APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

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APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by APOD Robot » Thu Jun 06, 2019 4:09 am

Image Messier 63: The Sunflower Galaxy

Explanation: A bright spiral galaxy of the northern sky, Messier 63 is about 25 million light-years distant in the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across. That's about the size of our own Milky Way Galaxy. Known by the popular moniker, The Sunflower Galaxy, M63 sports a bright yellowish core in this sharp telescopic portrait. Its sweeping blue spiral arms are streaked with cosmic dust lanes and dotted with pink star forming regions. A dominant member of a known galaxy group, M63 has faint, extended features that are likely star streams from tidally disrupted satellite galaxies. M63 shines across the electromagnetic spectrum and is thought to have undergone bursts of intense star formation.

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Thu Jun 06, 2019 6:47 am

First of all, I really like today's APOD! :D

M63. Photo: Thomas M. Bisque.
M63. Photo: Bob Holzer.
















However, a picture like today's APOD often inspires me to find other pictures of the same object that shows different aspects and properties of the object in question. The first pictures of M63 that I can remember looked much like the picture at upper left: They were black and white pictures that showed M63 as an overexposed center surrounded by a relatively dark dusty disk with a spiral pattern and some scattered embedded bright knots. The next pictures to arrive were those that looked like the one at right: M63 was now in color, with a bright inner yellow ring with an inner dust lane, surrounding an even brighter yellow nuclear region. The outer ring was still dark and spiral-patterned with scattered knots embedded in it.




M63 in B, V and Hα. Photo: Subaru Telescope.
The inner ring of M63 through 450 and 814 nm filters. ESA/NASA and Hubble.























Interestingly, M63 really is pretty much the same color all over, or relatively so. The Subaru Telescope image makes M63 look rather grey, with small splotches of pink from emission nebulas. The Hubble Telescope image, which enhances the blue and near infrared features of M63 because of the filters used, shows individual stars in the inner ring of M63 as blue grains of sand, scattered among, and alternating with, brown dust lanes.

M63 in infrared light. Photo: Spitzer/Médéric Boquien.
M63 in ultraviolet light. Photo: GALEX.




















Let's take a look at M63 through infrared and ultraviolet filters. In the infrared Spitzer picture at left, we can see that many of the orange splotches correspond to red Hα nebulas seen in the Subaru Telescope image. But the two deep red sources at left in the Spitzer image can't be matched with anything in the Subaru image.

The ultraviolet image from GALEX shows the hot stars and other ultraviolet sources in M63. Just maybe, the two red sources at left in the Spitzer image can be matched with blue sources in the GALEX image. Note the outlying blue arms or stellar streams in the GALEX image, which demonstrates the fact that star formation is taking place well outside the luminous disk of M63.

Messier 63 Stellar Tidal Stream in the Halo.
Credit: Michele Trungadi / Giuseppe Donatiello (process)

Finally, take a look at this set of pictures of the nature of the halo of M63. The top right picture is by far the most interesting to me. M63 is surrounded by extended stellar streams. My guess is that these stellar streams are the remnants of small galaxies that have been cannibalized by M63.


Note in all pictures the small bulge and the small but bright core of M63. If we are to believe Wikipedia, there might be a black hole in the center with a mass of almost a billion solar masses.


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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Boomer12k » Thu Jun 06, 2019 9:54 am

Nice focus and detail...disruption is plain to see...I think.

I have a short exposure M63...colors were brought out for "vibrancy"...

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by De58te » Thu Jun 06, 2019 9:59 am

Is the thick blue region just below the star with the spikes to the right the disrupted satellite galaxy, because it looks like to me it is still on the outer tip of a sparsely populated outer arm of M 63 ?

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by orin stepanek » Thu Jun 06, 2019 12:37 pm

Beautiful coloration in this galaxy! Looks as though it's core is kinda small as compared to similar galaxies! 8-)
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ironwood » Thu Jun 06, 2019 1:02 pm

Whenever I see a picture of a spiral galaxy like this one, my brain always assumes the part of the galaxy at the top of the image is farther away. Like it were lying on a black tabletop and I'm examining it. With effort, I can flip it and see the top side as closer to me like I'm viewing it from underneath. Do we know the true orientation since we can't see individual Cepheid variable stars at 25 million light years?

