Earth-like planets (meaning that they’re small and rocky, not that they have aliens writing blogs about science) are not only NOT rare–they’re the most common type of planet in our galaxy.
That was until Dimitar Sasselov gave a little lecture about exoplanets in England earlier this month. That little lecture was a TED Talk and was posted to the web last week. Now everyone is saying Sasselov leaked the news. DiscoveryNews:
Although these Kepler results were supposed to remain secret until February 2011, Sasselov has given the world an unofficial glimpse into the possible discovery of Earth-like extra-solar planets. But by the looks of things, we're not talking about one or two “second Earths.” We could be looking at a galaxy with a dominance of small rocky worlds.
And Science magazine’s ScienceInsider gives us the number of these potential worlds:
At 8:15 into his 18-minute talk, Sasselov showed a bar graph of planet size. Of the approximate 265 Kepler planets represented on the graph, about 140 were labeled "like Earth," that is, having a radius smaller than twice Earth's radius. "You can see here small planets dominate the picture," said Sasselov.
Earth-like planets are a big deal because most of the exoplanets found in the Milky Way thus far are gas giants. It doesn’t mean that small, rocky planets don’t exist—it’s just that Jupiter-like planets are easier to spot transiting their stars.
In “Did Kepler Scientist Leak Data? Um, Not Really” posted in this afternoon in Universe Today, Nancy Atkinson thinks today’s news is a little over the top,
But really, this is pretty much what the Kepler team said in June, that they expected half of the 750 planet candidates would turn out not to be planets, and a fair number of those might be Earth-sized.
In fact, the team published a paper stating that the majority of these new exoplanets are Neptune-sized or smaller.
And Sasselov explains in the talk that statistically, small rocky planets are more likely to be the norm—we only have to look at our own solar system for proof. Out of nine planets (he includes Pluto, so we can, too!), his graph shows five are small and rocky. But only one supports life. And he goes on to say that just because they are Earth-like, doesn’t mean these 140 planets are habitable. More research will be needed.
And Sasselov should know. He’s also the director of Harvard’s Origin of Life Initiative and in fact, was a consultant for the Academy’s planetarium show, Fragile Planet. He helped visualize the potentially habitable planet, Gliese581d, which is featured in the show.
Gliese581d from Fragile Planet