U.S. astronomers solve 45-year-old puzzle

BALTIMORE, April 10 (UPI) -- The European Space Agency said U.S. astronomers might have solved a 45-year-old mystery involving two ghostly spiral arms in the galaxy M106.

A team of astronomers from the University of Maryland took advantage of the unique capabilities of the ESA's XMM-Newton X-ray observatory, the National Aeronautics and Space Administration's Chandra X-ray Observatory and NASA's Spitzer Space Telescope.

M106, also known as NGC 4258, is a spiral galaxy 23.5 million light-years from Earth in the constellation Canes Venatici. In visible-light images, two prominent arms emanate from the bright nucleus and spiral outward. Those arms are dominated by young, bright stars, which light up the gas within the arms.

"But in radio and X-ray images, two additional spiral arms dominate the picture, appearing as ghostly apparitions between the main arms," said team member Andrew Wilson.

By analyzing data from XMM-Newton, Spitzer, and Chandra, the team in Maryland confirmed suspicions that the ghostly arms represent regions of gas that are being violently heated by shock waves.

The research -- prepared by lead author Yuxuan Yang -- is to appear in the May 10 issue of the Astrophysical Journal.