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APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 4:06 am
by APOD Robot
The Tadpole Galaxy from Hubble
Explanation: Why does this galaxy have such a long tail? In this stunning vista, based on image data from the
Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral
galaxy Arp 188, the Tadpole Galaxy. The
cosmic tadpole is a mere 420 million light-years distant toward the northern constellation of the Dragon (
Draco). Its
eye-catching tail is about 280 thousand
light-years long and features massive, bright blue star clusters. One
story goes that a more compact intruder galaxy crossed in front of
Arp 188 - from right to left in this view - and was
slung around behind the
Tadpole by their gravitational attraction. During the
close encounter, tidal forces drew out the
spiral galaxy's stars, gas, and dust forming the spectacular tail. The
intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right.
Following its terrestrial
namesake, the
Tadpole Galaxy will likely lose
its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 5:05 am
by VictorBorun
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 5:47 am
by Ann
Let's compare the image posted by Victor with the APOD:
![APOD 15 July annotated.png (895.5 KiB) Viewed 5795 times APOD 15 July annotated.png](./download/file.php?id=50028&t=1&sid=7cab3b09cb419a4a95d9569925f26c37)
Hongjun Pan wrote:
The image of the Tadpole galaxy or Arp 188 or UGC 10214 is carefully studied in this paper, the alternative mechanism for the formation of the Tadpole galaxy is proposed based on the ROTASE model with the information extracted from the image. The Tadpole galaxy and the other two smaller galaxies formed a well isolated local galactic cluster with mutual gravitational interactions. The three galaxies are approaching each other in merging under the gravitational forces. The Tadpole galaxy was initially a normal galaxy with unequal X-matter emission, one side of X-matter emission was strong, but the other side of X-matter emission was weak or had no emission. The Tadpole galaxy initially had a fast motion to the pair of smaller galaxies and had relatively slow rotation, the straight-like arm was generated in this period. When the three galaxies are close enough, the rotation of the Tadpole galaxy increased significantly, and the weak side X-matter emission increased significantly also, so, both arms are strong and clearly visible. Two smaller galaxies are close enough to form a pair with the galactic bridge, and the pair penetrated the Tadpole galaxy through its second (short) arm, seriously distorted the second arm. The strong mutual gravitational tidal forces among the three galaxies pulled the central disc area of the Tadpole galaxy out of its disc plane, changed the Tadpole rotation axis, this caused the morphology of the Tadpole galaxy like a sandwich structure, in which, the short spiral arm is on top, the central bar disc is in the middle, and the other long arm is at the bottom. The galaxy has a right-handed spiral chirality. The local cluster of the three galaxies will merge very soon in the time scale of the universe evolution, the morphology of the cluster will continue to change, the long straight tail will be invisible after all hydrogens are depleted. The two smaller galaxies formed a tadpole galaxy with double clumps; therefore, due to the huge size difference between the two different types of tadpole galaxies and the unique morphology, the current Arp 188 can be viewed as a hybrid of one type of tadpole galaxy parasitic inside of another type of tadpole galaxy, or humorously, a woman bearing a baby of another race through a transplant.
A reflexion here: If the Tadpole galaxy got so messed up when it collided with two really quite small satellite galaxies, then what will happen when the Milky Way collides with the Large Magellanic Cloud (and the Small Cloud presumably following afterwards)?
Sci News wrote:
The Large Magellanic Cloud, a dwarf galaxy located approximately 163,000 light-years away, is on a collision course with the Milky Way with which it will merge in about 2.4 billion years, according to new research. This catastrophic event could wake up our Galaxy’s dormant supermassive black hole, which would begin devouring surrounding gas and increase in size by up to 8 times; the Milky Way’s stellar halo will undergo an equally impressive transformation, becoming 5 times more massive; the merger will also gravitationally eject central disk stars into the halo.
Ann
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 6:47 am
by AVAO
Ann wrote: ↑Mon Jul 15, 2024 5:47 am
[...]
