APOD: The Galaxy, the Jet, and a Famous... (2023 May 04)

[beryllium732]

How would it be living in that galaxy? Would the nightsky be black with lots of stars but no galaxy disc in it with an expeption of a big jet sticking out in the nightsky?

add the boredom of red-and-dead star population: almost every star is a little smaller and yellower than Sun or is a red dwarf and not seen at all

Is it so! Imagine the civilizations in that galaxy not having the same sight as we does in ours. The inspirations and imagtinations shaping their cultures and use of star maps we have been spoiled with and they don't have that luxury. And the big blob in the central of the galaxy would spoil the dark night for them. I feel so sorry for them!

add the boredom of red-and-dead star population: almost every star is a little smaller and yellower than Sun or is a red dwarf and not seen at all

You are sure about that? Wouldn't there be a lot of Betelgeuses in the nightsky too except red dwarfs and more reddish yellow suns?

There are no (or at least extremely few) Betelgueses in the skies of any putative planet inside M87.

Betelgeuse is a young massive star. Only massive stars can become red supergiants thousands of times brighter than the Sun, and such massive stars die young. And since M87 is absolutely overwhelmingly dominated by old stars, there will be no Betelgeuses among them.

Here is how you can tell old modest red giant stars from young brilliant red supergiants. First, let's look at some young red supergiants, which are typically surrounded by many bright blue stars:

Red (actually yellow-orange) supergiant Antares submerged in nebulosity and surrounded by several blue stars. Antares is believed to be some 15 million years old. Image: Wikisky.

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Double Cluster of Perseus Tommy Lease.png

The Double Cluster of Perseus. At least 5 and possibly 7 red supergiants stand out
among the blue stars. The clusters are believed to be some 12 million years old.
Image credit: Tommy Lease.

Bright red giant BM Sco stands out among the blue stars of M6, the Butterfly Cluster. BM Sco is a bright giant but not a supergiant, since M6 is at least 50 million years old. Image: Giuseppe Donatiello

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Old red stars keep a different company than the brilliant red supergiants with their entourage of blue stars:

Old open cluster NGC 2158. This cluster is believed to be 2 billion years old. Image: SDSS.

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Old open cluster Trumpler 5 by zirl.png

Old open cluster Trumpler 5. This cluster is similar in age to the Sun.
Image: zirl.

Red supergiants are young massive stars, and they are typically surrounded by a large number of bright blue stars. Old red stars are much more modest, much less bright, don't stand out very much, and are not surrounded by blue stars (unless there happens to be one or more blue stragglers around).

Take a look at cluster NGC 2158. This cluster may be some 14,000 light-years away, and I found a Gaia parallax for the brightest red star which suggests that the V luminosity of this star is some ~68 times solar. That is not bad, but it is so very far from the brightness of a supergiant.

As for Trumpler 5, there is a star (at lower left) that stands out. However, this is a foreground star, at "only" some 3,400 light-years, whereas Trumpler 5 proper is at a distance of some 11,000 light-years. The V luminosity of the foreground star is some ~140 solar luminosities. That is not bad, but it is still in no way comparable to a supergiant.

By comparison, HD 14270, one of the red supergiants in the Double Cluster, has a V luminosity of some 3,100 solar. AS for BM Sco, the bright red non-supergiant, its V luminosity is some 1,000 solar.

Ann

Very interesting thank you!

Those blue stars in the two old clusters the NGC 2158 and Trumpler 5 is foreground blue stars which lies nearer to Earth?

Which is the typical stellar classification of the stars in the M87 galaxy? Does it have a lot more red dwarfs or more G-type stars like our sun? Does it have any star creating nebulas left? And by the way speaking of nebulas are the pink ionized nebulas in certain galaxies the same as our nebulas for example the horse nebula?

Their "Milky Way" would be a "Milky Blob" with the size and position depending on the location of the observer. The jet would not be visible.

