Planets from the Very Start

man reading paper at cafe

On a September day in 1991, after several hours at his computer, Alexander Wolszczan's work was done and he needed to move.

"I basically walked out of the office. I needed to calm down a little bit," he told me, recalling the day he confirmed the discovery of the first planets outside of our solar system. We were sitting in a coffee shop about a block from Penn State's University Park campus, where he now teaches. Characteristically low-key and soft-spoken, given to vests and open-collared shirts, the 50-year-old astronomer was gazing out at the drizzle and passing traffic, while the clatter of cups and conversation threatened to overcome the light jazz on the stereo.

"Up to that moment so many planets had been detected and then retracted that you would sort of approach someone and say, 'Hey, I found some planets.' When somebody said something like that to me, I would say, 'Okay, show me your data.'"

When he showed his data to his Cornell University colleagues, there was healthy scientific doubt.

"There always is," he said. "That's the way it should be." But, he continued, "It was very clear to me it couldn't be anything else. Of course, I was risking whatever I was risking by thinking like that, but it's just out of experience and the fact that the model produced such a perfect fit. I knew that it would be very hard to find some alternative explanation, some phenomenon that would mimic orbital motion so well. To me, it was planets from the very start."

Wolszczan's discovery of the first planets orbiting another star involved a radio telescope under repair, a relativistic binary object, and an invisible neutron star with an odd pitch and yaw to the radio pulses it broadcast. But the true start dates back to the summer he discovered the night sky as a boy in post-war Poland.

"I was six, something like that, and I jumped over a barbed wire fence—not high enough. I managed to cut myself quite a bit, so I had to go to the doctor and he had to sew me up and then I had my knee bandaged so I couldn't walk very much. For a six-year-old kid, that was a disaster," Wolszczan told me. "What my father did at night was put me on top of his shoulders and walk. And, I would just ride on top of his shoulders and he would show me the stars just to keep me occupied with something. He told me the stories of the constellations, and all those Greek, and Roman, and Chinese legends associated with various constellations and things like that, and I liked it."

He continued, "It is really impossible to reproduce what I was thinking on one summer's night, being six years old. Too much time has elapsed. But . . . I think I have always been fascinated with time and space and how that works and what is our relationship to time and space. That's why I like mountains. That's why I like to be on the shore of a big ocean and just watch it. I don't have to do anything. It's simply fascinating and kind of mind gripping. And, the same is true for the sky. It's bottomless."

"What makes it gripping?" I asked.

"The size and all the unsolved puzzles," he said. "I find it really fascinating to think about ourselves in this environment of space and time, the fact that we struggle against space and time."

"I've had, on occasion, just a touch of fear of it being so big," I said, remembering nightmares and the darker side of science fiction. "Does that ever touch you?"

"No, not really. It's just that there's so much to learn about. Not only on an intellectual level, but emotionally. To me, it's a very positive experience to sense the immense depth of all this."

In January 1990, the great radio telescope at the Arecibo Observatory in Puerto Rico was rendered only marginally operational while technicians fixed cracks in its 17-year-old structure. No longer able to scan, the huge dish lost its usual long line of astronomers waiting for observing time. But Arecibo could still be pointed at a patch of sky as it moved past with Earth's rotation. Wolszczan had been working as a research associate at Cornell University's National Astronomy and Ionosphere Center at Arecibo since 1983. Seizing a precious opportunity for extended use of the observatory, he got approval to explore new regions for rare millisecond pulsars—a long-time interest of his—away from our galaxy, where they had been found before.

Pulsars are seared clinkers left from the fires of supernova explosions, the cataclysmic stage in the life of supergiant stars. Small in size but incredibly heavy and compressed, these objects may only cover the area of a city on Earth, but have a mass many times that of our sun. Pulsars spin very rapidly—often many times a second—and their magnetic fields shape the radiation they emit into a revolving beam—the effect is like some dervish lighthouse. What makes pulsars of particular use to astronomers is that they make very precise clocks. The arrival of their steady signals, like clock ticks, can be measured very accurately. So depending on the proximity of the pulsar to other objects—say a tight cluster of stars— the stars' gravity will affect pulse arrivals here on Earth, allowing scientists to test relativity and conduct similar experiments impossible in any other way.

