Monday, January 21, 2008

How Far the Stars?

Here's the open star cluster known as M45 or the Pleiades. This image is a composite from two black and white images taken with the Palomar Observatory's 48-inch (1.2-meter) Samuel Oschin Telescope as a part of the Second Palomar Observatory Sky Survey (POSS II). The images were recorded on two glass photographic plates - one sensitive to red light and the other to blue. The plates were scanned and color combined to produce the image seen here.

The cluster is easily seen this time of year with no optical aid needed at all.

Four yeas ago today astronomers announced a revised distance estimate to the star known as Atlas within the Pleiades star cluster using data gathered by the Palomar Testbed Interferometer. Atlas, according to the findings, is 440 (+/- 6) light-years distant.

The distance measurement was in disagreement with the results obtained by the Hipparcos Space Astrometry Mission, which placed the cluster some 10% closer than other measurements. The Pleiades is the second closest star cluster to our solar system. Having an accurate distance to the closest star clusters is very important as they are used as stepping stones to all the rest.

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