About r/space
In its own words:
Share & discuss informative content on: * Astrophysics * Cosmology * Space Exploration * Planetary Science * Astrobiology
The community was created on Jan 26, 2008, which makes it 18 years old. Since Oct 19, 2026, it has gained 3,894 subscribers (+0.01%). Among the 6 communities on our science list it is number 2 by size. Among the 11 communities on our space and astronomy list it is the largest. It sits just behind r/Jokes (#15) and ahead of r/DIY (#17) in our ranking.
What sets r/space apart
Relative to its huge audience, posting is calm — around 0.9 new posts a day per million members, which puts it in the quietest fifth of the Top 100. A good post has less competition here. Its rhythm is strongly tied to time zones: the busiest hour (12:00 UTC) sees about 5.3× as many posts as the quietest (00:00 UTC).
Subscriber growth
Between Sep 19, 2026 and Oct 29, 2026, r/space grew from 27,971,110 to 27,990,867 subscribers (+19.8K, +0.07%). That is about 494 new members per day. The chart uses our weekly snapshots (8 so far), so it gets longer every week.
Top posts on r/space this week
This week’s highest-ranked posts, in Reddit’s own order (collected Oct 29, 2026).
- Astronomer here! Big news- I am a winner this year for the Wendy and Eric Schmidt Awards for Excellence in Science Communications, in large part for my posts on Reddit!u/Andromeda321 · Oct 27 · image
- Toronto, Canada photographed from the International Space Stationu/astro_pettit · Oct 24 · image
- Road to the Galactic Center. Image by Michael Abramyan in Monument Valley Utah, USAu/ojosdelostigres · Oct 25 · image
- Peripheral but I think relevant: Patrick Stewart has died.u/Adeldor · Oct 29 · link
- Ultra High Resolution Moon - Zoom in as far as you can!u/Mindless-Farm-7881 · Oct 24 · image
- The moon tonight!u/peeweekid · Oct 25 · image
- NASA's Swift observatory is losing more than 3 km of height a day and is predicted to re-enter on 2 Novemberu/DiveLive · Oct 27 · link
- China’s top-secret spaceplane can’t hide in low-Earth orbitu/Dorian182 · Oct 28 · link
- [OC] Elephant’s Trunk Nebulau/Slow_Contribution114 · Oct 25 · image
- Black holes can merge. But can one black hole become two? Physicists have investigated when such an extraordinary event might be possible.u/LogicalDirect · Oct 26 · link
All-time top posts
The highest-ranked posts in the history of r/space, from 2017 to 2024, ranked by Reddit.
- I'm 17 years old and just finished building this 14.7" f/2.89 Newtonian reflector telescope. Despite its stubby size it collects roughly 2500 times more light than the human eye and is bigger than th…u/__Augustus_ · Mar 29, 2020 · 203,642 points · 5,058 comments · image
- First full-colour Image of deep space from the James Webb Space Telescope revealed by NASA (in 4k)u/GroundbreakingSet187 · Jul 11, 2022 · 184,348 points · 8,357 comments · image
- I took nearly 50,000 images of the night sky to make an 81 Megapixel image of Tuesday's moon. Uncompressed image linked in the comments. [OC]u/ajamesmccarthy · Feb 17, 2019 · 166,990 points · 3,924 comments · image
- By complete accident I captured a plane crossing in front of our sun. I was able to figure out exactly which flight it was and got connected with the pilot, who was thrilled.u/ajamesmccarthy · Jan 31, 2021 · image
- The clearest image of Mars ever taken!u/EarlyNeedleworker · Sep 15, 2019 · 148,676 points · 2,437 comments · image
- And just like that, a space race is born.u/Fizrock · Dec 10, 2017 · 131,953 points · 3,690 comments · image
- Astronomers Capture First Image of a Black Holeu/SpaceRustem · Apr 10, 2019 · 131,588 points · 6,323 comments · link
- I teamed up with a fellow redditor to try and capture the most ridiculously detailed image of the entire sun we could. The result was a whopping 140 megapixels, and features a solar "tornado" over 14…u/ajamesmccarthy · Mar 26, 2023 · 128,731 points · 3,486 comments · image
- Two years ago, I teamed up with a fellow redditor to try and take the most ridiculous moon shot we could come up with. Today, we proudly introduce our newest collaboration, a 174 megapixel look at ou…u/ajamesmccarthy · Aug 21, 2022 · 122,841 points · 2,322 comments · image
- Falcon Heavy has a successful launch!!u/SuperDuperJake2 · Feb 6, 2018 · 122,558 points · 7,198 comments · text post
What r/space talks about
We read the titles of 189 recent posts (Oct 21–Oct 28), the words that come up most are “moon”, “nasa”, “solar”, “universe” and “satellite”. Other frequent themes are telescope, lunar, orbit, star, data and spacex. Recurring phrases include “solar system”, “black holes”, “black hole” and “concept release”. By format, 34% are links, 28% are text posts and 27% are images.
