The U.S. space agency announced Wednesday it has discovered six planets around a mid-sized Sun-like star.
"This is the most important thing in the field of extrasolar planets since the discovery of 51 Pegasi b, the first exoplanet detected in 1995," said Jack Lissauer astronomer, during a telephone press conference organized by the journal British scientist Nature.
This new planetary system was discovered by the Kepler satellite orbiting a star called Kepler-11, located 2000 light years from Earth.
Launched in March 2009, the Kepler space telescope's mission is to scrutinize more than 100 000 stars like the sun in the constellations of Cygnus and Lyra Milky Way.
The mission will last 3 ½ years will cost about 600 million dollars to the U.S. space agency.
The six exoplanets discovered by NASA are grouped around their stars in an orbit size of Mercury. They are very warm and do not provide conditions conducive to life.
They are two to four times bigger than our planet, and their mass is 2.3 to 13.5 greater than that of Earth.
The discovery of this planetary system that looks like a compact disc flatter than our solar system reinforces the theory that planets are formed within disks of gas and dust orbiting a star.
The two planets closest to the Kepler-11 are "mostly composed of water, possibly with a thin film of hydrogen and helium above, like mini-Neptune," said Daniel Fabrycky researcher at the University of California at Santa Cruz and co-author of the study.
The researchers did not exclude the presence of rocks. The other planets, partly soft, have a lower density than water.
The details of the discovery were published in the scientific journal Nature.