APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

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APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by APOD Robot » Wed Nov 08, 2023 5:05 am

Image Perseus Galaxy Cluster from Euclid

Explanation: There's a new space telescope in the sky: Euclid. Equipped with two large panoramic cameras, Euclid captures light from the visible to the near-infrared. It took five hours of observing for Euclid's 1.2-meter diameter primary mirror to capture, through its sharp optics, the 1000+ galaxies in the Perseus cluster, which lies 250 million light years away. More than 100,000 galaxies are visible in the background, some as far away as 10 billion light years. The revolutionary nature of Euclid lies in the combination of its wide field of view (twice the area of the full moon), its high angular resolution (thanks to its 620 Megapixel camera), and its infrared vision, which captures both images and spectra. Euclid's initial surveys, covering a third of the sky and recording over 2 billion galaxies, will enable a study of how dark matter and dark energy have shaped our universe.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Ann » Wed Nov 08, 2023 6:05 am


I just made a post in the Breaking Science News forum about Euclid's first images, before I had seen the new APOD. That was perhaps hasty of me. I used Euclid's portrait of IC 342 to illustrate the capabilities of Euclid, because that picture was my favorite.

But Euclid's portrait of the Perseus Galaxy Cluster is of course absolutely incredibly impressive. We see "near and far" at the same time and with much the same sharpness.

I think of the Perseus Cluster of Galaxies like this:

R. Jay GaBany is an amateur using amateur equipment, and his image is from 2008, which makes it very impressive indeed. As you can see, if you compare GaBany's image with Euclid's, GaBany highlights the very impressive nature of NGC 1275, which Euclid does not.

No, but Euclid highlights the impressive nature of the Perseus Cluster of Galaxies itself, and perhaps even more so, it brings out the almost impossible richness of the galactic background. It is almost as if the Universe had dressed up in jacket studded with glittering sequines:

Sequine studded jacket.png

It's hard not to ask oneself the question, "Why is it dark at night?", when one sees all those little galaxies as crystal-sharp grains of salt richly sprinkled all over Euclid's field.

Ann
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by alex555 » Wed Nov 08, 2023 7:41 am

Euclid shows a diffraction spike pattern similar to Webb.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Randall_Rathbun » Wed Nov 08, 2023 11:59 am

What are the faint purple-blue objects in the picture?

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Christian G. » Wed Nov 08, 2023 1:32 pm

Hubble, James Webb, Euclid, - we are living, right now, in a GOLDEN AGE of astronomy!

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Chris Peterson » Wed Nov 08, 2023 1:54 pm

alex555 wrote: Wed Nov 08, 2023 7:41 am Euclid shows a diffraction spike pattern similar to Webb.
It's a simpler pattern, but shows a similar six-spike pattern due to its 3-vane secondary support spider. (The JWST pattern is the result of hexagonal mirror segments and a 3-arm secondary mirror support, one of which is parallel to mirror sides.)
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Ann » Wed Nov 08, 2023 2:39 pm

Randall_Rathbun wrote: Wed Nov 08, 2023 11:59 am What are the faint purple-blue objects in the picture?
The way I understand it, they must be artifacts. Considering the way they look - they are extended sources, with sharp borders, and no increased brightness in the middle - they can't be anything "real".

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Thwack » Wed Nov 08, 2023 4:25 pm

Ann wrote: Wed Nov 08, 2023 2:39 pm
Randall_Rathbun wrote: Wed Nov 08, 2023 11:59 am What are the faint purple-blue objects in the picture?
The way I understand it, they must be artifacts. Considering the way they look - they are extended sources, with sharp borders, and no increased brightness in the middle - they can't be anything "real".

