Kepler-11b
Encyclopedia
Kepler-11b is an exoplanet
discovered in the orbit of the star Kepler-11
by the Kepler spacecraft, a NASA
-led mission to discover Earth-like planets
. Kepler-11b is four times more massive and twice as large as Earth, but it has a lighter density estimated at a little over half Earth's, and is therefore most likely not of Earth-like composition. Kepler-11b is the hottest of the six planets in the Kepler-11 system, and orbits more closely to Kepler-11 than the other planets in the system. Kepler-11b, along with its five counterparts, form the first discovered planetary system with more than three transiting planets—the most densely packed known planetary system. The system is also the flattest known planetary system. The discovery of this planet and its five sister planets was announced on February 2, 2011, after follow-up investigations.
. As the discovery of Kepler-11b was announced simultaneously with those of other planets, Kepler-11b was given the designation b because it was the innermost of the six announced planets. The host star, Kepler-11, was named for the Kepler Mission
that flagged it as host to several potential transit events under the name KOI
-157. The Kepler satellite is a NASA
-run space telescope that is tasked with the discovery of terrestrial planet
s that transit, or cross in front of, their host stars as seen from Earth. These transits cause fluctuations in the host star's brightness; these changes may suggest the presence of a planet, which can then be verified by follow-up observations.
Ground-based telescopes in California, Hawaii, the Canary Islands, Arizona, and Texas, as well as the Spitzer Space Telescope
, were used to conduct these follow-up observations and verify Kepler-11b's existence. In particular, the detection of an orbital resonance
effect between Kepler-11b and Kepler-11c confirmed the find. Kepler-11b's discovery was announced to the public on February 2, 2011. It is part of the first system discovered with more than three transiting planets, and is also part of the most compact and flat system yet discovered. Kepler-11's planetary system is the second known system to have multiple transiting planets, surpassing the three confirmed planets (two transiting) orbiting the star Kepler-9
.
that has a mass of 0.95 (± 0.1) Msun
and a radius of 1.1 (± 0.1) Rsun. In other words, Kepler-11 is approximately 5% less massive and 10% wider than the Sun. The star's metallicity
is 0 (± 0.1), meaning that the level of iron (and, presumably, other elements) in the star is almost the same as that of the Sun. Metallicity plays an important role in planetary systems, and stars with higher metallicity are more likely to have planets detected around them. This may be because the higher metallicity provides more material with which to quickly build planets into gas giants or because the higher metallicity increases planet migration towards the host star, making the planet easier to detect. The star has five other known planets in orbit: Kepler-11c
, Kepler-11d
, Kepler-11e
, Kepler-11f
, and Kepler-11g. The first five planets in the system are all able to fit within the orbit of planet Mercury
, while Kepler-11g orbits further out.
Kepler-11 has an apparent magnitude
of 14.2. It is too dim to see from Earth with the naked eye
.
es and 1.97 Earth radii
, making it over four times as massive and nearly twice as wide as Earth. While the radius of Kepler-11b is fairly well known (with a range of likely radii between 1.78 and 2.16 Earth radii), the mass is not as well constrained, with a range between 2.3 and 6.5 Earth masses. The mass is determined using transit timing variations of Kepler-11c
, and is limited by the quality of the data. Kepler-11b is the closest planet to its host star in the Kepler-11 planetary system. With an estimated density of 3.1 g/cm3, Kepler-11b is comparable to the moon
, and is significantly denser than the solar system's gas giants
but less dense than the terrestrial planets. Its intermediate density suggests that it is not of Earth-like composition, yet is nonetheless composed mostly of elements heavier than helium. The planet's effective temperature is 900 K, and is thus the hottest of the planets discovered in the Kepler-11 system. Kepler-11b orbits its host star every 10.30375 days at a distance of .091 AU
. Planet Mercury
, in comparison, orbits the Sun every 87.97 days from a distance of .387 AU. Kepler-11b's inclination
of 88.5° means that it deviates slightly from the orbital plane, but it does so more than the other five planets with which Kepler-11b was discovered.
Kepler-11b and Kepler-11c
orbit Kepler-11 with a strong orbital resonance
, which gravitationally tugs the planets into stable orbits at a set ratio. The ratio of the resonance between Kepler-11b and c is 5:4.
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
discovered in the orbit of the star Kepler-11
Kepler-11
Kepler-11 is a sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,000 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars...
by the Kepler spacecraft, a NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
-led mission to discover Earth-like planets
Terrestrial planet
A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun...
. Kepler-11b is four times more massive and twice as large as Earth, but it has a lighter density estimated at a little over half Earth's, and is therefore most likely not of Earth-like composition. Kepler-11b is the hottest of the six planets in the Kepler-11 system, and orbits more closely to Kepler-11 than the other planets in the system. Kepler-11b, along with its five counterparts, form the first discovered planetary system with more than three transiting planets—the most densely packed known planetary system. The system is also the flattest known planetary system. The discovery of this planet and its five sister planets was announced on February 2, 2011, after follow-up investigations.
Naming and discovery
Kepler-11b is named in two parts. The first part of its name is derived from the fact that it orbits the star Kepler-11Kepler-11
Kepler-11 is a sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,000 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars...