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Chris Peterson » Thu Jun 06, 2019 1:17 pm

Ironwood wrote:
Thu Jun 06, 2019 1:02 pm
Whenever I see a picture of a spiral galaxy like this one, my brain always assumes the part of the galaxy at the top of the image is farther away. Like it were lying on a black tabletop and I'm examining it. With effort, I can flip it and see the top side as closer to me like I'm viewing it from underneath. Do we know the true orientation since we can't see individual Cepheid variable stars at 25 million light years?
There are tricks for figuring out the orientation, such as noting dust reddening of globulars or bright stars on the periphery. We do see Cepheids out past 100 million light years, but they are of no help in determining orientation because the uncertainties on distance are greater than the diameter of the galaxies we're looking at.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by TheZuke! » Thu Jun 06, 2019 1:30 pm

I'll defer to Chris's explanation over what I was going to say...
and that is if a Doppler image of the galaxy exists, we could surmise which side of the galaxy is spinning toward us, and which side is spinning away,
but now that I think of it, that still wouldn't tell us if we're looking at the "top" or "bottom" of it. B^)
Like Ironwood, I'm "guilty" of the same "black tabletop" bias. Maybe that would change if I could view it from the perspective of me looking up to it from Earth, or not. Instead of the photo being on a computer screen slightly below eye level, separated from familiar (to me) constellations.

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Chris Peterson » Thu Jun 06, 2019 1:41 pm

TheZuke! wrote:
Thu Jun 06, 2019 1:30 pm
I'll defer to Chris's explanation over what I was going to say...
and that is if a Doppler image of the galaxy exists, we could surmise which side of the galaxy is spinning toward us, and which side is spinning away,
but now that I think of it, that still wouldn't tell us if we're looking at the "top" or "bottom" of it. B^)
Like Ironwood, I'm "guilty" of the same "black tabletop" bias. Maybe that would change if I could view it from the perspective of me looking up to it from Earth, or not. Instead of the photo being on a computer screen slightly below eye level, separated from familiar (to me) constellations.
For all but the most face-on galaxies, we can readily observe the direction of rotation from the Doppler shift, as you note. But like you say, that doesn't tell us which way it's tipped relative to us. You can always try rotating the image 180° and seeing if your bias shifts when you do so. I expect it will.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Thu Jun 06, 2019 4:55 pm

De58te wrote:
Thu Jun 06, 2019 9:59 am
Is the thick blue region just below the star with the spikes to the right the disrupted satellite galaxy, because it looks like to me it is still on the outer tip of a sparsely populated outer arm of M 63 ?
M63 in ultraviolet light. Photo: GALEX. Credit: NASA/Wikisky.
Tidal streams in the halo of M63. Photo: Michele Trungadi, Giuseppe Donatiello.

























Maybe, but I think not. Look at the GALEX ultraviolet image at left. As you can see, there are scattered armlets and clumps of blue stars well outside the luminous disk.

I believe that the is a large gaseous halo surrounding M63, but there are also stellar streams in the halo. It wouldn't surprise me if the movements of the stellar streams may compress the gas in certain places, triggering star formation. I would guess that the blue "armlet" outside the luminous disk has undergone star formation recently. On the other hand, the GALEX image does suggest that there is a connection between a spiral arm just "below" a long thick dust lane, and the blue armlet outside the luminous disk.

But take a look at the foursome of images at right. In the upper right panel, you can see that the stellar streams originate in two places, one at upper center, the other one at upper left. The blue armlet, by contrast, can be seen some distance away from these two places of origin, right next to the brightest foreground star in the image.

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by SeedsofEarth » Thu Jun 06, 2019 5:00 pm

Note the thin light streak along the right edge of the galaxy. Is that a more distant edge-on galaxy, or something else?

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by rstevenson » Thu Jun 06, 2019 5:26 pm

SeedsofEarth wrote:
Thu Jun 06, 2019 5:00 pm
Note the thin light streak along the right edge of the galaxy. Is that a more distant edge-on galaxy, or something else?
I think it must be, though it's not very clear. There's a brighter central blob near the middle of what I assume is an extended disk. Here it is, greatly enlarged from a different image of M63 (from a July 2017 APOD, I think.)
M63 detail.jpg
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Thu Jun 06, 2019 5:43 pm

Ironwood wrote:
Thu Jun 06, 2019 1:02 pm
Whenever I see a picture of a spiral galaxy like this one, my brain always assumes the part of the galaxy at the top of the image is farther away. Like it were lying on a black tabletop and I'm examining it. With effort, I can flip it and see the top side as closer to me like I'm viewing it from underneath. Do we know the true orientation since we can't see individual Cepheid variable stars at 25 million light years?
M63, south up. Photo:
Jschulman555 at wikipedia.org.
M63, north up. Photo: Bernard Miller.




















