“This planet really could have formed the same way Jupiter did; the whole solar system could be a lot like ours,” said co-author Bruce Macintosh, from Stanford University’s Kavli Institute.
The new gas giant is roughly twice the mass of Jupiter. Until now, the gas giant planets that have been directly detected have been much larger – five to 13 times Jupiter’s mass.
It orbits a little further from its parent star than Saturn does from the Sun and has a temperature of 430C (800F), hot enough to melt lead, but still rather cold compared with other alien gas giants, which reach temperatures above 540C (1,000F).
The Gemini Planet Imager is installed on the 8m Gemini South Telescope in Chile. It began science operations in 2014.
Other scientific instruments designed to detect exoplanets do so indirectly, by, for example, detecting the dip in starlight as a planet passes in front of its parent sun. GPI instead searches for light from the planet itself – referred to as direct imaging.
The astronomers use adaptive optics to sharpen the image of a star, and then block out the starlight. Any remaining incoming light is then analysed, with the brightest spots indicating a possible planet.