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Dec 18, 2013 11:55 AM EST

Milky Way Galaxy Has Four Arms, Reaffirming Old Data and Contradicting Recent Research


The Milky Way Galaxy does not have two stellar arms, it has four, according to a new long-term study that contradicts images from NASA's Spitzer Space Telescope.

Reported in a press release, researchers announced the results of a 12-year study and confirmed that large star formations make up four "arms" for the Milky Way Galaxy. Since the astronomers are inside the galaxy looking out, the study had to carefully examine star locations and their distance from Earth to deduce the shape of the Milky Way.

"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," study co-author Melvin Hoare, a member of the RMS Survey Team in the School of Physics & Astronomy at the University of Leeds, said in the release.

The researchers published their work in Tuesday in the journal Monthly Notices of the Royal Astronomical Society, an RMS Survey publication launched by Leeds.

Observations made by astronomers in the 1950s initially revealed the Milky Way to have four spiraling arms. Those scientists used radio telescopes and focused on gas clouds and newborn stars.

NASA's Spitzer Space Telescope challenged this discovery, announcing in 2008 it had found 110 million stars making up two massive arms. Spitzer focused on infrared light emitted by the stars to makes its discovery.

The new study combined data from radio telescopes in the U.S., Australia and China on about 1,650 massive stars previously identified by the RMS Survey.

"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 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."

Lead study author Dr. James Urquhart, of the Max Planck Institute for Radio Astronomy in Bonn, Germany, said massive stars typically have shorter lifespans, which could cause a discrepancy in the number of arms presently visible.

"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," he said.

The massive stars are far less common than the younger ones and are only found in the arms in which they form.

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

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