Derivation
As a far southern constellation, Ara is today almost invisible from Europe at any time of the year.
Between 2,000 and 3,000 years ago, though, it was clearly visible from southern Europe and northern
Africa during the summer months. The Greeks of that time called it Thytérion
or Thysiastérion, the Altar of Sacrifice, perhaps because it rose
in the sky at a propitious time of the year. This tradition was inherited by the
Romans, who gave the constellation the name we know today: 'Ara' is the Latin word for 'Altar'.
Stars
There are few bright stars in this region of the sky. The two brightest, Alpha and Beta Arae,
are coincidentally almost exactly the same magnitude of +2.8. Though the Beta star is almost
400 light years beyond the Alpha, it is much more luminous.
Some of Ara's stars are very distant: both Gamma Arae and Theta Arae lie more than 1,000
light years away, but both of these stars are brilliant supergiants, and so are clearly
visible to the naked eye of an observer on Earth.
Star Clusters
The most notable cluster in Ara is a Globular group that lies somewhat 'below' the plane
of the galactic disc. NGC 6397 is a fairly loose ball of stars lying approximately 7,000
light years (about 2,000 parsecs) from Earth's Solar System.
A little nearer to Earth, at about 4,500 light years distance, is an open star
cluster, NGC 6193. This is quite a young cluster on a cosmic timescale, and still surrounded by
much of its original nebulous material.
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The constellation of Ara describes a region towards the centre of our galaxy, and
somewhat 'below' the galactic plane.
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