Questions about the local Galaxy

[Kyriakos]

I have some questions, mostly about what is viewed of our own galaxy (termed in English 'the milky way') from earth.

1) Where in this Galaxy is our solar system? (in regards to the full spiral of it, and moreso regarding the 'arm' formations in that part).

2) I read that our own Galaxy is a Barred Spiral. Wiki gives me the info that this mostly means that the Galaxy has in its center a bar-like formation of closely placed stars. What does this mean in regards to the absolute core of the Galaxy? (ie in relation to the theory that its core is a supermassive black hole). Image of the types of galaxies follows in the spoiler, from wiki.

Spoiler Alert, click show to read: 

3) How much of our own Galaxy spiral is visible from any point on our planet?

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The reason i got interested is due to it being relatively nice to know some basic stuff about the local Galaxy as i plan to briefly refer in the next seminar on Democritos and his views (he was mainly an astronomer), one of which was that the Galaxy was a collection of closely placed stars (it seems that before him, that view in the sky was thought of being something other than star collections). His concurrent, Anaxagoras, is notable for first arguing that stars are 'massive fiery cores' which are very distant from the earth (so we are not burned by their heat), although he appears to have thought they were themselves smaller than the entire earth.

[Sphere]

The sun is about here in the milky way...




Unfortunately we can't get a view from outside our own galaxy so we have to extrapolate what it might look like. It is assumed to be a barred spiral, it is assumed to have a super-massive black hole at its center.

[plantagenet_king]

Yeah this is the Answer I would also give, we need to get out there really to see it in its full splendour

[Kyriakos]

Thank you, Sphere

And what about my main question, the one about how much of the Galaxy is visible from our planet? (and which part of it, too. Just some basic info).

[Visna]

Thank you, Sphere

And what about my main question, the one about how much of the Galaxy is visible from our planet? (and which part of it, too. Just some basic info).

Do you mean visible to the naked eye from a given point on earth? Because that's no more than, dunno, a few thousand or something.

[Sphere]

Thank you, Sphere

And what about my main question, the one about how much of the Galaxy is visible from our planet? (and which part of it, too. Just some basic info).

I guess I do not quite understand the question. All of the galaxy is more or less visible to us, it is just that from Earth we can only get a view looking through it. This is what the center of our galaxy looks like to us.

[Magister Militum Flavius Aetius]

And you can't really even see that anymore unless you manage to find a place where the light pollution is really low, like out in the cornfields of Nebraska or something.

[visser300]

Do we really can see that? I thought those kind of pictures are edited with photoshop or sth.

[Aulus]

Do we really can see that? I thought those kind of pictures are edited with photoshop or sth.

It really depends on your location. If there is very little light pollution and the Moon isn't reflecting too much light, then it is entirely possible to see the Milky Way. Perhaps not as brightly as that picture, but enough to see the rough shape of the dust clouds and the band.

I know the Ancient Greeks factored the Milky Way into their mythology, thus it most certainly is possible to see it without modern technology (otherwise they wouldn't have known about it to make a story about it!)

[Wulfburk]

I think on places like the atacama desert on Chile, where the sky is basically 100% clear, and there aint that much light pollution, you'll be able to see something close to that pic.

[saxdude]

Do we really can see that? I thought those kind of pictures are edited with photoshop or sth.

Mesoamerican cultures associated the arm of the spiral with the celestial serpent, the milky way is very present in their cosmology and mythos.
I guess people underestimate how much light polution has actually blocked out the night sky, the milky way has always been present in preindustrial cultures.

[Magister Militum Flavius Aetius]

Yeah, it's sad. You have to go way out into the ocean, or on an obscure mountain top like the Andes or Himalayas to see these kinds of images anymore.

[saxdude]

You could also go to the atacama.

[Kyriakos]

But is the spiral visible with the human eye?

Also (granted, i don't know almost at all about the galaxy in this subject) doesn't the exact position of our planet disable us to see some parts of the overall shape of the galaxy already? (i tried to visualise it as someone being in a spot in a spiral, looking inwards or outwards, but likely this is not how this parallels to).

[Aru]

But is the spiral visible with the human eye?

No, we can't see the shape of the galaxy since we are in it. Try seeing a left sleeve or general shape of shirt if you're looking from right sleeve. You can't.

Also human eyesight can recognize only few galactic forms by naked eye in perfect conditions. Mainly galactic center (the stripe of stars brighter than other starts - the "milky way". But not what lies behind it, for instance. Just like you can't see the other side of the Moon.

[Aulus]

But is the spiral visible with the human eye?

Also (granted, i don't know almost at all about the galaxy in this subject) doesn't the exact position of our planet disable us to see some parts of the overall shape of the galaxy already? (i tried to visualise it as someone being in a spot in a spiral, looking inwards or outwards, but likely this is not how this parallels to).

The spiral itself is not visible to us, because much as Aru said, we are in it. It's like looking at your roof from above when you are inside your house - impossible with your own eyes, and we do not yet possess technology that can do this for us.

We know our galaxy is a spiral galaxy because of what we can see. We see a long horizontal band, with a discernible, albeit somewhat small, bulge in the center. Based on the other galaxies that we can much more easily observe, it is the presence of this bulge in the center that indicates we live in a spiral galaxy, rather than an elliptical one. There was also a study done a few years back that provides compelling evidence that the Milky Way has a bar: http://www.newscientist.com/article/...l#.U4l17vldXO4

Due to our location, yes, there are parts of the galaxy we can't see. Thankfully with various telescopes looking at different wavelengths of light, we are better able to penetrate the dust and gas clouds that one finds in our galaxy, but even that can only go so far. We are closer to the edge of the spiral than the center, so looking across the spiral arm we are in, through the bulge, and towards the opposite arm and trying to discern one star from another and its distance from us is no easy feat. Here are some good 360 degree images that can help visualize what we can see (the center is the bulge, while the left and right would wrap around to show what is directly behind us): http://mwmw.gsfc.nasa.gov/mmw_sci.html#maps

However, everything you can see with your eyes belongs to the Milky Way. It doesn't tell you anything about the other side of the center, for sure, but it's not hard to extrapolate and imagine that it's pretty darn similar to our side.

[saxdude]

I meant the band of the spiral, rather than the spiral itself.