Kepler-12b
Encyclopedia
Kepler-12b is a Hot Jupiter
that orbits G-type star Kepler-12
some 600 parsecs away. The planet has an anomalously large radius that could not be explained by standard models at the time of its discovery, as it is almost 1.7 times Jupiter's size while being 0.4 times Jupiter's mass. The planet was detected by the Kepler spacecraft, a NASA
project searching for planets that transit (cross in front of) their host stars. The discovery paper was published on September 5, 2011.
's Kepler spacecraft continuously observes a region of the night sky, searching for signs of transiting planets. While orbiting their host stars, such transiting planets cross in front of host stars as seen from Earth. The slight and periodic dimming in the star's brightness is used to determine whether or not the dimming was caused by a planet and not by a false positive. Analysis of Kepler's early data yielded evidence of a transit signal around a star designated as KIC 11804465, later known as Kepler-12. The transit signal was designated KOI-20.
The Kepler Follow-up Program
(KFOP) worked to verify the existence of the planet. KFOP used the W.M. Keck Observatory's Keck I telescope to prove that Kepler-12 was not an eclipsing binary star (a possible false positive that mimics the transit signal). The WIYN Observatory
, which was used for speckle imaging
, supported Keck's findings and verified that the signal caused by KOI-20 was not caused by a nearby background star's interference. Adaptive optics
imaging in the near-infrared was obtained on September 9, 2009 with the Palomar Observatory
's PHARO camera on the Hale telescope
confirmed both the WIYN and Keck findings.
Keck's HIRES instrument measured Kepler-12's radial velocity
, which was used to find more of Kepler-12's characteristics (and, by extension, deduce the characteristics of KOI-20 itself). The radial velocity measurements eventually led to the confirmation of Kepler-12b as a planet. Kepler's data in its first 1.5 years of operation was processed and analyzed, yielding Kepler-12b's radius, mass and density.
The Spitzer Space Telescope
's IRAC infrared adaptive optics camera was used to carried out program #60028, which observed the occultation
s by several giant planets detected by Kepler behind their host stars. The Kepler team, using the observations, tentatively concluded that Kepler-12b most likely did not experience a temperature inversion, in which the day-side temperature of the planet is lower than the night-side. Kepler-12b's discovery paper was published in the Astrophysical Journal
on September 5, 2011.
, is an early G-type to late F-type star. This corresponds strongly with a sunlike dwarf star
nearing the end of the main sequence
, and is about to become a red giant
. Kepler-12 is located 600 parsec
s (1,957 light years) away from Earth. The star also has an apparent magnitude
of 13.438, which means that it cannot be seen from Earth with the unaided eye.
The star is slightly more massive, slightly more iron-rich and slightly hotter than the Sun. However, Kepler-12 is larger, with a radius of 1.483 times the Sun's radius.
, and (at the time of its discovery) was the least-irradiated of four Hot Jupiters experiencing a radius anomaly of approximately 1.7 times or more the mass of Jupiter
. This radius anomaly entails Hot Jupiters experiencing massive radius increases for a reason not explained by scientific models. Although Kepler-12 is the least-irradiated of the four Hot Jupiters, its radius is just as large, suggesting that multiple mechanisms influencing the planet's inflation are at work. Kepler-12b was compared to HD 209458 b
in its discovery paper because both planets appear to release similar amounts of energy (flux
); it was also compared to TrES-4b because of the similar radius of the planet.
Kepler-12b has a mass of 0.431 Jupiters. Its radius of 1.695 Jupiter radii, however, indicates that the planet is almost 70% more than the size of Jupiter. With an orbit of 0.0556 AU
, Kepler-12b's average orbit is approximately 5% the average distance between the Earth and Sun. The orbit lasts 4.4379637 days. Kepler-12b has an orbital inclination of 88.86º, indicating that the planet is seen as nearly edge-on with respect to the Earth and to its host star. According to Kepler's official website, the mass and radius of the planet can be compared to 137 Earths (in mass) and 19 Earths (for its radius). The planet's density is 0.111 grams/cm3, about a tenth of the density of water, and its equilibrium temperature is 1481 K (some 5.8 times greater than Jupiter's equilibrium temperature). Additionally, Kepler-12b has an almost totally circular orbit, with an orbital eccentricity
of less than 0.01.
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
that orbits G-type star Kepler-12
Kepler-12
-References:*http://arxiv.org/pdf/1109.1611v1*http://exoplanet.eu/planet.php?p1=Kepler-12&p2=b&showPubli=yes&sortByDate...
some 600 parsecs away. The planet has an anomalously large radius that could not be explained by standard models at the time of its discovery, as it is almost 1.7 times Jupiter's size while being 0.4 times Jupiter's mass. The planet was detected 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...
project searching for planets that transit (cross in front of) their host stars. The discovery paper was published on September 5, 2011.
