APOD: NGC 4631: The Whale Galaxy (2016 Jun 03)

[APOD Robot]

NGC 4631: The Whale Galaxy

Explanation: NGC 4631 is a big beautiful spiral galaxy. Seen edge-on, it lies only 25 million light-years away in the well-trained northern constellation Canes Venatici. The galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others its popular moniker, The Whale Galaxy. Either way, it is similar in size to our own Milky Way. In this sharp color image, the galaxy's yellowish core, dark dust clouds, bright blue star clusters, and red star forming regions are easy to spot. A companion galaxy, the small elliptical NGC 4627 is just above the Whale Galaxy. Faint star streams seen in deep images are the remnants of small companion galaxies disrupted by repeated encounters with the Whale in the distant past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in X-rays.

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[Ann]

It's great to see a fine galaxy take the center stage as the APOD!

NGC 4631 is a very blue, very starforming galaxy. In today's APOD, we can clearly see four distinct stellar populations. There is the yellow bulge, made up of old stars. There is the smooth, grayish-blue intermediate population, which dominates the Whale galaxy's thick disk (the outer part of its disk) as well as in the small companion galaxy, NGC 4627. There is the young blue population, which looks like sprinklings of salt because it is made up of clusters of very luminous stars. And there are the regions of star formation, seen as brilliant pink clouds all along the thin disk of NGC 4631.

The Whale and the Hockey Stick Galaxies.
Photo: Mark Hanson.

Interestingly, the Whale galaxy has another companion, NGC 4656, the Hockey Stick galaxy. What I find most remarkable about the Hockey Stick galaxy is that it seems to be made up of one kind of stellar population only, the young blue stars. In Mark Hanson's photo, a faint yellowing can indeed be seen in the center of NGC 4656 (but note how much yellower the bulge of NGC 4631 is). But no pink nebulas can be spotted in this galaxy, not in this photo and not in most other photos of NGC 4656 either.

It is as if NGC 4656 was the result of one tremendous burst of star formation, so that almost all its stars are the same age.

Ann

[connoisseur]

Spot on, Big Beautiful Whale (BBW) is my favorite too.

[gingermeeder]

I come here frequently being very much a novice in astronomy. But I believe in the beauty of the galaxy and universe and appreciate NASA,sharing with us. You make it so that we can pin it on Pinterest but why can't you give us share buttons for Facebook, Twitter& Google+? I share these all over the place. I can copy the URL's but they don't share the photos on Twitter, they just give a hyperlink. It works okay on Facebook & Google+ the copy & paste of URL's but I'd prefer to share directly from your source. Please give us those additional options. And thank-you for the excellent photography, videos, explanations. This is my one of my all time favorite spot to surf to and ultimately share my gorgeous findings. Peace, keep on going where no human has gone before. ---ginger meeder

[ShaileshS]

Beautiful. Like a mother whale carrying a baby along on her back.

Most edge on pictures I have seen have tons of dust lanes where we can't see the light and beauty of the stars/clusters in the plane of the galaxy. I wonder why there's not much dust in this one and is that unusual or normal ..

[Fred the Cat]

Love this image! In the insert

are those streams or jets? Streams I suppose but in the end another fantastic Pugh. Thanks once again!

[Asterhole]

Beautiful. Like a mother whale carrying a baby along on her back.

Most edge on pictures I have seen have tons of dust lanes where we can't see the light and beauty of the stars/clusters in the plane of the galaxy. I wonder why there's not much dust in this one and is that unusual or normal ..

Or maybe the spouting from the blowhole...?

I would surmise that since NGC4631 is interacting with possibly several smaller galaxies, the dust lanes have been disrupted or obscured by stars we seen in front of the core. Viewed from a more oblique angle would probably more show how much "damage" is being done. Of course if we could view from the inside we might not know that anything was going on at all...

[NGC3314]

Most edge on pictures I have seen have tons of dust lanes where we can't see the light and beauty of the stars/clusters in the plane of the galaxy. I wonder why there's not much dust in this one and is that unusual or normal ..

Very broadly, the dust organization changes between large, massive spirals (with correspondingly rapid orbital motions) and low-mass ones (usually with weaker central bylaws). For smaller spirals (and irregular galaxies), the dust doesn't get organized into long ones, just smaller patches. These leave more space in between so there are more places where we can see to the regions beyond. The larger ones are more photogenic (as well as just plain brighter and bigger imaging targets) so their pictures get splashed all over the place. Some local examples without very organized dust lanes are NGC 55 and NGC 4244.

