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April 13, 2006


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HARVARD GAZETTE ARCHIVES

aurora over station
The aurora australis snakes across the South Pole sky in 2002 in displays whose beauty awed researchers spending the winter there. (Photo courtesy of the U.S. Antarctic Program)

'Wintering-over' at the South Pole

Solitude, beauty, discovery

By Alvin Powell
Harvard News Office

They came to the South Pole, enduring months of bitter cold, darkness, and isolation, to peer at the galaxy's center through clear, dry skies.

They found unexpected beauty in shimmering auroras dancing above them, solace in work that probed the mysteries of the universe, and companionship in the people around them, with whom they joined the informal brotherhood of those who had wintered-over at the South Pole.

Harnett
Jules Harnett, a winter-over scientist, prepares for the elements - in typical winter headgear with no skin showing - in June 2004. (Photo by Jules Harnett)

And in December, they - scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) - declared "mission accomplished."

After 11 years, the Antarctic Submillimeter Telescope and Remote Observatory, AST/RO, was dismantled last fall. The 1.7-meter telescope was boxed up for transport and now sits on the snow, awaiting a decision on its next stop.

Tothill
Nicholas Tothill faces the elements in style.

CfA scientist Antony Stark, the project's principal investigator, said AST/RO confirmed theories about an enormous ring of interstellar gas in the galaxy's center and helped explain why the Milky Way's central black hole is less active than those at the center of other galaxies.

"We believe that the black hole is being starved of gas," Stark said during a recent interview.

Stark explained that astronomers believe that every galaxy has a black hole at its center. Some of those galactic black holes appear very active. Though nothing can escape a black hole's gravitational pull, many emit X-ray radiation, generated by gas that superheats as it falls into the black hole itself.

But the black hole at the center of the Milky Way is quiet. Thanks to AST/RO, Stark and other project scientists believe they know why.

station from the air
Aerial shot of South Pole Station with the partially built 'new station' in tan, the dome of the old station to its left buried in snow. The 'Dark Sector' for astronomy experiments is the cluster of buildings in the foreground, with the AST/RO building at the top left of the cluster. (Courtesy of the U.S. Antarctic Program)

Peering at submillimeter radiation coming in through the South Pole's thin, clear skies, AST/RO scanned the center of the galaxy for interstellar gas, specifically carbon monoxide.

Carbon monoxide is among the most abundant of the 100 different molecules known to exist in interstellar space, Stark said, making it a useful indicator for the location of interstellar gas clouds.

Using measurements taken through AST/RO, scientists found an enormous gas ring surrounding the Milky Way's center, confirming earlier theories of the ring's existence.

Stark and other AST/RO scientists now believe that the Milky Way's central black hole is prone to sporadic bursts of activity every 50 million years or so.

That's because the central gas ring is slightly unstable, according to AST/RO's measurements. Gas streaming toward the Milky Way's center builds up in the ring until it forms large lumps that break off and fall into the central black hole. This triggers X-ray bursts from the galactic center that decline as the gas is used up and cease altogether until a new lump breaks off the ring and falls inward. Stark said we're nearing - on a galactic scale anyway - the end of the latest 50 million-year cycle.

"We know we're 10 million years away from having a Milky Way with an active nucleus," Stark said.

Tothill beside mirror
Nick Tothill stands beside the primary mirror of the AST/RO telescope on the roof of the AST/RO building. (Photo by Jules Harnett, January 2004)

Craving 'freshies'

Those advances in understanding the Milky Way would have been impossible without scientists willing to leave friends and family for a long, cold, dark stay in one of the most inhospitable spots on Earth.

Located just a few hundred yards from the geographic South Pole, the Amundsen-Scott South Pole Station was built in 1956, when a Navy construction crew landed and began building a permanent base there. It has been continuously occupied since 1957 when the first scientific crew arrived.

Each summer, with 24-hour daylight and temperatures rising to a relatively balmy minus 20 degrees Fahrenheit, scientific work crews head south to tend the instruments based there. With the summer work window extending just from late October to mid-February, Stark said most of that time is devoted to tending equipment, performing maintenance and upgrades.

Most of the astronomical observations occur after the summer crews head home.

sunset
Sun sets behind AST/RO, the low white building in the foreground half buried in snow. The telescope is the silvery patch on the roof above the rightmost oval window. (Photo by Robert Schwartz, March 2005)

Scientists who've wintered over at the pole said they watch the last plane leave in February with mixed emotions.

"It's a little scary, because it makes your decision final," said Andrea Loehr, a CfA scientist who wintered over in 2005.

After circling the horizon for the summer months, the sun sets in March and stays down until September. Winter temperatures plunge to an average of 76 F below zero.

