Kepler-11f
Encyclopedia
Kepler-11f is an exoplanet
(extrasolar planet) discovered in the orbit of the sunlike star Kepler-11
by NASA
's Kepler spacecraft, which searches for planets that transit (cross in front of) their host stars. Kepler-11f is the sixth planet from its star, orbiting one fourth of the distance (.25 AU
) of the Earth from the Sun every 47 days. It is the furthest of the first five planets in the system, as compared to the outlying Kepler-11g. Kepler-11f is the least massive of Kepler-11's six planets, at nearly twice the mass of Earth; it is about 2.6 times the radius of Earth. Along with planets d and e and unlike the two inner planets in the system, Kepler-11f has a density lower than that of water and comparable to that of Saturn
. This suggests that Kepler-11f has a significant hydrogen–helium atmosphere. According to NASA, Kepler-11f and its sister planets form the most compact system yet discovered. The Kepler-11 planets constitute the first system discovered with more than three transiting planets. Kepler-11f was announced to the public on February 2, 2011 after follow-up investigations at several observatories.
-157 when it was first flagged for a transit event, is the planet's host star, and it is included in the planet's name to denote that. Because Kepler-11f was discovered with five other planets, the planets of Kepler-11 were sorted by distance from the host star; thus, since Kepler-11f is the fifth planet from its star, it was given the letter "f." The name "Kepler" is derived from the Kepler satellite, a NASA
Earth-trailing spacecraft that constantly observes a small patch of sky between the constellations Cygnus
and Lyra for stars that are transited by, in particular, terrestrial planet
s. As these planets cross in front of their host stars with respect to Earth, a small and periodic dip in the star's brightness occurs; this dip is noted by the spacecraft and tagged for future study. Scientists then analyze the transit event more carefully to verify if the planet actually exists and to gather information on the planet's orbit and composition (if possible).
Follow-up observations were conducted at observatories at the W.M. Keck Observatory's Keck 1 telescope in Hawaii; the Shane
and Hale
telescopes in California; the Harlan J. Smith
and Hobby-Eberly
telescopes in Texas; telescopes at the WIYN
(including MMT
) and Whipple
observatories in Arizona; and the Nordic Optical Telescope
in the Canary Islands. The Spitzer Space Telescope
was also used. Kepler-11f is part of the first system in which more than three transiting planets were discovered. According to NASA, Kepler-11's system is also the most compact and the flattest system yet discovered, surpassing even the Solar System. After the planets were confirmed, Kepler-11f and its sister planets were announced to the public on February 2, 2011. Analysis of the planets and study results were published the next day in the journal Nature
.
s away in the Cygnus constellation. It has 95% the mass
and 110% the radius of the Sun. Its mass and radius, combined with an approximate iron content (metallicity
) of 0 and effective temperature
of 5680 K, makes the star very similar to the Sun, though slightly more diffuse and slightly cooler. However, the star is approximately 1.74 times the age of the Sun, and is estimated to have existed for eight billion years. Kepler-11 has six known planets in orbit: Kepler-11b
, Kepler-11c
, Kepler-11d
, Kepler-11e
, Kepler-11f, and Kepler-11g. Kepler-11's five inner planets orbit closely to their host star, and their orbits would fit within that of Mercury
's.
With an apparent magnitude
of 14.2, Kepler-11 cannot be seen with the naked eye
.
, the least massive of the six planets discovered in the orbit of Kepler-11, although the planet's mass may range from 1.1 to 4.5, or from approximately that of Earth's mass to that of Kepler-10b
, a rather large confidence interval
. Its radius
is the second smallest of the six planets discovered in the system at 2.61 times the radius of Earth. Kepler-11f has a density of about 0.7 grams/cm3, comparable to that of the Solar System's least dense planet, Saturn. Kepler-11f is the fifth planet from Kepler-11, orbiting its host star every 46.68876 days at a distance of .25 AU
. Its eccentricity
, or the irregularity of the planet's orbit, is unknown. In comparison, Mercury
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11f has an orbital inclination
of 89.4°; it can be seen almost edge-on with respect to Earth. Its surface equilibrium temperature is 544 K, over twice the surface equilibrium temperature of Jupiter
and about two-thirds the surface temperature of Venus
.
Kepler-11f's low density, characteristic of the outer planets of the system, suggests that a large hydrogen and helium atmosphere is present on these planets. This low density is not shared by the planets Kepler-11b
and Kepler-11c
because the solar wind
has reduced their atmospheres to a thin layer. The planets accreted such large atmospheres because they formed within the first few million years of the system's existence, when a protoplanetary disk
was still present.
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...
(extrasolar planet) discovered in the orbit of the sunlike 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 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...
's Kepler spacecraft, which searches for planets that transit (cross in front of) their host stars. Kepler-11f is the sixth planet from its star, orbiting one fourth of the distance (.25 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
) of the Earth from the Sun every 47 days. It is the furthest of the first five planets in the system, as compared to the outlying Kepler-11g. Kepler-11f is the least massive of Kepler-11's six planets, at nearly twice the mass of Earth; it is about 2.6 times the radius of Earth. Along with planets d and e and unlike the two inner planets in the system, Kepler-11f has a density lower than that of water and comparable to that of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. This suggests that Kepler-11f has a significant hydrogen–helium atmosphere. According to NASA, Kepler-11f and its sister planets form the most compact system yet discovered. The Kepler-11 planets constitute the first system discovered with more than three transiting planets. Kepler-11f was announced to the public on February 2, 2011 after follow-up investigations at several observatories.
