Astronomers find smallest planet outside of solar system

Scientists have located the smallest planet found to date outside the solar system, astronomers with the Spanish Research Council and University College London announced Wednesday. 

The planet has a mass five times larger than Earth's and is 30 light-years away, orbiting a star in the constellation Leo, reported the team consisting of the research council's Ignasi Ribas and Andreu Font-Ribera along with visiting astrophysicist Jean-Philippe Beaulieu. 

Their findings were published Wednesday in Astrophysical Journal.

The researchers predict the new planet, called GJ 436c, is rocky with a radius roughly 50 per cent larger than Earth's.

"After final confirmation, the new exoplanet will be the smallest found to date," Ribas, the lead author, said in a release.

The researchers said that most of the roughly 280 planets so far discovered are gas giants similar to Jupiter. They noted that some planets with masses less than 10 times that of Earth's, called super-Earths, have been found, but none smaller than their discovery.

The researchers located the planet by monitoring the changes on the orbit of a known planet, the first found using this method.

"Because of this, the study opens a new path that should lead to the discovery of even smaller planets in the near future, with the goal of eventually finding worlds more and more similar to the Earth," Ribas said.

The astronomers said that one day on the new planet would be equivalent to more than three weeks on Earth.

They conducted simulations of the planet's rotations around the host star, GJ 436, and found that it orbits once every 5.2 days and completes a revolution in 4.2 days. In comparison, Earth revolves every 24 hours and completes a full orbit in 365 days, with a full day closely corresponding with the rotation period.