More questions for Graeme - The map of the observable universe.

[ChrisGreaves]

Science: The Map of the Observable Universe
Speaking of “cosmic perspectives,” professor Brice Ménard at Johns Hopkins University created this web-based Map of the Observable Universe. It’s a long, scrolling page in which each dot represents an entire galaxy—including one tiny pixel at the bottom representing our own Milky Way. As CNET observes, “With a single pixel, Ménard stunningly puts into perspective the cosmic brevity of everything we've ever truly known as human beings.”

I don't have any questions yet; I am still too busy scrolling up and down, and sideways, gob-smacked, as we say in the trade, at "Each point on this [[[scrollable]]] page is a real galaxy". But if you have a question, post it here; Graeme can put it on my tab ...
Cheers, Chris

[ChrisGreaves]

Question 1
"This map shows ... we see about 200,000 galaxies. This visualization ... about 10 degrees" So we would need 36 of these images to show all the galaxies? So roughly 7,200,000 galaxies were observed by the "telescope in New Mexico, USA"? What is a modern estimate of the number of galaxies today? I included a link to "The Galaxy Song" because I find it easier to remember songs, patterns of words set to music, than to remember the actual numbers.
Thanks in anticipation
Chris

[stuck]

Where's the option to get directions from my house to where ever takes my fancy?

Ken

[ChrisGreaves]

Where's the option to get directions from my house to where ever takes my fancy?

Hi Ken.
Right here.
Cheers, Chris

[ChrisGreaves]

Question 2
The left-hand side of the segment "full" has alongside the red-shift axis values ranging from 0.2 to 5. In what units are these values? Something like exponents/logarithms of wavelengths? Is the value at origin zero? What value lies beyond 5? Is it infinite - as in "the life of the universe", or some value that is like "division by zero"?

I understand that your effort in the project may not yet be recognized but I still think of you as knowing more about background to explanations than anyone else I know ...
Thanks in anticipation
Chris

[Graeme]

Question 1
What is a modern estimate of the number of galaxies today?

I expect the answer is, we don't know! The Hubble deep field image increased the estimate to 2 trillion:

https://www.nasa.gov/feature/goddard/20 ... ly-thought

The New Horizons mission downgraded that estimate:

https://www.nasa.gov/feature/new-horizo ... k-is-space

The JWST will probably shed more light on things.

Question 2
The left-hand side of the segment "full" has alongside the red-shift axis values ranging from 0.2 to 5. In what units are these values? Something like exponents/logarithms of wavelengths? Is the value at origin zero? What value lies beyond 5? Is it infinite - as in "the life of the universe", or some value that is like "division by zero"?

That's 5 questions!

1. That is redshift caused by universe expansion being used to measure distance. The Unit is Z,
2. The difference in the wavelengths of the emitted and detected light divided by the wavelength of the emitted light. This is written algebraically as z = Δλ/λ. (I had to look that up!)
3. Yes (https://lco.global/spacebook/light/redshift/)
4 and 5. A red shift of zero is the location of the observer. A red shift of 10 would mean the light has been travelling for 13 billion years. The maths breaks down after that! (Or, there was no light before that!)


Regards

Graeme

[ChrisGreaves]

3. Yes (https://lco.global/spacebook/light/redshift/)

Hi Graeme; I am still digesting your answers, but I took a quick look at LCO. Is this the sort of site that someone like you might access to make use of a serious telescope?
Thanks, Chris