J
- JAC – (publication) Japan Astronomical Circular
- JAC – (organization) Joint Astronomy Centre, the organization that operates the United Kingdom Infrared Telescope and the James Clerk Maxwell Telescope
- JAPOA – (organization) Japan Amateur Photoelectric Observers Association
- JAXA – (organization) Japan Aerospace eXploration Agency
- JCMT – (telescope) James Clerk Maxwell Telescope
- JD – (astrophysics terminology) Julian Date, an alternative time commonly used in astronomy
- JET-X – (telescope) Joint European Telescope for X-ray astronomy
- JGR – (publication) Journal of Geophysical Research
- JILA – (organization) formerly Joint Institute for Laboratory Astrophysics
- JKT – (telescope) Jacobus Kapteyn Telescope
- JPL – (organization) Jet Propulsion Laboratory, a research center associated with NASA
- JSGA – (telescope/organization) Japan SpaceGuard Association, a Japanese telescope used to track near-Earth asteroids and space junk
- JWST – (telescope) James Webb Space Telescope, a planned space telescope that will supersede the Hubble Space Telescope
Read more about this topic: List Of Astronomy Acronyms