The Diamond Cross is an asterism

Asterism (astronomy)

In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...

 in the southern constellation Carina

Carina (constellation)

Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...

. The Diamond Cross is composed of four bright star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s: Beta

Beta Carinae

Beta Carinae is the second brightest star in the constellation Carina and one of the brightest stars in the night sky, with apparent magnitude 1.68. It is the brightest star in the south polar asterism known as the Diamond Cross, marking the southwestern end of the asterism. Beta Carinae also has...

, Theta

Theta Carinae

Theta Carinae is a star in the constellation Carina. It is the brightest star in the open star cluster IC 2602, and it marks the northeastern end of the Diamond Cross asterism....

, Upsilon

Upsilon Carinae

Upsilon Carinae is a binary star in the constellation Carina. It is part of the Diamond Cross asterism in southern Carina....

 and Omega Carinae

Omega Carinae

Omega Carinae is a star in the constellation Carina. With a declination greater than 70 degrees south of the celestial equator, it is the most southerly of the bright stars of Carina , and it is part of a popular southern asterism known as the Diamond Cross. ω Carinae is a blue-white B-type giant...

. These four bright stars create an almost perfect diamond shape, hence the name "Diamond Cross". The entire asterism is visible to all observers south of 20°N latitude

Latitude

In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

. It bears a striking resemblance to Crux (The Southern Cross) and the False Cross

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:...

, and, like them, it lacks a central star in its cross pattern, creating a diamond-shaped or kite-like appearance. Both the Diamond Cross and the False Cross are sometimes mistaken for the true cross Crux, although the False Cross has always been a worse deceiver than the Diamond Cross, because most of its stars have approximately the same declination

Declination

In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...

s as the stars of Crux.