NGC 3372, the Eta Carinae Nebula. Image courtesy of ITA.

The Eta Carinae Nebula (also known as the Keyhole Nebula, the Great Nebula in Carina, the Carina Nebula, or NGC 3372) is a large bright nebula which surrounds the star Eta Carinae, one of the most massive and luminous stars in the galaxy. The nebula lies at an estimated distance between 6,500 and 10,000 light years from Earth. It is located in the constellation of Carina. The nebula contains multiple O-type stars.

This nebula is one of the largest H II regions in the Milky Way galaxy. It has a visual magnitude of 1.0. The astronomical coordinates are:

• R.A.: 10^h 43.8^m
• Dec.: -59° 52'

The nebula is one of the largest diffuse nebula in our skies. Although it is some four times as large and even brighter than the famous Orion Nebula, the Eta Carinae Nebula is much less well known, due to its location far in the southern hemisphere. It was discovered by Abbé Lacaille in 1751-52 from the Cape of Good Hope.

Within the large bright nebula is a much smaller feature, immediately surrounding Eta Carinae itself. This small nebula is known as the Homunculus Nebula (from the Latin meaning Little Man), and is believed to have been ejected in an enormous outburst in 1841 which briefly made Eta Carinae the second-brightest star in the sky.

Keyhole Nebula

A portion of the Eta Carina Nebula is known as the Keyhole Nebula. The Keyhole Nebula is actually a much smaller and darker cloud silhouetted against the much brighter background nebula.

External links

• The Eta Carinae Nebula @ SEDS NGC objects pages (http://www.seds.org/messier/xtra/ngc/n3372.html)
• NASA APOD: The Great Nebula in Carina - July 19, 1999 (http://antwrp.gsfc.nasa.gov/apod/ap990719.html)