At Arecibo, Wolszczan soon spotted two objects that gave him pause—a binary and a pulsar located near the constellation Virgo, the virgin, traditionally seen to be holding up either a spike of wheat, a scales, or a caduceus—a herald's staff. The object near Virgo, a millisecond pulsar 1,200 light years away, sent out beats of radiation twice as fast as a hummingbird's wing beat in flight. Yet it didn't hold the fascination of the binary—a pair of objects, one a dead mass and one a rhythmically radiating pulsar, revolving one around the other. This binary was only the fourth object like it found, and it potentially offered conditions better for studying gravitational phenomena than the one discovered by Nobel Prize winner Joseph Taylor. The millisecond pulsar, known as PSR1257+12 for its position in the sky, was relegated to a routine logging of its pulse arrival times while Wolszczan focused his attention on the binary.

drawing of space with colorful planets

However, it wasn't long before he noticed an apparent irregularity in the pulsar's beats—some were up-tempo and others were downtempo, a bit of a mystery since a more mature milli-second pulsar is relatively stable and not prone to the signal-disrupting starquakes that cause shudders in younger pulsars. More intriguing still was that there seemed to be some pattern to the beat changes, but the data were patchy, like messages on a Rosetta stone from which key words have been chipped. The irregularity might be caused by a star companion, but none was detected. Certainly, the explosion of the supernova would have vaporized any smaller object in the vicinity and the last possible thing it could be was a planet—everything known said no.

For all Arecibo's sensitivity, it was unable to pinpoint PSR1257+12's exact location, introducing the possibility of position error, which can mask or mimic movement of celestial objects. For help, Wolszczan contacted Dale Frail, an astronomer with the National Radio Astronomy Observatory, stationed at the so-called Very Large Array. Located on a high plateau in central New Mexico, the VLA features 27 radio dishes on rails arranged in a giant X. Frail, who could only use the VLA here and there for an hour or two, at first had trouble locating the pulsar; possibly interstellar gases were interfering with the signals. But then he started getting data and was able to transmit locations to Wolszczan.

As the methodical work was progressing between the collaborators in New Mexico and Puerto Rico, across the Atlantic from England came a sensational announcement. In July 1991 Andrew G. Lyne of the University of Manchester claimed he had found a planet orbiting around pulsar PSR1829-10, near the center of our Milky Way. Like Wolszczan, Lyne and his colleagues had noticed variations in the arrival of signals from the star. They believed the changes were caused by the way a smaller object slightly tugged the larger object one way, then another, as it orbited around it. With Lyne's announcement, claim was laid by a respected astronomer as the finder of the first planet outside our solar system.

"There was a media feeding frenzy," recalled Stephen P. Maran, spokesman for the American Astronomical Society and a man who claims to have presided over every AAS press conference in which a planetary discovery has either been announced or retracted, including earlier ones in 1984 and 1985.

Frail recalled that Lyne's announcement was very much on his and Wolszczan's minds as they continued working. Finally, Frail ran through his numbers one last time and faxed off the results to Arecibo with a note. "I remember making a joke: 'Don't find any planets,'" Frail said in a recent phone interview from New Mexico. "My recollection," he said, "was getting an e-mail back immediately saying, 'Two planets,' and gave their masses."

As confident as these words seemed to be, Wolszczan still wanted to be absolutely sure of what he had—one planet with a mass of 3.4 Earths circling the pulsar once every 66.6 Earth days, the other with a mass of 2.8 Earths spinning around PSR1257+12 every 98.2 days. Proving it beyond possible doubt required continued timing of the pulsar's signals and fitting the data into a mathematical model which would predict the arrival of future pulses. Back at Cornell, Wolszczan retrieved additional data from Arecibo off the Internet and crunched the numbers on his computer. By September 1991, it was time for a crucial test.

"I had the model and the computer code modified to accommodate the algorithms, and I had my data set. That was, I would say, the real 'Eureka moment' of this entire story," he said. "I actually remember it because I was sitting in front of this computer and we knew if it didn't work, I would be back to square one. . . . It was like getting ready for a hundred meter dash." Wolszczan ran the numbers but they faltered—"sort of worked" as he put it. The problem, he quickly realized, was that he had assumed the orbits of the two pulsar planets were circular, while most orbits generally are elliptical.

"Including eccentricity in those calculations is not easy. It took me three hours of playing around with numbers and then, at some point, I ran the code again with the improved parameters and all of a sudden, all the systematic residuals disappeared," Wolszczan said. A few more adjustments and he was satisfied he had it—the discovery of two new planets outside of our solar system.