Ann
They appear to be offset internal reflections from certain bright sources in the image. Similar to when a movie camera shoots an oncoming car at night with its bright headlights seen in one corner of the frame, and you see dim copies of the headlights in the opposite corner of the frame.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Wed Nov 08, 2023 5:52 pm

APOD Robot wrote: Wed Nov 08, 2023 5:05 am Image Perseus Galaxy Cluster from Euclid

Explanation: There's a new space telescope in the sky: Euclid. Equipped with two large panoramic cameras, Euclid captures light from the visible to the near-infrared. It took five hours of observing for Euclid's 1.2-meter diameter primary mirror to capture, through its sharp optics, the 1000+ galaxies in the Perseus cluster, which lies 250 million light years away. More than 100,000 galaxies are visible in the background, some as far away as 10 billion light years. The revolutionary nature of Euclid lies in the combination of its wide field of view (twice the area of the full moon), its high angular resolution (thanks to its 620 Megapixel camera), and its infrared vision, which captures both images and spectra. Euclid's initial surveys, covering a third of the sky and recording over 2 billion galaxies, will enable a study of how dark matter and dark energy have shaped our universe.
So, the Euclid captures link says:
After approximately one month, it reached its destination, a halo orbit around the Sun-Earth second Lagrange point L2, at an average distance of 1.5 million kilometers beyond Earth's orbit (or about four times the distance from the Earth to the Moon). There the telescope is expected to remain operational for at least six years. It joins the Gaia and James Webb Space Telescope missions at L2.

The objective of the Euclid mission is to better understand dark energy and dark matter by accurately measuring the accelerating expansion of the universe. To achieve this, the Korsch-type telescope will measure the shapes of galaxies at varying distances from Earth and investigate the relationship between distance and redshift.
So, how "big" is the L2 Lagrange point? And how close are the three telescopes there to each other?

Also, a "Korsch-type" telescope is a new term for me. Neat stuff!
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Chris Peterson » Wed Nov 08, 2023 6:05 pm

johnnydeep wrote: Wed Nov 08, 2023 5:52 pm
So, how "big" is the L2 Lagrange point? And how close are the three telescopes there to each other?
It's a point. So it is infinitely small. But these spacecraft are in orbits that place them from several hundred thousand to over a million kilometers from that point. So there's plenty of room.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Pastorian » Wed Nov 08, 2023 6:07 pm

Visually it appears as if the galaxies in this cluster are indeed arranged along filaments.
perseus, perceived filaments.jpg
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Wed Nov 08, 2023 7:46 pm

Chris Peterson wrote: Wed Nov 08, 2023 6:05 pm
johnnydeep wrote: Wed Nov 08, 2023 5:52 pm
So, how "big" is the L2 Lagrange point? And how close are the three telescopes there to each other?
It's a point. So it is infinitely small. But these spacecraft are in orbits that place them from several hundred thousand to over a million kilometers from that point. So there's plenty of room.
Ok, thanks.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Wed Nov 08, 2023 8:05 pm

Pastorian wrote: Wed Nov 08, 2023 6:07 pm Visually it appears as if the galaxies in this cluster are indeed arranged along filaments.

perseus, perceived filaments.jpg
I'm not sure those lines of galaxies you're positing in this APOD of the Perseus cluster aren't just created by your brain finding meaning in random points.

Also, I thought the real "galaxy filaments" were on the order of the size of entire clusters and superclusters, and wouldn't control the positions of galaxies within a cluster.

Note that your picture shows the filamentary structure in the early universe, and its 50 Mly view might be perhaps a hundred times (5 Gly) larger now due to the expansion of space.

But my reading of the Wikipedia article didn't manage to explain the scale of these filaments definitively for me.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Mischa Schirmer » Wed Nov 08, 2023 8:18 pm

Randall_Rathbun wrote: Wed Nov 08, 2023 11:59 am What are the faint purple-blue objects in the picture?
These are ghosts from the dichroic beamsplitter. The visible imager VIS onboard Euclid has a purely reflective design to minimise internal straylight. But a refelction of the backside of the dichroic element appears offset with respect to nearby bright stars. Our pipeline will mask them, but these images were processed with a custom-made basic pipeline that does not include many calibrations.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Wed Nov 08, 2023 8:22 pm

Mischa Schirmer wrote: Wed Nov 08, 2023 8:18 pm
Randall_Rathbun wrote: Wed Nov 08, 2023 11:59 am What are the faint purple-blue objects in the picture?
These are ghosts from the dichroic beamsplitter. The visible imager VIS onboard Euclid has a purely reflective design to minimise internal straylight. But a refelction of the backside of the dichroic element appears offset with respect to nearby bright stars. Our pipeline will mask them, but these images were processed with a custom-made basic pipeline that does not include many calibrations.
Hi Mischa! So what's your role with respect to Euclid in general and this particular image?
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by shaileshs » Wed Nov 08, 2023 9:03 pm

Ann wrote: Wed Nov 08, 2023 6:05 am It's hard not to ask oneself the question, "Why is it dark at night?", when one sees all those little galaxies as crystal-sharp grains of salt richly sprinkled all over Euclid's field.

