IC

Index Catalogue

The Index Catalogue —also known as the Index Catalogue of Nebulae, the Index Catalogue of Nebulae and Clusters of Stars, IC I, or IC II— is a catalogue of galaxies, nebulae and star clusters that serves as a supplement to the New General Catalogue...

 2391 (also known as the Omicron Velorum Cluster) is an open cluster

Open cluster

An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Vela

Vela (constellation)

Vela is a constellation in the southern sky. Its name is Latin for the sails of a ship, and it was originally part of a larger constellation, the ship Argo Navis, which was later divided into three parts, the others being Carina and Puppis.-Stars:...

. It has been purported to be first described by the Persian astronomer Al Sufi in about 964. It was also found by Abbe Lacaille and has been cataloged as Lac II 5. The cluster is at a distance of about 500 light-year

Light-year

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

s away from Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 and can be seen with the naked eye

Naked eye

The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...

. The cluster has a total visual magnitude of 2.5. The open cluster spans an area of sky of about 50 arcminutes, and contains about 30 stars. The cluster might be about the same age as the open cluster

Open cluster

An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 IC 2602

IC 2602

IC 2602 is an open cluster in the constellation Carina. It was discovered by Abbe Lacaille in 1751 from South Africa. The cluster is at a distance of about 479 light-years away from Earth and can be seen with the naked eye...

, and have a lithium depletion boundary

Lithium depletion boundary

The lithium depletion boundary technique is a method proposed for dating open clusters based on a determination of the lithium abundances of a cluster's stars whose masses are at about the hydrogen burning mass limit....

age of about 50 million years old.

External links

• http://www.seds.org/messier/xtra/ngc/i2391.html
• http://www.atlasoftheuniverse.com/openclus.html
• http://www.journals.uchicago.edu/PASP/journal/issues/v111n756/980173/980173.html
• Simbad