Size comparison of Kepler-186f (artist's impression) with Earth along with their projected habitable zones.
Kepler-186 and the Solar System
http://www.nasa.gov/ames/kepler/kepler-186-and-the-solar-system http://www.jpl.nasa.gov/news/news.php?release=2014-119 http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18000 The diagram compares the planets of our inner solar system to Kepler-186, a five-planet star system about 500 light-years from Earth in the constellation Cygnus.
The five planets of Kepler-186 orbit an M dwarf, a star that is is half the size and mass of the sun. The Kepler-186 system is home to Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distance from a star where liquid water might pool on the planet's surface. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zones of other stars and signals a significant step toward finding a world similar to Earth. The size of Kepler-186f is known to be less ten percent larger than Earth, but its mass and composition are not known. Kepler-186f orbits its star once every 130 days, receiving one-third the heat energy that Earth does from the sun. This places the planet near the outer edge of the habitable zone. The inner four companion planets each measure less than fifty percent the size of Earth. Kepler-186b, Kepler-186c, Kepler-186d and Kepler-186, orbit every 4, 7, 13 and 22 days, respectively, making them very hot and inhospitable for life as we know it. The Kepler space telescope infers the existence of a planet by the amount of starlight blocked when it passes in front of its star. From these data, a planet's radius, orbital period and the amount of energy received from the host star can be determined. The artistic concept of Kepler-186f is the result of scientists and artists collaborating to imagine the appearance of these distant worlds.
Kepler-62f is another habitable planet like Earth and size comparison with earth shows it is quite a bit bigger (1.5 times all around).
Kepler-62f with 62e as Morning Star
http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-morningstar.html http://www.nasa.gov/images/content/742541main_Kepler-62MorningStar-1_full.jpg The artist's concept depicts NASA's Kepler misssion's smallest habitable zone planet. Seen in the foreground is Kepler-62f, a super-Earth-size planet in the habitable zone of a star smaller and cooler than the sun, located about 1,200 light-years from Earth in the constellation Lyra. Kepler-62f orbits its host star every 267 days and is roughly 40 percent larger than Earth in size. The size of Kepler-62f is known, but its mass and composition are not. However, based on previous exoplanet discoveries of similar size that are rocky, scientists are able to determine its mass by association. Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech
Mass, radius and temperature
Kepler-62f is a
super-Earth, placing it in the class of exoplanets with a radius and mass bigger than Earth, but smaller than that of the ice giants
Neptune and
Uranus. It has an
equilibrium temperature of 208 K (−65 °C; −85 °F), close to that of
Mars.
[9] It has a radius of 1.46
R🜨,
[1] placing it below the radius of ≥1.6 R🜨 where it would otherwise be a
mini-Neptune with a volatile composition, with no solid surface.
[10] Due to its radius, it is likely a
rocky planet. However, the mass isn't constrained yet, estimates place an upper limit of <35
M🜨, the real mass is expected to be significantly lower than this.
[1] The
Planetary Habitability Laboratory estimated a mass of around 2.6 M🜨, assuming a rocky Earth-like composition.
[11]
Host star
Main article:
Kepler-62
The planet orbits a (
K-type)
star named
Kepler-62, orbited by a total of five known planets.
[1] The star has a mass of 0.69
M☉ and a radius of 0.64
R☉. It has a temperature of 4925
K and is 7 billion years old.
[1] In comparison, the
Sun is 4.6 billion years old
[12] and has a temperature of 5778 K.
[13] The star is somewhat metal-poor, with a
metallicity ([Fe/H]) of −0.37, or 42% of the solar amount.
[1] Its luminosity (
L☉) is 21% that of the Sun.
[1]
The star's
apparent magnitude, or how bright it appears from Earth's perspective, is 13.65. Therefore, it is too dim to be seen with the naked eye.
Orbit
Kepler-62f orbits its host star every 267.29 days at a
semi-major axis distance of about 0.718
astronomical units (107,400,000
km, 66,700,000
mi), which is roughly the same as
Venus's semi-major axis from the Sun. Compared to Earth, this is about seven-tenths of the distance from it to the Sun. Kepler-62f is estimated to receive about 41% of the amount of
sunlight that Earth does from the Sun, which is comparable to
Mars, which receives 43%.
[1]
Artist's conception of Kepler-62f (foreground) as a rocky terrestrial exoplanet orbiting its host star (center). The actual appearance is not known. Kepler-62e can be seen in the distance as a twinkling star.