A reflexion here: If the Tadpole galaxy got so messed up when it collided with two really quite small satellite galaxies, then what will happen when the Milky Way collides with the Large Magellanic Cloud (and the Small Cloud presumably following afterwards)?
Sci News wrote:
The Large Magellanic Cloud, a dwarf galaxy located approximately 163,000 light-years away, is on a collision course with the Milky Way with which it will merge in about 2.4 billion years, according to new research. This catastrophic event could wake up our Galaxy’s dormant supermassive black hole, which would begin devouring surrounding gas and increase in size by up to 8 times; the Milky Way’s stellar halo will undergo an equally impressive transformation, becoming 5 times more massive; the merger will also gravitationally eject central disk stars into the halo.
Ann
ThanX Ann
Your question is exciting, although I don't know whether anyone will be interested in it in ... generations of humanity.
Regarding the "scientific" paper cited by Victor, I would treat it with caution. According to my analysis and assessment, apart from a series of assumptions, there are no facts or data-based analysis results in it that would support the assumptions. On the contrary, the assumptions are based on a so-called ROTASE model mechanism, which was developed or invented by one of the authors himself and which is based in particular on a large unknown:
"This model assumes that the central black hole of the galaxy emits anti-gravitational or non-gravitational matter in two opposite directions. The emitted matter is called X-matter because the properties of the emitted matter are completely unknown (the "X" stands for "unknown")."
That means that in my opinion the paper written by two PhDs is hypothetical to support a hypothesis (hypothetical model) of another paper.
But okay. This is my personal opinion. The paper was peer-reviewed by 7 people.
Paper:
https://www.researchgate.net/publicatio ... ic_Merging
Peer-Review:
https://www.sdiarticle5.com/review-history/85417
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 9:36 am
by Ann
AVAO wrote: ↑Mon Jul 15, 2024 6:47 am
Ann wrote: ↑Mon Jul 15, 2024 5:47 am
[...]
A reflexion here: If the Tadpole galaxy got so messed up when it collided with two really quite small satellite galaxies, then what will happen when the Milky Way collides with the Large Magellanic Cloud (and the Small Cloud presumably following afterwards)?
Sci News wrote:
The Large Magellanic Cloud, a dwarf galaxy located approximately 163,000 light-years away, is on a collision course with the Milky Way with which it will merge in about 2.4 billion years, according to new research. This catastrophic event could wake up our Galaxy’s dormant supermassive black hole, which would begin devouring surrounding gas and increase in size by up to 8 times; the Milky Way’s stellar halo will undergo an equally impressive transformation, becoming 5 times more massive; the merger will also gravitationally eject central disk stars into the halo.
Ann
ThanX Ann
Your question is exciting, although I don't know whether anyone will be interested in it in ... generations of humanity.
Regarding the "scientific" paper cited by Victor, I would treat it with caution. According to my analysis and assessment, apart from a series of assumptions, there are no facts or data-based analysis results in it that would support the assumptions. On the contrary, the assumptions are based on a so-called ROTASE model mechanism, which was developed or invented by one of the authors himself and which is based in particular on a large unknown:
"This model assumes that the central black hole of the galaxy emits anti-gravitational or non-gravitational matter in two opposite directions. The emitted matter is called X-matter because the properties of the emitted matter are completely unknown (the "X" stands for "unknown")."
That means that in my opinion the paper written by two PhDs is hypothetical to support a hypothesis (hypothetical model) of another paper.
But okay. This is my personal opinion. The paper was peer-reviewed by 7 people.
Paper:
https://www.researchgate.net/publicatio ... ic_Merging
Peer-Review:
https://www.sdiarticle5.com/review-history/85417
Wowzers!!!
![Shocked :shock:](./images/smilies/icon_eek.gif)
Thanks for the warning, Jac!
Ann
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 11:30 am
by AVAO
Ann wrote: ↑Mon Jul 15, 2024 9:36 am
Wowzers!!!
![Shocked :shock:](./images/smilies/icon_eek.gif)
Thanks for the warning, Jac!
