An 80-Year-Old Looks at the Skies With New Eyes
Astronomer Sallie Baluinas pauses on the platform of the 80-year-old Hooker Telescope atop Mt. Wilson to touch the bentwood chair where Edwin Hubble sat, night after freezing night, in coat and tie, watching the horizons of the universe expand.
Hubble forever altered Earth’s place in the cosmos when he discovered in the 1920s that the Milky Way is not alone in the cosmos, but merely one among billions of galaxies, all sparkling with billions of stars. Baluinas turns to Hubble for inspiration, because she too is in the business of exploring new worlds. As director of science on the recently refurbished Hooker, she hopes to answer what she calls the second-most-important question astronomers can answer: Are we alone? (The most important, she says, is the nature of God.)
Since early this year, she has been scouring the solar neighborhood in search of sun-like stars, which would be likely prospects for undiscovered solar systems. If humans ever get seriously space-borne, she says, “these are the stars we’ll go to.”
But she also looks to the stars to answer more down-to-Earth questions--in particular, whether the waxing and waning of the sun’s energy output is behind dramatic climate swings on Earth. She’ll also put the Hooker to work as a sentinel, looking out for comets and asteroids passing near Earth “to determine their intentions,” she said.
Ironically, the Edison-era Hooker is now better suited to these tasks than any telescope in the Northern Hemisphere. In fact, Baluinas has already used the Hooker to discover several double stars that astronomers thought were singles.
And because astronomers use light to tell them everything they know about stars, scrambled light from two stars could throw a good many facts into question--including temperature, composition, age and distance. “It might screw up some fundamental knowledge,” she said.
That’s quite a feat for a World War I-era telescope fashioned from French wine bottle glass and constructed at the same factory that made the Hall of Mirrors at Versailles for Louis XIV.
The transformation was made possible by a new set of optics that fits on the Hooker like spectacles. Called adaptive optics, the system uses a small flexible mirror to take the blur out of starlight churned up by atmospheric turbulence.
It is attached to one side of the 100-inch main mirror, where it grabs a swatch of light coming from a guide star, measures its distortion, then distorts the flexible mirror in the opposite direction to compensate.
The results are astonishing. Suddenly an image of a star that has been squirming around like a penny at the bottom of a pool stands perfectly still. It’s like a self-focusing camera that fixes its image 300 times a second.
For now, Hooker has the only full-scale adaptive optics system in astronomy. Sooner or late, astronomers say, all major telescopes will have such a system.
A Suspicious Wobble
This night, Baluinas is after something special. She has just gotten the news via e-mail that astronomer Jeff Marcy of San Francisco State University is about to announce a suspicious wobble in the light from a certain star. The wobble, he concludes, is caused by the gravitational pull of at least one circling body: a planet.
“He’s saying it’s a new planet,” she shouts up to colleague Christopher Shelton, who is perched 12 feet up on the telescope’s tubular struts, pouring liquid nitrogen into the science camera to keep it cool.
Baluinas won’t be able to actually see the planet; no one can do that. Planets are far too dim. Instead, planet hunters scrutinize the spectrum of light from a star to see if it is distorted into the rhythmic wobble that is the sure sign of an invisible orbiting companion.
What the Hooker can see with unprecedented clarity is the star itself. That is critically important, because the wobble in the starlight could turn out to be caused by the pull of a dim stellar companion and not a planet. A planet is a major discovery, but double stars are as common as sand grains on a beach.
The Harvard-based Baluinas is well suited to the task of running this newly souped-up telescope. Her hobby is rebuilding cars. She just finished remaking a 1934 Ford--installing a modern motor and chopping down the roof and windows. “It’s getting painted,” she says. “Black. With flames.”
Like a beloved but abandoned jalopy, the Hooker has been an astronomical relic ever since the Carnegie Institution, its sponsor, shut it down 10 years ago. When fast computers and clever optics made it possible to bring new life to old telescopes, Mt. Wilson was the perfect place to start. Because when skies are clear, the view from Mt. Wilson is the best in the world.
The same blanket of smog that suffocates city dwellers below keeps the air above 5,000 feet remarkably still. Mt. Wilson rises above it all, sticking its head out for a clear view. To combat light pollution, however, astronomers had to find a way to make the images of stars so bright that they would stand out against the city’s glow.
As it turned out, the Department of Defense had been working on a similar problem for decades. Astronomers and missile trackers face common obstacles when they try to see through the Earth’s burbling atmosphere. Even on the clearest night, light filtering down has to fight its way through wind currents that can whip up the air like a jet in a Jacuzzi. The messages in the light get hopelessly garbled. The Department of Defense developed adaptive optics to get around the problem but kept the system classified until a few years ago.
Shortly after that, Baluinas and physicist Chris Shelton of the aerospace firm TRW persuaded Mt. Wilson Director Robert Jastrow to raise private funds to install a system on the Hooker. They got the most expensive part of the system--a flexible mirror--from the Air Force. With an additional $200,000--peanuts in the high-priced world of astronomy--Shelton and colleague Tom Schneider rigged up a system in less than two years.
These days, astronomers using the Hooker don’t have to sit outside, as Edwin Hubble did; instead, they sit in a warm control room stacked with computers and cookies, for munching when 4 a.m. rolls around and blood sugar gets low.
For now, Shelton is still getting the bugs out of the system. In fact, he’s the only one who knows how to get it to work. He moonlights (literally) at Mt. Wilson when he’s not at TRW. (On the side, he’s a musician, good enough to sing in the chorus of La Boheme behind Placido Domingo and appear at the Hollywood Bowl.)
From Hubble’s rickety chair to the rows of processors in the control room, the Hooker reveals astronomy in the midst of an awkward transition between past and future. A gray computer mouse sits uncomfortably on an antique desk. Wooden gears work side by side with state-of-the-art optics.
