HIP 13044 b
Encyclopedia
HIP 13044 b is a Jupiter
-like extrasolar planet
orbiting the old and metal-poor red giant
star HIP 13044
, which is situated approximately 2,000 light years
away from the Earth in the constellation Fornax
. Its discovery was announced on November 18, 2010 after observations using the FEROS spectrograph at La Silla Observatory
. According to evolutionary theories, HIP 13044 was formed in another galaxy
, and became part of the Milky Way
when the star's parent galaxy was absorbed by our own between six and nine billion years ago, the remnants of the galaxy forming the Helmi stream
. The planet has a very irregular orbit that is probably derived from the gravitational instabilities associated with HIP 13044's transition into the red giant
phase of its lifetime. At the time of its discovery, HIP 13044 b orbited what was noted as the oldest and most metal-poor star yet discovered.
. HIP 13044 b, the discovered planet, is the first time that a planetary system
has been discovered in a stellar stream
of extragalactic origin.
Using the FEROS spectrograph of the 2.2m MPG/ESO telescope
at the La Silla Observatory
in Chile, the science team that discovered the planet took thirty-six radial velocity measurements, a process that involves detecting small wobbles in a star caused by a planet as it tugs on it. The science team analyzed their observations in search of false positive alternatives that could also explain the signals detected by FEROS using photometric
measurements that were taken and publicly released by SuperWASP
, an organization that searches for transiting planets. The team compared the oscillations that HIP 13044 undergoes to the absence of the aforementioned oscillation at a sixteen day interval, and determined that the most likely reason for the blockage of the signal was the presence of a planetary companion. It was also determined that the planet was most likely not captured from another star in the Milky Way after Helmi stream became a part of the galaxy, implying that HIP 13044 b indeed originated outside the Milky Way.
The discovery of the planet may also suggest the need for rethinking issues in planet formation and survival, since it is the first planet ever discovered to be circling a star that is both very old and extremely metal-poor. The planet thus challenges the core-accretion model of planet formation, given that it may be unlikely a planetary core of sufficient mass was formed, and may signify it was formed via the competing disk instability model of planet formation. The planet's discovery was announced on November 18, 2010.
, a stellar stream consisting of stars that originated in a dwarf galaxy that collided and merged with the Milky Way between six and nine billion years ago. The star is rotating somewhat quickly, possibly indicating that it may have swallowed its inner planets during its red giant
phase. It has an eccentric galactic orbit, with a distance from 7 to 16 kiloparsecs. HIP 13044 has a mass
of 0.8 times that of the Sun and a radius that is 6.7 times that of the Sun, making it a very diffuse star. The star is estimated to have an effective temperature
of 6025 K, making it hotter than the Sun; however, with a metallicity
of [Fe/H] = −2.09, the star is extremely iron-deficient, having approximately 0.008 times the amount of iron measured in the Sun's spectrum. HIP 13044 is an old star, and is estimated to be at most nine billion years old, nearly twice the age of the Sun. Stars of this age, metallicity, and evolved stage are not known nor expected to have planets according to current theories on planetary formation.
The star is now in the final stages of its life as a horizontal branch
star, fusing helium
in its core. It is likely that the planet orbited farther away from the star before its red giant phase, and arrived at its current location due to frictional interactions with the star's outer gas envelope. As the star is expected to undergo another phase of expansion before becoming a white dwarf
, the planet's ultimate fate is uncertain.
HIP 13044 is situated at a distance of 701 parsec
s (2,286 light years) from Earth. It has an apparent magnitude
of 9.94, and thus is not visible from Earth with the unaided eye.
with a mass
of 1.25 times that of Jupiter. The planet orbits at a distance of 0.116 AU
every 16.2 days. HIP 13044 b has a large orbital eccentricity
of 0.25, and thus has a very elliptical orbit. The planet's orbital eccentricity is of special note, for such an eccentric orbit is not typical or predicted for planets of its kind. It is believed that an unevenly distributed pattern of mass loss may have shifted the planet's orbit to its present pattern, or that a third body in the system is manipulating HIP 13044 b's orbit.
To compare, Mercury
orbits the Sun at a distance of 0.387 AU every 87.97 days with an orbital eccentricity of 0.2056.
HIP 13044 b may have been part of a multiplanetary system before its host star entered its red giant phase. The system's planets were most likely consumed by the expanding stellar envelope
of the star. The gravitational disturbances caused by the expanding stellar envelope could have caused HIP 13044 b's orbit to deteriorate until it spiraled into its present, extremely close orbit.
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,...
-like extrasolar planet
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...
orbiting the old and metal-poor red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
star HIP 13044
HIP 13044
HIP 13044 is a red horizontal branch star about 2,300 light years away from the Earth in the constellation Fornax. The star is part of the Helmi stream, a former dwarf galaxy that merged with the Milky Way between six and nine billion years ago. As a result, HIP 13044 circles the galactic center...
, which is situated approximately 2,000 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
away from the Earth in the constellation Fornax
Fornax
Fornax is a constellation in the southern sky. Its name is Latin for furnace. It was created in the 18th century and is now one of the 88 modern constellations.-History:Fornax was formed by Nicolas Louis de Lacaille in 1756...
. Its discovery was announced on November 18, 2010 after observations using the FEROS spectrograph 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...
. According to evolutionary theories, HIP 13044 was formed in another galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, and became part of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
when the star's parent galaxy was absorbed by our own between six and nine billion years ago, the remnants of the galaxy forming the Helmi stream
Helmi stream
The Helmi stream is a stellar stream of the Milky Way Galaxy. It started as a dwarf galaxy, now absorbed by the Milky Way as a stream. It was discovered in 1999, is formed of old stars deficient in heavy elements and has a mass of 10 to 100 million solar masses...
