Vela (Vel)
Vela (pronounced vay-lah) was originally part of a larger constellation named Argo Navis, ship of the Argonauts used by Jason to retreive the Golden Fleece in Greek mythology. Vela became the Sail, Carina the Keel, Puppis the Prop, Pyxis the Compass. When French astronomer Nicolas Louis de Lacaille (1713-1762) arranged Argo Navis into more managable areas of sky in 1750, the stars retained their original letters and numbers. Consequently Vela was left with no stars designated as Alpha or Beta, both of these ended up in carina. Vela's brightest star is Gamma Velorum which shines at magnitude 1.8. Under normal convention, a star labelled Gamma would be the third brightest star in the constellation.
Two of Vela's stars, Kappa and Delta Velorum, when combined with two stars of neighbouring Carina, Iota and Epsilon Carinae, form what is known as the False Cross. The true cross, some 20º to the East, is smaller and moe prominent with brighter stars. Once recognised there should not be any confusion between the two.
Vela culminates high in the Southern sky above Carina early in the month. The Milky Way passes through a large portion of the constellation and as a result there are many doubles and open stars clusters. As far as double or multiple stars systems go Gamma Velorum (Dunlop 65) is hard to beat. It is abeautiful double star set in a splendid field which is easyily resolved in good binoculars and small telescoeps. Another fine pair of stars almost at right angles to Gamma is in the same field.The bright component of Gamma Velorum is the most luminous and nearest of the 'Wolf-Rayet' class of stars. These stars have extremely high temperature and only about 100 are known. Most are components of binary stars, and is thought that novae have a similar makeup toward the end of their life. Many of the central stars of planetary nebulae also have very similar spectra to the Wolf-Rayets, but are less luminous.
An easy bright open star cluster catalogued as NGC 2547, is great for small telescopes. Composed of bright stars in loops and arcs, it stands out against a field strewn with fainter background stars. Another popular object, the strange and complex planetary nebula NGC3132 or the small Eight-Burst nebula, lies on the Vela / Antlia border. Easily visble in small instruments as an oval of nebulosity it has a 10th magnitude central star. The 'Eight-Burst' is remarkable on long exposure photographs, showing several rings of nebulous material superimposed on each other. The energy needed to make the nebula glow does not come from the visible star. It is instead fuelled by a faint 16th magnitude companion 1.65 arc seconds from the primary, it has a very hot surface temperature of about 100 000º Kelvin.
Vela is home of the largest nebula in the sky, the 30 by 40 degree Gum Nebula (it spills over into several other constellations). It was discovered by Australian Colin Gum from a mosaic of photographs taken in hydrogen alpha light. Within the Gum Nebula lies the Vela Supernova Remnant; it's delicate wispy filaments are superb on photographs. A very unusual star, similar to the pulsar in the famous Crab Nebula, known as the Vela Pulsar lies within the supernova remnant. It was originally detected by radio astronomers, but has sincebecome only the second pulsar to be observed optically.
Interesting facts:
1) Ranked in 76th size
2) Has no Messier Objects.
3) This constellation contains a very onusual object known as the 'Vela Pulsar'. It was the scond of these type s of objects to be optically observed, the first being the pulsar within the Crab Nebula (M1).
4) The star Gamma Velorum is a Wolf Rayet type star surrounded by nebulosity, visible in 8" and larger apertures.
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