Explanation: To some, it looks like a penguin. But to people who study the universe, it is an interesting example of two big galaxies interacting. Just a few hundred million years ago, the upper NGC 2936 was likely a normal spiral galaxy: spinning, creating stars, and minding its own business. Then it got too close to the massive elliptical galaxy NGC 2937, below, and took a dive. Together known as Arp 142, they are featured in this new Webbinfrared image, while a visible lightHubble image appears in comparison. NGC 2936 is not only being deflected, but distorted, by this close gravitational interaction. When massive galaxies pass near each other, gas is typically condensed from which new stars form. A young group of stars appears as the nose of the penguin toward the right of the upper galaxy, while in the center of the spiral, bright stars together appear as an eye. Before a billion years, the two galaxies will likely merge into one larger galaxy.
These images are magnificent but it seems that the geometric rectification of one of the two data becomes imprecise when we move away from the center, for example when we go towards the lower left region: there seems to be a few pixels of shift between the Webb data and the other. This doesn't happen in the center.
The narrative seems way off the mark on at least 2 points. Firstly, how can two galaxies (insofar as we can trust red shift distance estimates) 17 million light years apart be gravitationally affecting one another? (326 mly and 343 mly) Secondly, how is it that the spiral is badly broken but the elliptical is unaffected?
Roy wrote: ↑Tue Jul 30, 2024 12:25 pm
The narrative seems way off the mark on at least 2 points. Firstly, how can two galaxies (insofar as we can trust red shift distance estimates) 17 million light years apart be gravitationally affecting one another? (326 mly and 343 mly) Secondly, how is it that the spiral is badly broken but the elliptical is unaffected?
We don't know how far apart they are to that precision. The distance estimates to these objects are determined solely from redshift and then conversion to a Hubble distance. There are measurement uncertainties, the Hubble constant uncertainty, and a relative motion unknown, as well an an uncertain time when the galaxies were at their closest and most of the tidal distortion was occurring.
Current data:
NGC 2936: z = 0.023557 ± 9.29e-6 -> Hubble distance 109.10 ± 7.65 Mpc (356.08 ± 24.97 Mly)
NGC 2937: z = 0.022647 ± 8.84e-6 -> Hubble distance 105.08 ± 7.36 Mpc (342.96 ± 24.02 Mly)
You cannot assess information like this without considering the error bars.
Chris
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Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
https://apod.nasa.gov/apod/ap230925.html wrote:Arp 142: The Hummingbird Galaxy
Image Credit: NASA, ESA, Hubble, HLA; Processing & Copyright: Basudeb Chakrabarti
Explanation: What's happening to this spiral galaxy? Just a few hundred million years ago, NGC 2936, the upper of the two large galaxies shown at the bottom, was likely a normal spiral galaxy -- spinning, creating stars -- and minding its own business. But then it got too close to the massive elliptical galaxy NGC 2937, just below, and took a turn. Sometimes dubbed the Hummingbird Galaxy for its iconic shape, NGC 2936 is not only being deflected but also being distorted by the close gravitational interaction. Behind filaments of dark interstellar dust, bright blue stars form the nose of the hummingbird, while the center of the spiral appears as an eye. Alternatively, the galaxy pair, together known as Arp 142, look to some like Porpoise or a penguin protecting an egg. The featured re-processed image showing Arp 142 in great detail was taken recently by the Hubble Space Telescope. Arp 142 lies about 300 million light years away toward the constellation of the Water Snake (Hydra). In a billion years or so the two galaxies will likely merge into one larger galaxy.
Last edited by bystander on Wed Jul 31, 2024 1:03 am, edited 1 time in total.
Reason:Please, no hot links to images > 500 kb. Uploaded as an attachement.
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Roy wrote: ↑Tue Jul 30, 2024 12:25 pm
The narrative seems way off the mark on at least 2 points. Firstly, how can two galaxies (insofar as we can trust red shift distance estimates) 17 million light years apart be gravitationally affecting one another? (326 mly and 343 mly) Secondly, how is it that the spiral is badly broken but the elliptical is unaffected?
