Kepler-10c
Encyclopedia
Kepler-10c is an exoplanet
orbiting yellow giant Kepler-10
, located around 560 light-years away in Draco
. Its discovery was announced by Kepler in May 2011, although it had been seen as a planetary candidate since January 2011 when Kepler-10b
was discovered. The team confirmed the observation using data from NASA's Spitzer Space Telescope
and a technique called Blender that ruled out most false positives. Kepler-10c was the third transiting planet to be confirmed statistically (based on probability rather than actual observation), after Kepler-9d
and Kepler-11g. The Kepler team considers the statistical method that led to the discovery of Kepler-10c as what will be necessary to confirm many planets in Kepler's field of view.
Kepler-10c orbits its host star every forty-five days at a quarter of the average distance between the Sun and Earth. It is about twice as large as Earth, although its mass was not well-constrained at the time of its confirmation in May 2011. It is likely that Kepler-10c is composed of low-density volatiles
, like water and gases, much like the planets GJ 1214 b, Kepler-11b
, and Kepler-11f
.
was confirmed in the orbit of the star Kepler-10
after measurements of its transiting behavior (where it crosses in front of Kepler-10, periodically dimming it) and a radial velocity
effect detected in Kepler-10's spectrum
provided the information needed to prove that it was indeed a planet. An additional, longer-period dimming was detected in Kepler-10's spectrum, suggesting that a second planet existed in the system; however, there remained the possibility that this signal could have been caused by some alternative reason, and that the transit event was a false positive. Attempts to measure the radial velocity effects of this object, now named KOI 072.02, were fruitless; therefore, to rule out false positive scenarios, the Kepler team used a technique called Blender.
The application of Blender was supplemented by use of the IRAC instrument on the Spitzer Space Telescope
, which was used on August 30 and November 15 in 2010 to further define Kepler-10's light curve at the point where KOI 072.02 appeared to transit it. It was found that the transiting object did not produce a color, an aspect that is characteristic of stars. This suggested even further that KOI 072.02 was a planet. In addition, the IRAC instrument found no difference in the transit signal when comparing the star's light curve in the infrared and in visible light; stars that are aligned with Kepler-10 might appear visibly similar, but would appear different in the infrared.
The WIYN Observatory
's 3.5m telescope was used for speckle imaging
on June 18, 2010; in addition, the PHARO camera on the Palomar Observatory
's 5m telescope was used for its adaptive optics
capabilities. These observations, combined with observations of Kepler-10's spectrum taken from the W.M. Keck Observatory, to rule out the possibility that a nearby star's light was corrupting the observed spectrum of Kepler-10 and creating the results that had led astronomers to believe that a second planet existed in Kepler-10's orbit. All of these possibilities, with the exception of if such a star existed exactly behind or in front of Kepler-10, were effectively ruled out; even with this, the Kepler team found that if a star was indeed aligned with Kepler-10 as seen from Earth, such a star would probably not be a giant star
.
With a greater degree of certainty established, the Kepler team compared the models formed using Blender to the photometric
observations collected by the Kepler satellite. The Blender technique allowed the Kepler team to rule out the majority of the alternatives including, notably, that of triple star systems
. Blender then allowed the Kepler team to determine that although all models representing hierarchical triple stars (a binary system between a single star and a double star) can resemble the light curve of Kepler-10, the aforementioned follow-up observations would have detected them all. The only possible blends remaining after ruling out hierarchical triple stars was that of determining if the curve is caused by interference from a background star, or if it is indeed caused by the orbit of a transiting planet.
Comparisons of KOI 072.02 to the 1235 other Kepler Objects of Interest
in Kepler's field of vision allowed astronomers to use models that led to the confirmation of KOI 072.02 as a planet with a high degree of certainty. KOI 072.02 was then renamed Kepler-10c. The planet's confirmation was announced at the Boston meeting of the American Astronomical Society
on May 23, 2011.
Kepler-10c was the first Kepler target to be observed using Spitzer with the hope of detecting a shallow transit dip in a light curve. At the time of Kepler-10c's discovery, Spitzer was the only facility capable of detecting shallow transits in the Kepler data to an extent at which the data could be meaningfully analyzed. The planet was also the third transiting planet that was validated through an analysis of statistical data (rather than actual observation), after the planets Kepler-9d
and Kepler-11g. In Kepler-10c's confirmation paper, the Kepler team discussed how a large fraction of planets in Kepler's field of view would be confirmed in this statistical manner.
s (564 light years) from Earth. The star is 0.895 solar mass
es and 1.056 solar radii, making the star slightly less massive than the Sun, but approximately the same size. With an effective temperature
of 5627 K, Kepler-10 is cooler than the Sun. The star is also metal-rich and far older: respectively, its metallicity
is measured at [Fe/H] = -0.16 (71% the amount of iron in the Sun), and its age at 11.9 billion years. Kepler-10 has an apparent magnitude
of 10.96, which means that the planet is invisible to the naked eye
from the perspective of an observer on Earth.
