Cluster Homes - APOD 2009 July 16

[emc]

http://apod.nasa.gov/apod/ap090716.html

Hello, hello. Anybody OUT there? Look… you’re not foolin’ me… hello?

[craterchains]

How about correcting this mis-statement?

", , , an archipelago of island universes a mere , , , "

Shouldn't that be island galaxies?

[Chris Peterson]

How about correcting this mis-statement?

", , , an archipelago of island universes a mere , , , "

Shouldn't that be island galaxies?

There's no such thing as an "island galaxy"; the very definition of "galaxy" carries the concept of being island-like. "Island universe" is a reference to terminology that first entered with the clear observation of galaxies, and persisted well into the 20th century. It remains a nice expression, carrying a flavor of the poetic, and seems to me entirely appropriate as used in captioning this image. (And note that the term is linked to material explaining its usage.)

[neufer]

How about correcting this mis-statement?

", , , an archipelago of island universes a mere , , , "

Shouldn't that be island galaxies?

"Island universes" is a little archaic but still acceptable. (At least it is not "nebulous.")

<<When William Herschel constructed his catalog of deep sky objects, he used the name spiral nebula for certain objects such as M31. These would later be recognized as immense conglomerations of stars, when the true distance to these objects began to be appreciated, and they would be termed island universes. However, the word universe was understood to mean the entirety of existence, so this expression fell into disuse and the objects instead became known as galaxies.>>

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• "See yonder, lo, the Galaxyë
  Which men clepeth the Milky Wey,
  For hit is whyt." —Geoffrey Chaucer. The House of Fame, c. 1380.

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• Jules Verne » The Moon-Voyage » Chapter XI. Imagination and Reality.
  
  Islands are numerous on the surface of the moon. They are almost all oblong or circular, as though traced with a compass, and seem to form a vast archipelago, like that charming group lying between Greece and Asia Minor which mythology formerly animated with its most graceful legends. Involuntarily the names of Naxos, Tenedos, Milo, and Carpathos come into the mind, and you seek the ship of Ulysses or the "clipper" of the Argonauts. That was what it appeared to Michel Ardan; it was a Grecian Archipelago that he saw on the map. In the eyes of his less imaginative companions the aspect of these shores recalled rather the cut-up lands of New Brunswick and Nova Scotia; and where the Frenchman looked for traces of the heroes of fable, these Americans were noting favourable points for the establishment of mercantile houses in the interest of lunar commerce and industry.

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• Archipelago, n.; pl. -goes or -gos . [It. arcipelago, properly, chief sea; Gr. pref + sea, perh. akin to blow, and expressing the beating of the waves. See Plague.] In a general sense, a sea interspersed with many isles; but particularly the sea which separates Europe from Asia, otherwise called the Egean Sea. It contains the Grecian isles, called Cyclades and Sporades.
  
  Plague, n. [L. plaga a blow, stroke, plague; akin to Gr. , fr. to strike; cf. L. plangere to strike, beat. Cf. Plaint.]

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[bystander]

How about correcting this mis-statement?

", , , an archipelago of island universes a mere , , , "

Shouldn't that be island galaxies?

IMHO, no. The island universe link to a previous apod provides a reference to The 1920 Shapely - Curtis Debate: The Scale of the Universe which provides a background for how recently this issue was decided. However that doen't resolve the term "island universe".

In 1750, Thomas Wright, in An original theory or new hypothesis of the universe, correctly speculated that the Milky Way was a flattened disc of stars and that many faint "nebulae" are probably just incredibly distant galaxies. Immanuel Kant, who in 1755 in Universal Natural History and Theory of Heaven expounded upon Wright's ideas, is generally credited with the term island universe. However, since universe was understood to be all encompassing, galaxy (originally meant to refer to the Milky Way) became the reference of choice.

So, it should be galaxy or island universe, but never island galaxy, and since we're talking archipelago, island universe seems appropriate.

[emc]

I've noticed that our physically interactive universe is limited to the Solar System. So in effect, our solar system is an “island universe”. The cosmos certainly fills our eyes and spectrometers but we can’t reach out and touch very much of it... not even remotely.

My point in starting this post about today's APOD was the incredible odds that someone amongst the Hercules Cluster of Galaxies is watching our island. Maybe they have an Asterisk too and muse about us.

I enjoy the term “island universe”. For me, it registers poetic, like Chris pointed out.

[Chris Peterson]

I've noticed that our physically interactive universe is limited to the Solar System. So in effect, our solar system is an “island universe”. The cosmos certainly fills our eyes and spectrometers but we can’t reach out and touch very much of it... not even remotely.

