General guestions 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 :

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

*

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.

 

[Cheetah]

1)

The Sun is near the inner rim of the Galaxy's Orion Arm, within the Local Fluff of the Local Bubble, and in the Gould Belt, at a distance of 8.33 ± 0.35 kiloparsecs (27,200 ± 1,100 ly) from the Galactic Center. The Sun is currently 5–30 parsecs (16–98 ly) from the central plane of the Galactic disk. The distance between the local arm and the next arm out, the Perseus Arm, is about 2,000 parsecs (6,500 ly).

http://en.wikipedia.org/wiki/Milky_Way#Sun.E2.80.99s_location_and_neighborhood

2)

Bars are thought to be a temporary phenomenon in the life of spiral galaxies, the bar structure decaying over time, transforming the galaxy from a barred spiral to a "regular" spiral pattern.

http://en.wikipedia.org/wiki/Barred_spiral_galaxy

So it seems that the bars simply exist for a while, and they don't necessarily have any effect on the galactic black hole...

3)

Of the 5,000 to 8,000 stars in the Milky Way visible to the human eye from Earth, one can usually only see about 2,500 at a time. In fact, the few thousand stars we can see of the Milky Way with our naked eye are only about 0.000003% of the 200-400 billion stars that inhabit the spiral!

http://www.universetoday.com/23173/the-milky-way-from-earth/

 

[Ziggy Stardust]

Milky way as seen from Earth

"The bright patch to the left of the image marks the bulge of stars at the heart of our Galaxy."

 

[Kyriakos]

Thank you

Some more elaboration is needed for the third question:

-Of the very tiny percentage of stars (and the full spiral) of our Galaxy we see from the earth, what is the exact direction (if set, or if practically stable in its periodic change to allow for an easy answer) of our own Galaxy we get to observe with a telescope?

Ie do we see more than just the bit of the arm or the spiral turn we are also tied to? Or do we just see a tiny part of the arm? And to which direction? (thanks, sorry for the basic questions, but i know next to nothing about galaxy telescopic examination).

(also, building on Ziggy's post: do we see an outer part of the closer spiral parts (arms) to the bar and the center of our galaxy, and infer the form of it as barred spiral due to the arrangement of the more densely packed areas in that view in the sky?).

 

[Glassfan]

Friend, download Stellarium.org.