# Presence of planets in Milky Way and other galaxies

Are there only planets in the Milky Way galaxy, or are there other planets in other galaxies?

If planets are only in the Milky Way, why aren't there planets in others?

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Come on... Really? You couldn't bother to google 'planet'? Here you go... en.wikipedia.org/wiki/Planet. –  Danu Aug 22 at 16:41
This question appears to be off-topic because it does not meet the minimum level of research effort to make for an acceptable question. –  Danu Aug 22 at 16:42
I would agree that there is little research effort, but I can understand the motivations for asking it. After all, how many extra-galactic planets have we found? Logic says that there should be as many in every other galaxy as there are in the Milky Way, but we haven't had much success finding them. But yes, logic would answer the question pretty well. By the way, why not ask this on the Astronomy SE in the first place (note: not a suggestion)? –  HDE 226868 Aug 22 at 16:50
@Danu I couldn't find this specific point on the Wikipedia page either. This is a reasonable enough (if simple question). –  Emilio Pisanty Aug 22 at 17:24
@Mehrdad: I think the fascination is twofold. (1) we've only just developed technology to detect them, so it's a growth industry just now. (2) we're interested to know how common earth-like planets are, because we're interested in life and the only kind of life we can confidently predict is possible, is the kind of life we see on earth. Note that finding extrasolar gas giants is already pretty boring to general news reporters, they want a better chance of liquid water than ever before or they're not running it. Planets with exotic chemistry also stand a chance, e.g. giant diamonds ;-) –  Steve Jessop Aug 22 at 23:01

Observing planets in other galaxies is really hard to do because they are so far away and planets are so small. One of our closest neighbors, the Andromeda Galaxy (also called M31), is about $10^{19}$ km away (just under 780 kpc), so finding a planet the size of Jupiter (roughly $10^5$ km diameter) is pretty tough (radius to distance is very small). Even the closer neighbors, the Magellanic clouds at distances of 50 and 60 kpc (LMC & SMC respectively), are still over $10^{18}$ km away so finding planets orbiting stars there are equally challenging.