From a recent study published on Monthly Notices of the Royal Astronomical Society, people know more about the Comet K2 (C/2017 K2 (PANSTARRS)) from the distant Oort cloud. The physical and active properties of the distant active comet are revealed in the research.

Dr. ZHANG Xiliang from Yunnan Observatories of Chinese Academy of Sciences led the research. They observed the comet with the Lijiang 2.4 m telescope.

Normally, a comet becomes active when it reaches the heliocentric distance of 3 to 5 au because of the effect of solar radiation. The discoveries of distant active comets pose a challenge for the current active mechanism of comet. So far the confirmed farthest heliocentric distance where the activity can be found is 25.8 au for comet C/2010 U3 (Boattini).

Comet K2, a small solar object coming from the Oort cloud, was discovered by the American survey telescope of PANSTARRS on 2017 May 21 at its heliocentric of 16 au and was then confirmed to be active. Dr. ZHANG Xiliang and collaborators began to monitor K2 on 2017 Sept. 8 using the Lijiang 2.4 m telescope.

Their results found that the activity of K2 during 2017 Sept. 8 and 2018 June 18 was mainly supported by the big particles of CO and CO2, the activity status of K2 was generally stable with short-term fluctuations. Meanwhile the nuclei size of K2 was also restricted.

The active properties of K2 will provide important information for studying the active mechanism of distant comets.

Contact:

ZHANG Xiliang

Yunnan Observatories

zhangxiliang@ynao.ac.cn