For Centuries, Man Has Yearned to Understand the Power of the Sun. Now Area Scientists Are Working to Harness It.
By Michael E. Ruane
Washington Post Staff Writer
Tuesday, June 19, 2007
Summer. Such an uncomplicated season. Winter's menace and spring's frenzy are over.
With calmer spirits, we emerge into the sunlight, relaxed enough to ponder mysteries of the universe.
This year's Metro summer series begins -- with the sun, of course.
It is a commonplace, fairly average, class-G star -- not as hot as the O- or B-class stars such as 10 Lacertra or Rigel, nor as cold as the class-M supergiant Antares.
But this star can affect the navigation of homing pigeons and the precision of oil drillers. Its mystery induced the ancients to cut out human hearts in sacrifice. And its light makes the daily 93 million-mile trip to Earth in about eight minutes.
Scientists across Washington are trying to simulate it, harness it and scrutinize it. Beachgoers bathe in it. By August -- or maybe this afternoon -- we'll be cursing it. And at 1:06 p.m. Thursday, its orientation in the sky officially begins summer.
It is our sun -- a giant seething irritable ball of nuclear fusion whose total energy output is so huge that a second's worth of it could meet U.S. power needs for 9 million years.
In religion, it is borne across the sky by the Navajo god Tsohanoai. It was Helios to the Greeks, riding his fiery chariot from dawn to dusk. And in the Bible, it was stopped in its tracks while Joshua slew the Amorites.
It rotates once every 25 days, regularly belching chunks of its insides into space or flinging out fountains of plasma called magnetic loops. It has an 11-year cycle, in which its storm activity ranges from what is called "solar minimum" to "solar maximum."
And it is the capricious source of space weather -- whose forecasting grows more vital as our technology grows more vulnerable.
With a core temperature of 27 million degrees Fahrenheit, the sun can warm and burn, cure and kill, nurture and destroy. One day a few eons from now, scientists believe it will expand and boil the Earth.
Until then, says NASA Goddard Space Flight Center astrophysicist W. Dean Pesnell, it's a great chance to analyze, and use, an actual star up close.
But not too close.
* * *
Scientists in Gaithersburg have built a large black aluminum sphere dubbed "the death star." It leaks a pale blue light on the third floor of Building 226 in the federal government's National Institute of Standards and Technology.
One could perish if trapped inside the sphere. Materials research engineer Joannie W. Chin, who helped build it, gets in every once in a while to clean it out, but only when the juice is off. There's an emergency red kill button in a clear box on a wall outside.
But the star -- technically the SPHERE, for simulated photodegradation by high-energy radiant exposure -- is seldom shut off. Using six powerful mercury lamps totaling 36,000 watts, the sphere simulates sunlight. Twenty-four hours a day. Seven days a week. For the past seven years.
Here, in Room B-349, the sun almost never sets.
The SPHERE "gives you the accelerated effects of the sun," Chin explained last week. "This device is 22 times the strength of the natural sun."
If you stuck your hand inside it, you'd get a bad sunburn. "You probably wouldn't want to do that," she said. "It wouldn't happen instantly." But if you burn on the beach in, say, half an hour, you'd burn in the sphere in a moment or two.
"It's the ultimate tanning booth," another NIST official said.
The sphere, about six feet across, was built to bombard things with ultraviolet light to see how well they hold up over time. The interior of the sphere is coated with a reflective Teflon-like material, Chin said.
One day exposed to the sphere's light is roughly akin to 35 days of normal exposure to the sun, said NIST research chemist Walter Eric Byrd.
The idea is to be able to quickly test plastics, coatings and the like without having to leave them out in the sun for weeks or months or years. "You don't want to wait 15 years to find out if your material will last 15 years," Chin said.
The sphere has been used to test such things as paint, sealant, caulk, the material in CDs, firefighters' coats, body armor and outdoor furniture. Of all things, body armor did not do well, Chin said. It was "highly susceptible to UV degradation, highly susceptible," she said. It can, however, be protected by a UV-resistant liner, she said.
