The Caldwell Objects

8 5
Omicron Velorum Cluster
IC2391
Type: Open Cluster
Con: Vela
RA: 08 h 40.3 m
Dec: -52° 55'
Mag: 2.5; 2.8 (O'Meara)
Diam: 60'
Dist: 500 light-years
Disc: Abd al-Rahman al-Sufi,
about A.D. 964
H ERSCHEL: None.
GC:None.
IC: Cluster, compressed, includes star
of magnitude 3.7 (o Velorum).
T HREE MAJOR " SUPER -
clusters" of relatively young
stars dominate our region of
the Milky Way: the Hyades
supercluster, which includes
the Beehive Cluster, or
Praesepe (M44); the Sirius
supercluster, which contains
the loose gathering of bright
stars in Ursa Major; and the
Pleiades supercluster,
containing the Pleiades, the
Alpha Persei Moving Cluster,
and
IC 2602 (Caldwell 102). But there are other stellar
superclusters in our galactic neighborhood, one
of the more conspicuous being the IC 2391
supercluster, which comprises IC 2391 (Caldwell
85) — a large naked-eye cluster in Vela — and
some 60 field stars. This supercluster's members
are nearly moving together through
85
space, and at least 95 percent of their collective
motion is directed toward a spot in Lepus at right
ascension 5 h 49 m and declination -12° 26'.
IC 2391 is commonly known as the Omicron
Velorum Cluster because the brightest of the
cluster's 30-odd members is the β Cephei-type
variable star Omicron (o) Velorum, which
The Caldwell Objects 339