Starship Asterisk*

MACS 1206: A Galaxy Cluster Gravitational Lens

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 above recently released image from the CLASH survey with the Hubble Space Telescope. The cluster MACS J1206.2-0847 is composed of many galaxies and is lensing the image of a yellow-red background galaxy into the huge arc on the right. Careful inspection of the image will reveal at least several other lensed background galaxies -- many appearing as elongated wisps. The foreground cluster can only create such smooth arcs if most of its mass is smoothly distributed dark matter -- and therefore not concentrated in the cluster galaxies visible. Analyzing the positions of these gravitational arcs also gives astronomers a method to estimate the dark matter distribution in galaxy clusters, and infer from that when these huge conglomerations of galaxies began to form.

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Anyone up for a "Slice o' Bacon"?



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Minor detail: there's an 's' missing from the title "MACS 1206: A Galaxy Cluster Gravitational Len" on the APOD page.

Please use the link in the caption to the YouTube video of a slow zoom into this view.
http://www.youtube.com/watch?v=9fNlS_tzBm4
It gives a better than most idea of the extraordinary perfomance of Hubble, as it zooms from an 'ordinary' view of the Corvus asterism; in, in, in, in, into this view.
Gives me vertigo!

John
(The one who wanted less "Gosh! Golly! Gee!" in Asterisk posts!)

^5s John!

(Amazing image, astounding video. Thanks for pointing it out!)

My comment on:
The foreground cluster can only create such smooth arcs if most of its mass is smoothly distributed .... and therefore not concentrated ...

A possible alternative explanation for the smooth gravitational arcs:

1. We observe the light of the background galaxy after B billions of years, but for things travelling with the speed of light time is at a standstill.
2. The trajectory of the photon is bend by the cluster mass in between, but not as we believe right at the time it passes the cluster.
3. The mass that bends the background light should be calculated as an average of the positions of the in between galaxies during B billions of years.

To me it seams that some of the background galaxies appear twice as their images bend around the foreground galaxies! either that or they have twins.

GigaGerard wrote:A possible alternative explanation for the smooth gravitational arcs:

1. We observe the light of the background galaxy after B billions of years, but for things travelling with the speed of light time is at a standstill.

That's not consistent with our very good understanding of General Relativity. It doesn't matter whether a photon feels time in any meaningful sense. What matters is that it exists in the Universe, having a (generally) discrete position and any particular time. That is, from our frame of view, we see it having a trajectory. And we observe a smooth flow of time. It is when and where the photon is acted on in our frame of reference that matters, not the photon's.

Magnificent ! Was this a " lucky shot " ?????

Wolf Kotenberg wrote:Magnificent ! Was this a " lucky shot " ?????

Nope. It was collected as part of a survey project targeting a specific list of known large galaxy clusters, with a well defined set of science goals.

Chris Peterson wrote:
It doesn't matter whether a photon feels time in any meaningful sense.
What matters is that it exists in the Universe, having a (generally) discrete position and any particular time.

Hath not a photon eyes? hath not a photon hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as an electron is? If you prick them, do they not bleed? if you tickle them, do they not laugh? if you poison them, do they not die? and if you wrong them, shall they not revenge? If they are like you in the rest frame, they will resemble you in motion. If a photon wrong a electron, what is his humility? Revenge. If a electron wrong a photon, what should his sufferance be by electron example? Why, revenge. The villany you teach them, they will execute, and it shall go hard but they will better the instruction.

neufer wrote:Hath not a photon eyes? hath not a photon hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as an electron is? If you prick them, do they not bleed? ...

What wavelength does a photon require in order to collect a pound of it? By my calculation, it's 5e-42 m, giving it the energy equivalent of a 10 megaton explosion. You don't want to piss off that photon!

I love it when smart people get in arguments.

Chris Peterson wrote:

neufer wrote:
Hath not a photon eyes? hath not a photon hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as an electron is? If you prick them, do they not bleed? ...

What wavelength does a photon require in order to collect a pound of it? By my calculation, it's 5e-42 m, giving it the energy equivalent of a 10 megaton explosion. You don't want to piss off that photon!

The pound of flash, which I demand of him,
Is dearly bought; 'tis mine and I will have it.
If you deny me, fie upon your laws of relativity!
There is no force in the decrees of Venice.
I stand for judgment: answer; shall I have it?
(Apologies to the Earl of Oxford.)

Neufer, i think you already have it, but I'm not sure what (it) is.

Shakespeare truly does speak in (relatively) universal terms.

Gravitational lensing is one of the more interesting aspects of cosmology that I like to read about. Thanks!

Neufer wrote:

Hath not a photon eyes?

It does!!!












Ann

Chris Peterson wrote:

neufer wrote:Hath not a photon eyes? hath not a photon hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as an electron is? If you prick them, do they not bleed? ...

What wavelength does a photon require in order to collect a pound of it? By my calculation, it's 5e-42 m, giving it the energy equivalent of a 10 megaton explosion. You don't want to piss off that photon!

Unless the photon is on the moon, then it's wavelength for a pound would be 8e-43 m.

hstarbuck wrote:

Chris Peterson wrote:
What wavelength does a photon require in order to collect a pound of it? By my calculation, it's 5e-42 m, giving it the energy equivalent of a 10 megaton explosion. You don't want to piss off that photon!

Unless the photon is on the moon, then it's wavelength for a pound would be 8e-43 m.

I get 4.873e-42 m for the Compton wavelength...

but 7.756e-43 m for the “reduced” Compton wavelength.

<<The reduced Compton wavelength is a natural representation for mass on the quantum scale, and as such, it appears in many of the fundamental equations of quantum mechanics.>>

So you are both right (although this is all rather moot since a Planck length is 1.6162e−35 m).