Discovery and Origin of Comet C/2017 K2 (PANSTARRS)
Comet C/2017 K2 (PANSTARRS) was first spotted on May 21, 2017, using the Pan-STARRS survey instrument in Hawaii. At the time of its discovery, it was the farthest active inbound comet ever observed, located between the orbits of Saturn and Uranus. The comet is believed to originate from the Oort Cloud, a region in the outer reaches of our solar system that is home to many long-period comets.
Orbit and Orbital Characteristics
C/2017 K2 follows a highly elliptical orbit characteristic of long-period comets. At its discovery, it was 1.49 billion miles (2.4 billion km) from the sun, which is 16 times farther away than Earth is from the sun. The comet reached its perihelion, or closest approach to the sun, on December 19, 2022, at a distance of about 1.8 AU (astronomical units) from the sun. Its orbital period is estimated to be in the millions of years, typical for comets originating from the Oort Cloud.
Notable Appearances and Observations
C/2017 K2 (PANSTARRS) made its closest approach to Earth on July 14, 2022, providing excellent opportunities for astrophotographers. The comet developed a large coma, estimated to be about 81,000 miles (130,000 km) in diameter, which is almost as big as Jupiter. It also displayed an impressively long tail, estimated to be about 500,000 miles (800,000 km) long. Despite its size, the comet remained a telescopic object, not visible to the naked eye, with a brightness around magnitude 8 to 9. This made it an ideal target for astrophotographers using telescopes or long-exposure photography techniques.
Scientific Significance and Composition
C/2017 K2 (PANSTARRS) is particularly interesting to scientists due to its early activity at such a great distance from the sun. Typically, comets become active when they get closer to the sun and their ices begin to sublimate. However, K2 was already showing signs of activity when it was first discovered between the orbits of Saturn and Uranus. This suggests that its activity is likely driven by a mix of ices, including more volatile substances like nitrogen, carbon dioxide, carbon monoxide, and molecular oxygen, in addition to water ice. The comet’s large coma and long tail indicate significant outgassing and dust production, providing valuable data for researchers studying the composition and behavior of Oort Cloud comets. For astrophotographers, the comet’s extended period of visibility and its impressive coma and tail offered numerous opportunities to capture detailed images of its evolution as it approached the inner solar system.
