New Supernova Seen In Nearby Galaxy M82 125
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."
Re:It was on the rise... (Score:5, Informative)
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.
Neutrinos? (Score:5, Informative)
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.
Re:Neutrinos? (Score:2, Informative)
Re:Neutrinos? (Score:2, Informative)
It's a type Ia supernovae, which do not produce neutrios in large numbers. So even if it were at the same distance as 1987A (a type II SNe), we still woudn't expect to detect any.
Re:It was on the rise... (Score:4, Informative)
Except, in our frame of reference, it's happening now, even though it happened then.
Nope. In our frame of reference, it most definitely happened then. The light is reaching us now. It's too late to emit a beam of light of our own to meet the supernova light halfway, which it wouldn't be if it was happening now.
The only reference frame at this point in space in which it is happening now is that of the light which is reaching us.
Re:LOL ... (Score:4, Informative)
I always get a kick out of the title "The Local Group", which means stars in our relative vicinity, 12 ly or so. .
The Local Group is actually a collection of nearby galaxies, not stars. The closest member (not including the Milky Way) is 25k ly away...
Re:It was on the rise... (Score:5, Informative)
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.
Re:It was on the rise... (Score:4, Informative)
Over such distances the expansion of space is totally insignificant -- that's a large scale effect and is *only* active on large scales. Local structures are totally disconnected from it. (If the language doesn't sound intimidating, the expansion is a feature of the Robertson-Walker metric, which is assumed to be valid on very large scales. It is not a feature of Schwarzschild, Kerr, Lemaitre-Tolman-Bondi, Szekeres or other metrics that describe smaller structure, although it's true that you can find, say, an LTB that also has a cosmological constant. Since local structure will be described by something close to a Szekeres, it is not influenced by the "universal" expansion.) It's a bit like the universe is that old expanding rubber sheet, and local structures are pebbles rolling around on it. The pebbles aren't growing, even though the space between them is.
Extra points for anyone spotting an enormous logical flaw in this picture that is at the heart of one of cosmology's biggest (and unsolved) fundamental issues.