Starship Asterisk*

Giant Cluster Bends, Breaks Images

Explanation: What are those strange blue objects? Many of the brightest blue images are of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies. Cluster galaxies here typically appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens. A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light. The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 10, 11, and 12 o'clock, from the center of the cluster. A blue smudge near the cluster center is likely another image of the same background galaxy. In all, a recent analysis postulated that at least 33 images of 11 separate background galaxies are discernable. This spectacular photo of galaxy cluster CL0024+1654 from the Hubble Space Telescope was taken in November 2004.

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Question - What is the estimate for how far apart in time the separate images of the galaxy are? By my rough estimate, it looks they might only be a few tens of years apart at most. If they are truly that close in time, could this background galaxy be a special candidate for supernova studies? Presumably, if we saw a supernova appear in one of the images, it would just be a few years before we saw it in one of the others. It seems like there might be a scientific advantage in knowing where to look for a supernova that is certain to appear in just a few years.

WOW....I am dizzy.....

So....how many "Lenses" are there???? If there are 33 images...


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2 questions

1) Why is the background image not a circle? It doesn't have to be a perfect circle because the mass is not spherical.

2) Are the images all in the same place at all light frequencies. I would think there is some prism effect and scatter the light like a prism.

I see what appears to be the original galaxy directly in the center of the galaxy mass

To paraphrase Gertrude Stein ... " There IS A Lot Of There There "

somebodyshort wrote:2 questions

1) Why is the background image not a circle? It doesn't have to be a perfect circle because the mass is not spherical.

2) Are the images all in the same place at all light frequencies. I would think there is some prism effect and scatter the light like a prism.

In order to get an Einstein ring, the foreground lensing galaxy (the red one), the background galaxy being lensed (the blue one) and the observer looking at the ring have to be perfectly aligned. See Astronomy Picture of the Day for December 21, 2011.

By the way, why are the lensing galaxies always red and the lensed galaxies almost always blue? I'd say it's inevitable that the lensing galaxy or galaxies have to be one or more supermassive elliptical galaxies, and such galaxies are always "red and dead", with no (or hardly any) discernible star formation. The reason why such galaxies are the perfect cosmic lenses is because they are the greatest mass concentrations in the universe. What about supermassive black holes? There are several reasons why supermassive black holes can't do a good lensing job by themselves. First of all, there almost certainly doesn't exist a single "galaxy-less" supermassive black hole in the universe. The supermassive black holes are always surrounded by a galaxy. And obviously the black hole plus the galaxy are a lot more massive together than the black hole on its own. In any case, even a supermassive black hole is puny when it comes to mass compared with the most massive elliptical galaxies. Also the galaxy is so very much more extended than the black hole, and a large lens can do a lot more lensing than a tiny one.

Why are the lensed galaxies always blue? That's a trickier question. They don't have to be blue, but they usually are. The reason is probably that the lensed galaxies hail from an epoch when the universe was blue and bursting with star formation well before the gigantic elliptical galaxies had been formed. So we are seeing "very early" brilliantly blue and star forming not-very-massive-for-their-brilliance galaxies, which are the perfect lensed galaxies, and "much later" supermassive, not-very-bright-for-their-mass red elliptical galaxies, which are the perfect cosmic lenses.

What was the second question you asked, are lensing galaxies like prisms? Well no, I don't think they are, because they are very fuzzy at the edges!

Ann

nebosite wrote:Question - What is the estimate for how far apart in time the separate images of the galaxy are? By my rough estimate, it looks they might only be a few tens of years apart at most. If they are truly that close in time, could this background galaxy be a special candidate for supernova studies? Presumably, if we saw a supernova appear in one of the images, it would just be a few years before we saw it in one of the others. It seems like there might be a scientific advantage in knowing where to look for a supernova that is certain to appear in just a few years.

You are probably better at math than I am! But you are right, the different lensed images have to arrive at the Earth at different times, because the different lensed images follow different paths through space to the Earth. Indeed, if a supernova was to appear in one of these lensed galaxy images, astronomers would wait with bated breaths for the appearance of the same supernova in the other lensed images. It would be a tremendously important observation, leading to a treasure trove of facts and discoveries.

