HD 154672
Encyclopedia
HD 154672 is a yellow subgiant (spectral type G3 IV). It is about 65 parsec
s away from the Sun
that is larger than, but of a similar mass to, the Sun. However, HD 154672 is much older. The star is very metal-rich, which is one of the reasons why it was targeted for a planet search by the N2K Consortium
, which discovered the gas giant planet HD 154672 b
using Doppler Spectroscopy
; the discovery was reported in October 2008. The N2K collaboration chose HD 154672 primarily because it aimed to discover the correlation between a star's metallicity
and the mass of orbiting planets.
HD 154672 was targeted by the Magellan Telescopes
. It is the host of the first planet discovered from the telescopes by N2K.
, a collaboration of astronomers hoping to take radial velocity
measurements of previously untargeted stars using Doppler spectroscopy
; however, HD 154672 had been previously targeted by a series of surveys, and was previously included in the Henry Draper catalog and the catalog of the European Space Agency
's Hipparcos
satellite.
N2K deliberately biased its search towards closely orbiting Jupiter-size planets (Hot Jupiter
s) in the orbit of metal-rich stars, as the consortium hoped to discover how the mass of a planet relates to its host star's metal content. Initially, HD 154672 was noted as a host to a short-orbit Hot Jupiter, although additional observations revealed that the prospective planetary body had a longer orbit than previously expected, as revealed by the Magellan Telescopes
at Chile's Las Campanas Observatory
.
Use of the Magellan Clay telescope's Magellan Inamori Kyocera Echelle spectrograph (MIKE) helped collect sixteen radial velocity measurements for HD 154672; a team of American astronomers and one from the Vatican City used these measurements to confirm the existence of planet HD 154672 b
and to determine its mass.
The discovery of HD 154672's planet was reported in the Astronomical Journal
on October 7, 2008 along with a planet in the orbit of HD 205739
.
of 1.06 times that of the Sun and a radius that is 1.27 times that of the Sun. Thus, it is slightly larger than the Sun, although it has a similar mass. The star has an effective temperature
of 5714 K, slightly cooler than the Sun; however, it is far richer in iron, with a measured metallicity
of [Fe/H] = 0.26. This means that the star has 1.82 times more iron than the Sun does. HD 154672 is far older than the Sun, as its estimated gyrochronological age
is estimated at 9.28 billion years. HD 154672's spectrum suggests that the star's chromosphere
(its outer layer) is not active.
HD 154672 is located 65.8 parsec
s (214.6 light years) away from Earth. It has an apparent magnitude
(V) of 8.22, making the star too dim to see from Earth with the naked eye
. The star is slightly dimmer than planet Neptune
as perceived with the naked eye, which has an apparent magnitude of 7.78 at its brightest. The star's actual brightness is measured with an absolute magnitude
of 4.12, similar to that of the Sun.
, as it is a closely orbiting planet with a high mass. Specifically, HD 154672 has a mass
that is 5.02 times greater than Jupiter's mass. It also orbits at a distance of 0.6 AU
, or about 60% of the mean distance between the Earth and Sun. This orbit is completed every 163.91 days.
HD 154672 b has an orbital eccentricity
of 0.61, denoting a very elliptical orbit. The planet's discoverers noted that if water existed in the planet's atmosphere, it might change from a liquid state to a gaseous state as the planet swings closer to its host star, increasing its temperature.
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 away from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
that is larger than, but of a similar mass to, the Sun. However, HD 154672 is much older. The star is very metal-rich, which is one of the reasons why it was targeted for a planet search by the N2K Consortium
N2K Consortium
The N2K Consortium is a collaborative multinational effort by American, Chilean and Japanese astronomers to find additional extrasolar planets around stars that are...
, which discovered the gas giant planet HD 154672 b
HD 154672 b
HD 154672 b is an extrasolar planet located approximately 215 light-years away in the constellation of Ara, orbiting the metal-rich and aged star HD 154672. This planet has a minimum mass five times that of Jupiter and orbits at about 60% the distance between the Earth to the Sun...
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....
; the discovery was reported in October 2008. The N2K collaboration chose HD 154672 primarily because it aimed to discover the correlation between a 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...
and the mass of orbiting planets.
HD 154672 was targeted by the Magellan Telescopes
Magellan telescopes
The Magellan Telescopes are a pair of 6.5 m diameter optical telescopes located at Las Campanas Observatory in Chile. The two telescopes are named after the astronomer Walter Baade and the philanthropist Landon T...
. It is the host of the first planet discovered from the telescopes by N2K.
Observational history
HD 154672 was first targeted for a planet search in 2004 by the N2K ConsortiumN2K Consortium
The N2K Consortium is a collaborative multinational effort by American, Chilean and Japanese astronomers to find additional extrasolar planets around stars that are...
, a collaboration of astronomers hoping to take 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 of previously untargeted stars 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....