But if a human on an Earth copy in M87 blocked the stars and let eyes adapt… still no jet?
But if the jet goes right their way and is 1000 times as bright as for Earth 1?

M87 is easily seen in a telescope, but its jet is not visible. Neither getting closer nor magnification makes things brighter.

So it is invisible even for the civlization that would reside in the galaxy. That's too bad it would be an awesome sight indeed!

[Chris Peterson]

How would it be living in that galaxy? Would the nightsky be black with lots of stars but no galaxy disc in it with an expeption of a big jet sticking out in the nightsky?

add the boredom of red-and-dead star population: almost every star is a little smaller and yellower than Sun or is a red dwarf and not seen at all

Is it so! Imagine the civilizations in that galaxy not having the same sight as we does in ours. The inspirations and imagtinations shaping their cultures and use of star maps we have been spoiled with and they don't have that luxury. And the big blob in the central of the galaxy would spoil the dark night for them. I feel so sorry for them!

That blob would be of similar brightness as the Milky Way is to us here. So it wouldn't ruin the night sky, only provide a structure to it, which like the Milky Way, might contribute to their culture and folklore.

[Ann]

How would it be living in that galaxy? Would the nightsky be black with lots of stars but no galaxy disc in it with an expeption of a big jet sticking out in the nightsky?

add the boredom of red-and-dead star population: almost every star is a little smaller and yellower than Sun or is a red dwarf and not seen at all

Is it so! Imagine the civilizations in that galaxy not having the same sight as we does in ours. The inspirations and imagtinations shaping their cultures and use of star maps we have been spoiled with and they don't have that luxury. And the big blob in the central of the galaxy would spoil the dark night for them. I feel so sorry for them!

You are sure about that? Wouldn't there be a lot of Betelgeuses in the nightsky too except red dwarfs and more reddish yellow suns?

There are no (or at least extremely few) Betelgueses in the skies of any putative planet inside M87.

Betelgeuse is a young massive star. Only massive stars can become red supergiants thousands of times brighter than the Sun, and such massive stars die young. And since M87 is absolutely overwhelmingly dominated by old stars, there will be no Betelgeuses among them.

Here is how you can tell old modest red giant stars from young brilliant red supergiants. First, let's look at some young red supergiants, which are typically surrounded by many bright blue stars:

Red (actually yellow-orange) supergiant Antares submerged in nebulosity and surrounded by several blue stars. Antares is believed to be some 15 million years old. Image: Wikisky.

---

Double Cluster of Perseus Tommy Lease.png

The Double Cluster of Perseus. At least 5 and possibly 7 red supergiants stand out
among the blue stars. The clusters are believed to be some 12 million years old.
Image credit: Tommy Lease.

Bright red giant BM Sco stands out among the blue stars of M6, the Butterfly Cluster. BM Sco is a bright giant but not a supergiant, since M6 is at least 50 million years old. Image: Giuseppe Donatiello

---

Old red stars keep a different company than the brilliant red supergiants with their entourage of blue stars:

Old open cluster NGC 2158. This cluster is believed to be 2 billion years old. Image: SDSS.

---

Old open cluster Trumpler 5 by zirl.png

Old open cluster Trumpler 5. This cluster is similar in age to the Sun.
Image: zirl.

Red supergiants are young massive stars, and they are typically surrounded by a large number of bright blue stars. Old red stars are much more modest, much less bright, don't stand out very much, and are not surrounded by blue stars (unless there happens to be one or more blue stragglers around).

Take a look at cluster NGC 2158. This cluster may be some 14,000 light-years away, and I found a Gaia parallax for the brightest red star which suggests that the V luminosity of this star is some ~68 times solar. That is not bad, but it is so very far from the brightness of a supergiant.

As for Trumpler 5, there is a star (at lower left) that stands out. However, this is a foreground star, at "only" some 3,400 light-years, whereas Trumpler 5 proper is at a distance of some 11,000 light-years. The V luminosity of the foreground star is some ~140 solar luminosities. That is not bad, but it is still in no way comparable to a supergiant.

