APOD: The Universe Nearby (2011 Jun 14)

Comments and questions about the APOD on the main view screen.

APOD: The Universe Nearby (2011 Jun 14)

Postby APOD Robot » Tue Jun 14, 2011 4:06 am

Image The Universe Nearby

Explanation: What does the universe nearby look like? This plot shows nearly 50,000 galaxies in the nearby universe detected by the Two Micron All Sky Survey (2MASS) in infrared light. The resulting image is anincredible tapestry of galaxies that provides limits on how the universe formed and evolved. The dark band across the image center is blocked by dust in the plane of our own Milky Way Galaxy. Away from the Galactic plane, however, each dot represents a galaxy, color coded to indicate distance. Bluer dots represent the nearer galaxies in the 2MASS survey, while redder dots indicating the more distant survey galaxies that lie at a redshift near 0.1. Named structures are annotated around the edges. Many galaxies are gravitationally bound together to form clusters, which themselves are loosely bound into superclusters, which in turn are sometimes seen to align over even larger scale structures.

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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby bystander » Tue Jun 14, 2011 4:09 am

I don't imagine you will dispute the fact that at present the stupid people
are in an absolutely overwhelming majority all the world over.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Beyond » Tue Jun 14, 2011 4:13 am

Seeing everything in the 'small' like that, it's almost hard to imagine the 'Bigness' of what it represents. :shock:
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Mactavish » Tue Jun 14, 2011 4:58 am

How "nearby"? I don't have a PhD in Astronomy, so don't understand all the techie talk.
Can you give me an idea in terms of millions of lightyears? Thanks.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby bystander » Tue Jun 14, 2011 5:25 am

Mactavish wrote:How "nearby"? I don't have a PhD in Astronomy, so don't understand all the techie talk.
Can you give me an idea in terms of millions of lightyears? Thanks.


CfA wrote:Today, astronomers unveiled the most complete 3-D map of the local universe (out to a distance of 380 million light-years) ever created. Taking more than 10 years to complete, the 2MASS Redshift Survey (2MRS) also is notable for extending closer to the Galactic plane than previous surveys - a region that's generally obscured by dust.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby garry » Tue Jun 14, 2011 9:48 am

Alton Arp, an astronomer of note, showed how we measure distance using redshift techniques can be seriously questioned. If so the current map of galaxies shown is not an exact map, but an estimation that may be flawed. If we completely understood the structure & workings of the Universe, why bother with being a lowly astronomer?
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Steve S » Tue Jun 14, 2011 11:05 am

Nearby Universe?!? My dictionary defines universe as "All existing matter and space considered as a whole; the cosmos." Has this definition 'slipped' or is it misused? I have heard terms like 'Super-Group' and "Super Bubble" used for groupings of galaxies but I thought that Universe was the ultimate, a unique term referring to EVERYTHING!
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby rstevenson » Tue Jun 14, 2011 11:29 am

If I say "nearby neighbourhood" I will be understood to mean only that portion of my neighbourhood which is relatively close to me, and not the entire area that might be my full neighbourhood. Language is not bound in a straitjacket; it is flexible and capable of great subtlety.

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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby ben.gt » Tue Jun 14, 2011 11:44 am

would be great to have this data in rotatable, zoomable 3d.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby davidgin50 » Tue Jun 14, 2011 11:51 am

I just did some primary school calculations on the back of an envelope and reckon that map represents a little under 2% of the whole - is that about right?
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby orin stepanek » Tue Jun 14, 2011 1:09 pm

you can get some stunning photos from 2mass image gallery! Might be worth downloading a shortcut. :wink: http://www.ipac.caltech.edu/2mass/gallery/
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby neufer » Tue Jun 14, 2011 1:13 pm

davidgin50 wrote:
I just did some primary school calculations on the back of an envelope and reckon that map represents a little under 2% of the whole - is that about right?

    I get more like ~ 0.001% :arrow:
http://apod.nasa.gov/apod/ap071107.html wrote:
Galaxies within one billion light years
= a redshift of about 0.1

http://en.wikipedia.org/wiki/Observable_universe wrote:
<<The current comoving distance to the particles which emitted the CMBR, representing the radius of the visible universe, is calculated to be about 14.0 billion parsecs (about 45.7 billion light years), while the current comoving distance to the edge of the observable universe is calculated to be 14.3 billion parsecs (about 46.6 billion light years).>>
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Chris Peterson » Tue Jun 14, 2011 2:19 pm

garry wrote:Alton Arp, an astronomer of note, showed how we measure distance using redshift techniques can be seriously questioned. If so the current map of galaxies shown is not an exact map, but an estimation that may be flawed. If we completely understood the structure & workings of the Universe, why bother with being a lowly astronomer?

Halton Arp was well respected, but has generally lost a good deal of that because of his refusal to adapt his ideas to new evidence- a very unscientific way of thinking. Nothing that Arp proposed regarding redshift has held up to close examination, yet Arp continues to try bending the data to fit his ideas, not the other way around. In fact, virtually nobody seriously questions the utility of the redshift-distance relationship, and it is unlikely that this map is flawed in some fundamental respect.