The problem is that the probability that a supernova will appear in any of the lensed images in our lifetime is vanishingly small.

Ann

Ann wrote:The problem is that the probability that a supernova will appear in any of the lensed images in our lifetime is vanishingly small.

Well, you're either very old or very lucky. Because several have been observed, including one so new that we're still waiting for the light along one path to reach us. http://apod.nasa.gov/apod/ap150309.html http://asterisk.apod.com/viewtopic.php?t=34526

Absolutely magnificent!

Chris Peterson wrote:several have been observed, including one so new that we're still waiting for the light along one path to reach us. http://apod.nasa.gov/apod/ap150309.html

The Wikipedia entry for that supernova (SN Refsdal) says it's "the first detected multiply-lensed supernova." Have there been others since last November? If not, how dow you account for "several"?

Jim Leff wrote:

Chris Peterson wrote:several have been observed, including one so new that we're still waiting for the light along one path to reach us. http://apod.nasa.gov/apod/ap150309.html

The Wikipedia entry for that supernova (SN Refsdal) says it's "the first detected multiply-lensed supernova." Have there been others since last November? If not, how dow you account for "several"?

There were others previously. Note that what makes Refsdal special is the "multiply lensed" aspect. It is the only example we have so far of such an event. But at least three singly imaged, lensed supernovas have been observed (Abell 383, RXJ1532.9+3021, MACS J1720+35).

IF a galaxy is at ONE distance behind another....and the front is Lensing a Supernova.....WHY would it take longer for light to reach us as any other angle, as the speed is the same, I assume, and the angles through the lens galaxy, and the angles to US....are not appreciably different for that distance to the lensing galaxy? Why should it take years to see another lensed image of the supernova?

Thanks.
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Ann wrote:The problem is that the probability that a supernova will appear in any of the lensed images in our lifetime is vanishingly small.

Chris Peterson wrote:several have been observed, including one so new that we're still waiting for the light along one path to reach us. http://apod.nasa.gov/apod/ap150309.html

http://asterisk.apod.com/viewtopic.php?t=34526

Jim Leff wrote:The Wikipedia entry for that supernova (SN Refsdal) says it's "the first detected multiply-lensed supernova." Have there been others since last November? If not, how do you account for "several"?

The news reporting this in March 2015 also said this was the first detected.
http://asterisk.apod.com/viewtopic.php?t=34519

Edit: I see Chris has already answered this.

Re-edit:

Chris Peterson wrote:There were others previously. Note that what makes Refsdal special is the "multiply lensed" aspect. It is the only example we have so far of such an event. But at least three singly imaged, lensed supernovas have been observed (Abell 383, RXJ1532.9+3021, MACS J1720+35).

http://asterisk.apod.com/viewtopic.php?t=33339

Boomer12k wrote:IF a galaxy is at ONE distance behind another....and the front is Lensing a Supernova.....WHY would it take longer for light to reach us as any other angle, as the speed is the same, I assume, and the angles through the lens galaxy, and the angles to US....are not appreciably different for that distance to the lensing galaxy? Why should it take years to see another lensed image of the supernova?

The angles are all different, so the paths are all different lengths. Keep in mind we're looking at a few years difference for something with a 14 billion year light path.

Boomer12k wrote:IF a galaxy is at ONE distance behind another....and the front is Lensing a Supernova.....WHY would it take longer for light to reach us as any other angle, as the speed is the same, I assume, and the angles through the lens galaxy, and the angles to US....are not appreciably different for that distance to the lensing galaxy? Why should it take years to see another lensed image of the supernova?

Thanks.
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It is because light from the background galaxy is spreading out in all directions, and the distortion of spacetime is not the same throughout the foreground galaxy cluster. Different photons from the background galaxy are going to encounter different local gravity wells as they pass through the cluster.

Ann

somebodyshort wrote:1) Why is the background image not a circle? It doesn't have to be a perfect circle because the mass is not spherical.

There is a dark matter map of this cluster. Dark matter is doing most of the lensing and its mass and location can be inferred from the lensing. Making these dark matter maps is seemingly routine among astronomers interested in such things these days...
http://hubblesite.org/newscenter/archiv ... 7/image/a/