mountain profile Institute for Astronomy University of Hawaii

The Sun

Maintained by LG

Solar Eclipses

During the last few years Shadia Habbal has organized several expeditions to observe total solar eclipses. These events offer rare opportunities to study the solar corona — the region of hot gas that is the source of the solar wind that strongly affectsconditions in the upper atmosphere of the Earth.

By acquiring simultaneous images of iron atoms at different levels of excitation, Habbal and her colleagues established for the first time that





An overlay of white light, Fe XIV 530.3 nm (green), and Fe XI 789.2 nm (red) emission from observations taken during the total solar eclipse of 1 August 2008.







The Diameter of the Sun

Jeff Kuhn is a member of an international team which has recently measured the diameter of the Sun with unprecedented accuracy.

The used the SOHO spacecraft to time the transits of the planet Mercury across the face of the Sun in 2003 and 2006.
They measured the Sun’s radius as 696,342 km (432,687 miles) with an uncertainty of only 65 km (40 miles).

Transits of Mercury occur 12-13 times per century providing astronomers with the opportunity to look for very small changes in the Sun's diameter over the next few decades.


Mercury's path across the solar disk as seen from NASA's Solar and Heliospheric Observatory on November 8, 2006.