C/2011 KP36 (Spacewatch)

Lore & Background

C/2011 KP36 (Spacewatch) was initially thought to be an asteroid-like object with a very eccentric orbit at the time of its discovery on 21 May 2011. A series of stacked images obtained from observations taken between April and May 2012 showed signs of diffuse cometary activity, with a coma about 6 arcseconds in diameter and a faint tail about 9 arcseconds in length. Observations in July 2015 from the Leoncito Astronomical Complex (CASLEO) in Argentina showed that the comet had a dust mass-loss rate of about 282.86 kg/s (623.6 lb/s) in average.

Orbital calculations of the comet showed that it has a very eccentric orbit whose perihelion is around 4.88 AU (730 million km) from the Sun and an aphelion of 71.94 AU (10.762 billion km), almost twice that of Neptune. NASA / JPL considers this comet as part of the Jupiter-family of comets, however this is highly unlikely as it takes roughly 238 years to complete one full orbit around the Sun. Some astronomers even consider this comet a scattered disc object, however Dr. Yan R. Fernandez concluded that 2011 KP36 belongs to the 'group of long-period comets that are nearly Halley-type' despite its Tisserand parameter being around 2.64.

Reader's Guide

C/2011 KP36 (Spacewatch) is notable primarily for its enormous nucleus diameter of 55.1 km, placing it among the largest comets ever discovered. Its orbital characteristics are unusual and debated: while NASA/JPL classifies it as a Jupiter-family comet, its 238-year orbital period makes that classification highly unlikely. Some astronomers consider it a scattered disc object, but Dr. Yan R. Fernandez concluded it belongs to the group of long-period comets that are nearly Halley-type, despite a Tisserand parameter of 2.64. The comet's distant orbit, with perihelion at 4.88 AU and aphelion nearly twice that of Neptune, means it remains far from the Sun even at its closest approach. Its cometary activity was confirmed in 2012 through stacked images showing a coma and faint tail, and later observations in 2015 measured a significant dust mass-loss rate. The uncertainty in its classification highlights the challenges in categorizing distant, long-period comets, and its large size makes it a key object for understanding the population of large cometary bodies in the outer solar system.

Did You Know?

• C/2011 KP36 has a nucleus diameter of 55.1 km (34.2 mi), making it one of the largest comets ever discovered.
• Its aphelion of 71.94 AU is almost twice that of Neptune.