HAT-P-33b
Encyclopedia
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. The planet is about three-fourths the mass of Jupiter, but is almost eighty percent larger than Jupiter is; this inflation has, as with the discovery of similar planets WASP-17b
and HAT-P-32b
, raised the question of what (other than temperature) causes these planets to become so large.
HAT-P-33b was difficult to confirm because its star experiences high jitter
, which disrupted the ability to obtain accurate measurements. As such, a greater number of radial velocity observations were collected to make the confirmation, although it was later determined that HAT-P-33b could not be determined using the radial velocity method. The planet's confirmation came about after the planet's light curve
was collected, and the Blendanal process ruled out most false positive scenarios.
collaboration, a project that searches the sky for planets in transit of, or crossing in front of, their host stars. The presence of a planet in HAT-P-33's orbit had been suspected as early as 2004, although high levels of jitter
were detected. This jitter
, or a random and shaky appearance that clouds the accuracy of measurements, made it difficult to easily verify the radial velocity
of the planetary candidate's host star, which usually leads summarily to the planet's confirmation.
As a start, the spectrum
of HAT-P-33 was composed using the digital speedometer at the 1.5 m Fred Lawrence Whipple Observatory
in Arizona. The collected data found that the star was a single dwarf star
exhibiting a slight rotation. Several of its parameters, including its effective temperature
and surface gravity
, were found. Additionally, the SOPHIE échelle spectrograph
at a 1.93m telescope at France's Haute-Provence Observatory
was used to observe the star. The resulting data invited the possibility that radial velocity measurements, which can exhibit anomalies that often indicate the presence of a planet, may have been because of background distortion (and not a planet). This possibility significantly complicated the ability of scientists to verify this planet. After the observations, follow-ups were postponed for several years.
Between September 2008 and December 2010, twenty-two spectra were collected using the High Resolution Echelle Spectrometer (HIRES) instrument at Hawaii's W.M. Keck Observatory. This data was used to derive HAT-P-33's radial velocity. A far greater number of spectra were gathered for HAT-P-33 than the number usually gathered for planetary candidates to compensate for the data's jitter effect. It was concluded that the jitter in the data was caused by stellar activity and not the presence of other planets.
It became apparent to the investigating science team that radial velocity data alone could not prove the existence of HAT-P-33b. As such, photometric
observations of HAT-P-33 were conducted using the Fred Lawrence Whipple Observatory's 1.2m telescope, which hosted the KeplerCam CCD instrument. This data was used to create the light curve
of HAT-P-33. In doing so, a slight dimming was observed where HAT-P-33b was believed to have transited its star.
Using a program called Blendanal, similar to the Blender technique used to verify the planets discovered by Kepler, the astronomers observing HAT-P-33 hoped to rule out false positive alternatives that could explain the planet-like signal seen in HAT-P-33's light curve and radial velocity. The use of Blendanal ruled out the possibilities that the signal was caused by that of a hierarchical triple star or a mixture between a bright star and a binary star
in the background. The possibility that HAT-P-33 is actually a binary star whose secondary companion is too dim to be distinguishable from the brighter star could not be ruled out. However, the data indicated that the planet HAT-P-33b did indeed exist.
The discoveries of the high-radii planets HAT-P-33b and HAT-P-32b
, along with that of WASP-17b
, contributed to the question of what factors, besides temperature, contribute to the large radii of these inflated planets. The discrepancy lies in planet WASP-18b
, which is far hotter than the newly discovered HAT planets and WASP-17b, but has a far smaller radius.
The discoveries of HAT-P-33b and HAT-P-32b were reported together in the Astrophysical Journal
. The paper was submitted on June 6, 2011. The authors of the discovery paper of the planets suggested the usage of the Spitzer Space Telescope
to observe the occultation
of HAT-P-33b behind its star to better define its characteristics.
s (1,367 light years) away from Earth. The star has 1.403 solar mass
es and 1.777 solar radii; the star is, in other words, 40% more massive than and 77% larger than the Sun. With an effective temperature of 6401 K, HAT-P-33 is hotter than the Sun. It is also more metal-rich, with a metallicity
that is measured at [Fe/H] = 0.05. This means that HAT-P-33 has 12% more iron than the amount measured in the Sun. HAT-P-33 is younger than the Sun, at an estimated age of 2.4 billion years. The surface gravity
of the star is determined to be 4.09. All the values above are determined with the assumption that planet HAT-P-33b has an irregular, or eccentric
, orbit.
