Are we alone?

Researchers part of team seeking Earth-like planets near other stars

Steven Schultz

Princeton scientists are competing to answer one of humanity's oldest questions: Are we alone?

Micheal Littman (left) and David Spergel are part of a Princeton team planning a NASA mission to find Earth-like planets near other stars. In this demonstration in Littman's lab, a laser, simulating a star, shines through a 35 mm slide, which imitates the opening of a novel telescope designed by Spergel. The resulting image, which is beamed into a video camera, is well suited to detecting dim objects next to bright ones.


A diverse team, with specialties from engineering to astrophysics, is working with an aerospace company and other institutions to design a $1 billion space-based telescope that can discover and study Earth-like planets orbiting distant stars.

The consortium is one of four teams competing to plan and execute the mission for NASA, which plans a 2012 launch.

The challenge is enormous. Over the last six years, astronomers have found evidence of Jupiter-sized planets outside our solar system, but none has been directly observed. Finding and observing smaller, rocky planets like Earth is beyond the power of any current telescope. Even the closest stars are many light-years away, and the light from a planet would be extraordinarily faint compared to the bright flow of its host star.

"This is something no one has done before," said Jeremy Kasdin, an assistant professor of mechanical and aerospace engineering who is leading the Princeton group. "It is so far out of human experience that we could see a life-bearing planet near another star. And it just opens up so many avenues of thought to contemplate a mission that could actually do it. I just find that incredibly exciting."

The Princeton team, the core of which consists of six faculty members, three graduate students and a postdoctoral fellow, already has generated several conceptual breakthroughs in areas ranging from the design of the telescope to the orbit of the satellite (see related article). Several of the ideas have been published in leading journals and could have broad applicability in space science.

"We've made a lot of progress and have had a lot of fun," said Kasdin. "We really feed off of each other."

Kasdin started the project after attending a December 1999 meeting at the Jet Propulsion Laboratory in Pasadena, Calif., where the National Aeronautics and Space Administration called on scientists in industry and academia to come up with creative solutions to the planet-finding problem.

NASA scientists already had a plan for the mission and even had published the ideas in a small book, but "they recognized that they didn't have a broad enough look and they needed to see more ideas before they committed the dollars," said Kasdin.

"We delved very, very deeply into the science and tried to challenge the basic assumptions," said astrophysicist David Spergel.

After returning from California, Kasdin began to pitch the project to others at Princeton, even though for many scientists here the topic is a significant departure from their usual area of study. Eventually, the group agreed to team up with scientists at the Space Telescope Science Institute in Baltimore, Md., and Ball Aerospace, a satellite manufacturer based in Boulder, Colo.

"When Jeremy asked me to participate, I said, 'No. I'm a cosmologist. I study the universe, not planets, and I've got plenty to do,'" said Spergel.

But for Spergel and the others, the challenge proved too great to pass up. The NASA mission has been a way to have a hand in the start of a whole new area of science.

Minor, dead backwater

Just 10 years ago, the field of extrasolar planets was, as Princeton astrophysicist Ed Turner put it, "a minor, dead backwater." But with the first discovery of a planet orbiting another star in 1995, the field has taken off. A total of 50 such planets have been detected, said Sara Seager, a project participant and member of the Institute for Advanced Study. Still, none of these planets has been observed directly; their presence is inferred from the observation of slight movements of the parent stars, which are tugged out of place by the orbiting planets' gravity.

"People are pouring into the field all over the world," said Turner, who is looking for ways to detect such details as oceans and weather from very minimal data. "It looks very exciting scientifically and a place where a lot of the action will be over the next decade," he said.

Thinking outside the box

Michael Littman, a professor of mechanical and aerospace engineering, said he liked the notion of "thinking outside the box."

"NASA had a box -- it was this book saying how they thought it should be done," said Littman. "All of us looked at that and said there must be other ways, and we began to free associate."

"That's a lot of fun," added Spergel. "That's the dreaming aspect of projects, when you ask, 'What are we really trying to accomplish?'"

NASA is eager for as much of that kind of innovation as possible.

"NASA has made finding Earth-like planets a major, major goal," said Charles Beichman, chief scientist of NASA's Origins program. "The agency takes it very seriously from NASA administrator Dan Goldin on down. It's become an organizing principle in space sciences."

NASA also wants to promote inter-action between academic scientists and engineers and aerospace contractors. "We want them bouncing their ideas off of nasty reality," said Beichman. Some ideas seem great on paper, he said, but turn out to require "many pounds of 'unobtanium' to build."

The Princeton group and its collaborators, working with more than $1 million of funding from NASA, have another year to develop their plan. NASA will then choose two teams to conduct further development, with the goal of selecting a final plan in three to five years.

If all goes well, the mission would be launched somewhere around 2012 and then begin to answer the ultimate question about whether life exists out-side our planet or whether our green and comfortable Earth is unique.

"If we look at the 100 nearest stars, how many have Earth-like planets?" asked Turner. "It could be every one. It could be none. We really have no idea."

Related article
Plane-finding requires fine-tuning


April 16, 2001
Vol. 90, No. 24
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Researchers part of team seeking Earth-like planets near other stars
1,675 offered spots in class of 2005
Photographs illuminate ruins of ancient Athens
Grant funds creation of first electronic archive on the arts

Civility efforts strive to unite campus
Staff rewarded for recruiting effors

By the numbers: the Board of Trustees
Nassau Notes
Calendar of events

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Editor: Ruth Stevens
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Contributing writers: Karin Dienst, Yvonne Chiu Hays, Marilyn Marks, Steven Schultz
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