Most Distant Object

[Airbrush]

The 2004 story (see below) reported a gravitationally lensed galaxy, behind a cluster called Abell 2218, that has a record-breaking redshift of 7.0.

 

“We are confident it is the most distant known object,” California Institute of Technology astronomer Richard Ellis said of the galaxy, which lies roughly 13 billion light-years from Earth. Put another way, the light traveled for 13 billion years to reach Earth."

 

The error in his report states it IS roughly 13 Billion LY from Earth, but it is really light that left it about 13 Billion years AGO. It is much further away now. Is there a general rule-of-thumb for converting 13 Billion years AGO to a current distance from Earth? Could we just double 13 Billion and call it about 26 Billion LY away, since it must be receding at nearly light speed? I have seen formulas for computing current distances, but the math is beyond me.

 

http://www.msnbc.msn.com/id/4274187/

[NowThatWeKnow]

If the light took 13 billion light years to get here, then you are seeing light that came from a galaxy when it was only 3.3465 Gly away. That galaxy is now 29.701 Gly away from us. Space had an expansion rate of 8.875 times while the light traveled.

http://www.astro.ucla.edu/~wright/DlttCalc.html

If you put 13 in the left box that says "light travel time in Gyr" and click flat, You will see where the #'s came from. The expansion of space is z + 1.

[Airbrush]

Thanks for your help NowThat. The math I had trouble with was exactly your illustration and I remember discussing exactly this with you on Historychannel.com. I finally figured out where you got 29.7 Gly. Gly is new terminology to me. "Gly" must mean giga light years.

 

So, for us newbies, when reading about objects that are on the edge of our visual horizon, about redshifts of 6.5 or higher, a good rule of thumb is take the time the light left in the past and multiply it by 2.3. 13 billion years ago X 2.3 = 30 Billion light years away NOW (approx). That discovery is over 4 years old, so I believe we may not ever find anything much further away than that. Right?

[NowThatWeKnow]

Gly is billion light years (see legend on calculator site). "Angular size distance D" is the distance the galaxy was away from us when the light was emitted. z at the top right is red shift and z + 1 is the expansion factor. "comoving radial distance" is the galaxies current location.

[Martin]

Airbrush and NowThat, thanks for excellent question and response.

Here is an estimated z~7.6 example. But was reported only last year so caution would be reasonable.

 

http://arxiv.org/abs/0802.2506

[Airbrush]

Interesting news Martin. From reading the article I am only able to gather that it has a redshift (z) of ~7.6, plus or minus 0.4. Does it say how old the light is? Anyone want to venture an estimate of its' current distance from us?

 

Why don't they give these astonishing objects on the edge of our visual horizon names? What is the highest redshift possible for an object to still be visible?

[Martin]

What is the highest redshift possible for an object to still be visible?

 

About z = 1090.

 

This corresponds to the moment in time when the universe became transparent. Not an exact moment but an interval of a few years during which it cooled enough so the gas that filled space was not glowing hot and able to scatter light.

 

If an object had existed before that time it would not be visible to us by electromagnetic radiation (light, radio waves etc) because the light would have been immediately blocked and scattered by the glowing hot gas. Space wasnt transparent.

 

So seeing stuff with z > 1090 is ruled out, if by seeing you mean with EM radiation.

 

And in fact we DO see back to around z = 1090 namely we see the hot glowing gas itself, just as it was becoming transparent.

This happened at around 3000 kelvin. What we see, when we look at maps of the CMB (those mottled red and blue ovals) is the light radiated by that 3000 kelvin glowing gas. So we are actually observing that matter, that gas.

 

The typical wavelength of thermal glow at 3000 kelvin is around 2 micrometers. The universe has expanded by a factor of about 1000 since that time, distrances and wavelengths have expanded by the same 1+z factor. Well if you multiply 2 micometers by 1000 you get 2 millimeters. That is a typical wavelength observed in the CMB.

 

It is the thermal glow of something at a temperature of approximately 3000/1090 kelvin. That is, 3000 K divided by the 1+z factor.

 

========================

Now I'm somewhat remorseful I jumped in on this thread because NowThat was taking care of business very well, as it stood.

