An artistic illustration depicts the HH 1177 system, located in a neighboring galaxy called the Large Magellanic Cloud. The massive young star at the center pulls in material from a rotating disk of gas and dust, but it also expels matter in the form of jets.
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For the first time, astronomers have glimpsed a young star outside the Milky Way, surrounded by a dense disk where planets can form.
The massive star, called HH 1177, and its rotating disk were spotted in the Large Magellanic Cloud, a neighboring dwarf galaxy about 160,000 light-years away. The unprecedented discovery could help scientists better understand the formation of stars and planets.
A newborn star increases in size by pulling matter from its surroundings. Gas and dust accumulate in a flat disk around the star, known as the accretion disk, as a result of strong gravitational forces. The rotating disk transports matter to the star, which gets bigger and bigger. The greater the mass of the star, the more powerful its gravitational field becomes, thus pulling more gas and dust into the disk.
A colossal star like HH 1177 lives fast and dies young, forming more quickly and having only a lifetime that is a fraction of that of a star like our Sun. This shortened timeline makes it difficult to observe the early stages of a massive star in our Galaxy, since both the star and its disk are hidden from view by the dusty material from which it forms.
But the material from which stars are formed in the Large Magellanic Cloud is different from that of the Milky Way.
HH 1177 is within a stellar nursery, called N180, which has less dust and a lower abundance of metal. The star is not obscured by a cocoon of gas and dust, providing a distant but clear view.
“When I first saw evidence of a rotating structure in the ALMA data, I couldn’t believe we had detected the first extragalactic accretion disk, it was a special moment,” said the study’s lead author, Dr. Durham University, UK. United, in a statement. “We know that disks are vital for the formation of stars and planets in our galaxy, and here, for the first time, we are seeing direct evidence of this in another galaxy.”
Astronomers detected the star, which is estimated to be about 15 times the mass of our Sun, using the Atacama Large Millimeter/submillimeter Array of telescopes in Chile, known as ALMA. The findings were published Wednesday in the journal Nature.
The ALMA observations followed an earlier detection made with the European Southern Observatory’s Very Large Telescope. The Multi Unit Spectroscopic Explorer, or MUSE instrument, on the telescope captured a jet of material released from the young star. HH 1177 was found deep in a gas cloud in the galaxy.
“We discovered a jet being launched from this massive young star, and its presence is a signal for continued disk accretion,” said McLeod.
ESO/ALMA (ESO/NAOJ/NRAO)/A. McLeod et al.
Several observatories contributed to the discovery of the extragalactic disk. The star and its jets were first discovered using the Very Large Telescope’s MUSE instrument (left and center). ALMA observations (right) revealed the rotating disk around the star.
To discern whether a disk was present around the star, the team needed to measure how quickly dense gas was moving around the star.
When matter is attracted to a young, evolving star, it does not fall directly on the celestial object. Instead, the material flattens and rotates around the star and forms a disk-like structure. The disk spins faster at its center. The difference in speed can help astronomers determine whether a disk has formed around a star.
“The frequency of light changes depending on how quickly the gas emitting the light approaches or moves away from us,” study co-author Dr. Jonathan Henshaw, a researcher at Liverpool John Moores University in the United Kingdom, said in a statement. 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.”
ALMA observations were able to make detailed measurements of the disk’s rotation.
Young stars are not the only celestial phenomena with accretion disks. Supermassive black holes also have thin, hot disks of matter rotating around them, which they feed on.
“We are in an era of rapid technological advancement when it comes to astronomical facilities,” said McLeod. “Being able to study how stars form at such incredible distances and in a different galaxy is very exciting.”