Extrasolar Planets
Encyclopaediadata
/td> Kepler-452 is a

G-type main-sequence star A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main-sequence star (luminosity class V) of spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective temp ...

located about 1,800

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s 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 Cygnus constellation. Although similar in temperature 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 ...

, it is 20% brighter, 3.7% more massive and 11% larger. Alongside this, the star is approximately six billion years old and possesses a high

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 a ...

. Thus, Kepler-452 can be considered a

solar twin Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. " solar panels") ** Solar calendar, a calendar whose dates indica ...

, although it could be considered a solar analog due to its age.

Nomenclature and history

Prior to Kepler observation, Kepler-452 had the

2MASS The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and ...

catalogue number 2MASS 19440088+4416392. In the Kepler Input Catalog, it has the designation of KIC 8311864. When it was found to have a transiting planet candidate, it was given the Kepler object of interest number of KOI-7016. Planetary candidates were detected around the star 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 ...

Kepler Mission 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 ...

, a mission tasked with discovering planets in

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 ...

around their stars. The transit method that Kepler uses involves detecting dips in brightness of stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of

, although other phenomena can also be responsible which is why the term "planetary candidate" is used. Following the acceptance of the discovery paper, the Kepler team referred to the star as Kepler-452, which is the normal procedure for naming exoplanets discovered by the spacecraft. Hence, this is the name usually used by the public to refer to the star and its planet. Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01", ".02", and so on, after the star's name, in the order of discovery. If planet candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest. Following these rules, there was only one candidate planet detected, with an orbital period of 384.843 days. The name Kepler-452 derives directly from the fact that the star is the catalogued 452nd star discovered by ''Kepler'' to have confirmed planets. The designation ''b'', derives from the order of discovery. The designation of ''b'' is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of Kepler-452, there was only one planet, so only the letter ''b'' is used.

Stellar characteristics

Kepler-452 is a G-type star that is approximately 104% the mass of and 111% the radius of the

. It has a temperature of 5757 K and is roughly 6 billion years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K. The star is metal-rich, with a

( Fe/ H) of about 0.21, or about 162% of the amount of iron and other heavier metals found in the Sun. The star's luminosity is somewhat normal for a star like Kepler-452, with a luminosity of around 120% of that of the solar luminosity. 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 li ...

, or how bright it appears from Earth's perspective, is 13.426. Therefore, it is too dim to be seen with the naked eye.

Planetary system

The star hosts one confirmed

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 ...

Kepler-452b Kepler-452b (sometimes quoted to be an ''Earth 2.0'' or ''Earth's Cousin'' based on its characteristics; also known by its Kepler Object of Interest designation ''KOI-7016.01'') is a super-Earth exoplanet orbiting within the inner edge of the ha ...

, discovered in July 2015 by the ''

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. This planet is mostly known for its characteristics similar to Earth, most notably its size, orbit and stellar flux. It is the first potentially rocky

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 ...

planet discovered orbiting 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. Kas ...

and the

abiogenesis In biology, abiogenesis (from a- 'not' + Greek bios 'life' + genesis 'origin') or the origin of life is the natural process by which life has arisen from non-living matter, such as simple organic compounds. The prevailing scientific hypothes ...

zone of a star very similar to the

. It may even have a surface temperature similar to that of Earth (the planet 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 approximately (Earth's equilibrium temperature is only 10 K cooler than this). However, its star is 6 billion years old (roughly 1.5 billion years older than the Sun). Due to this, Kepler-452b is receiving roughly 10% more stellar radiation than the Earth does today. If Kepler-452b is a rocky planet, it might be subject to 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 ...

. However, because of its mass (estimated to be about 5 ), it may be able to prevent succumbing to the runaway greenhouse for a limited amount of time (at most about 500 million years). Nevertheless, the planet is one of the most Earth-like planets discovered so far by the ''Kepler'' team. Both the Earth and Kepler-452b are at just the right distances from their stars so that water can be liquid, at a temperature between 0 °C and 100 °C.

Sun comparison

This table compares the Sun to Kepler-452.

Footnotes

References

{{Stars of Cygnus J19440088+4416392 Cygnus (constellation) G-type main-sequence stars 7016 Planetary systems with one confirmed planet TIC objects