Planet-hunting astronomers revealed Thursday that they’d found two tantalizing worlds, seemingly congenial to life as we know it, orbiting a star 1,200 light-years away.
Neither planet has been seen directly, and whether they actually harbor living things is speculative. Their presence has been inferred by the dimming of their parent star at regular intervals, as observed by NASA’s Kepler Space Telescope.
Kepler 62-f is just a bit larger than Earth — 1.41 Earth radii, to be precise — and it’s in the so-called Goldilocks position, orbiting the star (Kepler 62) at a distance where water could be splashing freely at the surface. The scientists think Kepler 62-f is a rocky planet like our own.
They also found Kepler 62-e, which is 1.6 times the radius of the Earth. It is closer to the parent star and warmer, but also within what is presumed to be the habitable zone. Scientists think the size of Kepler 62-e makes it a good candidate for being a water world, completely covered by ocean.
All told, the Kepler team revealed seven new planets in two planetary systems Thursday, publishing findings online in the journal Science and holding a news conference at NASA’s Ames Research Center in Mountain View, Calif.
“This is really cool,” said Pete Worden, the director of NASA Ames.
The Kepler telescope was launched in 2009 and has found more than 100 planets to date. The ultimate goal of planet-hunting astronomers is to find a true Earth twin, a planet that is no larger than our own and in an Earth-like orbit. Kepler 62-f comes very close. The mass of the planet is unknown, but computer models suggest that it must be a rocky planet like our own, and not a gas giant like Jupiter or Saturn or an ice world like Uranus or Neptune.
“We think that it may have significant land masses,” Kepler lead scientist William J. Borucki said.
The first exoplanet — a planet outside our solar system — was found in 1995, and since then a frenzy of planet-hunting using a variety of techniques has produced hundreds of discoveries. Extrapolating from what has been observed so far, astronomers increasingly think that planets are commonplace in the universe, and that our galaxy alone could have billions of planets in life-friendly orbits.
To date, however, extraterrestrial life remains conjectural. No life has been found beyond Earth. Even if an Earth twin were found, the superficial resemblance would not mean that we’d found a planet that was actually inhabited by living things. As Borucki noted, “We don’t know what life requires to get started.”
The Kepler telescope, which circles the sun in an Earth-trailing orbit, looks for stars that dim in a regular pattern, which would suggest that a planet is passing between the star and the telescope. Several such regularly spaced occulations will tell the astronomers that they’ve got a real planet dimming that star and not some random fluctuation in starlight.
The amount that the star dims will also give the Kepler team a sense of the diameter of the planet involved. As with other techniques for planet-finding, the big, hot, Jupiter-size planets in close-in orbits have been the easiest to detect. Refinement of the search methods have let astronomers find smaller and smaller planets that are farther from their parent stars — like Kepler 62-e and 62-f.