Although we are very nearly restricted to observing the Universe (and even most of the Solar System) in the light of EM, we do scoop up the occasional particle of interstellar dust, so there is at least a bit of condensed matter from elsewhere in the Universe available for our examination.

[neufer]

---------------------------------------------------------------------
. Coriolanus > Act IV, scene VI
.
MENENIUS: We loved him but, like beasts
. And cowardly nobles, gave way unto your clusters,
. Who did hoot him out o' the city.
.
COMINIUS: But I fear they'll roar him in again.
.
. [Enter a troop of Citizens]
.
MENENIUS: Here come the clusters.
---------------------------------------------------------------------
Cluster, n. [AS. cluster, clyster; cf. LG. kluster (also Sw. & Dan. klase a cluster of grapes, D. klissen to be entangled?.)]
.
1. A number of things of the same kind growing together; a bunch.
. Her deeds were like great clusters of ripe grapes, Which load the bunches of the fruitful vine. Spenser.
.
2. A number of similar things collected together or lying contiguous; a group; as, a cluster of islands." Motley.
.
3. A number of individuals grouped together or collected in one place; a crowd; a mob.
. As bees . . . Pour forth their populous youth about the hive In clusters. Milton.
---------------------------------------------------------------------

<<The Hercules Cluster (Abell 2151) is a cluster of about 100 galaxies some 570 million light-years distant in the constellation Hercules. It is rich in spiral galaxies and shows many interacting galaxies. The cluster is part of the larger Hercules supercluster.>>

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Superclusters are large groups of smaller galaxy groups and clusters and are among the largest structures of the cosmos.



The existence of superclusters indicates that the galaxies in our Universe are not uniformly distributed; most of them are drawn together in groups and clusters, with groups containing up to 50 galaxies and clusters up to several thousand. Those groups and clusters and additional isolated galaxies in turn form even larger structures called superclusters.

When we observe super clusters and larger structures today, we learn about the condition of the universe when these super clusters were created. The directions of the rotational axes of galaxies within super clusters also gives us insight into the formation process of galaxies early in the history of the Universe.

No clusters of super clusters (“hyperclusters”) are known, and the existence of structures larger than superclusters is debated. Interspersed among super clusters are large voids of space in which few galaxies exist. Even though superclusters are the largest structures confirmed, the total number of superclusters leaves possibilities for structural distribution; the total number of super clusters in the universe is believed to be close to 10 million.>>

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[emc]

Although we are very nearly restricted to observing the Universe (and even most of the Solar System) in the light of EM, we do scoop up the occasional particle of interstellar dust, so there is at least a bit of condensed matter from elsewhere in the Universe available for our examination.

So the cosmos leaks too.

[craterchains]

Island Universes, or Island Galaxies?

It is no wonder that our education systems are failing all over the world; confusion breeds instability and insanity. Why confuse this issue any more than it all ready is in the developing minds of those wanting to learn truth and not theories?

Universe
Galaxies make up the known universe.
Solar systems make up the galaxies.
Planets and moons make up the solar systems.

Now what's so hard about that?

, , , or even debatable?

[Chris Peterson]

Island Universes, or Island Galaxies?

As previously noted "island galaxy" doesn't mean anything, and would generally be poor usage. "Island universe" does have a specific meaning- it means "galaxy", and is acceptable usage in many cases. Note the important distinction between "universe" (especially as modified) and "the Universe".

[bystander]

Galaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation. They form the densest part of the large scale structure of the universe. In models for the gravitational formation of structure with cold dark matter, the smallest structures collapse first and eventually build the largest structures, clusters of galaxies. Clusters are then formed relatively recently between 10 billion years ago and now. Groups and clusters may contain from ten to thousands of galaxies. The clusters themselves are often associated with larger groups called superclusters.

The Hercules Cluster (Abell 2151) is a cluster of about 100 galaxies some 570 million light-years distant in the constellation Hercules. It is rich in spiral galaxies and shows many interacting galaxies. The cluster is part of the larger Hercules supercluster.

Superclusters are large groups of smaller galaxy groups and clusters and are among the largest structures of the cosmos.

The existence of superclusters indicates that the galaxies in our Universe are not uniformly distributed; most of them are drawn together in groups and clusters, with groups containing up to 50 galaxies and clusters up to several thousand. Those groups and clusters and additional isolated galaxies in turn form even larger structures called superclusters.

In physical cosmology, filaments are the largest known structures in the universe, thread-like structures with a typical length of 50 to 80 h-1 megaparsecs that form the boundaries between large voids in the universe. Filaments consist of gravitationally-bound galaxies; parts where a large number of galaxies are very close to each other are called superclusters.


