My friends lists are filled with news from Kepler 62, known formally as 2MASS J18525105+4520595. Located 1200 light-years away in the constellation Lyra (Vega with its confirmed protoplanetary disc is much the most famous star in that constellation, and much nearer), two super-Earths only moderately larger than our own world orbit within that orange dwarf’s habitable zone. The basics are outlined in the official NASA press release.
The Kepler-62 system has five planets; 62b, 62c, 62d, 62e and 62f. The Kepler-69 system has two planets; 69b and 69c. Kepler-62e, 62f and 69c are the super-Earth-sized planets.
Two of the newly discovered planets orbit a star smaller and cooler than the sun. Kepler-62f is only 40 percent larger than Earth, making it the exoplanet closest to the size of our planet known in the habitable zone of another star. Kepler-62f is likely to have a rocky composition. Kepler-62e, orbits on the inner edge of the habitable zone and is roughly 60 percent larger than Earth.
The third planet, Kepler-69c, is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our sun. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus.
Scientists do not know whether life could exist on the newfound planets, but their discovery signals we are another step closer to finding a world similar to Earth around a star like our sun.
The Centauri Dreams post “Water Worlds in the Habitable Zone” goes into more detail about the potential habitability.
Kepler 62 is a class K star somewhat smaller and cooler than the Sun. According to the CfA’s models, Kepler 62e should be cloudier than the Earth, while the cooler Kepler 62f would need to take advantage of the greenhouse effect from carbon dioxide in the atmosphere to keep it warm enough for the ocean to remain liquid. Harvard’s Dimitar Sasselov notes in this CfA news release that discoveries like this raise the prospect of other stars with not one but two planets in the habitable zone. That conjures up what until recently was our view of the Solar System, when not so many decades ago we used to believe Venus and Mars might each be habitable worlds.
I think Sasselov is right to linger over this thought. These may be water worlds and most likely would not develop technological civilizations, but imagine a system where two worlds with continents and oceans, worlds much like Earth, existed close to each other in the habitable zone, each highly visible to the other. Surely the inhabitants of planets like these, with the prospect of a truly colonizable world this close, would be impelled to make the crossing.
The other planets around this star? Kepler 62 b, c and d are 1.31, 0.54 and 1.95 times the size of the Earth, respectively, all orbiting the star too tightly to be in the habitable zone. For more, see this University of Washington news release. Kaltenegger and Sasselov’s work is to be published in The Astrophysical Journal, while Agol is second author of the discovery paper published online in Science today as Borucki et al., “Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone” (abstract).
I found, via The Dragon’s Tales, this interesting non-technical outline by Keith Cowing of Astrobiology Web, “Kepler-62 Has Two Water Worlds Circling in its Habitable Zone”.
As the warmer of the two worlds, Kepler-62e would have a bit more clouds than Earth according to computer models. More distant Kepler-62f would need the greenhouse effect from plenty of carbon dioxide to warm it enough to host an ocean. Otherwise, it might become an ice-covered snowball.
“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” said Harvard astronomer and co-author Dimitar Sasselov.
“The good news is — the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future,” he added.
The discovery raises the intriguing possibility that some star in our galaxy might be circled by two Earth-like worlds — planets with oceans and continents, where technologically advanced life could develop.