; however, HD 154672 had been previously targeted by a series of surveys, and was previously included in the Henry Draper catalog and the catalog of the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
's Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
satellite.
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
s) in the orbit of metal-rich stars, as the consortium hoped to discover how the mass of a planet relates to its host star's metal content. Initially, HD 154672 was noted as a host to a short-orbit Hot Jupiter, although additional observations revealed that the prospective planetary body had a longer orbit than previously expected, as revealed by the Magellan Telescopes
Magellan telescopes
The Magellan Telescopes are a pair of 6.5 m diameter optical telescopes located at Las Campanas Observatory in Chile. The two telescopes are named after the astronomer Walter Baade and the philanthropist Landon T...
at Chile's Las Campanas Observatory
Las Campanas Observatory
Las Campanas Observatory is an astronomical observatory owned and operated by the Carnegie Institution for Science It was established in 1969 and remains the primary observing site of that institution. The headquarters is located in La Serena, Chile and the observatory is in the southern Atacama...
.
Use of the Magellan Clay telescope's Magellan Inamori Kyocera Echelle spectrograph (MIKE) helped collect sixteen radial velocity measurements for HD 154672; a team of American astronomers and one from the Vatican City used these measurements to confirm the existence of planet HD 154672 b
HD 154672 b
HD 154672 b is an extrasolar planet located approximately 215 light-years away in the constellation of Ara, orbiting the metal-rich and aged star HD 154672. This planet has a minimum mass five times that of Jupiter and orbits at about 60% the distance between the Earth to the Sun...
and to determine its mass.
The discovery of HD 154672's planet was reported in the Astronomical Journal
Astronomical Journal
The Astronomical Journal is a peer-reviewed monthly scientific journal owned by the American Astronomical Society and currently published by Institute of Physics Publishing. It is one of the premier journals for astronomy in the world...
on October 7, 2008 along with a planet in the orbit of HD 205739
HD 205739
HD 205739 is a yellow-white dwarf . It is about 90 parsecs away from the Sun.A Jupiter-like planet has recently been detected in a Mercury-like eccentric orbit around this star....
.
Host star
HD 154672 is a sunlike G-type star that has a massSolar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
of 1.06 times that of the Sun and a radius that is 1.27 times that of the Sun. Thus, it is slightly larger than the Sun, although it has a similar mass. The star 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 5714 K, slightly cooler than the Sun; however, it is far richer in iron, with a 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...
of [Fe/H] = 0.26. This means that the star has 1.82 times more iron than the Sun does. HD 154672 is far older than the Sun, as its estimated gyrochronological age
Gyrochronological age
The gyrochronological age of a star is determined by using the rate at which the star spins to find its true age. The process of the star was presented by Søren Meibom, who used data collected by the Kepler spacecraft to present his findings in 2010 after he analyzed cluster NGC 6811....
is estimated at 9.28 billion years. HD 154672's spectrum suggests that the star's chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....
(its outer layer) is not active.
HD 154672 is located 65.8 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 (214.6 light years) away from Earth. It 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...
(V) of 8.22, making the star too dim to see 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"...
. The star is slightly dimmer than planet Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
as perceived with the naked eye, which has an apparent magnitude of 7.78 at its brightest. The star's actual brightness is measured with an absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
of 4.12, similar to that of the Sun.
Planetary system
HD 154672 b is a Hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
, as it is a closely orbiting planet with a high mass. Specifically, HD 154672 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 5.02 times greater than Jupiter's mass. It also orbits at a distance of 0.6 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, or about 60% of the mean distance between the Earth and Sun. This orbit is completed every 163.91 days.
HD 154672 b has an orbital eccentricity
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...
of 0.61, denoting a very elliptical orbit. The planet's discoverers noted that if water existed in the planet's atmosphere, it might change from a liquid state to a gaseous state as the planet swings closer to its host star, increasing its temperature.
See also
- HD 205739HD 205739HD 205739 is a yellow-white dwarf . It is about 90 parsecs away from the Sun.A Jupiter-like planet has recently been detected in a Mercury-like eccentric orbit around this star....
- HD 74156HD 74156HD 74156 is a yellow dwarf star in the constellation of Hydra, 211 light years from our solar system. It is known to be orbited by two giant planets.- Star :...
- 54 Piscium54 Piscium54 Piscium is an orange dwarf star approximately 36 light-years away in the constellation of Pisces. In 2002, an extrasolar planet was confirmed to be orbiting the star, and in 2006, a brown dwarf was also discovered orbiting it....
- HD 80606
- HD 37605HD 37605HD 37605 is an orange dwarf star located approximately 140 light years away in the constellation Orion. In 2004, a planet was found in orbit....
- HD 17156HD 17156HD 17156 is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. The Sun to star distance is 255.19 ly or 78.24 pc.The mass of the star is...
- HD 89744HD 89744HD 89744 is an F-dwarf star about 130 light years away in the constellation of Ursa Major. In April 2000, a planet was discovered by radial velocity method.- Stellar components :...