There are two planets known in the orbit of Kepler-10, the first being Kepler-10b. Kepler-10b is a rocky planet that orbits Kepler-10 every 0.8 days at a distance of 0.01684 AU
.
of Earth. At the time of its confirmation, Kepler-10c's mass had not yet been well-defined, and is estimated to have an upper limit of 0.06 times the mass
of Jupiter and an upper limit of 20 times the mass
of Earth. Kepler-10c's equilibrium temperature is estimated at 485 K, almost four times hotter than Jupiter. The planet's orbital inclination is 89.65º, or almost edge-on with respect to Earth and to Kepler-10. Transits have been observed at points where Kepler-10c has crossed in front of its host star.
Kepler-10c would have to have a mass at its upper limit (20 Earth masses) to have an Earth-like composition, so it is more likely that it is composed of low-density materials like water and hydrogen or helium gas. Kepler-10c might be more like the planets GJ 1214 b, Kepler-11b
, and Kepler-11f
, planets that are low mass and enriched in volatiles
.
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...
orbiting yellow giant Kepler-10
Kepler-10
Kepler-10, formerly known as KOI-72, is a sunlike star in constellation Draco that lies 173 parsecs away from the Earth. Kepler-10 was targeted by NASA's Kepler spacecraft, as it was seen the first star identified by the Kepler mission as a possible host to a small, transiting exoplanet...
, located around 560 light-years away in Draco
Draco (constellation)
Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere...
. Its discovery was announced by Kepler in May 2011, although it had been seen as a planetary candidate since January 2011 when 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...
was discovered. The team confirmed the observation using data from NASA's Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
and a technique called Blender that ruled out most false positives. Kepler-10c was the third transiting planet to be confirmed statistically (based on probability rather than actual observation), after Kepler-9d
Kepler-9d
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...
and Kepler-11g. The Kepler team considers the statistical method that led to the discovery of Kepler-10c as what will be necessary to confirm many planets in Kepler's field of view.
Kepler-10c orbits its host star every forty-five days at a quarter of the average distance between the Sun and Earth. It is about twice as large as Earth, although its mass was not well-constrained at the time of its confirmation in May 2011. It is likely that Kepler-10c is composed of low-density volatiles
Volatiles
In planetary science, volatiles are that group of chemical elements and chemical compounds with low boiling points that are associated with a planet's or moon's crust and/or atmosphere. Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, and methane, all compounds of C, H, O...
, like water and gases, much like the planets GJ 1214 b, 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-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...
.
Discovery and confirmation
In January 2011, the closely orbiting planet Kepler-10bKepler-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...
was confirmed in the orbit of the star Kepler-10
Kepler-10
Kepler-10, formerly known as KOI-72, is a sunlike star in constellation Draco that lies 173 parsecs away from the Earth. Kepler-10 was targeted by NASA's Kepler spacecraft, as it was seen the first star identified by the Kepler mission as a possible host to a small, transiting exoplanet...
after measurements of its transiting behavior (where it crosses in front of Kepler-10, periodically dimming it) and a 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...
effect detected in Kepler-10's spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
provided the information needed to prove that it was indeed a planet. An additional, longer-period dimming was detected in Kepler-10's spectrum, suggesting that a second planet existed in the system; however, there remained the possibility that this signal could have been caused by some alternative reason, and that the transit event was a false positive. Attempts to measure the radial velocity effects of this object, now named KOI 072.02, were fruitless; therefore, to rule out false positive scenarios, the Kepler team used a technique called Blender.
The application of Blender was supplemented by use of the IRAC instrument on 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...
, which was used on August 30 and November 15 in 2010 to further define Kepler-10's light curve at the point where KOI 072.02 appeared to transit it. It was found that the transiting object did not produce a color, an aspect that is characteristic of stars. This suggested even further that KOI 072.02 was a planet. In addition, the IRAC instrument found no difference in the transit signal when comparing the star's light curve in the infrared and in visible light; stars that are aligned with Kepler-10 might appear visibly similar, but would appear different in the infrared.
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...
