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Keyhole Nebula

Carina Nebula, Eta Carinae Nebula, Great Nebula in Carina, NGC 3372

Proper NamesCarina Nebula, Eta Carinae Nebula, Great Nebula in Carina, Keyhole Nebula
Messier NumberNone
NGC/IC NumberNGC 3372
Right Ascension10h 43m 48s
Declination-59° 52' 00"
Distancec.7,500 light years
c.2,300 parsecs
Magnitude+6.2 (illuminating star)
Mean DiameterApparent: c.3°
Actual: c.400 light years
Associated Star(s)Eta Carinae
Optimum VisibilityMarch
NotesThe 'Keyhole' of the Keyhole Nebula is a stream of material forming a dark shape against the background of the vast Eta Carinae Nebula complex. The full Nebula is busy with clusters and other features, notably the Homunculus Nebula surrounding Eta Carinae itself.

The region of space around the star Eta Carinae is a complex and turbulent area. Against the wide backdrop of the Eta Carinae Nebula can be seen an expanding region of dark gas - the 'Keyhole' of the Keyhole Nebula.

The Nebula consists of a huge cloud of ionised hydrogen surrounding the extraordinary star Eta Carinae. Eta Carinae itself is a binary system, consisting of two massive stars in a mutual embrace, each casting off spherical shrouds of matter to form a peculiar dumb-bell shape. It is one of the most massive and luminous stars known, and also one of the most variable. In the mid-nineteenth century, it was one of the brightest stars in the sky, but has now faded very considerably.

Surrounding the hourglass of Eta Carinae is an extensive cloud of ionised gas, within which several star clusters are in the process of forming. Clouds of dark obscuring dust swarm through the nebula, too, and the most prominent of these gives the nebula its name. This is a vast and rapidly expanding dark cloud in the central parts of the main nebula, that gives its common name of the 'Keyhole'.


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