Dr. Jonathan McDowell is an astrophysicist at the Smithsonian Astrophysical Observatory, part of the Center for Astrophysics (Harvard and Smithsonian) in Cambridge, MA. A staff member of the Chandra X-ray Center (CXC), he studies black holes, quasars and X-ray sources in galaxies, as well as developing data analysis software for the X-ray astronomy community as part of the Chandra X-ray Observatory team. As well as studying distant quasars, McDowell is known for work on the history of space exploration, and maintains the most comprehensive list of satellite and space launches. McDowell's online newsletter on space launches, Jonathan's Space Report (since 1989) gives details of all satellite launches, and the associated web site, https://planet4589.org, contains tables of rocket launches and space activities. In 2018 Dr. McDowell published a paper giving physical arguments that the lower boundary of outer space should be at 80 km above the Earth, and not the currently-popular value of 100 km. Main belt asteroid (4589) McDowell is named after him.