Ann
And they say visible material is less than 4% of universe.. I have a hard time even understanding space between 2 stars within a galaxy (can't imagine how there's hardly collision when 2 galaxies merge).. It's beyond my imagination such vast "visible" matter, how one can imagine how vast the "darkness" surrounding visible matter is.. Simply impossible for human imagination. In AWE of creator and creation. Humbling thought. As @Sadhguru correctly says, human beings (and even other living entities) are just a pop-up on screen and we all feel we are so great..

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by starsurfer » Wed Nov 08, 2023 11:25 pm

Why couldn't Euclid do an all-sky OIII survey?

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Pastorian » Thu Nov 09, 2023 12:14 am

johnnydeep wrote: Wed Nov 08, 2023 8:05 pm I'm not sure those lines of galaxies you're positing in this APOD of the Perseus cluster aren't just created by your brain finding meaning in random points.

Also, I thought the real "galaxy filaments" were on the order of the size of entire clusters and superclusters, and wouldn't control the positions of galaxies within a cluster.
"Brain finding meaning in random points" - I think that's 90% of what brains do : )

It sounds like you're saying that galaxy filaments are structures that far larger than a linear string of galaxies. That's not something I had considered before, thanks, I'll read up on it.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Ann » Thu Nov 09, 2023 6:01 am

shaileshs wrote: Wed Nov 08, 2023 9:03 pm
Ann wrote: Wed Nov 08, 2023 6:05 am It's hard not to ask oneself the question, "Why is it dark at night?", when one sees all those little galaxies as crystal-sharp grains of salt richly sprinkled all over Euclid's field.

Ann
And they say visible material is less than 4% of universe.. I have a hard time even understanding space between 2 stars within a galaxy (can't imagine how there's hardly collision when 2 galaxies merge).. It's beyond my imagination such vast "visible" matter, how one can imagine how vast the "darkness" surrounding visible matter is.. Simply impossible for human imagination. In AWE of creator and creation. Humbling thought. As @Sadhguru correctly says, human beings (and even other living entities) are just a pop-up on screen and we all feel we are so great..
Cotton balls.png
I once built a model of the inner solar system (the Sun, Mercury, Venus, the Earth and the Moon and Mars) using a 2 meter in diameter round table cloth, three 2 centimeter wide cotton balls and two yellow peas.

Then I stretched my mathematical ability to the limit to figure out that, yes, the distance between the Earth and the Sun was some 200 meters, give or take. And the distance between the Earth and the Moon was some 60 centimeters, like the length of your lower arm. (The distance between the Sun and Mars was some 300 meters, and the distance between the Sun and Venus was - I think - 145 meters. The distance from the Sun to Mercury may have been some 80 meters. Don't remember.)

Anyway. I asked two people to hold up the table cloth so that it looked like the round Sun. I asked other people to hold mercury, Venus, the Earth and Moon and Mars. I took long steps that I judged to be about a meter and counted my steps to put the planets in the right place.


100 meter track.png
A 100 meter track. The distance between
cotton ball Earth and table cloth Sun was twice as long.
Here's the deal. It was just unbelievable how small the planets were and how far they were from the Sun. It was mindboggling! Oh, but the Earth and the Moon were close. It was suddenly not hard at all to understand that it had been possible to send people to the Moon. And it became so painfully obvious how immeasurably harder - or impossible? - it would be to send people to Mars!

Here's "the other deal". It was sort of shocking to see how "empty" the inner Solar system really is. And then we must remember that the outer Solar system is much emptier, at least when it comes to the distance between the planets. And let's not even start talking about the distance between the Sun and the nearest stars!

