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O.k. i selelcted this photo off the internet of someone snapping a photo of one of the milky way spiral arms in the night sky and so my question is ..... was the photo possibly a time released shot as i thought that we can't see any of the spiral arms with our naked eye correct?
Yes, it is a photograph with long exposure and a decent GEM (German Equatorial Mount). You will notice that none of the stars are blurred, only the trees.
You are indeed looking toward the galactic center and that band of dust and cloud is the Sagittarius Arm. We are actually between two spiral arms, the Sagittarius Arm and the Perseus Arm, known as the "local spur."
In our rotation around the galaxy, our solar system will pass through the Perseus, Scutum-Crux, and Sagittarius Arms.
Well said, and you're quite right. Since the structure of the galaxy is somewhat of a flat disk, and we're in the disk, we're unable to directly see the arms because we're also in the disk. Part of the mappng process and the determination of spiraled arms has been based on observing areas and alignment of stars more densely grouped in comparison to areas less dense which hels define the arms. We've also been able to take that information and compare it with other galaxies we can see which helps us better visualize what our galaxy looks like. It was only until very recently that the core of the galaxy is not only bulges out from the galactic plane, but that it looks like it's a barred-spiral galaxy rather than a true spiral.
Until, not so long ago, we could guess, but had no real idea what the center of the galaxy looked like because of all dust and gas blocking the view in that direction. However, thanks to improved technologies radio telescopes and x-ray telescopes and infrared telescopes, have given us better information. Using infrared telescopes render the thick clouds of dust and gas nearly invisible leaving the stars themselves to be seen. Being able to look through such dense obstructions has allowed us to determine the path of stars in the center orbiting, at incredible speeds, around an invisible point that must be incredibly dense. That point is thought to be a supermassive black hole. In addition, we're also able to better look inside of dusty stellar nurseries, the remnants of supernovae, to see young stars inside.
While 3-D mapping helps better visualize things, by necessity it's still incomplete in terms full accuracy. We still have no real idea what the opposite side of the galaxy looks like as to the composure of and arms and spurs. There's far too much dust and gas in the galaxy, and we're pushing the limits of current technology just to peek in at the center of it. And there are far too many stars in the galaxy to make an accurate 3-D map. That said, we do have an understanding about spirals, and we can make reasonable and educated guesses as to how the structural parts of the galaxy look. Supercomputers are used to be able to better calculate and plot enormous numbers giving a reasonable estimate about the galaxy's structure, as well as from our observation of other similar galaxies. Even though realistically, it's just an educated guess, it's as close to accurate as we can make at the present time. Perhaps in the future, we'll have the means to be able to more clearly see all of the galaxy.
Since the arm we reside is in the same plane as the other arms, we see the dust clouds/arms only with an overlapping perspective, and most of it would be the Orion-Cygnus (minor) arm blocking the view of other arms.
O.k. so for example if we were either above or below the disk then i assume that we could see one of the spiraled arms like in the photo or no?
If you were far enough above or below the galactic plane, you'd have a much better view the spiraled arms because there'd be fewer obstacles blocking the view. For the sake of a comparative example, here's look at a NGC 6217, a barred spiral. Below is a look at M-31 (Andromeda galaxy), a spiral galaxy.
If you were far enough above or below the galactic plane, you'd have a much better view the spiraled arms because there'd be fewer obstacles blocking the view. For the sake of a comparative example, here's look at a NGC 6217, a barred spiral. Below is a look at M-31 (Andromeda galaxy), a spiral galaxy.
I'm wondering if we were for example slightly below the plane and yet still within the galaxy ''could'' we see some type of spiraled arm across the night sky or would we have to be so many trillions of miles backed away as just one arm would cover the entire sky with stars and nebula etx.
I'm wondering if we were for example slightly below the plane and yet still within the galaxy ''could'' we see some type of spiraled arm across the night sky or would we have to be so many trillions of miles backed away as just one arm would cover the entire sky with stars and nebula etx.
We would have to be well above OR below the galactic plane to see the arms. Also they are so relatively tenuous relative to the galactic center that IMO...I doubt you could see them in the sense you suggest.
Essentially you'd need to be in the galactic halo or further out to discern the spiral arms.
I'm wondering if we were for example slightly below the plane and yet still within the galaxy ''could'' we see some type of spiraled arm across the night sky or would we have to be so many trillions of miles backed away as just one arm would cover the entire sky with stars and nebula etx.
I had to do a little figuring. Think of it this way, Proxima Centauri, which is the closest star in the neighborhood to our Sun, is about 4.24 ly away, which converts to 24,908,311,095,247 miles. Ouch! That's almost 25 trillion miles away. But wait! There's more! The average thickness of the galaxy at the Sun is perhaps 2000 ly. You'd have to travel a loooong way out of the galaxy for a good view. Since that's not an alternative for us at the moment, we have to rely on other techniques to determine the arms. One of those ways is by observing areas where stars are more closely grouped, and areas that are more sparse in comparison. A Map of the Milky Way (See box: Properties of the Milky Way)
NB and PITTS thanks for the info and posted links as you all rock n roll .
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