Slashdot Mirror
Supernova 2011b Gradually Fading
An anonymous reader writes "The recent stellar explosion known as 'supernova 2011b' is gradually fading after outshining its host galaxy for over a month. The explosion first flared up in early January, and peaked at magnitude 12.9, putting it within the reach of many amateur telescopes. The host galaxy, NGC 2655, lies 64 million light years away, meaning that the star exploded while the dinosaurs still roamed the planet. My own sketches are available at gkastro.tk/."
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A supernova explodes. Slashdot reports 64 million years later.
If enithin kan gow rong it whil. (Murfey)
http://www.novaresource.org/
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That's not correct. Or at least that's not how simultaneity and past/present/future are defined in relativity, which seems to be what you're referring to with "frame of reference". I suppose you could define 'now' in that way... but that's not how it's defined in modern physics.
In our inertial reference frame, it happened ~64 million years ago. In the star's reference frame, it also happened ~64 million years ago. It's true there is no such thing as a universal reference frame, so one can certainly construct inertial reference frames (e.g. with large velocities relative to us) where the event occurred at different times. Even 'now' (in that reference frame). But the velocity difference between us and the supernova is modest (in the grand scheme of the universe) and thus our two references frames roughly agree about simultaneity and so on.
It's a strange misconception that people interpret relativity to mean that all space-time events on our past light-cone are 'now'. Relativity doesn't say that. It includes a well-defined concept about what is in the past, what is in the future, and the boundary between them being 'now'. We are not immediately aware of all space-time events on the 'now' plane... because it takes time for their signals to reach us. But when we receiving signals we are able to reconstruct and deduce what happened at previous moments. It is true that inertial reference frames do not agree on what 'now' means, and thus don't agree on simultaneity. But within a particular inertial reference frame, there is a meaningful concept of 'now'.
Again, I suppose you could define 'now' in such a way, but it's not at all useful to think of the big bang happening 'right now' as we look far out into space. It makes much more sense to think in terms of it having happened 13.7 billion years ago, and we're only now receiving signals from the afterglow of the big bang from distant regions of space.
Photographically it is well within reach of DSLRs equiped with a 200mm lens. I managed to go down to magnitude 17 (or 100 times less bright) and even fainter with a Canon 20D and a 200mm f/2.8 lens, placed on a tracking mount and exposed for about 2 hours (accumulated in exposures of a few minutes). I'm sure it would even lie within the limits of a 50mm lens. The problem becomes distinguishing it from the host galaxy.
Visually it was within reach of 4.5" beginner scopes at dark locations! These will set you back less than $200 nowadays. A $1000 12" would have produced very decent views of the SN together with it's host galaxy. There are a lot of telescopes of this size around. You obviously should take the time to visit a public observatory once.