. As the discovery of Kepler-11b was announced simultaneously with those of other planets, Kepler-11b was given the designation b because it was the innermost of the six announced planets. The host star, Kepler-11, was named for the Kepler Mission
Kepler Mission
The Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft is named in honor of the 17th-century German astronomer Johannes Kepler...
that flagged it as host to several potential transit events under the name KOI
Kepler Object of Interest
A Kepler Object of Interest is a star observed by the Kepler spacecraft which is suspected of hosting one or more transiting planets. KOIs come from a master list of 150,000 stars which itself is generated from the Kepler Input Catalog . A KOI shows a periodic dimming, indicative of an unseen...
-157. The Kepler satellite is a NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
-run space telescope that is tasked with the discovery of terrestrial planet
Terrestrial planet
A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun...
s that transit, or cross in front of, their host stars as seen from Earth. These transits cause fluctuations in the host star's brightness; these changes may suggest the presence of a planet, which can then be verified by follow-up observations.
Ground-based telescopes in California, Hawaii, the Canary Islands, Arizona, and Texas, as well as the Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
, were used to conduct these follow-up observations and verify Kepler-11b's existence. In particular, the detection of an orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
effect between Kepler-11b and Kepler-11c confirmed the find. Kepler-11b's discovery was announced to the public on February 2, 2011. It is part of the first system discovered with more than three transiting planets, and is also part of the most compact and flat system yet discovered. Kepler-11's planetary system is the second known system to have multiple transiting planets, surpassing the three confirmed planets (two transiting) orbiting the star Kepler-9
Kepler-9
Kepler-9 is a sunlike star in the constellation Lyra. It is situated in the Kepler Mission's field of view. Kepler-9 has three confirmed extrasolar planets, all discovered by Kepler using the transit method. The discovery of the first two planets was announced on August 26, 2010, and of the third...
.
Host star
Kepler-11 is a sunlike star in the constellation CygnusCygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
that has a mass of 0.95 (± 0.1) Msun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
and a radius of 1.1 (± 0.1) Rsun. In other words, Kepler-11 is approximately 5% less massive and 10% wider than the Sun. The star's metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
is 0 (± 0.1), meaning that the level of iron (and, presumably, other elements) in the star is almost the same as that of the Sun. Metallicity plays an important role in planetary systems, and stars with higher metallicity are more likely to have planets detected around them. This may be because the higher metallicity provides more material with which to quickly build planets into gas giants or because the higher metallicity increases planet migration towards the host star, making the planet easier to detect. The star has five other known planets in orbit: Kepler-11c
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its parent star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c...
, Kepler-11d
Kepler-11d
Kepler-11d is an exoplanet discovered in the orbit of the sun-like star Kepler-11. It is named for the telescope that discovered it, a NASA spacecraft named Kepler that is designed to detect Earth-like planets by measuring small dips in the brightness of their host stars as the planets cross in front...
, Kepler-11e
Kepler-11e
Kepler-11e is an exoplanet discovered in the orbit of the sunlike star Kepler-11. It is the fourth of six planets around Kepler-11 discovered by NASA's Kepler spacecraft. Kepler-11e was found by using the transit method, in which a the dimming effect that a planet causes as it crosses in front of...
, Kepler-11f
Kepler-11f
Kepler-11f is an exoplanet discovered in the orbit of the sunlike star Kepler-11 by NASA's Kepler spacecraft, which searches for planets that transit their host stars. Kepler-11f is the sixth planet from its star, orbiting one fourth of the distance of the Earth from the Sun every 47 days...
, and Kepler-11g. The first five planets in the system are all able to fit within the orbit of planet Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, while Kepler-11g orbits further out.
Kepler-11 has an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 14.2. It is too dim to see from Earth with the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
.
Characteristics
Kepler-11b is estimated to be 4.3 Earth massEarth mass
Earth mass is the unit of mass equal to that of the Earth. 1 M⊕ = 5.9722 × 1024 kg. Earth mass is often used to describe masses of rocky terrestrial planets....
es and 1.97 Earth radii
Earth radius
Because the Earth is not perfectly spherical, no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km...
, making it over four times as massive and nearly twice as wide as Earth. While the radius of Kepler-11b is fairly well known (with a range of likely radii between 1.78 and 2.16 Earth radii), the mass is not as well constrained, with a range between 2.3 and 6.5 Earth masses. The mass is determined using transit timing variations of Kepler-11c
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its parent star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c...
, and is limited by the quality of the data. Kepler-11b is the closest planet to its host star in the Kepler-11 planetary system. With an estimated density of 3.1 g/cm3, Kepler-11b is comparable to the moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, and is significantly denser than the solar system's gas giants
Gas Giants
Gas Giants were a pop rock band from Tempe, Arizona, formed as a successor project to the Gin Blossoms. The group was known as The Pharaohs when they formed in 1997, but changed their name after their label, A&M Records, merged with Universal Records and the band changed hands, re-signing with...
but less dense than the terrestrial planets. Its intermediate density suggests that it is not of Earth-like composition, yet is nonetheless composed mostly of elements heavier than helium. The planet's effective temperature is 900 K, and is thus the hottest of the planets discovered in the Kepler-11 system. Kepler-11b orbits its host star every 10.30375 days at a distance of .091 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. Planet Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, in comparison, orbits the Sun every 87.97 days from a distance of .387 AU. Kepler-11b's inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of 88.5° means that it deviates slightly from the orbital plane, but it does so more than the other five planets with which Kepler-11b was discovered.
Kepler-11b and Kepler-11c
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its parent star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c...
orbit Kepler-11 with a strong orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
, which gravitationally tugs the planets into stable orbits at a set ratio. The ratio of the resonance between Kepler-11b and c is 5:4.