Kepler-1649c is an Earth-sized

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

, likely

rocky ''Rocky'' is a 1976 American sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the ''Rocky'' franchise and stars Talia Shire, Burt Young, Carl Weathers, and Burgess M ...

, orbiting within the habitable zone of the

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

star

Kepler-1649 Kepler-1649 is a red dwarf star of spectral type M5V with a radius , a mass , and a metallicity of -0.15 e/H Planetary system Two confirmed planets orbit the star: Kepler-1649b and Kepler-1649c. Kepler-1649b is similar to Venus, where ...

, the outermost planet of the planetary system discovered by ''Kepler’s'' space telescope. It is located about away from

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 ...

, in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Cygnus. Kepler-1649c orbits its star a distance of from its host star with an orbital period of roughly 19.53

days A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two solar ...

, has a mass 1.2x times that of Earth, and has a radius of around 1.02 times that of Earth. Based on its mass and radius, it is likely a terrestrial planet, though its proximity to its star means it may likely be

tidally locked Tidal locking between a pair of co-orbiting astronomical body, 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 ...

. Kepler-1649c is estimated to receive about three-quarters of radiation from its host star as Earth does from the Sun. In 2017, Jeff Coughlin, the director of SETI's K2 Science Office, described it as the most "similar planet to Earth" found so far by the

Kepler Space Telescope The Kepler space telescope is a disused space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

. The planet was initially deemed a false positive by Kepler's robovetter algorithm. The Kepler False Positive Working Group published its recovery on April 15, 2020. Its first scientific description was published in ''The Astrophysical Journal Letters'', with first author Andrew Vanderburg, in April 2020.

Physical characteristics

Mass, radius and temperature

The exoplanet was identified as a rocky planet by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

and is very similar to

in terms of size, with a radius 1.06 times that of Earth.

Host star

Kepler-1649 is a type-M red dwarf star estimated to be roughly ¼ the radius of the Sun with only two confirmed planets in its orbit, the other being Kepler-1649b. Kepler-1649b is similar to

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

from our own solar system in two ways: both Kepler-1649b and Venus have orbits roughly half the radius of the next known planets (Kepler-1649c and Earth respectively), and they are of similar size.

Orbit

Kepler-1649c takes only 19.5 Earth days to orbit its host star Kepler-1649, an M-Type red dwarf. It orbits within the habitable zone of its star system, Kepler-1649.

Habitability

PIA23689-ViewFromKepler1649cOfHostStar-20200415

While the exoplanet does orbit within its star's habitable zone, due to the lack of information on the exoplanet's atmosphere, it is unclear if Kepler-1649c can sustain liquid water on its surface. As of 2021, no solar flare-ups have yet been observed from the host star; nonetheless, scientists believe that such stars are prone to frequent solar flare activity, and that such flares may have stripped the exoplanet's atmosphere and hindered the prospect of life.

Climate

Very little is known of Kepler-1649c's climate. It receives fully 75% of the light from its host star that Earth receives from the Sun; therefore, depending on the atmosphere, its surface temperature may be similar enough to the temperature of the Earth that liquid water may be present. It is unclear what the composition of Kepler-1649c's

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

is. Orbital evolution models show that significant oscillations of eccentricity under the gravitational influence of Kepler 1649c are likely, but the climate would remain

-like for most initial parameters.

References

{{Sky, 19, 30, 00.900, +, 41, 49, 49.514 Exoplanets discovered by the Kepler space telescope Exoplanets discovered in 2020 Near-Earth-sized exoplanets in the habitable zone Transiting exoplanets