Iota Horologii b

Iota Horologii b (ι Hor b / ι Horologii b) is an extrasolar planet orbiting the star Iota Horologii every 311 days. 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. The discovery is the result of a long-term survey of forty solar-type stars that was begun in November 1992.

Iota Horologii b was the first extrasolar planet found to have insolation similar to Venus.

Discovery

The discovery is the result of a long-term survey of forty solar-type stars that was begun in November 1992. It is based on highly accurate measurements of stellar radial velocities.

The team that found the new planet, now designated Iota Horologii b , consists of Martin Kürster, Michael Endl and Artie P. Hatzes.

Iota Horrologii b represents the first discovery of an extrasolar planet with an European Southern Observatory (ESO) instrument.

Radial velocity

For the star Iota Horologii , a measurement precision of about ± 17 m/s (± 61 km/h) was achieved. Iota Horologii b has an orbital period of 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.

File:Phot-32b-99.jpg

radial velocity of Iota Horologii b.

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 AU from the Sun) to just outside the orbit of the Earth (the point farthest from the Sun, at 162 million km or 1.08 AU)

Iota Horologii b is, however, at least 720 times more massive than the Earth and it is probably more similar to planet Jupiter in our own solar system. While the radial velocity technique described above only determines a minimum value for the planet's mass, an analysis of the velocity with which the star turns around its own axis suggests that the true mass of Iota Horologii b is unlikely to be much higher.

Characteristics and Speculations

File:IotaHorologii-orbit.jpg

Iota Horologii b's orbit (white) compared to Earth's orbit (green).

Iota Horologii b orbits a very Sun-like star, with a spectral type of G0.

Iota Horologii b was the first planet to be found orbiting in the habitable zone of its star, but as it is near the inner edge of that zone it is likely to be hotter than Earth. The first planet discovered near the center of its sun's habitable zone was HD 28185 b.

File:Sulfurjovian.jpg

Iota Horologii b is the best example of a "sulfur giant."

Iota Horologii b is the best example of a "sulfur giant" (rarly called Horologid planets). The upper layers of Iota Horologii b's atmosphere probably have a temperature similar to that of Venus. Because of this, Iota Horologii b might be yellowish-green in color, with an atmoshere of Hydrogen, Helium, Water and Sulfuric acid. Other examples of sulfur giants are Gamma Cephei Ab, 94 Ceti b, 23 Librae b and HD 82943 c.

With a possible dust disc around Iota Horologii, the possiblility of impacts on Iota Horologii is likely. Iota Horologii b is estimated to be slightly larger than Jupiter, at 1.026 times Jupiter's radius. Its albedo is estimated at 0.79. The Gravitational Influence (Hill Sphere) is estimated at 11,470,000 km (0.076 AU)

If Iota Horologii b has a natural satellite system (i.e. moons), maximum stable prograde moon orbit would be 4,120,000 km (0.027 AU). The maximum moon mass would be 10 times Earths's mass.

Work in Fiction

• In the science fiction novel Iota Cycle by Russell Lutz, Iota Horologii serves as a setting for colonization and terraforming. In the novel, Iota Horologii has six planets (Iota Horologii b being the second planet). The planets are referred to by a nickname after a continent. In order from closest to the star: Australia, Asia, Europe, Africa, America, and Antarctica (Asia being Iota Horologii b).

See also

• Gamma Cephei Ab
• HD 28185 b

External links

• "Iota Horologii b". Extrasolar Visions. Retrieved June 21. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• "Discovery of Iota Horologii b". European Southern Observatory. Retrieved June 12. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• "Iota Horologii". SolStation. Retrieved June 12. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• "Iota Horologii". планетные системы (in Russian). Retrieved June 21. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)