NASA’s Hubble Space Telescope have been utilized by the astronomers to accurately measure the rotation rate of a galaxy for the first time, based on the clock-like movement of its stars.
The study showed that the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), finishes a rotation every 250 million years, same as the time taken by our sun to complete a rotation around the center of our Milky Way galaxy.
Hubble determined the average motion of hundreds of individual stars in the LMC, positioned 170,000 light-years away. The telescope documented the stars’ minor motions over a seven-year period.
“By using Hubble to study the stars’ motions over several years, we can actually, for the first time, see a galaxy rotate in the plane of the sky,” noted lead author Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Maryland.
Scientists said that disk-shaped galaxies, like the LMC, naturally rotate like a carousel. Hubble’s abilities endow with a new technique to measure a galaxy’s rotation by the “sideways” proper motion of its stars, as seen in the plane of sky.
The Hubble Telescope orbits the earth’s atmosphere taking extremely high resolution pictures with high image stability making it the only telescope of its kind. The telescope sent to space in 1990 presents scientists with essential research data by the means of images it takes. NASA’s telescope is expected to remain in orbit and function until possibly the year 2020.
“If we imagine a human on the moon, Hubble’s precision would allow us to determine the speed at which the person’s hair grows,” van der Marel explained. “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.”
“Studying this nearby galaxy by tracking the stars’ movements gives us a better understanding of the internal structure of disk galaxies,” said co-author Nitya Kallivayalil of the University of Virginia. “Knowing a galaxy’s rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass.”
Earlier astronomers have determined galaxy rotation rates with the help of measurement of the Doppler motions of the galaxy’s starlight.
The combination of the Hubble sideways motions and the Doppler motions, was a full 3-D view of stellar motions in another galaxy, developed by the astronomers.
The findings were published in the Astrophysical Journal.