Iota Horologii b

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Iota Horologii b
Exoplanet List of exoplanets
Parent star
Star Iota Horologii
Constellation Horologium
Right ascension (α) 02h 42m 33.466s[1]
Declination (δ) −50° 48′ 01.06″[1]
Apparent magnitude (mV) 5.4
Distance 56.0 ± 0.2[1] ly
(17.17 ± 0.06[1] pc)
Spectral type G0Vp
Orbital elements
Semi-major axis (a) 0.91 AU
(136 Gm)
Periastron (q) 0.71 AU
(106 Gm)
Apastron (Q) 1.11 AU
(166 Gm)
Eccentricity (e) 0.22 ± 0.06
Orbital period (P) 311.3 ± 1.3 d
(0.8523 y)
Argument of
(ω) 78.9 ± 13.1°
Time of periastron (T0) 2,451,308.8 ± 10.4 JD
Semi-amplitude (K) 57.1 ± 5.2 m/s
Physical characteristics
Minimum mass (m sin i) 2.24 ± 0.13 MJ
Discovery information
Discovery date 29 July 1999[2]
Discoverer(s) Kürster et al.
Discovery method Doppler spectroscopy
Discovery site La Silla Observatory
Discovery status Published[3][4]
Other designations
HD 17051 b, HR 810 b
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

Iota Horologii b (ι Hor b / ι Horologii b), often catalogued HR 810 b, is an extrasolar planet approximately 56 light-years away in the constellation of Horologium (the Pendulum Clock). Iota Horologii b has a minimum mass 1.94 times that of Jupiter, however preliminary astrometric measurements suggest that the object may be around 24 Jupiter masses and would therefore be a brown dwarf.

Detection and discovery[edit]

The discovery of Iota Horologii b was the result of a long-term survey of forty Solar analog stars that was begun in November 1992. The planet represents the first discovery of an extrasolar planet with a European Southern Observatory instrument, with the data found at the La Silla Observatory in Chile.

The Keplerian signal found the planet to have an orbital period of 320.1 days, indicative of an orbiting planet with minimum mass of 2.26 Jupiter masses.[3] Iota Horologii b was announced in the summer of 1999 as the first planet found by a team of planet hunters led by Martin Kürster.[2]

The measurements of Iota Horologii show that the planet orbits the star approximately every 320 days. From this period, the known mass of the central star (1.03 solar masses) and the amplitude of the velocity changes, a mass of at least 2.26 times that of planet Jupiter is deduced for the planet.

It revolves around the host star in a somewhat elongated orbit. If it were located in the Solar System, this orbit would stretch from just outside the orbit of Venus (at 117 million km or 0.78 astronomical unit [AU] from the Sun) to just outside the orbit of the Earth (at 162 million km or 1.08 AU). Because the planet is at least 720 times more massive than the Earth, it is predicted that Iota Horologii b is more similar to planet Jupiter.

Because Iota Horologii is younger than the Sun, the announcement latter retracted of a protoplanetary disk caused speculation of this system still being active in debris bombardment.[5]

In recent astrometric analysis of Iota Horologii b suggests that planet b may have as much as 24 times the mass of Jupiter with an inclination of 5.5 degrees from Earth's line of sight. With this calculations, Iota Horologii b may actually be an extremely dim brown dwarf and a substellar companion of Iota Horologii. However these measurements were later proved useful only for upper limits of inclination.[6]

See also[edit]


  1. ^ a b c d van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b "Extrasolar Giant Planet in Earth-like Orbit" (Press release). Garching, Germany: European Southern Observatory. July 29, 1999. Retrieved December 29, 2012. 
  3. ^ a b Kürster, M.; et al. (2000). "An extrasolar giant planet in an Earth-like orbit. Precise radial velocities of the young star iota Horologii = HR 810". Astronomy and Astrophysics. 353 (3): L33–L36. Bibcode:2000A&A...353L..33K. 
  4. ^ Naef, D.; et al. (2001). "The CORALIE survey for southern extrasolar planets V. 3 new extrasolar planets". Astronomy and Astrophysics. 375 (1): 205–218. arXiv:astro-ph/0106255Freely accessible. Bibcode:2001A&A...375..205N. doi:10.1051/0004-6361:20010841. 
  5. ^ "Retracted in August 2001: ADONIS Discovers Dust Disk around a Star with a Planet". European Southern Observatory. 2000-10-13. Retrieved 2011-12-21. 
  6. ^ Pourbaix, D.; Arenou, F. (2001). "Screening the Hipparcos-based astrometric orbits of sub-stellar objects". Astronomy and Astrophysics. 372 (3): 935–944. arXiv:astro-ph/0104412Freely accessible. Bibcode:2001A&A...372..935P. doi:10.1051/0004-6361:20010597. 

External links[edit]

Coordinates: Sky map 02h 42m 31.65s, −50° 48′ 12.29″