Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Massive stars mark out Milky Way's 'missing' arms

17.12.2013
A 12-year study of massive stars has reaffirmed that our Galaxy has four spiral arms, following years of debate sparked by images taken by NASA's Spitzer Space Telescope that only showed two arms.

This shows the distribution of massive stars in the new study. Our location within the Galaxy is circled in black.

Credit: J. Urquhart et al. Background image by Robert Hurt of the Spitzer Science Center.

The new research, which is published online today [17 December] in the Monthly Notices of the Royal Astronomical Society, is part of the RMS Survey, which was launched by academics at the University of Leeds.

Astronomers cannot see what our Galaxy, which is called the Milky Way, looks like because we are on the inside looking out. But they can deduce its shape by careful observation of its stars and their distances from us.

"The Milky Way is our galactic home and studying its structure gives us a unique opportunity to understand how a very typical spiral galaxy works in terms of where stars are born and why," said Professor Melvin Hoare, a member of the RMS Survey Team in the School of Physics & Astronomy at the University of Leeds and a co-author of the research paper.

In the 1950s astronomers used radio telescopes to map our Galaxy. Their observations focussed on clouds of gas in the Milky Way in which new stars are born, revealing four major arms. NASA's Spitzer Space Telescope, on the other hand, scoured the Galaxy for infrared light emitted by stars. It was announced in 2008 that Spitzer had found about 110 million stars, but only evidence of two spiral arms.

The astronomers behind the new study used several radio telescopes in Australia, USA and China to individually observe about 1650 massive stars that had been identified by the RMS Survey. From their observations, the distances and luminosities of the massive stars were calculated, revealing a distribution across four spiral arms.

"It isn't a case of our results being right and those from Spitzer's data being wrong – both surveys were looking for different things," said Professor Hoare. "Spitzer only sees much cooler, lower mass stars – stars like our Sun – which are much more numerous than the massive stars that we were targeting."

Massive stars are much less common than their lower mass counterparts because they only live for a short time – about 10 million years. The shorter lifetimes of massive stars means that they are only found in the arms in which they formed, which could explain the discrepancy in the number of galactic arms that different research teams have claimed.

"Lower mass stars live much longer than massive stars and rotate around our Galaxy many times, spreading out in the disc. The gravitational pull in the two stellar arms that Spitzer revealed is enough to pile up the majority of stars in those arms, but not in the other two," explains Professor Hoare. "However, the gas is compressed enough in all four arms to lead to massive star formation."

Dr James Urquhart from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and lead author of the paper, said: "It's exciting that we are able to use the distribution of young massive stars to probe the structure of the Milky Way and match the most intense region of star formation with a model with four spiral arms."

Professor Hoare concludes, "Star formation researchers, like me, grew up with the idea that our Galaxy has four spiral arms. It's great that we have been able to reaffirm that picture."

Further information

Link to research paper: http://dx.doi.org/10.1093/mnras/stt2006

Professor Melvin Hoare is available for interview. Please contact Sarah Reed, Press Officer, University of Leeds on 0113 34 34196 or email s.j.reed@leeds.ac.uk

Image

Image credit: J. Urquhart et al. Background image by Robert Hurt of the Spitzer Science Center.

University of Leeds

The University of Leeds is one of the largest higher education institutions in the UK and a member of the Russell Group of research-intensive universities.

The 2008 Research Assessment Exercise showed the University of Leeds to be the UK's eighth biggest research powerhouse and the University's vision is to secure a place among the world's leading universities by 2015.

Sarah Reed | EurekAlert!
Further information:
http://www.leeds.ac.uk

More articles from Physics and Astronomy:

nachricht Bright Points in Sun's Atmosphere Mark Patterns Deep In Its Interior
18.04.2014 | NASA/Goddard Space Flight Center

nachricht Better Thermal-Imaging Lens From Waste Sulfur
18.04.2014 | University of Arizona

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Anzeige

Anzeige

Event News

Siemens at the 2014 UIC ERTMS World Conference in Istanbul

01.04.2014 | Event News

AERA Meeting: German and US-American educational researchers in dialogue

28.03.2014 | Event News

WHS Regional Meeting: International experts address health challenges in Latin America

24.03.2014 | Event News

 
Latest News

A cross-section of the Universe

18.04.2014 | Physics and Astronomy

More, bigger wildfires burning western U.S., study shows

18.04.2014 | Studies and Analyses

High disease load reduces mortality of children

18.04.2014 | Social Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>