How on Earth This is possible? (distance to a far galaxy)

In summary, the article discusses a study that proved Einstein's theory of general relativity holds true even beyond the solar system. The study focused on a galaxy called ESO 325-G004, located 450 million light years away, which was aligned with a more distant galaxy. Despite the immense distance of 17 billion light years, the study showed that the two galaxies were aligned to a tiny fraction of a degree. This alignm
  • #1
Prof Sabi
33
4
https://amp.scroll.in/article/88372...ivity-holds-true-even-beyond-the-solar-system

Read the Section in this link:
Cosmic alignment
The galaxy we investigated has the catchy name ESO 325-G004 – let’s call it E325. Located some 450m light years away, it is one of the closest examples of a rare cosmic alignment – sitting directly between us and a second, more distant, galaxy. The background galaxy in this case is some 17 billion light years further behind. The centres of these two galaxies are aligned to better than one ten-thousandth of a degree.

17 billion light years? Isn't the universe 13.7 billion years old?
 
Astronomy news on Phys.org
  • #2
At 17 Gly is where it is now, not at the time when it emitted the light that is captured in the picture.
 
  • #3
BvU said:
At 17 Gly is where it is now, not at the time when it emitted the light that is captured in the picture.
Need a lil elaboration :eek: ... as I am imagining in this way that the light from that Galaxy literally took 17 billion years to travel to us in with velocity 'c'.
 
  • #5
Prof Sabi said:
Need a lil elaboration :eek: ... as I am imagining in this way that the light from that Galaxy literally took 17 billion years to travel to us in with velocity 'c'.
Let's say the light is emitted at a distance D from the observer. In a non-expanding universe, that initial distance would remain constant in time, and it'd take t=D/c to cover the distance.
In an expanding universe, as the light travels, the distance D grows - both in the part that the light still has to cover, and the part already covered.
This means that the time needed to reach the observer is higher than t=D/c, and the distance at which the source galaxy ends up being by the time of reception is higher than the initial distance D.

edit: typo
 
Last edited:
  • Like
Likes alantheastronomer, davenn and jim mcnamara

1. How can we measure the distance to a far galaxy?

Scientists use a variety of methods to measure the distance to a far galaxy, such as the parallax method, standard candles, and redshift. The parallax method involves measuring the change in position of a nearby star relative to more distant stars as the Earth orbits the Sun. Standard candles are objects with known luminosity that can be used to determine distance based on how bright they appear. Redshift, or the stretching of light waves, can also be used to determine distance as objects that are moving away from us will have a higher redshift.

2. How accurate are these distance measurements?

The accuracy of distance measurements to far galaxies depends on the method used and the quality of data collected. For example, the parallax method is most accurate for nearby galaxies, while redshift measurements can have a margin of error of a few percentage points. However, advancements in technology and techniques have greatly improved the accuracy of these measurements in recent years.

3. Can we measure the distance to all galaxies?

Currently, scientists are able to measure the distance to a large number of galaxies in our observable universe. However, as our technology and methods continue to improve, it is possible that we may be able to measure the distance to even more distant galaxies in the future.

4. How does knowing the distance to a far galaxy help us understand the universe?

Knowing the distance to a far galaxy allows scientists to better understand the structure and evolution of the universe. By studying the distance to different galaxies, we can learn about the expansion of the universe, the distribution of matter, and the rate of star formation in different regions.

5. Are there any limitations to measuring the distance to far galaxies?

While our current methods for measuring the distance to far galaxies are highly advanced, there are still some limitations. For example, the accuracy of redshift measurements can be affected by factors such as the movement of galaxies and the effects of gravity. Additionally, as the universe continues to expand, the distance to far galaxies will continue to increase, making it more difficult to accurately measure their distance.

Similar threads

  • Astronomy and Astrophysics
Replies
12
Views
1K
  • Cosmology
Replies
11
Views
1K
Replies
4
Views
1K
Replies
13
Views
2K
Replies
8
Views
2K
  • Astronomy and Astrophysics
Replies
4
Views
6K
Replies
25
Views
2K
Replies
1
Views
1K
Back
Top