Comet 19P/Borrelly was discovered by Alphonse Louis Nicolas Borrelly on Dec. 28, 1904 in Marseilles, France.
Resembling a chicken leg, the nucleus of comet 19P/Borrelly is small and measures approximately 2.98 miles (4.8 kilometers) in diameter. This is about a third of the size of the object hypothesized to have led to the demise of the dinosaurs.
Borrelly orbits the Sun within the asteroid belt and is a member of the Jupiter-family. A Jupiter-family comet is defined as having an orbital period of less than 20 years and one that has been modified by close passages with the gas giant. It takes 6.85 years for this comet to orbit the Sun once. Borrelly last reached perihelion (closest approach to the Sun) in 2015.
Deep Space 1 flew by comet Borrelly on Sept. 22, 2001. Traveling at a speed of 10.25 miles (16.5 kilometers ) per second, Deep Space 1 flew just 1,367 miles (2,200 kilometers) above Borrelly's nucleus. This spacecraft captured the best-resolution pictures of any comet's nucleus at the time.
Deep Space 1, which was launched in 1998, was designed to be an engineering test mission. The technology tested by this mission informed the design of the Dawn spacecraft.
How Comet 19P/Borrelly Got Its Name
Comets are usually named for their discoverer(s) or for the name of the observatory/telescope used in the discovery. Since Alphonse Borrelly discovered this comet it is named for him. The letter "P" indicates that 19P/Borrelly is a "periodic" comet. Periodic comets have an orbital period of less than 200 years.