Lupus, In The Sky
In astronomy, an ancient constellation of the southern sky, located between the
constellations Centaurus and Scorpius. Lupus has no extremely bright stars but
is densely populated with stars of second and third magnitude. It is a
constellation rich in double stars and multiple stars. A few open clusters and
other deep-sky objects can be seen with binoculars within its boundaries; many
more are visible with a more powerful telescope. The name Lupus is Latin for
"wolf," but the wolf appellation apparently did not become common
until the Renaissance. The ancient Greeks and Romans figured the grouping as a
wild animal of no specific type. Representations among the Mediterranean
civilizations that recognized this grouping included a lioness, a leopard, a
male horse, and a howling dog. Lupus is often linked to the Centaur rearing
above it, though the symbolism may be forced. As examples, the Centaur is
sometimes described as reaching out to grasp Lupus and carry it to the Altar (Ara),
a nearby constellation, or as impaling Lupus on a pole. For a long time,
however, the stars were not clearly separated from those in Centaurus.
Eratosthenes, a Greek astronomer of the 3rd century BC, described these stars as
a wine skin from which the Centaur was about to drink. It fell to Hipparchus of
Bithnya, a Greek astronomer of the 2nd century BC, to separate the stars from
Centaurus and give the constellation a name, Therion (Wild Animal). The great
astronomer Ptolemy of Alexandria cataloged the constellation as Therion in the
2nd century AD, but alternative names continued to appear on sky maps for
centuries.
Lupus forms part of the disklike zone of young, bright stars called Gould's Belt
that slices through the Milky Way galaxy at an angle of about 18 degrees.
Sprinkled around the edge of Gould's Belt are star nurseries, all of about the
same age. The Dutch astronomer Adriaan Blaauw has proposed that all of these
star nurseries originated at the same time, about 30 million years ago, when
compression of dust and gas squeezed a large molecular cloud and caused a burst
of star formation. The very active Orion star nursery was one result; the
association of young, hot stars called the Upper Centaurus-Lupus Stellar
Association was another. Although stars in constellations generally move in
unrelated (to each other) fashion, most of the stars in this association are
moving together at the same speed, 16 miles (25 kilometers) per second, in the
direction of Beta Columbae.
The Upper Centaurus--Lupus Association lies in the part of Gould's Belt that
extends above the plane of the Milky Way, so that a portion of the Milky Way
runs through Lupus. This location brings within the boundaries of the
constellation some attractive star fields and their associated nebulae (both
bright and dark), galaxies, and clusters. The seventh-magnitude globular cluster
NGC 5986 can be seen with binoculars toward the northern end of the
constellation. This cluster is not extremely tight, and some individual stars
can be resolved with an amateur-sized telescope. A few degrees north of NGC 5986
is a dark band in the sky known as the dark nebula B 228. A dark nebula, or
absorption nebula, is a cloud of gas and dust that blocks light coming from
behind. As a result of absorption of their emitted light, the few stars visible
in the vicinity of B 228 appear unusually red. A few open clusters, including
the sixth-magnitude NGC 5822, lie near the southern border of the constellation.
On the western border, about 5 degrees northwest of Alpha Lupi, is the Wolf-Rayet
ring-type planetary nebula IC 4406, visible with a small telescope. The central
stars of the Wolf-Rayet nebulae are thought to be the hottest stars in the
universe.
The figured part of the constellation, the stars that make up the wolf shape,
contains several bright single, double, and multiple stars--none of which have a
name. Alpha, Beta, Gamma, Delta, Epsilon, and Zeta Lupi form a rough oblong
representing the body and front legs of the animal. Alpha Lupi, which might be
thought of as the eye, is a magnitude 2.3 blue giant about 620 light-years
distant from Earth. About 6 degrees northeast, marking the end of the ruff, is
Beta Lupi, a magnitude 2.7 blue-white giant about 680 light-years distant. Gamma
Lupi, where the tail and hind legs emerge from the animal's rump, is a magnitude
2.8 blue-white binary star whose close companion cannot be separated with a
small telescope. Northeast, along the more northerly of the hind legs, is a wide
multiple system, the Phi series, consisting of a magnitude 3.5 yellow-orange
giant star with two faint companions. The other hind leg is marked by the double
star Eta Lupi, whose components are a magnitude 3.4 blue-white primary and a
fainter, whitish yellow companion. Back in the oblong representing the animal's
body are the multiple star systems Pi and Mu Lupi, and the double star Kappa
Lupi, whose magnitude 3.9 and 5.7 blue-white components can be separated with a
small telescope. In the Southern Hemisphere Lupus is best viewed between March
and September. It reaches its highest point in the sky at 10:00 PM on June 1,
when, for an observer in the mid-southern latitudes, it appears about two thirds
of the way up the sky. Lupus lies northeast of the very bright star Alpha
Centauri and follows Centaurus across the sky. About half of Lupus is visible
from the mid-northern latitudes in late spring and early summer. For a northern
observer, Lupus lies southwest of the red supergiant Antares and precedes
Scorpius across the sky.
Lupus (the Wolf) Some Facts:
Genitive: Lupi
Abbreviation: Lup
Declination: -29.8 degrees to -55.3 degrees
Right ascension: 14 h 13 m, to 16 h 05 m
Area covered: 334 square degrees
Number of stars brighter than sixth magnitude: 70