# Why are the most distant galaxies "only" around 13 billion light years away?

According to Wikipedia's List of the most distant astronomical objects, the most distant galaxy (GN-z11) is estimated to be around 13.39 billion light years away from earth.

However, the observable universe has a diameter of 92 billion light years. I understand that galaxies needed some time to form, however I'm a bit confused by the fact that all of the objects are within the radius of 13.8 billion light years (which is the age of the universe). To me, it would make more sense if some objects would be also 20 or 30 billion light years away.

Are our telescopes simply not good enough to receive light from such far away galaxies or is there any "rule" that prevents galaxies to be farther away than the age of the univere in light years?

Also, if the second is true, how can astronomers know the universe is actually 92 billion ligt years across?

• how can astronomers know the universe is actually 92 billion ligt years across?” - They don’t. It is just a conclusion of the Friedmann cosmology that has been invalidated by the Hubble tension, Axis of Evil, the flatness problem, the infinite Big Bang problem, etc. May 1, 2020 at 15:07

It seems that there are two distance measures

1) Light Travel Distance

Basically the light travel distance $$(D)$$ is equal to the light travel time ($$t_o - t_e)$$ times the speed of light ($$c$$).

$$D = c \times (t_o-t_e)$$

2) The Proper distance

In this case we are using the distance measured by,

$$d_p = a(t_0)r$$ where $$r = c \int_0^a \frac{dt}{a(t)}$$ and $$a(t_0)=1$$

In the wikipedia page that you shared the distance is given in terms of the light travel distance.

For this case, the light travel distance means that the object formed around $$13.39$$ billion years ago. It does not say that the object is $$13.39$$ billion light years away (which I admit using this convention is pretty confusing)

The object is actually around $$32$$ billion light year away which you can see this information when you look at the wikipedia page of that galaxy GN-z11.

• Distance measurement on a cosmological scale can be confusing! Distance measures (cosmology) describes several distance (and time) scales commonly used in cosmology. May 1, 2020 at 11:04