Libra (constellation)

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Libra constellation
Libra constellation map.png
Latin name Libra
Latin genitive Librae
Abbreviation Lib
Right ascension 14213814 h 21 m 38 s to  16 h 02 m 17 s160217
declination 1704058−29 ° 59 ′ 42 ″ to  −0 ° 28 ′ 27 ″1997173
surface 538.052 deg²
rank 29
Completely visible 60.3 ° N to 90 ° S
Observation time for Central Europe January - (March) -
(May) - July
Number of stars brighter than 3 mag 2
Brightest star (size) Zuben-el-Shemali (2.61)
Meteor streams
Neighboring constellations
clockwise from north )
swell IAU ,

The Libra ( Latin Libra , astronomical signs ♎) is a constellation of the ecliptic .


The constellation Libra as seen with the naked eye

Libra is a constellation between Scorpio (Scorpius) and Virgo (Virgo). Two of its stars are brighter than the 3rd magnitude .

The scales lie on the ecliptic so that the sun , moon and the planets pass through them. It therefore belongs to the signs of the zodiac . However, due to the precession movement of the earth's axis, the time of the passage of the sun has changed compared to ancient times , which is why the zodiac sign Libra no longer corresponds to the constellation Libra. The sun is currently in Libra from October 31 to November 23.

History and mythology

Libra is one of the classic 48 constellations of antiquity described by Claudius Ptolemy .

Already with the Sumerians the constellation was called "Libra" ( Giš-rin ), perhaps because the sun was there 4000 years ago at the time of the equinox , but perhaps also because taxes were collected at this time of the year. The tax collectors weighed the amount of grain due with beam scales.

With the Babylonians and ancient Greeks , on the other hand, the stars were assigned to the scorpion and represented its claws. Therefore the constellation was called "Chelai" (the claws) by the Greeks.

The Arab astronomers also saw part of Scorpio in the constellation. The stars β and γ formed the northern scissors, the stars α, υ and σ the southern scissors of the Scorpio.

The current name Libra was introduced by the Romans around 100 AD . For them, the constellation represented the symbol of justice .

The “southern scissors” was not assigned to Libra until 1930 when the constellation boundaries were established by the International Astronomical Union (IAU). The star σ Librae was previously called γ Scorpii.

Celestial objects


B. F. Names or other designations size Lj Spectral class
β 27 Zuben-el-schemali (Zubeneschemali) 2.61 m 120 B8 V
α 2 9 Zuben-el-dschenubi (Zubenelgenubi) 2.75 m 77 A3
σ 20th Brachium , Cornu 3.29 m 292 M3 III
υ 3.60 m
θ 39 3.6 m 120 K4 III
τ 40 3.66 m 400 B3 V
γ 38 Zuben-el-Akrab 3.91 m 152 G8 IV
16 4.47 m
ι 4.54 m
37 4.61 m
κ 4.71 m
δ 13 Zuben-el-meticulousness 4.4 to 5.8 m 304 B9.5 V
ε 4.92 m
11 4.93 m
48 4.95 m
42 4.97 m
λ 5.04 m
36 5.13 m
α 1 5.13 m
ν 21st 5.19 m
12 5.27 m
μ 7th 5.32 m 250 A1 + A5
41 5.36 m
η 5.41 m
49 5.47 m
ξ 2 5.48 m
ζ 5.53 m
50 5.53 m
32 5.64 m
4th 5.70 m
ξ 1 5.78 m
34 5.82 m
18th 5.88 m
47 5.95 m

β Librae is a bluish shining star of the spectral class B8 V, 120 light years away . The name Zuben-el-Schemali comes from the Arabic and means "northern scissors" (of the scorpion).

The σ Librae ( Brachium ), 292 light years away, is a reddish star of the spectral class M4 III.

γ Librae is 152 light years away. The Arabic name Zuben-el-Akrab means "scorpion's scissors".

Double stars

object Sizes distance
α 2.8 / 5.2 m 231 "
ι 4.7 / 9.7 m 8.5 "
μ 5.7 m / 6.6 m 2.0 "

α Librae is a binary star system 77 light years away. Due to the wide angular distance of 231 arc seconds , they can already be observed with prism binoculars . The system is almost exactly on the ecliptic, so it is regularly the moon covered .

The Arabic name Zuben-el-dschenubi means "southern scissors".

The binary star system ι Librae is about 250 light years away. A telescope with an opening of 6 cm or more is required for observation .

Variable stars

star size period Type
δ 4.9 to 5.9 m 2,327 days Coverage variable

δ Librae is an eclipse- variable star of the Algol type, 304 light-years away . Its brightness changes regularly with a period of 2.327 days.

Messier and NGC objects

Messier (M) NGC other size Type Surname
5897 8.6 m Globular clusters

In Libra is the globular cluster NGC 5897, 45,000 light years away .

Further individual objects

Worth mentioning among the stars in Libra is u. a. Gliese 581 , a red dwarf 20.5 light years away , which is about 50 times weaker than our sun ( spectral class : M3.5, visual brightness: 10.56). It has a system of at least three planetary companions ( exoplanets ).

See also

Web links

Commons : Libra constellation  - collection of images, videos and audio files