APOD: Clouds of Andromeda (2018 Jan 08)

Comments and questions about the APOD on the main view screen.
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MarkBour
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Re: APOD: Clouds of Andromeda (2018 Jan 08)

Post by MarkBour » Tue Jan 09, 2018 5:02 pm

BDanielMayfield wrote:
MarkBour wrote:
neufer wrote: You don't see a red spiral :?:
Now I'm pretty sure you're having fun with me. So instead of trying to see what you're talking about, I'm trying to remember who said what. But, alas, I get it not.
Try looking for red inside "the great galaxy in Andromeda" instead of around it.
Thank you, Bruce. Art, is this what you meant?
I guess what threw me was Art's: '... "scattered hundreds of light-years" above Andromeda's arms'.
At this distance, hundreds of light years only amounts to what, a pixel? Always, my intuition leads me astray.
I'm really only responding at this point because I may not have been the only one thrown off by that.

But then, bringing the discussion back to the debate about the title, assuming Art is correct, then this really is an image of the clouds of Andromeda, in the sense that others have said it was not.
Mark Goldfain

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neufer
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Mark "seemingly tangled in the dust"

Post by neufer » Tue Jan 09, 2018 9:11 pm

MarkBour wrote:
I guess what threw me was Art's: '... "scattered hundreds of light-years" above Andromeda's arms'.
At this distance, hundreds of light years only amounts to what, a pixel? Always, my intuition leads me astray.

But then, bringing the discussion back to the debate about the title, assuming Art is correct, then this really is an image of the clouds of Andromeda, in the sense that others have said it was not.
https://apod.nasa.gov/apod/ap151012.html wrote:
<<The galaxy seemingly tangled in the dust is the striking spiral galaxy NGC 7497 some 60 million light-years away. Seen almost edge-on near the center of the field, NGC 7497's own spiral arms and dust lanes echo the colors of the Milky Way's stars and dust. >>
Art Neuendorffer

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Re: APOD: Clouds of Andromeda (2018 Jan 08)

Post by Martin » Thu Feb 01, 2018 6:04 am

Is there an explanation for how ionized hydrogen clouds can be found so far from the galactic plane? Thanks

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neufer
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Re: APOD: Clouds of Andromeda (2018 Jan 08)

Post by neufer » Thu Feb 01, 2018 3:21 pm

Martin wrote:
Is there an explanation for how ionized hydrogen clouds can be found so far from the galactic plane? Thanks
https://en.wikipedia.org/wiki/H_II_region wrote:
<<An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically a cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic cm. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.

They may be of any shape, because the distribution of the stars and gas inside them is irregular. The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. They often appear clumpy and filamentary, sometimes showing bizarre shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster of stars which have formed, such as the Pleiades.

H II regions can be observed at considerable distances in the universe, and the study of extragalactic H II regions is important in determining the distance and chemical composition of galaxies. Spiral and irregular galaxies contain many H II regions, while elliptical galaxies are almost devoid of them. In spiral galaxies, including our Milky Way, H II regions are concentrated in the spiral arms, while in irregular galaxies they are distributed chaotically. Some galaxies contain huge H II regions, which may contain tens of thousands of stars. Examples include the 30 Doradus region in the Large Magellanic Cloud and NGC 604 in the Triangulum Galaxy.>>
https://en.wikipedia.org/wiki/Molecular_cloud wrote: <<A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H2). This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.

Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is carbon monoxide (CO). The ratio between CO luminosity and H2 mass is thought to be constant, although there are reasons to doubt this assumption in observations of some other galaxies.

Within molecular clouds are regions with higher density, where lots of dust and gas cores reside, called clumps. These clumps are the beginning of star formation, if gravity can overcome the high density and force the dust and gas to collapse.>>
Art Neuendorffer

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Cousin Ricky
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Re: APOD: Clouds of Andromeda (2018 Jan 08)

Post by Cousin Ricky » Thu Feb 01, 2018 8:38 pm

heehaw wrote:Clouds OF Andromeda is not wrong, it is perfect! The wrong nomenclature is "the Andromeda galaxy:" it should be "the galaxy far beyond Andromeda."
Is there a rule that Andromeda is confined to the Milky Way Galaxy?

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Re: APOD: Clouds of Andromeda (2018 Jan 08)

Post by Chris Peterson » Thu Feb 01, 2018 8:53 pm

Cousin Ricky wrote:
heehaw wrote:Clouds OF Andromeda is not wrong, it is perfect! The wrong nomenclature is "the Andromeda galaxy:" it should be "the galaxy far beyond Andromeda."
Is there a rule that Andromeda is confined to the Milky Way Galaxy?
In fact, Andromeda, like all the constellations, extends to infinity.
Chris

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