Both planetary science and cosmology are ripe for big news in 2011, the former in its effort to find planets beyond the Earth and the solar system that could harbor water and thus life as we know it, and the latter in the unending effort to figure out what the universe is made of.

Finding out how common habitable planets are around Sun-like stars is the mission of NASA’s Kepler satellite, which has been trailing the Earth’s orbit of the Sun ever since its launching in March 2009, staring at 156,000 stars in the constellations Cygnus and Lyra looking for telltale blips in starlight caused by planets passing in front of them. Last June, the Kepler team released a list of 350 stars thought to be harboring planets, but at the same time, and over the protests of some astronomers, they held back the data on 400 more stars that they wanted to check out over the summer.

In February, the Kepler 400 are expected to be released. The smallest planet on the previous list was about one and a half times the diameter of the Earth. The Kepler scientists will not say anything about the stars on the withheld list or their candidate planets, but in an e-mail message Natalie Batalha, a co-investigator on Kepler, said it would not be unreasonable to suspect that there is a smattering of planet candidates smaller than that on the new list. More small planets could also show up as more data is analyzed, she said.