HAT-P-33 has an apparent magnitude
of 11.89. It cannot be seen from Earth with the naked eye
because it is so dim.
Because high levels of jitter have been detected in the spectrum of HAT-P-33, the ability to collect the most sensitive radial velocity measurements possible has been dulled. The loss of accuracy has prevented astronomers from disregarding the possibility that HAT-P-33 is actually a binary star, where the secondary, dimmer companion is visually indistinguishable from the brighter primary companion. If this is the case, then the dimmer star in the HAT-P-33 system would have to have a mass that is less than 0.55 times that of the Sun.
It is possible that other planets with shorter orbital period
s than HAT-P-33b exist in the system. However, at the time of HAT-P-33b's discovery, not enough radial velocity measurements had been collected to determine if this is so.
es and 1.827 Jupiter radii. In other words, it is about three-fourths as massive as Jupiter, but is slightly less than twice Jupiter's size. HAT-P-33b orbits its star at an average distance of 0.0503 AU
, which is about 5% of the average distance between the Sun and Earth. This orbit is completed every 3.474474 days (83.39 hours). HAT-P-33b has an equilibrium temperature of 1838 K, which is almost fifteen times hotter than the measured equilibrium temperature of Jupiter (124 K).
The best fit for the shape of HAT-P-33b's orbit suggests that the orbit is slightly elliptical, as the planet's orbital eccentricity is fit to 0.148. However, because the star HAT-P-33 has such a high level of jitter, it is difficult to constrain the planet's eccentricity with accuracy. Most of the planet's defined characteristics are based on the assumption that HAT-P-33b has an elliptical orbit, although the planet's discoverers have also derived HAT-P-33b's characteristics on the assumption that the planet has a circular orbit. The elliptical model has been chosen because it is considered to be the most likely scenario.
HAT-P-33b has an orbital inclination of 86.7º as seen from Earth. The planet is, thus, almost edge-on when seen from Earth. The planet has been observed to transit its host star.
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-32b
HAT-P-32b
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...
, raised the question of what (other than temperature) causes these planets to become so large.
HAT-P-33b was difficult to confirm because its star experiences high 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...
, which disrupted the ability to obtain accurate measurements. As such, a greater number of radial velocity observations were collected to make the confirmation, although it was later determined that HAT-P-33b could not be determined using the radial velocity method. The planet's confirmation came about after the planet'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...
was collected, and the Blendanal process ruled out most false positive scenarios.
Discovery
HAT-P-33b's existence was first suggested after observations by the six-telescope HATnetHATNet 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...
collaboration, a project that searches the sky for planets in transit of, or crossing in front of, their host stars. The presence of a planet in HAT-P-33's orbit had been suspected as early as 2004, although high levels 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...
were detected. This 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...
, or a random and shaky appearance that clouds the accuracy of measurements, made it difficult to easily verify 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 planetary candidate's host star, which usually leads summarily to the planet's confirmation.
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-33 was composed using the digital speedometer at the 1.5 m 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...
in Arizona. The collected data found that the star was a single 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....
exhibiting a slight rotation. Several of its parameters, 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...
, were found. Additionally, 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 a 1.93m telescope at France's 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...
was used to observe the star. The resulting data invited the possibility that radial velocity measurements, which can exhibit anomalies that often indicate the presence of a planet, may have been because of background distortion (and not a planet). This possibility significantly complicated the ability of scientists to verify this planet. After the observations, follow-ups were postponed for several years.
Between September 2008 and December 2010, twenty-two spectra were collected using the High Resolution Echelle Spectrometer (HIRES) instrument at Hawaii's W.M. Keck Observatory. This data was used to derive HAT-P-33's radial velocity. A far greater number of spectra were gathered for HAT-P-33 than the number usually gathered for planetary candidates to compensate for the data's jitter effect. It was concluded that the jitter in the data was caused by stellar activity and not the presence of other planets.
