HAT-P-32b
Encyclopedia
HAT-P-32b is a planet in the orbit of the G-type or F-type star HAT-P-32, which is approximately 1,044 light years away from Earth. HAT-P-32b was first recognized as a possible planet by the planet-searching HATNet Project
in 2004, although difficulties in measuring its radial velocity
prevented astronomers from verifying the planet until after three years of observation. The Blendanal program helped to rule out most of the alternatives that could explain what HAT-P-32b was, leading astronomers to determine that HAT-P-32b was most likely a planet. The discovery of HAT-P-32b and of HAT-P-33b
was submitted to a journal on June 6, 2011.
The planet is considered a Hot Jupiter
, and although it is slightly less massive than Jupiter, it is bloated to nearly twice Jupiter's size. At the time of its discovery, HAT-P-32b had one of the largest radii known amongst extrasolar planets. This phenomenon, which has also been observed in planets like WASP-17b
and HAT-P-33b
, has shown that something more than temperature is influencing why these planets become so large.
, an organization in search of transiting planets, or planets that cross in front of their host stars as seen from Earth. However, attempts to confirm the planetary candidate were extremely difficult because of a high level of jitter
(a random, shaky deviation in the measurements of HAT-P-32's radial velocity
) present in the star's observations. High-level jitter prevented the most common technique, that of bisector analysis, from revealing the star's radial velocity with enough certainty to confirm the planet's existence.
The spectrum
of HAT-P-32 was collected using the digital speedometer on Arizona's Fred Lawrence Whipple Observatory
(FLWO). Analysis of the data found that HAT-P-32 was a single, moderately rotating dwarf star
. Some of its parameters were also derived, including its effective temperature
and surface gravity
.
Between August 2007 and December 2010, twenty-eight spectra were collected using the High Resolution Echelle Spectrometer (HIRES) at the W.M. Keck Observatory in Hawaii. Twenty-five of these spectra were used to deduce HAT-P-32's radial velocity. To compensate for jitter, a greater number of spectra than that the usual for planetary candidates was collected. From this, it was concluded that stellar activity (and not the presence of yet-undiscovered planets) was the cause of the jitter.
Because astronomers concluded that the use of radial velocity could not, alone, establish the existence of planet HAT-P-32b, the KeplerCam CCD instrument on FLWO's 1.2m telescope was used to take photometric
observations of HAT-P-32. The data collected using KeplerCam CCD helped astronomers constructed HAT-P-32's light curve
. The light curve displayed a slight dimming at a point where HAT-P-32b was believed to transit its star.
The astronomers utilized Blendanal, a program used to eliminate the possibilities of false positives. This process serves a similar purpose to the Blender technique, which was used to verify some planets discovered by the Kepler spacecraft. In doing so, HAT-P-32's planet-like signature was found to not be caused by either a hierarchical triple star system or by a mixture of light between a bright single star and that of a binary star
in the background. Although the possibility that HAT-P-32 is actually a binary star with a dim secondary companion nearly indistinguishable from the primary companion could not be ruled out, HAT-P-32b was confirmed as a planet based on the Blendanal analysis.
HAT-P-32b had one of the highest radii known amongst planets at the time of its discovery. Like planets HAT-P-33b
and WASP-17b
, which are similarly inflated, the mechanism behind this is unknown; it is not solely related to temperature, which is known to have an effect. This is especially clear when compared to WASP-18b
, a planet that is hotter than the aforementioned HAT and WASP planets, because despite its temperature its radius is far lower than that of its counterparts.
Because of the high jitter of the star, the best way to collect more data on HAT-P-32b would be to observe an occultation
of HAT-P-32b behind its star using the Spitzer Space Telescope
.
HAT-P-32b's discovery was reported with that of HAT-P-33b in the Astrophysical Journal
. The discovery paper was submitted on June 6, 2011.
located some 320 parsec
s (1,044 light years) away from Earth. With 1.176 solar mass
es and 1.387 solar radii, HAT-P-32 is both larger and more massive than the Sun. HAT-P-32's effective temperature is 6001 K, making it slightly hotter than the Sun, although it is younger, at an estimated age of 3.8 billion years. HAT-P-32 is metal-poor; its measured metallicity
is [Fe/H] = -0.16, which means that it has 69% the iron content of the Sun. The star's surface gravity is determined to be 4.22, while its luminosity
suggests that it emits 2.43 times the amount of energy that the Sun emits. These parameters are adopted given the condition that the planet HAT-P-32b has an irregular (eccentric
) orbit.
HAT-P-32 has an apparent magnitude
of 11.29, which makes it invisible to eye of unaided observer standing on Earth.
