![]() On one side of a galaxy’s spinning stellar disk, the stars swinging in the direction of Earth will show a spectral blueshift - the compression of light waves due to motion toward the observer. This shift is known as the Doppler Effect. Studying structure and rotation is much easier if you view a nearby galaxy from the outside.”įor the past century, astronomers have calculated galaxy rotation rates by observing a slight shift in the spectrum of its starlight. It’s all at different distances, and you’re sitting in the middle of it. ![]() “Studying the Milky Way is difficult because you’re studying from the inside, so everything you see is spread all over the sky. “The LMC is a very important galaxy because it is very near to our Milky Way,” said van der Marel, who is the lead author on a paper in the Feb. 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. 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. “Studying this nearby galaxy by tracking the stars’ movements gives us a better understanding of the internal structure of disk galaxies,” said Kallivayalil, “Knowing a galaxy’s rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass.”ĭisk-shaped galaxies such as the Milky Way and the LMC generally rotate like a carousel. Hubble recorded the stars’ slight movements during a seven-year period. used Hubble to measure the average motion of hundreds of individual stars in the LMC, located 170,000 light-years away. 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. It takes our sun the same amount of time to complete a rotation around the center of our Milky Way galaxy. Using the sharp-eyed NASA Hubble Space Telescope, astronomers have for the first time precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.Īccording to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years.
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