WASP-13b
Encyclopedia
WASP-13b is an extrasolar planet
that was discovered in 2008 in the orbit of the sunlike star WASP-13. The planet has a mass of nearly half that of Jupiter, but a radius five-fourths the size of Jupiter. This low relative mass might be caused by a core that is of low mass or that is not present at all.
The planet orbits at approximately 5% of the distance between the Sun and Earth every four days. The star was observed several times between 2006 and 2009, at first through the SuperWASP
program and later through focused follow-up observations. Analysis of collected radial velocity
measurements led to the discovery of WASP-13b, which was reported in a journal on April 7, 2009. A follow-up study published in 2011 investigated the cause for inflated planets such as WASP-13b, and re-examined (and re-constrained) its mass, radius, density, and age.
-North program based at Roque de los Muchachos Observatory
in the Canary Islands led to the identification of WASP-13 as host to a potentially transiting object. Photometric
follow-up observations were taken on February 16, 2008 using the James Gregory Telescope
(JGT) in Scotland, which took 1047 exposures of the star, although the last twenty images taken were obscured by cloud cover and were discarded. Using HD 80408 as a reference star along with JGT measurements, the astronomers investigating the system were able to create a light curve
for the transiting planet.
WASP-13 was observed between February 11 and 15 in 2008 by the SOPHIE échelle spectrograph
at the Haute-Provence Observatory
in France, determining the radial velocity
of the transiting body. Use of the FIES echelle spectrograph at the Nordic Optical Telescope
in the Canary Islands gained other spectral measurements that yielded the characteristics of the star. Analysis of the SOPHIE and FIES data were used to constrain some of the orbiting body's characteristics. The discovery of the orbiting body's mass using radial velocity measurements led to its confirmation as the planet WASP-13b.
The discovery of WASP-13b was reported in the journal Astronomy and Astrophysics
by the European Southern Observatory
on May 19, 2009. The discovery paper was received by the journal on April 7, 2009.
Later, between 2009 and 2011, another team of astronomers observed WASP-13b and WASP-21b to find what caused some Hot Jupiters to have anomalously high radii. The RISE photometric camera on the Liverpool Telescope
was used to detect further transits. Two partial transits and two full transits were observed during this period, although the quality of both full transits was slightly compromised because of passing cloud cover. The collected observations, along with the JGT observations that were used to confirm the planet, were scaled to filter out errors such as background noise. The data was then used to re-define WASP-13b's parameters, including its age, mass, radius, and density. The study also noted that a limb darkening
effect was present, a characteristic that may affect future atmospheric studies of the planet.
constellation. Measurements taken by FIES and SOPHIE did not constrain the mass, radius, or age well; however, a later 2011 study using the Liverpool Telescope better-constrained those parameters. The star's mass is estimated at 1.09 times the mass of the Sun
, its radius at 1.559 times that of the Sun, and its density at 0.288 time's the Sun's density. These characteristics are re-defined taking limb darkening
into account. The star's metallicity
, which is measured by iron content, is placed roughly at [Fe/H] = 0, similar to that of the Sun. Also, the star's estimated effective temperature
is 5826 K, slightly warmer than the Sun.
WASP-13 has an apparent magnitude
of 10.42, making it invisible to the unaided eye as seen from Earth.
and a radius that is 1.389 times times Jupiter's radius. The planet is, in other words, less massive than Jupiter, but slightly more than a four tenths its size. WASP-13b's low mass can mostly likely be attributed to the presence of a low-mass core, or to the total lack of a core, according to the discovery paper. WASP-13b, which orbits its host star at a distance of 0.05362 AU
, circles its star completely every 4.35298 days. The 2011 study on the planet recognized WASP-13b as the fifth lowest-density extrasolar planet known, behind Kepler-7b
; WASP-17b
; TrES-4b; and COROT-5b.
WASP-13b has an orbital inclination of 86.9º, which means that it orbits almost edge-on as seen from Earth.
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...
that was discovered in 2008 in the orbit of the sunlike star WASP-13. The planet has a mass of nearly half that of Jupiter, but a radius five-fourths the size of Jupiter. This low relative mass might be caused by a core that is of low mass or that is not present at all.
The planet orbits at approximately 5% of the distance between the Sun and Earth every four days. The star was observed several times between 2006 and 2009, at first through the SuperWASP
SuperWASP
SuperWASP is an international academic organisation performing an ultra-wide angle search for transiting extrasolar planets with the aim of covering the entire sky down to ~15th magnitude.-Equipment:...
program and later through focused follow-up observations. Analysis of collected 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...
measurements led to the discovery of WASP-13b, which was reported in a journal on April 7, 2009. A follow-up study published in 2011 investigated the cause for inflated planets such as WASP-13b, and re-examined (and re-constrained) its mass, radius, density, and age.
Discovery
Between November 27, 2006, and April 1, 2007, 3329 images of the star WASP-13 by the SuperWASPSuperWASP
SuperWASP is an international academic organisation performing an ultra-wide angle search for transiting extrasolar planets with the aim of covering the entire sky down to ~15th magnitude.-Equipment:...
