Kepler-1649c is an Earth-sized

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

, likely

rocky ''Rocky'' is a 1976 American independent film, independent sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the Rocky (film series), ''Rocky'' franchise and also star ...

, orbiting within the

habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...

of the

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

star Kepler-1649, 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 Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, 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 first constellati ...

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 (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, and night. This daily cyc ...

, 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 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 ...

. 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 Seti or SETI may refer to: Astrobiology * SETI, the search for extraterrestrial intelligence. ** SETI Institute, an astronomical research organization *** SETIcon, a former convention organized by the SETI Institute ** Berkeley SETI Research Cent ...

'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 defunct 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 agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

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 often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

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

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 A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and ot ...

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 The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

; 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 gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

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