Libra (constellation)
Libra constellation |
|
---|---|
Latin name | Libra |
Latin genitive | Librae |
Abbreviation | Lib |
Right ascension | 14 h 21 m 38 s to 16 h 02 m 17 s |
declination | −29 ° 59 ′ 42 ″ to −0 ° 28 ′ 27 ″ |
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 .
description
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
Stars
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
- http://www.astronomie.de/bibliothek/artikel/sternbilder/waage.htm (star map)
- Libra constellation A photographic journey through the signs of the zodiac
- http://deepsky.astroinfo.org/Sco/m4/ (pictures of Scorpio and Libra)
- https://exoplanetarchive.ipac.caltech.edu/ (data of the exoplanets)