Iota Horologii b

Planetbox begin
name = Iota Horologii b Planetbox image

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caption = An artist's impression of Iota Horologii b with a
fictional, Venus-like moon in orbit around the planet.Planetbox star
star = Iota Horologii
constell = Horologium
RA = RA|02|42|31.65
DEC = DEC|-50|48|12.29
dist_ly = 50.6
dist_pc = 16.8
class = G0VpPlanetbox orbit
semimajor = 0.91
eccentricity = 0.22 ± 0.06
period = 311.3 ± 1.3
ang_dist = 58.71
long_peri = 78.9 ± 13.1
t_peri = 2,451,308.8 ± 10.4
semi-amp = 57.1 ± 5.2 Planetbox character
mass = >2.24 ± 0.13Planetbox discovery
discovery_date = 29 July 1998
discoverers = Kürster et al.
discovery_method = Doppler spectroscopy
discovery_site = flagicon|Chile La Silla
discovery_status = Published Planetbox catalog
names = Iota Horologii b, HD 17051 b, HR 810 b

Iota Horologii b (ι Hor b / ι Horologii b), often cataloged 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 jovial planets that has insolations similar to that of Venus.

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 an 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." [cite journal |url= http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A%26A...353L..33K&db_key=AST&high=3b4b5e274006575 |author=Kürster et al.|title=An extrasolar giant planet in an Earth-like orbit. Precise radial velocities of the young star iota Horologii = HR 810|journal=Astronomy and Astrophysics|volume=353|year=2000|pages=L33 – L36] Iota Horologii b was the first planet found by a team of planet hunters lead by Martin Kürster in the summer of 1998. [cite journal | url=http://www.edpsciences.org/papers/aa/full/2001/31/aa10239/aa10239.html |author=Naef et al.|title=The CORALIE survey for southern extrasolar planets V. 3 new extrasolar planets |journal = Astronomy and Astrophysics | volume=375 | year=2001 | pages=205–218 ]

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 planet to be found orbiting within its parent star's habitable zone. But having an eccentric and closer orbit than the Earth, Iota Horologii b is though to have an insolation similar to Venus.

Though no natural satellites were discovered around any extrasolar planet, the possibility of a moon around Iota Horologii b seems likely. The maximum stable prograde (or stability of a moon) around Iota Horologii b is calculated at be at approximately 4,120,000 kilometers (or 0.027 astronomical unit) away from the planetary center. 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. 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)

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. [http://www.eso.org/public/outreach/press-rel/pr-2000/phot-27-00.html]

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; [cite journal|url=http://adsabs.harvard.edu/abs/2001A%26A...372..935P|title=Screening the Hipparcos-based astrometric orbits of sub-stellar objects|author=Pourbaix, D. and Arenou, F.|journal=Astronomy and Astrophysics|volume=372|pages=935 – 944|year=2001|doi=10.1051/0004-6361:20010597] 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

* Gamma Cephei Ab
* Gliese 570 Ab
* HD 28185 b
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* Iota Horologii in fiction

References

External links

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