Kepler-1652b (also known by its Kepler Objects of Interest designation ''KOI-2626.01'') is a

super-Earth A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to ...

exoplanet, orbiting within the habitable zone of the red dwarf Kepler-1652 about 822 light-years away in the Cygnus constellation. Discovered by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

's ''Kepler'' spacecraft, Kepler-1652b was first announced as a candidate in 2013, but wasn't validated until four years later in 2017. It is a potential

with 160%

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

's radius. The planet orbits well within the

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kast ...

of its system, the region where liquid water can exist on a planet's surface. The planet is an eyeball planet candidate.

Characteristics

Mass, radius, and temperature

Kepler-1652b, like almost all of Kepler's known exoplanets, was found with the transit method, where a planet blocks a tiny fraction of its host star's light when it passed between the star and Earth's line of sight. As a result, the only well-established parameter is its radius. Based on the size of the star and the amount of light blocked, Kepler-1652b has a radius of 1.60 , within the

range between the sizes of Earth and the ice giants

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

and Neptune. Usually, the transition between rocky Super-Earths and gaseous Mini-Neptunes is expected to be at 1.6 , which would suggest that Kepler-1652b may be a small ice giant or

ocean planet An ocean world, ocean planet, panthalassic planet, maritime world, water world or aquaplanet, is a type of planet that contains a substantial amount of water in form of oceans, either beneath the surface, as subsurface oceans, or on the surf ...

. Kepler-1652b has an equilibrium temperature of , similar to Earth's at .

Orbit

Kepler-1652b has an orbital period of 38.1 days, over 9 times shorter than Earth's year of 365 days. It has a semi-major axis, or average orbital radius, of 0.1654 AU, also much lower than Earth's. Despite its close proximity to the star, Kepler-1652b is still temperate, due to how small Kepler-1652 is compared to the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The planet's eccentricity is believed to be near or at 0.

Host star

Kepler-1652b orbits the red dwarf star Kepler-1652, also designated KOI-2626. It is 0.404 times the mass and 0.382 times the radius of the Sun, with a temperature of 3638 K and an age of 3.2 billion years. For comparison, the Sun has a temperature of 5778 K and is 4.5 billion years old. Kepler-1652 is about 1.6 to 2.6% as luminous as the Sun. The apparent magnitude of the star is 10.22.

Habitability

Kepler-1652b's placement within the habitable zone does not ensure its habitability. Multiple other factors are included, such as composition, atmosphere, and the amount of radiation the planet receives. Kepler-1652b has a temperature very similar to that of Earth, and gets about 81% the sunlight Earth does. This places it well within the conservative habitable zone and means it is unlikely to suffer a

runaway greenhouse effect A runaway greenhouse effect occurs when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface. A ...

. While the planet is most likely

tidally locked Tidal locking between a pair of co-orbiting astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where a tidally locked bo ...

to its host star, which would create one hot side and one cold side, a thick atmosphere - if one exists - can distribute heat evenly around the planet, allowing for more areas to retain liquid water. The high radius of Kepler-1652b decreases its chances of habitability. Most planets with radii of ≥1.6 are expected to either be entirely covered in thick oceans or be more akin to the ice giants like Uranus or Neptune. Without a rocky surface, life may never be able to develop on a planet. Red dwarfs like Kepler-1652 can produce very strong flares, much more powerful than what the Sun produces, which could erode away the atmosphere of orbiting planets, compromising their habitability. While not all red dwarfs are this active, a strong magnetic field can still help keep the worst of the host star's radiation from reaching the planetary surface, protecting any possible life.

References