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Posted: **Mon May 06, 2019 4:09 am**

Virtual Flyby of the Whirlpool Galaxy

Explanation: What would it look like to fly over a spiral galaxy? To help visualize this, astronomers and animators at the Space Telescope Science Institute computed a virtual flyby of the Whirlpool Galaxy (M51) using data and images from the Hubble Space Telescope. At only 25 million light years distant and fully 50 thousand light years across, the Whirlpool is one of the brightest and most picturesque galaxies on the sky. Visible during the virtual flyby are spiral arms dominated by young blue stars, older lighter-colored stars, dark lanes of dust, and bright red emission nebulae. Many galaxies far in the distance can be seen right through M51. The visualization should be considered a time-lapse, because otherwise the speed of the virtual camera would need to be very near the speed of light.

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Posted: **Mon May 06, 2019 4:17 am**

Does not seem to be M51. Where is the companion NGC 5195? Angle of view is not like from Earth

Posted: **Mon May 06, 2019 5:05 am**

Guest wrote: ↑Mon May 06, 2019 4:17 am Does not seem to be M51. Where is the companion NGC 5195? Angle of view is not like from Earth

From the source: The striking symmetry of its spiral pattern may be due to a gravitational interaction with a companion dwarf galaxy, NGC 5195, which is not included in this visualization.

And since it's a simulation, the angle of view can be anything the creator wished it to be.

Posted: **Mon May 06, 2019 5:24 am**

I'm french and I hope you will excuse my poor English.

This video is quite poor too. First, the M51 lost its famous companion NGC 5195. Second, the flyby takes about one minute and the galaxy is thousand light-years large, so our virtual speed is millions time the light speed ! And, during such a long time travel, M51 must rotate...

Posted: **Mon May 06, 2019 7:18 am**

Amazing! It is my only chance to travel faster than light as I approach the Galaxy, isn´t it?

Posted: **Mon May 06, 2019 7:24 am**

This is disappointing in that the image of the galaxy remains a 2-D representation. When I read "virtual fly-by", I was kind of expecting it to reveal a 3-D structure - which of course I knew would have to be inferred rather than observed.

Posted: **Mon May 06, 2019 7:38 am**

Antony Rawlinson wrote: ↑Mon May 06, 2019 7:24 am This is disappointing in that the image of the galaxy remains a 2-D representation. When I read "virtual fly-by", I was kind of expecting it to reveal a 3-D structure - which of course I knew would have to be inferred rather than observed.

Well, that's the problem, in my opinion. We know practically all galaxies from the perspective that we can see them, and although infrared photography can reveal a lot about the inner workings of them, we still only see them from one perspective.

I'm a bit doubtful that virtual flybys like the one in today's APOD can reveal much that photographic stills haven't revealed already. That said, I do appreciate the work that went into this animation, and I do agree that the video is kind of fun to look at.

Ann

Posted: **Mon May 06, 2019 11:48 am**

Wow! I for one; was totally impressed with the virtual flyby! I even liked the fact, that as it got closer that stars from the Whirlpool were starting to freckle the scenery! I give it a 5 star rating!

Posted: **Mon May 06, 2019 11:55 am**

meh.... hollywood does better....

Posted: **Mon May 06, 2019 12:05 pm**

Thanks for all those days in the year with such a high perspective !

Just like mfavret I want that you correct the mistake about the speed of the camera : 100'000 light-years (diameter of M51) x 10 (because the camera is coming from at least 10 times this diameter) = 1 Mlight-years in 1 minute represent a speed of about 500 billions times the speed of light
(10^6*365*24*3600/60= ~500*10^9 times the speed of light !!! ) which is even much more than mfavret said. Thanks again !

Posted: **Mon May 06, 2019 1:38 pm**

Yes, not only is the camera traveling incredibly faster than light, but I have always been fascinated by the way galaxies look in photographs in general and how they would look to space travelers if they were to travel galactic distances. Somewhat difficult to understand because everything we look at here on earth, every object we see, we see in real time and because the size of the objects we look at are small we see them all, in their entirety, instantaneously. But when looking at incredibly large objects in space, for example a face on photo of a galaxy, basically all the light from that galaxy is hitting the camera (or your retina) at almost the same time and the appearance of that galaxy is correct in that it is representative of what that formation looked like X number of (light) years ago. But when we look at a galaxy that is tilted at say 45 degrees, we are not seeing it correctly. The light from a 100 thousand light year diameter galaxy is not getting to us all at the same time. The light from the closer edge of the galaxy is reaching us about 56 thousand years before the light from the far edge is. So our view of the galaxy may be correct for one of the edges, but the view of the other edge is from a different time and is showing us a different position of the stars compared to where the opposite side's ones were at that time. Which also leads me to wonder why, with this time delay, does the galaxy often still looks symmetrical and is not distorted in some way... can anyone with a better knowledge of this give me an answer to that?

