Question 1

What counts as a neighbour?

Accepted Answer

The Milky Way is the largest member of a group of a few dozen galaxies bound together by gravity, most of them dwarfs orbiting either us or Andromeda. Those dwarfs fill the top of this list, and the first large galaxy on it is Andromeda itself.

Question 2

Why are the nearest ones so hard to see?

Accepted Answer

Because the closest are small, faint and spread thin — and some of them lie behind the crowded plane of our own galaxy, where dust hides them. Several were only found in the last few decades, and more are still being discovered.

Question 3

How is the distance measured?

Accepted Answer

By parallax where the object is near enough — the shift in its apparent position as the Earth crosses its orbit, which is geometry and needs no assumptions. Beyond that, distance is inferred from how bright something of known luminosity appears, and the further out the ladder goes the more the uncertainty grows.

Question 4

How firm is the order?

Accepted Answer

Firmer at the top than at the bottom. Neighbouring rows often sit inside each other's error bars, so a swap between two adjacent entries is a revision rather than a correction. Each object's own page carries the figure with its uncertainty and the method it came from.

Question 5

Why are some galaxies missing?

Accepted Answer

Because this catalogue holds no distance for them. A row with an empty distance column cannot be ranked on it, so the list is the nearest of those measured rather than the nearest that exist.

Question 6

Which galaxy is nearest to the Milky Way?

Accepted Answer

The Canis Major and Sagittarius dwarfs are nearer still, but both are being torn apart and merged into our own, so whether they count as separate galaxies is a matter of definition. The nearest intact large galaxy is Andromeda, at about 2.5 million light years.

Question 7

Are they moving away from us?

Accepted Answer

Not these. The expansion of space carries distant galaxies apart, but a gravitationally bound group is held together against it — Andromeda is approaching at about 110 km/s, and current analyses give roughly even odds that the encounter a few billion years from now ends in a merger.

Question 8

Can any be seen without a telescope?

Accepted Answer

Three, in the right conditions: Andromeda from the northern hemisphere as a faint smudge on a dark night, and the Large and Small Magellanic Clouds from the southern hemisphere, which are obvious enough to have been mistaken for detached pieces of the Milky Way.

The nearest galaxies to the Milky Way

COMMON QUESTIONS