APOD: WISE Infrared Andromeda (2010 Feb 19)

[APOD Robot]

WISE Infrared Andromeda

Explanation: This sharp, wide-field view features infrared light from the spiral Andromeda Galaxy (M31). Dust heated by Andromeda's young stars is shown in yellow and red, while its older population of stars appears as a bluish haze. The false-color skyscape is a mosaic of images from NASA's new Wide-field Infrared Survey Explorer (WISE) satellite. With over twice the diameter of our Milky Way, Andromeda is the largest galaxy in the local group. Andromeda's own satellite galaxies M110 (below) and M32 (above) are also included in the combined fields. Launched in December 2009, WISE began a six month long infrared survey of the entire sky on January 14. Expected to discover near-Earth asteroids as well as explore the distant universe, its sensitive infrared detectors are cooled by frozen hydrogen.

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[sagansmyhero]

So obviously, we're looking at M31 through a veil of foreground stars that live in our own galaxy.

But are some of those dots actually other galaxies in the far distance? I'm thinking specifically about that red dot just above M31 and a little right of center.

[FrankAa]

Yes, I was wondering too... What are all the red dots? The picture is really sprinkled with them.

[Mr T]

Is it just me or does anyone else see a spiral structure in M110?

[geckzilla]

The red dots are 22-micron light, according to this. 22 microns is a small slice of the infrared part of the electromagnetic spectrum.

Infrared radiation (IR) is electromagnetic radiation with a wavelength between 0.7 and 300 micrometres

[FrankAa]

Which means that they are... ?

[geckzilla]

Things which emit or reflect 22-micron light. What can I say? Maybe one of the resident experts can enlighten us further.

[neufer]

Things which emit or reflect 22-micron light.

"Dust heated by Andromeda's young stars" to ~ 100ºK emits 22-micron light
(just as asteroids & comets heated by the sun ~ 200ºK emit 12-micron light).

[geckzilla]

So it's dust, then? You astronomers and your dust.

[FrankAa]

I don't think they are astroids or dust... The red dots are all over the picture, so they are not associated with the galaxy. Maybe they are background galaxies or foreground stars.

[orin stepanek]

what do we have if we compare the infrared to this picture? http://apod.nasa.gov/apod/ap100109.html do the red dots you see correspond to what looks like a galaxy?

Orin

[neufer]

Most of the infra- "red dots" are probably concentrations of Bok globules within H II regions:

http://antwrp.gsfc.nasa.gov/apod/ap091017.html
http://antwrp.gsfc.nasa.gov/apod/ap090414.html
http://apod.nasa.gov/apod/ap080215.html

<<The actual birth of stars within H II regions is hidden from us by the dense clouds of gas and dust which surround the nascent stars. It is only when the radiation pressure from a star drives away its 'cocoon' that it becomes visible. Before then, the dense regions which contain the new stars are often seen in silhouette against the rest of the ionised nebula—these dark patches are known as Bok globules, after astronomer Bart Bok, who proposed in the 1940s that they might be stellar birthplaces. Confirmation of Bok's hypothesis had to wait until 1990, when infrared observations finally penetrated the thick dust of Bok globules to reveal young stellar objects within. It is now thought that a typical Bok globule contains about 10 solar masses of material in a region about a light-year or so across, and that Bok globules most commonly result in the formation of double or multiple star systems.>>

[FrankAa]

I've compared the images. Most red dots appear as really faint gray dots in the visible light image.

If they were Bok-globules, as Art says, they should be within the milkyway, which seems a bit strange to me because they are so separated from everything. But maybe they are, I don't know.

[FrankAa]

At least one of the red dots corresponds to a fluffy white spot in visible light, so that would be a background galaxy, I guess.

[Storm_norm]

is it possible that the better resolution we use on the heavens could help make points of EM radiation stand out? would these red points of light be missed in other resolutions?

not really sure how to word the question.

the analogy I am trying to use here is when you use binoculars in semi-darkness. all sources of light are magnified, not just the image.

I don't know, maybe this is coming out of left field.

[FrankAa]

Well... if we forget about the dots for a moment...

What really intrigues me about this picture is the weird form the galaxy has in infrared. I see a ring of fire (which is really a huge spiral arm). Outside the ring, I see some matter that seems to be pulled away from the ring (left) and a partial outer ring (right). Inside the ring I see a smaller spiral system which is more like our own milkyway.

How did all this come to be?

[RJN]

I have emailed the WISE outreach team and asked them to check into these questions. I didn't write this APOD, and I haven't done much background research on this, but my guess would be that red blobs appearing in M31 itself are glowing dust in M31's dusty nebulas. The red dots scattered around the image, however, are more likely particularly cool stars that reside in our foreground Milky Way galaxy.

