Hubble measures rotation rate of galaxy 170,000 light-years away

NASA's Hubble Space Telescope has for the first time helped astronomers precisely measure the rotation rate of a galaxy based on the clock-like movement of its stars.

According to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years.

It takes our sun the same amount of time to complete a rotation around the center of our Milky Way galaxy.

The Hubble team-Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Md., and Nitya Kallivayalil of the University of Virginia in Charlottesville, Va.-used Hubble to measure the average motion of hundreds of individual stars in the LMC, located 170,000 light-years away. Hubble recorded the stars' slight movements during a seven-year period.

"Studying this nearby galaxy by tracking the stars' movements gives us a better understanding of the internal structure of disk galaxies," Kallivayalil said.

"Knowing a galaxy's rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass," the researcher said.

Disk-shaped galaxies such as the Milky Way and the LMC generally rotate like a carousel. Hubble's precision tracking offers a new way to determine a galaxy's rotation by the "sideways" proper motion of its stars, as seen in the plane of the sky.

Astronomers have long measured the sideways motions of nearby celestial objects, but this is the first time the precision has become sufficient to see another distant galaxy rotate.

The research is published in the Astrophysical Journal.