 Saturn-like rings and a sulfur stained atmosphere. | ||
| Parent star | ||
|---|---|---|
| Star | Iota Horologii | |
| Constellation | Horologium | |
| Right ascension | (α) | 02h 42m 31.65s |
| Declination | (δ) | -50° 48′ 12.29″ |
| Apparent magnitude | (mV) | 5.4 |
| Distance | 50.6 ly (16.8 pc) | |
| Spectral type | G0Vp | |
| Orbital elements | ||
| Semimajor axis | (a) | 0.91 AU |
| Eccentricity | (e) | 0.22 ± 0.06 |
| Orbital period | (P) | 311.3 ± 1.3 d |
| Argument of periastron | (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 1998 | |
| Discoverer(s) | Kürster et al. | |
| Detection method | Doppler spectroscopy | |
| Discovery site |  La Silla Observatory | |
| Discovery status | Published | |
| Other designations | ||
| Database references | ||
| Extrasolar Planets Encyclopaedia | data | |
| SIMBAD | data | |
Iota Horologii b (ι Hor b / ι Horologii b), often catalogued HR 810 b, is an extrasolar planet approximately 50 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. Iota Horologii b was the first extrasolar planet discovered to be orbiting in the habitable zone of its parent star, and is a prototype of jovian planets that has insolations similar to that of Venus.[citation needed]
Detection and discovery
The discovery of Iota Horologii b was the result of a long-term survey of forty solar twin 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. "With an eccentricity of 0.161 and a semi-major axis of 0.925 AU, this object moves in the most Earth-like orbit found so far among extrasolar planets."[1] Iota Horologii b was the first planet found by a team of planet hunters lead by Martin Kürster in the summer of 1998.[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 our own 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.
Physical characteristics
Iota Horologii b was the first confirmed extrasolar planet to be found orbiting within its parent star's habitable zone. But calculated from the planet's orbital distance, it is estimated that the planet orbits in the inner reaches of the zone. Because of this, it is plausible that the planet would have an insolation similar to Venus.[3]
Because of the planet's mass and distance, it is concluded that Iota Horologii b would likely contain a moon system. Based on the planet's its minimum mass, it is estimated that the stable prograde (or stability of a moon) around Iota Horologii b is approximately 4,120,000 kilometers (or 0.027 astronomical unit) away from the planetary center.[3] The maximum mass of a moon keeping a stable orbit around the planet would be approximately 10 times Earth mass (with a speculated radius of 1.026 Jupiter radii).[3] The calculated albedo of the planet is estimated at 0.79, while the gravitational influence (Hill sphere) is estimated at 11,470,000 km (0.076 AU).[3] However, these calculations are only estimates based on the planet's minimum mass. Because Iota Horologii is younger than the Sun, the announcement of a protoplanetary disk caused speculation of this system still being active in debris bombardment.[4]
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;[5] worthless for HD 192263 b, and for 55 Cancri c and upsilon Andromedae d they contradicted measured inclinations of other planets in their systems.
See also
References
- ^ Kürster 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: L33 – L36. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A%26A...353L..33K&db_key=AST&high=3b4b5e274006575.
- ^ Naef et al. (2001). "The CORALIE survey for southern extrasolar planets V. 3 new extrasolar planets". Astronomy and Astrophysics 375: 205–218. http://www.edpsciences.org/papers/aa/full/2001/31/aa10239/aa10239.html.
- ^ a b c d "Iota Horologii b". Extrasolar Visions. http://www.extrasolar.net/planettour.asp?PlanetID=32. Retrieved on 2008-06-12.
- ^ "ADONIS Discovers Dust Disk around a Star with a Planet". European Southern Observatory. 2000-10-13. http://www.eso.org/public/outreach/press-rel/pr-2000/phot-27-00.html. Retrieved on 2008-12-17.
- ^ Pourbaix, D. and Arenou, F. (2001). "Screening the Hipparcos-based astrometric orbits of sub-stellar objects". Astronomy and Astrophysics 372: 935 – 944. doi:. http://adsabs.harvard.edu/abs/2001A%26A...372..935P.
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