How far are other galaxies from earth?

1 Answer
Dec 26, 2015

Between 25×103 light years (nearest) and 13.3×109 light years (farthest)

Explanation:

The nearest would be a satellite galaxy of the Milky Way.

There seem to be two possible candidates:

(1) Canis Major Dwarf Galaxy / Canis Major Overdensity.

This is a disputed dwarf irregular galaxy about 25kly (thousand light years) from Earth.

(2) Saggitarius Dwarf Spheroidal/Elliptical Galaxy about 70kly from Earth.

The nearest major galaxy is the Andromeda Galaxy M31, situated about 2.5Mly (million light years) from Earth. At about 220kly in diameter, it is definitely larger than the Milky Way galaxy.

The third largest spiral galaxy in the Local Group is the Triangulum Galaxy at a distance estimated to be somewhere between 2.38Mly and 3.07Mly, with a diameter of about 60kly.

The most distant known galaxy is MACS0647-JD at a distance of 13.3Bly (billion light years), meaning that we see it as it was about 420 million years after the Big Bang.

Given that a light year is about 5.8785×1012 miles, that means that our nearest neighbouring galaxy is about 1.5×1017 miles (Canis Major Dwarf Galaxy) or 4×1017 miles (Saggitarius Dwarf Spheroidal Galaxy) away and the most distant known galaxy is 7.8×1022 miles away.

Actually the (comoving) distance to the farthest galaxy is considerably more than this due to the expansion of the universe, probably closer to 44.8×109 ly or 2.6×1023 miles.