Starship Asterisk*

AmazedAstronomer wrote:Still amazes me how visible these events are and that one could very well wipe out a large portion of the galaxy.

Ron-Astro Pharmacist wrote:The configuration of supernovae points almost seems similar to the points from which gravitational lensing has been studied.

http://arxiv.org/ftp/arxiv/papers/0806/0806.1884.pdf

If the dynamic system remained still keeping it free from distortion could the fifth point fall upon the L2 position?

http://en.wikipedia.org/wiki/Lagrangian_point

neufer wrote:
Pierre de Fermat in 1662 stated that a light ray travels from point P to point P',
along a path which takes the least time(; e.g., an Einstein ring).

In actuality, light ray travel from point P to point P', along a path
for which the travel time is either minimum, maximum or a saddle point.

The four Fermat travel paths of an off center gravitational lens Einstein cross represent:
[list]1) two minimum travel time paths and
2) two saddle point travel time paths:[/list]

http://physics.stackexchange.com/questions/14056/how-does-gravitational-lensing-account-for-einsteins-cross wrote:

Click to view full size image

The black circle is the center of symmetry of the point/strip, the cross next to it is the true position of the quasar, and the four crosses are the locations of the critical points, while the contour-line density on the saddles/sources tell you the inverse brightness. This matches the data perfectly.

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neufer wrote:

Ron-Astro Pharmacist wrote:The configuration of supernovae points almost seems similar to the points from which gravitational lensing has been studied.

http://arxiv.org/ftp/arxiv/papers/0806/0806.1884.pdf

If the dynamic system remained still keeping it free from distortion could the fifth point fall upon the L2 position?

http://en.wikipedia.org/wiki/Lagrangian_point

Similarity with the 5 orbital Lagrange points is purely coincidental.

If the gravitational lens body is sufficiently spread out it will form a fifth (maximum travel time path) point close to the the center of symmetry of the gravitational lens galaxy.

The good news in the case of today's APOD is that this fifth point will be the very last to show the supernova peak intensity.

The bad news, of course, is that it will be hidden by the gravitational lens galaxy itself.

neufer wrote:
Pierre de Fermat in 1662 stated that a light ray travels from point P to point P',
along a path which takes the least time(; e.g., an Einstein ring).

In actuality, light ray travel from point P to point P', along a path
for which the travel time is either minimum, maximum or a saddle point.

The four Fermat travel paths of an off center gravitational lens Einstein cross represent:
[list]1) two minimum travel time paths and
2) two saddle point travel time paths:[/list]

http://physics.stackexchange.com/questions/14056/how-does-gravitational-lensing-account-for-einsteins-cross wrote:

Click to view full size image

The black circle is the center of symmetry of the point/strip, the cross next to it is the true position of the quasar, and the four crosses are the locations of the critical points, while the contour-line density on the saddles/sources tell you the inverse brightness. This matches the data perfectly.

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R. H. MacDonald wrote:

geckzilla wrote: I have the same problem understanding how it happens. Rings are formed by spherical masses and crosses by flattened ones. I'm not sure how it works, though. But it is not hard to believe that it happens especially seeing all of the examples Hubble has provided us with. I just have to accept that I don't understand it well enough for it to be intuitive.

Thank you for your reply. Questions and answers are great ways to come up with more questions and answers.

I just have to accept that I don't understand it well enough for it to be intuitive.

The most read book in the history of mankind has that caveat to its basis. You just have to accept things by faith and faith alone.

I do not. If the chair looks to me like I can sit in it, I'll take the risk. If there is a leg missing, I won't. So, I study chairs in my own limited, uneducated way.

geckzilla wrote:Well, I'm a little insulted that you've equated my take on things to faith. It's more about knowledge in progress than faith. I don't accept that I will and can never understand something. It's just that right now, at this moment, I don't. It's an acceptance of ignorance. That's the complete opposite of faith.

neufer wrote:

http://physics.stackexchange.com/questions/14056/how-does-gravitational-lensing-account-for-einsteins-cross wrote:

Click to view full size image

The black circle is the center of symmetry of the point/strip, the cross next to it is the true position of the quasar, and the four crosses are the locations of the critical points, while the contour-line density on the saddles/sources tell you the inverse brightness. This matches the data perfectly.

