Kepler-7b
Encyclopedia
Kepler-7b is one of the first five planets to be confirmed by NASA
's Kepler spacecraft, and was confirmed in the first 33.5 days of Kepler's science operations. It is in the orbit of a star that is not as hot as the Sun, but is significantly larger and is expected to soon reach the end of the main sequence
. Kepler-7b is a Hot Jupiter
that is about half the mass of Jupiter, but is nearly 1.5 times its size; at the time of its discovery, Kepler-7b was the second most diffuse planet known, surpassed only by WASP-17b
. It orbits its host star every five days at a distance of approximately 0.06 AU
. Kepler-7b was announced at a meeting of the American Astronomical Society
on January 4, 2010.
's Kepler spacecraft was completing the last of tests on its photometer
, the instrument it uses to detect transit events, in which a planet crosses in front of and dims its host star for a brief and roughly regular period of time. In this last test, Kepler observed 50,000 stars in the Kepler Input Catalog
, including Kepler-7; the preliminary light curves were sent to the Kepler science team for analysis, who chose obvious planetary companions from the bunch for follow-up at observatories. Kepler-7 was not one of these original candidates. After a resting period of 1.3 days, Kepler began a nonstop 33.5-day period in which it observed 150,000 targets uninterrupted until June 15, 2009, when the collected data was downloaded and tested for false positives. Kepler-7's candidate was not found to be one of these false positives, such as an eclipsing binary star that may generate a light curve that mimics that of transiting planetary companions. Kepler-7 was then observed using Doppler spectroscopy
using the Fibre-fed Echelle Spectrograph at the Canary Islands' Nordic Optical Telescope
for ten nights in October 2009, taken with respect to the star HD 182488 to compensate for possible telescope error. Speckle imaging
of the star was taken at WIYN Observatory
in Arizona to check for close companions; when none were found, the High Resolution Echelle Spectrometer instrument at the W.M. Keck Observatory on Hawaii, the Harlan J. Smith Telescope
at the McDonald Observatory
in Texas, the PRISM camera at the Lowell Observatory
, and the Faulkes Telescope North
at the Haleakala Observatory
on Maui were also used to analyze Doppler spectroscopy of the planetary candidate. The radial velocity observations confirmed that a planetary body was responsible for the dips observed in Kepler-7's light curve, thus confirming it as a planet.
Kepler's first discoveries, including the planets Kepler-4b
, Kepler-5b
, Kepler-6b
, Kepler-7b, and Kepler-8b
, were first announced on January 4, 2010, at the 215th meeting of the American Astronomical Society
in Washington, D.C.
is the largest host star of the first five planets detected by Kepler, and is situated in the Lyra constellation. The star has a radius 184% that of the Sun. Kepler-7 also has 135% the Sun's mass, and thus is larger and more massive (though less dense than) the Sun. It is slightly hotter than the Sun, as Kepler-7 has an effective temperature
of 5933 K. The star is near its end of its life on the main sequence
. The star's metallicity
is [Fe/H] = 0.11, which means that Kepler-7 has 128% the amount of iron than is detected in the Sun.
, a Jupiter-sized gas giant
exoplanet orbiting close to its star. Its equilibrium temperature, due to its proximity to its star, is hot, and is measured at nearly 1540 K. However, of the first five planets discovered by Kepler, it is the second coolest, surpassed only by Kepler-6b
. This is over twelve times hotter than Jupiter. Kepler-7b has a mass
that is 0.433 times that of Jupiter, although it has been expanded to a size that is 1.478 times the radius of Jupiter. Because of this, its density is only 0.166 g/cm3, about the same as polystyrene
, a substance used to manufacture lightweight, disposable commercial plastic products. Only WASP-17b
(0.49MJ
; 1.66RJ) was known to have a lower-known density at the time of Kepler-7b's discovery. Such low densities are not predicted by current standard theories of planet formation. Kepler-7b orbits its host star every 4.8855 days at a distance of 0.06224 AU
, making it the furthest-orbiting planet of the first five discovered by Kepler. In addition, Kepler-7b has an observed orbital inclination of 86.5º, which means that it orbit is almost edge-on as seen from Earth. Mercury
, in contrast, orbits at a distance of .387 AU every 87.97 days.
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, and was confirmed in the first 33.5 days of Kepler's science operations. It is in the orbit of a star that is not as hot as the Sun, but is significantly larger and is expected to soon reach 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...
. Kepler-7b is a Hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
that is about half the mass of Jupiter, but is nearly 1.5 times its size; at the time of its discovery, Kepler-7b was the second most diffuse planet known, surpassed only by WASP-17b
WASP-17b
WASP-17b is an exoplanet in the constellation Scorpius that is orbiting the star WASP-17. Its discovery was announced on 11 August 2009. It is the first planet discovered to have a retrograde orbit, meaning it orbits in a direction counter to the rotation of its host star. This discovery changed...
. It orbits its host star every five days at a distance of approximately 0.06 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. Kepler-7b was announced at a 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 January 4, 2010.
Discovery
In 2009, 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 was completing the last of tests on its 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...
, the instrument it uses to detect transit events, in which a planet crosses in front of and dims its host star for a brief and roughly regular period of time. In this last test, Kepler observed 50,000 stars in the Kepler Input Catalog
Kepler 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....
