A short, curated guide — not an automatic related dump. Figures come from SubMouse's safe-for-work directory when we have them.
r/nasa (about 5.9M members, directory rank #139) covers NASA news, events and current and future missions. Wider space and astronomy rooms cover more.
Stay on nasa for the agency and its missions. Use space for astrophysics, cosmology and exploration in general, spacex for the company SpaceX, and Astronomy for observing and celestial study.
r/nasa — NASA
r/NASA is for anything related to the National Aeronautics and Space Administration; the latest news, events, current and future missions, and more.
/r/space: news, articles and discussion
When to choose it: You want space science and exploration beyond one agency.
Why it is here: Listed as related. Public description: astrophysics, cosmology, space exploration and planetary science (about 28.0M members, rank #16).
How it differs from r/nasa: All space versus NASA.
r/SpaceX, the premier SpaceX discussion community
When to choose it: Your topic is SpaceX launches and vehicles.
Why it is here: Public description: the largest fan-run SpaceX discussion board (about 3.7M members, rank #270).
How it differs from r/nasa: A private company versus NASA.
Astronomy
When to choose it: You are interested in observing or studying celestial objects.
Why it is here: Public description: the amateur hobby and scientific study of celestial objects (about 3.2M members, rank #333).
How it differs from r/nasa: Astronomy hobby versus agency news.
Run the automatic finder for r/nasa (results are matched from our directory; that page is not indexed): Find related to r/nasa.
Members and public descriptions come from SubMouse's safe-for-work directory (as of 2026-11-02 UTC); 7-day growth measured from 2026-10-26. Posts/day and culture claims appear only when we have them — missing fields stay n/a. Directory rank is listing order. Communities outside the published Top 100 open in the info tool instead of a full community page. Guide updated 2026-11-07.