A sadhu tries his goggles. Picture by Pabitra Das

New Delhi, July 21: Four astronomers will fly in an air force plane over northern India and a larger group will use a hillside in eastern China early Wednesday to steal science attainable only from the beauty of the moon hiding the sun.

A team of four scientists from the Udaipur Solar Observatory will fly in an Indian Air Force AN-32 transport aircraft and climb above the clouds to seek an unobstructed view of the July 22 solar spectacle, the longest total solar eclipse of the 21st century.

The AN-32 will take off from Agra, fly towards Khajuraho and enter the belt-shaped region of totality that stretches in India from Surat to Patna and beyond. “Monsoon clouds threaten to block the view from the ground over most parts of India,” said Shibu Mathew, a scientist from the Udaipur Solar Observatory. “High in the sky, may be able to avoid clouds,” he said.

But a trial flight into the eclipse belt early this morning didn’t look too promising, scientists said. The plane climbed up to 25,000 feet but patches of cloud persisted. “They were not ideal conditions, but we are hoping for better conditions tomorrow morning,” said P. Venkatkrishnan, director of the Udaipur Observatory.

The total solar eclipse caused by the moon’s shadow moving across the Earth many times faster than the speed of sound will begin at 6.23am in the Gulf of Cambay and pass over Surat, Indore, Bhopal, Varanasi and Patna and Arunachal Pradesh before heading into China and beyond along a path that curves over the Pacific Ocean.

Eclipse observers in India will have two disadvantages — the sun will hang low above the horizon so early in the morning and clouds may frustrate attempts to view the event.

An analysis by the US National Aeronautics and Space Administration suggests that Patna with 48 per cent sunshine is the best place to watch the eclipse in India.

But clouds aren’t expected to be a problem at Anji, a hillside near Hangzhou in eastern China where 16 astronomers from India have joined scientists from the US, Europe and Asia for a clearer and longer view of the eclipse.

Satellites and space-based telescopes now provide enormous data about the sun, but there are some observations that can be done only during a total solar eclipse, Venkatkrishnan told The Telegraph.

Scientists say the beauty of the total solar eclipse allows them to capture images of the corona — the superhot material around the sun — whose high temperature is an unresolved solar mystery. At other times it is not easy to study the corona because of the sun's brightness.

“There’s this big puzzle about the corona that has yet to be resolved,” said Harish Bhat, dean at the Indian Institute of Astrophysics, Bangalore. The temperature of the surface of the sun is about 6000°C, but the temperature of the corona is more than a million°C.

Scientists know that magnetic fields somehow contribute to the corona’s high temperature. “During an eclipse, we’re trying to get observations that will help us understand the mechanism of this heating,” said Venkatkrishnan.

While the totality interval -- the period during which the moon completely blocks the solar orb — in India will last about 3 minutes, the period of totality in Anji will last for 5 minutes 38 seconds.

“We’ve got a favourable forecast and we’re hopeful of seeing the eclipse clearly," Siraj Hasan, director of the Indian Institute of Astrophysics, Bangalore, told The Telegraph tonight from Anji.

This patch of land the size of a football field in eastern China will at dawn on Wednesday turn into the world’s busiest solar observatory. Anji is also hosting scientists from Udaipur and another Indian observatory. It has also drawn scientists from Azerbaijan, France, South Korea and the US — in addition to Chinese teams.