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An array of questions.

  1. May 2, 2005 #1
    Hi some questions have been plaguing me when I look up at the sky.

    1) Does anything exist between galaxies? Are there any lonely stars, blackholes, rocks, planets,gas or anything between galaxies. Or do these things only form within galaxies?

    2) I know about blackholes, but I can't really be sure about how they look. I know they are coned shape from pictures I have seen, and that you can't actually see them, but you can see the effects around them, and the x-rays they emit. So if I were to stand infront of a black hole it would be the shape of a circle. If i stood on the side I would see a cone. If i stood behind it would I see a circle with a point in the middle? Are blackholes rips in NOTHING? Or is space actually a material?

    3) Are all the stars that I am looking at actually really there or is it possible that some of them are so far away that the star is dead but the light is still heading in my direction.

    4)How do astronomers take pictures of distant galaxies? From the vantage point on Earth towards the different galaxies wouldn't something get in the way of the shot? Like a star or a planet? If they could take pictures of things that far away how come we never see close ups of planets like really close as if I were to look at the ground right now.

    5)..coming soon

    THANKS!! please no flamming.
     
  2. jcsd
  3. May 2, 2005 #2

    turbo

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    There are things between galaxies, including materials that have been perturbed out of galaxies, and things that exist, but are not currently part of a galaxy.

    The cone shape you see, with the curved sides, is a diagram of the gravitational potential surrounding a black hole. It bears no resemblance to how a black hole might look to us in our universe, it is simply a mathematical representation of the gravitational force exhibited by the black hole.

    All the supernovae that we will see in the future are currently visible as normal stars, but many of them blew up MANY years ago (some of them exploded before the Earth condensed, BTW).

    Often when observational astonomers take pictures of distant galaxies, things get in the way. I have had airplanes, satellites, clouds, and aurorae spoil my shots of distant galaxies. These are problems. The chance of having a planet superimposed over a great shot of an intergalactic nebula or another galaxy would be too hard to resist. I would do everything in my power to capture it, although the problem of adequately imaging a faint galaxy or nebula while supressing the high luminosity of a bright planet like Jupiter would be daunting. Some Photoshop cut-and-paste would likely be required for the resultant image to have any aesthetic appeal.
     
  4. May 3, 2005 #3

    SpaceTiger

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    Turbo's answers are good, but let me add a few things...

    Pretty much everything you said above is true, even the last statement, which you probably thought was contradictory. :wink:

    Fact is, much of the stuff that sits between galaxies was actually inside one of the galaxies at some point in the past, but got ejected for one reason or another. However, all of it (except for some of the gas, which is left over from the big bang) was originally formed in the galaxies.

    For gas between galaxies, there are only a few atoms atom in a cube that's a foot on each side. We've never observed any planets outside of the galaxy (and probably won't for a very long time), but they are almost certainly there, having been ejected from various solar systems in the galaxies. The same would be true of black holes. As for stars, we have seen a few between galaxies, most notably in the form of planetary nebulae. I worked on a project to look for planetary nebulae (the result when a star dies) in between galaxies in the Leo cluster. We didn't find any, but there have been some found in Virgo and Fornax.


    A black hole with nothing else around it would be quite a sight to see. Why? Because when light passes through a strong gravitational field, it tends to bend. As a result, we can actually use massive objects as a sort of lens for light. We can simulate what it would be like to have something like a black hole sitting in front of us, say, when we're looking at a building. Here's an example:

    http://cfa-www.harvard.edu/castles/logo.jpg

    I'm not sure of the exact mass distribution that was used in that picture, but for a black hole, there would be a region in the center from which we couldn't see any light coming through. This is the "event horizon".

    In practice, though, most black holes are surrounded by "accretion disks" (matter falling into them), so the picture would not be so simple. In fact, you wouldn't want to get anywhere near it because the accretion disk would emitting very strongly in the X-rays.


    Turbo answered this pretty well. Pretty much all of the stars you see in the sky should still be around, even taking into account the delay in light. Light delays across the galaxy are on order of thousands of years, while even the shortest-lived star lives for millions.


