Question

How many AU is the nearest Galaxy from the milkyway?

Answer 1

It depends what you mean by nearest galaxy, but the conversion factor between light years and AU is about `63000`

Explanation:

Let's work out a conversion factor between light years and AU first.

The Sun is roughly `93000000` miles from the Earth and light travels at about `186000` miles per second.

So `1` AU is about `500` light seconds.

There are `86400` seconds in a day and about `365.25` days per year, hence:

`86400 * 365.25 = 31557600" "` seconds per year.

Dividing this by `500` we arrive at:

`31557600/500 = 63115.2 ~~ 63000" "` AU per light year.

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How far away is the nearest galaxy from the Milky Way?

The very nearest galaxy would be one of the small satellite galaxies.

There are about `50` galaxies within about `1.4` million light years of the Milky Way. The closest are about `1000` light years from the edge, which by our reckoning would be about `63000000 = 6.3 xx 10^7` AU from the edge.

Perhaps of more interest is the distance to the Andromeda galaxy, our largest neighbour in the Local Group. This is about `2.5` million light years away, which would make it about `160` billion AU away.