460P/PanSTARRS

Lore & Background

The object was discovered on 22 January 2016 by a Pan-STARRS telescope and initially thought to be an asteroid, given the provisional minor planet designation 2016 BA14. Astronomer Denis Denisenko noted its orbit was very similar to 252P/LINEAR, prompting follow-up observations by the Lowell Discovery Telescope, which revealed a tail and identified it as a probable comet, renamed P/2016 BA14. It was also observed by the 4.3 meter aperture Discovery Channel Telescope in Arizona.

The comet made a close flyby to Earth on 22 March 2016 at a distance of 2.2 million mi (3.5 million km; 9.2 LD), the closest approach by a comet since 1770 and the third closest recorded. This flyby enabled radar observations by the Goldstone Solar System Radar, which revealed a rotation rate of 35–40 hours and surface features as small as 8 m, marking the highest resolution radar image of a comet. The nucleus was much larger than expected—about 1 km in diameter, compared to an earlier estimate of 125 meters—due to its very low albedo. The comet was recovered by R. Weryk on 17 October 2020 using the Pan-STARRS 1.8 m telescope, with an apparent magnitude of 22.6.

Reader's Guide

460P/PanSTARRS is significant primarily for its historic close approach to Earth in March 2016, which provided a rare opportunity for detailed study. The flyby allowed radar imaging at the highest resolution ever achieved for a comet, revealing surface features as small as 8 meters. The comet's nucleus was found to be about 1 km in diameter, much larger than initial predictions, and its surface reflects only 2-3 percent of light, similar to charcoal. Observations by NASA's Infrared Telescope Facility and the Subaru Telescope confirmed its low albedo and suggested a composition of phyllosilicate and organic materials, with a diameter of 800 m from mid-infrared data. The comet's orbit is very similar to that of 252P/LINEAR, and it may have split off from that comet. During the 2016 flyby, 252P/LINEAR was much more active, by three to four orders of magnitude, despite having a smaller nucleus. The comet's future orbital evolution includes a close approach to Jupiter in 2034 and 2042, altering its perihelion and period, and a next Earth flyby on 14 March 2048 at 0.052 AU. It was listed as a backup target for the European Space Agency's Comet Interceptor mission, with a potential flyby on 20 April 2037.

Did You Know?

• 460P/PanSTARRS made the closest approach to Earth by any comet since 1770, when Lexell's Comet passed within 1.4 million miles.
• The comet's nucleus reflects only 2-3 percent of visible light, about the same as a charcoal briquette.
• Radar observations during the 2016 flyby achieved the highest resolution radar image of a comet, detecting surface features as small as 8 meters.
• The comet may have split off from comet 252P/LINEAR, as their orbits are very similar.