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APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 4:05 am
by APOD Robot
A Molten Galaxy Einstein Ring
Explanation: It is difficult to hide a galaxy behind a cluster of galaxies. The closer cluster's gravity will act like a
huge lens, pulling images of the
distant galaxy around the sides and
greatly distorting them. This is just the case observed in the
featured image recently re-processed image from the
Hubble Space Telescope. The cluster
GAL-CLUS-022058c is composed of many galaxies and is
lensing the image of a yellow-red background galaxy into
arcs seen around the image center. Dubbed a molten
Einstein ring for its
unusual shape, four images of the same background galaxy
have been identified. Typically, a foreground galaxy cluster can only create such smooth arcs if most of its mass is
smoothly distributed -- and therefore not concentrated in the cluster galaxies visible. Analyzing the positions of these
gravitational arcs gives astronomers a method to estimate the
dark matter distribution in galaxy clusters, as well as infer when the stars in these early galaxies began to form.
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 1:14 pm
by orin stepanek
Although the galaxy isn't really molten; it sure looks like it is! I wish
we could put the photo together to see what the galaxy really looks
like!
This kitty really gets around lately!
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 3:23 pm
by howard.freeland
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 3:56 pm
by Chris Peterson
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 6:43 pm
by johnnydeep
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
Cool!
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 6:47 pm
by johnnydeep
This is the most impressive and convincing picture of gravitational lensing that I've seen so far. I presume an unlensed image of the subject galaxy is not visible here. For the curious, as I was, here's a pic from the linked-to
paper about the four separate images:
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 7:24 pm
by beryllium732
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
How do they know that the lensed galaxy is 9.3 Gyr away? How is it possible to measure that?
It's reddish orange color is because of the redshift? I see streams of blue bands which i guess is hot blue stars? But I guess that the lensed galaxy would be much more blue looking if it were much closer?
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Tue Jul 05, 2022 7:55 pm
by Chris Peterson
beryllium732 wrote: ↑Tue Jul 05, 2022 7:24 pm
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
How do they know that the lensed galaxy is 9.3 Gyr away? How is it possible to measure that?
It's reddish orange color is because of the redshift? I see streams of blue bands which i guess is hot blue stars? But I guess that the lensed galaxy would be much more blue looking if it were much closer?
At cosmological distances, the "distance" (I used light travel time) is directly calculable from the redshift.
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Wed Jul 06, 2022 3:18 am
by C0ppert0p
This is by far, the best example of an Einstein Ring, that i've ever seen
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Wed Jul 06, 2022 7:48 pm
by Ann
beryllium732 wrote: ↑Tue Jul 05, 2022 7:24 pm
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
How do they know that the lensed galaxy is 9.3 Gyr away? How is it possible to measure that?
Distance is normally measured using redshift. Measuring redshift would not be possible if it was not for the presence of absorption lines in stellar spectra (and also in the spectra of galaxies).
When a star or a galaxy is moving away from us, the dark spectral lines move toward the red part of the spectrum, like this:
So basically astronomers just study the spectral lines of a galaxy to find out how redshifted the lines are, and therefore, how far away the galaxy is.
It's reddish orange color is because of the redshift? I see streams of blue bands which i guess is hot blue stars? But I guess that the lensed galaxy would be much more blue looking if it were much closer?
Take a look at the APOD again. Inside the white oval is a fairly undistorted view of the lensed galaxy. The lensed galaxy is relatively similar to nearby galaxy NGC 7678. Both galaxies have an intrinsically yellow center (although the distant galaxy appears to lack a brilliantly bright core), and both of them have one blue arm.
Bear in mind that the light from the distant galaxy in the APOD is very redshifted, but one of the galaxy's arms is intrinsically bluer than the rest of it. The filter used for this Hubble image were F555W, which is this color:
███, and two infrared filters. What passed through the yellow-green filter was mapped as blue in the Hubble image.
Bear in mind that what we see as blue in the APOD was originally emitted as ultraviolet light, which has then been redshifted to yellow-green light by the time it reached the Earth.
Ann
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Wed Jul 06, 2022 7:59 pm
by Ann
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
howard.freeland wrote: ↑Tue Jul 05, 2022 3:23 pm
We are in-line with the distant lensed galaxy and the gravitational lens itself. I'd like to presume that there really are astronomers on that distant galaxy gazing at the lensed Milky Way. I wonder what they would be seeing right now, whatever "right now" means in this relativistic universe?
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source.
In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
Is that why the lensed galaxy looks so big and fat compared with the elliptical galaxy that is lensing it?
Lensed galaxies don't usually look that thick.
Ann
Re: APOD: A Molten Galaxy Einstein Ring (2022 Jul 05)
Posted: Sat Jul 09, 2022 1:51 pm
by beryllium732
Ann wrote: ↑Wed Jul 06, 2022 7:48 pm
beryllium732 wrote: ↑Tue Jul 05, 2022 7:24 pm
Chris Peterson wrote: ↑Tue Jul 05, 2022 3:56 pm
This is an unusual system. The source is at z=1.48 (9.3 Gyr) and the lens is at z=0.36 (4 Gyr), meaning that the lens is approximately centered between us and the source. In most cases where we observe Einstein rings, the lens is much closer to us than the source, meaning that anybody at the source would likely not see our galaxy lensed. This is a rare case where they might.
How do they know that the lensed galaxy is 9.3 Gyr away? How is it possible to measure that?
Distance is normally measured using redshift. Measuring redshift would not be possible if it was not for the presence of absorption lines in stellar spectra (and also in the spectra of galaxies).
When a star or a galaxy is moving away from us, the dark spectral lines move toward the red part of the spectrum, like this:
So basically astronomers just study the spectral lines of a galaxy to find out how redshifted the lines are, and therefore, how far away the galaxy is.
It's reddish orange color is because of the redshift? I see streams of blue bands which i guess is hot blue stars? But I guess that the lensed galaxy would be much more blue looking if it were much closer?
APOD 5 July 2022 lensed galaxy detail.png
Take a look at the APOD again. Inside the white oval is a fairly undistorted view of the lensed galaxy. The lensed galaxy is relatively similar to nearby galaxy NGC 7678. Both galaxies have an intrinsically yellow center (although the distant galaxy appears to lack a brilliantly bright core), and both of them have one blue arm.
Bear in mind that the light from the distant galaxy in the APOD is very redshifted, but one of the galaxy's arms is intrinsically bluer than the rest of it. The filter used for this Hubble image were F555W, which is this color:
███, and two infrared filters. What passed through the yellow-green filter was mapped as blue in the Hubble image.
Bear in mind that what we see as blue in the APOD was originally emitted as ultraviolet light, which has then been redshifted to yellow-green light by the time it reached the Earth.
Ann
Always love your detailed answers! Thank you for explaining it all so vividly!
So in reality it's a very bright galaxy. It's really cool!
