Special Sub-Topic: The Southern Cross and its Neighbourhood Click Here To Play: The Southern Cross and its Neighbourhood

Which of the five stars in the Southern Cross constellation are usually not so easily visible to the naked eye or by using binoculars?

Epsilon Crucis. Set in a kite-like formation, four major stars and one fainter one make up the Southern Cross. Set at the bottom is Alpha Crucis (Acrux), 321 light years away from us. The two arms of the cross are formed by Beta Crucis (Mimosa) and Delta Crucis. The top star is Gamma Crucis (Gacrux), a red-orange star, 88 light years away. Below Delta Crucis is the fainter Epsilon Crucis, quite distant at 570 light years. Of course, there are many other faint stars in the constellation that can be viewed through a telescope.

To locate south by means of the south celestial pole, you make use of the Southern Cross together with two other bright stars commonly known as what?

Pointer Stars. The Pointer Stars are Alpha Centauri (Rigil Kentauri) and Beta Centauri (Hadar). To find south, extend a line through the Southern Cross, top to tail, and a similar line from the Pointers. The two lines meet close enough to the south celestial pole to reliably indicate south.

Which two stars in the Alpha Centauri system orbit each other?

Alpha Centauri Al and Alpha Centauri B. Alpha Centauri is one of the brightest stars in the sky. It actually consists of a binary star system, named Alpha and Beta (AB), orbiting each other. The third star is called Proxima Centauri, much fainter and much further away from earth than the other two. Because there are only three stars there are no stars such as Gamma, Iota or Zeta Centauri.

South of the 34 degree latitude, the Southern Cross is visible all-year round, never dipping below the horizon. What is such a constellation called when it can always be seen?

Circumpolar. From certain latitudes, stars are defined as being circumpolar because they are close to the celestial pole and therefore always visible. Areas south of the 34 degree latitude include a part of southern Australia, Tasmania and New Zealand. On the other side of the world, parts of Argentina and Chile also lie south of that latitude. Protuberant means bulging, sinanthropus is an apelike man, while there is no such thing as a canon star.

Close to the Southern Cross, there is another cross-shaped constellation. Because it can be mistaken for the Southern Cross, it is commonly known as what?

False Cross. The False Cross lies in the constellation of Vela (named after the sails of a ship). The cross is made up of Delta and Kappa Velorum and Iota and Epsilon Carinae. The stars are fainter than those of the Southern Cross and lack the tell-tale bright Pointer Stars in the vicinity.

What is the name of the dark nebula close to Alpha and Beta Crucis?

The Coal Sack. The Coal Sack is a region of dark gas that only shows up because it blocks out the light of stars behind it. It is easily visible against the rich starfield of the Milky Way around it. It is estimated to lie at 600 light years from earth.

What is the common name for Open Starcluster NGC 4755 seen close to the Southern Cross?

The Jewel Box. An open cluster is a collection of stars that seem grouped together in a loose formation. The Jewel Box lies just outside the Southern Cross, close to Beta Crucis. It was discovered in 1751 by Abbe Lacaille at Cape Town, South Africa. Set against the background of the Coal Sack, the collection of stars shine red, white, blue and orange. Through a telescope, you can make out more than fifty stars.

What type of stellar phenomenon is Omega Centauri?

Globular Cluster. Omega Centauri (NGC 5139) is the biggest globular cluster in the Milky Way, made up of an estimated five million stars. The cluster is part of the constellation of Centaurus.

In 1843 the star Eta Carinae appeared to explode into a supernova. It ejected a giant bubble of gas. In what nebula within the greater Carinae nebula is the star found?

Keyhole. The Carinae nebula lies on the other side of the Southern Cross as the Pointer Stars. Within it lies the Keyhole nebula. Eta Carinae is a massive blue star that brightens and dims over time. In 1843 it brightened to virtually outshine every other star in the sky as stars do when they become supernovas and die. Because Eta Carinae survived the event, the term 'supernova imposter event' was coined. The Horsehead is a dark nebula, Omega is an emission nebula and Cat's Eye is a planetary nebula.

Many countries in the Southern Hemisphere feature the Southern Cross on their national flags. Name one exception.

Argentina. The flags of Australia, Papua New Guinea and Samoa feature the five stars of the Southern Cross, while New Zealand's flag omits the fainter Epsilon Crucis. Brazil's flag features a star map of the southern sky. Argentina's flag has a yellow sun on it.