Word: planetful
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Earlier this month, astronomers from San Francisco State University, the University of California, Berkeley, and the Carnegie Institution of Washington announced the discovery of a fifth planet around the star 55 Cancri, which is 41 light-years away in the constellation Cancer. The find makes that star system the most heavily populated one known other than our sun's and raises to 265 the total of extrasolar planets since astronomers began discovering them in 1995. To skywatchers, however, 55 Cancri is special, not just because of its litter of worlds but because of what it tells us about the possibility...
...newly found planet has about half the mass of Saturn, but its orbit places it about 73 million miles (117 million km) from 55 Cancri, or 20 million miles (32 million km) closer to it than Earth is to the sun. That gives the planet a roughly Earthlike year of 260 days and, more important, puts it in what astronomers call the habitable zone, the distance from its sun at which liquid water can exist. The planet is too dense and gaseous to harbor life as we know it, but if it has any moons, they could be warm enough...
That's a slow process, though. It took 18 years of measurements before the presence of the planet could be confirmed. Now an entirely new planet-hunting strategy, centered on a type of star nobody has been looking at, could reveal in as little as a year a habitable, Earthlike planet--and if the scientists get lucky, more than...
...During the 1990s, sky surveys revealed that these puny stars are as thick as ants at a picnic, accounting for up to 70% of all the stars in the Milky Way. Because an M-dwarf is so faint, its habitable zone is much smaller, so any planet that falls within that zone would be much closer to it than Earth is to the sun. And that, says Harvard astronomer David Charbonneau, gives planet hunters a huge advantage. "Basically," he says, "it lets us cheat...
Rather than looking for a stellar wobble, Charbonneau and others are watching red dwarfs for signs of their light subtly dimming as an orbiting planet passes in front of them--a sort of mini-eclipse known as a transit. "If an Earth-size planet in an Earthlike orbit passes in front of a star like the sun," he says, "it dims the star by 1 part in 10,000 or even less." Since a habitable planet around an M-dwarf is much closer--about 7 million miles (11 million km) away--the transit lasts significantly longer. And since the star...