's 3.5m telescope 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...
on June 18, 2010; in addition, the PHARO camera on 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 5m telescope was used for its 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...
capabilities. These observations, combined with observations of Kepler-10's spectrum taken from the W.M. Keck Observatory, to rule out the possibility that a nearby star's light was corrupting the observed spectrum of Kepler-10 and creating the results that had led astronomers to believe that a second planet existed in Kepler-10's orbit. All of these possibilities, with the exception of if such a star existed exactly behind or in front of Kepler-10, were effectively ruled out; even with this, the Kepler team found that if a star was indeed aligned with Kepler-10 as seen from Earth, such a star would probably not be a giant star
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
.
With a greater degree of certainty established, the Kepler team compared the models formed using Blender to the photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
observations collected by the Kepler satellite. The Blender technique allowed the Kepler team to rule out the majority of the alternatives including, notably, that of triple star systems
Multiple star
A multiple star consists of three or more stars which appear from the Earth to be close to one another in the sky. This may result from the stars being physically close and gravitationally bound to each other, in which case it is physical, or this closeness may be merely apparent, in which case...
. Blender then allowed the Kepler team to determine that although all models representing hierarchical triple stars (a binary system between a single star and a double star) can resemble the light curve of Kepler-10, the aforementioned follow-up observations would have detected them all. The only possible blends remaining after ruling out hierarchical triple stars was that of determining if the curve is caused by interference from a background star, or if it is indeed caused by the orbit of a transiting planet.
Comparisons of KOI 072.02 to the 1235 other Kepler Objects of Interest
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...
in Kepler's field of vision allowed astronomers to use models that led to the confirmation of KOI 072.02 as a planet with a high degree of certainty. KOI 072.02 was then renamed Kepler-10c. The planet's confirmation was announced at the Boston meeting of the American Astronomical Society
American Astronomical Society
The American Astronomical Society is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC...
on May 23, 2011.
Kepler-10c was the first Kepler target to be observed using Spitzer with the hope of detecting a shallow transit dip in a light curve. At the time of Kepler-10c's discovery, Spitzer was the only facility capable of detecting shallow transits in the Kepler data to an extent at which the data could be meaningfully analyzed. The planet was also the third transiting planet that was validated through an analysis of statistical data (rather than actual observation), after the planets Kepler-9d
Kepler-9d
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...
and Kepler-11g. In Kepler-10c's confirmation paper, the Kepler team discussed how a large fraction of planets in Kepler's field of view would be confirmed in this statistical manner.
Host star
Kepler-10 is a G-type star located 173 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 (564 light years) from Earth. The star is 0.895 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es and 1.056 solar radii, making the star slightly less massive than the Sun, but approximately the same size. With 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 5627 K, Kepler-10 is cooler than the Sun. The star is also metal-rich and far older: respectively, its 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 measured at [Fe/H] = -0.16 (71% the amount of iron in the Sun), and its age at 11.9 billion years. Kepler-10 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 10.96, which means that the planet is invisible to 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"...
from the perspective of an observer on Earth.
There are two planets known in the orbit of Kepler-10, the first being Kepler-10b. Kepler-10b is a rocky planet that orbits Kepler-10 every 0.8 days at a distance of 0.01684 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
.
Characteristics
Kepler-10c is the second planet in Kepler-10's orbit, circling its star every 45.29485 days at a distance of 0.2407 AU, or 24% of the mean distance between the Earth and Sun. Kepler-10c's radius is estimated at 0.2 times the radius of Jupiter and 2.227 times the radiusEarth 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...
of Earth. At the time of its confirmation, Kepler-10c's mass had not yet been well-defined, and is estimated to have an upper limit of 0.06 times the mass
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....
of Jupiter and an upper limit of 20 times the 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....
of Earth. Kepler-10c's equilibrium temperature is estimated at 485 K, almost four times hotter than Jupiter. The planet's orbital inclination is 89.65º, or almost edge-on with respect to Earth and to Kepler-10. Transits have been observed at points where Kepler-10c has crossed in front of its host star.
Kepler-10c would have to have a mass at its upper limit (20 Earth masses) to have an Earth-like composition, so it is more likely that it is composed of low-density materials like water and hydrogen or helium gas. Kepler-10c might be more like the planets GJ 1214 b, 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-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...
, planets that are low mass and enriched in volatiles
Volatiles
In planetary science, volatiles are that group of chemical elements and chemical compounds with low boiling points that are associated with a planet's or moon's crust and/or atmosphere. Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, and methane, all compounds of C, H, O...
.