|Vela, the sails of the great ship Argo
Navis, sit to the north of Carina the Keel. For more on the story
of Argo Navis see Puppis the Stern.
This constellation is not always appreciated
as much as it should as it contains some fine sights and some interesting
objects, and not all of them in the Milky way, which covers half of this
constellation. In May 1999 a nova was sighted by dedicated variable
star observer and comet discoverer Peter Williams of Sydney, Australia,
below mu (m)
Velorum which was easily visible for a week. It also contains
the brighter parts of the Gum nebula which is the remnants of a supernova
explosion that was recorded by the ancient Sumarians 6000 years ago.
It shows up best on photographic plates and it's true nature was recognised
by Australian astronomer Colin Gum in 1952. The pulsar that was the
result of this supernova was visually identified using the Anglo-Australian
Telescope in 1977. A very large aperture telescope, an OIII filter
and steady seeing is needed to glimpse this faint but extensive nebula.
Velorum on the far west side of the constellation is the brightest Wolf-Rayet
star in the sky. These stars have masses 10-50 times larger than
our sun and burn very hot, up to 90 000K (hotter than O class stars) and
show strong emission lines in either ionised helium, carbon, oxygen or
nitrogen. Gamma Velorum shows strong lines in ionised carbon.
It is thought that these stars are the centre of O class stars left after
their outer layers have been ejected at high speeds, as some Wolf-Rayet
stars have a ring nebula surrounding them. About half of them are
also binary stars, as is gamma Velorum.
Two stars from Vela, delta (d)
and kappa (k)
Velorum, make half of what is known as the False Cross. The False
Cross is four stars of similar shape to Crux, further to the west in the
Milky Way, that some people mistake for the Southern Cross. However
once the "real" cross is learnt you'll notice they are quite different,
the False Cross is the larger of the two but has no Pointers and no "fifth"
star in the middle of one side.
An excerpt from Johan van
Keulen's Boeck zee-kaardt, 1709.
Vela represents the sails
of the old constellation of Argo Navis.
This article is ©2002
Stargazers Astronomy Shop