APOD: Milky Way Galaxy Doomed: Collision... (2012 Jun 04)

[ta152h0]

just imagine the Andromedians arriving here and this is the first thing they run into

http://www.youtube.com/watch?v=hM4z6B4I1iw

[GaryP]

The artist's rendition is nice, but how about a computer simulation, or the output of one? (Almost said "an actual computer simulation".)

Couldn't figure out that gateway question "What is the asterisk about?". What is one supposed to reply? "Starship" and "astronomy" both failed as containing too few characters. Oh, was there a footnote? Precious!

[ta152h0]

These things are spinning every which way. Guess the original ( Big Bang ) kick was not a synchronized swimming event ? Proves a singularity cannot be assigned rotation. Maybe I will skip the ice cold one tonight.

[SJoe]

The artist's rendition is nice, but how about a computer simulation, or the output of one? (Almost said "an actual computer simulation".)

Try this one..

http://www.youtube.com/watch?v=7HF5Oy8IMoM

[Seantos]

Beautiful. Inspired me to use my own images:

[nstahl]

Obviously a great APOD. A neat image, even if imagined, and it's stirred up a lot of interest in the science.

[scr33d]

I always find such artist-imagined event a little bogus. They almost always never depict correct surface brightness of extended objects: closer objects do not necessary imply brighter objects (except for point sources).
Unless the artists are saying that in 5 Gyr our descendents have 1000 x more sensitive (and multi-band?) eyes.

[Chris Peterson]

I always find such artist-imagined event a little bogus. They almost always never depict correct surface brightness of extended objects: closer objects do not necessary imply brighter objects (except for point sources).
Unless the artists are saying that in 5 Gyr our descendents have 1000 x more sensitive (and multi-band?) eyes.

Yeah, but I guess they figure that an image of what it will really look like- a sort of "Y" shaped Milky Way- would not make an interesting image. But the rendering is reasonable for what you'd see if you made a 30-second exposure with an ordinary camera (and to see this visually, you'd only need a factor of ten or so increase in sensitivity, and no broader wavelength sensitivity than we already have).

[Winky]

The artist's rendition is nice, but how about a computer simulation, or the output of one? (Almost said "an actual computer simulation".)

Try this one..

http://www.youtube.com/watch?v=7HF5Oy8IMoM

And this one => http://www.youtube.com/watch?v=PrIk6dKcdoU
and here's a fun place to play with galaxy collisions => http://burro.cwru.edu/JavaLab/GalCrashWeb/main.html

[scr33d]

I always find such artist-imagined event a little bogus. They almost always never depict correct surface brightness of extended objects: closer objects do not necessary imply brighter objects (except for point sources).
Unless the artists are saying that in 5 Gyr our descendents have 1000 x more sensitive (and multi-band?) eyes.

Yeah, but I guess they figure that an image of what it will really look like- a sort of "Y" shaped Milky Way- would not make an interesting image. But the rendering is reasonable for what you'd see if you made a 30-second exposure with an ordinary camera (and to see this visually, you'd only need a factor of ten or so increase in sensitivity, and no broader wavelength sensitivity than we already have).

Yes, I remember from a comment that Feynman made (he was lecturing on photo multiplier) that our eyes need only ~10x more sensitivity inorder to see individual photons.

[Chris Peterson]

Yes, I remember from a comment that Feynman made (he was lecturing on photo multiplier) that our eyes need only ~10x more sensitivity in order to see individual photons.

The quantum efficiency of the eye is around 10%, and under the right conditions we can detect single photons. In most cases, it takes about 20 photons to illicit a response- a mechanism that apparently exists to reduce the effects of thermal noise in the retina.

Actually, sensitivity isn't what matters. Our eyes and typical consumer cameras have similar sensitivity. The difference is that a camera can integrate- collect photons for a long time- whereas the human eye can't. Astronomical cameras approach perfect sensitivity, but cannot produce an image of a dim object without hours of exposure. It doesn't matter if you can detect every photon if there are hardly any photons to begin with.

If we want our distant descendents to see the night sky as it appears in images, we'll need to evolve eyes that can integrate... and heads that can stay very steady for hours on end!

[scr33d]

I see your points. So to not duplicate what a camera does (no integration) but just to see the world with increase eye sensitive, I could think of images from light-amplification scopes? Or do those scopes not response logarithmically and thereby not give an equivalent (super eyes) experience?

[Chris Peterson]

I see your points. So to not duplicate what a camera does (no integration) but just to see the world with increase eye sensitive, I could think of images from light-amplification scopes? Or do those scopes not response logarithmically and thereby not give an equivalent (super eyes) experience?

Right, what you see in a night vision scope is pretty much what you'd see if you could use every photon collected. The intrinsic noise in an image (or at some point in an image) is equal to the square root of the number of photons collected. That's why short exposure images are noisy, and it's why the view through a night vision scope is noisy. With a small number of photons, the signal-to-noise ratio is inherently low... and no technology can every change that.

[scr33d]

I see your points. So to not duplicate what a camera does (no integration) but just to see the world with increase eye sensitive, I could think of images from light-amplification scopes? Or do those scopes not response logarithmically and thereby not give an equivalent (super eyes) experience?

Right, what you see in a night vision scope is pretty much what you'd see if you could use every photon collected. The intrinsic noise in an image (or at some point in an image) is equal to the square root of the number of photons collected. That's why short exposure images are noisy, and it's why the view through a night vision scope is noisy. With a small number of photons, the signal-to-noise ratio is inherently low... and no technology can every change that.

Okay, but I was concern with the high photon count end also. I mean you could deal with the low count end (noise) by cooling, but we see a large dynamic range because the eyes response in log scale--which I don't think night vision scopes do. I mean this limitation is apparent in lots of (linearly) integrated images: M31's core, for example, is washed out in images that show its spiral. I am conjecturing that with a human eye that is >10x more sensitive and has log response, the seeing experience would have no easy analogy--it certainly would not be like looking through night vision goggles nor looking at 30 min exposures of M31.

[ta152h0]

I was thinking here something that is so far away right now and only spans a fraction of its distance, we can assume for all practical purposes this thing looks like a beautiful spiral. But as it gets closer, the fact that light from the far side maybe 120000 ly older than the light approaching from the nearest end, would this thing appear distorted, perhaps " bent ", in real time ?

[ThePiper]

I see your points. So to not duplicate what a camera does (no integration) but just to see the world with increase eye sensitive, I could think of images from light-amplification scopes? Or do those scopes not response logarithmically and thereby not give an equivalent (super eyes) experience?

Right, what you see in a night vision scope is pretty much what you'd see if you could use every photon collected. The intrinsic noise in an image (or at some point in an image) is equal to the square root of the number of photons collected. That's why short exposure images are noisy, and it's why the view through a night vision scope is noisy. With a small number of photons, the signal-to-noise ratio is inherently low... and no technology can every change that.

This is a highly interesting alongside discussion. Thanks Chris and scr33d!

[ta152h0]

That is why I keep coming back to this apod