People handle the long months of isolation by throwing themselves into their work. AST/RO winter-over scientists were among the small number of people each winter whose jobs required them to go outside regularly.

The AST/RO building was almost a kilometer from the main building, meaning a there-and-back trek for researchers each day. Nicholas Tothill, who spent the winter of 2004 at the South Pole, said he could make the trip in about 15 minutes in good weather. If the sky was bright - especially if the moon was up - the going was smooth because his eyes would adjust to the dark and he wouldn't trip over lumps of snow in the path. Flashlights weren't much good, he said, because it was so cold the batteries would quickly fade.

baby-buggy cover over telescope
The 'baby buggy cover' is temporarily deployed over the telescope to provide some protection for scientists cooling down (with liquid helium) a new receiver mounted on the telescope. Something in the sky has caught their eye, as they are out on the roof. (Photo by Jules Harnett, August 2004)

Other scientific projects sometimes piggybacked onto AST/RO, taking advantage of the fact that a researcher would be there to tend the instruments in the winter. Tothill remembers one in particular that required him to remove his outer mitten to adjust a delicate knob. He remembers discussing the instrument with the designers and reminding them that it's pretty cold to be taking one's gloves off at the South Pole. He managed the task by removing just the outer mitten and leaving on his inner liner, but said after putting it back on, the mitten never warmed up again until he got back inside.

Being outside had its benefits, however. Christina Hammock, who wintered over in 2005 as an employee of station manager Raytheon Corp. and who now works at the CfA, said the sight of the night sky and particularly the shimmering aurora australis kept her going.

"The auroras, that's the only thing that makes it bearable," said Hammock. "That's the only reason you don't miss the sun, because the sky is so beautiful."

Julienne Harnett, who wintered over with Tothill in 2004, remembers varied colors of the moonlight reflecting off the Antarctic ice.

Harnett, Tothill, Martin
Jules Harnett (left) and Tothill (center) receive training from previous AST/RO winter-over scientist Chris Martin, November 2003. (Photo by Karina Leppik)

"It really varied, from silver to dark, mercury gray," Harnett said.

Another fact of life was that one seemed never to be dressed just right. With extreme cold outside and room temperature inside, it seemed one was always either too warm - standing inside waiting to go out - or not warm enough, though one winter-over said she just remembers being cold all the time.

When not working, the base offers some amenities. The food is pretty good, by several accounts, though fresh fruits and vegetables, or "freshies" as they're called, become scarce despite a small greenhouse that produces salad fixings with some regularity.

In recent years, with construction of a new base under way, the South Pole has been more crowded than in the past, serving as a home to between 60 and 86 people in winter. When construction is completed, the winter population is expected to fall again to between 35 and 40, according to AST/RO Project Manager Adair Lane.

Over time, the base has developed traditions. Shortly after the last plane leaves, the winter-overs gather in the main dining room, the Galley, for a showing of the science fiction movie "The Thing," about an alien that attacks researchers in an isolated Antarctic base. At midwinter, tradition dictates that the film "The Shining," about a family isolated in a haunted hotel after a snowstorm, be shown.

Midwinter is also the date of the base's biggest party, as residents begin to look forward to the return of the sun and of the planes that connect them with the outside world. By the end of winter, however, the dark, the cold, the close quarters, and even the altitude - the South Pole is at about 9,300 feet on top of a glacier - take their toll. People get cranky, crave fresh foods, and keep an eye out for that first plane of the season to land.

The best site on Earth

Though AST/RO's work has been finished, Stark said a new project is under construction. Called the South Pole Telescope, the 10-meter dish instrument is much larger than AST/RO and will probe the basic nature of the universe.

Like AST/RO, the South Pole Telescope will take advantage of what Stark called "probably the best observatory site on Earth." At an elevation of 9,300 feet and with clear, dry air, telescopes at the South Pole have to deal with less atmospheric interference than telescopes elsewhere.

The South Pole Telescope, which is expected to start operations next winter, will look for the largest structures known to science - clusters of galaxies - by looking for their silhouettes against the cosmic microwave background, a remnant of the big bang that formed the universe.

About 7,000 clusters of galaxies have been discovered so far, Stark said. Those clusters, closer to Earth, have been discovered using visible light. More distant clusters are much fainter, making them difficult to detect using those methods. By looking for cluster-shaped cold spots against the cosmic microwave background, Stark said they should be able to see all the galaxy clusters visible from the South Pole, as many as 30,000.

Stark said the project, which is a collaboration of the Harvard-Smithsonian Center for Astrophysics, the University of Chicago, the University of Illinois, and the University of California, Berkeley, has the potential to keep astronomers busy for decades.

"If this works, it's going to open a whole new field of astronomy," Stark said.

alvin_powell@harvard.edu







Copyright 2007 by the President and Fellows of Harvard College