By comparison, HD 14270, one of the red supergiants in the Double Cluster, has a V luminosity of some 3,100 solar. AS for BM Sco, the bright red non-supergiant, its V luminosity is some 1,000 solar.

Ann

Very interesting thank you!

Those blue stars in the two old clusters the NGC 2158 and Trumpler 5 is foreground blue stars which lies nearer to Earth?

Which is the typical stellar classification of the stars in the M87 galaxy? Does it have a lot more red dwarfs or more G-type stars like our sun? Does it have any star creating nebulas left? And by the way speaking of nebulas are the pink ionized nebulas in certain galaxies the same as our nebulas for example the horse nebula?

As for the blue stars seen near the outskirts of NGC 2158, they are very, very likely outlying members of much younger (c. 175 million years old) and considerably more nearby (around 3,000 light-years) cluster M35.

NGC 2158. Credit: SDSS.

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Clusters M35 (left) and NGC 2158 (lower right).
Credit: Rolf Wahl Olsen.

I checked the most obvious of the blue stars at the outskirts of NGC 2158, and the distance to it jibes perfectly with the distance to M35, some 3,000 light-years. The brightness of this star, TYC 1864-1197-1, coupled with its distance, shows that its true brightness is some 30 solar luminosities. In other words, this is a star similar to Sirius and Vega. So yes, indeed, this is a foreground star seen in front of NGC 2158.

I checked one of the blue stars near the outskirts of Trumpler 5 too, and indeed, that star is also a foreground star.

As for the blue stars seen inside NGC 2158, one or even two of them might be blue stragglers, stars that have "stolen" gas from another star and become brighter and bluer.

Sometimes it is hard to make head or tails of blue stars seen in or extremely near old clusters. Take cluster M67, whose age is believed to be some 4 billion years. There is a blue star at the outskirts of this cluster, and it looks as if it might belong there!

M67. The blue star at lower right sticks out like a sore thumb. Credit: Palomar Observatory / STScI / WikiSky.

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Here the blue star of M67 is seen at upper left. Credit: SDSS.

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Is this blue star a true member of the cluster? I'm not sure. I checked its distance, proper motion and radial velocity and compared it to the red star seen next to it. The red star had pretty much the same proper motion, but it seemed to be a bit closer, and its radial velocity was much higher. So maybe the blue star is a background object and not a member of M67?

You asked about the typical stellar classification of stars in M87. That prize definitely goes to the M-type dwarfs! Little red stars that live extremely long lives and burn their candles almost painfully slowly.

Proper motion of Barnard's Star, a small red dwarf star 6 light-years from the Earth. Credit: Rick Johnson.

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The picture above shows Barnard's Star, a star of spectral class M4V at a distance of only 6 light-years, which makes it one of the absolutely closest stars to the Earth. Despite its proximity, this faint star is invisible to the eye.

Stars similar to Barnard's Star certainly abound in M87. Since the mass of Barnard's Star is only 16% of the Sun's mass, it may still be a little bit on the faint and lightweight side even for the stellar population of M87. At a wild guess, I'd say that the most typical mass of stars in M87 may be 40% or maybe even 50% of the Sun's mass.

The second most common type of stars in M87, again if you ask me, is probably the white dwarfs, burnt-out remnants of stars that have used up all their available stellar fuel, cast off their outer layers, bared their cores, and started the process of radiating all the heat of their cores into the surrounding interstellar medium.

White dwarf star Sirius B next to bright A-type star Sirius. Credit: NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

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You asked about G-type stars. They are so very much less common than the red dwarf stars even in the Milky, and they are not going to be proportionally more common in M87. In the Milky Way, I believe that the G-type stars make up some 5% of all stars in our galaxy. In M87, the proportion may be even lower, since M87 by all accounts has not had any significant star formation for billions of years.


However...

The skies of a putative planet inside M87 may be lit up by one or even more globular clusters. In the Milky Way, there are only some 200 globular clusters all told, and the brightest of them is only fourth magnitude (from the Earth's perspective), so it doesn't stand out. But M87 has some
15,000 globular clusters.

