New perch for a telescope

Supersize balloons are lifting scientists' sights, allowing them to see farther into space.

By Faye Flam
Inquirer Staff Writer

To get the clearest possible view of the heavens you need to get above Earth's atmosphere, but you don't necessarily have to get there by space shuttle.

Last month an international collaboration led by the University of Pennsylvania lofted a telescope to the edge of outer space on an enormous balloon. As it flew from Sweden to western Canada, it observed dusty regions where new stars are being born millions of light years away. That may help explain how stars and planets are formed from stardust.
Reaching a height of 125,000 feet, it got above at least 98 percent of the atmosphere, says Mark Devlin, an astronomy professor at Penn. That's four times the height of an intercontinental jet.
"We're basically in space - the sky is black," says meteorologist Danny Ball, manager of National Scientific Balloon Facility in Palestine, Texas.
These are not ordinary balloons. They're as big as the Houston Astrodome, with 25 to 30 miles of seams and 25 acres of material. A Texas company called Aerostar makes them.
Astronomers have sent telescopes and other detectors up by balloon since the 1960s. Balloon-borne instruments observe the sky in different wavelengths, examine atmospheric chemistry, and in some early missions, sent astronauts up to check out the effects of very high altitudes on the human body.
The National Scientific Balloon Facility launches 15 to 20 balloons a year from various outposts - Sweden, South America, Canada, Australia and Antarctica. The longest flight took 42 days and made three complete circles around Antarctica.
The Penn-led ballooning project, called BLAST (Balloon-borne Large-Aperture Sub-millimeter Telescope), makes its observations not in visible light but in a wavelength between infrared and radio waves. By looking in that range, the researchers hoped to see stardust glowing with the nascent stars as well as whole galaxies too hazy to show up in visible light.
Our eyes are tuned to a narrow band of light wavelengths - the visible range - but the universe shines in a much larger spectrum. Radio waves, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays each reveal a different range of phenomena - a different face of the universe.
Just as X-rays show the bones in the human body, sub-millimeter telescopes can penetrate otherwise opaque, dusty galaxies, says Gary Melnick of the Harvard-Smithsonian Center for Astrophysics. Regions that look bright in the sub-millimeter range, he says, often look black to an optical telescope.
Sub-millimeter waves can also penetrate to the very core of young star-forming regions in our own galaxy, he says. Water and other molecules that mix with that stardust also radiate light in this range. "We believe these are important for forming planets and perhaps forming life."
"It's relatively uncharted territory," says Devlin, the project leader.
In recent years, satellites designed to map the universe in the somewhat longer-wavelength microwaves range have picked up a diffuse glow or noise in the sub-millimeter range. But those satellites couldn't pinpoint them, he says. BLAST is the first flying telescope designed to discern individual sources of this glow.
BLAST was designed to look both within our own galaxy and far beyond. Because of the long time it takes light to reach us from distant galaxies, we see them as they looked long ago - when they were in a more primitive phase.
These "younger" galaxies are still in the process of making most of their stars. They have fewer stars and more stardust, which shows up better in the sub-millimeter range than in the visible.
Caltech astronomer Thomas Phillips, considered one of the founders of sub-millimeter astronomy, says many galaxies that look dim or invisible in ordinary light glow brightly in the sub-millimeter range. Some of that glow may come from stars forming, but some may also come from stars dying as they get pulled into massive black holes.
Flying on a balloon gives you a better perspective for a short time but it takes guts, he says, to build a multimillion dollar instrument and send it up on something that's still subject to the vagaries of wind and weather.
The BLAST project started in 2000 as the international team started building the payload - a 6-foot-diameter telescope almost as wide as that flown on the Hubble. The apparatus stands 25 feet high and weighs two tons. Devlin and his colleagues assembled much of it in the Left Bank Building in West Philadelphia. They test-flew it from Texas in 2003 and then, last spring, launched it from Kiruna, a small town in northern Sweden.
They flew in June because of the 24-hour daylight above the Arctic Circle that time of year. The temperature swings associated with a normal day-night cycle would have caused the balloon to rise and fall, says Devlin, which would complicate their mission.
It helps that winds in the stratosphere blow more predictably than those closer to the ground - going reliably westward in the spring. They couldn't fly over Russia, says Devlin, because the Russians don't allow research balloons over their territory. So they planned to cause the balloon to fall by remote control when it reached western Canada.
One of their primary fears was losing the telescope in the ocean. After four days they were as close to water as they dared get and so they let the balloon fall over Victoria Island in northwestern Canada.
A NASA plane flew Devlin and colleague Jeff Klein to Victoria Island, where it was snowing hard. By then the telescope had landed in the empty tundra. They caught up with it by helicopter.
The landing had broken the mirror, but Devlin says he was thrilled that the payload landed more or less intact and they got good data on regions inside our galaxy. Because their run was so short it didn't deliver hoped-for observations of distant galaxies, he says.
For the next few months the team will re-assemble BLAST for a second flight, planned for December 2006. They will try to go around the periphery of Antarctica for about 14 days, looking for galaxies whose light began to travel to us seven billion years ago.
"That's where a lot of interesting stuff is going on."