A Periodic Visitor at Kitt Peak

The night sky above the WIYN 3.5-meter telescope at the U.S. National Science Foundation Kitt Peak National Observatory, a Program of NSF NOIRLab, is adorned with Jupiter (center right) and the Pleiades (upper right) in this Image of the Week. But the most impressive of all the adornments is Comet Pons-Brooks on the bottom right side of this image. This comet, with a nucleus about 30 kilometers (19 miles) in diameter, follows a 71-year orbit around the Sun. It was first recorded in 1812 by Jean-Louis Pons, and was then ‘discovered’ on its next passage near Earth by William Robert Brooks — hence the name Pons-Brooks.

Comets orbit the Sun in elongated elliptical orbits. These relatively small, icy bodies are dark against the blackness of space so when they travel into the farthest parts of the Solar System they become invisible to us on Earth. Astronomers recover — or, in other words, relocate — a comet when it’s observed upon its return to the inner Solar System and they have rematched the comet’s trajectory to earlier observations.

Most recently, Comet Pons-Brooks was recovered on 20 June 2020 by the Lowell Discovery Telescope when it was 11.9 AU from the Sun, just beyond the orbit of Saturn. Pons-Brooks most recently made its closest pass to the Sun on 21 April 2024 and is now returning to the cold darkness of the outer Solar System.

Rob Sparks, the photographer, is a NOIRLab Audiovisual Ambassador.