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Nitpicker wrote:The different patterns resulting from gravitational lensing, seem analogous to the different kinds of diffraction patterns one gets with different obstructions inside a telescope.

Chris Peterson wrote:

Nitpicker wrote:The different patterns resulting from gravitational lensing, seem analogous to the different kinds of diffraction patterns one gets with different obstructions inside a telescope.

They aren't, though. Gravitational lensing isn't a diffractive process at all. It isn't refractive, either, although it is analogous to refraction in many ways.

Gravitational lenses can't produce real images, because unlike a normal refractive lens, their power is highest in the center and falls off with distance. Imaging lenses are zero power through their centers, and increase in power as the radial distance increases.

Dad is watching wrote: We see four images and expect one more, but is this number limited? If the lensing is a result of a non-symetrical collection of masses, could we not discover a situation where the number of 'lensed images' could be 8 or 10 or more in dependence on the complexity of the non-symmetrical lens?

Also, in today's image where we see the four 'maxima', if the exposure was longer in duration, would we see some sort of connecting image filament forming between the four maxima? Not circular, of course because the lens material is not symetrical, but more snake-like?

Nitpicker wrote:Gravitational lensing patterns do not have to result from diffraction, in order to be analogous to the diffraction patterns observed through different telescope designs. The differing shapes of the gravitational fields (surrounding the galaxy clusters) which form the gravitational lens, are analogous to the differing shapes of the telescope obstructions. Was meant as a geometric analogy only, as neufer's contour map of inverse brightness, was reminiscent of a diffraction pattern, at least in appearance.

Chris Peterson wrote:

Nitpicker wrote:Gravitational lensing patterns do not have to result from diffraction, in order to be analogous to the diffraction patterns observed through different telescope designs. The differing shapes of the gravitational fields (surrounding the galaxy clusters) which form the gravitational lens, are analogous to the differing shapes of the telescope obstructions. Was meant as a geometric analogy only, as neufer's contour map of inverse brightness, was reminiscent of a diffraction pattern, at least in appearance.

To make that geometrical analogy when we're talking about another- and completely unrelated- optical phenomenon is very confusing. I'd certainly avoid it. If you're talking about a geometrical similarity, call it a geometrical similarity. But the wording you chose certainly suggests a phenomenological relationship between the two, even if you didn't mean it that way. As a picker of nits, you ought to appreciate the distinction!

James Rhoades wrote:At about four finger widths from the highlighted galaxy to the lower left corner is an object when viewed under magnification has a series of red objects arranged in a ring around the central object.

Is this another example of gravitational lens magnification.

longtry wrote: ↑Sun Jul 14, 2019 8:20 am ... Now the question is: what is the order of things? Is the SN inside the IS? Or is the IS inside the HC? Or did the SN happen in an even farther galaxy, so its light came to us through this sequence: SN => IS => HC => Earth?

The yellow-hued quadruply-imaged Supernova ... occurred in the early universe far behind the cluster.

rstevenson wrote: ↑Sun Jul 14, 2019 6:45 pmAs the description says:

The yellow-hued quadruply-imaged Supernova ... occurred in the early universe far behind the cluster.

So it's kind of SN => (IS + HC) => Earth.

longtry wrote: ↑Mon Jul 15, 2019 3:54 am dark matter centre.jpg

rstevenson wrote: ↑Sun Jul 14, 2019 6:45 pmAs the description says:

The yellow-hued quadruply-imaged Supernova ... occurred in the early universe far behind the cluster.

So it's kind of SN => (IS + HC) => Earth.