"It was just quite a relief to see this step-by-step procedure finally produce a result," he explained, describing the emotion of that moment. "It was not like all of a sudden I knew it was planets. It was just the assumption I had made at some point and did the work to verify it. It culminated in that moment when I fitted the very precise model to the timing data and that was it."

Wolszczan and Frail published their results in the January 9, 1992, edition of the journal Nature. Then they headed off to the American Astronomical Society meeting in Atlanta, Georgia. Preceding Wolszczan to the podium would be Andrew Lyne, to discuss what he had found around PSR1829-10 seven months before. News media interest was piqued, and "astro-politics" were swirling.

Addressing a lecture hall packed with hundreds of astronomers and the media, Lyne stunned his audience. "This talk is not the one I was originally proposing to give," he began, then valiantly proceeded to explain that just before his departure for the conference he had discovered an elemental, but fatal, error in the work he and his colleagues had done: They had failed to take Earth's motion into account. It had created the illusion that PSR1829-10 was reacting to an object revolving around it.

Sitting in the front row of the hall, Frail recalled hearing gasps roll their way back through the assembled scientists; mixed with a few scattered snickers, according to Steve Maran, who watched as an AP correspondent "scuttled off like a crab" to file his story. Appreciating the unaccustomed display of honesty—other major retractions have been made by letter—the audience gave Lyne an ovation. Now it was Wolszczan's turn.

"You just had a non-discovery and nobody was thinking that there would be planets around the most destructive type of star—a supernova that turned into a pulsar," said Geoff Marcy in a phone interview from his office at the University of California at Berkeley; in 1996, Marcy and Paul Butler would find planets potentially conducive for life as we know it. "Alex's discovery is the most unexpected in the past two decades. There were two major strikes against this batter. The whole astronomical community was on pins and needles. Certainly Alex's discovery came at the most challenging possible time."

Recalled Wolszczan, "It made things quite a bit more difficult because I had to try to sound much more convincing than I had planned to." What turned things that day was the exquisite care evident in his work and the fact that he was systematically able to rule out possible reasons for an erroneous detection—programming mistakes, astrophysical reasons, clouds of ionized gas, and so forth. "I really went over that quite meticulously. There really wasn't much else," he said, adding with typical understatement, "It went quite well."

Marcy credits the Penn State astronomer for the push he gave his own work and the search for extra-solar planets generally. Wolszczan's homeland has accorded him its highest scientific honor, the Prize of the Foundation of Polish Science, and in February 1996, he was named the winner of the prestigious Beatrice M. Tinsley Award by the American Astronomical Society for exceptionally creative and innovative research. He has also received the Popular Science Grand Award.

Wolszczan later clinched his results in an article in Science, March 1, 1994. Proof of the planets' existence around PSR1257+12 was offered in the form of measurable effects they had on one another. The article also showed the pulsar was host to a third planet, this one with the mass of our Moon, racing around the pulsar every 25.3 days. Blasted by hideous sweeps of pulsar radiation, the planets are all believed to be rock balls barren of life like ours. Yet with Wolszczan's discovery, our view of our place in the universe moved a fraction farther away from the center, toward a more humble reality.

Wolszczan believes that scientists should search for as many planetary systems as possible, so that they can learn the true nature of the process of planetary formation.

"Then we can go on from there. And if, for example, we only find that they cannot harbor life like our sun in any way, then we are back to square one asking the same question again: 'So, what are we doing here?'

"At this point, our hope is we are just part of the much larger business that has to do with planetary systems and life elsewhere on other planetary systems. But if we don't find anything, and we convince ourselves that our existence here on the planet is not the typical course of events, then we will have to look at it again."

I interjected, "It would almost be like being back to the pre-Copernican world."

"Absolutely," Alex said, quickly adding, however, "I hope there will be no need to take a step like that. I presume we will find more planetary systems and, in time, find Earth-type planets around other stars."

Alexander Wolszczan, Ph.D., is distinguished professor of astronomy and astrophysics in the Eberly College of Science, 525 Davey Lab, University Park, PA 16802; 814-865-2918; alex@astro.psu.edu. Writer Charles C. DuBois is coordinator of college relations in the Smeal College of Business Administration.

Last Updated September 01, 1997