Before Shelton and Baluinas can set their sights on Marcy’s star, they have to wait for bubbles of warm air trapped in the telescope dome during the day to rise into the cold night. Shelton watches on a computer console as dark and light pixels shimmer in waves like ripples on a pond--his view of what the telescope is seeing. “The dome is burping,” he says. It takes an hour or so for things to settle down, so Baluinas talks about her research on charting the cycles of sun-like stars--known at Mt. Wilson as “Sallie’s stars.” Most such stars, she says, go through cycles of increased magnetic activity every decade or so; the sun’s cycle is about 11 years. No one knows why. “The theory is still quite a muddle,” she says. “We’re trying to understand why the sun has an 11-year clock.”
A Discovery . . . Maybe
The answer might give them clues to some puzzling climate patterns that could have deep implications for global warming on Earth. During the 1700s, for example, the sun was unusually quiet. Sunspots disappeared, as did auroras, indicating diminished solar activity.
Around that time, most of Europe froze over in what has come to be known as the Little Ice Age. Such strange interludes of quiet seem to roll around every few hundred years or so, which means the sun is due for such a period. Conversely, the current trend toward global warming might be caused by an active sun as much as by emissions of heat-trapping greenhouse gases, Baluinas suggests.
Shelton, meanwhile, has sighted on Marcy’s star. It looks like twins--two stars lined up like an abbreviated traffic signal. “Maybe we’ve found something,” he says.
If it’s really two stars--rather than a glitch in the equipment--it means that Marcy hasn’t found a planet after all, but simply another double star.
To know for sure, they have to sight on a different star--one they know is a single star. If they still see multiples, that means the telescope is seeing double because of a flaw in the system--and Marcy’s planet discovery is intact. “You don’t learn anything until you compare and contrast,” says Shelton.
The astronomers hold their breath. Shelton locks in the second star. “Look at that, it’s a dot,” says Baluinas. A dot means that the telescope is not producing double stars on everything it sees. A single dot on this image means that the double dot on the previous image was real. Grins and high fives are exchanged all around.
Baluinas is ecstatic. Checking out the new planet so quickly after its discovery is exactly what the Hooker is good at. If she wanted to check out Marcy’s star on one of the big modern telescopes, says Baluinas, she would have to write a grant and maybe wait for more than a year. The big telescopes are way oversubscribed because too many astronomers are waiting in line to use them. “I’ve done that,” she says. “I’ve spent three years getting two stinky nights at Kitt Peak.”
The Hooker, at present, is undersubscribed--in part because it has just gotten back into operation and astronomers are waiting to see what it can do, Baluinas says.
Suddenly, the bubble of euphoria that filled the small control room only a moment ago plummets like a lead balloon. Now it looks like they have only found a bug in the adaptive optics system--not another double star. “It could be an oscillation in the mirror,” sighs Shelton. That’s how it goes a lot of the time in astronomy. “You think you got it, then you don’t got it.”
Like kicking the tires of a used car to see what shakes loose, astronomers have to keep trying to punch holes in their own results to make sure they’re solid. “You kick the measurement every way you can,” says Baluinas.
Baluinas retreats to a table in the tiny control room to look up coordinates for another possible double star called HD81809. She’s got a list of objects to look at, some chosen by her and Shelton and Jastrow, others submitted from astronomers who would like them to take a look at this or that.
Later that night, HD81809 turns out to be a double, just as Baluinas had predicted. So it was a productive evening after all.
A Few Limitations
Even bug-free, the adaptive optics system on the Hooker has some real limitations. For one thing, something has to tell the deformable mirror exactly how to mold itself to untwinkle starlight--and that requires precise information on how the atmosphere is bending the light.
But the star being studied may not be bright enough to determine such complex information. So a sensor must gauge the distortion in the light from a brighter “guide star,” which may not always be conveniently near the object they want to look at.
There are other restrictions: The view is best when they look straight up. And because the stars they study have to be bright, they are limited to relatively close stars in our galaxy.
Despite the brightening effect of adaptive optics, the relatively small Hooker mirror will never gather enough light to see far out into the universe. But for sharp images of stars, planets, asteroids and comets in the immediate neighborhood, it can’t be beat.
Meanwhile, more cutting-edge technology is coming soon to Mt. Wilson. This summer, Georgia State University will break ground on a constellation of seven telescopes that will work in unison as one gigantic eye; the network should be able to see 100 times more detail than is now possible with the Hubble Space Telescope--equivalent to seeing a nickel 10,000 miles away.
For Baluinas, it is something of a dream come true. When she was about five, she wrote to the National Aeronautics and Space Adminsitration, asking how one got to be an astronaut. They wrote back saying astronauts had to be fighter pilots. “So I thought, OK, I’ll join the Air Force.” Her parents took her to a recruiting station to give her a glimpse of her future. “My parents said they’d never forget the look on my face when they told me little girls don’t grow up to fly jets,” she said. “We left brokenhearted.”
Now, she dreams of someday discovering a new planet. After all, she likes to remind people, the Earth is “a backwater planet,” orbiting an ordinary star. Our unremarkable place in the galaxy leads her to believe there might be others like us out there.
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Taking the Twinkle Out of Stars
A new system called adaptive optics has made the 80-year-old Hooker Telescope on Mt. Wilson the sharpest in the Northern Hemisphere. Here is a simplified breakdown of how the system works:
* PROBLEM: Shifting layers of air in the Earth’s atmosphere bend light and make stars appear to twinkle.
* MIRRORS: Light is gathered by mirrors and reflected to sensors.
* DISTORTION: Sensors measure the distortion in the light and tell a flexible mirror how to compensate.
