The NASA Hubble Space Telescope has measured, for the first time, the rotation rate of a galaxy, one whose stars have clockwork-like movement. The galaxy is the Large Magellanic Cloud, or LMC, and the NASA Hubble Space Telescope has determined by the movement of its stars in the central part of the galaxy that 250 million years is how long it would take the Large Magellanic Cloud to make a single rotation, according to the Space Telescope Science Institute.
250 million years is also approximately how long it takes for the sun to make a complete rotation around the center of our Milky Way Galaxy.
Two of the Institute’s scientists, Nitya Kallivayalil and Roeland van der Marel, were behind the idea of using the NASA Hubble Space Telescope to measure the rate of rotation of the Large Magellanic Cloud (LMC), 170,000 light-years away from us.
The LMC, like the Milky Way, are both disk-shaped galaxies, and that type of galaxy generally rotates like a wheel or tire of a car.
According to van der Marel, using the NASA Hubble Space Telescope to study the movements of the stars within the LMC over several years, they could then see for the first time “a galaxy rotate in the plane of the sky.”
What makes the NASA Hubble Space Telescope the only one capable of making such observations?
There are various reasons, according to the two Institute scientists, why the NASA Hubble Space Telescope is currently the only telescope capable of making such observations as the rotation of an entire galaxy.
One of the main reasons is the very longevity that the Hubble Space Telescope has been in existence in space — 24 years. It’s the only telescope in space that has been around fr enough years to then extrapolate how a galaxy moves over millions and billions of years. Also crucial is the fact that it’s the only telescope in space that has a sharp enough resolution and which can take stable enough images to accurately document the movement of a galaxy.
The rotation of a galaxy like the LMC is so slow and the movements are so small that, as van der Marel says, like the hands of an extremely slow clock, even using the NASA Hubble Space Telescope, “we need to stare at them for several years to see any movement.”
In the past, astronomers have attempted to measure the rate at which a galaxy rotates through analyzing minor shifts in the spectrum of the light from its stars. The stars rotating in the direction towards Earth show a blue shift in the light spectrum, while the stars which rotate away from Earth on the other side of a disk-shaped galaxy like the LMC will demonstrate a spectral redshift.
However, the two Institute researchers have discovered that the use of the NASA Hubble Space Telescope has provided them with a much more precise method of determining the speed of a galaxy’s rotation. This is because the method involving analyzing the shifts in the spectrum of light, according to Roeland van der Marel, “doesn’t allow one to actually see things change over time.”
The researcher van der Marel said that the precision of the observations that the NASA Hubble Space Telescope made of the rotation of the stars within the LMC galaxy would be similar to looking through the telescope at a human on the surface of the moon and being able to measure “the speed at which the person’s hair grows.”
The NASA Hubble Space Telescope has been extremely useful to a large number of researchers and scientists, and it now has made it possible to accurately measure the rate of speed at which an entire galaxy rotates, namely, the Large Magellanic Galaxy.
Written by: Douglas Cobb