APOD: Herschel's Andromeda (2013 Feb 02)

[APOD Robot]

Herschel's Andromeda

Explanation: This infrared view from the Herschel Space Observatory explores the Andromeda Galaxy, the closest large spiral galaxy to our own Milky Way. Only 2.5 million light-years distant, the famous island universe is also known to astronomers as M31. Andromeda spans over 200,000 light-years making it more than twice the size of the Milky Way. Shown in false color, the image data reveal the cool dust lanes and clouds that still shine in the infrared but are otherwise dark and opaque at visual wavelengths. Red hues near the galaxy's outskirts represent the glow of dust heated by starlight to a few tens of degrees above absolute zero. Blue colors correspond to hotter dust warmed by stars in the more crowded central core. Also a tracer of molecular gas, the dust highlights Andromeda's prodigious reservoir of raw material for future star formation.

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[Ann]

It's a fine picture, and the caption has improved tremendously since NASA wrote about this picture on January 30. See http://asterisk.apod.com/viewtopic.php?f=31&t=30625.

Ann

[owlice]

"the" caption? The text supplied by JPL and the APOD explanation were written by two different individuals.

[saturno2]

M 31 Andromeda
Infrared view
This spiral Galaxy is in the Local Group
Two times the size that Our Galaxy Milky Way
Andromeda is beautiful in the normal color

[BDanielMayfield]

This image was the subject of a very recent S&T article: http://www.skyandtelescope.com/news/Rea ... 85351.html
In the comments following the article I asked why these dust rings didn’t appear to be aligned with the more familiar visible views of Andromeda’s spiral arms. Peter gave me what I thought was a very good answer.

[neufer]

[c]Harvard Astronomy 201B : ISM and Star Formation[/c]
<<The Spitzer Space Telescope has three instruments on-board:

• IRAC (Infrared Array Camera) is an infrared camera operating on four wavelengths (3.6 µm, 4.5 µm, 5.8 µm and 8 µm).
  
  IRS (Infrared Spectrograph) is an infrared spectrometer with four sub-modules operating at the wavelengths 5.3-14 µm (low resolution), 10-19.5 µm (high resolution), 14-40 µm (low resolution), and 19-37 µm (high resolution).
  
  MIPS (Multiband Imaging Photometer for Spitzer) has three detector arrays in the far infrared (128 × 128 pixels at 24 µm, 32 × 32 pixels at 70 µm, 2 × 20 pixels at 160 µm).

Dust Distribution in M31 Showing Evidence of a Galactic Collision

[b][color=#FF0000]Fig.10: The Andromeda Galaxy (M31) at 24-micron by MIPS[/color][/b] (Image Credit: http://www.spitzer.caltech.edu/&#41 )

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[b][color=#0000FF]Fig.11: M31 Inner Dust Ring at 8-micron by IRAC[/color][/b] (Image Credit: http://www.spitzer.caltech.edu/&#41 )

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<<Here is an image of M31 at 24-micron. An outer ring of dust is prominent. This picture is constructed from 11,000 separate snapshots by MIPS. Asymmetrical features are seen in the prominent ring of star formation. The ring appears to be split into two pieces, forming the hole to the lower right. These features may have been caused by interactions with satellite galaxies (such as M32 and M110) around M31 (The Andromeda Galaxy) as they plunge through its disk. This image also reveals tracings of spiral arms within this ring that reach into the very center of the galaxy.

With a further imaging using IRAC onboard Spitzer, new evidence was found that the Andromeda Galaxy was probably involved in a violent head-on collision with the neighboring dwarf galaxy Messier 32 (M32) more than 200 million years ago. The following image (Fig.11) reveals an inner dust ring deep within the Andromeda galaxy in addition to the outer prominent dust ring visible in the 24-micron image (Fig.10). When combined with a previously observed outer ring, the presence of both dust rings suggests that M32 plunged through the disk of the Andromeda Galaxy along Andromeda’s polar axis approximately 210 million years ago. (Ref: http://www.spitzer.caltech.edu/)

What is most interesting is that the centers of those rings (outer ring center is number 1 with red color, inner ring center is number 2 with green color) are offset from the galactic center (number 3 with purple color in the upper diagram (Fig.11)). The outer ring of star formation is offset from the galactic center by about 1kpc, which is about 10% of the radius of the outer ring. The inner ring of star formation is offset from the galactic center by about 0.5kpc, which is about 40% of the radius of the inner ring.>>

[Psnarf]

I was looking for the color codes when I found these wavelengths on the ESA Hershel site: blue is 70 mm, green is 100 mm, and red is combined 160 mm and 250 mm. Blue is hotter than green; red is colder than green, only a few degrees above 0-kelvin. Just for fun, I reached for my 32-cm ruler. Seven centimeters is about the length of my index finger. It is difficult for me to imagine infrared waves that long, much too large to get past the pupils of our eyeballs. Wavelengths at 25cm are emitted by extremely cold dust. The structure of the black hole at the center of the galaxy appears strange to me on the large images. http://www.herschel.caltech.edu/media/i ... 3-004b.jpg Perhaps it is an optical illusion.
-"Musings of a Complete Idiot", 3.14:159.

[charlesking7]

In this image Is the near edge of the Andromeda galaxy at the bottom left or top right? How much distortion does the image have with the (less than as a sin function of tilt angle) 200,000 light year distance from those edges?

[Chris Peterson]

The structure of the black hole at the center of the galaxy appears strange to me on the large images. http://www.herschel.caltech.edu/media/i ... 3-004b.jpg Perhaps it is an optical illusion.

We can't begin to see any hint of structure related to Andromeda's central black hole at the scale of these images. The core structure you are referring to, while interesting, is probably unrelated to that black hole, which is structurally evident only in the central few tens of light years.