We don't know how far apart they are to that precision. The distance estimates to these objects are determined solely from redshift and then conversion to a Hubble distance. There are measurement uncertainties, the Hubble constant uncertainty, and a relative motion unknown, as well an an uncertain time when the galaxies were at their closest and most of the tidal distortion was occurring.
Current data:
NGC 2936: z = 0.023557 ± 9.29e-6 -> Hubble distance 109.10 ± 7.65 Mpc (356.08 ± 24.97 Mly)
NGC 2937: z = 0.022647 ± 8.84e-6 -> Hubble distance 105.08 ± 7.36 Mpc (342.96 ± 24.02 Mly)
You cannot assess information like this without considering the error bars.
I took those distances from the Wikipedia entries. The elliptical is visibly farther, and unperturbed. Are you defending the narrative because an astronomer wrote it? Or because a non-astronomer questions it?
Roy wrote: ↑Tue Jul 30, 2024 12:25 pm
The narrative seems way off the mark on at least 2 points. Firstly, how can two galaxies (insofar as we can trust red shift distance estimates) 17 million light years apart be gravitationally affecting one another? (326 mly and 343 mly) Secondly, how is it that the spiral is badly broken but the elliptical is unaffected?
We don't know how far apart they are to that precision. The distance estimates to these objects are determined solely from redshift and then conversion to a Hubble distance. There are measurement uncertainties, the Hubble constant uncertainty, and a relative motion unknown, as well an an uncertain time when the galaxies were at their closest and most of the tidal distortion was occurring.
Current data:
NGC 2936: z = 0.023557 ± 9.29e-6 -> Hubble distance 109.10 ± 7.65 Mpc (356.08 ± 24.97 Mly)
NGC 2937: z = 0.022647 ± 8.84e-6 -> Hubble distance 105.08 ± 7.36 Mpc (342.96 ± 24.02 Mly)
You cannot assess information like this without considering the error bars.
I took those distances from the Wikipedia entries. The elliptical is visibly farther, and unperturbed. Are you defending the narrative because an astronomer wrote it? Or because a non-astronomer questions it?
I'm providing the best current distance estimates along with their errors. I do not know which of the two galaxies is nearer. The measurements do not make it certain, and I see nothing in the images to suggest which is the closest. It is also hard to determine the degree to which the elliptical is perturbed, because that is much less obvious is such structures than it is in spiral galaxies.
I don't understand what you think needs "defending".
Last edited by Chris Peterson on Tue Jul 30, 2024 8:56 pm, edited 1 time in total.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
We don't know how far apart they are to that precision. The distance estimates to these objects are determined solely from redshift and then conversion to a Hubble distance. There are measurement uncertainties, the Hubble constant uncertainty, and a relative motion unknown, as well an an uncertain time when the galaxies were at their closest and most of the tidal distortion was occurring.
Current data:
NGC 2936: z = 0.023557 ± 9.29e-6 -> Hubble distance 109.10 ± 7.65 Mpc (356.08 ± 24.97 Mly)
NGC 2937: z = 0.022647 ± 8.84e-6 -> Hubble distance 105.08 ± 7.36 Mpc (342.96 ± 24.02 Mly)
You cannot assess information like this without considering the error bars.
I took those distances from the Wikipedia entries. The elliptical is visibly farther, and unperturbed. Are you defending the narrative because an astronomer wrote it? Or because a non-astronomer questions it?
I'm providing the best current distance estimates along with their errors. I do not know which of the two galaxies is nearer. The measurements do not make it certain, and I see nothing in the images to suggest which is the closest. It is also hard to determine the degree to which the elliptical is perturbed, because that is much less obvious is such structures than it is in spiral galaxies.
Roy, you can't use redshift as a perfect measurement of distance!