Wikipedia wrote:

Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy in the constellation Virgo that contains several trillion stars. One of the largest and most massive galaxies in the local universe, it has a large population of globular clusters — about 15,000 compared with the 150–200 orbiting the Milky Way(...)

Since the skies of a putative planet inside M87 are likely to be comparatively featureless and "the same all over", maybe one or two globular clusters will stand out?

M87. The little white dots scattered all over the image are globular clusters. Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics) and E. Baltz (Stanford University)

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Artist's impression of the skies inside Milky Way globular cluster 47 Tuc. There are two concentrations of light in this sky. The brightest one is the core of 47 Tuc itself, while the fainter one (at upper left) is another globular cluster, NGC 362. The dust lanes seen faintly at left belong to the Milky Way. Illustration: William Harris and Jeremy Webb

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You asked if the pink nebulas of other galaxies are similar to the pink nebulas of the Milky Way. Yes, they are indeed the same kind of objects. They are gas clouds that are being ionized by the ultraviolet light of the hot stars that have recently been formed from these very clouds (or are still being formed from them).

Starforming pink nebulas in the dust lane of the Milky Way. Credit: JUAN CARLOS CASADO (STARRYEARTH.COM) / SCIENCE PHOTO LIBRARY

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Starforming pink nebulas in galaxy M81. Credit: Subaru Telescope (NAOJ), Hubble Space Telescope; Processing & Copyright: Roberto Colombari & Robert Gendler

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Ann

Edit: One more thought. On the Earth, we can't see the center of our galaxy because the thick central Milky Way dust lane blocks our view. But in M87 there are no dust lanes. There is dust, certainly, but there are no dust lanes.

Perhaps the center of M87 shines brightly in the skies of all planets inside this galaxy? Like having a bright fuzzy patch in the sky that is always there?

Click to view full size image

Maybe this fuzz patch with a brilliantly bright central point of light is always there as a constant feature of the night skies of planets of M87?

Ann

[VictorBorun]

How would it be living in that galaxy? Would the nightsky be black with lots of stars but no galaxy disc in it with an expeption of a big jet sticking out in the nightsky?

But if a human on an Earth copy in M87 blocked the stars and let eyes adapt… still no jet?
But if the jet goes right their way and is 1000 times as bright as for Earth 1?

M87 is easily seen in a telescope, but its jet is not visible. Neither getting closer nor magnification makes things brighter.

However being closer to the axis of the jet must make it look brighter (as well as shorter and more violet-shifted in its spectrum).

Earth is in fact off that axis by 17° ± 2° and HST does struggle to get the jet in a long exposure with a colour mix exaggerating short-wave channel:

[AVAO]

The Galaxy, the Jet, and a Famous Black Hole

...Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of enormous energy driving the relativistic jets from the center of active galaxy M87...

Just 4 fun 1:1 infill of the BH:

ROLLOVER:

Click to view full size image 1 or image 2

Biggggg:https://live.staticflickr.com/65535/528 ... e732_o.jpg
Note the black dot in the middle and click on it with the magnifying glass. You will then see the BH in 1:1 format. Wait 3 seconds for sharpness.

Recognize the twists in the main beam:

Bigg:https://live.staticflickr.com/65535/528 ... a774_o.jpg

Biggggg:https://live.staticflickr.com/65535/528 ... d283_o.jpg
Click on the center of the BH and notice the two outflows in opposite direction of the main jet.


Bigg:https://live.staticflickr.com/65535/528 ... 1826_o.jpg

Original Image Sources:
https://www.researchgate.net/figure/The ... _336767798
https://de.wikipedia.org/wiki/Messier_8 ... ll_jpg.jpg
https://hubblesite.org/contents/media/i ... Image.html
https://www.eso.org/public/germany/images/eso2305a/
https://www.researchgate.net/figure/M87 ... _323594901
https://astronomy.com/news/2021/12/snap ... wisted-jet

[beryllium732]

As for the blue stars seen near the outskirts of NGC 2158, they are very, very likely outlying members of much younger (c. 175 million years old) and considerably more nearby (around 3,000 light-years) cluster M35.

