I know we have "exoplanets" etc. but those are nouns for specific objects outside our solar system.

We have extraterrestrial for objects outside Earth's atmosphere, but I don't know if we have a general adjective for objects outside our solar system.

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    $\begingroup$ "Extrasolar" is the word you're looking for, and you've misspelled "exoplanets". $\endgroup$ – AtmosphericPrisonEscape Mar 26 '19 at 11:15
  • $\begingroup$ @AtmosphericPrisonEscape We don't say "extrasolar stars" or "extrasolar medium", I think the question is pretty interesting in fact. Also, the spelling was quickly corrected. $\endgroup$ – uhoh Mar 27 '19 at 0:22
  • $\begingroup$ Opposite to planets, stars are naturally extrasolar. For most of discussions, then galactic or extragalactic (to be intended within another galaxy, for objects) is what usually counts. $\endgroup$ – Alchimista Mar 27 '19 at 8:31

To cut it short, while there is no definitive term, things outside of our solar system is usually referred as Interstellar.

When we talk about things outside of our solar system, we either talk about other star systems (and their planets are called exoplanets as you mentioned) or we talk about interstellar medium.

The interstellar term was not used for objects until 2017, when we discovered Oumuamua. Now, any object that doesn't belong to or that did not originate in our solar system is designated as Interstellar. For that matter Oumuamua's official designation is 1I/2017, for which the I stands for interstellar.

Here I should note that planets that does not revolve around any star are called Rogue Planets.


As @AtmosphericPrisonEscape noted in comments, above, "Extrasolar" is the correct term. E.g., we refer to "extrasolar planets", not "interstellar planets."

"Interstellar" refers to things among the stars (Merriam-Webster: "located, taking place, or traveling among the stars especially of the Milky Way galaxy")

"Extrasolar" means "outside the Solar System." (Merriam-Webster: "originating or existing outside the solar system")

One distinction is that "interstellar" doesn't include all space outside the Solar System -- "Interstellar space" is usually spoken of as distinct from, and much smaller than, "Intergalactic space".

The original question asked for "a general adjective for objects outside our solar system" and that would be "extrasolar".

  • $\begingroup$ The term "interstellar planet" seems to be rare but when it is used it usually refers to planets that are not bound to a star (usually termed "free-floating" or "rogue" planets). $\endgroup$ – user24157 Mar 28 '19 at 18:58

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