Posted: **Mon May 06, 2019 1:49 pm**

astroarchitect1 wrote: ↑Mon May 06, 2019 1:38 pm Yes, not only is the camera traveling incredibly faster than light, but I have always been fascinated by the way galaxies look in photographs in general and how they would look to space travelers if they were to travel galactic distances. Somewhat difficult to understand because everything we look at here on earth, every object we see, we see in real time and because the size of the objects we look at are small we see them all, in their entirety, instantaneously. But when looking at incredibly large objects in space, for example a face on photo of a galaxy, basically all the light from that galaxy is hitting the camera (or your retina) at almost the same time and the appearance of that galaxy is correct in that it is representative of what that formation looked like X number of (light) years ago. But when we look at a galaxy that is tilted at say 45 degrees, we are not seeing it correctly. The light from a 100 thousand light year diameter galaxy is not getting to us all at the same time. The light from the closer edge of the galaxy is reaching us about 56 thousand years before the light from the far edge is. So our view of the galaxy may be correct for one of the edges, but the view of the other edge is from a different time and is showing us a different position of the stars compared to where the opposite side's ones were at that time. Which also leads me to wonder why, with this time delay, does the galaxy often still looks symmetrical and is not distorted in some way... can anyone with a better knowledge of this give me an answer to that?

The difference in one edge to the other caused by light travel time is insignificant when compared with the rotation rate of a galaxy. A time shift of tens of thousands of years and a rotation rate of hundreds of millions of years. So any distortion is probably less than a single pixel at the highest resolution of our images. In other words, we can effectively treat the image as a snapshot at a single time.

Posted: **Mon May 06, 2019 2:09 pm**

mfavret wrote: ↑Mon May 06, 2019 5:24 am
I'm french and I hope you will excuse my poor English. This video is quite poor too.

First, the M51 lost its famous companion NGC 5195.

M51 and NGC 5195 are two pancakes whose relative thicknesses, orientations and 3D positions are not well understood.

To have attempted to include NGC 5195 would have required an excessive amount of speculation.

mfavret wrote: ↑Mon May 06, 2019 5:24 am
Second, the flyby takes about one minute and the galaxy is thousand light-years large, so our virtual speed is millions time the light speed! And, during such a long time travel, M51 must rotate...

A high virtual speed implies a relatively short time period...probably no more than a million years here.

Galaxies require HUNDREDS of millions of years to rotate!

Because there are no relativistic distortions this is (as stated) a time lapse from a space craft traveling perhaps only a fifth the speed of light yet,still, much much faster than ~ 0.001 c velocity stars whose apparent motions are almost entirely due to the motion of the spacecraft.

Posted: **Mon May 06, 2019 2:11 pm**

I think astroarchitect is asking a relevant question. Even a 50,000 lightyear diameter should show a few degrees of rotation and thereby distort slightly the photographic view. Can someone with facts show why even the larger galaxies still show pure symmetry?

Posted: **Mon May 06, 2019 2:16 pm**

mfavret wrote: ↑Mon May 06, 2019 5:24 am I'm french and I hope you will excuse my poor English.

This video is quite poor too. First, the M51 lost its famous companion NGC 5195. Second, the flyby takes about one minute and the galaxy is thousand light-years large, so our virtual speed is millions time the light speed ! And, during such a long time travel, M51 must rotate...

We should treat this as a time-lapse image. If the total camera travel was on the order of 500,000 ly, and we were traveling at a practical, largely non-relativistic speed of 0.1 c, the actual data would span 5 million years. In that time the galaxy rotates just a few percent of a full rotation- probably not enough to be apparent compared with the much larger shift in viewpoint created by the moving camera.

Posted: **Mon May 06, 2019 2:20 pm**

gps35n wrote: ↑Mon May 06, 2019 2:11 pm I think astroarchitect is asking a relevant question. Even a 50,000 lightyear diameter should show a few degrees of rotation and thereby distort slightly the photographic view. Can someone with facts show why even the larger galaxies still show pure symmetry?

A 50,000 ly time shift from the front to back edge, with a galaxy that has a rotation time of 150 million years, means a rotation distortion on the order of 0.1 degrees. That's not enough to be visible at all to our eye. It has no visual impact on the structure or symmetry at the level of an image of the entire galaxy.

Posted: **Mon May 06, 2019 2:35 pm**

My initial thought was that it appeared that we were flying over a small lake.Fantasy just can't always replace the frustration of knowing we are but a speck in all this majesty and the nearest star is out of our reaches.

Posted: **Mon May 06, 2019 4:03 pm**

I'm kind of puzzled by the last sentence. 'The visualization should be considered a time-lapse, because otherwise the speed of the virtual camera would need to be very near the speed of light.' Let's suppose that the virtual camera speed was filmed at very near the speed of light. That would mean that the flyby video speed would last more than 50,000 years. It seems to me that it lasted about a minute. A year of film would have to speeded up 525,600 times in 1 minute. Then that would be multiplied by 50,000. My calculater doesn't have enough digits to calculate that. I suppose it is some 5 x 10^10 times the speed of light.