In addition, some lenticular (S0) galaxies have a disk of stars but almost no dust (this must be for historical reasons in the galaxy), and have no dust lane at all. NGC 3115 is a good example for this.

[Visual_Astronomer]

Nice picture!

I was just looking at the Whale and the Hockey Stick last new moon. They are a couple of my favorite spring-time galaxies; large, bright and very close together.

[Ann]

Beautiful. Like a mother whale carrying a baby along on her back.

Most edge on pictures I have seen have tons of dust lanes where we can't see the light and beauty of the stars/clusters in the plane of the galaxy. I wonder why there's not much dust in this one and is that unusual or normal ..

Don't miss NGC 3447, the ultimate "mother and baby" galaxy. Surely you can't miss the baby at upper left?

NGC 3447, by the way, hosted a supernova Type Ia in 2012, and the galaxy is also close enough to have had its Cepheids measured by the Hubble Telescope in order to figure out the rate of expansion and acceleration of the universe. See http://asterisk.apod.com/viewtopic.php?f=31&t=36006.

Ann

[robgendler]

Martin is a fine astrophotographer but the image is severely clipped. There's absolutely no shadow data. The background is black which is a major flaw in processing.

[geckzilla]

Martin is a fine astrophotographer but the image is severely clipped. There's absolutely no shadow data. The background is black which is a major flaw in processing.

It's there, it's just not stretched. I'd call it an aesthetic choice rather than a flaw.

[Boomer12k]

This image looks more like a Dolphin....

Great Shot.
:---[===] *

[heehaw]

Yellowish core? Does not seem to be at the center. What the heck is it?

[Ann]

Yellowish core? Does not seem to be at the center. What the heck is it?

Click to view full size image

M101 and NGC 5474.
Photo: Thomas V. Davis.

A galaxy is not a solid structure, and the core may "slosh around" inside it. Or, if you'd rather put it like that, the fluffy arms may slosh this way and that around the core.

Check out this picture of M10 and its small satellite galaxy NGC 5474. In both galaxies, the core is visibly displaced from the center.

Ann

[rgendler]

Martin is a fine astrophotographer but the image is severely clipped. There's absolutely no shadow data. The background is black which is a major flaw in processing.

It's there, it's just not stretched. I'd call it an aesthetic choice rather than a flaw.

Well it was a poor (and surprising) processing choice. I really wonder if Martin made this choice or the image was manipulated by APOD staff. Hard to believe someone as experienced as Martin would clip the image that much.

[geckzilla]

Martin is a fine astrophotographer but the image is severely clipped. There's absolutely no shadow data. The background is black which is a major flaw in processing.

It's there, it's just not stretched. I'd call it an aesthetic choice rather than a flaw.

Well it was a poor (and surprising) processing choice. I really wonder if Martin made this choice or the image was manipulated by APOD staff. Hard to believe someone as experienced as Martin would clip the image that much.

Could be that he got a new monitor. I've long had a monitor that shows a lot of brightness in the shadows and images like this look fine on my screen. I've always had to compensate for the general population having much darker monitors by pushing the brightness up to the point that things look a little washed out on my screen. Sometimes I'll still make something that just looks good to me and forget everyone else, though. I always laugh (or at least grin a little) when I see that someone has taken the selection tool and paint bucket to fill the background with pure black. It's so obvious on my screen, but most people clearly can't see it. Martin's picture looks great to me.

[starsurfer]

Martin is a fine astrophotographer but the image is severely clipped. There's absolutely no shadow data. The background is black which is a major flaw in processing.

It's there, it's just not stretched. I'd call it an aesthetic choice rather than a flaw.

Well it was a poor (and surprising) processing choice. I really wonder if Martin made this choice or the image was manipulated by APOD staff. Hard to believe someone as experienced as Martin would clip the image that much.

The image was originally like this and has not been altered by APOD, that is something they never do. For some reason, Martin changed his processing approach last year and all his galaxy images now have really dark backgrounds. I also agree with you as a lot of information for background galaxies is lost.

