had detected the first extragalactic accretion disc, it was a special moment,” said Anna McLeod, a study co-author and astronomer at Durham University in the United Kingdom, in a statement. “We know discs are vital to forming stars and planets in our galaxy, and here, for the first time, we’re seeing direct evidence for this in another galaxy.”
This new study follows previous observations of star system HH 1177 made with the Multi Unit Spectroscopic Explorer instrument on the European Southern Observatory’s Very Large Telescope. In 2018, the telescope spotted a jet from a forming star located deep inside a gas cloud in the Large Magellanic Cloud.
“We discovered a jet being launched from this young massive star, and its presence is a signpost for ongoing disc accretion,” said McLeod.
In order to confirm the presence of an accretion disc around the star, the authors needed to measure the movement of dense gas around the young star. As matter is pulled towards this expanding star, it can’t fall directly onto it. The matter flattens into a spinning disc around the star instead. ALMA was able to provide detailed frequency measurements that made it possible to distinguish the characteristic spin of a disc and confirm the detection of the first disc around a young star outside of our galaxy.
“The frequency of light changes depending on how fast the gas emitting the light is moving towards or away from us,” said Jonathan Henshaw, study co-author and astrophysicist at Liverpool John Moores University in the UK, in a statement. “This is precisely the same phenomenon that occurs when the pitch of an ambulance siren changes as it passes you and the frequency of the sound goes from higher to lower.”
[Related: Your guide to the types of stars, from their dusty births to violent deaths.]
Curious to learn more about this groundbreaking observation? You can read more here.
