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by Jane Houston
12,000 years ago a supernova event marked the catastrophic end in the life of a massive star in the constellation Vela, a large constellation representing a sail on the giant ship Argo in the southern sky. The self-destruction of the star released a huge amount of energy as radiation, but a substantial fraction of the force of the explosion blasted the outer part of the supernova into an expanding shell of matter that traveled through the almost empty space between the stars.
As the rapidly moving blast wave encountered the relatively stationary interstellar medium it created a very narrow, luminous shock front that appears as a huge faint nebula.
The Vela Supernova Remnant is one significant part of the Gum Nebula (Gum 12), a complex shell of faint nebulous filaments. It is the largest object in the sky, apart from the Milky Way, and measures 36 degrees across Vela and its neighboring constellations. It is a half shell of filaments similar to the Veil Nebula in Cygnus, and was discovered by Australian Astronomer Colin S. Gum in 1952.
A haunting David Malin photograph of a portion of the Vela supernova greets me every morning. Cut out of an AAT Astronomy Calendar and framed, it is hung on the wall right above where I store my two LITEBOX reflector telescopes. I added the Vela Supernova Remnant to my Ayers Rock observing projects a long time ago.
My first challenge was to identify the constellation of Vela, sort of a sideways Auriga shaped constellation above the Orion arm of the Milky Way. Then I had to identify the triangle of three stars - zeta Puppis, lambda Velorum and gamma Velorum - a Wolf-Rayet star and a double star as well.. Most of the significant areas of the Gum Nebula are contained within this triangle, nestled between these amazing stars in this awesome section of the sky. This area is too large to fit on one Uranometria page, so it took me a while to see the triangle, though all three stars are very bright. Volume 7 of the Webb Societies Deep Sky Observers handbook series - the Southern Sky volume was a great help. But the good ship Argo (and all its constellation segments) contains more naked eye bright stars than any other constellation - 676 stars to be exact. That's alot of stars to wade through. Once I found the triangle I placed my 22 Panoptic in the focuser of my 12.5 inch reflector and took a little 84X spin around Vela and Puppis. I knew this object would be difficult, much like looking for the Veil Nebula in a light polluted front yard without a filter. I saw nothing at first!
I borrowed an OIII filter and tried again. I thought perhaps I had detected a very subtle change in the view through the eyepiece, but it was so subtle that I called others over for a look. No one else could see anything for sure, either! I offered Barry Peckham the opportunity to trade telescopes for a little while. The extra aperture offered in his 15 inch LITEBOX reflector as compared to my 12.5 incher, might just make the difference between seeing and believing.
Switching to his 27 Panoptic with the OIII filter in the F5.5 15 incher did indeed make a difference! Soon long ribbons of nebulosity snaked through the eyepiece. Just like the Veil Nebula, the circular shaped shell of star stuff twisted and curled in delicious tendrils of filamentary magic. It was very dim, but the long pencil shaped ribbons and streamers could be followed easily by pulling down on the big dob. Chunky and curvy sections abounded. Soon the snaky line was not only in the eyepiece, but behind the LITEBOX as well. Everyone had to take a look at history!
That long pencil shaped remnant turned out to be the Pencil Nebula. This is an outlying wisp of the Vela supernova remnant, almost the only sign of the eastern part of this vast bubble of expanding shock wave. Many fine, tangled filaments are seen in the western part of the nebula, but in the east, most of it is hidden in dust. This is one of the brighter eastern fragments, and its unusual linear appearance in the telescope was remarked on by Sir John Herschel who discovered this nebula in the 1840s. This spindly shape is the source of its popular name.
I cataloged many individual objects within this golden triangle in my sketch book and note book. There were dark nebulous patches, double and triple stars, fascinating planetary nebulae of the most beautiful hues of green and blue and clusters, and clouds galore. But my most vivid memory of this night in the Australian outback was to imagine how this area looked to the Aborigines 12,000 years ago when a brilliant light shown in their sky for a month or more. A star burst the size of the moon! Star burst carvings in New South Wales may be the observers log from these ancient and noble accidental astronomers.