APOD: Clouds of Andromeda (2017 Jan 04)

[APOD Robot]

Clouds of Andromeda

Explanation: The beautiful Andromeda Galaxy is often imaged by planet Earth-based astronomers. Also known as M31, the nearest large spiral galaxy is a familiar sight with dark dust lanes, bright yellowish core, and spiral arms traced by blue starlight. A mosaic of well-exposed broad and narrow-band image data, this colorful, premier portrait of our neighboring island universe offers strikingly unfamiliar features though, faint reddish clouds of glowing ionized hydrogen gas in the same wide field of view. Still, the ionized hydrogen clouds likely lie in the foreground of the scene, well within our Milky Way Galaxy. They could be associated with the pervasive, dusty interstellar cirrus clouds scattered hundreds of light-years above our own galactic plane. If they were located at the 2.5 million light-year distance of the Andromeda Galaxy they would be enormous, since the Andromeda Galaxy itself is 200,000 or so light-years across.

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[Ele6]

It looks so weird that way up.

[geckzilla]

Sorry I was late getting the thread up this morning. I woke up a bit later and forgot for a bit. Sometime soon I expect that the process will become automated again.

Nice picture, Rogelio. I understand it is quite challenging to get those cirrus clouds to show up around Andromeda.

[NoelC]

It's pretty impressive to show so clearly the hydrogen features that the red plates from the POSS II DSS only show the barest hint of, and only then when pushed beyond any reasonable limits. I sense you've compressed a monstrous dynamic range into the result. Not bad - it looks pretty natural.

-Noel

[Guest]

Howdy,
I'm barely even a hobbyist with no astronomical education...just a curiosity. And I love reading APOD.

Something about the explanation of the red bits being ionized hydrogen clouds (far) in front of Andromada seems out of place to me. If there were clouds between us and M31, why then do they conform to a pattern of appearing only on M31 spirals? Would we not see a more random distribution of clouds and not all of them in front of M31?

[geckzilla]

Something about the explanation of the red bits being ionized hydrogen clouds (far) in front of Andromada seems out of place to me. If there were clouds between us and M31, why then do they conform to a pattern of appearing only on M31 spirals? Would we not see a more random distribution of clouds and not all of them in front of M31?

What do you mean? Galactic cirrus is all over the sky. It roughly follows the shape of our galaxy—a disk.

[Chris Peterson]

Howdy,
I'm barely even a hobbyist with no astronomical education...just a curiosity. And I love reading APOD.

Something about the explanation of the red bits being ionized hydrogen clouds (far) in front of Andromada seems out of place to me. If there were clouds between us and M31, why then do they conform to a pattern of appearing only on M31 spirals? Would we not see a more random distribution of clouds and not all of them in front of M31?

I think it's your personal image processing system which is falsely concluding that the hydrogen clouds are lining up with any structure in the galaxy. I can make mine do that, as well, but I have more experience studying images like this, so it's easier for me to recognize such illusions and ignore them.

[Tszabeau]

Assuming that the interstellar cirrus clouds shown are associated with the Milky Way and not Andromeda... where are the ones that are, surely, associated with it? Just too faint to be photograhed?

[Ann]

It's pretty impressive to show so clearly the hydrogen features that the red plates from the POSS II DSS only show the barest hint of, and only then when pushed beyond any reasonable limits. I sense you've compressed a monstrous dynamic range into the result. Not bad - it looks pretty natural.

-Noel

Noel, you're back! I've really missed you!

And Rogelio, that's a splendid image. You've outdone yourself again!

Click to view full size image

Galaxy M82. Photo: Ken Crawford.

Click to view full size image

Clouds of Andromeda. Photo: Rogelio Bernal Andreo.

I have to agree with those who think that it looks as if the red clouds of hydrogen seem to follow the outline of the Andromeda galaxy, but I also agree that this is an illusion. M31 itself shows no signs of of being associated with the sort of galactic outflows that might show up as a red halo engulfing the entire galaxy.

Check out the picture of galaxy M82 at left. You can see that the red clouds of hydrogen emanate from the center of the galaxy. Note that the outflow at upper left stretches far away from the galaxy, almost as far away as the galaxy is long. By contrast, no red clouds can be seen at the edges of the disk. Also there are no red clouds elsewhere in the background.

M31 looks completely different in today's APOD. Its core appears to be completely "quiet", and there is no obvious association between the red clouds and the galaxy at all. Instead, the little red puffs of gas are scattered all over the picture, as they would be, if they were associated with our own galaxy and not M31.

