HD 205739 b
Encyclopedia
HD 205739 b is an extrasolar planet
located approximately 295 light-year
s away in the constellation
of Piscis Austrinus
, orbiting the star
HD 205739
. This planet has a minimum mass
37% more than Jupiter
and orbits 90% of the distance between the Earth
and the Sun
. The planet has a very elliptical orbit, which has led its discoverers to postulate that the planet's surface temperature varies by about 100 K along the entire orbit. This planet was reported on September 5, 2008 after its discovery at Las Campanas Observatory
, where the planet was observed for years by the N2K Consortium
while using the Magellan Telescopes
. Follow-up observations collected the radial velocity
measurements necessary to confirm the candidate as a planet.
. The star was also observed by Hipparcos
, which released its catalogue in 1997. The observations that led to the discovery of the planet HD 205739 b started when the N2K Consortium
started an extended search for planets around 300 stars not usually targeted by Doppler spectroscopy
surveys. In the case of HD 205739, the star was observed using the Magellan Telescopes
at Las Campanas Observatory
in Chile. HD 205739 was selected primarily because it was a metal-rich star; the N2K collaboration biased their search towards metal-rich stars with closely orbiting Jupiter-size planets, hoping to find a connection between a star's metallicity
and its planets' masses.
HD 205739 was flagged originally as a candidate hosting a Hot Jupiter
, which is a large gas giant that orbits closely to its star, although later observations suggested that the planetary candidate orbited further out over the next 3.5 years of observation.
The star was studied through the Magellan Inamori Kyocera Echelle spectrograph's (MIKE) ability to use Doppler spectroscopy
to measure radial velocity
. Twenty-four measurements were recorded for HD 205739. The measurements were analyzed for accuracy. They were then used to derive the planet's characteristics, which led to the planet's confirmation.
The team of astronomers, which were from the United States, Chile, and the Vatican City, sent the paper to the Astronomical Journal
on April 7, 2008. The paper was accepted, and was later published on October 7, 2008.
that is 1.22 times the mass of the Sun and a size that is 1.33 times the radius of the Sun. In other words, it is slightly more massive and slightly larger than the Sun is. With an effective temperature
of 6176 K, HD 205739 is also hotter than the Sun, although it is younger, at an estimated age of 2.84 billion years. The star is rich in iron; its measured metallicity
is [Fe/H] = 0.19, or 1.55 times the iron detected in the Sun. After analysis of HD 205739's spectrum, it can be concluded that HD 205739's chromosphere
(its outermost layer) is not active. HD 205739 cannot be seen from Earth with the naked eye
because the star has an apparent magnitude
(V) of 8.56.
is 1.37 times the mass of Jupiter
. The planet has been found to orbit its host star every 279.8 days at a distance of 0.896 AU
, which is approximately 89.6% of the mean distance between the Sun and the Earth. HD 205739 b has a mildly elliptical orbit, given its orbital eccentricity
of 0.27. The planet's elliptical orbit is typical with respect to discovered planets whose orbits are longer than twenty days and have not grown circular because of tidal force
s. According to its discoverers, HD 205739 b's elongated orbit causes its surface temperature to fluctuate by up to 100 K.
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...
located approximately 295 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Piscis Austrinus
Piscis Austrinus
Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish" in contrast with the larger constellation Pisces, which represents a pair of fishes. Prior to the 20th century, it was also known as Piscis Notius...
, orbiting the star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
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....
. This planet has a minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
37% more than Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
and orbits 90% of the distance between the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and 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...
. The planet has a very elliptical orbit, which has led its discoverers to postulate that the planet's surface temperature varies by about 100 K along the entire orbit. This planet was reported on September 5, 2008 after its discovery at 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...
, where the planet was observed for years 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...
while using 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...
. Follow-up observations collected 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...
measurements necessary to confirm the candidate as a planet.
Discovery
HD 205739's designation is from the Henry Draper catalogueHenry Draper Catalogue
The Henry Draper Catalogue is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension , published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the...
. The star was also observed by 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...
, which released its catalogue in 1997. The observations that led to the discovery of the planet HD 205739 b started when 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...
started an extended search for planets around 300 stars not usually targeted by 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....
surveys. In the case of HD 205739, the star was observed using 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 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...
in Chile. HD 205739 was selected primarily because it was a metal-rich star; the N2K collaboration biased their search towards metal-rich stars with closely orbiting Jupiter-size planets, hoping to find a connection 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 its planets' masses.
HD 205739 was flagged originally as a candidate hosting a Hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
, which is a large gas giant that orbits closely to its star, although later observations suggested that the planetary candidate orbited further out over the next 3.5 years of observation.
The star was studied through the Magellan Inamori Kyocera Echelle spectrograph's (MIKE) ability to use 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....
to measure 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...
. Twenty-four measurements were recorded for HD 205739. The measurements were analyzed for accuracy. They were then used to derive the planet's characteristics, which led to the planet's confirmation.
The team of astronomers, which were from the United States, Chile, and the Vatican City, sent the paper to 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 April 7, 2008. The paper was accepted, and was later published on October 7, 2008.
Host star
HD 205739 is an F-type star with a massSolar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
that is 1.22 times the mass of the Sun and a size that is 1.33 times the radius of the Sun. In other words, it is slightly more massive and slightly larger than the Sun is. With 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 6176 K, HD 205739 is also hotter than the Sun, although it is younger, at an estimated age of 2.84 billion years. The star is rich in iron; 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] = 0.19, or 1.55 times the iron detected in the Sun. After analysis of HD 205739's spectrum, it can be concluded that HD 205739's chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....
(its outermost layer) is not active. HD 205739 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 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...
(V) of 8.56.
Characteristics
HD 205739 b is a Jupiter-size planet. The estimated minimum massMinimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
is 1.37 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....
. The planet has been found to orbit its host star every 279.8 days at a distance of 0.896 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, which is approximately 89.6% of the mean distance between the Sun and the Earth. HD 205739 b has a mildly elliptical orbit, given its 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 0.27. The planet's elliptical orbit is typical with respect to discovered planets whose orbits are longer than twenty days and have not grown circular because of tidal force
Tidal force
The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force per unit mass exerted on one body by a second body is not constant across its diameter, the side nearest to the second being more attracted by it than the side...
s. According to its discoverers, HD 205739 b's elongated orbit causes its surface temperature to fluctuate by up to 100 K.