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

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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?
 

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  • #2
BvU
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At 17 Gly is where it is now, not at the time when it emitted the light that is captured in the picture.
 
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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'.
 
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Bandersnatch
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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
 
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