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Partial  eclipse
Noah Berger photo

Sky watchers see Sun turn to crescent of fire at Lawrence Hall of Science
11 June 2002

By Diane Ainsworth, Public Affairs

Sky watchers witnessed the Sun changing from a glowing marble to a radiant crescent of light yesterday during a two-hour partial eclipse that was seen from Borneo to Mexico.

The partial eclipse drew approximately 250 astronomy enthusiasts and nature lovers to the University's Lawrence Hall of Science, which overlooks San Francisco Bay. Some drove up from the South Bay to catch the light show, while others living nearby, in Berkeley, Orinda and Oakland, stopped by to enjoy the party and pick up free sunglasses and energy efficient light bulbs.

"Cool," said Forrest Lineburger, a Berkeley graduate, who drove up from Mountain View to watch the two-hour, four-minute eclipse. "It makes you feel miniscule."

  Eclipse viewer
Mavees Ahlborn uses "Eclipse Shades" to view the solar eclipse from the Berkeley hills.   Noah Berger Photo

"This is a rare and beautiful show that nature is putting on for us," said Toshi Komatsu, assistant director of the Hall of Science Planetarium. "You get a solar eclipse maybe twice a year, but you may not be in the right place to see it, so any kind of an eclipse is always a treat."

Astronomer Alan Gould of the Lawrence Hall of Science set up a powerful refractor telescope with 40 times the magnification and an eclipse filter for public viewing. A less powerful reflector telescope with about 20 times the magnification also drew lines of people waiting to get a glimpse of the Moon as it slid in front of the Sun.

"It's great to remind people that the Moon is actually moving," he said. "We know it orbits, but a lot of times we don't really realize that until we see it."

At the peak of the eclipse, which occurred at 6:16 p.m. Pacific time, the Moon had blocked out about 70 percent of the Sun's surface.

Few sunspots

Three dark sunspots, each as big as Earth, were visible in the southern hemisphere of the Sun. Sunspots are dark, cooler regions of the solar atmosphere with intense magnetic fields that choke off heat and energy flowing outward from the Sun's interior, Komatsu said. This keeps them thousands of degrees cooler than the turbulent gas around them.

Sun Facts:

- The Sun is 92 percent hydrogen, 8 percent helium.

- About 100 times the diameter of Earth, or 109 times Earth's radius, and 333,000 times Earth's mass.

- 15.5 billion Kelvin at its center, hot enough for fusion to occur.

- only 70 percent as luminous at birth 4.5 billion years ago.

- steady brightening is caused by increasing amounts of helium accumulating in the Sun's core.

- today the Sun's surface is 300 K hotter and its radius is six percent greater than it was 4.5 billion years ago.

- the UV rays that are most intensive during solar maximum do not cause sunburns; most of the UV rays causing sunburns are blocked by ozone.

- three billion years from now, the Sun will be hot enough to boil away Earth's oceans, leaving our planet a burned-out cinder; life on Earth will end.

- seven billion years from now, the Sun will run out of hydrogen and balloon into a giant star, engulfing the planet Mercury and becoming 2,000 times brighter than it is now.

Normally they appear in pairs of opposite magnetic polarity, joined by loops of magnetic field lines that rise into the overlying solar atmosphere, Komatsu explained. There are far fewer to freckle the Sun's face right now than there were earlier in the year because the height of the Sun's activity has subsided.

"We would probably see twice as many sunspots during solar maximum," Komatsu said. "The ones we see today look something like a chain of islands."

Michele Hubinger, a resident of Orinda, asked her four-and-a-half year old son, Evan, to explain the eclipse. "It's the moon on top of the Sun," he exclaimed in no uncertain terms. Hubinger has been following eclipses ever since the late 1960s, when her father took her to watch a total solar eclipse in Pennsylvania and ignited her curiosity.

"I remember that eclipse," she said, gazing skyward with her special solar-viewing shades. "The temperature dropped considerably and it turned from daylight to utter darkness."

During a total eclipse, the sun's fiery atmosphere looks like a halo of light. "We can study fine structure and detail in the corona during a total eclipse, because the brightest part of the Sun is blocked out," Gould said. "The corona is about 1 million degrees Kelvin and radiates out millions of kilometers, producing the solar wind."

Northern, southern lights

These gales of ionized matter blow at speeds of 1.6 million miles per hour from higher latitudes above the Sun's equator and have been known to disrupt power grids and telecommunications when they collide with Earth's upper atmosphere. They also are responsible for the shimmering northern and southern auroras.

Flares, loops and prominences all create a "magnetic carpet" over the Sun's surface and are the subject of several international space science missions, including RHESSI, a NASA/UC Berkeley satellite launched on Feb. 5, 2002. Solar physicists are using the RHESSI spacecraft to image flares in x-ray wavelengths as they tear away from the Sun's corona. Flares are thought to signal the release of tremendous amounts of magnetic energy, like a tightly twisted rubber band that suddenly snaps.

Scientists will learn more about flares and other solar eruptions during the next total solar eclipse, which will be visible on Dec. 4 in Africa and Australia.