Iota¹ Librae, Latinized from ι¹ Librae, is a quadruple

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Libra Libra generally refers to: * Libra (constellation), a constellation * Libra (astrology), an astrological sign based on the star constellation Libra may also refer to: Arts and entertainment * ''Libra'' (novel), a 1988 novel by Don DeLillo Musi ...

. Its

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

is 4.54. It is located 379 light years from earth.Extended Hipparcos Compilation (XHIP) (+ Anderson, 2012)
/ref>

Visibility

Due to its southern location, although the star can be seen from most regions of the earth, observers in the southern hemisphere are more advantaged. Near

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

, it appears circumpolar, while it always remains invisible only in the vicinity of the

Arctic Circle The Arctic Circle is one of the two polar circles, and the northernmost of the five major circle of latitude, circles of latitude as shown on maps of Earth at about 66° 34' N. Its southern counterpart is the Antarctic Circle. The Arctic Circl ...

. Its magnitude of 4.5 means that naked-eye visibility is dependent on a sky sufficiently free from the effects of

light pollution Light pollution is the presence of any unwanted, inappropriate, or excessive artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting sources, during the ...

. The best time for observation in the evening sky falls in the months between May and September; from both hemispheres of the period of visibility remains approximately the same, thanks to the position of the star not far from the celestial equator.

Physical

Iota¹ Librae is a four star system. The inner pair, designated components Aa and Ab, form a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

with an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 22.35 years and an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.35. The brighter member has a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...

of , indicating it is a B-type subgiant star with an overabundance of

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

in the

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

. It is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

of the Alpha2 Canum Venaticorum type with a magnitude that varies from 4.53 to 4.56, while its spectrum likewise shows variability.General Catalogue of Variable Stars (Samus + 2007-2012)
/ref> The secondary component is of class B9. The two stars are very close together (0.2 arcsec away), respectively of magnitude 5.1 and 5.5. A third component is located 57 arcsec distant; it is a star of the tenth magnitude, Iota¹ Librae B. The third component is also a double star, of equal magnitudes, 1.9 arcseconds apart.Burnam's Celestial Handbook, pp. 1107-1108. Due to its position on the ecliptic, it is sometimes obscured by the Moon or planets. A lunar occultation took place April 4, 2012.

References

External links

Simbad archive
{{DEFAULTSORT:Iota1 Librae Libra (constellation) B-type subgiants Librae, Iota1 Alpha2 Canum Venaticorum variables 4 Librae, 24 Durchmusterung objects 074392 134759 5652