January 10, 2014
Large New Exoplanet Discovered In The Pisces Constellation
redOrbit Staff & Wire Reports - Your Universe Online
A team of astronomers led by Stephen Kane of San Francisco State University (SFSU) has discovered a new giant planet that could have twice the mass of Jupiter.The new planet is located in a star system within the Pisces constellation, and could help scientists gain new insight into how extrasolar planets, or exoplanets, are formed. This new star system contains just one star, as do three other systems containing extrasolar planets studied by Kane and his colleagues.
Kane and his colleagues presented their findings Thursday at the annual conference of the American Astronomical Society (AAS) in Washington, DC, calling the discovery surprising given the high rate of multiple-star systems located in our galactic neighborhood.
“There is a great interest in these stars that are known to host planets,” he explained, noting that astronomers suspect that the process of planet formation in a multi-star system would be vastly different from that in a single-star system. The former, Kane said, “might have not one but two planetary disks” where planets form, “or it could be that having an extra star would be disruptive, and its gravity could cause any protoplanets to pull apart.”
Even though astronomers have found relatively few extrasolar planets in multi-star systems, Kane said that scientists know that they do exist. The investigators used optical imaging data collected at Hawaii’s Gemini North Observatory. They studied four systems and found signs suggesting that something else (perhaps a second star) was also present in the system.
In each of those systems, the radial velocity technique was used to discover the extrasolar planets. This method, which was pioneered by astronomers at SFSU, measures variations in the velocity of a star as it moves towards and away from Earth, perturbed or “wobbled” by the gravitational pull of a nearby cosmic body. Based on the radial velocity signature, astronomers can determine if a planet or star is the source of the wobble.
“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,” the university said. “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,” similar to that of a comet, according to Kane.
“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. But when they took a closer look at the systems, they were able to rule out the possibility that another star was perturbing the system,” the university wrote.
Kane explained that he and his associates thought that they might find stellar companions, but were surprised when they confirmed that none of the four systems had a binary star. However, in the case of the star Pisces' HD 4230, there was unexplained radial velocity apparently originating from the pull of an unknown giant planet.
They were able to confirm that using additional radial velocity data collected at the Keck Observatory. Since they were unable to locate stellar companions, the researchers believe that the leftover radial velocity indicates that all four systems contain additional planets that they have not yet been discovered – particularly in the system known as HD 168443.
“Kane is one of the few astronomers to use a variety of planet-hunting techniques, including radial velocity and imaging. He said that the new findings motivated him to look at other extrasolar systems with similar kinds of unexplained radial velocity data, to see if other stars or planets may be lurking there,” the university wrote.
The research will also appear in the Astrophysical Journal.