, including Kepler-7; the preliminary light curves were sent to the Kepler science team for analysis, who chose obvious planetary companions from the bunch for follow-up at observatories. Kepler-7 was not one of these original candidates. After a resting period of 1.3 days, Kepler began a nonstop 33.5-day period in which it observed 150,000 targets uninterrupted until June 15, 2009, when the collected data was downloaded and tested for false positives. Kepler-7's candidate was not found to be one of these false positives, such as an eclipsing binary star that may generate a light curve that mimics that of transiting planetary companions. Kepler-7 was then observed using Doppler spectroscopy
Doppler spectroscopy
Doppler spectroscopy, also known as radial velocity measurement, is a spectroscopic method for finding extrasolar planets. It involves the observation of Doppler shifts in the spectrum of the star around which the planet orbits....
using the Fibre-fed Echelle Spectrograph at the Canary Islands' 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...
for ten nights in October 2009, taken with respect to the star HD 182488 to compensate for possible telescope error. 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...
of the star was taken at 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 to check for close companions; when none were found, the High Resolution Echelle Spectrometer instrument at the W.M. Keck Observatory on Hawaii, the Harlan J. Smith Telescope
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...
at the McDonald Observatory
McDonald Observatory
The McDonald Observatory is an astronomical observatory located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Fowlkes and Mount Locke in the Davis Mountains of West Texas...
in Texas, the PRISM camera at the Lowell Observatory
Lowell Observatory
Lowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
, and the Faulkes Telescope North
Faulkes Telescope North
The Faulkes Telescope North is a clone of the Liverpool Telescope, and is located at Haleakala Observatory in the U.S. state of Hawaii.The telescope is owned and operated by LCOGT. This telescope and its sister telescope Faulkes Telescope South are used by research and education groups across the...
at the Haleakala Observatory
Haleakala Observatory
The Haleakala High Altitude Observatory site, on the Island of Maui is the site of Hawaii's first astronomical research observatory. At elevation, Haleakala is above one third of the Earth's atmosphere...
on Maui were also used to analyze Doppler spectroscopy of the planetary candidate. The radial velocity observations confirmed that a planetary body was responsible for the dips observed in Kepler-7's light curve, thus confirming it as a planet.
Kepler's first discoveries, including the planets Kepler-4b
Kepler-4b
Kepler-4b, initially known as KOI 7.01, is an extrasolar planet first detected as a transit by the Kepler spacecraft. Its radius and mass are similar to that of Neptune; however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System. The planet's...
, Kepler-5b
Kepler-5b
Kepler-5b is one of the first five planets discovered by NASA's Kepler spacecraft. It is a Hot Jupiter that orbits a subgiant star that is more massive, larger, and more diffuse than the Sun is...
, Kepler-6b
Kepler-6b
Kepler-6b is an extrasolar planet in the orbit of the unusually metal-rich Kepler-6, a star in the field of view of the NASA-operated Kepler spacecraft, which searches for planets that cross directly in front of, or transit, their host stars. It was the third planet to be discovered by Kepler....
, Kepler-7b, and Kepler-8b
Kepler-8b
Kepler-8b is the fifth of the first five exoplanets discovered by NASA's Kepler spacecraft, which aims to discover planets in a region of the sky between the constellations Lyra and Cygnus that transit their host stars. The planet is the hottest of the five...
, were first announced on January 4, 2010, at the 215th 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...
in Washington, D.C.
Host star
Kepler-7Kepler-7
Kepler-7 is a star located in the constellation Lyra in the field of view of the Kepler Mission, a NASA operation in search of Earth-like planets. It is home to the fourth of the first five planets that Kepler discovered; this planet, a Jupiter-size gas giant named Kepler-7b, is as light as styrofoam...
is the largest host star of the first five planets detected by Kepler, and is situated in the Lyra constellation. The star has a radius 184% that of the Sun. Kepler-7 also has 135% the Sun's mass, and thus is larger and more massive (though less dense than) the Sun. It is slightly hotter than the Sun, as Kepler-7 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 5933 K. The star is near its end of its life on 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...
. The star's 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 [Fe/H] = 0.11, which means that Kepler-7 has 128% the amount of iron than is detected in the Sun.
Characteristics
Kepler-7b is a hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
, a Jupiter-sized gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...
exoplanet orbiting close to its star. Its equilibrium temperature, due to its proximity to its star, is hot, and is measured at nearly 1540 K. However, of the first five planets discovered by Kepler, it is the second coolest, surpassed only by Kepler-6b
Kepler-6b
Kepler-6b is an extrasolar planet in the orbit of the unusually metal-rich Kepler-6, a star in the field of view of the NASA-operated Kepler spacecraft, which searches for planets that cross directly in front of, or transit, their host stars. It was the third planet to be discovered by Kepler....
. This is over twelve times hotter than Jupiter. Kepler-7b has a 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....
that is 0.433 times that of Jupiter, although it has been expanded to a size that is 1.478 times the radius of Jupiter. Because of this, its density is only 0.166 g/cm3, about the same as polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...
, a substance used to manufacture lightweight, disposable commercial plastic products. Only WASP-17b
WASP-17b
WASP-17b is an exoplanet in the constellation Scorpius that is orbiting the star WASP-17. Its discovery was announced on 11 August 2009. It is the first planet discovered to have a retrograde orbit, meaning it orbits in a direction counter to the rotation of its host star. This discovery changed...
(0.49MJ
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....
; 1.66RJ) was known to have a lower-known density at the time of Kepler-7b's discovery. Such low densities are not predicted by current standard theories of planet formation. Kepler-7b orbits its host star every 4.8855 days at a distance of 0.06224 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, making it the furthest-orbiting planet of the first five discovered by Kepler. In addition, Kepler-7b has an observed orbital inclination of 86.5º, which means that it orbit is almost edge-on as seen from Earth. 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...
, in contrast, orbits at a distance of .387 AU every 87.97 days.