New planets discovered

Two newly discovered planets outside our solar system have roughly the size of Earth and the mass of Neptune.

"We found two such planets both 15 to 20 Earth masses," said Geoffrey Marcy, of the University of California at Berkeley.

"Both planets orbit very nearby stars in our solar neighbourhood, and indeed they are only about 35 light-years away."

One of the two planets orbits the star 55 Cancri, already known for its three gaseous giants. The new planet's mass is 18 times that of Earth and slightly more than Neptune's.

The other planet orbits star Gliese 436. Its mass is 20 times Earth's.