Iota Horologii b
Encyclopedia
Iota Horologii b (ι Hor b / ι Horologii b), often catalogued HR 810 b, is an extrasolar planet
approximately 50 light-year
s 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 mass
es and would therefore be a brown dwarf
.
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. Iota Horologii b was the first planet found by a team of planet hunters led by Martin Kürster in the summer of 1998.
The measurements of Iota Horologii
show that the planet orbits the star approximately every 320 day
s. 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.
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.
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.
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
approximately 50 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Horologium
Horologium
Horologium is a small and faint constellation in the southern sky . Its name is Latin for clock. It was created in the 18th century by Abbé Nicolas Louis de Lacaille, who originally named it Horologium Oscillitorium after the pendulum clock to honour its inventor, Christiaan Huygens...
(the Pendulum Clock
Pendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...
). Iota Horologii b has a minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
1.94 times that of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, however preliminary astrometric measurements
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
suggest that the object may be around 24 Jupiter mass
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....
es and would therefore be a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
.
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 ObservatoryEuropean Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
instrument, with the data found at the La Silla Observatory
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory organisation, and several others are partly maintained by ESO...
in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
.
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. Iota Horologii b was the first planet found by a team of planet hunters led by Martin Kürster in the summer of 1998.
The measurements of Iota Horologii
Iota Horologii
Iota Horologii is a solar twin, yellow dwarf star approximately 56 light-years away in the constellation of Horologium . The star is classified as a G0Vp yellow dwarf...
show that the planet orbits the star approximately every 320 day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
s. 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
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
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
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
, this orbit would stretch from just outside the orbit of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
(at 117 million km or 0.78 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
[AU] from the Sun) to just outside the orbit of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
(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
Iota Horologii
Iota Horologii is a solar twin, yellow dwarf star approximately 56 light-years away in the constellation of Horologium . The star is classified as a G0Vp yellow dwarf...
is younger than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, the announcement of a protoplanetary disk
Protoplanetary disk
A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star...
caused speculation of this system still being active in debris bombardment.
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
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
and a substellar companion of Iota Horologii
Iota Horologii
Iota Horologii is a solar twin, yellow dwarf star approximately 56 light-years away in the constellation of Horologium . The star is classified as a G0Vp yellow dwarf...
. However these measurements were later proved useful only for upper limits of inclination.