* Astronomy

RHESSI Will Use Venus Transit to Improve Measurements of the Sun's Diameter

The RHESSI (Ramaty High Energy Solar Spectroscopic Imager) satellite focuses on the highest energy x-rays and gamma-rays produced by the sun, helping to observe solar flares of all shapes and sizes. The satellite is pointed toward the sun, and constantly in rotation, which provides a serendipitous bit of side research: by monitoring the limb of the sun on its four second rotation cycle, RHESSI's Solar Aspect System (SAS) has produced ten years worth of precise measurements of the sun's diameter. This has already provided scientists with one of the most accurate measurements of what's called the oblateness of the sun, which is the difference between the diameter from pole to pole and the equatorial diameter. With the new data obtained during the Venus Transit on June 5-6, 2012, the RHESSI team hopes to improve the knowledge of the exact shape of the sun and provide a more accurate measure of the diameter than has previously been obtained., and the event that really put the issue on the global political agenda.
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