However, there are some interesting and apparently wind-blown red gas structures at top center in today's APOD. If they were not ionized by the galaxy, what caused them? I'm going to stick my neck out and guess that they may, indeed, be a remnant of a past outburst of Nu Andromeda, the brightest blue star in the picture, located just below center. Unfortunately, Nu And is a B5-type star, with a "surface temperature" of about 15,000K, which is really too cool to ionize a nebula. Yes, but you have to remember that the nebula in today's APOD is exceedingly faint. Also Nu And is a tight binary star, and according to Jim Kaler, the two components of Nu And are separated by only about three stellar radii! I can easily see them having had an outburst of some sort in the past, which may have left behind this very faint nebula.

Anyway, what a great picture! Again, thanks, Rogelio!

Ann

[MarkBour]

That's a beautiful image!

Assuming that the interstellar cirrus clouds shown are associated with the Milky Way and not Andromeda... where are the ones that are, surely, associated with it? Just too faint to be photograhed?

https://www.nasa.gov/audience/foreducat ... Faint.html explains that any object is going to be fainter, the farther it is away from you, by an inverse square law. If you look at a typical galactic cirrus cloud in today's APOD and imagine that it is in the Milky Way, then it is at most about 90,000 light years away from us, or you could say typically 50,000 light years away would be a reasonable initial guess. And I'm assuming it is somewhere in or near the visible disk one would see from a distant view of our galaxy.

Now Andromeda is 2,500,000 light years away. A galactic cirrus cloud in Andromeda then would be an object in or near its disk, and would be 2,500,000 / 50,000 = 50 times as far away, roughly. Such a cloud, then, would be 50x50 = 2500 times as faint as one in our galaxy, and also 2500 times as small in apparent extent (area).

It would be interesting to learn more of these clouds we are seeing here.

I'm going to stick my neck out and guess that they may, indeed, be a remnant of a past outburst of Nu Andromeda, the brightest blue star in the picture, located just below center.

If, as Ann is guessing, they were created by the star(s) Nu Andromedae, then they are somewhere near it, at only 620 light years distant from Earth. So, if what you are seeing is a cloud at only 600 light years, now a comparable cloud in Andromeda itself would be 2,500,000 / 600 = 4167 times as far away. So a similar cloud in Andromeda would be (very roughly) 4000x4000 = 16 million times as small in area and 16 million times as faint!

One other thought on the illusion. If you go look at the moon on a night where conditions are right and there are a few (earth-atmosphere) cirrus clouds "around" it, they will definitely tend to look like they are somehow being affected by the Moon. The Moon will be so bright that it will shine right through the clouds and it will often appear as if the clouds have parted around it, because of this. This effect is even more pronounced in camera images. If one of the clouds in today's APOD appeared to run right across and in front of Andromeda, it would help us see it correctly. But the image of Andromeda is bright enough, I think, that it is preventing that, in the same way that the Moon does to earthly clouds. (See https://www.metabunk.org/explained-why- ... oon.t7084/).

[RBAF]

It's pretty impressive to show so clearly the hydrogen features that the red plates from the POSS II DSS only show the barest hint of, and only then when pushed beyond any reasonable limits. I sense you've compressed a monstrous dynamic range into the result. Not bad - it looks pretty natural.

Thank you Noel, Geckzilla, Ann and everyone!

I started treating the LRGB and Ha data separately. The LRGB data was easy to bring, of course, and the Ha data was nothing but a fight trying to isolate signal from noise. Check the WHAM survey, it'll show a much clearer correlation.

Rogelio

[Chris Peterson]

If, as Ann is guessing, they were created by the star(s) Nu Andromedae, then they are somewhere near it, at only 620 light years distant from Earth. So, if what you are seeing is a cloud at only 600 light years, now a comparable cloud in Andromeda itself would be 2,500,000 / 600 = 4167 times as far away. So a similar cloud in Andromeda would be (very roughly) 4000x4000 = 16 million times as small in area and 16 million times as faint!

The inverse square law doesn't apply in the way you might expect to extended sources. This cloud, at Andromeda, would have the same surface brightness as the cloud much closer. It would just be smaller. This is why the entire Andromeda galaxy is about the same brightness to our naked eyes as the band of the Milky Way. Because it's a galaxy similar to our own.

[Boomer12k]

Learn something new everyday... Galactic Cirrus...

Interesting, and great looking image.

