C/2017 K2 (PanSTARRS), sometimes called the K2 “megacomet,” came closest to Earth on Thursday, July 14, at a distance of about 168 million miles. The Canada–France–Hawaii Telescope (CFHT) suggested K2’s nucleus could be between 18 and 100 miles (30 to 160 km) wide, but data from the Hubble Space Telescope showed it might be only 11 miles (18 km) wide.
During its close approach to Earth, the comet was at peak brightness. Perfect timing for a conjunction with a star cluster.
The comet seems to be launching a jet of material in the direction of the cluster’s center. Actually, no. Just one of the comet’s two tails is visible there. An ion tail and a dust tail are present in all comets. The solar wind blows the gaseous ion tail directly away from the sun. The comet’s orbit is more precisely traced by the heavier dust tail. The ion tail is what is pointing toward the star cluster.
As mentioned in Spaceweather.com, “Using a telescope in Namibia, Gerald Rhemann photographed the big comet passing by M10 on July 15th.”
The comet seems to have originated in the Oort cloud. Unlike other comets that appear repeatedly, this was the K2 comet’s first trip to our inner solar system. It was first spotted by the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) in the solar system’s outer reaches in 2017.