According to my software (and based on these two galaxies' redshift), NGC 6050A (at left) is located at a distance of 120 megaparsecs (420 million light-years), but NGC 6050B (at right) is located at a distance of 140 megaparsecs (480 million light-years). If we believe that redshift gives us the perfect distances to these two galaxies, we must assume that NGC 6050A is 60 million light-years closer to us than NGC 6050B (which is about the distance between the Milky Way and the Virgo Cluster).
Take a look at this map of the location of the Virgo Cluster in constellation Virgo:
Can you take a look at the location of the Virgo Cluster in the sky, some ~60 million light-years away from us, and spot the monstrous elliptical galaxy M87 in there? No?
But NGC 6050 A and B are not only cosying up to one another, they are also pretty much the same size. That makes it impossible for them to be 60 million light-years apart. It's impossible!
And as for the interacting galaxies of Arp 142, they are not 17 million light-years apart, either. Believe me, they are not.
Ann
Last edited by Ann on Wed Jul 31, 2024 3:37 am, edited 1 time in total.
I am well aware that redshift is not a reliable measure of distance. Hubble himself doubted it, even after he compiled his table of values with nearby galaxies that led to the concept of a Hubble constant. Which all Big-bang astronomers use as a distance measure. Halton Arp’s Seeing Red discusses it extensively.
But the whole point and title of this post is to claim that two galaxies are interacting gravitationally. I look at the pictures, including the one most recently posted by Johnnydeep and I see Arp 142 severely perturbed in the foreground, and an elliptical unperturbed in the background. When I look up the redshift distance, astronomers have no other, my estimate of what I see is confirmed that they are 17 million light years apart. Our galaxy is only 3 million light years from the great galaxy in Andromeda, and we are not perturbing each other.
Footnote about Hubble: he was a Major in the Army in WWI, and trained troops 1917- 1918. Then had a ground-breaking career as an astronomer with the Mt Wilson 100 inch and Mt Palomar 200 inch telescopes.
Roy wrote: ↑Tue Jul 30, 2024 10:33 pm
I am well aware that redshift is not a reliable measure of distance. Hubble himself doubted it, even after he compiled his table of values with nearby galaxies that led to the concept of a Hubble constant. Which all Big-bang astronomers use as a distance measure. Halton Arp’s Seeing Red discusses it extensively.
But the whole point and title of this post is to claim that two galaxies are interacting gravitationally. I look at the pictures, including the one most recently posted by Johnnydeep and I see Arp 142 severely perturbed in the foreground, and an elliptical unperturbed in the background. When I look up the redshift distance, astronomers have no other, my estimate of what I see is confirmed that they are 17 million light years apart. Our galaxy is only 3 million light years from the great galaxy in Andromeda, and we are not perturbing each other.
Footnote about Hubble: he was a Major in the Army in WWI, and trained troops 1917- 1918. Then had a ground-breaking career as an astronomer with the Mt Wilson 100 inch and Mt Palomar 200 inch telescopes.
Cosmological redshift is most certainly a reliable measure of distance. But it comes with an error of plus or minus a few percent.
Halton Arp became a crackpot. It happens to some scientists when they get old.
That the two galaxies are interacting gravitationally is beyond reasonable doubt. There are no other forces that could produce this kind of distortion, and the resultant shapes, tidal tails, and star formation regions are accurately modeled in many similar systems (possibly in this one, as well) with nothing more than gravity.
You are using poor information to assess the distance between the galaxies (Wikipedia is hardly the definitive source!) and totally ignoring the error on the distances. No astronomer would do this. The optical evidence shows that the galaxies are much closer, and the measured values easily support that. And we certainly don't know which galaxy is in the foreground from any information in these images or from redshift measurements.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
Roy wrote: ↑Tue Jul 30, 2024 10:33 pm
I am well aware that redshift is not a reliable measure of distance. Hubble himself doubted it, even after he compiled his table of values with nearby galaxies that led to the concept of a Hubble constant. Which all Big-bang astronomers use as a distance measure. Halton Arp’s Seeing Red discusses it extensively.
