WASP-43b
Encyclopedia
WASP-43b is a transiting planet in orbit around the young, active, and low-mass star WASP-43
in the constellation Sextans. The planet is a Hot Jupiter
with a mass almost twice that of Jupiter, but a radius that is slightly less than Jupiter's. WASP-43b was flagged as a candidate by the SuperWASP
program before they conducted follow-ups using instruments at La Silla Observatory
in Chile, which confirmed the planet's existence and provided orbital and physical characteristics. The planet's discovery was published on April 14, 2011.
At the time of its discovery, WASP-43b had an orbital period
of approximately 0.8 days (19.2 hours), the second shortest orbit ever detected, surpassed only by WASP-19b
. In addition, at the time of discovery, WASP-43b was the most closely orbiting Hot Jupiter known, a phenomenon that can most likely be explained by its host star's low mass.
, a British organization working to discover transiting planets across the entirety of the sky. In particular, WASP-43 was observed first by the leg of WASP-South at the South African Astronomical Observatory
between January and May 2009.
Later observation by both SuperWASPs in the Northern and Southern Hemispheres led to the collection of 13,768 data points between January and May 2010 and to the use of the CORALIE spectrograph
at La Silla Observatory
in Chile. Fourteen measurements using the radial velocity method confirmed WASP-43b as a planet, revealing its mass in the process. The use of La Silla's TRAPPIST
telescope helped the science team working on the planet to create a light curve
of the planet's transit in December 2010.
The planet's discovery was published in the journal Astronomy and Astrophysics
on April 14, 2011.
s (261 light years) away. The star has a mass
of 0.58 times that of the Sun, but is more diffuse with a radius of 0.93 times that of the Sun. The star's effective temperature
is 4400 K, making the star cooler than the Sun, and is metal-poor with regards to the Sun because it has a metallicity
of [Fe/H] = -0.05 (89% the amount of iron in the Sun). The star is young, and is estimated to be 598 million years old (as compared to the Sun's 4.6 billion years). Analysis of emission lines have indicated that WASP-43 is an active star.
WASP-43 has one detected planet in its orbit, WASP-43b. The star has an apparent magnitude
of 12.4, and thus is too faint to be seen with the unaided eye from Earth.
with a mass of 1.78 times the mass of Jupiter
, but a radius of 0.93 times that of Jupiter's. The planet orbits its host star at a mean distance of 0.0142 AU
every 0.813475 days (19.5234 hours); this orbital period
, at the time of WASP-43b's discovery, was the second-shortest orbit yet detected, surpassed only by WASP-19b
. In addition, WASP-43b had the closest orbit to its host star (among Hot Jupiters) at the time of its discovery, comparable only to the Super-Earth
planet GJ 1214b and to the planetary candidate orbiting KOI-961. While Hot Jupiters are known to have small orbital periods, planets with exceptionally small periods below three or four days are extremely rare; however, in the case of WASP-43b, the planet's proximity can be explained because its host star has a very low mass. The rarity of systems like that of WASP-43 and its planet suggest that Hot Jupiters do not usually occur around low-mass stars, or that such planets cannot maintain stable orbits around such stars.
WASP-43b, along with the planets WASP-19b and WASP-18b
, conflicted with currently accepted models of tidal movements derived from observations of the orbits of binary star
systems. Revisions to the model with regard to planets were proposed to help the models conform to the orbital parameters of these planets.
In comparison, planet Mercury
has an orbital period of 87.97 days and lies at a mean distance of 0.387 AU from the Sun.
WASP-43
WASP-43 is a K-type star in the Sextans constellation. It is almost the same size as the Sun, but approximately half the mass. WASP-43 has one known planet in orbit, a Hot Jupiter called WASP-43b. At the time of publishing of WASP-43b's discovery on April 15, 2011, the planet was the most closely...
in the constellation Sextans. The planet is a Hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
with a mass almost twice that of Jupiter, but a radius that is slightly less than Jupiter's. WASP-43b was flagged as a candidate by 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 before they conducted follow-ups using instruments at La Silla Observatory
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory organisation, and several others are partly maintained by ESO...
in Chile, which confirmed the planet's existence and provided orbital and physical characteristics. The planet's discovery was published on April 14, 2011.
