Sunshine Recorder

A new index scores planetary bodies on their suitability for life: Two decades ago astronomers suspected that planets might orbit other stars, but no one had ever seen one. These days hundreds are known. In a (subscription-only) paper published in the journal Astrobiology researchers, led by Dirk Schulze-Makuch of Washington State University, have come up with an index that aims to describe just how friendly to life such exoplanets might be. Tipping its hat to the possibility that aliens could have dramatically different biochemistry from earthlings, the index confines itself to measuring big-picture factors such as the presence of a solid surface, the average surface temperature, the strength of a planet’s magnetosphere (which helps shield it from cosmic radiation) and the like. Unsurprisingly, Earth comes top of the list. Interestingly, though, Titan, a Saturnian moon covered in hydrocarbon lakes, takes the second spot in our solar system, ahead of Mars. There is still some doubt about whether Gliese 581g, the highest-scoring exoplanet, actually exists; but the existence of its companion world Gliese 581d, which scores nearly as highly, is uncontroversial. Sadly we won’t be visiting any time soon—the Gliese-581 system is around 20 light-years from Earth, in the constellation of Libra.

A Trip Around Our Solar System: Robotic probes launched by NASA, the European Space Agency (ESA), and others are gathering information for us right now all across the solar system. We currently have spacecraft in orbit around the Sun, Mercury, Venus, Earth, Mars, and Saturn; several others on their way to smaller bodies; and a few on their way out of the solar system entirely. On Mars, a rover called Spirit has just been officially left for dead, after two years of radio silence from it — but its twin, Opportunity, continues on its mission, now more than 2,500 days beyond its originally planned 90-days. With all these eyes in the sky, I’d like to take the opportunity to put together a photo album of our Solar system — a set of family portraits, of sorts — as seen by our astronauts and mechanical emissaries. [38 photos]

Kepler team spots Earth-sized planets orbiting sun-like star: Just two weeks after the confirmation of a planet that’s within the habitable zone of a distant star, the Kepler team is back with the discovery of two Earth-sized planets orbiting in what is now a five-planet system (three other planets orbiting the star, Kepler-20, had been spotted earlier). Although these planets are much too hot to support liquid water, one of them (Kepler-20e) is the smallest exoplanet yet detected. Read more.

Dwarf Planet Eris Is Icy Double of Pluto: Astronomers from France have made the first accurate measurements of the distant dwarf planet Eris, and found that it’s an almost exact doppelganger of the declassified ninth planet, Pluto. Eris was discovered in 2005 and initial measurements pegged its diameter at a fraction larger than that of Pluto. This finding, and the possibility that there were other giant objects in the icy Kuiper belt beyond Neptune, put Pluto’s planetary status into question.