Ray Jayawardhana
As cosmic denizens go, brown dwarfs may not rank among the most spectacular sights. Too massive to be planets, but not hefty enough to burn brightly as stars, these heavenly bodies have nonetheless found an advocate in University of Toronto astrophysicist Ray Jayawardhana.
Dr. Jayawardhana, or RayJay as his colleagues call him, finds valuable clues in these “failed stars” about the mysteries of star and planet formation, work that he will continue through his 2009 NSERC E.W.R. Steacie Memorial Fellowship.
In addition to wide-ranging studies of brown dwarfs, he will also focus on the detection and characterization of giant planets around other stars. Both types of bodies are often lumped together as “sub-stellar objects,” because they share some similarities. But there are important differences as well. For instance, unlike planets, most brown dwarfs are found in isolation rather than in orbit around stars.
Until recently, extra-solar planets could be discovered only through indirect means—by measuring the parent star’s wobble due to an unseen planet’s gravitational tug, or by observing periodic dimming of starlight as a planet passes in front, for example. But Dr. Jayawardhana’s team has taken it one step further. In September 2008, they published a rare snapshot of a likely giant planet circling a young Sun-like star some 500 light years from Earth.
This dramatic addition to the cosmic photo album attracted widespread media attention, but Dr. Jayawardhana values it more for what it can reveal about the origin and diversity of planetary systems. Its high mass (about eight times that of Jupiter) and wide orbit (more than ten times the Sun-Neptune distance) pose challenges to existing theories of star and planet formation and blur the distinctions between stars, brown dwarfs and planets. While planets in our solar system are thought to have built up from particles in a disk surrounding the young Sun, this object may have formed differently, perhaps directly from a contracting gas cloud fragment, as stellar binary companions do.
“One big motivation for my work is a desire to unravel the true diversity of planetary systems out there, and to understand where our solar system fits in,” says Dr. Jayawardhana. “Even though astronomers have discovered a few hundred extra-solar planets since the mid-1990s, that’s just the tip of the iceberg. Because of limitations in our detection methods, we are not really getting the full picture yet.”
Photographing a distant planet involves much more than snapping the shutter, since the bright glare of the star usually hides the faint planet. Going after younger planets (mere millions of years old) helps, since these give off their own radiation rather than just reflecting starlight. Astronomers also use various tricks and advanced optical technology to suppress the star’s glare.
Looking at objects that are relatively close to Earth helps too, which in this case means anywhere from a few light years to several hundred light years. “In the grand scheme of things, this is really close–it’s our cosmic back yard.”
Pushing the limits of the technology is one of Dr. Jayawardhana’s specialties. Working in a highly competitive area, his innovative research proposals win him coveted observation time on the world’s largest telescopes. “We’re trying to use the most advanced instrumentation on the world’s premier facilities to push the boundaries of science,” he says. “That way you get to do new things and discover new types of objects, and characterize them in ways that haven’t been possible until now. It is fun to work on the edge.”
Once an object is discovered, the next steps include finding out more about its characteristics. In the case of planets, that may bring researchers closer to the intriguing possibility of finding signs of life on other planets.
Dr. Jayawardhana’s lifelong enthusiasm about the cosmos is infectious, and he has received many accolades for his communications skills. In fact, had he not become a researcher, he might have pursued a career as a science journalist. The latest of his many outreach efforts involved 3,000 ads that appeared in Toronto’s buses, subways and streetcars for a month, promoting a sense of wonder about the cosmos. “The idea was to reach literally hundreds of thousands of people, even for just 30 seconds, to highlight that we are intimately connected to the rest of the universe,” he explains.