My own answer to that, which might be wrong, is that the lower part of the galaxy (in "north up" pictures) is the part that is closest to us. In south up versions of M63, it will be the upper part of the galaxy that is closer to us.

Dark dust nebula because of interstellar dust reddening.
Source: faculty.virginia.edu.
Bright dust nebula because of interstellar reflection.
Photo: Rogelio Bernal Andreo.






















How can you tell? My answer is the reddening of the dust in the part of the galaxy that is closest to us.

Look at the picture at left of a dust cloud situated in front of a star field. Note how the thin outer parts of the dust cloud blocks some of the light from the stars and makes it first "greener", then yellower. But when the dust gets thicker, the stars behind the dust look first orange, then red. Then the light from the stars gets blocked out altogether, and the center of the dust cloud is a deep dark shade of brown.

But while dust can make starlight redder and also block it altogether, dust can also reflect starlight back at us. Look at the picture at right. Light from the bright star Rigel is lighting up the dust cloud known as the Witch Head Nebula. The Witch Head Nebula is reflecting some of Rigel's light back at us.

That is why I think that if the dust lanes are darker in one half of a galaxy that is inclined to us, then it is the half of the disk with the darker dust lanes that is closer to us. Because a galaxy is typically brighter the closer to the center we get, but if there are dust lanes between us and some of the bright light from the inner disk, then the dust lanes will look very dark. But on the far side of the galaxy, the dust lanes may very well reflect some of the bright light from the inner disk back at us.

The Andromeda Galaxy. Photo: Terry Hancock.
The Andromeda Galaxy. Photo: Mike Lynch.




















We are used to seeing the Andromeda Galaxy the way it looks in the picture at left. You can see that the darkest dust lanes are located along the lower right edge of the disk. That is the part of the galaxy that is closest to us.

But what if we flip the galaxy, so that it is "upside down"? Now the dust lanes are darkest in the upper part of the galaxy. Now it is that part of the galaxy that is closest to us.

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Last edited by Ann on Thu Jun 06, 2019 8:01 pm, edited 1 time in total.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by MarkBour » Thu Jun 06, 2019 7:32 pm

Ann wrote:
Thu Jun 06, 2019 5:43 pm
Ironwood wrote:
Thu Jun 06, 2019 1:02 pm
Whenever I see a picture of a spiral galaxy like this one, my brain always assumes the part of the galaxy at the top of the image is farther away. Like it were lying on a black tabletop and I'm examining it. With effort, I can flip it and see the top side as closer to me like I'm viewing it from underneath. Do we know the true orientation since we can't see individual Cepheid variable stars at 25 million light years?
...
How can you tell? My answer is the reddening of the dust in the part of the galaxy that is closest to us.
...
then it is the half of the disk with the darker dust lanes that is closer to us
...
Ann
I find this persuasive and very clever!

I would be most surprised if it did not hold true ... that statistically, the dust lanes are significantly more contrasting and visible on the near half of the disk. I wonder if anyone has looked at this and if they could verify it (if there are enough galaxies for which we independently know which half of the disk is closer). If it is verified, it would give us a mostly reliable way to guess which half of a distant, inclined, spiral galaxy is the closer half.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by neufer » Thu Jun 06, 2019 8:43 pm

MarkBour wrote:
Thu Jun 06, 2019 7:32 pm

I would be most surprised if it did not hold true ... that statistically, the dust lanes are significantly more contrasting and visible on the near half of the disk. I wonder if anyone has looked at this and if they could verify it (if there are enough galaxies for which we independently know which half of the disk is closer). If it is verified, it would give us a mostly reliable way to guess which half of a distant, inclined, spiral galaxy is the closer half.
Considering that spiral arms almost always spiral in in the direction they rotate,
all one needs is a Doppler measurement to determine which half of the disk is closer.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by MarkBour » Fri Jun 07, 2019 1:03 am

