Wednesday, 3 August 2016

A veil in summer sky

I've already talked about supernovae before, cataclisms that mark the death of a giant star. Nuclear fusion becomes unstable... the star collapses under its own gravity which in turn causes the violent expulsion of the entire star's atmosphere in a matter of seconds. The acute energy release may be as high as 1044 Joules or the entire energy output of the Sun during its whole 10-billion year life! The expelled matter may reach velocities up to 30.000km/s or one tenth of the speed of light! 

But as dramatic and spectacular as they appear, the remains of the star fade quickly and after a couple of months all that's left is an incredibly dense core that consist of neutrons. Although perhaps only 10km in diameter,the neutron star's density is 1015 higher than that of normal matter and hence it's incredibly heavy. In some cases it may be heavy enough to continue to collapse under its own gravity until it has become a point. At which stage it becomes a black hole: an object with such a high mass that you'd need to travel faster than light in order to escape from it. That's why we can't observe anything within them because nothing, not even light, travels fast enough to escape. 

But supernovae are not just the end. The blast is so strong that heavier elements such as metals are formed and expelled into the universe. So in a sense a supernova feeds the universe with a lot of complex elements which one day may be needed for the creation of planets and... life. And not all's destroyed instantly. Almost 6.000 years ago a vehement supernova lit up 1.400 lightyears from us in the constellation of Cygnus. As far as I'm aware no observation reports from that day exist so we can only speculate how our ancient ancestors stared at the sky in awe when an insignificant star suddenly became brighter than the full Moon. Now, thousands of years later, the remains of that explosion are still visible in a small to medium telescope: the Veil nebula. What I've sketched here is just a part of the eastern region. The total Veil nebula complex is 110 lightyears in diameter, or in our sky this equals 6 full moons, and continues to expand at a breathtaking rate. Gas filaments that mainly consist of oxygen are heated up and ionised by the blastwave of the supernova explosion and start to emit light themselves. Exactly these frail filaments are what makes this nebula so jaw-droppingly lovely to look at and in a big instrument such as my binoscope the spectacle surpasses even the wildest imagination. I just had to share this with you and I sincerely hope that you enjoy it.

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