Surely, nobody is suggesting that we completely understand the structure and workings of the Universe? The data contained in this image is useful for placing bounds on some of the unknowns, which in astronomy, is one of the most common ways that knowledge advances.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Chris Peterson » Tue Jun 14, 2011 2:23 pm

neufer wrote:I get more like ~ 0.001%

And of course, that's just for the observable Universe. If we consider the entire Universe, it's almost certainly a tiny fraction even of that... if not an infinitesimal one!
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby bystander » Tue Jun 14, 2011 2:43 pm

neufer wrote:I get more like ~ 0.001%

That's just using a simple ratio of the radii (radiuses?). Since we are dealing with volume, shouldn't that be cubed?
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby neufer » Tue Jun 14, 2011 3:57 pm

bystander wrote:
neufer wrote:
I get more like ~ 0.001%

That's just using a simple ratio of the radii (radiuses?). Since we are dealing with volume, shouldn't that be cubed?

The radii are in a ratio of 1 to 46.

The volumes are in a ratio of 1 to 463.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby deathfleer » Tue Jun 14, 2011 4:07 pm

what's the scale of today's map, is it 1:1,000,000,000,000,000,000,000,000,000,000
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby bystander » Tue Jun 14, 2011 4:13 pm

neufer wrote:The radii are in a ratio of 1 to 46.

The volumes are in a ratio of 1 to 463.

For this, the radii are in a ratio of 380 × 106 to 46.6 × 109

CfA wrote:… (out to a distance of 380 million light-years) …
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby neufer » Tue Jun 14, 2011 4:26 pm

bystander wrote:
neufer wrote:The radii are in a ratio of 1 to 46.

The volumes are in a ratio of 1 to 463.

For this, the radii are in a ratio of 380 × 106 to 46.6 × 109

CfA wrote:… (out to a distance of 380 million light-years) …

APOD Robot wrote:Image The Universe Nearby

Explanation: Bluer dots represent the nearer galaxies in the 2MASS survey,
while redder dots indicating the more distant survey galaxies that lie at a redshift near 0.1 [~ 109 lyrs]. >>
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Wolf kotenberg » Tue Jun 14, 2011 6:20 pm

Ok, I give up. Calling myself an insignificant one is far far too generous. Perhaps I should just sit down, preferably in Brazil, with an ice cold one in my hands, wait for Eta Carinae to shower me with whatever cosmic wave it wants to and always have access to APOD. and some farofa.
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby neufer » Tue Jun 14, 2011 6:30 pm

Wolf kotenberg wrote:
Ok, I give up. Calling myself an insignificant one is far far too generous. Perhaps I should just sit down, preferably in Brazil, with an ice cold one in my hands, wait for Eta Carinae to shower me with whatever cosmic wave it wants to and always have access to APOD. and some farofa.

That's the spirit :!:
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby SevenHerons » Tue Jun 14, 2011 9:12 pm

Wolf kotenberg wrote:Ok, I give up. Calling myself an insignificant one is far far too generous. Perhaps I should just sit down, preferably in Brazil, with an ice cold one in my hands, wait for Eta Carinae to shower me with whatever cosmic wave it wants to and always have access to APOD. and some farofa.




Let's have a convention. Where in Brazil?
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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby NoelC » Tue Jun 14, 2011 9:22 pm

If the speed of light is changing (in my mind another way to think of the "expansion" of space-time - am I way off base?), then is it really meaningful to think in terms of distance? Not to mention that the distances are virtually unimaginable anyway. I like that this map is presented in % of C as opposed to trying to describe things in terms of distance.

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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Chris Peterson » Tue Jun 14, 2011 9:49 pm

NoelC wrote:If the speed of light is changing (in my mind another way to think of the "expansion" of space-time - am I way off base?)...

I do think that's off base. The expansion has no connection with c, but only shifts the wavelength as the intervening space expands.

...then is it really meaningful to think in terms of distance?

There is some kind of meaning there, but perhaps it isn't so useful. Cosmologists generally look at z, the redshift, as the fundamental unit, and it isn't usually felt necessary to convert this to a distance- except in press releases <g>.

Not to mention that the distances are virtually unimaginable anyway.

Are they? I don't find it difficult at all to think in terms of billions of light years. These seem like natural and easy units for measuring the Universe. It's no different than thinking in fractions of nanometers for many atomic scale examples. I think the problem comes when people try to tie together units that are radically different, like directly comparing the distance to the supermarket to the distance across the observable Universe. But there's no need to do that.

I like that this map is presented in % of C as opposed to trying to describe things in terms of distance.

The map is not really showing a percentage of c. That would be a velocity. The map is showing redshift, which is a ratio of the apparent recessional velocity to c- a unitless value.
Chris

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Re: APOD: The Universe Nearby (2011 Jun 14)

Postby Wolf kotenberg » Tue Jun 14, 2011 10:21 pm

I decided while sitting in brazil sipping on a cold one, that no matter where I am, the universe is about 14 billion light years old.
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