Starship Asterisk*

A Redshift Lookup Table for our Universe

Explanation: How far away is "redshift six"? Although humans are inherently familiar with distance and time, what is actually measured for astronomical objects is redshift, a color displacement that depends on exactly how energy density has evolved in our universe. Now since cosmological measurements in recent years have led to a concordance on what energy forms pervade our universe, it is now possible to make a simple table relating observed cosmological redshift, labeled "z", with standard concepts of distance and time, including the extrapolated time since the universe began. One such table is listed above, where redshift z is listed in the first and last columns, while the corresponding universe age in billions of years is listed in the central column. To find the meaning of the rest of the columns, please read the accompanying technical paper. Although stars in our galaxy are effectively at cosmological redshift zero, the most distant supernovae seen occur out past redshift one, which the above chart shows occurred when the universe was approximately half its present age. By contrast, the most distant gamma-ray bursts yet observed occur out past redshift six, occurring when the universe was younger than one billion years old, less than 10 percent of its present age.

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I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

very nice. the original paper has added scales for small z and recent lookback times.
i hope ned wright soon updates his cosmological calculator, which i've found very useful ...

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

I thought the redshift was measure because we know from how much the carbon spectral line has been 'reddened'. But how comes we can figure it out in a simple gamma-ray burst? I thought they cannot show any spectral line, or do they?

Beyond wrote: I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

LOL - I never shifted until I was 40 and now I try to shift sometimes even if I'm on automatic.

ALSO, A BIG THANK YOU APOD FOR POSTING THE CHART, It is very impressive.

If the table head included units, it would be perfect. Thank you APOD of sharing this!

SebastienP wrote:I thought the redshift was measure because we know from how much the carbon spectral line has been 'reddened'. But how comes we can figure it out in a simple gamma-ray burst? I thought they cannot show any spectral line, or do they?

From what I understand from this paper, they use the absorption of the optical afterglow to determine the redshift.

Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

I still shift....my Z is a 4 speed.

Like to DRIVE to Jupiter someday...but with the price of gas....
:---[===] *

Why is "2013 April 8" off the scale on the age chart

(Can I postpone now sending in my income taxes?)

Boomer12k wrote:

Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

I still shift....my Z is a 4 speed.

Like to DRIVE to Jupiter someday...but with the price of gas....
:---[===] *

Seems like you're already there to me!

Something seems wrong with the time scale. At the low z end, the time traveled seems to jump exponentially with an increase in z, yet at the higher Z end, the time traveled increases by quite a bit less with an increase in z. Wouldn't it be the other way around, since the farther away the object is, the faster it is receding?
I know neuf will straighten me out on this!

It's a nomograph harking back to the sliderule era bc (before computers). You lay a straight-edge across between z values and read values of the scales in between. For example, for z = 2, I read H = 204, dm = 46, age = 3.3, time = 10.5, and so forth. Do these numbers sound right? My engineering instincts quail at the thing, however. Units are not shown! The author may show how to use it somewhere, but I didn't look that far into it.

Never mind. The objects ARE receding faster, as indicated by the red shift.

drollere wrote:very nice. the original paper has added scales for small z and recent lookback times.
i hope ned wright soon updates his cosmological calculator, which i've found very useful ...

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

What's to update? His calculator gives exactly the same values as today's calculator. Maybe you want the default hubble and omega values updated so you don't have to type them in?

stephen63 wrote:Never mind. The objects ARE receding faster, as indicated by the red shift. :derp:

Well, sort of. Keep in mind that cosmological redshift isn't an indicator of how fast objects are receding (which would be Doppler redshift), but of the amount that space has expanded in the time that the light has been traveling. The distinction can be subtle, but it's important.

This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.

http://archive.ncsa.illinois.edu/Cyberi ... mpany.html

But after about 300,000 years, the opaque soup of nuclear matter and radiation began to clear. By this time, the temperature of the universe dropped to 3,000 K. ... The vast sea of photons created during the earliest epochs prior to recombination persist to this day, in the form of cosmic microwave background that pervades the universe. No longer so energetic after being stretched by the expansion of the universe ... this radiation has cooled to a chilly 2.73 K

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

But even though the temperature of the Universe changes as it evolves, with TCMB = To (1+z), the Universe looks isothermal because the redshifting of radiation makes the warmer but redshifted distant Universe appear to have exactly the same temperature as the Universe today.

The CMBR has a thermal black body spectrum at a temperature of 2.725 K, so it peaks in the microwave range frequency of 160.2 Ghz(1.9 mm wavelength).

http://www.universetoday.com/79777/cosm ... radiation/

So, at what wavelength(s) would the
Cosmic Microwave Background originally have been emitted?  And what would its redshift be?

Can anyone help me?
Margarita

MargaritaMc wrote:This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.

That is your answer. The CMB is not seen as one wavelength today, because it was not emitted as a single wavelength. The CMB is observed as a blackbody spectrum, which peaks at about 2 mm. That is the blackbody spectrum equivalent for a radiator at 2.7 K. When the photons were emitted, the source temperature was about 3000 K, meaning the spectrum peaked at a bit under 1 micrometer, just into the near IR. Visually, the light would have appeared warm white.

The ratio of current peak wavelength to emitted peak wavelength is about 1100, which is therefore the redshift of the CMB.

MargaritaMc wrote:
So, at what wavelength(s) would the
Cosmic Microwave Background originally have been emitted?  And what would its redshift be?

https://en.wikipedia.org/wiki/Redshift#Extragalactic_observations wrote:
<<The most distant objects exhibit larger redshifts corresponding to the Hubble flow of the universe. The largest observed redshift, corresponding to the greatest distance and furthest back in time, is that of the cosmic microwave background radiation; the numerical value of its redshift is about z = 1089 (z = 0 corresponds to present time), and it shows the state of the Universe about 13.7 billion years ago, and 379,000 years after the initial moments of the Big Bang.>>

Thank you, Chris and Art, very much indeed.

Margarita

neufer wrote:Why is "2013 April 8" off the scale on the age chart

(Can I postpone now sending in my income taxes?)

“A citizen can hardly distinguish between a tax and a fine, except that the fine is generally much lighter.” – GKC ILN, 5/25/31

So, do you want a tax+fine?

Sorry to bother about what may have a trivial answer,

But what's up with the 1" scale and the kpc scales? Seems like (for the 1") 8.7 is the magic number, around which there's a kind of strange symmetry. I would have thought that there's a linear distance-size relationship. Obviously, there's something more complicated to this than meets the eye.

Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

Well, shifting in the Red is a feat that takes large amounts of Dark Energy to accomplish and unfortunately most Datsun 280Z's still run on Regular energy

stephen63 wrote:Never mind. The objects ARE receding faster, as indicated by the red shift.

I don't think they are receding faster than my hair line

BMAONE23 wrote:

Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red.

Well, shifting in the Red is a feat that takes large amounts of Dark Energy to accomplish and unfortunately most Datsun 280Z's still run on Regular energy

haha, that's why Boomer12k hasn't tried driveing his 280-Z to Jupitor. However, i see that he is only 15 posts away from 500, when one is declared to be officially insane, so who knows...