HIP 13044
Encyclopedia
HIP 13044 is a red horizontal branch
star about 2,300 light years (700 pc
) 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 at a highly irregular orbit with respect to the galactic plane
. HIP 13044 is slightly less massive than the Sun, but is approximately seven times its size. The star, which is estimated to be at least nine billion years old, has passed the red giant
phase. One planet, a Hot Jupiter
that has been designated HIP 13044 b
, has been discovered in the orbit of HIP 13044. There is evidence that other planets may have been present, but these planets were engulfed, a possible cause for HIP 13044's high rotational speed. At the time of its discovery, HIP 13044 was the most metal-poor
exoplanetary host star discovered.
first observed HIP 13044 using Fiber-fed Extended Range Optical Spectrograph (FEROS) at the European Southern Observatory
's La Silla Observatory
in Chile. The first follow-up led to the collection of 36 radial velocity
measurements taken between September 2009 and July 2010.
The team also used photometric
data that had been passively collected by and publicly released into the archive of the SuperWASP
collaboration, which had been observing the region where the star was located. In this data, HIP 13044 was found to oscillate; the signal was blocked roughly every sixteen days. Analysis of the SuperWASP and FEROS data led scientists to conclude that the planet HIP 13044 b
existed in the orbit of HIP 13044.
s (2,286 light years) away from Earth in the Helmi stream
—a group of low metallicity stars moving with large velocities relative to the Sun. The star follows an eccentric galactic orbit, with a distance from the galactic center ranging from 7 to 16 kiloparsecs. The orbit does not lie in galactic plane
, and can reach distances as high as 13 kpc above it. This indicates that it once was part of a satellite galaxy of the Milky Way
, which was disrupted 6–9 billion years ago. The star itself is estimated to be at least nine billion years old.
HIP 13044 is fairly evolved core helium burning star, which has already passed the red giant
stage of its evolution. It lies near the blue end of the red horizontal branch bordering the instability strip
. It surface temperature is about 6025 K and the radius is about 6.7 solar radii. The star is also estimated to be 0.8 solar mass
es. Having the rotation period of 5–6 days, HIP 13044 is a fast rotating star for its type. It is possible that this is because it may have swallowed inner planets during its red giant
phase.
The star has an apparent magnitude
of 9.94. It cannot be seen with the unaided eye.
that orbits its host star at a distance of 0.116 AU
(11.6% the mean distance between the Earth and the Sun). The planet completes and orbit every 16.2 days. HIP 13044 b has a mass estimated at 1.25 times that of
Jupiter. HIP 13044 b also has, with an orbital eccentricity
of 0.25, an elliptical orbit. HIP 13044 b's proximity to its host star is not unusual, but a close planet with such a high eccentricity is rare. One model suggests that HIP 13044 b is the remnant of a multi-planetary system that collapsed as HIP 13044 entered the red giant phase, and that the engulfing of inner planets caused irregularities that shifted HIP 13044 b's orbit; another model suggests that an asymmetrical distribution of mass in the star caused the same effect. At the time of its discovery, HIP 13044 b was found to orbit the most metal-poor star discovered to date.
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 about 2,300 light years (700 pc
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
) 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...
. The star is part of 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...
, a former dwarf galaxy
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
that merged with 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...
between six and nine billion years ago. As a result, HIP 13044 circles the galactic center at a highly irregular orbit with respect to the galactic plane
Galactic plane
The galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
. HIP 13044 is slightly less massive than the Sun, but is approximately seven times its size. The star, which is estimated to be at least nine billion years old, has passed 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. One planet, a Hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
that has been designated HIP 13044 b
HIP 13044 b
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...
, has been discovered in the orbit of HIP 13044. There is evidence that other planets may have been present, but these planets were engulfed, a possible cause for HIP 13044's high rotational speed. At the time of its discovery, HIP 13044 was the most metal-poor
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...
exoplanetary host star discovered.
Observational history
A science 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...
first observed HIP 13044 using Fiber-fed Extended Range Optical Spectrograph (FEROS) at the European Southern Observatory
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
's 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 first follow-up led to the collection of 36 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 taken between September 2009 and July 2010.
The team also used photometric
Photometry
Photometry can refer to:* Photometry , the science of measurement of visible light in terms of its perceived brightness to human vision...
data that had been passively collected by and publicly released into the archive of the 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:...
collaboration, which had been observing the region where the star was located. In this data, HIP 13044 was found to oscillate; the signal was blocked roughly every sixteen days. Analysis of the SuperWASP and FEROS data led scientists to conclude that the planet HIP 13044 b
HIP 13044 b
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...
existed in the orbit of HIP 13044.
Characteristics
HIP 13044 is an F-type star located approximately 701 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 (2,286 light years) away from Earth in 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...
—a group of low metallicity stars moving with large velocities relative to the Sun. The star follows an eccentric galactic orbit, with a distance from the galactic center ranging from 7 to 16 kiloparsecs. The orbit does not lie in galactic plane
Galactic plane
The galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
, and can reach distances as high as 13 kpc above it. This indicates that it once was part of a satellite galaxy 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...
, which was disrupted 6–9 billion years ago. The star itself is estimated to be at least nine billion years old.
HIP 13044 is fairly evolved core helium burning star, which has already passed 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...
stage of its evolution. It lies near the blue end of the red horizontal branch bordering the instability strip
Instability strip
The Instability strip is a nearly vertical region in the Hertzsprung–Russell diagram which is occupied by pulsating variable stars .The instability strip intersects the main sequence in the region of A...
. It surface temperature is about 6025 K and the radius is about 6.7 solar radii. The star is also estimated to be 0.8 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. Having the rotation period of 5–6 days, HIP 13044 is a fast rotating star for its type. It is possible that this is because it may have swallowed 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.
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...
of 9.94. It cannot be seen with the unaided eye.
Planetary system
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...
that orbits its host star 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....
(11.6% the mean distance between the Earth and the Sun). The planet completes and orbit every 16.2 days. HIP 13044 b has a mass estimated at 1.25 times that of
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....
Jupiter. HIP 13044 b also has, with 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 0.25, an elliptical orbit. HIP 13044 b's proximity to its host star is not unusual, but a close planet with such a high eccentricity is rare. One model suggests that HIP 13044 b is the remnant of a multi-planetary system that collapsed as HIP 13044 entered the red giant phase, and that the engulfing of inner planets caused irregularities that shifted HIP 13044 b's orbit; another model suggests that an asymmetrical distribution of mass in the star caused the same effect. At the time of its discovery, HIP 13044 b was found to orbit the most metal-poor star discovered to date.