Twinkle Twinkle Little Star
Published on 15 Apr 2007 at 11:03 pm.
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Filed under Astronomy, Photography, Space.
The Astronomy Picture of the Day came as quite a surprise to me. It shows a movie made by J. Hartman of the Harvard-Smithsonian Center for Astrophysics and J. Stanek of Ohio State University of a Globular Cluster of stars, many of which are RR Lyrae stars. These stars fluctuate in brightness over a manner of hours! The stars in this image are not twinkling because of the usual fluctuations in our atmosphere. They are actually changing brightness! The gif below is reduced in size, please click on it for a bigger image or visit APOD to see it in all its glory.
Globular Clusters are swarming clusters of stars all in orbit around each other. The orbital periods are long (~100,000 years) because the sizes of these clusters are vast.
RR Lyrae stars are relatively small stars with masses less than the mass of our Sun. They are old stars and are running out of Hydrogen fuel in their cores. This causes them to pulsate rather than shine at a relatively steady rate like our Sun. These variations in luminosity allow astronomers to accurately estimate their distances. For this reason RR Lyrae stars are important for measuring distances in the galaxy.
Kevin Knuth
Albany NY
