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It's called "The Milky Way" because if you don't know what you're looking at, it looks like a hazy, nebulous path across the sky.
But try this : go down to Chile, or somewhere else in the Southern Hemisphere. Go outside at a nice, dark site, and stay out there so your eyes adapt. If the galaxy is passing overhead, you will see something like this:
This is a picture taken by an all-sky cloud monitor camera at the Cerro-Tololo Inter-American Observatory. Around the edge of the picture is the horizon; you can see the silhouettes of the telescope domes. And, directly overhead, is the big and impressive edge-on spiral galaxy that we are inside. The "Milky Way," with a telescope, resolves to lots and lots and lots of stars. You can see the bulge near the center. The contours are irregular, because the disk of the galaxy is filled with dust clouds, some of whicih are closer to us, some of which are farther from us. All of the stars in this picture are in the Milky Way; they're just the closest ones, that look spread out on the sky to us because we're embedded in the disk.
It's a very impressive sight. I strongly recommend that everybody in the Northern Hemisphere find a way, sometime in their life, to get down to the Southern Hemisphere sometime in the fall when they can see this. And if you're already in the Southern Hemisphere, and haven't seen this-- get to it!
Comments
... I am speechless. This fills me with reverent awe.
Posted by: Melissa G | March 10, 2007 12:27 PM
This reminds me of a picture taken of the same observatory, it was the APOD a few years back (it came back for an encore a little while ago), and it has stuck with me as one of my favorite astronomy pictures of all time
http://antwrp.gsfc.nasa.gov/apod/ap040313.html
Posted by: Ryan Vilim | March 10, 2007 12:33 PM
Cool picture. But how can you claim that all the stars in the shot are in the Milky Way?
Posted by: Dwigth | March 10, 2007 12:57 PM
I'm confused. How can we see the galaxy that we are in?
Posted by: Gabe | March 10, 2007 1:06 PM
Gabe: "I'm confused. How can we see the galaxy that we are in?"
Consider this:
"I'm confused. How can we see the Earth that we are standing on?"
Consider that we can see some, but not all...
The harder question is:
"What would the Milky Way galaxy look like to an observer far far away?"
The answer involves the fact that what I was taught when I took Astrophysics at Caltech is no longer believed. Key words: "Barred Spiral."
Posted by: Jonathan Vos Post | March 10, 2007 2:09 PM
Which "fall": fall in Chile, or in the Northern hemisphere?
I should know, since I'm Chilean, but I never noticed, and can't check now because I'm in Europe :-(
Not that I didn't pay attention to the Via Lactea, of course, it's truly a gorgeous view. But Orion and Scorpio were always my season markers.
BTW, when any of you go there, don't forget to check Magellan's clouds.
Posted by: dileffante | March 10, 2007 2:43 PM
*sigh* You're right, everyone should go south and look up at least once in their lives. And I too was wondering about all of the stars being in our galaxy, the Magellanic Clouds gotta be in there somewhere.
Posted by: arby | March 10, 2007 3:56 PM
Even in the Northern Hemisphere, just going somewhere with a truly dark sky is hell of amazing for a city-dweller. It becomes hard to find the constellations you're used to because there are just SO SO MANY STARS.
Posted by: Amali | March 10, 2007 4:38 PM
The only stars we can see that aren't in the Milky Way are in galaxies outside the Milky Way. There are some galaxies (the Magellanic Clouds, M31 in Andromeda, maybe one or two others) that are bright enough to appear in an image like this. Unfortunately none of them were visible at the time of this image. Even if they were visible, those galaxies would look like little fuzzy patches, without any distinct stars. In short, anything that looks like a star in this image is a star inside the Milky Way.
Posted by: ColoRambler | March 10, 2007 9:42 PM
This appears to be a picture from the Southern Spring. The pointers and the southern cross are at the top, and the megellanic clouds are hidden behind the dome at the top of the picture. Just to the left of the galactic center in this shot is Scorpio, which currenly rises after midnight.
Posted by: Lab Lemming | March 11, 2007 6:49 AM
Nice, but you don't explain why people in the northern hemisphere don't see this. I live in the south and am very familiar with the view.
Posted by: graeme | March 11, 2007 10:06 AM
Sorry -- Southern Spring! Northern fall. My northocentrism was rearing its ugly head there.
We can see the galaxy we're inside because galaxies aren't solid. They're mostly empty space (well, filled with dark matter and tenuous gas, but you can't see that). Close to the plane of the galaxy there's lots of dust clouds, which is why a lot of the galaxy is blotted out from our point of view. All the stars around us are within the disk; we look through and past them towards the collection of stars that make up the disk, and actually look like a thin band as we add up the many stars that are all thousands of light-years away and closer to the Galactic center.
Re: why people in the Northern Hemisphere don't see this : they can see the Milky Way passing overhead, but not with the center of the galaxy directly overhead. The center of the Galaxy is in the constellation Sagittarius, which is far in the Southern Sky. At my latitude (about 36 north), Sagittarius passes fairly low in the Southern sky when it's up. At CTIO, it passes nearly directly overhead, and hence the view we see here with the galaxy in its full glory centered over the night sky.
Without a telescope, you can't pick out individual stars in any other galaxy. As ColoRambler mentioned, there are a few galaxies that can be seen with the naked eye (the two Magellanic Clouds, the Andromeda Galaxy; I've heard some claim others, but I'm dubious), but they look like fuzz patches, not like collections of individual stars. You can only see them because of the combined light of lots and lots of stars. Any star that you can see with your naked eye is not only in the Milky Way, but in the very local regions of our own Galaxy.
(One exception: when supernova 1987A in the LMC exploded, people in the Southern Hemisphere could see that as an individual star for a little while.)
Posted by: Rob Knop | March 11, 2007 10:47 AM
It's possible to see a couple of other galaxies with the naked eye, but it's quite difficult. You need an absolutely dark sky and exceptional transparency. I've seen M33 as a faint fuzzy blob from the middle of Nebraska after a spring cold front, but I've never been able to pick it out from anywhere in California, including some fairly dark sites.
Oh, and this is still a stunning photo. Anyone who doesn't see a similarity with pictures of other edge on spiral galaxies is either really dense or a True Believer.
Thanks for sharing!
Posted by: David Williamson | March 12, 2007 1:47 AM
Jonathan Vos Post said: "What would the Milky Way galaxy look like to an observer far far away?"
Is it possible to measure the distance to many many stars in the Milky Way and draw a 3D map that would probably reveal its rough shape as seen from afar?
Posted by: Filip | March 12, 2007 5:42 AM
Out here in Western Washington (state), standing in my yard at night I can discern the cloud of the galactic axis. It's not anywhere clear and crisp like the photo, but I can see it.
Posted by: Jeff | March 12, 2007 12:06 PM
Jonathan Vos Post said: "What would the Milky Way galaxy look like to an observer far far away?"
NGC 891. It'll be one of my Friday Galaxy Blogging targets in the future :)
Posted by: Rob Knop | March 13, 2007 1:00 AM