Kepler-62c (also known by its Kepler Object of Interest designation ''KOI-701.05'') is an approximately

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

-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 ...

discovered in orbit around the star

Kepler-62 Kepler-62 is a K-type main sequence star cooler and smaller than the Sun, located roughly 990 light years from Earth in the constellation Lyra. It resides within the field of vision of the ''Kepler'' spacecraft, the satellite that NASA ...

, the second innermost of five discovered 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, succeedin ...

's Kepler spacecraft around Kepler-62. At the time of discovery it was the second-smallest exoplanet discovered and confirmed by the ''Kepler'' spacecraft, after

Kepler-37b Kepler-37b is an extrasolar planet (exoplanet) orbiting Kepler-37 in the constellation Lyra. it is the smallest planet discovered around a main-sequence star, with a radius slightly greater than that of the Moon and slightly smaller than that o ...

. It was found using the

transit method Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty o ...

, in which the dimming that a planet causes as it crosses in front of its star is measured. Its

stellar flux In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spec ...

is 25 ± 3 times Earth's. It is similar to Mercury.

Physical characteristics

Mass, radius and temperature

Kepler-62c is a

sub-Earth A sub-Earth is a planet "substantially less massive" than Earth and Venus. In the Solar System, this category includes Mercury and Mars. Sub-Earth exoplanets are among the most difficult type to detect because their small sizes and masses produ ...

, an exoplanet with a radius and mass smaller than Earth. It has an

equilibrium temperature The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were a black body being heated only by its parent star. In this model, the presence or absence of an atmosphere (and therefore any greenhouse effect) is ...

of . It has a radius of 0.54 . This is about the size of

, making it the second-smallest exoplanet discovered, with

being the size of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

. However, the mass is currently not known, estimates place an upper limit of <4 , the real mass is expected to be significantly lower than this, say around 0.1 , comparable to the size of Kepler-37b.

Host star

The planet orbits a ( K-type)

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

named

, orbited by a total of five planets. The star has a mass of 0.69 and a radius of 0.64 . It has a temperature of 4925 K and is 7 billion years old. In comparison, 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 ...

is 4.6 billion years old and has a temperature of 5778 K. The star is somewhat metal-poor, with a

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as ...

( e/H of −0.37, or 42% of the solar amount. Its luminosity () is 21% that of the Sun. The star's

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

, 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-62c orbits its host star with an orbital period of 12 days at a distance of about 0.092 AU (compared to the distance of Mercury from the Sun, which is about 0.38 AU). It receives about 25 times more

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when ...

than Earth does from the Sun.

Discovery

In 2009,

's ''

Kepler Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws o ...

'' spacecraft was completing observing stars on its

photometer A photometer is an instrument that measures the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum. Most photometers convert light into an electric current using a photoresistor, ...

, the instrument it uses to detect

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...

events, in which a planet crosses in front of and dims its host star for a brief and roughly regular period of time. In this last test, Kepler observed stars in the

Kepler Input Catalog The Kepler Input Catalog (or KIC) is a publicly searchable database of roughly 13.2 million targets used for the Kepler Spectral Classification Program (SCP) and ''Kepler''. Overview The Kepler SCP targets were observed by the 2MASS project ...

, including Kepler-62; the preliminary light curves were sent to the Kepler science team for analysis, who chose obvious planetary companions from the bunch for follow-up at observatories. Observations for the potential exoplanet candidates took place between 13 May 2009 and 17 March 2012. After observing the respective transits, which for Kepler-62c occurred roughly every 12 days (its orbital period), it was eventually concluded that a planetary body was responsible for the periodic 12-day transits. The discovery, along with the planetary system of the star Kepler-69 were announced on April 18, 2013.

References

{{Sky, 18, 52, 51.06019, +, 45, 20, 59.507 Exoplanets discovered in 2013 Kepler-62 Transiting exoplanets Lyra (constellation) 62c