Apparent distance to far galaxies

  • I
  • Thread starter gptodd
  • Start date
  • Tags
    Galaxies
In summary, if we had a way to measure the apparent distance to 13 billion light-year galaxies, it would appear much closer due to the fact that the light left the source 13 billion years ago. The proper distance at emission of all the light being received now can be seen on a light-cone graph, with the oldest light being visible near the left edge of the x-axis and the farthest emitters emitting their light approximately 9 billion years ago.
  • #1
gptodd
2
0
TL;DR Summary
How far away were galaxies when they emitted the light we now see?
If we had a way to measure the apparent distance to 13billion light year galaxies (parallax or something) what would it be? The light left the source 13 billion years ago, so it would appear much closer.
I can't find an answer and I'm hoping you know.
 
Astronomy news on Phys.org
  • #2
Hi, gptodd. Welcome to PF.

The proper distance at emission of all the light being received now is shown on the light-cone graph below:
1600812950738.png

Think of it as tracing all the light from all the galaxies which were emitting at different times on the x axis, and which we observe now (at the 13.8 point on the x axis). So e.g. a galaxy which emitted light 2 billion years ago (11.8 Gy after the big bang), and whose light we are just receiving, was approx 1.75 billion light years distant.
The oldest light we can see, from the CMB, would be near the left edge of the x-axis (at the ~380 thousand point, translating to approx. 44 million light-years on the y axis).
Whereas the farthest emitters emitted their light approximately 9 billion years ago, when they were less than 6 Gly distant.
 
  • #3
Thank you so much!
-gptodd
 

FAQ: Apparent distance to far galaxies

1. What is the apparent distance to far galaxies?

The apparent distance to far galaxies is the distance that we observe them to be from Earth, based on the light that reaches us. This distance is affected by factors such as the expansion of the universe and the speed of light.

2. How do scientists determine the apparent distance to far galaxies?

Scientists use various methods to determine the apparent distance to far galaxies, including redshift measurements, standard candles, and parallax measurements. These methods involve analyzing the light emitted from the galaxies and comparing it to known values and patterns.

3. Why is the apparent distance to far galaxies important?

The apparent distance to far galaxies is important because it helps us understand the size and structure of the universe. It also allows us to study the evolution of galaxies and the expansion of the universe.

4. Can the apparent distance to far galaxies change over time?

Yes, the apparent distance to far galaxies can change over time due to the expansion of the universe. As the universe expands, the light from these galaxies has to travel a longer distance to reach us, making them appear farther away.

5. How do scientists account for the expansion of the universe when measuring the apparent distance to far galaxies?

Scientists use a mathematical model called the Hubble-Lemaître law to account for the expansion of the universe when measuring the apparent distance to far galaxies. This law takes into account the redshift of light from these galaxies and allows for more accurate distance measurements.

Similar threads

Replies
12
Views
1K
Replies
7
Views
1K
Replies
6
Views
2K
Replies
1
Views
1K
Replies
30
Views
4K
Replies
1
Views
1K
Replies
4
Views
2K
Replies
13
Views
2K
Back
Top