Very cold clear skies next few nights... but too cold for me... might get out the Binocs... not sure yet...more snow maybe Saturday, then ugh... freezing rain....
:---[===] *

[neufer]

Learn something new everyday... Galactic Cirrus...

It's the Galactic Cumulonimbus you have to be careful about.

[Oldironsides]

It looks so weird that way up.

Can't say if this was intentional or accidental but this image of M31 has been rotated 90 degrees.

[Chris Peterson]

It looks so weird that way up.

Can't say if this was intentional or accidental but this image of M31 has been rotated 90 degrees.

With respect to what?

[neufer]

[b][color=#0000FF]Andromeda as depicted in Urania's Mirror, a set of constellation cards published in London c. 1825, showing the constellation from the inside of the celestial sphere[/color][/b]

---

It looks so weird that way up.

Can't say if this was intentional or accidental but this image of M31 has been rotated 90 degrees.

With respect to what?

Certainly not with respect to Andromeda, herself, who seems rather upset that her nice Nu red cirrus gown has gotten somewhat Messier.

[RBAF]

It looks so weird that way up.

Can't say if this was intentional or accidental but this image of M31 has been rotated 90 degrees.

The image appears rotated 180 degrees from the way it's usually photographed, but as pointed out, N/S/E/W orientations in space are mostly for our own reference.

Most images of M31 present it as if we're above the galaxy. Here, it appears as if we're below it. It's deliberate, but not for the sake of doing something "different". Not only with the "appearance" of the red clouds I liked it this way more, with the brightest clouds being up where they're noticed first, but generally speaking, I simply like more seeing M31 in this orientation. Believe it or not, seeing something above or below you can be perceived differently. I can go on that topic for a while, but I also don't want to sound too involved

Of course, rotating a familiar vista can throw some people away, and that's when my intention to give a different experience (rather than a different orientation) can fail. It may help to forget for a moment you're looking at M31, and examine the image as a "brand new" galaxy from below, something for which this image is probably as good as it gets since one could say it was taken out of Cygnus. Other than that, you're welcome to rotate the image in your own screen if you'd rather look at the image that way

Best,
Rogelio

[grootski]

grootski
asternant

The Ionized Hydrogen red clouds depicted between Earth and M3. I see at least five bands of ionized clouds, I'm calling them, "magnetic Shock Waves" of ionized Hydrogen cloud rings from a Nova of many light years past. The shape of the rings, curved , indication of the direction of the Exploding star and 10º east from north . Agreeing with the Question, in between M31 and our Milky Way. They are not visible in M31 of December 27 A POD Pod Image and is some-what closer to us, although that M31 is reversed from the January 4 image in question is a relevant question to the ionized clouds they are this side of Andromeda Galaxy of Jan. 4.

I thank you for trying to help this 98 year old man and with MG 'm legally blind. After reading your postings on my posts they tell me something, Bye.
submitted - January 6,2017

[Ann]

grootski
asternant

The Ionized Hydrogen red clouds depicted between Earth and M3. I see at least five bands of ionized clouds, I'm calling them, "magnetic Shock Waves" of ionized Hydrogen cloud rings from a Nova of many light years past. The shape of the rings, curved , indication of the direction of the Exploding star and 10º east from north . Agreeing with the Question, in between M31 and our Milky Way. They are not visible in M31 of December 27 A POD Pod Image and is some-what closer to us, although that M31 is reversed from the January 4 image in question is a relevant question to the ionized clouds they are this side of Andromeda Galaxy of Jan. 4.

I thank you for trying to help this 98 year old man and with MG 'm legally blind. After reading your postings on my posts they tell me something, Bye.
submitted - January 6,2017

Grootski, I so admire you for checking out the APOD and trying to understand what you are seeing there, even though you are 98 years old and legally blind.

But I want to point out that you haven't seen these red clouds in any image before, because they are exceedingly faint. Rogelio Bernal Andreo, the photographer who took the image, is the first person to have photographed them.

Ann

[RBAF]

Rogelio Bernal Andreo, the photographer who took the image, is the first person to have photographed them.

Actually, these clouds were already detected in the VTSS H-Alpha survey, and prior to my image, it was Sean Walker from S&T who noticed them in one of his own shots. I wrote the whole story here: http://www.deepskycolors.com/Clouds_of_Andromeda.html

It is true, however, that this is the first full-color image showing these clouds in such obvious manner (a bit "in your face" if you will).

Rogelio