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Astronomers identify a young heavyweight star in the Milky Way

Last Updated on Friday, 19 August 2016 15:06
Published on Monday, 22 August 2016 09:00

Astronomers have identified a young star, located almost 11,000 light years away, which could help us understand how the most massive stars in the Universe are formed. This young star, already more than 30 times the mass of our Sun, is still in the process of gathering material from its parent molecular cloud, and may be even more massive when it finally reaches adulthood. The results will be presented this week at the Star Formation 2016 conference held at the University of Exeter, UK, and are to be published in Monthly Notices of the Royal Astronomical Society.

 

The researchers, led by a team at the University of Cambridge, have identified a key stage in the birth of a very massive star, and found that these stars form in a similar way to much smaller stars like our Sun – from a rotating disc of gas and dust.

In our galaxy, massive young stars – those with a mass at least eight times greater than the Sun – are much more difficult to study than smaller stars. This is because they live fast and die young, making them rare among the 100 billion stars in the Milky Way, and on average, they are much further away.

 

“An average star like our Sun is formed over a few million years, whereas massive stars are formed orders of magnitude faster — around 100,000 years,” said Dr John Ilee from Cambridge’s Institute of Astronomy, the study’s lead author. “These massive stars also burn through their fuel much more quickly, so they have shorter overall lifespans, making them harder to catch when they are infants.”

The protostar that Ilee and his colleagues identified resides in an infrared dark cloud - a very cold and dense region of space which makes for an ideal stellar nursery. However, this rich star-forming region is difficult to observe using conventional telescopes, since the young stars are surrounded by a thick, opaque cloud of gas and dust. But by using the Submillimeter Array (SMA) in Hawaii and the Karl G Jansky Very Large Array (VLA) in New Mexico, both of which use relatively long wavelengths of light to observe the sky, the researchers were able to ‘see’ through the cloud and into the stellar nursery itself.

 

By measuring the amount of radiation emitted by cold dust near the star, and by using unique fingerprints of various different molecules in the gas, the researchers were able to determine the presence of a ‘Keplerian’ disc - one which rotates more quickly at its centre than at its edge.

thumb mm1 artistsArtist’s impression of the disc and outflow around the massive young star. Credit: A. Smith (Institute of Astronomy, Cambridge)

 

“This type of rotation is also seen in the Solar System - the inner planets rotate around the Sun more quickly than the outer planets,” said Ilee. “It’s exciting to find such a disc around a massive young star, because it suggests that massive stars form in a similar way to lower mass stars, like our Sun.”

 

The initial phases of this work were part of an undergraduate summer research project at the University of St Andrews, funded by the Royal Astronomical Society (RAS). The undergraduate carrying out the work, Pooneh Nazari, said, “My project involved an initial exploration of the observations, and writing a piece of software to ‘weigh’ the central star. I’m very grateful to the RAS for providing me with funding for the summer project — I’d encourage anyone interested in academic research to try one!”

 

From these observations, the team measured the mass of the protostar to be over 30 times the mass of the Sun. In addition, the disc surrounding the young star was also calculated to be relatively massive, between two and three times the mass of our Sun. Dr Duncan Forgan, also from St Andrews and lead author of a companion paper, said, “Our theoretical calculations suggest that the disc could in fact be hiding even more mass under layers of gas and dust. The disc may even be so massive that it can break up under its own gravity, forming a series of less massive companion protostars.”

 

The next step for the researchers will be to observe the region with the Atacama Large Millimetre Array (ALMA), located in Chile. This powerful instrument will allow any potential companions to be seen, and shed further light on this intriguing young heavyweight in our galaxy.

 

Media contacts

 

Ms Sarah Collins
Office of Communications, University of Cambridge
Tel: +44 (0)1223 765542
Mob: +44 (0)7525 337458
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Dr Morgan Hollis
Royal Astronomical Society
Tel: +44 (0)20 7292 3977
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Dr Sam Lindsay
Royal Astronomical Society
Tel: +44 (0)20 7292 3976
Mob: +44 (0)7957 566 681
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Science contact

 

Dr John Ilee
Institute of Astronomy
University of Cambridge
Tel: +44 (0) 1223 337513
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Images and captions

 

Artist’s impression of the disc and outflow around the massive young star. Credit: A. Smith (Institute of Astronomy, Cambridge)

 


Further information

 

This research will be published in:
J.D. Ilee et al. ‘G11.92-0361 MM1: A Keplerian disc around a massive young proto O-star.’ Monthly Notices of the Royal Astronomical Society (2016): DOI: 10.1093/mnras/stw1912

 

D. H. Forgan et al. ‘Self-gravitating disc candidates around massive young stars.’ Monthly Notices of the Royal Astronomical Society (2016): DOI: 10.1093/mnras/stw1917

 

Advance Access copies of the papers can be downloaded at:
http://mnras.oxfordjournals.org/content/early/2016/08/09/mnras.stw1912.abstract?keytype=ref&ijkey=eluyNqjmL10BXw1

 

http://mnras.oxfordjournals.org/content/early/2016/08/09/mnras.stw1917.abstract?keytype=ref&ijkey=zOh0M2tLry5D6rD

 

The team is composed of John D. Ilee (Institute of Astronomy, University of Cambridge, UK), Claudia. J. Cyganowski (University of St Andrews, UK), Pooneh Nazari (University of St Andrews, UK), Todd R. Hunter (National Radio Astronomy Observatory, Charlottesville, USA), Crystal Brogan (National Radio Astronomy Observatory, Charlottesville, USA), Duncan H. Forgan (University of St Andrews, UK) and Qizhou Zhang (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA).

 

This work has been supported by a grant from the European Research Council.

 


Notes for editors

 

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter via @royalastrosoc