Kepler-40, formerly known as KOI-428, is an

F-type F-type may refer to: *F-type asteroid, a type of carbonaceous asteroid *F-ATPase, a membrane protein *F-type main-sequence star, a hydrogen-fusing star * F-type Prisons, high-security prisons in Turkey *MG F-type Magna, six-cylinder-engined car pr ...

star in the constellation Cygnus. Kepler-40 is known to host at least one planet, Kepler-40b. The star is approximately 1.5 times more massive than the Sun, and is over two times its size; it was, at upon its discovery, the largest yet discovered with a transiting planet in its orbit. Kepler-40 was first noted as home to a possible transiting object by the Kepler spacecraft; the data on the system was released to the public. A team of French and Swiss scientists used follow-up data to determine the existence of the

Hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...

planet Kepler-40b, and later had their results published in a scientific journal on January 4, 2011.

Observational history

Kepler-40 was first targeted 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 of p ...

spacecraft, an Earth-trailing

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 ...

operation that searches for planets that

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...

, or cross in front of, their host stars. It was labeled a Kepler Object of Interest (KOI) during the satellite's first 33.5 days of operations, which stretched from mid-May to mid-June 2009, because of the detection of a potential transit event. The data collected by Kepler's

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, ...

was publicly released, including data on Kepler-40 and its possible transiting companion. Data on Kepler-40 was analyzed by a team of French and Swiss astronomers, who first tested for

false positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

s. When all obvious false positives were cleared, the science team used the

SOPHIE échelle spectrograph Sophie is a feminine given name, another version of Sophia, from the Greek word for "wisdom". People with the name Born in the Middle Ages * Sophie, Countess of Bar (c. 1004 or 1018–1093), sovereign Countess of Bar and lady of Mousson * Sop ...

at the

Haute-Provence Observatory The Haute-Provence Observatory (OHP, ) is an astronomical observatory in the southeast of France, about 90 km east of Avignon and 100 km north of Marseille. It was established in 1937 as a national facility for French astronomers. Ast ...

in southern France to gather

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

measurements on the star. Collected data was then checked to see if it corresponded with that of a closely orbiting

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

or that of a planet; it was found to be that of a planet, leading to the confirmation of Kepler-40b. After Kepler-40b was confirmed, the French and Swiss science team worked to clarify the stellar parameters its star by analyzing the star's spectrum as collected by SOPHIE. Kepler-40 is the sixth known planetary host star with a

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

of more than 1.8 times that of the Sun. At the time of its discovery, Kepler-40 was the most evolved star known to have a transiting planet. Kepler-40 and its exoplanet were published in the journal ''

Astronomy and Astrophysics ''Astronomy & Astrophysics (A&A)'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. It is operated by an editorial team under the supervision of a board of directors re ...

'' on January 4, 2011, after being submitted on September 15, 2010.

Characteristics

Kepler-40 is an

star that is 1.48 times the

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

of the Sun and 2.13 times its radius. The star has an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 6510 K, making it hotter than the Sun. Its

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

of e/H= 0.10 means that Kepler-40 has 1.26 times as much iron as the Sun does. Kepler-40 was, at the time of its discovery, the largest and most evolved star known to host a transiting planet. It is the sixth known host star with a radius over 1.8 times that of the Sun and a transiting planet, after stars that include

Kepler-5 Kepler-5 is a star located in the constellation Cygnus in the field of view of the Kepler Mission, a NASA project aimed at detecting planets in transit of, or passing in front of, their host stars as seen from Earth. One closely-orbiting ...

and

Kepler-7 Kepler-7 is a star located in the constellation Lyra in the field of view of the Kepler Mission, a NASA operation in search of Earth-like planets. It is home to the fourth of the first five planets that Kepler discovered; this planet, a ...

. Kepler-40 lies approximately 2200

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s (7,200

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s) away from Earth, further than any star (with a known distance) with an exoplanet previously discovered by Kepler. With an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 14.58, it was also dimmer than any star previously recognized by Kepler. Because of its low apparent magnitude, Kepler-40 cannot be seen with the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

Planetary system

Kepler-40b is the first (and only) planet discovered so far in the orbit of Kepler-40. It has a

that is 2.2 times that of Jupiter's, the rough equivalent of 700 Earths. The planet also has a radius that is 1.17 times that of Jupiter and a density of 1.68 grams/cm³. Kepler-40b has an

equilibrium temperature The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were in radiative equilibrium, typically under the assumption that it radiates as a black body being heated only by its parent star. In this model, th ...

of 1620 K, over six times hotter than the equilibrium temperature of Earth. It orbits its star every 6.87 days at a distance of 0.081 AU.

References

{{Stars of Cygnus Planetary systems with one confirmed planet Cygnus (constellation) Planetary transit variables 428 F-type subgiants