Ann
I like the galaxy
![Wink ;-)](./images/smilies/icon_wink.gif)
... even if it is not mirrored, like the original images in the hubble legacy archive ...
Original data: NASA/ESA jac berne (flickr)
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 1:03 pm
by Christian G.
Small cause, big effect! I’d be curious to see a simulation of how these modest intruders could produce such a dramatic distorsion. If I did not know of the intruders I would have thought that a
large galaxy outside the frame was the cause. In Arp 273 a similarly small intruder (if that's indeed what it is) on top right triggers star formation but that’s mostly all it does apparently, while the major arm distorsions seem to come only from the large galaxy below.
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 1:16 pm
by Chris Peterson
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 1:19 pm
by Christian G.
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
Got it, thanks!
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 1:30 pm
by VictorBorun
AVAO wrote: ↑Mon Jul 15, 2024 6:47 am
"This model assumes that the central black hole of the galaxy emits anti-gravitational or non-gravitational matter in two opposite directions. The emitted matter is called X-matter because the properties of the emitted matter are completely unknown (the "X" stands for "unknown")."
my bad. I googled a picture with the intruder(s) marked, and cut it from the paper I didn't bothered to read. I might have seen "X" letters but mistaken them for X-ray mentioning
![Sad :(](./images/smilies/icon_sad.gif)
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 2:02 pm
by AVAO
Christian G. wrote: ↑Mon Jul 15, 2024 1:19 pm
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
Got it, thanks!
Well. I think the author of today's APOD rotated the original NASA images/data so that the small galaxy in the bottom right is clearly visible in the image. That's why the north orientation of the original NASA images is no longer preserved. What he probably didn't know is that these are displayed mirror-inverted in a FITS viewer ...
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 2:06 pm
by Chris Peterson
AVAO wrote: ↑Mon Jul 15, 2024 2:02 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:19 pm
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
Got it, thanks!
Well. I think the author of today's APOD rotated the original NASA images/data so that the small galaxy in the bottom right is clearly visible in the image. That's why the north orientation of the original NASA images is no longer preserved. What he probably didn't know is that these are displayed mirror-inverted in a FITS viewer ...
Right. The rotation is no big deal. The mirroring is slightly unfortunate.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 3:22 pm
by JustCurious
Why doesn't APOD include the relative size/measurements of ANY and EVERY image, as viewed from earth? (Arc, degrees, or apparent at arms length) I can't help to think this is an important aspect of any astronomical image appreciation. Thanks.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 5:48 pm
by Psnarf
Obquote: [cue klaxon] "Intruder Alert! Intruder Alert!" -Star Trek.
Obquote 2: "What you see is what you get!" -Geraldine, played by Flip Wilson.
Are the spikes from stars within the Milky Way?
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 5:51 pm
by Chris Peterson
Psnarf wrote: ↑Mon Jul 15, 2024 5:48 pm
Obquote: [cue klaxon] "Intruder Alert! Intruder Alert!" -Star Trek.
Obquote 2: "What you see is what you get!" -Geraldine, played by Flip Wilson.
Are the spikes from stars within the Milky Way?
Every star in the image (and even every galaxy) has diffraction spikes. But only the brightest point sources produce spikes that rise above the background noise to become visible. So almost certainly we're only seeing them on nearby stars. Ones in the Milky Way.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 6:26 pm
by Ann
I have to talk about the color of this APOD, because I am, after all, the Color Commentator. And the color of this APOD both delights and bothers me.
When I first saw a picture of the Tadpole Galaxy, it looked like the picture at right. The colors were pale. In the APOD, almost all of the Tadpole Galaxy except the very center is so blue that it could have been made of untold quintillions of Nemophila menziesii, Baby blue eyes!
A Blue Universe, full of Baby blue eyes.
Credit: Hiroki Kondo.
Okay, I'll confess: Hiroki Kondo's image of an entire field of Baby blue eyes in bloom is one of the most achingly lovely and beautiful pictures that I have ever seen. But do things ever get that blue out in space? My answer is that it is at least okay to show the Pleiades as that amazingly blue:
So, yes, all the bright stars of the Pleiades are blue, and the nebulosity surrounding them is certainly blue. But a whole galaxy?