Discovery
NASANASA
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 continuously observes a region of the night sky, searching for signs of transiting planets. While orbiting their host stars, such transiting planets cross in front of host stars as seen from Earth. The slight and periodic dimming in the star's brightness is used to determine whether or not the dimming was caused by a planet and not by a false positive. Analysis of Kepler's early data yielded evidence of a transit signal around a star designated as KIC 11804465, later known as Kepler-12. The transit signal was designated KOI-20.
Kepler Follow-up Program
The Kepler-Follow-up Program, known also as the Kepler Follow-up Observation Program and KFOP, is a program instituted to conduct follow-up observations on Kepler Objects of Interest , or signals noticed by the Kepler spacecraft that may indicate the presence of a planet transiting its host star...
(KFOP) worked to verify the existence of the planet. KFOP used the W.M. Keck Observatory's Keck I telescope to prove that Kepler-12 was not an eclipsing binary star (a possible false positive that mimics the transit signal). 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...
, which was used for speckle imaging
Speckle imaging
Speckle imaging describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add method or on speckle interferometry methods...
, supported Keck's findings and verified that the signal caused by KOI-20 was not caused by a nearby background star's interference. Adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
imaging in the near-infrared was obtained on September 9, 2009 with 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...
's PHARO camera on the Hale telescope
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...
confirmed both the WIYN and Keck findings.
Keck's HIRES instrument measured Kepler-12's radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
, which was used to find more of Kepler-12's characteristics (and, by extension, deduce the characteristics of KOI-20 itself). The radial velocity measurements eventually led to the confirmation of Kepler-12b as a planet. Kepler's data in its first 1.5 years of operation was processed and analyzed, yielding Kepler-12b's radius, mass and density.
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...
's IRAC infrared adaptive optics camera was used to carried out program #60028, which observed the occultation
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
s by several giant planets detected by Kepler behind their host stars. The Kepler team, using the observations, tentatively concluded that Kepler-12b most likely did not experience a temperature inversion, in which the day-side temperature of the planet is lower than the night-side. Kepler-12b's discovery paper 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 September 5, 2011.
Host star
Kepler-12, known also as KIC 11804465 in the Kepler Input CatalogKepler Input Catalog
The Kepler Input Catalog is a publicly searchable database of roughly 13.2 million targets used for the Kepler Spectral Classification Program and Kepler....
, is an early G-type to late F-type star. This corresponds strongly with a sunlike dwarf star
Dwarf star
The term dwarf star refers to a variety of distinct classes of stars.* Dwarf star alone generally refers to any main sequence star, a star of luminosity class V.** Red dwarfs are low-mass main sequence stars....
nearing the end of the main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
, and is about to become a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
. Kepler-12 is located 600 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 (1,957 light years) away from Earth. The star also 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 13.438, which means that it cannot be seen from Earth with the unaided eye.
The star is slightly more massive, slightly more iron-rich and slightly hotter than the Sun. However, Kepler-12 is larger, with a radius of 1.483 times the Sun's radius.
Characteristics
Kepler-12b is a Hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
, and (at the time of its discovery) was the least-irradiated of four Hot Jupiters experiencing a radius anomaly of approximately 1.7 times or more the mass of Jupiter
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....
. This radius anomaly entails Hot Jupiters experiencing massive radius increases for a reason not explained by scientific models. Although Kepler-12 is the least-irradiated of the four Hot Jupiters, its radius is just as large, suggesting that multiple mechanisms influencing the planet's inflation are at work. Kepler-12b was compared to HD 209458 b
HD 209458 b
HD 209458 b is an extrasolar planet that orbits the Solar analog star HD 209458 in the constellation Pegasus, some 150 light-years from Earth's solar system, with evidence of water vapor....
in its discovery paper because both planets appear to release similar amounts of energy (flux
Flux
In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
); it was also compared to TrES-4b because of the similar radius of the planet.
Kepler-12b has a mass of 0.431 Jupiters. Its radius of 1.695 Jupiter radii, however, indicates that the planet is almost 70% more than the size of Jupiter. With an orbit of 0.0556 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, Kepler-12b's average orbit is approximately 5% the average distance between the Earth and Sun. The orbit lasts 4.4379637 days. Kepler-12b has an orbital inclination of 88.86º, indicating that the planet is seen as nearly edge-on with respect to the Earth and to its host star. According to Kepler's official website, the mass and radius of the planet can be compared to 137 Earths (in mass) and 19 Earths (for its radius). The planet's density is 0.111 grams/cm3, about a tenth of the density of water, and its equilibrium temperature is 1481 K (some 5.8 times greater than Jupiter's equilibrium temperature). Additionally, Kepler-12b has an almost totally circular orbit, with an orbital 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...
of less than 0.01.