Thanks, Rob. If that's the case, then can you show me the place of the SN in the picture as if the IS+HC were not there at all? ...

longtry wrote: ↑Sun Jul 14, 2019 8:20 am Wow... the picture from Hubble site is amazing, and it raises many questions in my head that I can't possibly wrap them around without being able to understand each of them step by step. So, here they go:
1. In the picture, the 4 arrows point to 4 bright yellow points that appear inside a blue-y swirl in the south-southwest portion of an overwhelmingly big and fuzzy light source. As I understand it, the 4 bright points are identified as 1 supernova (SN); the blue swirl is actually 2 interacting spirals (IS) with distinct cores, like in the Antennae pair; and the big fuzzy thing is the dominant center of a huge cluster (HC) with many galaxies swimming all around the picture. Please correct me if I'm wrong.
Now the question is: what is the order of things? Is the SN inside the IS? Or is the IS inside the HC? Or did the SN happen in an even farther galaxy, so its light came to us through this sequence: SN => IS => HC => Earth?

APOD Robot wrote: ↑Mon Mar 09, 2015 4:08 am Galaxy and Cluster Create Four Images of Distant Supernova

Explanation: With patience and luck, a fifth image of the supernova will also be recovered nearby in the next few years.

https://en.wikipedia.org/wiki/SN_Refsdal wrote:
<<SN Refsdal is the first detected multiply-lensed supernova, visible within the field of the galaxy cluster MACS J1149+2223. It was given its nickname in honor of the Norwegian astrophysicist Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the universe. The host galaxy of SN Refsdal is at a redshift of 1.49, corresponding to a comoving distance of 14.4 billion light-years and a lookback time of 9.34 billion years. The multiple images are arranged around the elliptical galaxy at z = 0.54 in a cross-shaped pattern, also known as an "Einstein cross".

---

The image to the left shows a part of the deep field observation of the galaxy cluster MACS J1149.5+2223 from the Frontier Fields programme. The circle indicates the predicted position of the newest appearance of the supernova. To the lower right the Einstein cross event from late 2014 is visible. The image on the top right shows observations by Hubble from October 2015, taken at the beginning of the observation programme to detect the newest appearance of the supernova. The image on the lower right shows the discovery of the Refsdal Supernova on 11 December 2015, as predicted by several different models.

After the discovery of the Refsdal Supernova, astronomers predicted that they would have the rare opportunity to see the supernova again in about one year, after the four images had faded away. This is because the initially observed four-image pattern was only one component of the lensing display. The supernova may have appeared as a single image some 40–50 years ago elsewhere in the cluster field.

The supernova Refsdal reappeared punctually at the predicted position between mid November 2015 and December 11, 2015 (with the exact date being uncertain by approximately one month which is the interval between two consecutive Hubble observations), in excellent agreement with the blind model predictions made before the reappearance was observed. The time delay between the original quadruplet observed in 2014 and the latest appearance of the supernova in 2015 was used to infer the value of the Hubble constant. This is the first time this technique, originally suggested by Refsdal, has been applied to supernovae.>>

Chris Peterson wrote: ↑Mon Jul 15, 2019 1:08 pm Specifically, the lensing mass has z=0.54 (~5 Gly), and the SN has z=1.49 (~9 Gly).

neufer wrote: ↑Mon Jul 15, 2019 4:26 pm With patience and [bad] luck, those two specific links have disappeared since "2015 Mar 09."

rstevenson wrote: ↑Mon Jul 15, 2019 12:51 pm Given the four almost equally spaced images of the SN around the bright blob, I would guess that the SN is directly behind it -- perhaps a little off center. But those in the know can likely calculate this instead of guess, and I'm just an interested amateur. For example, the center of mass of the entire cluster would also have an influence on the path the SN's light took getting to and around that blob.

longtry wrote: ↑Tue Jul 16, 2019 4:12 am Since no one has commented on the previous pic, I suppose that everyone is OK with my assumption. Now with Bob's confirmation about the SN, I've modified the image once again, this time adding 2 red marks indicating the SN, 9Gly from Earth, in the position it would be in if there were no HC+IS at all. OK, time for 2nd question:
2. How could another ghost image of the SN "may" appear in the blue circle in 1995?? Light had to bend all the way around and thus needed to travel way way farther than through the nearly straight IS route. It'd be more like 2035 with the configuration we're talking about.