After I made my model of the Solar system, I can easily believe that stars so extremely rarely collide during a galactic merger. That's because they are so terrifically far apart. On the other hand, a galactic merger will doom almost any higher life forms anyway, or so I believe, because the terrible tidal forces unleashed by such a merger will play absolute havoc with most or all planetary orbits around their suns in such galaxies.

Ann
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Mischa Schirmer » Thu Nov 09, 2023 11:22 am

johnnydeep wrote: Wed Nov 08, 2023 8:22 pm Hi Mischa! So what's your role with respect to Euclid in general and this particular image?
I'm the mission calibration scientist. In this role I have to be familiar with a lot of aspects of Euclid and how we process the data, but I also lent a helping hand for these PR images which were processed "externally" by Jean-Charles.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Rauf » Thu Nov 09, 2023 1:40 pm

Ann wrote: Thu Nov 09, 2023 6:01 am
shaileshs wrote: Wed Nov 08, 2023 9:03 pm
Ann wrote: Wed Nov 08, 2023 6:05 am It's hard not to ask oneself the question, "Why is it dark at night?", when one sees all those little galaxies as crystal-sharp grains of salt richly sprinkled all over Euclid's field.

Ann
And they say visible material is less than 4% of universe.. I have a hard time even understanding space between 2 stars within a galaxy (can't imagine how there's hardly collision when 2 galaxies merge).. It's beyond my imagination such vast "visible" matter, how one can imagine how vast the "darkness" surrounding visible matter is.. Simply impossible for human imagination. In AWE of creator and creation. Humbling thought. As @Sadhguru correctly says, human beings (and even other living entities) are just a pop-up on screen and we all feel we are so great..
Cotton balls.png
I once built a model of the inner solar system (the Sun, Mercury, Venus, the Earth and the Moon and Mars) using a 2 meter in diameter round table cloth, three 2 centimeter wide cotton balls and two yellow peas.

Then I stretched my mathematical ability to the limit to figure out that, yes, the distance between the Earth and the Sun was some 200 meters, give or take. And the distance between the Earth and the Moon was some 60 centimeters, like the length of your lower arm. (The distance between the Sun and Mars was some 300 meters, and the distance between the Sun and Venus was - I think - 145 meters. The distance from the Sun to Mercury may have been some 80 meters. Don't remember.)

Anyway. I asked two people to hold up the table cloth so that it looked like the round Sun. I asked other people to hold mercury, Venus, the Earth and Moon and Mars. I took long steps that I judged to be about a meter and counted my steps to put the planets in the right place.


100 meter track.png
A 100 meter track. The distance between
cotton ball Earth and table cloth Sun was twice as long.
Here's the deal. It was just unbelievable how small the planets were and how far they were from the Sun. It was mindboggling! Oh, but the Earth and the Moon were close. It was suddenly not hard at all to understand that it had been possible to send people to the Moon. And it became so painfully obvious how immeasurably harder - or impossible? - it would be to send people to Mars!

Here's "the other deal". It was sort of shocking to see how "empty" the inner Solar system really is. And then we must remember that the outer Solar system is much emptier, at least when it comes to the distance between the planets. And let's not even start talking about the distance between the Sun and the nearest stars!

After I made my model of the Solar system, I can easily believe that stars so extremely rarely collide during a galactic merger. That's because they are so terrifically far apart. On the other hand, a galactic merger will doom almost any higher life forms anyway, or so I believe, because the terrible tidal forces unleashed by such a merger will play absolute havoc with most or all planetary orbits around their suns in such galaxies.

Ann
There's a popular YouTube video, in which they tried to do something similar :)
Click to play embedded YouTube video.

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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Thu Nov 09, 2023 2:20 pm

Mischa Schirmer wrote: Thu Nov 09, 2023 11:22 am
johnnydeep wrote: Wed Nov 08, 2023 8:22 pm Hi Mischa! So what's your role with respect to Euclid in general and this particular image?
I'm the mission calibration scientist. In this role I have to be familiar with a lot of aspects of Euclid and how we process the data, but I also lent a helping hand for these PR images which were processed "externally" by Jean-Charles.
Cool. Thanks.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Thu Nov 09, 2023 2:32 pm

Anne said above:
After I made my model of the Solar system, I can easily believe that stars so extremely rarely collide during a galactic merger. That's because they are so terrifically far apart. On the other hand, a galactic merger will doom almost any higher life forms anyway, or so I believe, because the terrible tidal forces unleashed by such a merger will play absolute havoc with most or all planetary orbits around their suns in such galaxies.

