Observing Libra

The Constellation of The Scales

© Kelly Whitt

May 4, 2007

Libra, the constellation of The Scales, is located on the ecliptic between Virgo and Scorpius. The ecliptic is the plane in the sky on which the sun, moon, and planets travel. As we all orbit the sun on this plane, the solar system objects only pass through the constellations that reside on the ecliptic. These constellations on the ecliptic are known as the zodiac constellations. In the Northern Hemisphere, Libra is best viewed in the spring months.

Libra was once part of the constellation Virgo the Virgin and then part of the Scorpius the Scorpion, represented its claws. As the newest zodiac constellation, Libra is the only one of the twelve on the ecliptic that is not named for a living creature. The Scales are used to symbolize balance or the weighing of goods or issues.

As an observing location, Libra is a smaller constellation and therefore has fewer targets of interest. Its stars are dimmer stars, forming a triangle and two lines stretching down from each end, representing the baskets that would hold the items being weighed.

The Stars of Libra the Scales

The star at the top of the triangle is the brightest in the constellation, Zubeneschamali, at magnitude 2.61. It is a blue star located 160 light-years away. The name Zubeneschamali means "northern claw" and is a remnant from when Libra was part of Scorpius the Scorpion.

The star in the triangle to the right, or south, of Zubeneschamali is Zubenelgenubi. This star's name means "southern claw". Zubenelgenubi is a magnitude 2.75 star with a magnitude 5.15 stellar companion. This double star is easily separated with binoculars. The two are a physical double, both lying 77 light-years away.

The last star that marks the triangle of Libra is Zubenelakrab. Its name means "scorpion's claw". Zubenelakrab is a magnitude 3.91 star lying 152 light-years away.

The star Sigma Librae hangs down below the point of Zubenelgenubi. It is a red star of magnitude 3.25 and 292 light-years away. Hanging down from Zubenelakrab are two stars. The first is 3.60-magnitude Upsilon Librae and below that is 3.66-magnitude Tau Librae, which lies at the border with the constellation Lepus.

Clusters and Galaxies in Libra

In the middle of the constellation is one deep-sky object of note. It is NGC 5897, a globular cluster shining at magnitude 8.6. This globular cluster is a bit more diffuse than the well-known globulars and more irregularly shaped.

There are no bright galaxies in Libra, but there is one that is fairly easy to find if you have a large telescope. It lies just half degree from the brightest star, Zubeneschamali, and in the direction of the next brightest star, Zubenelgenubi. This galaxy is NGC 5885, an 11.7-magnitude barred spiral galaxy.

A recent discovery has put Libra in the news. The first Earth-like planet to be found lies in the direction of this constellation. The planet is named Gliese 581 c. It is a magnitude 10.57 star located one and a half degrees above and slightly to the left (northeast) of Zubeneschamali.

Libra

Print Article

View All Articles

How to subscribe to feeds