Starship Asterisk*

The Whirlpool Galaxy in Infrared Dust

Explanation: How do spiral galaxies form stars? To help find out, the Hubble Space Telescope imaged the nearby photogenic spiral M51 in infrared light to highlight the dust that traces the dense gas that best forms stars. To further isolate the dust, much of the optical light from stars has also been digitally removed. The resulting unique image shows swirling and intricate patterns on the longest scales, while numerous bright clumps of previously hidden open star clusters appear on the smaller scales. To see the detailed optical light image for comparison, run your cursor over the above image. Anyone with a good pair of binoculars can see the Whirlpool toward the constellation of the Hunting Dogs (Canes Venatici). M51 lies about 30 million light years away, while the above imaged area spans about 15,000 light years from top to bottom. Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with a neighboring smaller galaxy.

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Like looking down into an eye of a hurricane!
Also reminds me of a Mandelbrot set, or actually the Julia Set as it is more spiral.

M51 is classified as a spiral galaxy (Sa). The infrared picture makes the core resemble a barred spiral (SBa). Does anyone else feel the same?

The Two-faced Whirlpool Galaxy
http://asterisk.apod.com/vie ... 29&t=22620

Anybody notice the grid pattern at the center (black hole location) of the infrared image? You must enlarge (select) the image to see it.

Whats really interesting if you zoom in even closer (shift +) you can see the grid pattern extends beyond the dark inky pool that surrounds the central point of light. . . very faintly into the surrounding area. This grid pattern cannot be seen in any other areas of the entire image. . . is this a artifact of the instrument or something really going on in the core region?

kenk wrote:M51 is classified as a spiral galaxy (Sa). The infrared picture makes the core resemble a barred spiral (SBa). Does anyone else feel the same?

You are absolutely right. Very many, if not most, classical spiral galaxies have at least a small bar at their centers. M100 is an example of a galaxy which is generally thought of as no-barred, but which does in fact have a small bar at its center. Another galaxy which has a small central bar is M101:
In this infrared image of M101, the central bar feature is quite noticable.

Ann

Concerning the caption of today's picture [that is supposedly written by a 'professional astronomer']: I am bothered by the increasing misuse of the word 'optical' when what is meant is 'visible.' By saying that the 'optical light has been removed' implies that the non-optical light remains. This foolishness would make an oxymoron out of a term such as 'infrared optics.' Mostly, I think this is just carelessness, but that kind of carelessness is inappropriate for a science feature.

How would you describe an infra-red lens, plantguy?
It has all the characteristics of a visible light refracting assembly, it's just transparent to IR.
So 'infra-red optics'. What oxymoronic element is there?

Nor 'misnomer'. those lenses are lenses - aka 'optics' (unless you are describing spiritous liquor dispensers behind a bar) - and they are designed to refract and focus infra-red light. So optics for infra-red.

But I agree, on 'optical' for 'visible'!

John

The area around the central grid is quite blurred compared with the sharply defined outer part, is this due to high speed of rotation at the center?

This infrared image is really interesting but to me it says a lot more about the nature of the center of the galaxy, as much as anything else. The heat signature of the black hole is really surprising to me. There is one tiny point of heat, surrounded by a cool reagion. That is totally unexpected to me. I guess I just have never seen it before. And surrounding the cool region, the heat signature seems to take on almost a plasma type of pattern, like everything is just liquified at that point. I'd like to know more about people interpretation of that!

Chris L

John,

I agree with you completely!

My point was that if one states that infrared light is somehow 'non-optical' (as opposed to visible light) the implication of this distortion in language, results in the question, how can there be infrared optics if infrared light is somehow not optical light. In my world, all electromagnetic radiation referred to in making an image, becomes (by default) optical: ergo infrared optics and x-ray optics.

Thank you.

DaveH wrote:Whats really interesting if you zoom in even closer (shift +) you can see the grid pattern extends beyond the dark inky pool that surrounds the central point of light. . . very faintly into the surrounding area. This grid pattern cannot be seen in any other areas of the entire image. . . is this a artifact of the instrument or something really going on in the core region?

Dave, I believe that what you're referring to is a result of the pixelization of the image. When a camera like Hubble's "sees" an image, it isn't like the old film images where the light is imprinted on molecules of some photo sensitive substance. Instead it breaks down what it sees as discrete little blocks of light that, when combined, make up the whole image. These blocks of light are known as pixels. When the image was "played with" to get what we're seeing, traces of the pixel boundaries remain. From the description, they had to get rid of a lot of light to be able to see each individual star, and since the core of the galaxy is flooded with light, the computer wasn't able to do a perfect job. In fact, I believe the pixels are actually smaller than the cubes detailed in the center, since the individual stars are smaller than the blocks are. It would seem to me that this (the bars) would add to the theory that it's a result of the computer enhancement.

Hey! That was my sink last night when I turned on the garbage disposal after dumping spoiled tomato sauce in it.

Why has this image been reversed/mirrored/flipped? Does doing so make it easier to work with?

Indigo_Sunrise wrote:Why has this image been reversed/mirrored/flipped? Does doing so make it easier to work with?

I don't think it has. It appears to be a normal view, with north down, east right. That's a 180° rotation from convention, but not unusual.

Chris Peterson wrote:I don't think it has. It appears to be a normal view, with north down, east right. That's a 180° rotation from convention, but not unusual.

Today's image, of course, looks like this.

But in a link from the description, here, it looks to be rotating the other way.

I was just curious whether there is a reason why it has been flipped, or if it's more of an 'imager's choice' type of thing.

Indigo_Sunrise wrote: Today's image, of course, looks like this.

But in a link from the description, here, it looks to be rotating the other way.

I was just curious whether there is a reason why it has been flipped, or if it's more of an 'imager's choice' type of thing.

It is always the imager's choice. The type of telescope matters, as well, in determining the orientation of the raw image. The most common convention is north up, east left, which (with respect to using the eye) provides an unmirrored image with a standard rotation. Today's image is close to that- unmirrored but south up. But there's no rule, just convention, and that convention is often broken- especially with images taken with an aesthetic intent.

All the same, the mirrored orientation of the second image you reference is unusual- a point that was discussed on this forum when that APOD was published. The vast majority of M51 images you see will be like today's APOD, although with different rotations.

Anyone (in the Northern Hemisphere) with a good pair of binoculars can see the Whirlpool toward the constellation of the Hunting Dogs (Canes Venatici).