planet4589.org is the website of Jonathan McDowell, an astrophysicist, space sustainability analyst, and historian of astronautics. McDowell worked at the Harvard-Smithsonian Center for Astrophysics from 1988 to 2026 and with the Chandra X-Ray Center from 1994 to 2026. He is now retired and an honorary professor at Durham University.
The site provides extensive data on the history of space exploration, including a general catalog of artificial space objects. This catalog includes data on space organizations, orbital launch logs, satellite lists, and more. McDowell also publishes Jonathan's Space Report (JSR), a monthly newsletter detailing space launches and piloted missions. The website also features statistical figures, space activities analyses, and a catalog of space debris clouds. McDowell is also active on social media, using platforms such as Twitter (@planet4589) and Bluesky (@planet4589.bsky.social). His work is widely referenced in the space industry. In May 2024, his expertise was featured in the "Smarter Every Day 298" YouTube video, where he helped analyze a mysterious object photographed during a solar eclipse.
