Big planets far from their stars have, until now, been harder to find. (File Photo)
Scientists have discovered two Jupiter-sized exoplanets about 150 light years away from Earth which could reveal whether life is possible on the smaller planets in other solar systems. "We believe planets like Jupiter have profoundly impacted the progression of life on Earth. Without them, humans might not be here to have this conversation," said Stephen Kane, an associate professor at the University of California, Riverside in the US. "Understanding how many other stars have planets like Jupiter could be very important for learning about the habitability of planets in those systems," said Kane.
Along with liquid water oceans, Kane said astronomers believe such planets have the ability to act as 'slingshots,' pulling objects like meteors, comets, and asteroids out of their trajectories en route to impact with small, rocky planets. Many larger planets have been found close to their stars. However, those aren't as useful for learning about the architecture of our own solar system, where the giant planets including Saturn, Uranus and Neptune are all farther from the Sun.
Big planets far from their stars have, until now, been harder to find. A study, published in the Astronomical Journal, found success in a novel approach combining traditional detection methods with the latest technologies.
One popular method of searching for exoplanets -- planets in other solar systems -- involves monitoring stars for "wobble," in which a star moves towards and away from Earth. The wobble is likely caused by the gravitational pull a nearby planet is exerting on it. When a star wobbles, it's a clue there may be an exoplanet nearby. When the planet is far from its star, the gravitational pull is weaker, making the wobble smaller and harder to detect.
The other problem with using the wobble detection method, Kane said, is that it just takes a long time. Earth only takes a year to orbit the Sun. Jupiter takes 12, Saturn takes 30, and Neptune takes an astonishing 164 years.
The larger exoplanets also take many years to circle their stars, which means observing a complete orbit could engulf an astronomer's entire career. To accelerate the process, Kane and his team combined the wobble method with direct imaging. This way, if the team thought a planet might be causing wobble, they could confirm it by sight.
Obtaining a direct image of a planet quadrillions of miles away is no simple task. It requires the largest possible telescope, one that is at least 32 feet long and highly sensitive. Even from this distance, the light of the stars can overexpose the image, obscuring the target planets. The team overcame this challenge by learning to recognise and eliminate the patterns in their images created by starlight.
Removing the starlight allowed Kane's team to see what remained. The team applied the combination of wobble and imaging method to 20 stars.
In addition to the two being orbited by giant Jupiter-like planets that had not been previously discovered, the team also detected a third, previously observed star with a giant planet in its system. "This discovery is an important piece of the puzzle because it helps us understand the factors that make a planet habitable and whether that's common or not," said Kane.
"We are converging rapidly on answers to this question that the past 3,000 recorded years of history could only wish they had available to them," he said.