For the first time, a disk of material similar to that from which the planets in our Milky Way form is discovered around a young star in the Large Magellanic Cloud, a neighboring galaxy.
Observations from the ALMA (Atacama Large Millimeter/submillimeter Array) telescope in Chile show the existence of a young, massive star that is growing and accumulating material from its surroundings, forming a rotating disk.
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The disk and jet in the young star system HH 1177, seen with MUSE and ALMA.
Photo: ESO/ALMA (ESO/NAOJ/NRAO)/A. McLeod et al.
Accretion disks play an essential role in the formation of stars and planets in the Milky Way. For example, the Earth and the planets in our solar system were born from rocks and dust that orbited the sun.
When I first saw evidence of a rotating structure in the ALMA data, I couldn’t believe that we had discovered the first extragalactic accretion disk. It was an extraordinary moment, said astrophysicist Anna McLeod, a professor at the University of Durham and lead author of the paper published in the journal Nature (New Window).
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Artistic illustration depicting a forming star surrounded by a disk in which planets are forming.
Photo: ESO/L. Calcada
Our galactic neighborhood
- The Milky Way is one of a group of fifty closely spaced galaxies that make up the Local Group.
- Andromeda is 2.55 million light-years from the Sun. It is the closest spiral galaxy to the Milky Way.
- However, there are dwarf galaxies closer to us, in our neighborhood. The Canis Galaxy is 25,000 light-years away, the Sagittarius Galaxy is 80,000 light-years away, and the Large Magellanic Cloud and Small Magellanic Cloud are 160,000 and 210,000 light-years away from our galaxy.
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A system in training
In 2019, the MUSE instrument installed on the European Southern Observatory’s Very Large Telescope, also located in Chile, enabled the discovery of a region of the Large Magellanic Cloud populated by newly formed stars.
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Color composite image of the Large Magellanic Cloud region populated by newly formed stars.
Photo: ESO/Digitalized Sky Survey 2. Acknowledgments: Davide De Martin
At that time, MUSE also discovered a jet from a massive nascent star with a mass twelve times that of the Sun. This jet, which spans nearly 33 light-years, is named HH 1177. Not only is it the very first of its kind observed in visible light outside the Milky Way, but it is also one of the longest jets observed to date.
This work was carried out following the work from 2019. Their authors wanted to check whether the jet was related to the presence of an accretion disk. To determine this, scientists had to measure the movement of the dense gas around the star.
The frequency of light changes depending on how quickly the light-emitting gas is moving toward or away from us, says British astrophysicist Jonathan Henshaw of Liverpool John Moores University and co-author of the study.
This is the exact same phenomenon that occurs when the sound of an ambulance siren changes as it passes you, and the frequency of the sound changes from a higher level to a lower level.
Thanks to detailed frequency measurements from ALMA, researchers were able to detect the characteristic rotation of a disk, confirming the discovery of the first disk around a young extragalactic star.
Massive stars
To be classified as massive, a star must have a mass about eight times greater than that of the Sun. These stars form much faster and live much shorter lives than low-mass stars like our Sun, the researchers note.
Their observation is often complicated by the fact that they are bathed in the dusty material from which they evolve, but which also forms the disks from which the planets form.
In the case of the Large Magellanic Cloud, the material from which new stars form is fundamentally different from that of the Milky Way. Thanks to its low dust content, HH 1177 is no longer enveloped in its natural cocoon, giving astronomers a clear, if distant, view of star and planet formation.
Being able to study star formation at such incredible distances and in another galaxy is very exciting, says Anna McLeod.