Listen Here, Sunny Boy, We Owe You a Lot

AS THE SUN RISES

TEXT AND PHOTOGRAPHS BY GARY LADD It's midday and I'm standing on the floor of southern Arizona's Sonoran Desert. Despite the beauty of the surrounding landscape, one sensation dominates: heat. The intensity of the sun bakes my head and shoulders, ricochets off the sandy ground and forces distant mountains to ripple like banners.

Visitors from around the world come to Arizona to experience the mild temperatures, usually in winter when the sun appears lower in the southern sky. Golfers, hikers and outdoor people of diverse interests soak up our sunlight. Our generally cloudless skies, dry air, continental position, latitude, longitude and elevation modulate the sun's rays, branding them as uniquely Arizona's.

The sun drives our agriculture, nourishes our forests and cacti, warms our atmosphere and literally makes our lives possible.

How is it that a bright spot in the sky could do all of this? What exactly is the nature of that thing that blazes with such intensity that I can't bring myself to look at it?

To answer those questions, I get back inside my air-conditioned car, pull onto State Route 86 heading southwest from Tucson, and continue toward the National Solar Observatory on Kitt Peak. I've made arrangements to spend two days with Dr. Bill Livingston, a solar astronomer. On the mountaintop at an elevation of nearly 7,000 feet, the air temperature is 20 degrees cooler. Here, among the world's largest col-lection of optical telescopes, I'll find some answers to my questions about the Arizona sun, an object so obvious and dependable that most of us never begin to appreciate it. But Livingston does. From the mountaintop, two or three days a month, he keeps an eye on it.

Livingston usually studies the sun using Kitt Peak's McMath-Pierce Solar Telescope-an angular, white 100-foot-high structure with a massive slanted shaft that funnels sunlight into a chamber carved from the mountain's bedrock.

The main observing room is a rectangular, underground space with a high ceiling perforated by several openings, or portals. Any of the por-tals can direct light from the telescope downward through the observ-ing room into spectographs below floor level. Beneath other portals, mirrors can reflect beams into still other instruments. Livingston uses the main spectrograph, an instrument that breaks light into its various colors.

As a brilliant beam of sunlight, 30 inches in diameter, splashes across the room, an image of the sun comes into focus on the spectrograph for Livingston, wearing sunglasses, to examine. Today's solar disk is relatively dull with only a few small sunspots scattered across its glowing face.

"This side of the sun is pretty uninspiring today," he says. "The far side is more active." He knows this, he says, because he observed a larger collection of spots a few days earlier before the sun's rotation carried them from view. Dark features that sometimes appear on the sun's surface, sunspots are sites of strong magnetic fields generated in the sun's interior.

Our sun, which astronomers believe is about halfway through its estimated 10-billion-year lifetime, converts gigantic amounts of one element into another. Every second, astronomers have discovered, 700 million tons of hydrogen are transformed by nuclear fusion into helium. The helium, however, weighs 5 million tons less than the initial hydrogen. The mass lost in the fusion process becomes electromagnetic energy, as expressed in Einstein's equation, E=mc², which we on Earth eventually sense as visible light. Earth, at a distance of 93 million miles, catches only about half of a billionth of the sun's gigantic energy output.

Livingston, in his quest to learn about the sun, has traveled to the far reaches of our planet to observe the sun in total eclipse a dozen times, and the sky was clear each time. Typically only during a total solar eclipse can the sun's outer atmosphere, the corona, be examined in detail.

As one of his long-term projects, Livingston has observed the sun for nearly 30 years using the same instrumentation specifically designed for detecting solar temperature changes that might affect global warming on Earth. So far he says he has detected no significant changes. He and other astronomers suspect, however, that the sun is subject to periods of variability that could affect Earth's climate.