neufer wrote:
Thu Jun 06, 2019 8:43 pm
MarkBour wrote:
Thu Jun 06, 2019 7:32 pm

I would be most surprised if it did not hold true ... that statistically, the dust lanes are significantly more contrasting and visible on the near half of the disk. I wonder if anyone has looked at this and if they could verify it (if there are enough galaxies for which we independently know which half of the disk is closer). If it is verified, it would give us a mostly reliable way to guess which half of a distant, inclined, spiral galaxy is the closer half.
Considering that spiral arms almost always spiral in in the direction they rotate,
all one needs is a Doppler measurement to determine which half of the disk is closer.
I do recall discussing this once before. I believe that's a good approach, though I think there were some rare exceptions, and certainly some disks don't show clear spiral direction (that's not a fair criticism, as we we talking about spiral galaxies). Still, I like the simplicity of Ann's method and would like to find out how well it holds up.

As to having the Doppler for galaxies ... I guess that since determining rotation curves for galaxies is one of the grand interests of astronomers, I'm guessing that many, many galaxies have had detailed measurements of this. Hmmm ... there must be a catalog of these somewhere (?)
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by orin stepanek » Fri Jun 07, 2019 2:48 am

I like to think that the dark side is closer to us as the far side is lit up by the galaxy stars! But That is JMHO! :wink:
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Fri Jun 07, 2019 3:28 am

neufer wrote:
Thu Jun 06, 2019 8:43 pm
MarkBour wrote:
Thu Jun 06, 2019 7:32 pm

I would be most surprised if it did not hold true ... that statistically, the dust lanes are significantly more contrasting and visible on the near half of the disk. I wonder if anyone has looked at this and if they could verify it (if there are enough galaxies for which we independently know which half of the disk is closer). If it is verified, it would give us a mostly reliable way to guess which half of a distant, inclined, spiral galaxy is the closer half.
Considering that spiral arms almost always spiral in in the direction they rotate,
all one needs is a Doppler measurement to determine which half of the disk is closer.
NGC 4622. Credit: NASA and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: Dr. Ron Buta (U. Alabama), Dr. Gene Byrd (U. Alabama)
and Tarsh Freeman (Bevill State Community College)
Almost always, but not quite.
Space telescope wrote:

Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures from the NASA/ESA Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. This Hubble telescope photo of the oddball galaxy is presented by the Hubble Heritage team. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue].
As you say, Art, photographing a galaxy and carefully measuring it (by Doppler shift?) will indeed demonstrate which side of the galaxy is closer.

But in order to check my own hypothesis that simply eyeballing pictures of galaxies and checking the saturation of their dust lanes will give away the galaxies' 3D position in space, I browsed through my trusted The Color Atlas of Galaxies by James D Wray to find inclined galaxies showing dust lanes of various shades of darkness. I had to admit that in some cases, I just couldn't tell which side of the galaxy sported the darker dust lanes.






M81. Photo: Steve Coates.






















But one example where I think that the dark dust lane method will work is M81. Look at the two pictures. Note that the blue smudge of the tiny satellite galaxy Holmberg IX is at top in one image and near bottom in the other. But in both cases, the side of M81 that is farthest from Holmberg IX is the one that shows the darkest dust lanes. I'm going to guess that that is the side that is closest to us.

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by alter-ego » Fri Jun 07, 2019 7:01 am

Ann wrote:
Thu Jun 06, 2019 5:43 pm
...
My own answer to that, which might be wrong, is that the lower part of the galaxy (in "north up" pictures) is the part that is closest to us. In south up versions of M63, it will be the upper part of the galaxy that is closer to us.
...
It wasn't until GAIA measured transverse velocities of Andromeda that the closest edge was known for sure. In that case, the dust opacity argument and apparent trailing edge assumption, coupled with the velocity field, all lead to the conclusion: the NE edge is closest. However, both explanations don't agree for M63. The velocity field for M63 shows the left (east) side is blue-shifted, and red-shifted on the right side. Though classified as a flocculent galaxy, a symmetric two-arm spiral structure is seen in the NIR image. Assuming the trailing-edge rule holds, the nearest edge is the top edge in the north-up view. So what is the right answer? I think it's 50-50. Given the inability of radial Doppler velocity to measure transverse velocity, there are only two galaxies (excluding MW) with full rotation curves measured. They are M31 and M33. Determining the nearest edge for any other galaxy will have some underlying assumption, and therefore speculative.
 
