UH scientists find better way to measure sun

HONOLULU — A team of scientists from Hawai‘i, Brazil and California has measured the diameter of the sun with unprecedented accuracy by using a spacecraft to time planet Mercury’s transits across the face of the sun in 2003 and 2006, the University of Hawai‘i reported Wednesday.

The team measured the sun’s radius as 432,687 miles with an uncertainty of only 40 miles.

“Transits of Mercury occur 12 to 13 times per century, so observations like this allow us to refine our understanding of the sun’s inner structure, and the connections between the sun’s output and Earth’s climate,” Jeff Kuhn, one of the UH scientists who was part of the team that measured the sun, stated in a news release.

The measurement was achieved by using the solar telescope aboard a NASA satellite, thereby bypassing the blurring caused by Earth’s atmosphere that occurs when observations are made from the ground.

The sun’s measurements were made by UH Manoa Institute for Astronomy scientists Marcelo Emilio (visiting from Ponta Grossa, Brazil), Kuhn and Isabelle Scholl, in collaboration with Rock Bush of Stanford University. They used the Michelson Doppler Imager aboard NASA’s Solar and Heliospheric Observatory to make the measurements.

The team is preparing to observe the transit of Venus across the sun on June 5. They expect these observations to improve the accuracy of their solar size measurement even further.

The scientists’ work was supported in part by NASA under a grant issued through the NASA Science Mission Directorate.

Visit www.ifa.hawaii.edu to view the scientific paper on the new measurements.

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