The McMath-Pierce Solar Telescope is the largest on Earth. The National Solar Observatory also operates telescopes at Sacramento Peak, New Mexico, and the Global Oscillation Network Group (the “GONG”) with its instruments located across the world. Livingston's observations end in the late afternoon. After dinner, he and visiting astronomer Roland Carpenter and I gather in the observing room solely for the pleasure of watching the sunset projected onto a square of white cardboard. As we look and chat, the disk of the sun sinks through a distant cloud, flattening and reddening as it nears the horizon. The flattening is an effect of light-refraction of the atmosphere, the reddening an effect of dust in the air. We watch until the last glint of orange light blinks out beyond distant mountains. An hour later, before heading to the dormitory, I look up into the night sky. Up there, far beyond our solar system, I can see an extravagance of other stars, a couple thousand of them. Astronomers have found that unlike our sun, most of these stars are members of multiple systems with two or three stars orbiting their common center of mass. Each star sheds light across an otherwise inky emptiness. As I gaze upward, it reminds me of a nighttime view across a large, forbidding lake to the twinkling, friendly lights of human civilization along distant shores. When I mosey around the dark summit of Kitt Peak (wary of hostile rattlesnakes), it's easy to appreciate how lucky we are to live on a planet of just the right size at just the right distance from a dependable star of just the right type. The next morning, Livingston opens the telescope soon after sunrise. He and Carpenter go back to their observations. Livingston's 30 years of monitoring the sun seem rather epic. But on astronomical scales, the time is insignificant. Most stars blaze for billions of years. According to stellar evolution models, in about 3 billion years our sun will begin to bloat outward as its hydrogen supply dwindles, becoming a giant red star and rendering Earth hot enough that its mountains will sag into oblivion. Then, 2 billion or 3 billion years after that, the sun will collapse into a white dwarf star glowing dimly as it heads to the end of its existence.

I ask Livingston how he might generally characterize the sun. “More than anything, it's constant. Very constant,” he says. There is a cycle during which the sun displays frequent sunspots, then decreases to only a few, then frequent again on a schedule of about every 11 years. “But those changes are rather superficial,” he explains. The last sunspot maximum occurred in 2001. It's not surprising that the sun is so stable. Its size alone suggests stability. The diameter of the sun, although tiny compared to the truly giant stars, is much larger than the diameter of the moon's orbit around the Earth. More than a million Earths could fit inside the volume of the sun. Scientists believe that “the sun is. very slowly getting brighter,” Livingston says. Though the brightening is not detectable, scientists have formed this belief through theory and by observing other stars.

At the end of the afternoon's observations, Livingston's giant mirror rotates into its stowed position. The blinding white light from our Arizona sun that has flooded into the observing room all day is suddenly extinguished. Only the dreary, green glow of the fluorescent light fixtures remains to usher us out of the room.

We often whine about the heat of our summers in Arizona. But without that fabulous sun star, none of us would be here to complain. All In the 1970s, Gary Ladd worked as a research assistant at Kitt Peak National Observatory and at Mount Hopkins Observatory south of Tucson. He now lives in Page.

LOCATION: Kitt Peak is approximately 56 miles southwest of Tucson. GETTING THERE: From Tucson, drive south on Interstate 10 to Interstate 19. Follow I-19 about 1 mile to Ajo Way (State Route 86). Turn west (right). Follow State 86 west past Three Points to State Route 386, the Kitt Peak turnoff. Turn left onto State 386 and drive 12 miles to the visitors center at the summit of Kitt Peak. HOURS: Daily, 9 A.M. to 3:45 P.M.; closed Thanksgiving, Christmas and New Year's Day. FEES: Suggested donation of $2 per person for visitors center admission and self-guided tours. Guided tour fees: $2 adult, $1 children 6-12. ATTRACTIONS: Visitors center, one-hour guided tours, self-guided tours and picnic area. Reservations are not required for day use. Nightly Observing Programs and Advanced Observing Programs are available by reservation only. TRAVEL ADVISORY: At an elevation of 6,880 feet, care should be exercised by those with cardiac or respiratory problems. Dress warmly in winter. ADDITIONAL INFORMATION: (520) 318-8200 or (520) 318-8726; www.noao.edu.