Astronomers discover ring-shaped star disk outside the Milky Way for the first time

A groundbreaking discovery by astronomers has revealed a rotating disk around a massive star in the Large Magellanic Cloud, providing new insights into star formation in different galactic environments. An international team of astronomers reports the first discovery of a rotating disk surrounding a forming high-mass star in a galaxy other than the Milky Way.

Astronomers have discovered a rotating disk surrounding a massive star forming in the Large Magellanic Cloud, the most distant observation ever made. The discovery, made using the ALMA observatory and detailed in the journal Nature, reveals key differences in the star formation processes of different galaxies, highlighting that the Large Magellanic Cloud is less dusty and metal-rich than the Milky Way. Image credit: ESO/L. Calcada

This disk surrounds a young, massive star in a stellar nursery called N180, located in a nearby dwarf galaxy called the Large Magellanic Cloud.

The disk is 163,000 light-years away from Earth, making it the most distant disk around a massive star ever directly detected.

This artist's impression shows the HH1177 system, located in the Large Magellanic Cloud, a neighboring galaxy to our Milky Way. The young, massive stellar object glowing at the center is collecting material from the dusty disk while ejecting it in powerful jets. Image credit: ESO/M. Kornmesser

Making groundbreaking observations with ALMA

Using a European Southern Observatory (ESO) partner, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, researchers have observed gas motions around a young stellar object in the Large Magellanic Cloud that are consistent with a Kepler accretion disk - an accretion disk that promotes the growth of stars by injecting material.

The research team, led by Durham University and including astronomers from the UK Astronomy Technology Centre, published the results in the journal Nature.

When material is pulled toward a growing star, it cannot fall directly onto the star but flattens out to form a disk that orbits the star. Closer to the center of the star, the disk spins faster, and this difference in speed is the "smog gun" that shows astronomers the existence of an accretion disk.

Using the combined capabilities of the European Southern Observatory's (ESO) Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, we observed a disk around a young, massive star in another galaxy. The image on the left is an observation from the Multi-Unit Spectroscopic Explorer (MUSE) on the VLT, showing the parent cloud LHA120-N180B in which the system, named HH1177, was first observed. The middle image shows the jets accompanying it. The upper half of the jet is slightly toward us, giving it a blue shift; the lower half is receding from us, giving it a red shift. Subsequent ALMA observations (right) revealed a rotating disk around the star, with the sides of the disk also moving toward and away from us. Source: ESO/ALMA(ESO/NAOJ/NRAO)/A.McLeodetal.

Lead author of the study, Dr Anna McLeod from Durham University's Center for Extragalactic Astronomy, said: "When I first saw evidence of rotating structure in the ALMA data, I couldn't believe we had detected the first extragalactic accretion disk; this was a special moment. We knew the disk was important for The formation of stars and planets in the Milky Way is crucial, and here, for the first time, we see direct evidence of this in another galaxy. We are in an era of rapid advances in astronomical facilities and technology, and it is really exciting to be able to study how stars form at such great distances and in different galaxies."

At the center of this mosaic is a realistic image of the young star system HH1177, located in the Large Magellanic Cloud, a neighboring galaxy to the Milky Way. The image, obtained by the Multi-Unit Spectroscopic Explorer (MUSE) on the European Southern Observatory's Very Large Telescope (VLT), shows jets emanating from the star. The researchers then found evidence of a disk surrounding the young star using the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner. The image at right is an artist's impression of the system, showing the jets and disks. Source: ESO/A.McLeodetal./M.Kornmesser

Discovered Characteristics and Impact

Massive stars form much faster and have much shorter lifespans than lower-mass stars like the Sun. In our Milky Way, these massive stars are notoriously difficult to observe, often obscured by dusty material as a disk forms around them.

Unlike similar circumstellar disks in the Milky Way, this system is optically visible, likely due to the lower dust and metal content in its surroundings. This allows astronomers to peer into the accretion dynamics usually hidden behind gas and dust.

Analysis of the disk shows that at larger distances from the central star, the inner Keplerian region is transitioning into invaginating material. The star is estimated to be about 15 times more massive than the Sun.

While the Milky Way's disk has many familiar features, some intriguing differences emerge. The low metal content typical of LMC seems to make the disc more stable when broken.