M63 Velocity Field.JPG
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Fri Jun 07, 2019 7:24 am

alter-ego wrote:
Fri Jun 07, 2019 7:01 am
Ann wrote:
Thu Jun 06, 2019 5:43 pm
...
My own answer to that, which might be wrong, is that the lower part of the galaxy (in "north up" pictures) is the part that is closest to us. In south up versions of M63, it will be the upper part of the galaxy that is closer to us.
...
It wasn't until GAIA measured transverse velocities of Andromeda that the closest edge was known for sure. In that case, the dust opacity argument and apparent trailing edge assumption, coupled with the velocity field, all lead to the conclusion: the NE edge is closest. However, both explanations don't agree for M63. The velocity field for M63 shows the left (east) side is blue-shifted, and red-shifted on the right side. Though classified as a flocculent galaxy, a symmetric two-arm spiral structure is seen in the NIR image. Assuming the trailing-edge rule holds, the nearest edge is the top edge in the north-up view. So what is the right answer? I think it's 50-50. Given the inability of radial Doppler velocity to measure transverse velocity, there are only two galaxies (excluding MW) with full rotation curves measured. They are M31 and M33. Determining the nearest edge for any other galaxy will have some underlying assumption, and therefore speculative.
 
M63 Velocity Field.JPG
Bear with me because of my lousy math.

You said:
The velocity field for M63 shows the left (east) side is blue-shifted, and red-shifted on the right side.
I get that.
Assuming the trailing-edge rule holds, the nearest edge is the top edge in the north-up view.
I don't get that.

Consider an old long-playing record, seen at an angle like in the picture at left. Let's assume that the left part of the LP in blue-shifted, because the tracks in it are approaching us, but the right edge of the record is redshifted, because the tracks there are receding from us. Surely that in itself doesn't mean that the top edge of the record is closer to us than the bottom edge? And surely a counter-clockwise rotation doesn't in itself mean that the top edge of a spiral galaxy will be closest to us in north up images?

All right, I guess your reasoning makes sense to everyone who is comfortable with math, but I am not. Could you explain?

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by neufer » Fri Jun 07, 2019 11:27 am

Ann wrote:
Fri Jun 07, 2019 7:24 am



Consider an old long-playing record, seen at an angle like in the picture at left. Let's assume that the left part of the LP in blue-shifted, because the tracks in it are approaching us, but the right edge of the record is redshifted, because the tracks there are receding from us. Surely that in itself doesn't mean that the top edge of the record is closer to us than the bottom edge? And surely a counter-clockwise rotation doesn't in itself mean that the top edge of a spiral galaxy will be closest to us in north up images?
You DO remember how record players work don't you, Ann?

The record rotates CLOCKWISE; i.e., in the direction that the groves spiral out in order that the stylus travels in.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by Ann » Fri Jun 07, 2019 12:33 pm

neufer wrote:
Fri Jun 07, 2019 11:27 am
Ann wrote:
Fri Jun 07, 2019 7:24 am



Consider an old long-playing record, seen at an angle like in the picture at left. Let's assume that the left part of the LP in blue-shifted, because the tracks in it are approaching us, but the right edge of the record is redshifted, because the tracks there are receding from us. Surely that in itself doesn't mean that the top edge of the record is closer to us than the bottom edge? And surely a counter-clockwise rotation doesn't in itself mean that the top edge of a spiral galaxy will be closest to us in north up images?
You DO remember how record players work don't you, Ann?

The record rotates CLOCKWISE; i.e., in the direction that the groves spiral out in order that the stylus travels in.
I remember. Does that mean that the top half of the record is nearer to us than the bottom half?

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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by neufer » Fri Jun 07, 2019 2:42 pm

Click to play embedded YouTube video.
Ann wrote:
Fri Jun 07, 2019 12:33 pm
neufer wrote:
Fri Jun 07, 2019 11:27 am

You DO remember how record players work don't you, Ann?

The record rotates CLOCKWISE; i.e., in the direction that the groves spiral out in order that the stylus travels in.
I remember. Does that mean that the top half of the record is nearer to us than the bottom half?
The upper right is blue shifted towards us and spirals out into the nearer bottom left.
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Re: APOD: Messier 63: The Sunflower Galaxy (2019 Jun 06)

Post by AVAO » Fri Jun 07, 2019 8:32 pm

I have no answer. but I am sure it is 42 ...
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