Astronomers Studying New Planets Find that Many Are Not Like Those in Our Solar System

To us, the solar system seems normal. But new studies of the planets sprinkled around other stars suggest that our corner of the galaxy is actually a pretty weird place.

(Photo: C. Pulliam & D. Aguilar (CfA))

Scientists have discovered that a large proportion of the recently discovered planets outside our own solar system are nothing like the familiar planets orbiting our sun. Instead, many are “mini-Neptunes”: roughly the size of Earth but, unlike Earth, composed of a thick layer of gases around a solid core, which is more like the composition of the planet Neptune. That implies that the recipe for making planets in other solar systems is far different than the process that led to Earth’s formation.
The mini-Neptunes “dominate the inventory” of the 3,000-plus planets found by NASA’s planet-hunting spacecraft Kepler, said University of California-Berkeley astronomer Geoff Marcy on Monday at an American Astronomical Society meeting just outside Washington, D.C. “These are planets we never expected based on our own solar system.”
Marcy and his team examined dozens of “exoplanets” – planets that circle a star other than the sun – spotted by Kepler before it went bust last year. With the keen-eyed Keck telescope in Hawaii, Marcy’s team looked for tiny perturbations that planets create in their stars. The bigger the perturbation, the more massive the planet.
The researchers found that exoplanets fall into two groups. Planets that are roughly twice the size of Earth or smaller have a rocky core plus some water, like Earth. But planets two to four times the size of Earth have a rocky core but are also built of lots of gas, like Neptune.
SOURCE: Traci Watson
Special for USA TODAY