Large Magellanic Cloud. A disk around a star in another galaxy has been discovered for the first time

The Large Magellanic Cloud is a neighboring galaxy to our own. The disk discovered there is identical to the disks in which planets form in the Milky Way. The discovery was made using the Atacama Large Millimeter/submillimeter Array (ALMA) radio interferometer in Chile, of which the European Southern Observatory (ESO) is a partner.

– When I first saw evidence of the rotating structure in the ALMA data, I couldn’t believe we had discovered the first exoplanet accretion disk. Anna McLeod, a professor at Durham University in the United Kingdom, and first author of the research published Wednesday in the journal Nature, said it was a special moment. She added: “We know that disks are key to the formation of stars and planets in our galaxy, and now we see for the first time direct evidence that this is also the case in another galaxy.”

This research expands on observations made with the Multi-Unit Spectroscopic Explorer (MUSE) instrument on the European Southern Observatory’s Very Large Telescope, which detected a stream from a forming star – in a system called HH 1177 – deep in a gas cloud in the Large Magellanic Cloud.

– We discovered that a jet emanates from a young, massive star, and its presence heralds ongoing disk accretion – MacLeod points out. But to confirm whether this type of disk actually existed, the research team needed to measure the movement of dense gas around the star.

When matter is pulled toward the accreting star, it does not fall directly onto it, but rather flattens out to form a rotating disk around it. The closer to the center, the faster the disk rotates, and the difference in speeds is evidence that shows astronomers the presence of an accretion disk.

– The frequency of light changes depending on how quickly the gas emitting it moves towards us or away from us – explains Jonathan Henshaw, trainee at Liverpool John Moores University in the UK, and co-author of the research. He added that this is the same phenomenon that occurs when the tone of the ambulance siren changes as it passes us and the sound frequency decreases from top to bottom.

Precise frequency measurements using ALMA allowed the authors to discern the disc’s distinct rotation, confirming the discovery of the first disc around a young extragalactic star.

Massive stars like the ones observed here form much faster and live much shorter than low-mass stars like the Sun. In our galaxy, massive stars are difficult to observe and are often obscured by the dust they create when the disk surrounding them forms. However, in the Large Magellanic Cloud, a galaxy 160,000 light-years away, the material from which stars are made is radically different from that in the Milky Way. With less dust, HH 1177 is no longer obscured by its natural cocoon, giving astronomers a view of star and planet formation.

– In the case of astronomical infrastructure, we are in an era of rapid technological development – adds McLeod. “Being able to study how stars form at such amazing distances, and in another galaxy, is very exciting,” he added.