APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun 29)

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APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun 29)

Post by APOD Robot » Wed Jun 29, 2011 4:06 am

Image Abell 2744: Pandoras Cluster of Galaxies

Explanation: Why is this cluster of galaxies so jumbled? Far from a smooth distribution, Abell 2744 not only has knots of galaxies, but the X-ray emitting hot gas (colored red) in the cluster appears distributed differently than the dark matter. The dark matter, taking up over 75 percent of the cluster mass and colored blue in the above image, was inferred by that needed to create the distortion of background galaxies by gravitational lensing. The jumble appears to result from the slow motion collision of at least four smaller galaxy clusters over the past few billion years. The above picture combines optical images from the Hubble Space Telescope and the Very Large Telescope with X-ray images from the Chandra X-Ray Observatory. Abell 2744, dubbed Pandora's cluster, spans over two million light years and can best be seen with a really large telescope toward the constellation of the Sculptor.

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by bystander » Wed Jun 29, 2011 4:24 am

Abell 2744: Pandora’s Cluster — Clash of the Titans
http://asterisk.apod.com/viewtopic.php?f=31&t=24246
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Beyond » Wed Jun 29, 2011 4:48 am

Finally! A place thats as confused as i am about everything. :mrgreen:
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Boomer12k » Wed Jun 29, 2011 4:52 am

The collision of four smaller clusters is going to be even and symmetrical? That is kind of limited thinking when we know now that the Universe is a chaotic place.

Who says the hot gas and dark matter distribution has to match? They are two different things. Two galaxies collide, their motion stalls as the gravity of both works to coalesce them together. Yet their dark matter continues on in the direction they were going like two remote control cars with marbles on them when they crash. The cars stop, but the marble fly off and keep going. So I would expect them to act differently. So of course four clusters collide and the distribution is different, and uneven, there are four of them!
And yet this whimsical stuff (dark matter) that keeps going is supposed to hold the galaxies together so everything spins at the same observed rate? And it is 75 percent of the mass in this picture? It is either of very much more mass and acts as one, or it is like neutrinos, so slight and small and different that it is barely affected by anything. Dark Matter is strange stuff indeed.

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Jim Leff » Wed Jun 29, 2011 4:58 am

" Abell 2744, dubbed Pandora's cluster, spans over two million light years"

So this entire cluster spans just twenty Milky Ways (@100,000 light years in diameter)??

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Chris Peterson » Wed Jun 29, 2011 5:06 am

This is one of my favorite astronomical images of all time. To me, it represents the best of scientific thinking, to develop an approach to indirectly detect, and render as an image, a large region of dark matter. Great stuff!
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Boomer12k » Wed Jun 29, 2011 5:29 am

Jim Leff wrote:" Abell 2744, dubbed Pandora's cluster, spans over two million light years"

So this entire cluster spans just twenty Milky Ways (@100,000 light years in diameter)??

Doesn't seem possible that all those galaxies are in the space between the Milky Way and The Andromeda Galaxy, 2.2-ish million light years. No wonder the gas is so hot.
I tried to search for the number of galaxies in the cluster, but could not find it. It is a said to be 3.5 billion light years away.

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by alter-ego » Wed Jun 29, 2011 6:17 am

Boomer12k wrote:
Jim Leff wrote:" Abell 2744, dubbed Pandora's cluster, spans over two million light years"

So this entire cluster spans just twenty Milky Ways (@100,000 light years in diameter)??

Doesn't seem possible that all those galaxies are in the space between the Milky Way and The Andromeda Galaxy, 2.2-ish million light years. No wonder the gas is so hot.
I tried to search for the number of galaxies in the cluster, but could not find it. It is a said to be 3.5 billion light years away.
I found a 2006 reference where the estimated total mass within 1 Mpc ≈1.5x10^15 M☉. Assuming the APOD link estimating galaxies amount to ≈5% (of the total mass) applies to the same region, and that our galaxy ≈1.5x10^11 M☉, then that works out to be a whopping 500 galaxies or so!
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by garry » Wed Jun 29, 2011 9:59 am

With dark matter, I thought it was still a theory and still nota proven scientific fact. If in the APOD it is coloured blue, does this mean you can measure it? How do you measure a theory? A discrepancy perhaps?

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by neufer » Wed Jun 29, 2011 11:41 am

Art Neuendorffer

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by hughmass » Wed Jun 29, 2011 1:14 pm

Remember the old Star Trek episodes, where alien intelligences made of clouds of energy roamed the Universe.
They looked exactly like this. Well, on my tv they did.
Gene Roddenberry, such a genius, Star Trek, Babylon 5, so predictive of the future.
Just waiting for the iCloud's communication and ultimatums.