 

There is more to say. The matter that we are now seeing when we map the CMB used to be separated from our matter (at the time it radiated the light) by a distance of 42 million lightyears, a comparatively tiny distance. But that distance was increasing rapidly at the time and we are only just now getting the light from that stuff. What remains of that hot gas, that we are seeing via the CMB, is probably just stars and galaxies like ours, because the stuff cools and condenses over time (like watervapor making snowflakes). And it is now, today, as we get the light from it now become CMB radiation, at a distance of 46 billion lightyears. That is, the distance from our matter to that matter has increased by a factor of 1090.

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Merged post follows:

Consecutive posts merged

 

And of course when the people on those galaxies, now 46 billionlightyears from here, look in our direction they see CMB which is the glow emitted from our matter back then when space became transparent. It is reciprocal.

Interesting news Martin. From reading the article I am only able to gather that it has a redshift (z) of ~7.6, plus or minus 0.4. Does it say how old the light is? Anyone want to venture an estimate of its' current distance from us?

 

Ned Wright says we better not trust that 7.6 until more work has been done.

It was reported last year. Let's suppose it is confirmed by more observation and it turns out to be just what they estimated, namely 7.6 (but hopefully with a narrower errorbar or confidence interval or whatever.)

 

Then how do we answer your question about how far away it is now? And how far away was it when it emitted the light that we are now getting from it?

 

Can anybody supply these figures? I should give NowThat a chance since it's partly his thread.

 

Hint: google "wright calculator" and you get the standard version that you can plug 7.6 directly into, and not bother with light travel time.

 

================================

 

Why don't they give these astonishing objects on the edge of our visual horizon names?

that's a delightful idea. The codenumber tag they gave to this object is

A1689-zD1. The first part is meaningful because Abell 1689 is a massive cluster of many galaxies forming a superb gravitational lens.

So what these guys are doing is methodically examining the tiny much more distant objects that are way out behind Abell 1689. They get magnified by the Abell 1689 lens making it possible to study their spectra even tho they would normally be too far.

 

So if you wanted to name it, you could start by thinking of a name for that vast noble and dense cluster of galaxies called by its catalog number A1689.

Whatever you think of would be like a family name for the little specks out behind the lens, and then there'd be some individual specifier possibly more memorable than "zeedee-0ne" or "zipdog-uno"

 

Abell 1689 has name recognition:

http://en.wikipedia.org/wiki/Abell_1689

"Abell 1689 is a galaxy cluster in the constellation Virgo. It is one of the biggest and most massive galaxy clusters known and acts as a gravitational lens, distorting the images of galaxies that lie behind it. It is 2.2 billion light years ... away from earth."

 

Was 1689 the year Newton published the Principia? No, that was more like 1687, but in 1689 he took a seat in Parliament.

"Newton was also a member of the Parliament of England from 1689 to 1690 and in 1701, but his only recorded comments were to complain about a cold draught in the chamber and request that the window be closed."

http://en.wikipedia.org/wiki/Isaac_Newton

 

1689 was a landmark year for the Parliament and Britain as a whole, they deposed James II and proclaimed William and Mary the official royal couple. This was called the "Glorious Revolution" and it finally ended some 50 years of turmoil and religion-inspired civil war that had begun with Cromwell. Amidst all these great events Newton, the man of science, remarked that the chamber was drafty and asked them to close the window.

 

So I guess I would suggest the name Commons for that lensing cluster Abell 1689. And I would probably call that alleged 7.6 thing by a name like

Commons Zipdoguno. This is by way of challenging you to come up with a better suggestion

Edited February 27, 2009 by Martin
Consecutive posts merged.

[NowThatWeKnow]

Now I'm somewhat remorseful I jumped in on this thread because NowThat was taking care of business very well, as it stood...

 

...Can anybody supply these figures? I should give NowThat a chance since it's partly his thread.

 

z=7.6 puts the galaxy 3.4208 billion light years away when it omitted the light we see today.

 

Martin, much of what I know about cosmology has come from reading your post. It will be awhile before I can fill in for you so don't leave me hanging too long. I probably know about [math]7.6^{-10}[/math] as much as you.