A galaxy that, at best, is made up of stars of all spectral classes, and which could be made of late-type yellow and red stars almost exclusively?
Let's look at some different types of stellar populations. Let's look at ancient and metal-poor populations, and old and metal-rich, and intermediately aged and metal-rich:
Let's look at a galaxy with a very interesting post-starburst population:
Stellar populations of NGC 5394. Credit: NOIRLab.
The white arc is a densely populated post-starburst region of aging and cooling stars.
Please click on the picture of NGC 5394 to see the full size of it. Like all at least reasonably big and star-rich galaxies, NGC 5394 has a yellow center made up of predominantly K-type and M-type stars. NGC 5394 also has two elongated arms, which are blue. One of the arms contains very few and small clusters, which suggests that the stars here are typically class A (like Sirius and Vega) rather than spectral class O and B (like the brilliant blue stars in Orion). The other arm contains a few red emission nebulas, which shows that this arm contains some hot bright stars of spectral classes O and B.
But the most interesting thing about NGC 5394 is its brilliantly white stellar "arc" to the upper right of the yellow center. You could argue that this arc is overexposed and that it really contains hot stars of spectral classes O and B, but that does not seem to be the case. NGC 5494 is not very bright in ultraviolet light, which it would be if the stellar arc was made of hot stars. No, this is clearly a still brilliantly bright and densely populated post-starburst area, where the dominant stars are probably spectral classes F and G.
Please note that the stellar arc is smooth. There are no clusters visible here. That in itself suggests that there are no or very few blue stars here, because young blue stars at least of spectral classes O and B are typically found in clusters.
My point? There are few clusters seen in the Tadpole Galaxy. Yes, there are some clusters there, but large parts of the Tadpole Galaxy look smooth. And not only are they smooth, but also bright. High surface brightness, smooth populations of stars are practically never blue. We should not expect such parts of the Tadpole Galaxy to be blue.
And that was my long-winded way of saying that I think that today's APOD is very beautiful in all its blue glory, but I don't find it entirely realistic!
Ann
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Mon Jul 15, 2024 9:18 pm
by johnnydeep
Intruders? They look to me more like two of the "massive blue clusters" ignited by the now long gone true intruder that created the Tadpole's tail.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Tue Jul 16, 2024 4:06 am
by Avalon
What would an image of the Tadpole by the Webb telescope look like?
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Tue Jul 16, 2024 4:18 am
by Ann
johnnydeep wrote: ↑Mon Jul 15, 2024 9:18 pm
Intruders? They look to me more like two of the "massive blue clusters" ignited by the now long gone intruder that created the Tadpole's tail.
I agree that "Intruder 2" looks just like a massive cluster that formed as a consequence of "Intruder 1's" intrusion into the Tadpole Galaxy.
I read somewhere that rich open cluster NGC 6231 may have formed as a consequence of globular cluster NGC 6397's passage through the Milky Way's disk. Don't know if this is an accepted theory at all - probably not - but I like the idea.
Ann
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Tue Jul 16, 2024 5:43 pm
by johnnydeep
Ann wrote: ↑Tue Jul 16, 2024 4:18 am
johnnydeep wrote: ↑Mon Jul 15, 2024 9:18 pm
Intruders? They look to me more like two of the "massive blue clusters" ignited by the now long gone intruder that created the Tadpole's tail.
I agree that "Intruder 2" looks just like a massive cluster that formed as a consequence of "Intruder 1's" intrusion into the Tadpole Galaxy.
I read somewhere that rich open cluster NGC 6231 may have formed as a consequence of globular cluster NGC 6397's passage through the Milky Way's disk. Don't know if this is an accepted theory at all - probably not - but I like the idea.
