How do we really know what our galaxy looks like?

Question

How can we be 100% sure our universe is a "spiral" galaxy? We havent sent any type of satalite or shuttle even past our solar system, so how can we see a picture of our galaxy billions upon billions of miles away? I could understand how we can see other galaxies with the Hubble telescope, but how can we see our own within our galaxy?

Answer 1

They look at other galaxies and see what types are out there.  They only fall into several varieties.  

Once they know our galaxy must be like one of the few on offer they can do some calculations.  We can see towards the center of the Miky Way just fine.  When they estimate its size and what they know about what they can see they can figure which of the types fits with that.  And the answer is a Spiral Galaxy.

Answer 2

they have cameras in there

Answer 3

cause there are people smarter then we will ever be

Answer 4

What they do is, they observe other galaxies and the movements they have. They compare them to our Galaxy & then decide which type of Galexy our Galexy ressembles the most. And this is how they get a general idea of what our galexy looks like.=]

Answer 5

By advanced and tedious simulations.

Answer 6

Well, all science uses evidence to formulate theories and laws.  If one looks at the properties of our own galaxy from our vantage point, it can be discerned that it has a definite plane.  Thus eliminating other galaxy types (irregular, elliptical, barred spirals) thus leaving us with a Spiral galaxy.  However, that brings the possibilities down to  5 or 6 galaxy types, but all within the spiral class.  Additionally, one can discern definite rifts within that plane of stars, suggesting arms.  Larger rifts would lend to a barred spiral, however, the spaces between masses of stars are not so wide.

Another issue of describing the galaxy is a question of scale.  Sure we can discern the shape, but what is its size?

This was partially sorted out during the Great Debate between two astronomers in 1920.  (Shapley/Curtis)  Until that time, it was thought our galaxy was the Universe and the debate raged over the nature of "Spiral Nebulae".

I've included some excellent sources for this discussion.

Additionally, there ARE probes (not satellites as satellites only orbit larger bodies) that have left the solar system; five of them in fact:  Pioneer 10 and 11, Voyager 1 and 2, and New Horizons.  However, only three are still functioning. (the latter three).  With the exception of New Horizons, they are more or nearly 100 AU from Earth.  (An AU is the distance from Earth to the Sun)  Put in terms of light-time, Voyager 2 is nearly 12 hours and Voyager 1 is almost 15 light hours away!  That's a huge distance in human terms.

But, it'll still take a while for those probes to get to galactic borders.  Particularly depending on it's direction.  Even if it's taking the quickest route out of the galaxy proper, remember that the thickness of our galaxy, where our sun (and thus our solar system) lies is roughly 1000 light years thick.  If they were to go to the edge of the galactic disk it'd be closer to 20,000 light years.  Of course this is all very rough, not due to measurements mind you, but due to the undefined nature of a "galactic border".

Hope this helps.  Check the links below for a more in-depth explanation.

Answer 7

Mathematics.  Astronomers and scientists can deduce the overall shape and structure of our galaxy by observing the movements of planets and other celestial bodies, and then calculating the gravitational forces necessary to cause the patterns they have observed.

Answer 8

We look at other galaxies and try to compare the two, and we picture what ours look like at the same time.

Answer 9

they track as many stars as they see in a computer then the computer can change the view

Answer 10

We can look out from where we are and see where stars are (or at least where the density of stars are) and how far away they are and then plot them out in 3D and see what the shape of our galaxy is.

Think of what it would be like trying to draw yourself, if mirrors and cameras didn't exist. You can see your arms radiating out from your torso and your legs stretching below you. Plus you see what other people look like. You judge that your arms a little longer than average and your legs a little thinner than average and then you draw a picture of yourself even though you've never seen yourself from afar.

Answer 11

The same way you know what your house looks like from the inside.

Answer 12

First a small correction: our "universe" is not our galaxy. The universe is everything...well, everything *in* the universe including our galaxy.

We don't know precisely what the Milky Way looks like, but we can get a pretty accurate idea from careful observation of what we can see of it from our place inside. Because the spiral arms are well-defined and relatively easy to observe we can imply from those what the others should look like. We've also conducted a very good survey of our galaxies central core region with radiotelescopes. The relative movements of stars and the distribution of immense clouds of gas (...called 'nebulas'...) further add to our vision of the Milky Way.

Answer 13

the primary way we figured out that the milky way was a spiral galaxy and that it did indeed had spiral arms was through careful observation of the 21centimeter radiation emitted by neutral hydrogen that inhabit the galaxy.

it is assumed that denser regions of the Milky Way, or the spiral arms, if there were any, would naturally contain more mass than what wasn't the spiral arms.

by carefully measuring the redshifts, or velocities of the mass, the overall shape can be pieced together.

the biggest problem was interstellar dust.  it made it impossible to see into the plane of the galaxy through conventional telescopes.  however astronomers utilized the radio wavelengths, the 21 cm radiation, which shines through the dust and have thus pieced together a solid picture of the milky way in support of spiral arms.

for more information, a good book to read is "the alchemy of the heavens" by ken croswell.