Posted: **Mon May 06, 2019 4:12 pm**

De58te wrote: ↑Mon May 06, 2019 4:03 pm I'm kind of puzzled by the last sentence. 'The visualization should be considered a time-lapse, because otherwise the speed of the virtual camera would need to be very near the speed of light.' Let's suppose that the virtual camera speed was filmed at very near the speed of light. That would mean that the flyby video speed would last more than 50,000 years. It seems to me that it lasted about a minute. A year of film would have to speeded up 525,600 times in 1 minute. Then that would be multiplied by 50,000. My calculater doesn't have enough digits to calculate that. I suppose it is some 5 x 10^10 times the speed of light.

It's very complex. Keep in mind that from the moving observer's standpoint, it's possible to traverse tens of thousands of light years in an arbitrarily short time. Including in a single minute. But if you were filming out the front of your spacecraft, traveling at a highly relativistic speed, you'd see nothing at all like what this video shows.

Posted: **Mon May 06, 2019 5:12 pm**

They've got the sound wrong ...

Click to play embedded YouTube video.

Posted: **Mon May 06, 2019 5:15 pm**

Philippe Delacrétaz wrote: ↑Mon May 06, 2019 12:05 pm Thanks for all those days in the year with such a high perspective !

Just like mfavret I want that you correct the mistake about the speed of the camera : 100'000 light-years (diameter of M51) x 10 (because the camera is coming from at least 10 times this diameter) = 1 Mlight-years in 1 minute represent a speed of about 500 billions times the speed of light
(10^6*365*24*3600/60= ~500*10^9 times the speed of light !!! ) which is even much more than mfavret said. Thanks again !

I said about thousands years without any computation (just a reference to the size of such a galaxy) but with the message of Philippe Delacrétaz, it's more about a million years. Considering that the sun rotates one tour in about 240 million years, during the travel, if in M51, it will rotate about 1.5° but inner stars rotate much more faster so I think that some rotation (at different rates regarding the distance from the center) could be seen.

I have seen such an animation in an old video clip (2006?) still on my PC, nammed "galaxy_flythrouh.avi". You can find it here (it's frome ESO) : https://www.youtube.com/watch?v=4vxpTIWCKFs. During the fly out the Milky Way it seems that the speed is not very different but the rotation is obvious. So one of the two videos is not realistic… or both ?

Posted: **Mon May 06, 2019 5:21 pm**

mfavret wrote: ↑Mon May 06, 2019 5:15 pm
Philippe Delacrétaz wrote: ↑Mon May 06, 2019 12:05 pm Thanks for all those days in the year with such a high perspective !

Just like mfavret I want that you correct the mistake about the speed of the camera : 100'000 light-years (diameter of M51) x 10 (because the camera is coming from at least 10 times this diameter) = 1 Mlight-years in 1 minute represent a speed of about 500 billions times the speed of light
(10^6*365*24*3600/60= ~500*10^9 times the speed of light !!! ) which is even much more than mfavret said. Thanks again !
I said about thousands years without any computation (just a reference to the size of such a galaxy) but with the message of Philippe Delacrétaz, it's more about a million years. Considering that the sun rotates one tour in about 240 million years, during the travel, if in M51, it will rotate about 1.5° but inner stars rotate much more faster so I think that some rotation (at different rates regarding the distance from the center) could be seen.

The rotation rate of the inner stars is slowest, with the regions away from the center all rotating at about the same rate. This is due to the dark matter halo of the galaxy. (But note that this is the speed as distance/time, not angle/time.)

Posted: **Mon May 06, 2019 11:30 pm**

Maybe it is another Whirlpool galaxy?

This looks nothing like M51...at all...it is not the perspective.

As a simulation, or a representation, it is a "CROPPED" view...with much missing.

I can see some similarity in the "forked" dust lanes at the bottom of this simulation...but that is about all...

Eagerly awaiting a more complete representation...

:---[===] *

Posted: **Mon May 06, 2019 11:55 pm**

Boomer12k wrote: ↑Mon May 06, 2019 11:30 pm Maybe it is another Whirlpool galaxy?

This looks nothing like M51...at all...it is not the perspective.

As a simulation, or a representation, it is a "CROPPED" view...with much missing.

I can see some similarity in the "forked" dust lanes at the bottom of this simulation...but that is about all...

Eagerly awaiting a more complete representation...

:---[===] *

It is M51.

Posted: **Tue May 07, 2019 2:45 am**

Boomer12k wrote: ↑Mon May 06, 2019 11:30 pm Maybe it is another Whirlpool galaxy?

This looks nothing like M51...at all...it is not the perspective.

As a simulation, or a representation, it is a "CROPPED" view...with much missing.

I can see some similarity in the "forked" dust lanes at the bottom of this simulation...but that is about all...

Eagerly awaiting a more complete representation...

:---[===] *

Yes, it is "cropped", but it is M51, or M51a (NGC5194) to be more precise. M51b (NGC 5195) is not included in the visualization. See the link "virtual flyby" for more information.

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APOD: Virtual Flyby of the Whirlpool Galaxy (2019 May 06)

APOD: Virtual Flyby of the Whirlpool Galaxy (2019 May 06)

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