Scientists have finally confirmed that our Milky Way galaxy has four spiral arms. This confirmation has been done after a study of massive stars in the Milky Way for about 12-years.
Monthly Notices of the Royal Astronomical Society
We live in Milky Way galaxy and that is the reason, we cannot look at its shape from outside – at last not at this time, perhaps in the future we may be able to see – so, the scientists devised a way to deduce its shape from the study of the stars present in it and their distances from us.
Initially, in 1950s, astronomers used radio telescopes to observe our Galaxy with the help of clouds of gas in which new stars are formed. They noted four major arms of the Milky Way galaxy. Then, NASA’s Spitzer telescope looked at low-mass stars in 2008 and showed only two arms resulting in a debate among astronomers.
In the present study, astronomers used several radio telescopes in Australia, USA and China and looked at about 1650 massive stars that had been identified by the RMS Survey. They reassured that our Milky Way galaxy has four spiral arms. Massive stars have less life, i.e. about 10 million years, than lower mass counterparts resulting in their less common presence in galaxies.
“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 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.. “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.”
Professor Hoare concluded, “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.”
Massive stars mark out Milky Way’s ‘missing’ arms – University of Leeds (http://goo.gl/O9NLdq)
J. S. Urquhart et al. (2013). The RMS survey: galactic distribution of massive star formation Monthly Notices of the Royal Astronomical Society DOI: 10.1093/mnras/stt2006