NGC 2158. Credit: SDSS.

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M35 NGC 2158 Rolf Wahl Olsen.png

Clusters M35 (left) and NGC 2158 (lower right).
Credit: Rolf Wahl Olsen.

I checked the most obvious of the blue stars at the outskirts of NGC 2158, and the distance to it jibes perfectly with the distance to M35, some 3,000 light-years. The brightness of this star, TYC 1864-1197-1, coupled with its distance, shows that its true brightness is some 30 solar luminosities. In other words, this is a star similar to Sirius and Vega. So yes, indeed, this is a foreground star seen in front of NGC 2158.

I checked one of the blue stars near the outskirts of Trumpler 5 too, and indeed, that star is also a foreground star.

As for the blue stars seen inside NGC 2158, one or even two of them might be blue stragglers, stars that have "stolen" gas from another star and become brighter and bluer.

Sometimes it is hard to make head or tails of blue stars seen in or extremely near old clusters. Take cluster M67, whose age is believed to be some 4 billion years. There is a blue star at the outskirts of this cluster, and it looks as if it might belong there!

M67. The blue star at lower right sticks out like a sore thumb. Credit: Palomar Observatory / STScI / WikiSky.

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Here the blue star of M67 is seen at upper left. Credit: SDSS.

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Is this blue star a true member of the cluster? I'm not sure. I checked its distance, proper motion and radial velocity and compared it to the red star seen next to it. The red star had pretty much the same proper motion, but it seemed to be a bit closer, and its radial velocity was much higher. So maybe the blue star is a background object and not a member of M67?

You asked about the typical stellar classification of stars in M87. That prize definitely goes to the M-type dwarfs! Little red stars that live extremely long lives and burn their candles almost painfully slowly.

Proper motion of Barnard's Star, a small red dwarf star 6 light-years from the Earth. Credit: Rick Johnson.

---

The picture above shows Barnard's Star, a star of spectral class M4V at a distance of only 6 light-years, which makes it one of the absolutely closest stars to the Earth. Despite its proximity, this faint star is invisible to the eye.

Stars similar to Barnard's Star certainly abound in M87. Since the mass of Barnard's Star is only 16% of the Sun's mass, it may still be a little bit on the faint and lightweight side even for the stellar population of M87. At a wild guess, I'd say that the most typical mass of stars in M87 may be 40% or maybe even 50% of the Sun's mass.

The second most common type of stars in M87, again if you ask me, is probably the white dwarfs, burnt-out remnants of stars that have used up all their available stellar fuel, cast off their outer layers, bared their cores, and started the process of radiating all the heat of their cores into the surrounding interstellar medium.

White dwarf star Sirius B next to bright A-type star Sirius. Credit: NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

---

You asked about G-type stars. They are so very much less common than the red dwarf stars even in the Milky, and they are not going to be proportionally more common in M87. In the Milky Way, I believe that the G-type stars make up some 5% of all stars in our galaxy. In M87, the proportion may be even lower, since M87 by all accounts has not had any significant star formation for billions of years.


However...

The skies of a putative planet inside M87 may be lit up by one or even more globular clusters. In the Milky Way, there are only some 200 globular clusters all told, and the brightest of them is only fourth magnitude (from the Earth's perspective), so it doesn't stand out. But M87 has some
15,000 globular clusters.

Wikipedia wrote:

Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy in the constellation Virgo that contains several trillion stars. One of the largest and most massive galaxies in the local universe, it has a large population of globular clusters — about 15,000 compared with the 150–200 orbiting the Milky Way(...)

Since the skies of a putative planet inside M87 are likely to be comparatively featureless and "the same all over", maybe one or two globular clusters will stand out?

