An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago.Danielle Futselaar & Franck Marchis
A state-of-the-art camera, partly built in Canada and specially designed to see planets orbiting nearby stars, has chalked up its first discovery – a giant planet that resembles a much younger and hotter version of Jupiter.
The discovery could shed light on our own celestial history, researchers say, because the planet may have formed in much the same way as Jupiter and Saturn did, in a place that leaves room for Earth-sized planets that could be orbiting closer to the star.
"This is a very exciting result," said Jeff Chilcote, a postdoctoral researcher at the University of Toronto's Dunlap Institute and a member of the discovery team. "We're trying to understand solar systems that are like our solar system."
The planet was spotted by the Gemini Planet Imager, or GPI (pronounced "Gee-Pie"), which was installed on the Gemini South Telescope at Cerro Pachon, Chile, in 2013.
The new-found planet circles the star 51 Eridani, located about 100 light years away – a short hop by galactic standards. That makes it an ideal target for GPI's precision optics, including key components that were developed and built at the National Research Council's Herzberg Institute of Astrophysics in Victoria.
Although close to 2,000 planets have been discovered by various indirect means over the past 20 years, only a handful have been seen directly.
GPI is one of a new generation of astronomical instruments built to subtract the intense light of a target star to isolate the image of an orbiting planet that is a million or more times fainter. The feat has often been compared to spotting a firefly perched on the rim of a blazing searchlight.
The advantage of the technique is that it allows astronomers to glean details about a planet's atmospheric properties and composition.
"That's the real bonus here. … We get to detect the light from every planet we discover," said James Graham, an astronomer at the University of California, Berkeley, who first proposed GPI more than a decade ago.
The spectrum of the newly detected planet, dubbed 51 Eridani b by astronomical convention and announced Thursday, reveals that its atmosphere is rich in methane and water vapour – similar to Jupiter's but at a much warmer temperature, because the planet is billions of years younger and still aglow from the heat of its formation.
Estimated to be two to three times heavier than Jupiter, it may be the least massive planet to be spotted to date by direct imaging.
It will take a few years of continued observations of plotting the planet's orbit to determine, but it is probably about as far from its star as Saturn is from the sun, Prof. Graham said.
That puts it in a zone where it could have started as a rocky nucleus that grew quickly enough to attract a much larger mass of hydrogen gas. If so, it probably formed the way Jupiter did. Researchers have long suspected that Jupiter has an Earth-sized rocky core at its centre.
The apparent similarity strengthens the possibility that the system could harbour smaller planets like Earth located even closer to the star.
Now that 51 Eridani b has been discovered, the new system is sure to be scrutinized by future planet hunters using the James Webb Space Telescope, slated for launch in 2018, or the planned Thirty Meter Telescope, a project that Canada joined this year and could see first light in 2024.
"This will be a well-studied system over the next decade or so," Prof. Graham said.
Ivan Semeniuk