Popular post flairs: Discussion (38), image/gif (37), paywall (1).
Activity and best time to post
r/space gets about 26 new posts a day. The public archive holds 498,760 posts and 10,043,978 comments in total, about 20.1 comments per post. Last week the busiest day was Sunday (36 posts) and the quietest was Monday (21). Posting peaks around 12:00 UTC and is lowest around 00:00 UTC.
Rules of r/space
The moderators of r/space list 14 rules. In short:
- Submissions must be related to Space/Cosmology
- No sensationalist/misleading/unscientific content or titles
- No spam/blogspam/paywalled/pirated content
- No petitions/surveys/crowdfunding
- No social media links
- No duplicate or re-hosted content
- Images are only allowed on Sunday UTC
- No low-effort or meme images are permitted at any time.
- If an image is not OC you must give credit to the original photographer.
- No low-effort/meme/joke/troll/insult comments
How to join
Open reddit.com/r/space and press “Join”. Read the community rules in the sidebar before you post: every subreddit is run by its own volunteer moderators.
Frequently asked questions
How big is r/space?
r/space has 27,990,867 subscribers (Oct 29, 2026), which makes it the #16 safe-for-work subreddit in the SubMouse ranking. It added 19,757 members between Sep 19, 2026 and Oct 29, 2026.
How old is r/space?
r/space was created on Jan 26, 2008, so it has been around for 18 years. The oldest post in the public archive is from Feb 24, 2008.
How active is r/space?
Very active: r/space gets about 26 new posts a day (average of the last four weeks). Over its lifetime the archive counts 498,760 posts and 10,043,978 comments. In a sample of 189 recent posts we counted 142 different authors.
When is r/space most active?
Based on post counts from Oct 21, 2026 to Oct 27, 2026, the busiest day was Sunday and the quietest Monday, and most posts arrive around 12:00 UTC, with the fewest around 00:00 UTC. More posts also means more competition, so a quieter hour can help a post get noticed.
What is r/space about?
The community describes itself as: “Share & discuss informative content on: * Astrophysics * Cosmology * Space Exploration * Planetary Science * Astrobiology” Recent post titles often mention moon, nasa, solar, universe and satellite. Most posts are links (34%).
Is r/space safe for work?
Yes. Reddit does not mark r/space as an 18+ (NSFW) community. SubMouse lists safe-for-work subreddits only.
How do I post on r/space?
Join the community on Reddit first, then use “Create post”. r/space accepts both text and link posts, with images and galleries enabled. It has 14 posted rules, starting with: “Submissions must be related to Space/Cosmology”; “No sensationalist/misleading/unscientific content or titles”; “No spam/blogspam/paywalled/pirated content”. Moderators remove posts that break the rules, so read them in the sidebar before posting.
Which communities are like r/space?
Communities with similar topics include r/news (31.6M), r/nasa (5.9M), r/cats (9.5M), r/beginnerfitness (3M) and r/InternetIsBeautiful (16.6M).
Stats from public data (data updated Oct 29, 2026; activity, rules and archive totals via the Arctic Shift archive, Oct 29, 2026; top posts from Reddit’s public feeds). Point and comment counts are archive snapshots and can be lower than on Reddit today. SubMouse is an independent directory and is not affiliated with Reddit or the moderators of r/space.