[starsurfer]

Also stellar streams associated with this galaxy are mentioned, two separate pro-am collaborations detected them separately. Two images show them clearly, this one by Fabian Neyer and another by Karel Teuwen.

[geckzilla]

The image was originally like this and has not been altered by APOD, that is something they never do. For some reason, Martin changed his processing approach last year and all his galaxy images now have really dark backgrounds. I also agree with you as a lot of information for background galaxies is lost.

At least one of the editors has modified images in the past, actually. I think he stopped, though, other than perhaps a color profile going missing from time to time.

[rgendler]

The image was originally like this and has not been altered by APOD, that is something they never do. For some reason, Martin changed his processing approach last year and all his galaxy images now have really dark backgrounds. I also agree with you as a lot of information for background galaxies is lost.

At least one of the editors has modified images in the past, actually. I think he stopped, though, other than perhaps a color profile going missing from time to time.

It's not just the background. The transition of halo to black background is too abrupt and unnatural. We have dozens of computers where I work all with calibrated monitors and the image looks the same for me. So if you think it looks great then I suggest you look into calibrating your monitor or buy a new one.

[geckzilla]

It's not just the background. The transition of halo to black background is too abrupt and unnatural. We have dozens of computers where I work all with calibrated monitors and the image looks the same for me. So if you think it looks great then I suggest you look into calibrating your monitor or buy a new one.

No thanks. I'll take the bias I'm used to. Besides, your monitors are all calibrated to look the same as each other. Of course the image looks the same to you on all of them. In reality, most people don't have that. I looked at my images on a bunch of uncalibrated monitors to get an idea of what I needed to do with them.

Personally, I think you are ... very rigid in your thinking on this. There is nearly always room for improvement, but you seem to see it as some kind of unforgivable flaw. Maybe you should email him instead of commenting here. I don't think he's reading the comments.

[rgendler]

It's not just the background. The transition of halo to black background is too abrupt and unnatural. We have dozens of computers where I work all with calibrated monitors and the image looks the same for me. So if you think it looks great then I suggest you look into calibrating your monitor or buy a new one.

No thanks. I'll take the bias I'm used to. Besides, your monitors are all calibrated to look the same as each other. Of course the image looks the same to you on all of them. In reality, most people don't have that. I looked at my images on a bunch of uncalibrated monitors to get an idea of what I needed to do with them.

Personally, I think you are ... very rigid in your thinking on this. There is nearly always room for improvement, but you seem to see it as some kind of unforgivable flaw. Maybe you should email him instead of commenting here. I don't think he's reading the comments.

No I'm not rigid on this. I have a lot of experience processing images (probably more than you) so I do know what I'm talking about. You seem compelled to defend the processing for some reason I'm not sure about. I know Martin (although I no longer have his contact info) as a great image processor so that is why this image got my attention. As long as my comments are appropriate to the image I think I'll continue to post them here. Sorry if that offends you.

[geckzilla]

No I'm not rigid on this. I have a lot of experience processing images (probably more than you) so I do know what I'm talking about. You seem compelled to defend the processing for some reason I'm not sure about. I know Martin (although I no longer have his contact info) as a great image processor so that is why this image got my attention. As long as my comments are appropriate to the image I think I'll continue to post them here. Sorry if that offends you.

Offends me? All I'm saying is that it's possible he wants his images to look exactly how he processes them. Not how Robert Gendler would have processed them—how he wants them. It's also possible that something else is up.

And I didn't mean for you to stop posting your comments here. I mean that your criticism can't help him if he doesn't see it.

[rgendler]

No I'm not rigid on this. I have a lot of experience processing images (probably more than you) so I do know what I'm talking about. You seem compelled to defend the processing for some reason I'm not sure about. I know Martin (although I no longer have his contact info) as a great image processor so that is why this image got my attention. As long as my comments are appropriate to the image I think I'll continue to post them here. Sorry if that offends you.

Offends me? All I'm saying is that it's possible he wants his images to look exactly how he processes them. Not how Robert Gendler would have processed them—how he wants them. It's also possible that something else is up.

And I didn't mean for you to stop posting your comments here. I mean that your criticism can't help him if he doesn't see it.

Perhaps this is beating a dead horse....but this isn't just any image. It was chosen as Astronomy Picture of the Day. The fact a seriously flawed image was chosen gives credibility to critics of APOD that the very best images aren't always chosen.