The universe is always changing. The stars over our heads at night look eternal, but the firmament is far from permanent. Polaris wasn’t always the (northern) pole star, but Vega was, and will be again in another 12 millennia. All the stars you see are moving, rather fast actually, just imperceptibly slow at this distance and in our infinitesimal frame of time reference. If people were rocks, who regularly respond to each other’s requests with “Hang on a million years!” before obliging, the stars might appear as satellites or planes do to us. Maybe as young pebbles they’d like in green fields and hold contests to make up patterns from the stars before they dissipate, like us short-lived humans do with clouds.
Anyway, on August 14th, Japanese amateur astronomer Koichi Itagaki of Yamagata, Japan, found something new: Nova Delphini 2013.
What we call stuff in the universe reveals that our changing understanding of its nature is far outpacing our bureaucratic ability to determine names. Pluto is a good example. The word “nebula” is another. Originally named for fuzzy patches in telescopes of indeterminate origin and structure, some of them turned out to be galaxies, others giant clouds of gas where stars are created, and others much smaller but expanding gas shells of Red Giants that collapsed into White Dwarves and blew a giant bubble as a last hurrah.
Novae and Supernovae serve as another example. Nova means “new” and the term originally referred to what appeared to be new stars. New stars that were really bright were called supernovae. Makes sense.
But now we know the process that creates each is very different. Supernova come in two different types, and are basically big explosions that destroy the original star, either a white dwarf or a super giant.
Nova are rather different, and happen when a white dwarf member of a close binary star system sucks up (accretes) enough helium and hydrogen from its neighboring star that gravity causes the plasma to fuse on the dwarf’s surface, releasing a lot of energy (including light). In a nova, the host star is not destroyed, and white dwarves can host multiple novae over time.
Nova Delphinus 2013 was visible to the naked eye, and might still be in a very dark location. I tried to see it but couldn’t, but I did manage to catch it in this photograph, taken from my back yard here in Geneva. If you click through to the full size image (it might take a bit to load it) and click again to get the full size view, the Nova is the larger/brighter of the two stars in the middle of the blue circle. You will notice that at this magnification the stars are not dots but short lines…my camera was on a tripod and not a mount that tracks for the earth’s rotation. So you see the effect of us spinning…as I said, everything is changing.