APOD: Galaxy and Cluster Create Four of... (2015 Mar 09)

[APOD Robot]

Galaxy and Cluster Create Four Images of Distant Supernova

Explanation: What are the unusual spots surrounding that galaxy? They are all images of the same supernova. For the first time, a single supernova explosion has been seen split into multiple images by the gravitational lens deflections of intervening masses. In this case the masses are a large galaxy and its home galaxy cluster. The featured image was captured last November by the Earth-orbiting Hubble Space Telescope. The yellow-hued quadruply-imaged Supernova Refsdal occurred in the early universe far behind the cluster. Measuring the locations and time-delays between the supernova images should allow astrophysicists to recover the amount of dark matter in the galaxy and cluster. With patience and luck, a fifth image of the supernova will also be recovered nearby in the next few years.

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[bystander]

http://asterisk.apod.com/viewtopic.php?t=34519

[ta152h0]

Let's say I am a student in your advanced geometry class. How would you show the light path of this discovery ? Or would you be the devious professor and give it as a final examination ?

[Beyond]

Patience and luck. Very apt descriptions.

[Evenstar]

Mind boggling!

[alter-ego]

Another nice synopsis can be read at S&T
In the S&T blog, C. S. Kochanek (an author referenced in the paper below) is quoted as predicting the 5th (central) image intensity (see below) will be too demagnified to be observable.
If fade timings are seen on all the images it may also be possible to extract Cosmic expansion rate. However, Kochanek states that the detail of gravitational lens needs to be know very accurately: Across the galaxy cluster the lens density variations of ±1% precision must be known and supernova fade timings must be accuratate to within ±5% .

The spiral host galaxy itself is multiply imaged by the galaxy cluster (20 , 25 ). Consequently,
our models predict both that the SN could be detected at future epochs in a
different image of the spiral host galaxy, and that it has already appeared elsewhere in
yet another image of the spiral. A search of archival HST imaging in both the optical
(F606W, F814W, and F850LP) and infrared (F105W, F125W, F140W, and F160W) at the
locations of the multiple images of the presumed host galaxy has revealed no evidence for
SN Refsdal when these data were taken. Our set of cluster lens models predicts that the
SN will appear in the central image of the spiral host galaxy, at an approximate position
of = 11h49m36.01s, = +2223048.1300 (J2000.0) at a future time, within a year to a decade from now (2015 to 2025).

This observation is really a amazing. A real benefit of new-technology, rapid and repetitive, sky survey capabilities will likely yield more of this kind of needle-in-the-haystack data.

[Ann]

What an utterly fascinating image!

Those four images of the supernova look like widely scattered and absurdly red regions of star formation in a ring of star formation around the bulge of the galaxy where they appear to be located. The spiral galaxy in question is interacting with another spiral galaxy in a way that makes it look slightly similar to Hubble's iconic image of interacting galaxies NGC 6050 and IC 1179 in the Hercules Cluster of galaxies. The cluster of galaxies is also remarkable, since it contains several very lively spirals close to its dominant massive ellipticals. What an amazing coincidence! What a fantastic picture!

I hope astronomers find out something interesting about this particular supernova. And then I hope they find out something hugely interesting about dark matter and the evolution of the universe.

Ann

EDIT: I just read alter-ego's post. The host galaxy itself is multiply imaged! No wonder there are so many "very spirally spirals" seen in this cluster! (And imagine that the supernova may be seen again within a year... fantastic!!)

[geckzilla]

Yet another observational accomplishment to add to the long list of things which seem to confirm the elegant theory of general relativity. There are people tying their brains in knots trying to say Einstein got it wrong and gravitational lenses are already almost impossible to explain without GR, but to see a supernova and then see it again as predicted? The promise of this seems almost too good to be true. I can't wait to find out.

For what it's worth, I've got a version of the image up here. It uses near-infrared observations taken over a three month period at the end of 2014 and start of 2015. A small amount of data from 2013 was integrated into the data I used but that didn't stop the supernova from showing up. The featured image uses some shorter wavelength observations for the blue channel (or, at least, the F814W part of it) which were taken six months prior and do not show the supernova. This probably is why the supernova appears so yellow.

[Camiel Plevier]

Why will there be a fifth image? What is the reasoning behind that?

[geckzilla]

Why will there be a fifth image? What is the reasoning behind that?

The gravitational lens increases the length of space that a ray of light must travel in. The stronger the bend, the longer the path. For a path > 9 billion light years long that bending amounted to only a few decades from our vantage point.

[RedFishBlueFish]

Let's say I am a student in your advanced geometry class. How would you show the light path of this discovery ? Or would you be the devious professor and give it as a final examination ?

Yes.

Although I can understand why it is hoped/expected for a 5th and central image to appear, I do not understand why there are four images at the moment - rather than a simple basically continuous circle of brightness surrounding the refracting galaxy.

[R. H. MacDonald]

I can understand an Einstein ring, that is, the original light source being deflected uniformly around the lensing mass (the galaxy in the way.) I can understand how a single, perfectly focused SN image can be displaced to one side. What I cannot understand is the Einstein cross. I cannot see how there will be multiple images that are perfectly focused at different angles. Given a suggestion that the gravity field of the lensing galaxy is elliptical or otherwise asymmetrical, such a field still should only show either a distorted ring or just one displaced image of the supernova.