But the whole point and title of this post is to claim that two galaxies are interacting gravitationally. I look at the pictures, including the one most recently posted by Johnnydeep and I see Arp 142 severely perturbed in the foreground, and an elliptical unperturbed in the background. When I look up the redshift distance, astronomers have no other, my estimate of what I see is confirmed that they are 17 million light years apart. Our galaxy is only 3 million light years from the great galaxy in Andromeda, and we are not perturbing each other.
Footnote about Hubble: he was a Major in the Army in WWI, and trained troops 1917- 1918. Then had a ground-breaking career as an astronomer with the Mt Wilson 100 inch and Mt Palomar 200 inch telescopes.
Cosmological redshift is most certainly a reliable measure of distance. But it comes with an error of plus or minus a few percent.
Halton Arp became a crackpot. It happens to some scientists when they get old.
That the two galaxies are interacting gravitationally is beyond reasonable doubt. There are no other forces that could produce this kind of distortion, and the resultant shapes, tidal tails, and star formation regions are accurately modeled in many similar systems (possibly in this one, as well) with nothing more than gravity.
You are using poor information to assess the distance between the galaxies (Wikipedia is hardly the definitive source!) and totally ignoring the error on the distances. No astronomer would do this. The optical evidence shows that the galaxies are much closer, and the measured values easily support that. And we certainly don't know which galaxy is in the foreground from any information in these images or from redshift measurements.
Like Chris said, it's not possible to say which galaxy of Arp 142 is in the background and which is in the foreground.
However, it is indeed likely that the galaxies are currently well separated from one another. During a merger, two galaxies will approach each other, and then, in a sort of slingshot effect, separate, before approaching each other again. Consider the Youtube video of a simulation of the future merger of the Milky Way and Andromeda:
Click to play embedded YouTube video.
But even during first approach, spiral galaxies will typically become distorted. It's their arms that will become distorted, because spiral arms are often all showoff and fireworks and little substance. That is because spiral arms typically get their light from massive blue stars, which shine fantastically bright even though they are not nearly that fantastically massive.
Consider HD 93129A, a brilliant massive O-type star in the cluster Trumpler 14 in the Carina Nebula. According to Wikipedia, the mass of this star is 110 solar masses. But its luminosity is ~1.5 million times the solar luminosity! You should not take these figures to be exact, but you should understand that with massive stars, you get a lot of bang (light) for the buck (mass).
Spiral arms are elongated structures that are typically not that massive. Therefore they are easily distorted during galactic interactions.
Elliptical galaxies, as well as bright yellow cores of spiral galaxies, are the opposite. They contain extremely few, if any, brilliantly bright massive stars. Instead they get their light from billions and billions small cool red and yellow stars (and a much smaller number of moderately-massive red giant stars).
Consider Proxima Centauri, the nearest star to the Earth apart from the Sun. According to Wikipedia, the mass of Proxima is 0.12 the mass of the Sun, but its visible light output is only 0.00005 the light of the Sun!
Elliptical galaxies contain billions and billions of small red dwarf stars. Realistically, stars like Proxima Centauri contribute very little of the light output of elliptical galaxies. Most of the light of these galaxies comes from moderately-massive (say, 1-2 solar masses) red giant stars, whose visible light output is typically 30-300 times that of the Sun.
But while stars like Proxima Centauri contribute very little light to elliptical galaxies, they do provide a lot of mass. That's because the mass of red dwarfs is not negligible, unlike their light output, and there are so, so many of them. Therefore, bright yellow or yellow-white elliptical galaxies are massive. Often but not always, they are also quite compact.
The elliptical component of Arp 142 may indeed be quite compact, because its fluffier (and very faint!) outer layers may already have been torn away and lost during its previous interactions with the spiral galaxy of Arp 142.
We have every reason to believe that the two components of Arp 142 are close to one another - say, separated by no more than 500,000 light-years - and that they are indeed interacting.
Arp 142: Interacting Galaxies from Webb