At the time of its discovery, WASP-43b had an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of approximately 0.8 days (19.2 hours), the second shortest orbit ever detected, surpassed only by WASP-19b
WASP-19b
WASP-19b is an extrasolar planet, notable for possessing the shortest orbital period of any known planetary body: 0.7888399 days or approximately 18.932 hours....
. In addition, at the time of discovery, WASP-43b was the most closely orbiting Hot Jupiter known, a phenomenon that can most likely be explained by its host star's low mass.
Observational history
WASP-43 was first flagged as host to a potential transiting event (when a body crosses in front of and dims its host star) by data collected by 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:...
, a British organization working to discover transiting planets across the entirety of the sky. In particular, WASP-43 was observed first by the leg of WASP-South at the South African Astronomical Observatory
South African Astronomical Observatory
South African Astronomical Observatory is the national center for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's function is to conduct research in astronomy and astrophysics...
between January and May 2009.
Later observation by both SuperWASPs in the Northern and Southern Hemispheres led to the collection of 13,768 data points between January and May 2010 and to the use of the CORALIE spectrograph
CORALIE spectrograph
The CORALIE spectrograph is an echelle type spectrograph used for astronomy. This instrument used with a telescope to measure star spectra for the Doppler effect to detect the presence of extrasolar planets by the radial velocity method...
at La Silla Observatory
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory organisation, and several others are partly maintained by ESO...
in Chile. Fourteen measurements using the radial velocity method confirmed WASP-43b as a planet, revealing its mass in the process. The use of La Silla's TRAPPIST
TRAPPIST
TRAPPIST is Belgian robotic telescope in Chile which came online in 2010, and is an acronym for TRAnsiting Planets and PlanetesImals Small Telescope, so named in homage to Trappist beer produced in the Belgian region. Situated high in the Chilean mountains at La Silla Observatory, it is actually...
telescope helped the science team working on the planet 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...
of the planet's transit in December 2010.
The planet's discovery was published 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...
on April 14, 2011.
Host star
WASP-43 is a K-type star in the Sextans constellation that is about 80 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 (261 light years) away. The star has a mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
of 0.58 times that of the Sun, but is more diffuse with a radius of 0.93 times that of the Sun. The star's 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 4400 K, making the star cooler than the Sun, and is metal-poor with regards to the Sun because it has a 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...
of [Fe/H] = -0.05 (89% the amount of iron in the Sun). The star is young, and is estimated to be 598 million years old (as compared to the Sun's 4.6 billion years). Analysis of emission lines have indicated that WASP-43 is an active star.
WASP-43 has one detected planet in its orbit, WASP-43b. The star 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 12.4, and thus is too faint to be seen with the unaided eye from Earth.
Characteristics
WASP-43b is a dense Hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
with a mass of 1.78 times 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....
, but a radius of 0.93 times that of Jupiter's. The planet orbits its host star at a mean distance of 0.0142 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
every 0.813475 days (19.5234 hours); this orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
, at the time of WASP-43b's discovery, was the second-shortest orbit yet detected, surpassed only by WASP-19b
WASP-19b
WASP-19b is an extrasolar planet, notable for possessing the shortest orbital period of any known planetary body: 0.7888399 days or approximately 18.932 hours....
. In addition, WASP-43b had the closest orbit to its host star (among Hot Jupiters) at the time of its discovery, comparable only to the Super-Earth
Super-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...
planet GJ 1214b and to the planetary candidate orbiting KOI-961. While Hot Jupiters are known to have small orbital periods, planets with exceptionally small periods below three or four days are extremely rare; however, in the case of WASP-43b, the planet's proximity can be explained because its host star has a very low mass. The rarity of systems like that of WASP-43 and its planet suggest that Hot Jupiters do not usually occur around low-mass stars, or that such planets cannot maintain stable orbits around such stars.
WASP-43b, along with the planets WASP-19b and WASP-18b
WASP-18b
WASP-18b is an extrasolar planet that is notable for having an orbital period of less than one day. It has a mass equal to 10 Jupiter masses, just below the boundary line between planets and brown dwarfs, about 13 Jupiter masses. Due to tidal deceleration, it is expected to spiral towards and...
, conflicted with currently accepted models of tidal movements derived from observations of the orbits of binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
systems. Revisions to the model with regard to planets were proposed to help the models conform to the orbital parameters of these planets.
In comparison, 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...
has an orbital period of 87.97 days and lies at a mean distance of 0.387 AU from the Sun.