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Fire threatens UCLA solar tower at Mount Wilson

UCLA astronomers are on fire watch today (August 31), hoping that firefighters can keep a huge wildfire that has already scorched more than 100,000 acres from destroying a 150-foot solar tower and computer equipment used by the scientists to measure the magnetic field at the sun's face. 

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Towercam view taken at 7:46 a.m. Tuesday, Sept. 1, from the top of UCLA's 150-foot solar tower at Mount Wilson.
UCLA's Physics and Astronomy Department's tower, which is topped by a complex of mirrors and lenses, is located at the Mount Wilson Observatory, a 40-acre complex of 50 to 60 buildings and the location for various research projects run separately by UCLA, UC Berkeley, USC, Caltech and Georgia Tech, among others. UCLA has been using a spectrometer, buried underground, to take daily magnetic field measurements of the sun's surface since 1970. The tower's central shaft allows sunlight to travel from the mirrors and lenses at the top to the instruments below. The tower itself has been used to measure solar activity continuously since 1912, when scientists recorded their observations by doing hand-drawings of sunspots and their magnetic fields.

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Photo of UCLA's 150-foot solar tower taken on a clear day.
Two UCLA staff observers, one of whom lives at the observatory complex, were evacuated Friday night, said Luca Bertello, who is the co-investigator on the research project, headed by Professor Emeritus Roger Ulrich and funded by NASA. Fire had already made the Angeles Crest Highway — the winding road that leads to Mount Wilson Road — nearly impassable in some sections, according to media reports. Firefighters were taken off the top of the mountain as the fire approached this morning. Aircraft dropped fire retardant over the entire site.

"Right now, the fire is still very unpredictable," Bertello said. "The risk is high, but so far, everything is all right." A webcam mounted on top of the tower has been taking photos that appear on a website every two minutes. Photos from the webcam have been used extensively by news media to get an aerial view of the smoke in the surrounding area and to follow the progression of the fire. Heavy web traffic has slowed the site considerably.
 
"I think it's probably one of the most popular websites in the country right now," said Ulrich. The camera, which gives UCLA astronomers information on weather conditions at the site, has been up for five or six years, and firefighters have used it before to obtain local fire information, he said.
 
"The situation is pretty scary," said Ulrich. "Currently, we're at some risk, but not a huge amount. If the fire gets into those big trees, though, we might have a crown fire." A crown fire occurs when fire reaches the canopy level of tall trees. A laboratory which houses computers and other equipment is located at the base of the tower. The intense heat from a crown fire could damage the building and melt the computers. "To get into the trees, the fire would have to come in from the north. Now it's coming in from the east." the astronomer said.
 
Built in 1910, the solar tower was the largest instrument of its kind until 1962. It has provided researchers with a valuable, unbroken record of solar activity for 87 years.

"Of course, everybody is anxious. But there's nothing we can do about it," Bertello said. "I try not to think about the consequences."

Also on Mount Wilson is an infrared spatial interferometer operated by UC Berkeley. It consists of three telescopes and measures stars at mid-infrared wavelenths with high angular resolution.

To see photos taken from the webcam on UCLA's 150-foot solar tower, go here. The most current scientific data from the tower can be viewed here.