* Astronomy

Both planetary science and cosmology are ripe for big news in 2011, the former in its effort to find planets beyond Earth and the solar system that could harbour 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 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 harbouring 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.
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Using Planet Colours to Search for Alien Earths

Earth is invitingly blue. Mars is angry red. Venus is brilliant white. Astronomers have learned that a planet's "true colours" can reveal important details. For example, Mars is red because its soil contains rusty red stuff called iron oxide. And the famous tint of our planet, the "blue marble"? It's because the atmosphere scatters blue light rays more strongly than red ones. Therefore the atmosphere looks blue from above and below.
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Nearly one in four stars like the Sun could have Earth-sized planets, according to a new estimate published in the journal Science.
A US team has found that on average small, so-called rocky planets are much more common in orbit close to their star than giant planets similar in size to Jupiter.
This estimate is based on observations from nearby stars taken by the the twin 10-metre Keck telescopes in Hawaii. These show that 22 of the stars had detectable planets.
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Title: The effects of fly-bys on planetary systems
Authors: Daniel Malmberg, Melvyn B. Davies, Douglas C. Heggie

Most of the observed extrasolar planets are found on tight and often eccentric orbits. The high eccentricities are not easily explained by planet-formation models, which predict that planets should be on rather circular orbits. Here we explore whether fly-bys involving planetary systems with properties similar to those of the gas giants in the solar system, can produce planets with properties similar to the observed planets. Using numerical simulations, we show that fly-bys can cause the immediate ejection of planets, and sometimes also lead to the capture of one or more planets by the intruder. More common, however, is that fly-bys only perturb the orbits of planets, sometimes leaving the system in an unstable state. Over time-scales of a few million to several hundred million years after the fly-by, this perturbation can trigger planet-planet scatterings, leading to the ejection of one or more planets. For example, in the case of the four gas giants of the solar system, the fraction of systems from which at least one planet is ejected more than doubles in 10^8 years after the fly-by. The remaining planets are often left on more eccentric orbits, similar to the eccentricities of the observed extrasolar planets. We combine our results of how fly-bys effect solar-system-like planetary systems, with the rate at which encounters in young stellar clusters occur. For example, we measure the effects of fly-bys on the four gas giants in the solar system. We find, that for such systems, between 5 and 15 per cent suffer ejections of planets in 10^8 years after fly-bys in typical open clusters. Thus, encounters in young stellar clusters can significantly alter the properties of any planets orbiting stars in clusters. As a large fraction of stars which populate the solar neighbourhood form in stellar clusters, encounters can significantly affect the properties of the observed extrasolar planets.

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