[Martin]

OK let me check. Google "wright calculator"....first hit...put

7.6 in the z box...

 

distance now comes up 29.4 billion lightyears

 

distance then (ang. size dist.) comes up 3.42 billion lightyears

 

Just what you said.

 

I'm old and have limited energy. It really helps when new people know some of the quantitative stuff and respond to whatever extent. thanks.

Edited February 27, 2009 by Martin

[Airbrush]

I found a 2-12-08 story with a name for that very early galaxy, A1689-zD1, that is magnified ten times by the gravitational lensing of Abell 1689.

 

http://www.nasa.gov/centers/jpl/news/Spitzer20080212.html

 

The light originated from A1689-zD1 about 700 Million years after the Big Bang and is now about 12.8 Billion years old. It is among the first galaxies to form after the Dark Ages, which lasted from about 400,000 years until about one Billion years after the Big Bang. I didn't see any redshift number, but it must be the one Martin introduced here with a redshift of ~7.6 and the galaxy is now almost 30 Billion LY from us.

 

How much further is the CMB if it has a redshift of 1090, which is 136 times higher redshifted than z = 8?

Edited March 3, 2009 by Airbrush

[Martin]

...with a redshift of ~7.6 and the galaxy is now almost 30 Billion LY from us.

 

How much further is the CMB if it has a redshift of 1090, which is 136 times higher redshifted than z = 8?

 

Airbrush you'v got to learn to use the Wright calculator. It's sooooo easy!

 

z= 7.6 means something is now 30 billion lightyears away.

z= 1090 means something is now 46 billion lightyears away.

 

Please pick up the habit of doing this for yourself, as an astronomer would.

 

Google "wright calculator". The top hit is:

http://www.astro.ucla.edu/~wright/CosmoCalc.html

 

 

Go there and just type 1090 into the z-box, and press the button called "general". You will get the present day distance is 46 billion lightyears, plus some other information which may not mean anything to you for the moment.

[Airbrush]

z= 7.6 means something is now 30 billion lightyears away.

z= 1090 means something is now 46 billion lightyears away.

 

Interesting comparison! Does that mean that the current "edge" of the visible universe (the region of CMB) is about 50% further away than the furthest known galaxy that can be seen? Does that mean we probably will not see any galaxies with redshifts greater than 8, simply because the age of the universe would not allow it? Even using the greatest gravitational magnifier known Abell 1689?

[Martin]

z= 7.6 means something is now 30 billion lightyears away.

z= 1090 means something is now 46 billion lightyears away.

 

Interesting comparison! Does that mean that the current "edge" of the visible universe (the region of CMB) is about 50% further away than the furthest known galaxy that can be seen? Does that mean we probably will not see any galaxies with redshifts greater than 8, simply because the age of the universe would not allow it? Even using the greatest gravitational magnifier known Abell 1689?

 

This is a case where if you had used the calculator and put in those two redshifts (and also the other one you thought of) you would yourself have come up with an understanding of what limits the highest redshift galaxy we can hope to see, with whatever instruments.

 

Try it. You are pretty clearly intelligent, so you are crippling your mind if you don't make use of the numerical model. The wright calculator is a hands-on embodiment of the standard LCDM model. It tells other things besides distances. Put in some redshifts and see what kind of limit you can figure out by yourself.

 

Remember that anything remotely resembling what we think of as a galaxy is going to take at least half a billion years to form, out of the thin hot gas we see at z= 1090 and the almost uniformly spread out dark matter we can infer from the visible uniformity of the gas. Things take time to curdle, clump, come together.

[Airbrush]

I did just like you said Martin, and I now believe we will probably never find any galaxy or quasar with a red shift greater than 8, because before 13 Billion years ago was the Dark Ages. They also said that galaxies formed even before quasars.

[Martin]

smart inference.

I mean it. I'm not presuming to act condescending.

You can learn alot of stuff just playing around with the model.

If you ask questions about what some of the other output features are like e.g. "angular size distance" ask.

Some I don't happen to know. some I do