Planet-forming disc around star seen beyond our galaxy for first time
First insight into planet formation in other galaxies.
ASTRONOMERS PEERING into the nearby galaxy known as the Large Magellanic Cloud have spotted something that has never been seen outside our own Milky Way: a disc of gas and dust around a young star.
The disc is identical to those which form planets within our galaxy over millions of years. As a young star grows, its gravity accretes matter from its surroundings to form a rotating accretion disc, also called a proto-planetary disc because clumps formed within it are believed to be the seeds of planets.
Detection of the intergalactic proto-planetary disc in the Large Magellanic Cloud was made using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. It turned its eyes to the young star system after the European Southern Observatory’s Very Large Telescope spotted a powerful jet of matter emerging from the star: a signpost of disc formation.
“When I first saw evidence for a rotating structure in the ALMA data, I could not believe that we had detected the first extragalactic accretion disc,” says lead author Anna Mcleod, an extragalactic astronomer at Durham University, UK. “We know discs are vital to forming stars and planets in our galaxy, and here, for the first time, we’re seeing direct evidence for this in another galaxy.”
Mcleod and team determined that the matter around the star was rotating by analysing the wavelength of light coming from the disc.
“The frequency of light changes depending on how fast the gas emitting the light is moving towards or away from us,” explains co-author Jonathan Henshaw, a research fellow at the UK’S Liverpool John Moores University. “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.”
If the disc is rotating faster closer to the star, this indicates to astronomers that an accretion disc is present.
“We are in an era of rapid technological advancement when it comes to astronomical facilities,” Mcleod says. “Being able to study how stars form at such incredible distances and in a different galaxy is very exciting.”
The discovery is detailed in a paper published in Nature.