Name and discovery
Kepler-11, known as KOIKepler 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 when it was first flagged for a transit event, is the planet's host star, and it is included in the planet's name to denote that. Because Kepler-11f was discovered with five other planets, the planets of Kepler-11 were sorted by distance from the host star; thus, since Kepler-11f is the fifth planet from its star, it was given the letter "f." The name "Kepler" is derived from the Kepler satellite, 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...
Earth-trailing spacecraft that constantly observes a small patch of sky between the constellations Cygnus
Cygnus (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...
and Lyra for stars that are transited by, in particular, 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. As these planets cross in front of their host stars with respect to Earth, a small and periodic dip in the star's brightness occurs; this dip is noted by the spacecraft and tagged for future study. Scientists then analyze the transit event more carefully to verify if the planet actually exists and to gather information on the planet's orbit and composition (if possible).
Follow-up observations were conducted at observatories at the W.M. Keck Observatory's Keck 1 telescope in Hawaii; the Shane
C. Donald Shane telescope
The C. Donald Shane telescope is a reflecting telescope located at the Lick Observatory in California. It was named after astronomer C. Donald Shane in 1978, who led the effort to acquire the necessary funds from the California Legislature, and who then oversaw the telescope's construction...
and Hale
Hale telescope
The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in California, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning...
telescopes in California; the Harlan J. Smith
Harlan J. Smith Telescope
The Harlan J. Smith Telescope is a 2.7m telescope located at the McDonald Observatory, in Texas, in the United States. This telescope is one of several research telescopes that are part of the University of Texas at Austin observatory perched atop Mount Locke in the Davis Mountains of west Texas...
and Hobby-Eberly
Hobby-Eberly Telescope
The Hobby-Eberly Telescope is a 9.2-meter aperture telescope located at the McDonald Observatory. It combines a number of features that differentiate it from most telescope designs, resulting in greatly lowered construction costs...
telescopes in Texas; telescopes at the WIYN
WIYN Consortium
WIYN Consortium consists of the University of Wisconsin–Madison , Indiana University , Yale University , and the National Optical Astronomy Observatories...
(including MMT
MMT Observatory
The MMT Observatory is an astronomical observatory on the site of Fred Lawrence Whipple Observatory . The Whipple observatory complex is located on Mount Hopkins, Arizona, USA in the Santa Rita Mountains...
) and Whipple
Fred Lawrence Whipple Observatory
The Fred Lawrence Whipple Observatory is an astronomical observatory owned and operated by the Smithsonian Astrophysical Observatory and is their largest field installation outside of their main site in Cambridge, MA...
observatories in Arizona; and the Nordic Optical Telescope
Nordic Optical Telescope
The Nordic Optical Telescope is an astronomical telescope located at Roque de los Muchachos Observatory, La Palma in the Canary Islands. First light came in 1988, with regular observing beginning in 1989. It is funded by Denmark, Sweden, Iceland, Norway and Finland...
in the Canary Islands. 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...
was also used. Kepler-11f is part of the first system in which more than three transiting planets were discovered. According to NASA, Kepler-11's system is also the most compact and the flattest system yet discovered, surpassing even the Solar System. After the planets were confirmed, Kepler-11f and its sister planets were announced to the public on February 2, 2011. Analysis of the planets and study results were published the next day in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
.
Host star
Kepler-11 is a G-type star, much like the Sun is, and is located 613 parsecParsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s away in the Cygnus constellation. It has 95% the mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
and 110% the radius of the Sun. Its mass and radius, combined with an approximate iron content (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...
) of 0 and effective temperature
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...
of 5680 K, makes the star very similar to the Sun, though slightly more diffuse and slightly cooler. However, the star is approximately 1.74 times the age of the Sun, and is estimated to have existed for eight billion years. Kepler-11 has six known planets in orbit: Kepler-11b
Kepler-11b
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...
, 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, and Kepler-11g. Kepler-11's five inner planets orbit closely to their host star, and their orbits would fit within that of 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...
's.
With 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, Kepler-11 cannot be seen 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-11f is, at 2.3 times the mass of EarthEarth 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....
, the least massive of the six planets discovered in the orbit of Kepler-11, although the planet's mass may range from 1.1 to 4.5, or from approximately that of Earth's mass to that of Kepler-10b
Kepler-10b
Kepler-10b is the first confirmed terrestrial planet to have been discovered outside the Solar System. Discovered after several months of data collection during the course of the NASA-directed Kepler Mission, which aims to discover Earth-like planets crossing in front of their host stars, the...
, a rather large confidence interval
Confidence interval
In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...
. Its radius
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...
is the second smallest of the six planets discovered in the system at 2.61 times the radius of Earth. Kepler-11f has a density of about 0.7 grams/cm3, comparable to that of the Solar System's least dense planet, Saturn. Kepler-11f is the fifth planet from Kepler-11, orbiting its host star every 46.68876 days at a distance of .25 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. Its eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
, or the irregularity of the planet's orbit, is unknown. In comparison, 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...
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11f has an orbital 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 89.4°; it can be seen almost edge-on with respect to Earth. Its surface equilibrium temperature is 544 K, over twice the surface equilibrium temperature of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
and about two-thirds the surface temperature of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
.
Kepler-11f's low density, characteristic of the outer planets of the system, suggests that a large hydrogen and helium atmosphere is present on these planets. This low density is not shared by the planets Kepler-11b
Kepler-11b
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...
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...
because the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
has reduced their atmospheres to a thin layer. The planets accreted such large atmospheres because they formed within the first few million years of the system's existence, when a protoplanetary disk
Protoplanetary disk
A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star...
was still present.