Kepler-11d
Encyclopedia
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. This process, known as the transit method, was used to note the presence of six planets in orbit around Kepler-11, of which Kepler-11d is the third from its star. Kepler-11d orbits Kepler-11 well within the orbit of Mercury
approximately every 23 days. The planet is approximately six times more massive than the Earth, and has a radius that is three and a half times larger than that of Earth's. It is, however, far hotter than Earth is. Its low density, comparable to that of Saturn
, suggests that Kepler-11d has a large hydrogen–helium atmosphere. Kepler-11d was announced with its five sister planets on February 2, 2011 after extensive follow-up studies.
. Because Kepler-11d was announced at the same time as the five other planets in the system, their names are sorted by their distances from the host star; thus, because Kepler-11d is the third planet from Kepler-11, it was given the designation d. Kepler-11 was named for the Kepler spacecraft, a NASA
Earth-trailing satellite purposed with discovering Earth-like planets
in a small area of the sky between the constellations Cygnus
and Lyra by observing planets that transit, or cross in front of, their host stars with respect to Earth. The transit causes the star's brightness to dim slightly and at a regular rate, a phenomenon that the Kepler satellite notes till future study can prove or disprove the existence of a planetary body. Kepler-11d was flagged by Kepler-11, given the designation KOI
-157.
Required follow-up observations were conducted at the Hale
and Shane
telescopes in California; the W.M. Keck Observatory's Keck I telescope in Hawaii; telescopes at the WIYN
, Whipple
, and MMT
observatories in Arizona; and the Hobby-Eberly
and Harlan J. Smith
telescopes of west Texas. Additionally, the Spitzer Space Telescope
was used. Kepler-11d, along with its five sister planets, were announced to the public on February 2, 2011. Its discovery paper was published in the journal Nature
the next day.
is a G-type star in the Cygnus constellation. With a mass of .95 Msun
, a radius of 1.1 Rsun, a measured metallicity
of 0, and an effective temperature
of 5680 K, Kepler-11 is near in mass (95% of Sun), radius (110% of Sun), and iron content as the Sun. Metallicity has been observed to play a major role determining the type of planet a star forms. As metal-rich gas clouds tend to cause planetary cores to aggregate to a gravitationally prominent size while primordial gases still exist in the system, gas giants tend to form under such conditions. It is also slightly cooler than the Sun. However, it is estimated to be eight (± two) billion years old, far older than the Sun is. Kepler-11 is host to five other planets other than Kepler-11d: Kepler-11b
, Kepler-11c
, Kepler-11e
, Kepler-11f
, and Kepler-11g. The first five planets in the system have orbits that would collectively fit inside the orbit of planet Mercury
, while Kepler-11g orbits at a considerably further distance in relation to the orbits of its inner counterparts.
At a distance of 613 parsec
s, Kepler-11d has an apparent magnitude
of 14.2. It is, thus, not visible with the naked eye
.
and a radius of 3.43 RE
, making it some six times more massive than Earth with nearly three and a half times the radius. With a density of .9 grams/cm3, Kepler-11d's density is less than that of water and comparable to that of the gas giant Saturn
. This suggests that, unlike its sister planets Kepler-11b
and Kepler-11c
, which are closer to their host star, Kepler-11d has maintained a large atmosphere that is most likely composed to hydrogen and helium. Kepler-11d has an equilibrium temperature of 692 K, nearly 2.7 times the equilibrium temperature of Earth. Kepler-11d orbits at a mean distance of .159 AU
from its host star and completes an orbit
every 22.68719 days, making it the third planet from Kepler-11. In comparison, planet Mercury
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11d has an orbital inclination
of 89.3°. Thus, Kepler-11d is almost exactly edge on with respect to Earth.
The presence of large quantities of hydrogen and helium on Kepler-11d, Kepler-11e
, and Kepler-11f
suggest that these planets formed within the first few million years of the system's existence, when gas could still be captured from the forming protoplanetary disc.
