The catalogue of newly found planets is becoming richer by the day. By one new estimate, virtually all the billions of stars in the Milky Way could have a planet orbiting them.
Planets orbiting other stars may be a dime a dozen in the Milky Way, but cheap hardly means boring.
Skip to next paragraphFrom a new pair of planets like Tatooine of "Star Wars" fame, each with its own pair of suns, to a trio of small rocky planets zipping around a red-dwarf star, the cosmos presents a breathtaking plethora of planetary systems. A new estimate suggests that the Milky Way's population of planets exceeds 100 billion.
These are among the planet-hunting highlights from this week's winter meeting of the American Astronomical Society in Austin, Texas.
The ultimate goal is to find Earth-size planets orbiting in a star's habitable zone ? the place?where a planet, with the right atmosphere, can host water as liquid, ice, and gas on its surface.
While no Earth-scale planets in this Goldilocks zone have yet appeared, "these latest observations make it extremely likely that Earth-scale planets in the habitable zone exist, probably in large numbers," says Philip Armitage, an astrophysicist at the University of Colorado at Boulder.
Three results highlighted at the meeting speak volumes about how far researchers have come in the 16 years since astronomers detected the first exoplanet orbiting a sun-like star.
Between 600 and 700 extrasolar planets have been confirmed, depending on which online catalog keeps tally. NASA's Kepler mission has accounted for 35 of these, with another 2,326 "planet candidates" awaiting evaluation.
Yet this number pales beside an estimate offered by a research team that presented its results at the meeting and in the Jan. 12 issue of the journal Nature.
Based on a six-year survey of stars using a technique known as gravitational lensing, in which an intervening star's gravity magnifies the light from a star far behind it, the team estimates that 17 percent of all stars in the galaxy host a planet of Jupiter's mass or greater. About 52 percent of stars host Neptune-class planets, while 62 percent host so-called super Earths.
Given the trend toward higher numbers of lower-mass planets, "statistically, every star in the galaxy should have at least one planet, and probably more," according to Kailash Sahu, a researcher a the Hubble Space Telescope Institute in Baltimore and a member of the research team.
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