Picture from: http://www.astronoo.com/es/constelaciones-zodiaco.html
LIBRA : The origin name came from Latin (Lib) In a scale from 1 to 6, the number one to
represent the biggest stars you can see and six to be the dimmest that a human eye can possible
see. The overall visual view comparable to the naked eye would be a magnitude of six which
makes this constellation the 29th in size taking an area of 538 square degrees. Libra can be
located at latitudes of +65 degrees and -90 degrees. The best observation is “During bright
northern spring nights it lies east of Virgo and west of Scorpius”1
From the twelve original zodiacal constellations that are Aries, Taurus, Gemini, Cancer, Leo,
Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius and Pisces. Libra is the only
constellation that is an object. All other constellations are represented by a living thing that
could be an animal or someone from mythology.
Several Middle Eastern cultures saw Libra as a symbol for equality and justice. To the Greek
Astraea was the last God to stay on earth, she rose to heaven to become the constellation Virgo
and she carried the Scales of Balance of justice which is known by the constellation of Libra. In
ancient history the area where Libra is located in space was known by the Geek as the claws of
the scorpion, basically Libra was the claws of the constellation of Scorpius. “The Greek called
this area Chelae (Χηλαί), literally meaning claws” 2 Greek astronomer Ptolemy was the first to
catalogued the constellation in 150 A.D. Libra does not contain any first magnitude stars.
Before Greek times, about a thousand years before Christ the Babylonians referred Libra as the
balance of heavens; then the Romans revived this constellation as a balance. To the Romans
Libra was shown as a scale of balance that was held by Farnes Atlas, a Roman Character from
mythology. They visualized the constellation as a balance because the sun lay there at the
autumn equinox, when the hours of daylight and night are equal.
For the Chinese, the square part of Libra was named Di, which meaning in Chinese is root. The
name was given because Libra was visible in early October. In October when the ground dried
up you can see the roots on the ground. It was also imagined as the hand or the chest of the blue
dragon
To shape the balance Alpha Librae the second brightest star in Libra and Beta Librae the
brightest star in the constellation are the scales of the balance and Gamma and Sigma Librae are
the weighing pans.
With a seeming visual size of 2.6 Libra’s brightest stars, Beta Librae and second brightest Alpha
Librae with a visual magnitude of 5.15 official names are Zubenelgenubi which in Arabic means
“The southern claw” and Beta Librae Zubeneschamali the Northern Claw”2 As to remind us
that Libra was once part of Scorpius.
Beta Librae “In the stellar classification of B8 V, which means that it is a blue-white dwarf is
classified as a single star, but it shows small periodic variations in luminosity (0.03of a
magnitude), which indicate the presence of a companion star” 3
In the other hand Alpha Librae has a double star. They are close to the ecliptic and can be
obscured by the moon and sometimes even by planets. Alpha-1 “Visual magnitude of 5,15 is
74.9 light years distant from earth….and Alpha-2 magnitude of 2.74 is 78.8 light years distant
from the Sun”3
Brachium or Sigma Librae is a red giant star with a visualization of a 3.29 magnitude and 288
light years away. This star has a pulsation period of 20 days and variations in magnitude over
small stages of 15 to 20 minutes.
Zubenelakrab or known as Gamma Librae, has a size of 3.19 and is about 445 light years distant,
it’s classified as an orange giant from a stellar class K0 III.
Libra is known to home a star known as Methuselah, the oldest known star in the universe! Also
named HD 140283 was believed to have been formed right after the Big Bang. The star is
approximately “14.46 billion years old, while the Universe is believed to be 13.77 billion years
old. The star’s age does not really conflict with the age of the Universe because the values are
uncertain.” 3 It also homes 48 Librae one of the fastest spinners known, projecting a speed of 400
km/s.
Libra has a star named Gliese 581 or HO Librae it’s a red dwarf that star that has at least six
planets. There has been a lot of controversy with planets Gliese 581 d, and Gliese 581 g were at
one point there was hope that there could be signs for life. Then in September 2010 Gliese 581
g, “was classified as a tidally locked planet. Studies show that tidally locked planets may still
have the ability to support life”5 Librae 23 has two planets confirmed it is a yellow dwarf and it
is much older than our own earth sun with an approximation age between 8.4 and 11.1 billion
years.
Libra also has galaxies NGC 5792 with a magnitude of 12.1. NGC 5890 visual size of 14 which
was discovered by the American astronomer Ormondo Stone, NGC 5885 is a spiral galaxy with a
11.8 size, and NCG 5897 with a cluster of a magnitude of 9.
Resources:
1
2
“Libra-Constellations-Digital Images of the Sky” 07/16/04
http://www.allthesky.com/constellations/libra/
“Star Tales-Libra-Ian Ridpath” http://www.ianridpath.com/startales/libra.htm
3
“Libra Constellation: Facts, Myth, Stars, Deep Sky Objects” http://www.constellationguide.com/constellation-list/libra-constellation/
4
“Constelaciones del Zodiaco” http://www.astronoo.com/es/constelaciones-zodiaco.html
5
“Libra-Wikipedia, The Free Encyclopedia” “Libra (constellation)”
http://en.wikipedia.org/wiki/Libra_(constellation)