Iota Horologii,
Latinized from ι Horologii, is a yellow-hued
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
approximately 56.5
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away in the
Horologium constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
. The star is classified as a G0Vp
(it has previously been classified as G3 and a
subgiant
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...
V. It has a mass and radius larger than the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
, and is about 50% more luminous.
In 1999, a planet of the star was discovered.
Because the planet orbits in a near
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
orbit, Iota Horologii was ranked 69th in the list of candidates for
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
's planned
Terrestrial Planet Finder
The Terrestrial Planet Finder (TPF) was a proposed project by NASA to construct a system of space telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled in 2011. There were two telescope ...
mission. In 2000, a
dust disc was announced around the star, but this was later determined to be an instrumental artifact.
Distance and visibility
Since Iota Horologii is in the minor constellation of
Horologium and is quite dim in the sky, it has not been given a traditional name. It lies roughly between the stars
Eta Horologii and
R Horologii
R Horologii is a red giant star approximately 1,000 light-years away in the southern constellation of Horologium. It is a Mira variable with a period of 404.83 days, ranging from apparent magnitude
Apparent magnitude () is a me ...
(though it is not close to them in real space).
In its current position, Iota Horologii is closest to the star
Chi Eridani
χ Eridani (Latinised as Chi Eridani) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.70. The distance to this system, as determined using the parallax method ...
(a
yellow subgiant), approximately 7 light-years away. The closest
planetary system
A planetary system is a set of gravitationally
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interacti ...
s to Iota Horologii are
HD 10647
HD 10647 (q1 Eridani) is a 6th-apparent magnitude, magnitude yellow-white dwarf star, 57 light-years away in the constellation of Eridanus (constellation), Eridanus. The star is visible to the unaided eye under very dark skies. ...
(a
yellow dwarf), approximately 57 light-years away, and
Epsilon Reticuli
Epsilon Reticuli, Latinized from ε Reticuli, is a double star approximately 59 light-years away in the constellation of Reticulum. The primary component is an orange subgiant, while the secondary is a white dwarf. The two sta ...
(an orange subgiant), approximately 59 light-years away. Other
star system
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speak ...
s close to Iota Horologii include
Nu Phoenicis
Nu Phoenicis is a F-type main-sequence star in the southern constellation of Phoenix. It is visible to the naked eye with an apparent visual magnitude of 4.95. This is a solar analogue, meaning its observed properties appear similar to t ...
and
Zeta Reticuli.
Properties
Spectrograph
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...
ic analysis indicates the star must have formed together with the stars of the
Hyades cluster (~625 million years ago) but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. The
metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
of the star matches the abundances found in the Hyades, indicating that the metals (elements heavier than helium) in the atmosphere were not acquired because it engulfed planetary material.
Measurements of magnetic activity with the 1.5 m telescope at
Cerro Tololo Inter-American Observatory
The Cerro Tololo Inter-American Observatory (CTIO) is an astronomical observatory located on Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Cerro Pachón about to the southeast. It is approximately ...
show that the star has a 1.6 year
magnetic activity
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magn ...
cycle which, as of 2010, is the shortest cycle measured so far for a solar like star. The sun by comparison has an 11-year
magnetic activity cycle. There may be a second, longer cycle which modulates the 1.6 year cycle.
Planetary system
''Iota Horologii b'' is believed to be Jupiter-sized.
The planet's discovery was the result of a survey of forty stars that began in November 1992.
Stability analysis reveals that the orbits of Earth-sized planets located in the planet's
trojan points would be stable for long periods of time.
Based on residuals in the radial velocity curve, a planet in an
eccentric
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-center, in geometry
* Eccentricity (graph theory) of a v ...
orbit with a period of approximately 600 days was proposed, but this was not confirmed and it seems likely that the effect was due to activity on Iota Horologii itself.
An
astrometric
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way.
Histor ...
measurement of the planet's inclination and true mass was published in 2022 as part of
Gaia DR3
The ''Gaia'' catalogues are star catalogues created using the results obtained by '' Gaia'' space telescope.
The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, espec ...
.
See also
*
Gliese 570
References
External links
*
*
*
*
{{DEFAULTSORT:Iota Horologii
Horologii, Iota
CD-51 00641
017051
012653
0810
0108
Horologium (constellation)
Planetary systems with one confirmed planet
G-type main-sequence stars
Hyades (star cluster)