[Michel P]

I wonder what the night sky would look like for a planet in M110 or M32. Would M31 be seen edge on, as a full disc or something in between? Would Andromeda block out a considerable part of the night sky, and how bright would it be? What insights on the structure and evolution of galaxies would be available from such a view that aren't accessible to astronomers on earth?

[FrankAa]

Thanks RJN... The questions of Michel are nice too

[Chris Peterson]

I wonder what the night sky would look like for a planet in M110 or M32. Would M31 be seen edge on, as a full disc or something in between? Would Andromeda block out a considerable part of the night sky, and how bright would it be? What insights on the structure and evolution of galaxies would be available from such a view that aren't accessible to astronomers on earth?

I think their night skies would look very similar to our own. From M110, M32 would probably resemble the Milky Way- a faint glowing band across the sky. From M32, M110 would probably resemble the Large Magellanic Cloud- one of our own satellite galaxies.

I don't think astronomers in those locations would see anything we couldn't see from here, in terms of understanding the nature of the cosmos.

[neufer]

I wonder what the night sky would look like for a planet in M110 or M32. Would M31 be seen edge on, as a full disc or something in between? Would Andromeda block out a considerable part of the night sky, and how bright would it be? What insights on the structure and evolution of galaxies would be available from such a view that aren't accessible to astronomers on earth?

I think their night skies would look very similar to our own. From M110, M32 would probably resemble the Milky Way- a faint glowing band across the sky. From M32, M110 would probably resemble the Large Magellanic Cloud- one of our own satellite galaxies.

I don't think astronomers in those locations would see anything we couldn't see from here, in terms of understanding the nature of the cosmos.

From M32, M31 would probably be seen edge on and resemble "a faint glowing band across" one hemisphere of the sky almost perpendicular to it's own (relatively dust free) Milky Way.

From M110, M31 would probably resemble an enormously large Magellanic Cloud blocking out a considerable portion of one hemisphere of the night sky as regards to observing more distant galaxies.

We know little about the galaxies lurking behind our own Milky Way; even the close ones:

<<The Canis Major Dwarf galaxy was first discovered in November 2003 by an international team of astronomers. Although closer to the Earth than the centre of the galaxy itself, the Canis Major Dwarf galaxy was difficult to detect as it is located behind the plane of the Milky Way, where concentrations of stars, gas and dust are densest. This, along with its small size, explains why it was not discovered sooner. The team of astronomers that discovered it were collaborating on analysis of data from the Two-Micron All Sky Survey (2MASS), a comprehensive survey of the sky in infrared light, which is not blocked by gas and dust as severely as visible light. Because of this technique, scientists were able to detect a very significant over-density of class M giant stars in a part of the sky occupied by the Canis Major constellation, along with several other related structures composed of this type of star, two of which form broad, faint arcs.>>

[kjardine]

There have been quite a number of articles published in the scientific literature questioning the existence of a Canis Major Dwarf Galaxy.

See:
http://adsabs.harvard.edu/abs/2008ApJ...672..930V

as just one example. (This article points out that the Orion Spur extends in this direction and is a more credible explanation for the observed "overdensity" than a dwarf galaxy.)

The Wikipedia article you cite has one paragraph remarking on this controversy - in my view this article should be rewritten to make it clearer that a "Canis Major Dwarf Galaxy" is a controversial hypothesis rather than a confirmed object, or still better, given the level of scientific controversy, it should just be deleted.

[rstevenson]

The Wikipedia article you cite has one paragraph remarking on this controversy - in my view this article should be rewritten to make it clearer that a "Canis Major Dwarf Galaxy" is a controversial hypothesis rather than a confirmed object, or still better, given the level of scientific controversy, it should just be deleted.

Wikipedia has a process for making these sorts of changes, if needed. Register and participate. It's a Good Thing.

Rob

[RJN]

There was an APOD specifically on the Canis Major Dwarf: http://apod.nasa.gov/apod/ap071104.html . Perhaps the explanation there is more satisfying. Indeed, though, our APOD explanations are rarely perfect -- but we try. Thanks, kjardine, for point out that reference. - RJN

[kjardine]

Wikipedia has a process for making these sorts of changes, if needed. Register and participate. It's a Good Thing.

If you check the discussion for that Wikipedia article, you'll see that I recommended that the article be deleted about two years ago. I was even supported by another poster who added another journal citation. Nothing has happened, however.

There is no way I'm going to delete the article myself. For a while I spent some time trying to repair various astronomy posts on Wikipedia, but I got tired of the weird politics and strange (to me) notion of truth often used to justify Wikipedia "facts". I've got better uses for my time than getting into a s**t fight on Wikipedia!