M87. The little white dots scattered all over the image are globular clusters. Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics) and E. Baltz (Stanford University)

---

Artist's impression of the skies inside Milky Way globular cluster 47 Tuc. There are two concentrations of light in this sky. The brightest one is the core of 47 Tuc itself, while the fainter one (at upper left) is another globular cluster, NGC 362. The dust lanes seen faintly at left belong to the Milky Way. Illustration: William Harris and Jeremy Webb

---

You asked if the pink nebulas of other galaxies are similar to the pink nebulas of the Milky Way. Yes, they are indeed the same kind of objects. They are gas clouds that are current or former birth places of hot stars that are being ionized by the ultraviolet radiation of of young or newborn hot stars.

Starforming pink nebulas in the dust lane of the Milky Way. Credit: JUAN CARLOS CASADO (STARRYEARTH.COM) / SCIENCE PHOTO LIBRARY

---

Starforming pink nebulas in galaxy M81. Credit: Subaru Telescope (NAOJ), Hubble Space Telescope; Processing & Copyright: Roberto Colombari & Robert Gendler

---

Ann

Edit: One more thought. On the Earth, we can't see the center of our galaxy because the thick central Milky Way dust lane blocks our view. But in M87 there are no dust lanes. There is dust, certainly, but there are no dust lanes.

Perhaps the center of M87 shines brightly in the skies of all planets inside this galaxy? Like having a bright fuzzy patch in the sky that is always there?

Click to view full size image

Maybe this fuzz patch with a brilliantly bright central point of light is always there as a constant feature of the night skies of planets of M87?

I always hugely thank you for your detailed and informational answers! I am learning so much thanks to you! It would be really awesome if JWST could peak or peer into M87 not the black hole itself but the stars and layers around it and see if it's completely dead or does have any form of star formation even though most of the galaxy is more or less dead. Maybe we are writing it off as almost dead when it really isn't?

[VictorBorun]

The Galaxy, the Jet, and a Famous Black Hole
...Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of enormous energy driving the relativistic jets from the center of active galaxy M87...

Just 4 fun 1:1 infill of the BH:
ROLLOVER:

Click to view full size image 1 or image 2

4 fun or 4 pulling our leg? Prove me wrong, but I thought the jet up to the bend is a few thousand ly while M87* is a few light days, of scale like 1 to million

Correcting update: my bad, I misunderstood the word ROLLOVER. It's a series, and the orange doughnut is just a symbol at the start of that series

[AVAO]

The Galaxy, the Jet, and a Famous Black Hole
...Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of enormous energy driving the relativistic jets from the center of active galaxy M87...

Just 4 fun 1:1 infill of the BH:
ROLLOVER:

Click to view full size image 1 or image 2

4 fun or 4 pulling our leg? Prove me wrong, but I thought the jet up to the bend is a few thousand ly while M87* is a few light days, of scale like 1 to million

Correcting update: my bad, I misunderstood the word ROLLOVER. It's a series, and the orange doughnut is just a symbol at the start of that series

Hmmm. You're right. I measured againand lo and behold! The scaling of the poster of the scientific publication with 44 authors ( https://www.researchgate.net/figure/The ... _336767798 ) can not really be correct, if the scalings from ESO ( https://www.eso.org/public/images/eso2208-eht-mwe/ ) and NARO ( https://www.nrao.edu/archives/files/ori ... 0e15cb.jpg ) are correct. The total error is probably by a factor of 20-200. This means that the picture of the BH should be around 20-200 times smaller than shown above in my 1'483'790'400 Pixel Working-Image...

But it is extremely difficult to estimate exactly which intermediate step the error lies in, since the compared images also come from different sources in the scientific papers. My experience has shown that the last step between "beam" and "donat" cannot usually be checked very precisely visually, since there are no longer any comparable structural features.

What a pity, but ThanX2Y!

(Rollover = Mouseover (also mouse over, hover effect or rollover) refers to a special technique in website design that can be used for various elements such as text, graphics, buttons or banners.)