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The Southern Cross

The Southern Cross is one of the best known patterns in the night sky, and the most familiar star pattern for us in the southern hemisphere.

Composed of five stars it forms the shape of a cross and is the most distinctive feature of the constellation Crux. It is the smallest constellation in the sky. The Southern Cross is notable for containing two bright stars, Acrux and Gacrux, the top and bottom stars which point the way to the Southern Celestial Pole.

It is one of the easiest star groups to identify in the sky and it has significance in a number of cultures in the southern latitudes.

The five stars that form it are represented on the flags of Australia, New Zealand, Papua New Guinea, Samoa, and Brazil. The Southern Crossx is also included in the national anthems of Australia and Brazil.

The Southern Cross dominates the Crux constellation and so is often confused for the constellation itself. The constellation Crux or Crucis contains many more than five stars. The stars that form the cross pattern are the brightest ones. The cross-shaped pattern can easily be seen from the southern latitudes at any time of year.

Observers in the tropical latitudes of the northern hemisphere can see it near the horizon in winter and spring, but only for a few hours every night. I once saw it around early June on the Tropic of Cancer.

The five stars of the Southern Cross are believed to be between 10 and 20 million years old.

The Southern Cross is located near the larger constellation Centaurus, which surrounds it on three sides. Crux constellation is also bordered by Musca, the Fly.

Alpha and Beta Centauri pointing to the Southern Cross

To find the Southern Cross, first look for the two very bright stars nearby, Alpha and Beta Centauri. Following a line from Alpha to Beta Centauri will take you near Gamma Crucis, the top star in the cross.

The Southern Cross spans only six degrees from north to south.

The Southern Cross should not be confused with the so-called False Cross, formed by four other bright stars in the vicinity. The X-shaped False Cross bears a slight resemblance to the Southern Cross and is oriented in approximately the same way, but the four stars – two belonging to the constellation Vela, the Sails, and two to Carina, the Keel – are located a bit farther to the north, and they do not point to the Southern Celestial Pole. They will, however, mark the pole’s location around the year 8600, when the pole has gradually shifted to a point just east to the intersection of the False Cross’ cross-arms.

The Coalsack Nebula is located approximately 600 light-years away from Earth in the southern part of the Southern Cross. This seemingly starless dark patch is actually an opaque interstellar dust cloud that obscures the light of the background Milky Way stars. The first European to see this remarkable object was probably the Spanish navigator and explorer Vincente Yanez Pinzon when he sailed to the South American coast in 1499. The Coalsack earned the nickname “Black Magellanic Cloud” in the 16th century, apparently rivalling the prominence of the Small and Large Magellanic Clouds, the two dwarf irregular galaxies that shine brightly in the skies of the Southern Hemisphere. The Incas tell that the god Ataguchu, in a fit of temper, kicked the Milky Way and a fragment flew off, forming the Small Magellanic Cloud where it landed on the sky, and leaving the black mark of the Coalsack behind. Beware of Inca gods in a bad mood! Another famous sight seen from southern latitudes — though it can creep into view in tropical northern latitudes — is the Southern Cross, or Crux. This cross-shaped constellation has assumed great significance in the cultures of the Southern Hemisphere, even as far back as prehistoric times. So distinctive and evocative is the Southern Cross that the national flags of Australia, Brazil, New Zealand, Papua New Guinea, and Samoa all include a representation of it. The European Southern Observatory (ESO) has also acknowledged the significance of Crux as the foremost constellation of the southern skies, and has proudly incorporated the cross-shaped symbol into the ESO logo. Its Mapudungun name (that is, in the language of the native Chilean Mapuche population), Melipal, was given to the third Unit Telescope of the VLT on Paranal. Image: ESO/S. Brunier

Donna the Astronomer

I am a keen astronomer lucky enough to live and work in Coonabarabran the Astronomy Capital of Australia! I am a ‘Drover’s Brat’ and discoverer of a couple of comets and asteroids. I operate Milroy Observatory and can show you how to best integrate dark sky experiences into your tourism, farm stay or AirBnB business.

This Post Has 2 Comments

  1. Ggreybeard

    Here in Sydney suburbia we can make out the five main stars but not much else. I guess you would see a few more stars from your location in the Astronomy Capital of Australia.

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