Iota Herculis
Encyclopedia
Iota Herculis (ι Her, ι Herculis) is a fourth-magnitude star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
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....
Hercules
Hercules (constellation)
Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today...
. The luminary shares an etymological similarity with the star Rigel
Rigel
Rigel is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18...
in the constellation of Orion
Orion (constellation)
Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...
, as both stars refer to one of the feet of each mythological hero.
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
, , meaning Celestial Flail
Purple Forbidden enclosure
The Purple Forbidden enclosure is one of the San Yuan or Three enclosures. Stars and constellations of this group lie near the north celestial pole and visible all year from temperate latitudes in the Northern Hemisphere.-Asterisms:The asterisms are :...
, refers to an asterism consisting of ι Herculis, ξ Draconis
Xi Draconis
Xi Draconis is a star in the constellation Draco. It has the traditional name Grumium or Genam.This star, along with β Dra , γ Dra , μ Dra and ν Dra were Al ʽAwāïd, "the Mother Camels", which was later known as the Quinque Dromedarii.In Chinese, , meaning Celestial Flail, refers to an asterism...
, ν Draconis
Nu Draconis
Nu Draconis is a double star in the constellation Draco. The respective components are designated ν1 Draconis and ν2 Draconis...
, β Draconis
Beta Draconis
Beta Draconis is the third brightest star in the constellation of Draco. It has the traditional name Rastaban, which has also been used for Gamma Draconis....
and γ Draconis. Consequently, ι Herculis itself is known as
Properties
Iota Herculis is a B-type subgiant starSubgiant star
A subgiant star is a star that is slightly brighter than a normal main-sequence star of the same spectral class, but not as bright as true giant stars...
that is at the end of its hydrogen fusion stage. With a stellar classification
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
B3IV, it is considerably larger 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...
, having a mass that is 6.5 times solar and a radius 5.3 times. Though its apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
is only 3.79, it is 2,500 times more luminous than the Sun, yielding an absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
of -2.11, brighter in fact than the most of the hot B stars in the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...
open star cluster
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
. The Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
mission estimated its distance at roughly 152 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s (pc) from 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...
, or 496 light years (ly) away; an updated parallax measurement from Floor van Leeuwen in 2007, however, puts the distance at 455ly with a much tighter error factor of only 8ly.
Star system
Iota Herculis is a multiple starMultiple star
A multiple star consists of three or more stars which appear from the Earth to be close to one another in the sky. This may result from the stars being physically close and gravitationally bound to each other, in which case it is physical, or this closeness may be merely apparent, in which case...
system. It is a spectroscopic binary having a 113.8 day period, indicating that its closest component is separated by about 1 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. Another companion can be found at approximately 30 AU from the main star, giving it an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of about 60 years. Still another star has been identified orbiting the main star with an angular separation of 116 arcseconds and a visual magnitude of 12.1. This would place it approximately 18,000 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
away, giving it an orbit of about 1 million years.
See also
- Lists of stars in the constellation Hercules
- Class B Stars
- Multiple starMultiple starA multiple star consists of three or more stars which appear from the Earth to be close to one another in the sky. This may result from the stars being physically close and gravitationally bound to each other, in which case it is physical, or this closeness may be merely apparent, in which case...
- Variable starVariable starA star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
External links
- Jim Kaler's Stars, University of Illinois: IOTA HER (Iota Herculis)
- An Atlas of the Universe: Multiple Star Orbits