The Large Magellanic Cloud is a companion galaxy of the Milky Way, about 160,000 light-years away from Earth. The image below shows a brilliant region in the Large Magellanic Cloud, captured by the Multivariate Spectral Detector (MUSE) on the Very Large Telescope (VLT). This region is known as LHA 120-N 180B and is a nebula known as the ionized hydrogen region (HII region).
MUSE captures the dazzling region in the Large Magellanic Cloud where new stars are forming. The relatively small amount of dust in the Large Magellanic Cloud and MUSE's keen vision allow us to see the intricate details of this region in the visible light band. (Photo: ESO, A McLeod et al.)
The HII region is an interstellar cloud of ionized hydrogen, such a region is the cradle of stars, and newly formed massive stars ionize the surrounding gases to form a spectacular spectacle. The unique shape of LHA 120-N 180B consists of a large ionized hydrogen bubble surrounded by four smaller bubbles.
This color image is synthesized from data collected by the digitized Sky Survey 2 and shows the area around LHA 120-N 180B. (Photo: ESO/Digitized Sky Survey 2. Acknowledgment: Davide De Martin）
In 2019, deep in the luminous region of LHA 120-N 180B, MUSE discovered a jet from a massive young star. This is the first time such a jet has been observed in visible light outside the Milky Way. Normally, such jets are obscured by the surrounding dust, making them only visible in the infrared or radio bands.
However, due to the relatively dust-free environment of the Large Magellanic Cloud, the jet, named HH 1177, was able to be observed in the visible light range. With a length of nearly 33 light-years, it is one of the longest jets observed to date.
The middle image shows the jet, with the top of the jet slightly facing us, blueshifted, and the bottom of the jet, moving away from us, redshifted. Shown on the right are observations of the Atacama Large Millimeter/Submillimeter Array (ALMA), indicating that the star has a rotating disk around it, and similarly, its sides are moving closer to or farther away from us. (Photo: ESO/ALMA (ESO/NAOJ/NRAO)/A. McLeod et al.)
Astronomers believe that the presence of jets is a sign that disk accretion is underway. But to confirm that such a disk does exist around the star, it is also necessary to measure the movement of the dense gas around the star.
When matter is attracted by the gravitational pull of a star, it does not fall directly into the star. Due to the conservation of angular momentum, the matter will eventually form a rotating disk around the star. In the region near the center, the disk rotates faster, and this difference in speed is conclusive evidence of the existence of accretion disks in astronomy.
The center of this image shows a real image of the young star system HH 1177 obtained by MUSE. The researchers then used ALMA to look for evidence of the disk surrounding the young star. The illustration on the right shows an artistic conception of this celestial object, depicting a jet stream and a disk. (Photo: ESO/A. McLeod et al./M. Kornmesser)
In a new study published in the journal Nature, astronomers saw a rotating structure by using detailed frequency measurements of the Atacama Large Millimeter/Submillimeter Array (ALMA). This is the first time astronomers have seen direct evidence of an accretion disk around a young star in another galaxy.
Artistic conception of the HH 1177 system, with a young, massive star object glowing at the center accretting material from a dust disk while also expelling material with a powerful jet. Using ALMA, a team of astronomers succeeded in finding evidence of the disk's existence by observing its rotation. (Photo: ESO/M. Kornmesser)
The researchers say the study provides an answer to a big question: It provides strong evidence that massive stars with masses several times the size of the Sun form in the same way as small-mass stars.
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