When Bruce Macintosh was a first-year student at the University of Toronto, the notion that one could point a telescope at a distant star and grab a snapshot of an alien world would have been too far fetched even for a Star Trek episode.
This past November, Dr. Macintosh, now a physicist with Stanford University and the Lawrence Livermore National Laboratory in California, travelled to a mountain top in Chile and did just that.
“It was pretty astonishing,” he said. “The first few minutes we were just staring at it and saying ‘Is that little blob real?’”
It was. Even after a decade of designing and building a camera for precisely this purpose, it came as something of a surprise to Dr. Macintosh and his colleagues to witness just how well their new device worked at picking off a planet orbiting more than 60 light-years from Earth. The result – a triumph for team members, including a group of Canadian scientists that built about one-third of the camera’s instrumentation – marks a turning point in the effort to directly image solar systems beyond our own.
“Now we can start to get dozens of them,” Dr. Macintosh said. “Hopefully, they’ll just be falling off the telescope.”
The $25-million camera, known formally as the Gemini Planet Imager but referred to by team members as GPI (pronounced “G-Pie”), is the product of an international consortium. It made its debut on Tuesday when Dr. Macintosh and colleagues unveiled their first test images at an international meeting of astronomers in Washington, D.C.
In one of those images, a planet that was previously known to be orbiting the star Beta Pictoris shows up as a small but distinct dot. What is remarkable is that it would previously have taken an hour or more to acquire such an image and days of processing to tease out the target buried in the data. The new camera spotted it in minutes.
Exoplanets – the term for planets that orbit stars other than the sun – have been making news ever since the first few were detected in the mid-1990s. Last year the number of confirmed exoplanets topped 1,000 and the now-defunct Kepler spacecraft has identified thousands of possible candidates to add to the list.
Yet, nearly all of these distant worlds have never been seen. Instead, their existence is inferred, mostly through the modest gravitational tugs they exert on the stars they circle, or by the slight dip in a star’s brightness that occurs when an orbiting planet crosses in front.
Only since 2009 have astronomers succeeded in separating the faint light of a handful of planets from the overpowering glare of their host suns – an arduous feat likened to spotting a firefly perched on a blazing searchlight kilometres away.
Now the doors on exoplanet observation have been blown wide open. Because it was specially designed for the task, GPI is the most efficient camera yet at locking onto a star and carefully subtracting away its light while allowing the light of an adjacent planet to pass through and form an image.
“There really hasn’t been anything quite like it,” said Les Saddlemyer, a systems engineer with the National Research Council, who oversaw the Canadian phase of the camera’s construction and is now part of the team fine-tuning its performance on the massive, eight-metre Gemini South telescope in Chile. The camera is more than ten times more sensitive than previous instruments, which will allow it to be used in a broad survey of about 600 stars later this year in hopes of discovering new planets.
The camera’s design should allow it to image planets circling around stars that are located up to 230 light-years from Earth, providing a revealing sample of the worlds that exist in our local region of the Milky Way galaxy.
The sample will not be entirely representative, however. The camera works in the infrared part of the spectrum where only newly formed giant planets – younger versions of Jupiter and Saturn in our own solar system – are bright enough to be seen. These planets are still aglow from the heat of their recent creation. But that is precisely why scientists are excited about the power of seeing such recently arrived worlds with GPI.
“We can actually see them, which means we can look at what they’re made of much more easily,” said Quinn Konopacky, a postdoctoral researcher at the Dunlap Institute for Astronomy and Astrophysics in Toronto and a member of the GPI team.
The camera will not just image planets but will allow their light to be collected and analyzed for clues to their chemical composition. Dr. Konopacky said she hopes to use this data to address long-standing questions about precisely how giant planets form.
Equally important, because of the way the camera subtracts the light of the central star, it will only show giant planets that orbit their stars at a distance. Solar systems that harbour such planets are different from the majority of those that have been found so far, because most indirect methods for planet detection favour large worlds that are very close to their stars.
Yet it’s the solar systems with the big planets located farther out that are thought to be more like our own. If Jupiter and Saturn orbited our sun closely, Earth would have been disrupted from its own trajectory long ago, rendering human life impossible.
Whatever GPI spots will be complementary to what has already been discovered, because it represents not just a single tool, but the coming of age of a new technique, says Sara Seager, a physicist and exoplanet expert at the Massachusetts Institute of Technology who is not part of the GPI team.
“Now it is the ‘direct imaging’ planet-finding technique’s turn to make waves,” Prof. Seager said.
In fact GPI is currently in the vanguard. A similar camera called SPHERE now being built by the European Southern Observatory is expected to come online later this year. By then, GPI should be announcing its first discoveries and offering astronomers a new window on worlds beyond our own.