Kepler-9d
Encyclopedia
Kepler-9d, formerly known as KOI-377.03, is a planet in orbit around the sunlike star Kepler-9
. Initially discovered by Kepler spacecraft, a terrestrial planet
-searching satellite built and operated by NASA
, Kepler-9d is most likely a Super-Earth, with an estimated radius approximately 60% larger than that of Earth's, although its exact mass cannot be determined. Kepler-9d orbits Kepler-9 every 1.56 days at a distance of .0273 AU
from its star, an extremely close distance. Although Kepler-9d is the closest planet to its star in its system, it is named Kepler-9d instead of Kepler-9b because two gas giants, Kepler-9b
and Kepler-9c
, were confirmed first. The original studies into the system first suggested that Kepler-9d might be a planet, but a follow-up investigation made by the Kepler team later confirmed that it was; the confirmation of Kepler-9d as a planet was made public with the team's paper, which was published in the Astrophysical Journal
on January 1, 2011 . The team used telescopes at the W.M. Keck Observatory in Hawaii to follow up on the Kepler space telescope's initial discovery.
Flagged initially as a transit event by the satellite, Kepler-9d was given the designation KOI 377.03. It was recognized as a potential planet after a study into the system confirmed Kepler-9b and Kepler-9c, but follow-up studies had to be completed to verify that it was indeed a planet, and that the apparent transit event was not due to a background eclipsing binary star in the aperture of Kepler's photometer
. Kepler's team exhaustively disproved that the small transit event could have been anything but a planet, and their results were published in the Astrophysical Journal on January 1, 2011. Follow-up observations were conducted by the High Resolution Echelle Spectrometer at the W.M. Keck Observatory in Hawaii, as well as the WIYN Observatory
in Arizona and the Palomar Observatory
in California.
s away from Earth. With a mass of 1.07 M☉
and a radius of 1.02 R☉, Kepler-9 is almost exactly the same size and width of the Sun, being only 7% more massive and 2% wider. Kepler-9 has an effective temperature
of 5777 (± 61) K, as compared to the Sun's at 5778 K, and is approximately 32% more metal-rich
(in terms of iron) than the Sun. Kepler-9 is younger than the Sun, and is estimated to be one billion years old. Kepler-9 has two planets other than Kepler-9d: the gas giants Kepler-9b and Kepler-9c.
, although its exact mass is not known. It is presumed to be at least 1.5 Earth mass
es. The planet's radius is inferred to be 1.64 RE
, or approximately 64% larger than Earth's radius. With an equilibrium temperature of 2026 K, it is hotter than all the previous planets discovered by Kepler (not counting the three previously discovered ones located in its field of view). Its density is not known. With an average distance of .0273 AU
(2,537,695.73 miles) from its star, which it orbits every 1.592851 days, Kepler-9d is the closest planet to its star in the Kepler-9 system. To compare, the planet Mercury
is .3871 AU away from the Sun, which it orbits every 87.97 days.
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...
. Initially discovered by Kepler spacecraft, a 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...
-searching satellite built and operated 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...
, Kepler-9d is most likely a Super-Earth, with an estimated radius approximately 60% larger than that of Earth's, although its exact mass cannot be determined. Kepler-9d orbits Kepler-9 every 1.56 days at a distance of .0273 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from its star, an extremely close distance. Although Kepler-9d is the closest planet to its star in its system, it is named Kepler-9d instead of Kepler-9b because two gas giants, Kepler-9b
Kepler-9b
Kepler-9b is one of the first planets discovered outside the solar system by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the...
and Kepler-9c
Kepler-9c
Kepler-9c is one of the first seven extrasolar planets, exoplanets, discovered by NASA's Kepler Mission, and one of at least two planets orbiting the star Kepler-9. Kepler-9c and Kepler-9b were the first exoplanets confirmed to be transiting their star. The planet's discovery was announced by the...
, were confirmed first. The original studies into the system first suggested that Kepler-9d might be a planet, but a follow-up investigation made by the Kepler team later confirmed that it was; the confirmation of Kepler-9d as a planet was made public with the team's paper, which was published in the Astrophysical Journal
Astrophysical Journal
The Astrophysical Journal is a peer-reviewed scientific journal covering astronomy and astrophysics. It was founded in 1895 by the American astronomers George Ellery Hale and James Edward Keeler. It publishes three 500-page issues per month....
on January 1, 2011 . The team used telescopes at the W.M. Keck Observatory in Hawaii to follow up on the Kepler space telescope's initial discovery.
Discovery and name
Kepler-9d is named because it was the third planet discovered in the orbit of Kepler-9. If it had been confirmed at the same time as planets Kepler-9b and Kepler-9c, which are (respectively) the second and third planets by distance in the system, then Kepler-9d would have been known as b; Kepler-9b as c; and Kepler-9c as d, as simultaneous discoveries are sorted by distance from the host star. Kepler-9 was named for the Kepler spacecraft, a NASA satellite that aims to discover terrestrial planets in transit around, or crossing in front of, their host stars as seen from Earth. This transit causes a regular interval in which the star briefly and slightly dims as the planet crosses it.Flagged initially as a transit event by the satellite, Kepler-9d was given the designation KOI 377.03. It was recognized as a potential planet after a study into the system confirmed Kepler-9b and Kepler-9c, but follow-up studies had to be completed to verify that it was indeed a planet, and that the apparent transit event was not due to a background eclipsing binary star in the aperture of Kepler's photometer
Photometer
In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...
. Kepler's team exhaustively disproved that the small transit event could have been anything but a planet, and their results were published in the Astrophysical Journal on January 1, 2011. Follow-up observations were conducted by the High Resolution Echelle Spectrometer at the W.M. Keck Observatory in Hawaii, as well as the WIYN Observatory
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...
in Arizona and the Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
in California.
Host star
Kepler-9 is a sunlike star in the constellation Lyra that lies some 650 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 from Earth. With a mass of 1.07 M☉
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 1.02 R☉, Kepler-9 is almost exactly the same size and width of the Sun, being only 7% more massive and 2% wider. Kepler-9 has 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 5777 (± 61) K, as compared to the Sun's at 5778 K, and is approximately 32% more metal-rich
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...
(in terms of iron) than the Sun. Kepler-9 is younger than the Sun, and is estimated to be one billion years old. Kepler-9 has two planets other than Kepler-9d: the gas giants Kepler-9b and Kepler-9c.
Characteristics
Based on the size of its light curve, Kepler-9d is assumed to be a Super-EarthSuper-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants. The term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability...
, although its exact mass is not known. It is presumed to be at least 1.5 Earth mass
Earth 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. The planet's radius is inferred to be 1.64 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...
, or approximately 64% larger than Earth's radius. With an equilibrium temperature of 2026 K, it is hotter than all the previous planets discovered by Kepler (not counting the three previously discovered ones located in its field of view). Its density is not known. With an average distance of .0273 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
(2,537,695.73 miles) from its star, which it orbits every 1.592851 days, Kepler-9d is the closest planet to its star in the Kepler-9 system. To compare, the 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...
is .3871 AU away from the Sun, which it orbits every 87.97 days.