Ann
The paper that Victor linked to seems to think that both "1" and "2" are intruders. I suppose there are good reasons, but to me, both still look like massive cluster spawned by some now gone true intruder, though granted, "1" is quite large! But I guess I must be wrong.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Tue Jul 16, 2024 6:07 pm
by Ann
johnnydeep wrote: ↑Tue Jul 16, 2024 5:43 pm
Ann wrote: ↑Tue Jul 16, 2024 4:18 am
johnnydeep wrote: ↑Mon Jul 15, 2024 9:18 pm
Intruders? They look to me more like two of the "massive blue clusters" ignited by the now long gone intruder that created the Tadpole's tail.
I agree that "Intruder 2" looks just like a massive cluster that formed as a consequence of "Intruder 1's" intrusion into the Tadpole Galaxy.
I read somewhere that rich open cluster NGC 6231 may have formed as a consequence of globular cluster NGC 6397's passage through the Milky Way's disk. Don't know if this is an accepted theory at all - probably not - but I like the idea.
Ann
The paper that Victor linked to seems to think that both "1" and "2" are intruders. I suppose there are good reasons, but to me, both still look like massive cluster spawned by some now gone true intruder, though granted, "1" is quite large! But I guess I must be wrong.
I don't think you "must" be wrong at all! I don't think that there is enough evidence to say what really happened to make the Tadpole Galaxy into what it is.
The way I understand it, judging from the paper than Victor linked to, the authors of that paper aren't quite sure that they are right, either.
Ann
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Tue Jul 16, 2024 6:53 pm
by johnnydeep
Ann wrote: ↑Tue Jul 16, 2024 6:07 pm
johnnydeep wrote: ↑Tue Jul 16, 2024 5:43 pm
Ann wrote: ↑Tue Jul 16, 2024 4:18 am
I agree that "Intruder 2" looks just like a massive cluster that formed as a consequence of "Intruder 1's" intrusion into the Tadpole Galaxy.
I read somewhere that rich open cluster NGC 6231 may have formed as a consequence of globular cluster NGC 6397's passage through the Milky Way's disk. Don't know if this is an accepted theory at all - probably not - but I like the idea.
Ann
The paper that Victor linked to seems to think that both "1" and "2" are intruders. I suppose there are good reasons, but to me, both still look like massive cluster spawned by some now gone true intruder, though granted, "1" is quite large! But I guess I must be wrong.
I don't think you "must" be wrong at all! I don't think that there is enough evidence to say what really happened to make the Tadpole Galaxy into what it is.
The way I understand it, judging from the paper than Victor linked to, the authors of that paper aren't quite sure that they are right, either.
Ann
Thanks. I only skimmed the paper.
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Wed Jul 17, 2024 1:14 am
by beryllium732
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
What do you mean by east counterclockwise from north? Can you give me an example with a picture?
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Wed Jul 17, 2024 2:08 am
by Chris Peterson
beryllium732 wrote: ↑Wed Jul 17, 2024 1:14 am
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
What do you mean by east counterclockwise from north? Can you give me an example with a picture?
North is the direction that declination increases in (when north of the celestial equator). East is the direction that RA increases. East is counterclockwise of north, or -90 degrees from north.
_
Re: APOD: The Tadpole Galaxy from Hubble (2024 Jul 15)
Posted: Wed Jul 17, 2024 3:43 am
by Ann
beryllium732 wrote: ↑Wed Jul 17, 2024 1:14 am
Chris Peterson wrote: ↑Mon Jul 15, 2024 1:16 pm
Christian G. wrote: ↑Mon Jul 15, 2024 1:03 pm
p.s. great close-up image AVAO! (but do you mean by "mirrored" that this is not the actual state of the galaxy but an optical effect? I'm not sure I understand)
Astronomical images, by convention, should be presented with east counterclockwise from north. (And ideally with north up, but this convention is often ignored in order to match the geometry of the object to that of the camera, or sometimes for purely aesthetic ends.) This is what we see when we look at the sky, and what telescopes with an even number of reflective surfaces produce. Images presented with with east clockwise from north (as with today's APOD) are considered mirrored (and harder to work with).
What do you mean by east counterclockwise from north? Can you give me an example with a picture?
This is how I learnt it: In astronomical images, north should be up and east to the left.
Ann