The present day dark matter distribution in a slice cut through a simulation of a flat universe with cosmological constant. The distribution reveals fine, filamentary structures. The slice has a side length of 520 million light years, and a thickness of 100 million light years. It contains the so-called "supergalactic plane". The major nearby clusters, like Coma, Virgo, Perseus cluster, are labelled.

These filaments remind me of the network of nerves in our bodies.

[emc]

What if outer space aliens have mental illnesses like us? Would they be “out there” or what?

Maybe these Cluster Homes (Galaxies) are suffering from proximity incumbent super stress ecological disorder… too many galaxies in one place?

[emc]

The present day dark matter distribution in a slice cut through a simulation of a flat universe with cosmological constant. The distribution reveals fine, filamentary structures. The slice has a side length of 520 million light years, and a thickness of 100 million light years. It contains the so-called "supergalactic plane". The major nearby clusters, like Coma, Virgo, Perseus cluster, are labelled.

These filaments remind me of the network of nerves in our bodies.

Sure would be neat to see a few billion year movie time lapsed into a few hours.

[bystander]

Cluster Homes

[neufer]

• 
  
  * Blue: optical image from the Digitized Second Palomar Sky Survey
  * Red: radio image from the VLA at 21cm wavelength (1.415 GHz, 1.5 arcsec FWHM)
  * Elliptical galaxy at z=0.016485

The inner jet of radio galaxy NGC 315 as observed with Chandra and the Very Large Array
D. M. Worrall 1★ , M. Birkinshaw 1 , R. A. Laing 2 , W. D. Cotton 3 and A. H. Bridle

<<We present Chandra X-ray results for the jet, nucleus and gaseous atmosphere of NGC 315, a nearby radio galaxy whose jet kinematics are known through deep radio mapping. Diffuse X-ray synchrotron emission is detected from the jet out to 30 arcsec from the nucleus, through regions both of fast bulk flow and deceleration. The X-ray-to-radio flux ratio drops considerably where the flow decelerates, but the X-ray and radio emissions show similar transverse extents throughout, requiring distributed particle acceleration to maintain the supply of X-ray-emitting electrons. A remarkable knotty filament within the jet is seen in both the radio and X-ray, contributing roughly 10 per cent of the diffuse emission along its extent at both wavelengths. No completely satisfactory explanation for the filament is found, though its oscillatory appearance, roughly aligned magnetic field and requirements for particle acceleration, suggest that it is a magnetic strand within a shear layer between fast inner and slower outer flow.>>

[emc]

• 
  
  * Blue: optical image from the Digitized Second Palomar Sky Survey
  * Red: radio image from the VLA at 21cm wavelength (1.415 GHz, 1.5 arcsec FWHM)
  * Elliptical galaxy at z=0.016485

The inner jet of radio galaxy NGC 315 as observed with Chandra and the Very Large Array
D. M. Worrall 1★ , M. Birkinshaw 1 , R. A. Laing 2 , W. D. Cotton 3 and A. H. Bridle

<<We present Chandra X-ray results for the jet, nucleus and gaseous atmosphere of NGC 315, a nearby radio galaxy whose jet kinematics are known through deep radio mapping. Diffuse X-ray synchrotron emission is detected from the jet out to 30 arcsec from the nucleus, through regions both of fast bulk flow and deceleration. The X-ray-to-radio flux ratio drops considerably where the flow decelerates, but the X-ray and radio emissions show similar transverse extents throughout, requiring distributed particle acceleration to maintain the supply of X-ray-emitting electrons. A remarkable knotty filament within the jet is seen in both the radio and X-ray, contributing roughly 10 per cent of the diffuse emission along its extent at both wavelengths. No completely satisfactory explanation for the filament is found, though its oscillatory appearance, roughly aligned magnetic field and requirements for particle acceleration, suggest that it is a magnetic strand within a shear layer between fast inner and slower outer flow.>>

So what’s up with this Art? The knotty filament is challenging my perception of “what’t going on” in our universe. This is the sort of thing that makes me wish I were smart in a cosmic sense. Are you telling me that this is an illustration of how these dark matter filaments are formed? I think you are a smart man but your thoughts often seem to traverse above my head. But I enjoy your posts.

[neufer]

So what’s up with this Art?

Bystander's filament picture included NGC 315 so I investigated a little.

The knotty filament is challenging my perception of “what’t going on” in our universe. This is the sort of thing that makes me wish I were smart in a cosmic sense. Are you telling me that this is an illustration of how these dark matter filaments are formed? I think you are a smart man but your thoughts often seem to traverse above my head. But I enjoy your posts.

My posts often traverse above my own head. But I appreciate the interest.