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 gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speak ...

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 origins of the e ...

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 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, 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 most northerly of the five major circles of latitude as shown on maps of Earth. Its southern equivalent is the Antarctic Circle. The Arctic Circle marks the southernmost latitude at w ...

. Its magnitude of 4.5 means that naked-eye visibility is dependent on a sky sufficiently free from the effects of light pollution. 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 is a system of two star, stars that are gravity, 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 using a telescope as separa ...

with an orbital period of 22.35 years and an eccentricity 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 grati ...

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

photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...

. It is a variable star 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