__NOTOC__ Kepler-5b is one of the first five planets 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, succeeding t ...

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. It is a

Hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temp ...

that orbits a

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

star that is more massive, larger, and more diffuse than the Sun is. Kepler-5 was first flagged as the location of a possibly transiting planet, and was reclassified as a Kepler Object of Interest until follow-up observations confirmed the planet's existence and many of its characteristics. The planet's discovery was announced at a meeting of the

American Astronomical Society The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the adv ...

on January 4, 2010. The planet has approximately twice the mass of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

, and is about 1.5 times larger. It is also fifteen times hotter than Jupiter. Kepler-5b orbits Kepler-5 every 3.5 days at a distance of approximately 0.051 AU (7.6 Gm).

Observational history

The

spacecraft's first days of science activity revealed a series of transit events, in which some body (such as a planet) crosses in front of, and therefore dims, its host star. Such objects were taken from 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 ...

and reclassified as

Kepler Objects of Interest 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 ...

. Kepler-5 was one of these objects of interest, and was given the designation KOI-18. After the stellar parameters were established, the Kepler science team ran models and fits to ensure that Kepler-5's transit event was not a

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 result ...

, such as an

eclipsing binary A binary star 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 using a telescope as separate stars, in wh ...

star. Once the planetary nature of Kepler-5b was established, the Kepler team searched for the planet's

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

behind its star, hoping to find the temperature on its day side. They found both, and were able to set the

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 the planet. The use of

speckle imaging Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("'' ...

using

adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...

at the WIYN Observatory in Arizona and the

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in California isolated the starlight of Kepler-5 from background stars. Use of the Fibre-fed Echelle Spectrograph (FIES) at the

Nordic Optical Telescope The Nordic Optical Telescope (NOT) is an astronomical telescope located at Roque de los Muchachos Observatory, La Palma in the Canary Islands. The telescope saw first light in 1988, and was officially inaugurated during September 1989. Regular o ...

on the Canary Islands on June 4, 2009 provided data that was used to determine the star's

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

. The

W.M. Keck Observatory The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...

High Resolution Echelle Spectrometer The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...

(HIRES), which was used on June 3–6, 2009, and July 2–4, 2009, determined

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

measurements for the star, which helped to further define stellar parameters. Kepler-5 has, as considered by the Kepler team, the potential for use in the study of planets in extreme conditions; its high temperature, large size, and short

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

contribute to the aforementioned conditions. The findings of the Kepler team, which also included planets Kepler-4b,

Kepler-6b __NOTOC__ Kepler-6b is an extrasolar planet in the orbit of the unusually metal-rich Kepler-6, a star in the field of view of the NASA-operated Kepler spacecraft, which searches for planets that cross directly in front of, or transit, their host ...

Kepler-7b Kepler-7b is one of the first five exoplanets to be confirmed by NASA's Kepler spacecraft, and was confirmed in the first 33.5 days of Kepler's science operations. It orbits a star slightly hotter and significantly larger than the Sun that is exp ...

, and Kepler-8b, were announced at the 215th meeting of the

of January 4, 2010.

Host star

Kepler-5 is a

in the Cygnus constellation that is expected to soon deplete its hydrogen stores in the core and begin fusing hydrogen in the shell region surrounding the core. The star is 1.374 times the

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

of the Sun (another model suggests that Kepler-5 as a mass of 1.21 times that of the Sun), although it is more diffuse at 1.793 times the Sun's

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

. The star's

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 ...

is measured to be at e/H= 0.04, which means that Kepler-5 has 1.10 times the levels of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

as the Sun does. 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 ...

is 13.4, meaning that it cannot be seen with the unaided eye.

Characteristics

Kepler-5b is a

with a mass that is 2.114 times that of Jupiter and a radius of 1.431 times Jupiter's radius. This also means that Kepler-5b is not very dense. The planet's measured density is 0.894 grams/cm³, less than that of pure water and comparable only to the density of Saturn, which is approximately 0.69 grams/cm³. The planet has an

of 1868 K, making it fifteen times hotter than Jupiter. Kepler-5b orbits its host star every 3.5485 days at a mean distance of 0.05064 AU. In addition, with an

orbital inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

of 86.3º, Kepler-5b orbits Kepler-5 almost edge-on with respect to Earth. In comparison, planet

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

orbits the Sun at a distance of 0.387 AU every 87.97 days. The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to 2169 K.A Comprehensive Study of Kepler Phase Curves and Secondary Eclipses:Temperatures and Albedos of Confirmed Kepler Giant Planets
/ref>

References

External links

Discovery of the Transiting Planet Kepler-5b
{{Sky, 19, 57, 37.7, +, 44, 2, 6.2 Exoplanets discovered in 2010 Hot Jupiters Giant planets Transiting exoplanets Cygnus (constellation) 5b