Could we see galaxies while in a spaceship?
- Thread starter FPAlpha
- Start date
That doesn't make any sense to me at all. I'm not asking to see blinding light like a 100 watt light bulb right in my face. I'm talking about seeing a swirly spiral of the galaxy. No matter how far the stars are, they still give of light which travels at light speed. If you are in a spot right outside of the galaxy, that light would reach you. Some light, released 1000s of years ago would reach you at the same time as other light released only 100's of years ago. That and the dust would make everything look blurry, but you could see it no question about that.
On a good day, in a good position, you can see Andromeda Galaxy over 2 billion light years away with a naked eye. The fact that you can't see Milky Way clearly is due to light pollution. Milky Way, of course, got the name because Romans saw it with a naked eye on a clear night.
I'm going to agree with you on this one. One question I do have, though, is would the galactic center be noticeably brighter than the spirals?
That picture you posted can still be seen in plenty places on Earth. It's still not anything like the whole galaxy and you might be able to see Andromeda but all you can see is a spot of light. Just because you like the idea of looking at a whole galaxy from outside doesn't mean it's possible.
But light gets dimmer as the inverse square of the distance, because it's spreading out spherically from the source and a smaller fraction of it is going to reach your eyes the farther away from it you are. If you're ten times as far away, it'll be a hundred times as dim. If you're a thousand times far away, it'll be a million times as dim. There's a reason why we need telescopes and long-exposure cameras to get those bright, clear pictures of galaxies.
If you were just 72 light-years away from our Solar System, the Sun would become invisible to the naked eye, unless you had really acute vision. That's how quickly a star can dim below visibility.
Yes, but only faintly. Its apparent magnitude is 3.44 -- less than a quarter as bright as Mars. That's pretty dim.
Remember, I haven't been saying the Milky Way would be completely invisible. I've been saying that it would be a nebulous gray blur rather than some brilliant, vivid, multicolored thing like in the astronomical photos and the TV/movie images based on them. You'd see something, but you wouldn't see that.
But even without light pollution, it's still fairly faint compared to the stars. That photo you include in your post is clearly a long exposure, since the clouds and hills are blurred (meaning the camera tracked the stars and moved relative to the landscape) and that brightest star in the center is a washed-out blob rather than a pinpoint. To the naked eye of the person who took that picture, relying only on instantaneous light intake rather than a cumulative exposure, the Milky Way would've looked dimmer. They could see it, obviously, but it wouldn't look that bright or colorful.
So if we were to be perpendicular to the Milky Way, we wouldn't see the Milky Way like we see it in the artist renderings and illustrations?
So we wouldn't see something like this?
Not with the naked eye, no. As I said above, astronomical pictures like that are created by taking long exposures with sensitive telescopes, and generally by artificially enhancing the images with false or exaggerated colors. Open that image in an editing program, dial down the brightness, contrast, and color saturation considerably, and then you'll approach what the unassisted human eye could probably make out.
Yep, exactly, and to add to what Christopher said, many of those pictures are often altered or enhanced in certain ways. For example, I have a program that will stack a series of images and combine them to extrapolate the data in them into one image that has all the data. So, in effect they're composites of many images stacked one on top of each other. The detail gets better the more frames one stacks up. You'd never get a view of a galaxy as good as that, even with the best telescope in the world without software enhancement. In fact, that picture looks like some CGI might have been added to give it some depth between the spirals. Kind of looks 3Dish.
Oh and Christopher, you should come up north some time. The dark skies are beautiful and we can see the Milky Way quite well with the naked eye. For a good example of what one can see with the naked eye, one can check out my astrophotography thread. But yes, that is one very long exposure, and most likely is stacked as well.
Last edited:
Also, when we look at the Milky Way, we're seeing the Central Bulge of the galaxy from a distance of roughly 20,000 light-years or so and the rest of the visible stars from a closer distance. In order to be far enough away to see the entire disk of the galaxy in your field of view -- say it subtends, oh, 90 degrees so that it can pretty much all be considered "in front" of you rather than extending into your peripheral vision -- you'd have to be at least 50,000 light-years from it, so it would appear (2.5)^1/2 = about 1/6 as bright. And in order to get a good, clear view of the whole thing, say, subtending about the width of your computer monitor in front of you -- say maybe 45 degrees -- you'd need to be 120,000 light-years away, or 6 times as far, so the disk of the galaxy would be 1/36 as bright to the naked eye as the Milky Way is in Earth's sky.
Well, that's more or less to scale, but of course it's simulated, a black-and-white photo of the Moon cropped and pasted onto a much longer color exposure of M31. The apparent magnitude of the full Moon is nearly 3 million times that of M31.
Similar threads