Ann
I don’t know about that. I would think that planets and life in areas of lesser stellar density that “collide” will not experience much orbital disruption. I think stars would have to pass each other well within each others’ Oort clouds to cause any altering of cometary bodies that might one day wreak havoc on inner planets.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by Chris Peterson » Thu Nov 09, 2023 2:40 pm

johnnydeep wrote: Thu Nov 09, 2023 2:32 pm Anne said above:
After I made my model of the Solar system, I can easily believe that stars so extremely rarely collide during a galactic merger. That's because they are so terrifically far apart. On the other hand, a galactic merger will doom almost any higher life forms anyway, or so I believe, because the terrible tidal forces unleashed by such a merger will play absolute havoc with most or all planetary orbits around their suns in such galaxies.

Ann
I don’t know about that. I would think that planets and life in areas of lesser stellar density that “collide” will not experience much orbital disruption. I think stars would have to pass each other well within each others’ Oort clouds to cause any altering of cometary bodies that might one day wreak havoc on inner planets.
Although a bunch of comets thrown into an inner system could certainly be problematic, that's not the real problem. The real problem is tidal forces (and not "terrible tidal forces" at all, but trivially small ones) that perturb planetary orbits. No planetary system is stable, and it takes very little to tweak orbits. And it doesn't take much of an orbital change to massively disrupt the ability of a planet to sustain life. For solar mass bodies, and solar systems similar to our own, the magic distance is about a light year. Anything passing closer than that has a good chance of tweaking orbits enough to end life on planets. That distance is probably common over hundreds of millions of years even in low density parts of collisions. So yeah... as far as complex life is concerned, galactic mergers are probably bad news.
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Re: APOD: Perseus Galaxy Cluster from Euclid (2023 Nov 08)

Post by johnnydeep » Thu Nov 09, 2023 4:25 pm

Chris Peterson wrote: Thu Nov 09, 2023 2:40 pm
johnnydeep wrote: Thu Nov 09, 2023 2:32 pm Anne said above:
After I made my model of the Solar system, I can easily believe that stars so extremely rarely collide during a galactic merger. That's because they are so terrifically far apart. On the other hand, a galactic merger will doom almost any higher life forms anyway, or so I believe, because the terrible tidal forces unleashed by such a merger will play absolute havoc with most or all planetary orbits around their suns in such galaxies.

Ann
I don’t know about that. I would think that planets and life in areas of lesser stellar density that “collide” will not experience much orbital disruption. I think stars would have to pass each other well within each others’ Oort clouds to cause any altering of cometary bodies that might one day wreak havoc on inner planets.
Although a bunch of comets thrown into an inner system could certainly be problematic, that's not the real problem. The real problem is tidal forces (and not "terrible tidal forces" at all, but trivially small ones) that perturb planetary orbits. No planetary system is stable, and it takes very little to tweak orbits. And it doesn't take much of an orbital change to massively disrupt the ability of a planet to sustain life. For solar mass bodies, and solar systems similar to our own, the magic distance is about a light year. Anything passing closer than that has a good chance of tweaking orbits enough to end life on planets. That distance is probably common over hundreds of millions of years even in low density parts of collisions. So yeah... as far as complex life is concerned, galactic mergers are probably bad news.
Ok, thanks for weighing in. I knew you would. :ssmile: And I stand corrected. But is there really enough of a gravitational effect from a star passing within 1 ly of the Sun to be able to - however minutely - perturb its planets' orbits? Let's see now: if the force of the Sun's gravity on Saturn is F at Saturn's distance of 10 AU, and a Sun-like star approaches within 1 ly (63000 AU), that would be 6300 times as far, and so its gravitational force would be 6300*6300 less. That's 40 million times smaller! But I guess even that tiny amount could perturb things significantly over a hundred million years?
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