Anticipation heats up for rare solar eclipse

This summer, darkness will fall across the face of America. Birds will stop singing. Temperatures will drop. Stars will become visible in the daytime sky.

A total solar eclipse occurs somewhere on Earth about once every 18 months, and it can happen absolutely anywhere.

On Aug. 21, however, what’s known as the path of totality will cut a 60-mile-wide arc across the United States, beginning in Oregon at 10:15 a.m. local time and ending in South Carolina about an hour and a half later. Astronomers are calling it the Great American Eclipse. Researchers have been anticipating the event for years.

Jay Pasachoff, an astronomer at Williams College in Massachusetts who has seen 33 total eclipses and 32 partial eclipses, said that during a total solar eclipse, the moon completely obscures the face of the sun, causing the daytime sky to darken by a factor of 1 million.

“It’s a really unique feeling, standing in the shadow of the moon,” said Matt Penn, an astronomer at the National Solar Observatory in Tucson. “Crickets start to chirp. Birds start to roost. Chickens do weird things. And it’s all in reaction to the strange light.”

Penn said his team’s focus will be to measure the velocity of the solar wind, the outflow of particles coming from the sun.

“These particles are accelerated at high speeds, but we don’t know how that acceleration works,” he said.

Most researchers plan to study the sun’s outer atmosphere, or corona — a complex swirl of gases much hotter than what you’d find on the surface of the sun.

“The fundamental question we are asking is, what is causing the atmosphere to heat up like that?” said Shadia Habbal, of the University of Hawaii’s Institute for Astronomy. “This is one of the scientific mysteries regarding the sun that remains unanswered.”

On the other side of the country, researchers from the Harvard-Smithsonian Center for Astrophysics are planning to study the corona from a plane flying at 49,000 feet.

The group, led by solar physicist Ed DeLuca, is building an instrument that will allow them to examine the solar atmosphere in infrared wavelengths. Their ultimate goal is to better understand the magnetic fields that hold the corona in place.