<p>The redshift of the quasar is <a href="https://research.ast.cam.ac.uk/lensedquasars/indiv/2M1310-1714.html" rel="nofollow noreferrer">1.975</a>, so it is nowhere near the edge of the observable universe.</p>
<p>17 billion light years is the comoving distance (i.e. where it is now), as you can confirm with <a href="http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html" rel="nofollow noreferrer">this cosmology calculator</a>.</p>

CC BY-SA 4.0
2021-08-26T10:12:25.860Z
+1  That's what I was looking for!  Where did you find the redshift?
Dave Gremlin
CC BY-SA 4.0
2021-08-26T12:15:25.437Z
@DaveGremlin link added
ProfRob
CC BY-SA 4.0
2021-08-25T23:20:06.417Z
2021-08-26T12:15:06.580Z
2021-08-26T12:15:06.580Z
ProfRob
<p><a href="http://www.sci-news.com/astronomy/quintuply-imaged-quasar-09938.html" rel="nofollow noreferrer">This Einstein ring</a></p>
<p><a href="https://i.sstatic.net/7ES7c.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7ES7c.png" alt="enter image description here" /></a></p>
<p><em>Image credit: NASA / ESA / Hubble / T. Treu / Judy Schmidt</em></p>
<p>shows multiple images of the quasar <a href="https://esahubble.org/images/potw2132a/" rel="nofollow noreferrer">2M1310-1714</a>.  Its distance is quoted at 17 billion light years and although the age of the universe is around 13.8 billion light years old, when the comoving distance is taken into account, <a href="https://en.wikipedia.org/wiki/Observable_universe" rel="nofollow noreferrer">the distance to the edge of the observable universe</a> is 46.6 Gly.</p>
<p>However, I keep coming across a link to  Ned Wright's <a href="http://www.astro.ucla.edu/%7Ewright/Dltt_is_Dumb.html" rel="nofollow noreferrer">&quot;Why the Light Travel Time Distance should not be used in Press Releases&quot;</a>.  The link is dead but the summary states</p>
<blockquote>
<p>Since public information offices in the US never want to mention the
redshift of an object, distances are usually given as light travel
time distances. This has one simple property: the distance in light
years is never greater than the age of the Universe in years.</p>
</blockquote>
<p>Is this the sense in which &quot;17 billion light years&quot; is being used here, and if so, what is the mechanism by which gravitational lensing can show objects beyond the 46.6 Gly boundary.  The only papers I can find are about imaging the ring, nothing about the distance to it or how that distance was determined.</p>

CC BY-SA 4.0
2021-08-25T21:19:14.643Z
"quoted at 17 billion light years"  That doesn't seem to be in the source.  Presumably that is a co-moving distance, because if it were a light travel time distance we would be seeing it at a time before the start of the universe . . . which isn't possible.
James K
<observable-universe><gravitational-lensing><quasars>
Is quasar 2M1310-1714 outside the observable universe?
Dave Gremlin
# Is quasar 2M1310-1714 outside the observable universe?

(Asked by: username_0 on 2021-08-25)

[This Einstein ring](http://www.sci-news.com/astronomy/quintuply-imaged-quasar-09938.html)

[![enter image description here](https://i.sstatic.net/7ES7c.png)](https://i.sstatic.net/7ES7c.png)

*Image credit: NASA / ESA / Hubble / T. Treu / Judy Schmidt*

shows multiple images of the quasar [2M1310-1714](https://esahubble.org/images/potw2132a/). Its distance is quoted at 17 billion light years and although the age of the universe is around 13.8 billion light years old, when the comoving distance is taken into account, [the distance to the edge of the observable universe](https://en.wikipedia.org/wiki/Observable_universe) is 46.6 Gly.

However, I keep coming across a link to Ned Wright's ["Why the Light Travel Time Distance should not be used in Press Releases"](http://www.astro.ucla.edu/%7Ewright/Dltt_is_Dumb.html). The link is dead but the summary states

> Since public information offices in the US never want to mention the
> redshift of an object, distances are usually given as light travel
> time distances. This has one simple property: the distance in light
> years is never greater than the age of the Universe in years.

Is this the sense in which "17 billion light years" is being used here, and if so, what is the mechanism by which gravitational lensing can show objects beyond the 46.6 Gly boundary. The only papers I can find are about imaging the ring, nothing about the distance to it or how that distance was determined.

**Tags:** observable-universe, gravitational-lensing, quasars

> **Comments:**
> **username_1**: "quoted at 17 billion light years"  That doesn't seem to be in the source.  Presumably that is a co-moving distance, because if it were a light travel time distance we would be seeing it at a time before the start of the universe . . . which isn't possible.  

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## 1 answers

### Answer by username_2 on 2021-08-25. Score: 7 | Accepted answer

The redshift of the quasar is [1.975](https://research.ast.cam.ac.uk/lensedquasars/indiv/2M1310-1714.html), so it is nowhere near the edge of the observable universe.

17 billion light years is the comoving distance (i.e. where it is now), as you can confirm with [this cosmology calculator](http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html).

> **Comments:**
> **username_0**: +1  That's what I was looking for!  Where did you find the redshift?  
> **username_2**: @username_0 link added  

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