-North program based at Roque de los Muchachos Observatory
Roque de los Muchachos Observatory
Roque de los Muchachos Observatory is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands...
in the Canary Islands led to the identification of WASP-13 as host to a potentially transiting object. Photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
follow-up observations were taken on February 16, 2008 using the James Gregory Telescope
James Gregory Telescope
The James Gregory Telescope was constructed in 1962 by the University of St Andrews. It is of a Schmidt-Cassegrain design and is fitted with a CCD camera...
(JGT) in Scotland, which took 1047 exposures of the star, although the last twenty images taken were obscured by cloud cover and were discarded. Using HD 80408 as a reference star along with JGT measurements, the astronomers investigating the system were able to create a light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
for the transiting planet.
WASP-13 was observed between February 11 and 15 in 2008 by the SOPHIE échelle spectrograph
SOPHIE échelle spectrograph
The SOPHIE échelle spectrograph is a high-resolution echelle spectrograph installed on the 1.93m reflector telescope at the Haute-Provence Observatory located in south-eastern France...
at the Haute-Provence Observatory
Haute-Provence Observatory
The Observatoire de Haute-Provence was established in 1937 as a national facility for French astronomers. Astronomical observations began in 1943 using the 1.20 m telescope, and the first research papers based on observations made at the observatory were published in 1944...
in France, determining the 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...
of the transiting body. Use of the FIES echelle spectrograph at the 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...
in the Canary Islands gained other spectral measurements that yielded the characteristics of the star. Analysis of the SOPHIE and FIES data were used to constrain some of the orbiting body's characteristics. The discovery of the orbiting body's mass using radial velocity measurements led to its confirmation as the planet WASP-13b.
The discovery of WASP-13b was reported in the journal Astronomy and Astrophysics
Astronomy and Astrophysics
* Astronomy and Astrophysics has a 2010 impact factor of 4.410.-See also:*The Astronomy and Astrophysics Review*Advanced Satellite for Cosmology and Astrophysics*Astronomy & Geophysics*Astronomical Journal*Astrophysical Journal...
by the European Southern Observatory
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
on May 19, 2009. The discovery paper was received by the journal on April 7, 2009.
Later, between 2009 and 2011, another team of astronomers observed WASP-13b and WASP-21b to find what caused some Hot Jupiters to have anomalously high radii. The RISE photometric camera on the Liverpool Telescope
Liverpool Telescope
The Liverpool Telescope is a fully robotic telescope that observes autonomously, i.e. it operates without human intervention. Professional astronomers and other registered users submit observation specifications to be considered by the telescope's robotic control system at any time of the day or...
was used to detect further transits. Two partial transits and two full transits were observed during this period, although the quality of both full transits was slightly compromised because of passing cloud cover. The collected observations, along with the JGT observations that were used to confirm the planet, were scaled to filter out errors such as background noise. The data was then used to re-define WASP-13b's parameters, including its age, mass, radius, and density. The study also noted that a limb darkening
Limb darkening
Limb darkening refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image...
effect was present, a characteristic that may affect future atmospheric studies of the planet.
Host star
WASP-13 is a sunlike G-type star located in the LynxLynx (constellation)
Lynx is a constellation in the northern sky, introduced in the 17th century by Johannes Hevelius. It is named after the lynx, a genus of cat. It is a very faint constellation; its brightest stars form a zigzag line.-History:...
constellation. Measurements taken by FIES and SOPHIE did not constrain the mass, radius, or age well; however, a later 2011 study using the Liverpool Telescope better-constrained those parameters. The star's mass is estimated at 1.09 times the mass of the Sun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
, its radius at 1.559 times that of the Sun, and its density at 0.288 time's the Sun's density. These characteristics are re-defined taking limb darkening
Limb darkening
Limb darkening refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image...
into account. 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...
, which is measured by iron content, is placed roughly at [Fe/H] = 0, similar to that of the Sun. Also, the star's estimated 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...
is 5826 K, slightly warmer than the Sun.
WASP-13 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 10.42, making it invisible to the unaided eye as seen from Earth.
Characteristics
WASP-13b is a transiting planet with an estimated mass that is (including limb darkening) 0.477 times that of JupiterJupiter 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....
and a radius that is 1.389 times times Jupiter's radius. The planet is, in other words, less massive than Jupiter, but slightly more than a four tenths its size. WASP-13b's low mass can mostly likely be attributed to the presence of a low-mass core, or to the total lack of a core, according to the discovery paper. WASP-13b, which orbits its host star at a distance of 0.05362 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, circles its star completely every 4.35298 days. The 2011 study on the planet recognized WASP-13b as the fifth lowest-density extrasolar planet known, behind Kepler-7b
Kepler-7b
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...
; 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...
; TrES-4b; and COROT-5b.
WASP-13b has an orbital inclination of 86.9º, which means that it orbits almost edge-on as seen from Earth.