A very high level of jitter has been detected in the star's spectrum. Because this jitter disrupts the ability to determine radial velocity measurements with high-precision accuracy, there is a possibility that HAT-P-32 is actually a binary star system, where the brighter companion visually masks the presence of a secondary, dimmer companion. If this is the case, then HAT-P-32's dimmer constituent probably has a mass that is under half of the Sun's mass.
Other planets with orbital period
s that are smaller than that of HAT-P-32b's orbit may be present in this system. However, when the discovery of the planet was published, not enough radial velocity measurements had been collected to determine if this was the case.
that has 0.941 Jupiter mass
es and 2.037 Jupiter radii. In other words, HAT-P-32b is slightly less massive than Jupiter is, although it is nearly twice Jupiter's size. The planet's average distance from its host star is 0.0344 AU
, or approximately 3% of the mean distance between the Earth and the Sun. It completes an orbit every 2.150009 days (51.6 hours). HAT-P-32b has an equilibrium temperature of 1888 K, which is fifteen times hotter than Jupiter's equilibrium temperature.
Many of the described characteristics are derived on the assumption that HAT-P-32b has an orbit that is elliptical (eccentric). The best fit for HAT-P-32b's orbital eccentricity is 0.163, denoting a slightly elliptical orbit, although the jitter effect observed in its host star has made the planet's eccentricity difficult to accurately find. The discoverers have also derived the planet's characteristics assuming that the planet has a circular orbit, although they have given preference to the elliptical model.
Because of HAT-P-32b's orbital inclination with respect to Earth is 88.7º, the planet is seen almost edge-on with respect to Earth. It has been found to transit its host star.
HATNet Project
The Hungarian Automated Telescope Network project is a network of six small fully automated "HAT" telescopes. The scientific goal of the project is to detect and characterize extrasolar planets using the transit method. This network is used also to find and follow bright variable stars...
in 2004, although difficulties in measuring its 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...
prevented astronomers from verifying the planet until after three years of observation. The Blendanal program helped to rule out most of the alternatives that could explain what HAT-P-32b was, leading astronomers to determine that HAT-P-32b was most likely a planet. The discovery of HAT-P-32b and of HAT-P-33b
HAT-P-33b
HAT-P-33b is a planet in the orbit of HAT-P-33, which lies 1,367 light years away from Earth. Its discovery was reported in June 2011, although it was suspected to be a planet as early as 2004...
was submitted to a journal on June 6, 2011.
The planet is considered a Hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
, and although it is slightly less massive than Jupiter, it is bloated to nearly twice Jupiter's size. At the time of its discovery, HAT-P-32b had one of the largest radii known amongst extrasolar planets. This phenomenon, which has also been observed in planets like 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...
and HAT-P-33b
HAT-P-33b
HAT-P-33b is a planet in the orbit of HAT-P-33, which lies 1,367 light years away from Earth. Its discovery was reported in June 2011, although it was suspected to be a planet as early as 2004...
, has shown that something more than temperature is influencing why these planets become so large.
Discovery
It had been suggested that a planet was in the orbit of the star HAT-P-32 as early as 2004; these observations were collected by the six-telescope HATNet ProjectHATNet Project
The Hungarian Automated Telescope Network project is a network of six small fully automated "HAT" telescopes. The scientific goal of the project is to detect and characterize extrasolar planets using the transit method. This network is used also to find and follow bright variable stars...
, an organization in search of transiting planets, or planets that cross in front of their host stars as seen from Earth. However, attempts to confirm the planetary candidate were extremely difficult because of a high level of jitter
Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of...
(a random, shaky deviation in the measurements of HAT-P-32'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...
) present in the star's observations. High-level jitter prevented the most common technique, that of bisector analysis, from revealing the star's radial velocity with enough certainty to confirm the planet's existence.
The 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...
of HAT-P-32 was collected using the digital speedometer on Arizona's Fred Lawrence Whipple Observatory
Fred Lawrence Whipple Observatory
The Fred Lawrence Whipple Observatory is an astronomical observatory owned and operated by the Smithsonian Astrophysical Observatory and is their largest field installation outside of their main site in Cambridge, MA...
(FLWO). Analysis of the data found that HAT-P-32 was a single, moderately rotating 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....
. Some of its parameters were also derived, including its 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...
and surface gravity
Surface gravity
The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in...
.