[starsurfer]

Does anyone remember Intel Pentium?

[geckzilla]

I can understand an Einstein ring, that is, the original light source being deflected uniformly around the lensing mass (the galaxy in the way.) I can understand how a single, perfectly focused SN image can be displaced to one side. What I cannot understand is the Einstein cross. I cannot see how there will be multiple images that are perfectly focused at different angles. Given a suggestion that the gravity field of the lensing galaxy is elliptical or otherwise asymmetrical, such a field still should only show either a distorted ring or just one displaced image of the supernova.

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.

[Ron-Astro Pharmacist]

http://www.pbs.org/wgbh/nova/space/star-in-you.html

We were all so cute as babies. Wonder how old we were when this picture was taken?

Click to play embedded YouTube video.

[Chris Peterson]

I can understand an Einstein ring, that is, the original light source being deflected uniformly around the lensing mass (the galaxy in the way.) I can understand how a single, perfectly focused SN image can be displaced to one side. What I cannot understand is the Einstein cross. I cannot see how there will be multiple images that are perfectly focused at different angles. Given a suggestion that the gravity field of the lensing galaxy is elliptical or otherwise asymmetrical, such a field still should only show either a distorted ring or just one displaced image of the supernova.

It occurs because the lens isn't symmetrical. A ring occurs when the lensing body creates a spherical gravitational field, which is pretty common. Arcs are a variation on this. Multiple images occur when the field is uneven and discontinuous. This is much less common, because galaxies (regardless of their shape) produce substantially spherical fields (because the lensing is caused by dark matter, and that is usually in a spherical halo). The same is true (although to a lesser degree) for galaxy clusters.

[R. H. MacDonald]

It occurs because the lens isn't symmetrical. A ring occurs when the lensing body creates a spherical gravitational field, which is pretty common. Arcs are a variation on this. Multiple images occur when the field is uneven and discontinuous. This is much less common, because galaxies (regardless of their shape) produce substantially spherical fields (because the lensing is caused by dark matter, and that is usually in a spherical halo). The same is true (although to a lesser degree) for galaxy clusters.

Thank you for your post.

So, this topic's lensing galaxy's mass distribution has four separate local maximums and the original single light source (the SN) is being slightly displaced in four separate ways? This would suggest the gravity field doing the distorting would have four points also in the shape of a cross, eh?

[neufer]

I can understand an Einstein ring, that is, the original light source being deflected uniformly around the lensing mass (the galaxy in the way.) I can understand how a single, perfectly focused SN image can be displaced to one side. What I cannot understand is the Einstein cross. I cannot see how there will be multiple images that are perfectly focused at different angles. Given a suggestion that the gravity field of the lensing galaxy is elliptical or otherwise asymmetrical, such a field still should only show either a distorted ring or just one displaced image of the supernova.

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.

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]

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.

---

[R. H. MacDonald]

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.

[R. H. MacDonald]

"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."

Yes, I had gone to Wikipedia and saw that. Thanks for the reply, by the way. What I can't get my head around is that the negative to positive influence in the contour line is a smooth transition and, the way I think of it as, causing a sliding sort of distortion not a perfectly focused one. Multiple crescents, so to speak.

[Chris Peterson]

So, this topic's lensing galaxy's mass distribution has four separate local maximums and the original single light source (the SN) is being slightly displaced in four separate ways? This would suggest the gravity field doing the distorting would have four points also in the shape of a cross, eh?

Keep in mind that the lensing body in this case is not a galaxy, but a galaxy cluster. That is usually the case for gravitational lenses.

[neufer]

"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."

Yes, I had gone to Wikipedia and saw that. Thanks for the reply, by the way. What I can't get my head around is that the negative to positive influence in the contour line is a smooth transition and, the way I think of it as, causing a sliding sort of distortion not a perfectly focused one. Multiple crescents, so to speak.

The two saddle points in particular are far from "perfectly" focused.

[OTheWonderOfItAll]

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.

You simply have to have a lot more faith in that book to sit in a chair with a leg missing, same as walking on water. It can be done, but isn't often.

[Ron-Astro Pharmacist]

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

[Dad is watching]

I can understand an Einstein ring, that is, the original light source being deflected uniformly around the lensing mass (the galaxy in the way.) I can understand how a single, perfectly focused SN image can be displaced to one side. What I cannot understand is the Einstein cross. I cannot see how there will be multiple images that are perfectly focused at different angles. Given a suggestion that the gravity field of the lensing galaxy is elliptical or otherwise asymmetrical, such a field still should only show either a distorted ring or just one displaced image of the supernova.

It occurs because the lens isn't symmetrical. A ring occurs when the lensing body creates a spherical gravitational field, which is pretty common. Arcs are a variation on this. Multiple images occur when the field is uneven and discontinuous. This is much less common, because galaxies (regardless of their shape) produce substantially spherical fields (because the lensing is caused by dark matter, and that is usually in a spherical halo). The same is true (although to a lesser degree) for galaxy clusters.

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?