. The planet has a very irregular orbit that is probably derived from the gravitational instabilities associated with HIP 13044's transition into the red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
phase of its lifetime. At the time of its discovery, HIP 13044 b orbited what was noted as the oldest and most metal-poor star yet discovered.
Discovery
The study that led to the discovery of the planet was performed by a team from the Max Planck Institute for AstronomyMax Planck Institute for Astronomy
The Max-Planck-Institut für Astronomie is a research institute of the Max Planck Society. It is located in Heidelberg, Baden-Württemberg, Germany near the top of the Koenigstuhl, adjacent to the historic Landessternwarte Heidelberg-Königstuhl astronomical observatory.The institute was founded in...
. HIP 13044 b, the discovered planet, is the first time that a planetary system
Planetary system
A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets , asteroids, meteoroids, comets, and cosmic dust...
has been discovered in a stellar stream
Stellar stream
This is a list of stellar streams. A stellar stream is an association of stars orbiting a galaxy that was once a globular cluster or dwarf galaxy that has now been torn apart and stretched out along its orbit by tidal forces...
of extragalactic origin.
Using the FEROS spectrograph of the 2.2m MPG/ESO telescope
MPG/ESO telescope
The MPG/ESO telescope is a 2.2-m ground-based telescope at the European Southern Observatory in La Silla, Chile. It was built by Zeiss and has been operating since 1984. It is on indefinite loan to the European Southern Observatory from the Max Planck Institute for Astronomy...
at the 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, the science team that discovered the planet took thirty-six radial velocity measurements, a process that involves detecting small wobbles in a star caused by a planet as it tugs on it. The science team analyzed their observations in search of false positive alternatives that could also explain the signals detected by FEROS using photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
measurements that were taken and publicly released by 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:...
, an organization that searches for transiting planets. The team compared the oscillations that HIP 13044 undergoes to the absence of the aforementioned oscillation at a sixteen day interval, and determined that the most likely reason for the blockage of the signal was the presence of a planetary companion. It was also determined that the planet was most likely not captured from another star in the Milky Way after Helmi stream became a part of the galaxy, implying that HIP 13044 b indeed originated outside the Milky Way.
The discovery of the planet may also suggest the need for rethinking issues in planet formation and survival, since it is the first planet ever discovered to be circling a star that is both very old and extremely metal-poor. The planet thus challenges the core-accretion model of planet formation, given that it may be unlikely a planetary core of sufficient mass was formed, and may signify it was formed via the competing disk instability model of planet formation. The planet's discovery was announced on November 18, 2010.
Host star
HIP 13044 is an F-type giant located in the Fornax constellation's Helmi streamHelmi stream
The Helmi stream is a stellar stream of the Milky Way Galaxy. It started as a dwarf galaxy, now absorbed by the Milky Way as a stream. It was discovered in 1999, is formed of old stars deficient in heavy elements and has a mass of 10 to 100 million solar masses...
, a stellar stream consisting of stars that originated in a dwarf galaxy that collided and merged with the Milky Way between six and nine billion years ago. The star is rotating somewhat quickly, possibly indicating that it may have swallowed its inner planets during its red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
phase. It has an eccentric galactic orbit, with a distance from 7 to 16 kiloparsecs. HIP 13044 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 0.8 times that of the Sun and a radius that is 6.7 times that of the Sun, making it a very diffuse star. The star is estimated to have 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 6025 K, making it hotter than the Sun; however, 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...
of [Fe/H] = −2.09, the star is extremely iron-deficient, having approximately 0.008 times the amount of iron measured in the Sun's spectrum. HIP 13044 is an old star, and is estimated to be at most nine billion years old, nearly twice the age of the Sun. Stars of this age, metallicity, and evolved stage are not known nor expected to have planets according to current theories on planetary formation.
The star is now in the final stages of its life as a horizontal branch
Horizontal branch
The horizontal branch is a stage of stellar evolution which immediately follows the red giant branch in stars whose masses are similar to the Sun's...
star, fusing helium
Triple-alpha process
The triple alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei are transformed into carbon.Older stars start to accumulate helium produced by the proton–proton chain reaction and the carbon–nitrogen–oxygen cycle in their cores...
in its core. It is likely that the planet orbited farther away from the star before its red giant phase, and arrived at its current location due to frictional interactions with the star's outer gas envelope. As the star is expected to undergo another phase of expansion before becoming a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
, the planet's ultimate fate is uncertain.
HIP 13044 is situated at a distance of 701 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 (2,286 light years) 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...
of 9.94, and thus is not visible from Earth with the unaided eye.
Characteristics
HIP 13044 b is a Hot JupiterHot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
with 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....
of 1.25 times that of Jupiter. The planet orbits at a distance of 0.116 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
every 16.2 days. HIP 13044 b has a large 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 0.25, and thus has a very elliptical orbit. The planet's orbital eccentricity is of special note, for such an eccentric orbit is not typical or predicted for planets of its kind. It is believed that an unevenly distributed pattern of mass loss may have shifted the planet's orbit to its present pattern, or that a third body in the system is manipulating HIP 13044 b's orbit.
To compare, 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...
orbits the Sun at a distance of 0.387 AU every 87.97 days with an orbital eccentricity of 0.2056.
HIP 13044 b may have been part of a multiplanetary system before its host star entered its red giant phase. The system's planets were most likely consumed by the expanding stellar envelope
Stellar Envelope
Stellar envelope may mean:* Part of the star where fusion reactions are not running* Common envelope in a binary system...
of the star. The gravitational disturbances caused by the expanding stellar envelope could have caused HIP 13044 b's orbit to deteriorate until it spiraled into its present, extremely close orbit.