Zee Media Bureau/Liji Varghese
New Delhi: Astronomers for the first time have precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.
The team used NASA`s Hubble Space Telescope to measure the average motion of hundreds of individual stars in the central part of the neighbouring galaxy, called the Large Magellanic Cloud (LMC). Hubble recorded the slight movements of the stars over a period of seven-years.
The team found that LMC completes a rotation every 250 million years – approximately the same amount of time taken by the Sun to complete a rotation around the centre of our Milky Way galaxy.
They used Hubble`s Wide Field Camera 3 and Advanced Camera for surveys to observe stars in 22 fields spread across the vast disk of the LMC, which appears in the southern night sky as an object about 20 times the diameter of the moon.
LMC also a disk-shaped galaxy just like ours, rotates like a carousel and is one of the Milky Way`s nearest neighbours, located about 170,000 light-years away.
"Studying this nearby galaxy by tracking the stars` movements gives us a better understanding of the internal structure of disk galaxies," study co-author Nitya Kallivayalil, of the University of Virginia, said.
"Knowing a galaxy`s rotation rate offers insight into how a galaxy has formed, and it can be used to calculate its mass," the researcher added.
Hubble`s precision tracking offers a new way to determine a galaxy`s rotation by the "sideways" motion of its stars, as seen in the plane of the sky. For long, astronomers have been able to measure the sideways motions of nearby celestial objects, but this is for the first time that the precision has become sufficient to see another distant galaxy rotate.
"This precision is crucial, because the apparent stellar motions are so small because of the galaxy`s distance. You can think of the LMC as a clock in the sky, on which the hands take 250 million years to make one revolution. We know the clock`s hands move, but even with Hubble we need to stare at them for several years to see any movement, " lead author Roeland van der Marel, of the Space Telescope Science Institute in Baltimore, said.
The study was published on February 1 issue of the Astrophysical Journal.
Image Credit: NASA/ESA