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   Image courtesy of Daniel Huber

From: Daniel Huber
Mount Wilson Observatory, California, July 06, 2011

Measuring the sizes of Kepler stars

My name is Daniel, and I am an astronomer from the University of Sydney in Australia. I am currently on an observing run at Mt. Wilson observatory, which is located at roughly 6000 feet in the San Gabriel mountains north-east of Los Angeles, CA. Mt. Wilson is a historic observatory: on the picture in the background to the right you can see the dome of the famous 100-inch Hooker telescope, which was used by Edwin Hubble in the 1920's to discover the expansion of the universe.

For my observing run I am using telescopes such as the one just behind me on the picture. There are six identical telescopes like this on the mountain, and they are part of the Center for High Angular Resolution Astronomy (CHARA) array. Using a technique called interferometry we are observing stars with two or more telescopes simultaneously. By combining the light from different telescopes through vacuum pipes (one of which can be seen near the bottom right of the picture) we are able to reach resolutions as high as if we were observing with a telescope as large as the separation between them. Some of these telescopes stand up to 330 meters apart, enabling us to resolve objects which are up to 5 million times smaller than the apparent size of the moon in the sky! I am using the CHARA telescopes to measure the apparent sizes of stars observed by the Kepler mission. By combining these apparent sizes with the distance to the star, we can calculate their physical sizes which is a very important quantity to improve our understanding of stars.

Our observing run lasts for 5 nights, and our first four nights have already been very successful with great weather and plenty of good data! During the coming weeks I will be analyzing the data and discuss the results with colleagues in the US and in Europe, before heading back to Australia in September. It will be very exciting to see how our results compare with the data taken from the Kepler space telescope!

Postcards from the Observatory

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