[drollere]

the "ring" structure, known as a circumnuclear ring, seems to occur in about 20% of spiral galaxies (in a small sample) and is associated with an active galactic nucleus. computer simulations suggest that the rings would result from the near collision of two galactic nuclei; the ring is compressed from the nucleus outward as a massive shock wave. the shock wave rolls up the interstellar medium to create large and very active star forming regions, which are indicated by the brightest areas in the infrared.

this is a beautiful image, and it is fascinating that beauty often goes with the analytical content of an image, so that beauty is the affective experience of insight into fundamental structure or process.

[neufer]

I was looking for the color codes when I found these wavelengths on the ESA Hershel site: blue is 70 mm, green is 100 mm, and red is combined 160 mm and 250 mm. Blue is hotter than green; red is colder than green, only a few degrees above 0-kelvin. Just for fun, I reached for my 32-cm ruler. Seven centimeters is about the length of my index finger. It is difficult for me to imagine infrared waves that long, much too large to get past the pupils of our eyeballs.

Difficult for any of us to imagine infrared waves that long.

That's MICRO-meters not millimeters, Psnarf.

Blue is 70 µm, green is 100 µm, and red is combined 160 µm and 250 µm.

[nstahl]

It's interesting that we think of red as a hot color and blue a cool color when the opposite is more true. But not in our physical experience.

And it's great how our scientists can use the whole spectrum to learn SO Much about the universe around us.

[anon]

"making it more the twice the size" Good grief. It always pains me to see APOD explanations with grammar and spelling errors.

[BDanielMayfield]

Thanks neufer for sharing the Spitzer info showing the collisional causation for these ring structures, and thanks also to drollere for adding this:

the "ring" structure, known as a circumnuclear ring, seems to occur in about 20% of spiral galaxies (in a small sample) and is associated with an active galactic nucleus. computer simulations suggest that the rings would result from the near collision of two galactic nuclei; the ring is compressed from the nucleus outward as a massive shock wave. the shock wave rolls up the interstellar medium to create large and very active star forming regions, which are indicated by the brightest areas in the infrared.

this is a beautiful image, and it is fascinating that beauty often goes with the analytical content of an image, so that beauty is the affective experience of insight into fundamental structure or process.

I like your concluding statement drollere. I am often more moved by the reasons why these images appear as they do, even when they exibit extraordinary beauty.

So the infrared rings in Andromeda in a way are like the round wave in a pond speading out after a rock is dropped into it.

Another insight I'm enjoying from this is that small galaxies orbiting around and even thruogh large galaxies can have a large effect upon a large galaxy's star formation rate.

[emc]

"making it more the twice the size" Good grief. It always pains me to see APOD explanations with grammar and spelling errors.

It pains me to see my own errors... I feel relief when I see other's.

[owlice]

I'm getting verse...

• O beautiful spiral in the sky
  How far away from us you lie
  Yet drawing closer, someday to be
  Merging with us... well, not me
  
  'cause I'm definitely not going to be around for that.

[emc]

some have hope with dream
there will be infinite time to glean

[MikeJ]

While there is no up or down in space, every time I see the Andromeda or other galaxy at a steep angle like this I wonder are we looking up at the bottom or down at the top. In other words is the edge to the right top closer to us or is it the bottom left and at that distance can we really know for sure?

[Jedster1]

"making it more the twice the size" Good grief. It always pains me to see APOD explanations with grammar and spelling errors.

It pains me to see my own errors... I feel relief when I see other's.

Then you'll be pained to learn that it's " others' " or " another's " but not " other's ".

Speaking of optical illusions, when first I opened the page the photo looked 3D to me. Very strange and unexpected, but quite enjoyable.

[emc]

In referring to another person besides me, “other’s” is correct.

[ErnieM]

The two arms protruding from the opposite ends of the galactic bar appears to me to be very loosely connected to the rest of the "rings and arcs" making up the bulk of the galactic disc. I suppose each of these "rings and arcs" represents past galaxy collisions. Just curious if some backward computer simulations have been attempted to give us an idea (virtually) on how this island universe came to be the way it looks now. After all, it is the largest neighboring galaxy to our Milky Way.

[neufer]

In referring to another person besides me, “other’s” is correct.

Hmmm...

Your “significant other’s” significant mistake is what comes to mind.

[emc]

I should introduce you to her… she has a great sense of humor… how else would she tolerate me?

[Jedster1]

In referring to another person besides me, “other’s” is correct.

Sadly, just saying it is so doesn't make it so, but you just keep on blissfully botching the English language. You're not the only one. Oh, wait, perhaps you're one of those that say "your not the only one".

Nobody cares any more, anyway. Why the hell should I? Carry on.

[Anthony Barreiro]

While there is no up or down in space, every time I see the Andromeda or other galaxy at a steep angle like this I wonder are we looking up at the bottom or down at the top. In other words is the edge to the right top closer to us or is it the bottom left and at that distance can we really know for sure?

It looks to me like the left hand edge is closer. You can see faint blue and green blotches of hotter gas to the lower left of that edge, against the blackness of intergalactic space. These look like small objects orbiting the galaxy -- globular clusters perhaps? On the opposite right hand edge, the faint blue and green blotches are superimposed against the much more saturated red spirals, as if they are seen against the background of the galactic disk. Any faint blue and green splotches behind the galactic disk would be hidden by the disk itself.

That's just how it looks to me. Maybe somebody else actually knows for sure.

This is an interesting image, and a fitting tribute to the Herschel space telescope which has shown us the infrared universe.

Bruce is right, the Sky and Telescope article is worth reading.