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 sun-like 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...
. It is named for the telescope that discovered it, 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...
spacecraft named Kepler that is designed to detect 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...
by measuring small dips in the brightness of their host stars as the planets cross in front. This process, known as the transit method, was used to note the presence of six planets in orbit around Kepler-11, of which Kepler-11d is the third from its star. Kepler-11d orbits Kepler-11 well within the orbit 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...
approximately every 23 days. The planet is approximately six times more massive than the Earth, and has a radius that is three and a half times larger than that of Earth's. It is, however, far hotter than Earth is. Its low density, 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,...
, suggests that Kepler-11d has a large hydrogen–helium atmosphere. Kepler-11d was announced with its five sister planets on February 2, 2011 after extensive follow-up studies.
Name and discovery
As with all exoplanets, Kepler-11d is named first for its host 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...
. Because Kepler-11d was announced at the same time as the five other planets in the system, their names are sorted by their distances from the host star; thus, because Kepler-11d is the third planet from Kepler-11, it was given the designation d. Kepler-11 was named for 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...
Earth-trailing satellite purposed with discovering 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...
in a small area of the 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 by observing planets that transit, or cross in front of, their host stars with respect to Earth. The transit causes the star's brightness to dim slightly and at a regular rate, a phenomenon that the Kepler satellite notes till future study can prove or disprove the existence of a planetary body. Kepler-11d was flagged by Kepler-11, given the designation 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.
Required follow-up observations were conducted at the 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...
and 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...
telescopes in California; the W.M. Keck Observatory's Keck I telescope in Hawaii; telescopes at the WIYN
WIYN Observatory
The WIYN Observatory is owned and operated by the WIYN Consortium. Its telescope, a 3.5-meter instrument, is the newest and second largest telescope on Kitt Peak in Arizona...
, 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...
, and 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...
observatories in Arizona; and the 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...
and 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...
telescopes of west Texas. Additionally, 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 used. Kepler-11d, along with its five sister planets, were announced to the public on February 2, 2011. Its discovery paper was published 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...
the next day.
Host 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...
is a G-type star in the Cygnus constellation. With a mass of .95 Msun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
, a radius of 1.1 Rsun, a measured 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 an 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, Kepler-11 is near in mass (95% of Sun), radius (110% of Sun), and iron content as the Sun. Metallicity has been observed to play a major role determining the type of planet a star forms. As metal-rich gas clouds tend to cause planetary cores to aggregate to a gravitationally prominent size while primordial gases still exist in the system, gas giants tend to form under such conditions. It is also slightly cooler than the Sun. However, it is estimated to be eight (± two) billion years old, far older than the Sun is. Kepler-11 is host to five other planets other than Kepler-11d: 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-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 have orbits that would collectively fit inside 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 at a considerably further distance in relation to the orbits of its inner counterparts.
At a distance of 613 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s, Kepler-11d 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, thus, not visible 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-11d has a mass of 6.1 MEEarth 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....
and a radius of 3.43 RE
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 some six times more massive than Earth with nearly three and a half times the radius. With a density of .9 grams/cm3, Kepler-11d's density is less than that of water and comparable to that of the gas giant 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, unlike its sister 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...
, which are closer to their host star, Kepler-11d has maintained a large atmosphere that is most likely composed to hydrogen and helium. Kepler-11d has an equilibrium temperature of 692 K, nearly 2.7 times the equilibrium temperature of Earth. Kepler-11d orbits at a mean distance of .159 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from its host star and completes an orbit
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
every 22.68719 days, making it the third planet from Kepler-11. In comparison, 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...
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11d 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 89.3°. Thus, Kepler-11d is almost exactly edge on with respect to Earth.
The presence of large quantities of hydrogen and helium on Kepler-11d, 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...
, and 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...
suggest that these planets formed within the first few million years of the system's existence, when gas could still be captured from the forming protoplanetary disc.