    Space is very empty, so it's rare that other stars or planets get in the way. Traditionally, however, we do have a lot of problems with dust. In fact, from the ground, only our radio telescopes can see through all the dust that sits between us and the galactic center.


    There are in fact some very nice images of the planets. What are you looking for, exactly?
     
  5. May 3, 2005 #4

    Phobos

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    The key to telescopes is not magnification, but aperature (the amount of light collected). Distant objects like galaxies are faint, so it's more important to gather as much light as possible in order to get a clearer image. Magnification is important too, but (1) telescopes have a limited resolution power (how "close" you can make something appear) and (2) when you magnify an unclear image, it just becomes more unclear. Some objects in the sky (nearby galaxies, nebulae, star/galaxy clusters) appear in the sky bigger than the Moon does, but they're too faint to see without a telescope (much bigger aperature than the pupil of your eye).

    In short, those images of far-away galaxies are not as magnified as you might think. So, being able to see a distant galaxy clearly does not mean we can zoom in on a pebble on Mars.

    The planets may be a lot closer, but a good sized galaxy is a million-million times bigger.

    Astronomers often gather as much light as possible from the distant (deep space) object and then magnify just enough to bring out sufficient detail.

    As SpaceTiger noted, we do have some good images of planets in our solar system. From Earth, our best resolution on Mars is something like 17 miles (one pixel in the image represents 17 miles on Mars). In order to get images with resolutions in the 10's or 100's of meters, you'll need to put a satellite around that planet. For an up-close, ground-level view, you'll need a lander (as you probably know, there are a couple rovers on Mars right now and there was a recent lander on Saturn's moon Titan).
     
  6. May 3, 2005 #5

    Phobos

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    Yes, in photos of distant galaxies, it's not uncommon to see a huge bright star by it (which is a star in the foreground from our own galaxy). But space is vast and largely empty, so many clear views are available.

    But note that many deep space photos are pointed out of the plane of our galaxy (remember our galaxy is disk-shaped). We can't really see through the plane of our galaxy to get photos of other galaxies in that direction because the contents of our galaxy get in the way.

    Don't worry. We don't allow flaming here at PF. Welcome!
     
  7. May 3, 2005 #6
    Thank you everyone for the great responses!

    I really liked the pictures of Mars. At the south poler cap I take it that is the ice I hear about so often.

    That light distortion picture is a really cool concept aswell.

    It's not that I am looking for anything-I wouldn't know where to start. I was just wondering if taking really close shots of a planet were possible. Somewhat like earth-viewer. (I don't know the official name) Phobos gave me a good explanation.

    Let me see if I can conjure up another question...Oh I have some questions about wormholes. Do they have the same characteristics as a blackhole? How are they formed? Are they only theoretical? Do they have an immense gravitational field?
     
  8. May 3, 2005 #7

    turbo

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    We are spoiled by our technology. We have Earth-orbiting satellites that can give us very detailed pictures of our planet. The best pictures are classified, and will be until our intelligence agencies have access to OOM better images, or perhaps even better. In the '70s, earth-orbiting satellites could distinguish between male and female Soviet factory workers based on whether the person walking to the plant was wearing a bright-colored babushka on their head. Let me caution you that lest you think this is whiz-bang stuff, the NSA would probably not have allowed the release of that kind of information to a college level photogrammetry class at the height of the cold war unless they already had access to MUCH better imagery. Hubble is not the only highly-capable telescope in Earth orbit - it just happens to be targeted at objects of interest to astronomers and it has detector packages appropriate to the tasks.

    We cannot get equivalent high-rez views of other Sol-orbiting planets unless we are willing to launch huge telescope platforms to them, and that's not in the budget. There are lots of compact, low-mass, experiments that are vying for space on planetary platforms, and they can give us valuable information about these planets without the massive mirrors, power supplies, etc needed to support a project like HST.
     
  9. May 3, 2005 #8

    SpaceTiger

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    Some of my thoughts on the issue. There are a lot of discussions on this in Dr. Michio Kaku's Forum as well.
     
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