It became apparent to the investigating science team that radial velocity data alone could not prove the existence of HAT-P-33b. As such, 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-33 were conducted using the Fred Lawrence Whipple Observatory's 1.2m telescope, which hosted the KeplerCam CCD instrument. This data was used to create the 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 HAT-P-33. In doing so, a slight dimming was observed where HAT-P-33b was believed to have transited its star.
Using a program called Blendanal, similar to the Blender technique used to verify the planets discovered by Kepler, the astronomers observing HAT-P-33 hoped to rule out false positive alternatives that could explain the planet-like signal seen in HAT-P-33's light curve and radial velocity. The use of Blendanal ruled out the possibilities that the signal was caused by that of a hierarchical triple star or a mixture between a bright star and 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. The possibility that HAT-P-33 is actually a binary star whose secondary companion is too dim to be distinguishable from the brighter star could not be ruled out. However, the data indicated that the planet HAT-P-33b did indeed exist.
The discoveries of the high-radii planets HAT-P-33b and HAT-P-32b
HAT-P-32b
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...
, along with that of 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...
, contributed to the question of what factors, besides temperature, contribute to the large radii of these inflated planets. The discrepancy lies in planet 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...
, which is far hotter than the newly discovered HAT planets and WASP-17b, but has a far smaller radius.
The discoveries of HAT-P-33b and HAT-P-32b were reported together 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 paper was submitted on June 6, 2011. The authors of the discovery paper of the planets suggested the usage of 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...
to observe the 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-33b behind its star to better define its characteristics.
Host star
HAT-P-33, or GSC 2461-00988, is an F-type star that lies 419 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 (1,367 light years) away from Earth. The star has 1.403 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 1.777 solar radii; the star is, in other words, 40% more massive than and 77% larger than the Sun. With an effective temperature of 6401 K, HAT-P-33 is hotter than the Sun. It is also more metal-rich, with 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...
that is measured at [Fe/H] = 0.05. This means that HAT-P-33 has 12% more iron than the amount measured in the Sun. HAT-P-33 is younger than the Sun, at an estimated age of 2.4 billion years. The 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...
of the star is determined to be 4.09. All the values above are determined with the assumption that planet HAT-P-33b has an irregular, or 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-33 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 11.89. It cannot be seen from Earth with 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"...
because it is so dim.
Because high levels of jitter have been detected in the spectrum of HAT-P-33, the ability to collect the most sensitive radial velocity measurements possible has been dulled. The loss of accuracy has prevented astronomers from disregarding the possibility that HAT-P-33 is actually a binary star, where the secondary, dimmer companion is visually indistinguishable from the brighter primary companion. If this is the case, then the dimmer star in the HAT-P-33 system would have to have a mass that is less than 0.55 times that of the Sun.
It is possible that other planets with shorter 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 than HAT-P-33b exist in the system. However, at the time of HAT-P-33b's discovery, not enough radial velocity measurements had been collected to determine if this is so.
Characteristics
HAT-P-33b is a planet that has 0.764 Jupiter massJupiter 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 1.827 Jupiter radii. In other words, it is about three-fourths as massive as Jupiter, but is slightly less than twice Jupiter's size. HAT-P-33b orbits its star at an average distance of 0.0503 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, which is about 5% of the average distance between the Sun and Earth. This orbit is completed every 3.474474 days (83.39 hours). HAT-P-33b has an equilibrium temperature of 1838 K, which is almost fifteen times hotter than the measured equilibrium temperature of Jupiter (124 K).
The best fit for the shape of HAT-P-33b's orbit suggests that the orbit is slightly elliptical, as the planet's orbital eccentricity is fit to 0.148. However, because the star HAT-P-33 has such a high level of jitter, it is difficult to constrain the planet's eccentricity with accuracy. Most of the planet's defined characteristics are based on the assumption that HAT-P-33b has an elliptical orbit, although the planet's discoverers have also derived HAT-P-33b's characteristics on the assumption that the planet has a circular orbit. The elliptical model has been chosen because it is considered to be the most likely scenario.
HAT-P-33b has an orbital inclination of 86.7º as seen from Earth. The planet is, thus, almost edge-on when seen from Earth. The planet has been observed to transit its host star.