Sure. The SETI account is mastodon.social/@setiinstitute

This looks like it might have been the NASA account, but I can’t verify whether it was official: mstdn.social/@NASA (The unofficial one that is active and more popular is social.beachcom.org/@nasa)

Some people working in space, e.g. astronomers and astrophysicists. There are many more, these are just some examples

• scicomm.xyz/@KellyLepo
• mastodon.social/@sundogplanets
• mastodon.social/@markmccaughrean
• mastodon.social/@AstroHyde
• mastodon.online/@elizabethtasker
• mastodon.social/@mcnees
• mastodon.social/@badastro
• mastodon.online/@michael_w_busch
• mastodon.online/@astro_jcm
• mastodon.social/@pomarede
• tech.lgbt/@planetarypan
• scicomm.xyz/@JohnBarentine
• scicomm.xyz/@drcaro
• mastodon.social/@planet4589

These people appear to be current or former nasa employees:

• masto.ai/@astroptere
• xoxo.zone/@arielwaldman
• mastodon.online/@Physicsj
• deepspace.social/@kevinmgill
• mastodon.online/@astrobiolena
• mapstodon.space/@mapperwocky

And here are some other space-related organisations:

• scicomm.xyz/@sjastronomy
• social.numerique.gouv.fr/@irap
• fediscience.org/@OJ_Astro
• mastodon.social/@ec_euclid
• mastodon.social/@esoastronomy
• vmst.io/@WestportObservatory
• mastodon.online/@StellaLunaObs
• observatory.social/@BGO

This is just what I found looking around, I think it shows there’s a strong space community on the fediverse.