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New Supernova Seen In Nearby Galaxy M82
The Bad Astronomer writes "A new and potentially bright supernova was just discovered in the nearby galaxy M82. This is a Type Ia supernova, the catastrophic explosion of a white dwarf. It appears to be on the rise, and may have been caught as much as two weeks before peak brightness. It's currently already brighter than magnitude 12, and may get to mag 8, easy to see in small telescopes. The galaxy is less than 12 million light years away, so this may become one of the best-studied supernovae in recent times. Type Ia supernovae are used to measure dark energy, so seeing one nearby is a huge boon to astronomy."
Since no information can travel faster than light, for all intents and purposes and discussions of causality it is happening right now. Since we are just entering its light cone, anything outside of it is inaccessible to us - and always will be.
> I'm always stressing to people at our star parties the light you see is history.
I'm surprised they still invite you. They probably already know.
Except, in our frame of reference, it's happening now, even though it happened then.
Which means in the future, we will would have seen this from before, but we won't have yet known if more stuff which will would have happened in the past will be happening in the present as the future unfolds.
So it is simultaneously not happening now, and happening now -- it isn't really happening now there, but here it is happening now, except it already happened there, and technically it has already happened here, but we're only now becoming aware of it now, but in the future, both will have happened in the past.
Which is why we stick with tenses which make sense to our poor little brains. it's just too damned hard to conjugate the verbs. ;-)
So, from what I've been able to tell -- we discuss it in the present tense, and then occasionally remind ourselves that we're seeing something which happened a long time ago. But then we try not to mix up the two, because it hurts more than an ice-cream headache.
Lost at C:>. Found at C.
THE question I am sure many will think about is how many neutrinos will be detected.
For supernova 1987a at 168'000 light years 24 neutrinos have been detected.
At 12 mega light years M82 is 71 times further, which dilutes the neutrinos by a factor ~5000.
So the answer is 0 neutrino if the detectors were the same as in 1987.
I doubt that the present detectors have improved by a factor 1000 in the meanwhile,
but I would be glad to be disproved.
Supernovas can affect the biospheres of planets within eight parsecs
Still, that's nothing compared to the hypothetical death tolls in active galaxies.
Since no information can travel faster than light, for all intents and purposes and discussions of causality it is happening right now. Since we are just entering its light cone, anything outside of it is inaccessible to us - and always will be.
Well, if you argue that, you have to give up concept of distance, or concept of speed of light. From our frame of reference, light traveled certain distance at certain speed, and simple calculation will tell how long time it took.
Or to put it another way, when you receive reflection of light you sent to a mirror, neither sending nor reflecting happened when you received the reflection back. It is in fact possible to determine distance of mirror by knowing how long ago sending and reflecting happened.