>> Aren't we *in* the Milky Way?
> 
> Yes, and it's quite a flat disc, so looking out from Earth along the 
> plane of the disc you see a lot more stars than looking out 
> perpendicular to it, this looks like a brighter band going across the sky.

I will admit I don't know much about the geometry of our galaxy, but I 
was under the impression that the disk is hundreds of billions of light 
years "thick", it's just that it's quadrillions of light years across as 
well. The point being, the disk is many million stars thick, and so we 
should see them in just about every direction we look.

>>> BTW if you're interested, one of the brightest "stars" in the sky at 
>>> the moment is actually Jupiter.
>>
>> Any ideas what the visual angle for that is? ;-)
> 
> Wikipedia tells me the radius is 71500 km, Stellarium tells me it's 
> 5.224 AU away from us, so googling "2*71500 km / 5.224 AU in degrees" 
> gives 0.01 degrees.

So... about 36 seconds of arc. Man, that's pretty small.

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"scott" <sco### [at] scottcom> wrote:
> > Aren't we *in* the Milky Way?
>
> Yes, and it's quite a flat disc, so looking out from Earth along the plane
> of the disc you see a lot more stars than looking out perpendicular to it,
> this looks like a brighter band going across the sky.

This is a pretty awesome photo of the whole thing:

http://en.wikipedia.org/wiki/File:Deathvalleysky_nps_big.jpg

Not exactly what you'd see with the naked eye but it gives you the idea.

> >> BTW if you're interested, one of the brightest "stars" in the sky at the
> >> moment is actually Jupiter.
> >
> > Any ideas what the visual angle for that is? ;-)
>
> Wikipedia tells me the radius is 71500 km, Stellarium tells me it's 5.224 AU
> away from us, so googling "2*71500 km / 5.224 AU in degrees" gives 0.01
> degrees.

Jupiter and Saturn are particularly easy to pick out, because they're big enough
to be actual discs rather than points like regular stars. And if you can hold
binoculars steady enough you'll just about see Saturn's rings.

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Bill Pragnell wrote:

> This is a pretty awesome photo of the whole thing:
> 
> http://en.wikipedia.org/wiki/File:Deathvalleysky_nps_big.jpg
> 
> Not exactly what you'd see with the naked eye but it gives you the idea.

This is awesomer:

http://en.wikipedia.org/wiki/File:Perseid_Meteor.jpg

Here in the name of God does the night sky actually look like this?!

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> I will admit I don't know much about the geometry of our galaxy, but I was 
> under the impression that the disk is hundreds of billions of light years 
> "thick",

It's much smaller than you think:

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

> So... about 36 seconds of arc. Man, that's pretty small.

It's still one of the very few objects in the sky that allows you to 
actually see its shape with a good pair of binoculars or a small telescope 
though.

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>> I will admit I don't know much about the geometry of our galaxy, but I 
>> was under the impression that the disk is hundreds of billions of 
>> light years "thick",
> 
> It's much smaller than you think:
> 
> http://en.wikipedia.org/wiki/Milky_way

Heh, "only" 100,000 light years across and 1,000 light years thick. 
Well, that's the trouble when you start dealing with Really Huge 
Numbers, see?

There's a reason why would talk about 4 Terabytes rather than 
4,000,000,000,000 bytes - it's frighteningly easy to get the number of 
digits wrong! ;-)

Obligatory XKCD:

http://xkcd.com/558/

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> This is a pretty awesome photo of the whole thing:
>
> http://en.wikipedia.org/wiki/File:Deathvalleysky_nps_big.jpg
>
> Not exactly what you'd see with the naked eye but it gives you the idea.

I always wonder how they get these type of photos.

I mean this must be a pretty long exposure to get that detail?  But since 
the Earth is rotating, either the ground or the sky is going to get motion 
blurred.  Is this a photoshop of two images, or can they really get a photo 
like that in one shot?

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Invisible <voi### [at] devnull> wrote:
> This is awesomer:
>
> http://en.wikipedia.org/wiki/File:Perseid_Meteor.jpg
>
> Here in the name of God does the night sky actually look like this?!

Well, that's an even longer exposure than the one I posted (you can tell by the
way the stars are slightly elongated), so no, that's not exactly what you'd see
by eye either. But similar!

A shame there's only one meteor visible there, I was expecting more...

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"scott" <sco### [at] scottcom> wrote:
> > I will admit I don't know much about the geometry of our galaxy, but I was
> > under the impression that the disk is hundreds of billions of light years
> > "thick",
>
> It's much smaller than you think:
>
> http://en.wikipedia.org/wiki/Milky_way

I always remember galactic vital statistics by knowing all the lyrics to this:

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

:-)

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> I always remember galactic vital statistics by knowing all the lyrics to this:
> 
> http://en.wikipedia.org/wiki/Galaxy_song
> 
> :-)

Is that something like the song about the table of elements?

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"scott" <sco### [at] scottcom> wrote:
> > This is a pretty awesome photo of the whole thing:
> >
> > http://en.wikipedia.org/wiki/File:Deathvalleysky_nps_big.jpg
> >
> > Not exactly what you'd see with the naked eye but it gives you the idea.
>
> I always wonder how they get these type of photos.
>
> I mean this must be a pretty long exposure to get that detail?  But since
> the Earth is rotating, either the ground or the sky is going to get motion
> blurred.  Is this a photoshop of two images, or can they really get a photo
> like that in one shot?

I'm not sure. The fact that it's a nearly-complete panorama makes it even more
complicated - I guess it must have been unwrapped from a fisheye.

I'd think it was a single shot. I bet you could get away with up to a minute of
exposure, and it's very wide angle so any movement would be less noticeable.

Any expert photographers here want to comment?

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