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by bystander » Wed Jun 29, 2011 1:21 pm

garry wrote:With dark matter, I thought it was still a theory and still nota proven scientific fact. If in the APOD it is coloured blue, does this mean you can measure it? How do you measure a theory? A discrepancy perhaps?
Most of astrophysics is theory. Yes, you can measure dark matter, or rather the effects of it. By measuring the "lensing effect", the amount of matter required to produce that effect can be computed. What matter isn't visible in emr is assumed to be dark matter (arXiv:1103.2772).
bystander wrote:Abell 2744: Pandora’s Cluster — Clash of the Titans
http://asterisk.apod.com/viewtopic.php?f=31&t=24246
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by neufer » Wed Jun 29, 2011 1:46 pm

bystander wrote:
Most of astrophysics is theory.
Most of astrophysics is hypothesis; the best of astrophysics is theory.
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by orin stepanek » Wed Jun 29, 2011 1:57 pm

I was surprised to learn that clusters of galaxies would collide with other clusters. Seems as though with the universe expanding; that they would be going away from each other. :?
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by BMAONE23 » Wed Jun 29, 2011 1:59 pm

An interesting image to be certain. With the combination of Hubble Images and VLT Images being used to create the visible image I have to ask: Did hubble images produce the more focused central region and the VLT images the less focused outside areas?

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by bystander » Wed Jun 29, 2011 2:08 pm

BMAONE23 wrote:Did hubble images produce the more focused central region and the VLT images the less focused outside areas?
HubbleSite wrote:... The image is a composite of separate exposures made by Hubble Space Telescope Advanced Camera for Surveys detectors in October 2009, the VLT, and the Chandra ACIS detector. Hubble provides the central, most detailed part of the image, while the VLT, which has a wider field of view, provides the outer parts of the image.
bystander wrote:Abell 2744: Pandora’s Cluster — Clash of the Titans
http://asterisk.apod.com/viewtopic.php?f=31&t=24246
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by hickok_wild_b » Wed Jun 29, 2011 3:33 pm

There is clearly a spaceship in the lower right

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by bystander » Wed Jun 29, 2011 5:05 pm

hickok_wild_b wrote:There is clearly a spaceship in the lower right
Clearly, and at 3.5 billion light years away, it must be huge. :roll:
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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Chris Peterson » Wed Jun 29, 2011 5:13 pm

garry wrote:With dark matter, I thought it was still a theory and still nota proven scientific fact. If in the APOD it is coloured blue, does this mean you can measure it? How do you measure a theory? A discrepancy perhaps?
Everything's a theory (or if you like, per Neufer, some things are hypotheses). There is no such thing as a proven scientific fact- that concept doesn't exist is science. Everything we measure, we measure indirectly and infer some sort of physical truth from our interpretation of that measurement.

Given the number of independent observations that can be explained by dark matter, few physicists doubt that it is real, even if it remains uncertain just what all of its actual physical properties are.
Chris

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by brutus inquisitor » Wed Jun 29, 2011 6:33 pm

Thank you for this impressive image and for the fascinating postings. Maximum enjoyment!
doleo ergo sum

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by neufer » Wed Jun 29, 2011 8:24 pm

orin stepanek wrote:
I was surprised to learn that clusters of galaxies would collide with other clusters.

Seems as though with the universe expanding; that they would be going away from each other. :?
Hubble expansion cannot do work on (i.e., expand) gravitationally bound systems.

(Besides, Hubble expansion would only have amounted to just 50 km/s within the span of two million light years.)
Art Neuendorffer

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by islader2 » Wed Jun 29, 2011 9:15 pm

BRUTUS INQ: quid quid latine dictum sit, altum vivitur {si hoc legere scis nimium eruditionis habes} Ave!

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by Boomer12k » Wed Jun 29, 2011 9:54 pm

garry wrote:With dark matter, I thought it was still a theory and still nota proven scientific fact. If in the APOD it is coloured blue, does this mean you can measure it? How do you measure a theory? A discrepancy perhaps?

The dark matter in blue is an ESTIMATE based on what it would take to achieve the gravitational lensing effects, that normal matter does not add up to being able to do... supposedly. It is "INFERRED".

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by saturn2 » Thu Jun 30, 2011 12:28 am

Pandora Cluster of Galaxies is very great 2 millions of l. y.

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Re: APOD: Abell 2744: Pandoras Cluster of Galaxies (2011 Jun

Post by DavidLeodis » Thu Jun 30, 2011 10:24 am

In the final sentence in the explanation it states Abell 2744 "can best be seen with a really large telescope". That made me :) . So, size does matter :!:

PS. The APOD is a cropped version of the full released image that can be seen when clicking on the APOD or some of the links. To me there does not seem to be anything of significance gained here by using a cropped version and so I would prefer to see the image that was released.