UV light tends to be absorbed by certain things, such as plastics and human skin. When that happens, the light breaks molecules apart. "It actually physically takes the chemical bond and just slices it in half," Chin said. "That's how you get damage in your skin" and in plastics, which have similar chemical makeups, she said.
The sphere has a series of boxes attached to its exterior. Substances to be tested are placed in the boxes. The box doors are closed. Doors to the sphere are then opened, and the box fills with ultraviolet light.
Although NIST does not do product development, Chin said the sphere has been able to tell industry how long a given material will hold up in the sun.
Chin said that because UV is the most damaging part of sunlight, the sphere filters out almost everything else.
Indeed, Chin and Byrd said, sun light is an imprecise term for the complex spectrum of energy on Earth that is affected by a variety of weather and climate conditions.
"I don't like the word sun," Byrd said. "What's it mean? Is it 'sun' when it's cloudy?"
Chin agreed: Is it the kind sun you have in Miami? she asked. Or "the sun in Phoenix?"
"Exactly," Byrd said.
"We try to be more technical here at NIST," Chin said. Sun is "not a very NISTy kind of term."
* * *
Up on the building's sun-baked, white-gravel roof -- site of the agency's photovoltaic test facility -- A. Hunter Fanney is not so picky.
He embraces sunlight. In all its forms. As chief of the building environment division of NIST's Building and Fire Research Laboratory, Fanney has been studying the efficiency of solar energy devices for almost 30 years.
On his roof facility, he has solar panels, shingles, slates, slabs and modules arrayed like flowers in a garden.
Downstairs, in a huge, ground-floor bay, he keeps NIST's four-wheel solar tracking test bed, which can be loaded with solar arrays, towed outside and kept aimed directly at the sun throughout the day.
All this used to be for a niche market: things like calculators and solar-powered road signs, Fanney said last week. No more. With the largest portion of all greenhouse gas -- 37 percent -- now emitted in the production of energy for buildings, interest in solar power has soared, he said, and companies have long waiting lists for the purchase of solar panels.
He has seen the technology improve and the industry grow from one with companies run out of garages to one with the interest of giant corporations. "I think it's great," he said. "I think it's going to be one of the many ways that we help solve our energy situation. I'm excited about it. Absolutely."
Plus, it is now possible, under certain circumstances, for a solar-powered building to generate excess electricity that can be sold back to a utility, he said. And that has people's attention.
* * *
The sun has long had space scientists' attention at NASA's Goddard Space Flight Center in Greenbelt.
Goddard has a pair of new $43 million satellites that just started eyeballing the sun and another ready to be launched there in about two years.
Even though it's only a middle-of-the-road star, its proximity is tantalizing. The next closest stars are the Alpha Centauri trio, about 25 trillion miles away.
Stars are often classified in seven categories according to temperature -- O, B, A, F, G, K and M -- with O being relatively warm and M relatively cool.
The natural convulsions of our G-class star, caused by spasms of electrical activity, rise in frequency for 11 years and then fall for 11 more, creating so-called solar storms that hurl bursts of energy at the Earth.
Solar experts say those bursts can disrupt our magnetic field and affect navigation satellites, communications systems, spacewalking astronauts, oil drillers, homing pigeons and power grids.
In 1989, a solar storm's magnetic disruption knocked out power to 6 million people in Montreal for nine hours, according to the National Weather Service's Space Environment Center.
Pigeons, which rely on a stable magnetic field to navigate, can also be thrown off by such disruptions, scientists say, and sun storm radiation is potentially fatal to astronauts caught in the open.
In addition, pipelines can corrode faster when the magnetic field is altered, sun scientists say. And oil drillers who use Global Positioning System satellites to point their drills can be thrown off if the GPS satellites go haywire.
So, much of the new space science is aimed at forecasting those outbursts, which generate what is essentially space weather. And although space weather isn't yet headed for the evening news, it could be soon. Michael Kaiser, project scientist for NASA's twin STEREO sun satellites, said solar forecasters are about where hurricane experts were in the 1950s.
Currently, the forecast is for mild conditions on the sun. It's cycle is at "solar minimum," with about one solar storm eruption a day vs. five a day during "solar maximum," about a decade from now.
So if you've got pigeons, it's probably okay to let them out.
But do stay tuned.
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