Reaching for the Stars: UC astronomers

Author: 
Dan Falk
Magazine Section: 
Focus

For these UC astronomers, the sky is definitely not the limit

Sara Seager’s enthusiasm for astronomy began with a camping trip at age ten, when she was blown away by the myriad of stars that were visible when one escaped far from city lights. Today, the Professor of Planetary Science and Physics is focused on stars that have their own planets, and especially any planet that might resemble our own blue-green world – or as she calls it, “Earth 2.0.” She states her goal plainly: “We want to find a planet which, like earth, could support life.”

Seager (BSc 1994 UC) graduated from the University of Toronto, picked up a PhD from Harvard in 1999, and has been at the Massachusetts Institute of Technology since 2007.  Last year, she received a MacArthur “genius” award. Her timing has been impeccable: She began her career when the field itself was young, putting her on the front lines as the idea of “extrasolar planets” (or “exoplanets”) went from being science fiction to an active area of nuts-and-bolts research.

The most compelling data has come from Kepler, a space-based telescope launched in 2009.  Kepler has been aimed at a single, small swath of sky – containing thousands of stars – and checking to see how many of them are periodically dimmed by the motion of a planet passing in front (what astronomers call a “transit”). “Kepler has been revolutionary,” says Seager. “Its goal was to tell us how common earth-like planets around sun-like stars are – so that if we wanted to do something more detailed, we’d know what the odds are.” Those odds now look pretty good: Kepler has flagged nearly 1,000 exoplanets, some of them remarkably similar in size to our own Earth.

And the search is moving quickly. We might be less than a decade away from identifying another life-bearing world, says David Charbonneau (BSc 1996 UC), another grad who is passionate about planets. “I think we really could be in the business of looking for life on its surface, on a timescale of five or ten years,” says Charbonneau, who now works down the road from Seager, as a Professor in the Department of Astronomy at Harvard. Like Seager, Charbonneau was star-struck at an early age, but in university his first choice was cosmology. Then, suddenly, planets became a hot topic. “I switched entirely what I was going to do for my thesis, and I never looked back,” he says.

As a graduate student, Charbonneau made the first ever detection of an exoplanet transiting its parent star – and he did it using a telescope with a measly 4-inch (10 centimetre) diameter lens. That was in 1999; just ten years later came the launch of Kepler, which has “revolutionized the whole field,” Charbonneau says.

But Kepler is just the beginning: With the transit method now tried-and-true, other projects are adopting a similar approach. Charbonneau is excited about “MEarth” (pronounced “mirth”), a transit-hunting array of robotic telescopes perched on top of Mount Hopkins in Arizona that are monitoring the brightness of thousands of red dwarf stars. Seager, meanwhile, tells me about TESS (Transiting Exoplanet Survey Satellite); due for launch in 2017, the spacecraft will look for transits involving nearby stars, helping to pin down specific, potentially life-friendly planets in our own “stellar neighbourhood.”

Future missions may allow astronomers to study an exoplanet’s atmosphere directly, in the hope of finding “biosignatures” – the signs of any chemical, or combination of chemicals, that might hint at the presence of life. “Whether that life is single-celled bacteria or intelligent alien life, we’re not able to discern,” says Seager. But any biosignature discovery, she says, would be a momentous discovery.

***

While Seager and Charbonneau look for planets, Wendy Freedman (BSc 1979 UC) is probing the origins of the universe itself. Freedman earned her PhD in 1984, and in that same year she joined the staff of the Observatories of the Carnegie Institution in Pasadena, California, where she’s been the Director since 2003. A good chunk of her career has been devoted to pinning down the value of something called the “Hubble constant” – a critical parameter in the big bang model of the cosmos, necessary for calculating the universe’s size and its age.

The good news is, there’s been a huge amount of progress over the last couple of decades, thanks to fine-scale mapping of the cosmic microwave background radiation, often described as the faint “echo” of the big bang, and also from studies involving the motion of distant galaxies. Freedman herself led the Hubble Space Telescope Key Project, a decade-long effort in which astronomers used the Hubble Telescope to study galaxies by measuring the brightness of certain kinds of variable stars, known as Cepheid variables, within those galaxies.

All of these measurements help pin down the value of the Hubble constant, and, in turn, quantities like the universe’s age. “Twenty years ago, we were arguing whether the universe was 10 billion years old or 20 billion years old – we really didn’t know it to better than a factor of two,” says Freedman. “Now the argument has come down to, is it 13.7 billion years old, or is it 13.8 billion years old? So we have really made a major step forward.”

***

You don’t have to reach for the edge of the universe or the beginning of time to appreciate the grandeur of the cosmos. For members of the public, a bright comet or a solar eclipse might do the trick; for some, a glimpse of Saturn’s rings through a telescope will become a memory that lasts a lifetime. “Astronomy isn’t just for astronomers,” as John Percy (BSc 1962 UC), known around the world for his astronomy outreach efforts, told me. Back in 1967, Professor Percy was a founding faculty member at the University of Toronto’s Mississauga campus. His own research has focused on variable stars and stellar evolution, but outreach and education was always a top concern. He’s worked extensively with school boards in developing curricula, and in providing resources for teachers that might not have a background in astronomy.

In fact, U of T astronomers have been spreading the word about the cosmos for decades. As Percy points out, the Dunlap Institute for Astronomy and Astrophysics owes its existence to a public lecture: The year was 1921, and Clarence Chant, the founder of the Astronomy Department, was giving a public talk about a comet that was visible at the time from Canadian skies. A wealthy mining executive named David Dunlap happened to be in the audience. After his death, Dunlap’s widow donated the funds for the construction of the David Dunlap Observatory in Richmond Hill; from 1935, it would be home to Canada’s largest optical telescope, with its 74-inch (1.9 metre) mirror.

Today – seven years after his official retirement – Percy is optimistic about the state of Canadian astronomy. Canadian scientists are involved with some of the world’s largest telescopes, including the Gemini Observatory (with twin 8-metre telescopes in Hawaii and Chile), a giant radio telescope array known as ALMA (Atacama Large Millimetre Array) in Chile, and the James Webb Space Telescope – the replacement for the much-celebrated but soon-to-be-retired Hubble, due to launch in 2018. With those instruments, and with many other more modest ones, a new generation of astronomers will be tackling the mysteries of the universe, from the big bang to black holes.

“When you do surveys of astronomical productivity, Canada is always in the top three,” says Percy. “If this was hockey, it would be on the front page of the newspapers, but Canadians aren’t fully aware of how many important contributions Canadian astronomers have made”– nor of how many Canadian astronomers got their start at UC.

 

Dan Falk is a science journalist based in Toronto. His most recent book is The Science of Shakespeare: A New Look at the Playwright’s Universe.

Images courtesy of  NASA/JPL-Caltech.