Washington: Astronomers have discovered a giant new planet that could be twice the mass of Jupiter located in a star system in the Pisces constellation.
The star system harbouring the new planet contains only one star, which is a surprising finding, given the high rate of multiple-star systems in our solar neighbourhood, researchers said.
There is a great interest in these stars that are known to host planets since astronomers suspect that planet formation in a multi-star system would be very different from planet formation in a single-star system like our own, said Stephen Kane, a San Francisco State University astronomer.
A multiple-star system "might have not one but two planetary disks" where planets form, he said.
"Or it could be that having an extra star would be disruptive, and its gravity could cause any protoplanets to pull apart," he added.
Relatively few extrasolar planets have been found in multiple-star systems, "but we know that they are there," Kane said.
Kane led a team which studied four star systems using optical imaging data collected at the Gemini North observatory in Hawaii.
In each system, the extrasolar planets were found by the radial velocity technique which measures variations in the speed at which a star moves away and toward Earth, "wobbled" by the gravitational pull of a nearby cosmic body.
Depending on the radial velocity signature, astronomers calculate whether the wobble is coming from a planet or star.
In the star systems studied by Kane and his colleagues, there was a part of the radial velocity data that couldn`t be explained entirely by the pull of an orbiting planet.
And at the same time, the planets that had already been discovered in these systems followed eccentric orbits, swinging away from their stars in a less circular and more elliptical fashion, "more like that of a comet," Kane said.
With these two clues, the researchers wondered if the radial velocity and eccentric orbits might be explained by the presence of another star in the system.
"I thought we were likely to find stellar companions, and when all four didn`t have a binary star, that did surprise me," Kane said.
In the case of one star, Pisces` HD 4230, the unexplained radial velocity appears to be coming from the pull of a previously undiscovered giant planet, researchers said.
They confirmed the planet`s presence with additional radial velocity data collected at Hawaii`s Keck observatory.
Given that the researchers did not find any stellar companions, Kane said it is very likely that the leftover radial velocity is instead a signal that there are additional planets to be found in all four systems.