Smallest Extrasolar Planets yet Discovered

31 August 2004:Scientists Discover First of a New Class of Extrasolar Planets, NASA

“Astronomers announced today the first discovery of a new class of planets beyond our solar system about 10 to 20 times the size of Earth – far smaller than any previously detected. The planets make up a new class of Neptune-sized extrasolar planets. In addition, one of the new planets joins three others around the nearby star 55 Cancri to form the first known four-planet system.”

31 August 2004: New class of extrasolar planets discovered: new era for planet hunting

“These two newest planets join a growing roster of some 135 exoplanets, so-called because they are outside of our solar system. Both new Neptunes are very close to their parent stars, orbiting once every 2 to 3 days, and have similar likely masses, estimated to be between about 17 and 21 Earths–close to Neptune’s mass.”

31 August 2004: McDonald Observatory Astronomers Discover Neptune-sized Planet with Hobby-Eberly Telescope

“The highlight of the work is the fact that the newly discovered planet, rho-1 Cancri e, has a minimum mass of only 14 Earth masses, and a most likely mass of just 18 Earth masses – about the mass of Neptune.”

31 August 2004: Detection of a Neptune-mass planet in the rho Cancri system using the Hobby-Eberly Telescope

31 August 2004: A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436