Between August 2007 and December 2010, twenty-eight spectra were collected using the High Resolution Echelle Spectrometer (HIRES) at the W.M. Keck Observatory in Hawaii. Twenty-five of these spectra were used to deduce HAT-P-32's radial velocity. To compensate for jitter, a greater number of spectra than that the usual for planetary candidates was collected. From this, it was concluded that stellar activity (and not the presence of yet-undiscovered planets) was the cause of the jitter.
Because astronomers concluded that the use of radial velocity could not, alone, establish the existence of planet HAT-P-32b, the KeplerCam CCD instrument on FLWO's 1.2m telescope was used to take photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
observations of HAT-P-32. The data collected using KeplerCam CCD helped astronomers constructed HAT-P-32's 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...
. The light curve displayed a slight dimming at a point where HAT-P-32b was believed to transit its star.
The astronomers utilized Blendanal, a program used to eliminate the possibilities of false positives. This process serves a similar purpose to the Blender technique, which was used to verify some planets discovered by the Kepler spacecraft. In doing so, HAT-P-32's planet-like signature was found to not be caused by either a hierarchical triple star system or by a mixture of light between a bright single star and that of a 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...
in the background. Although the possibility that HAT-P-32 is actually a binary star with a dim secondary companion nearly indistinguishable from the primary companion could not be ruled out, HAT-P-32b was confirmed as a planet based on the Blendanal analysis.
HAT-P-32b had one of the highest radii known amongst planets at the time of its discovery. Like planets HAT-P-33b
HAT-P-33b
HAT-P-33b is a planet in the orbit of HAT-P-33, which lies 1,367 light years away from Earth. Its discovery was reported in June 2011, although it was suspected to be a planet as early as 2004...
and 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...
, which are similarly inflated, the mechanism behind this is unknown; it is not solely related to temperature, which is known to have an effect. This is especially clear when compared to 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...
, a planet that is hotter than the aforementioned HAT and WASP planets, because despite its temperature its radius is far lower than that of its counterparts.
Because of the high jitter of the star, the best way to collect more data on HAT-P-32b would be to observe an 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...
of HAT-P-32b behind its star using 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...
.
HAT-P-32b's discovery was reported with that of HAT-P-33b 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....
. The discovery paper was submitted on June 6, 2011.
Host star
HAT-P-32, or GSC 3281-00800, is a G-type or F-type dwarf starDwarf 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....
located some 320 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 (1,044 light years) away from Earth. With 1.176 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 1.387 solar radii, HAT-P-32 is both larger and more massive than the Sun. HAT-P-32's effective temperature is 6001 K, making it slightly hotter than the Sun, although it is younger, at an estimated age of 3.8 billion years. HAT-P-32 is metal-poor; its measured 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] = -0.16, which means that it has 69% the iron content of the Sun. The star's surface gravity is determined to be 4.22, while its luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
suggests that it emits 2.43 times the amount of energy that the Sun emits. These parameters are adopted given the condition that the planet HAT-P-32b has an irregular (eccentric
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...
) orbit.
HAT-P-32 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 11.29, which makes it invisible to eye of unaided observer standing on Earth.
A very high level of jitter has been detected in the star's spectrum. Because this jitter disrupts the ability to determine radial velocity measurements with high-precision accuracy, there is a possibility that HAT-P-32 is actually a binary star system, where the brighter companion visually masks the presence of a secondary, dimmer companion. If this is the case, then HAT-P-32's dimmer constituent probably has a mass that is under half of the Sun's mass.
Other planets with 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...
s that are smaller than that of HAT-P-32b's orbit may be present in this system. However, when the discovery of the planet was published, not enough radial velocity measurements had been collected to determine if this was the case.
Characteristics
HAT-P-32b is a Hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
that has 0.941 Jupiter 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....
es and 2.037 Jupiter radii. In other words, HAT-P-32b is slightly less massive than Jupiter is, although it is nearly twice Jupiter's size. The planet's average distance from its host star is 0.0344 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, or approximately 3% of the mean distance between the Earth and the Sun. It completes an orbit every 2.150009 days (51.6 hours). HAT-P-32b has an equilibrium temperature of 1888 K, which is fifteen times hotter than Jupiter's equilibrium temperature.
Many of the described characteristics are derived on the assumption that HAT-P-32b has an orbit that is elliptical (eccentric). The best fit for HAT-P-32b's orbital eccentricity is 0.163, denoting a slightly elliptical orbit, although the jitter effect observed in its host star has made the planet's eccentricity difficult to accurately find. The discoverers have also derived the planet's characteristics assuming that the planet has a circular orbit, although they have given preference to the elliptical model.
Because of HAT-P-32b's orbital inclination with respect to Earth is 88.7º, the planet is seen almost edge-on with respect to Earth. It has been found to transit its host star.