| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Horologium |
| Right ascension | 02h 42m 33.46667s[1] |
| Declination | −50° 48′ 01.0551″[1] |
| Apparent magnitude (V) | +5.40[2] |
| Characteristics | |
| Spectral type | G0Vp[3] |
| B−Vcolor index | 0.57[2] |
| Variable type | none |
| Astrometry | |
| Radial velocity (Rv) | 16.94±0.12[1] km/s |
| Proper motion (μ) | RA: 333.716(35)[1]mas/yr Dec.: 219.423(42)[1]mas/yr |
| Parallax (π) | 57.6131±0.0383 mas[1] |
| Distance | 56.61 ± 0.04 ly (17.36 ± 0.01 pc) |
| Absolute magnitude (MV) | +4.23[4] |
| Details | |
| Mass | 1.25 ± 0.01[5] M☉ |
| Radius | 1.16 ± 0.04[6] R☉ |
| Luminosity | 1.64 ± 0.05[6] L☉ |
| Temperature | 6,080[6] K |
| Metallicity [Fe/H] | 0.14–0.19[5] dex |
| Rotation | 7.70+0.18 −0.67 d[7] |
| Rotational velocity (v sin i) | 6.0±0.5[7] km/s |
| Age | 0.625[5] Gyr |
| Other designations | |
| ι Hor,GJ 108,HD 17051,HIP 12653,HR 810,2MASS J02423346-5048008[2] | |
| Database references | |
| SIMBAD | data |
Iota Horologii,Latinized from ι Horologii, is a yellow-huedstar approximately 56.5light-years away in theHorologiumconstellation. The star is classified as a G0Vp[3]yellow dwarf (it has previously been classified as G3 and asubgiant [IV]). It has a mass and radius larger than theSun, and is about 50% more luminous.
In 1999, a planet of the star was discovered.[8] Because the planet orbits in a nearEarth orbit, Iota Horologii was ranked 69th in the list of candidates forNASA's plannedTerrestrial Planet Finder mission. In 2000, adust disc was announced around the star, but this was later determined to be an instrumental artifact.[9]
Since Iota Horologii is in the minor constellation ofHorologium and is quite dim in the sky, it has not been given a traditional name. It lies roughly between the starsEta Horologii andR Horologii (though it is not close to them in real space).
In its current position, Iota Horologii is closest to the starChi Eridani (ayellow subgiant), approximately 7 light-years away. The closestplanetary systems to Iota Horologii areHD 10647 (ayellow dwarf), approximately 57 light-years away, andEpsilon Reticuli (an orange subgiant), approximately 59 light-years away. Otherstar systems close to Iota Horologii includeNu Phoenicis andZeta Reticuli.[3]
Spectrographic analysis indicates the star must have formed together with the stars of theHyades cluster (~625 million years ago) but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. Themetallicity 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.[5]
Measurements of magnetic activity with the 1.5 m telescope atCerro Tololo Inter-American Observatory show that the star has a 1.6 yearmagnetic activity cycle which, as of 2010, is the shortest cycle measured so far for a solar like star. The sun by comparison has an 11-yearmagnetic activity cycle. There may be a second, longer cycle which modulates the 1.6 year cycle.[10]
Iota Horologii b is believed to be Jupiter-sized.[8] The planet's discovery was the result of a survey of forty stars that began in November 1992.[11]
Stability analysis reveals that the orbits of Earth-sized planets located in the planet'strojan points would be stable for long periods of time.[12]
Based on residuals in the radial velocity curve, a planet in aneccentric 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.[11]
Anastrometric measurement of the planet's inclination and true mass was published in 2022 as part ofGaia DR3.[13]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 6.2±0.5 MJ | 0.96 ± 0.05 | 307.2 ± 0.3 | 0.18 ± 0.03 | 87±6° | — |
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