Nearby Star System Mystery Solved: Massive Planet Dynamics Explained

Astronomers may have just solved the mysteries of one of the most fascinating nearby star systems. Scientists have managed to create the first viable model for the planetary system orbiting one of the first stars discovered to have planets.

The star system is located just 39 light-years away in the constellation Cancer. It shines brightly when viewed from Earth because it's so close. That said, something has long baffled astronomers about the system.

Since 2002, scientists have been unable to create a plausible model for the masses and orbits of two giant planets located close to the star, named 55 Cancri, in the system. These planets are actually located closer to 55 Cancri than Mercury is to our sun, which baffled astronomers. They couldn't understand how such massive planets could avoid plunging into their parent star or colliding with each other.

"The 55 Cancri planetary system is unique in the richness of both the diversity of its known planets and the number and variety of astronomical observations," said Eric Ford, one of the researchers, in a news release. "The complexity of this system makes it unusually challenging to interpret these observations."

In this case, the researchers developed a tool for simulating planetary systems using graphics cards in order to accelerate the computations. They combined multiple types of observations and found that one of the planets in the system has eight times the mass of Earth, twice the distance of Earth's radius, but is the same density of earth. They also found that it orbited its host star in less than 18 hours, rather than nearly 3 days as originally thought.

"These two giant planets of 55 Cancri interact so strongly that we can detect changes in their orbits," said Benjamin Nelson, one of the researchers, in a news release. "These detections are exciting because they enable us to learn things about the orbits that are normally not observable. However, the rapid interactions between the planets also present a challenge since modeling the system requires time-consuming simulations for each model to determine the trajectories of the planets and therefore their likelihood of survival for billions of years without a catastrophic collision."

The findings reveal a bit more about how this star system operates. This, in particular, can help inform astronomers about other star systems that are further away.

"One must precisely account for the motion of the giant planets in order to accurately measure the properties of the super-Earth-mass planet," said Ford in a news release. "Most previous analyses had ignored the planet-planet interactions. A few earlier studies had modeled these effects, but had performed only simplistic statistical analyses due to the huge number of calculations required for a proper analysis."

The findings will be presented at a meeting of the International Astronomical Union in Belgium in July 2014.