15/07/2022 09:36-10:28 UT
Total exposure time:
iTelescope - T9, Siding Spring Observatory, Australia
FLI ProLine 16803
Tele Vue NP127fli 127/680 mm
10Micron 2000 HPS
Focal ratio, length:
f/5.3, 680 mm
9 x 120 s Lum, 3 x 120 s R/G/B
Astro Pixel Processor, PixInsight, Adobe Lightroom, Adobe Photoshop
After the comets C/2020 F3 (NEOWISE) in 2020 and C/2021 A1 (Leonard) in 2021, 2022 will be another interesting one, but not as spectacular as the previous two comets.
C/2017 K2 (PANSTARRS) was discovered on 21 May 2017 by Richard Wainscoat and colleagues using the 1.8-metre telescope of the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) sky survey programme from the Maui Island in the Hawaiian Islands. From the first images, it was obvious that it was moving relatively slowly, so it was concluded that a distant object had been detected. Calculations soon showed that the hypothesis was correct, with the comet discovered at a distance of 2.4 billion kilometres from the Sun. And further calculations revealed that C/2017 K2 (PANSTARRS) probably came to us from a distance of 0.8 light years, from the Oort cloud. What makes this comet special is that comets are very rarely active at this distance from the Sun. This may also mean that it is probably the first time it has approached the Sun, as the gases, which are volatile even at low temperatures, would have already left the surface of the nucleus on a previous solar approach. Researchers were able to identify the celestial wanderer, which is about 14-18 km in diameter (a pretty big comet), by July 2013, after reviewing archival images.
Following its discovery, its brightness and apparent diameter have increased steadily and predictably. These suggested that a "fresh" comet of 6-7 magnitude brightness would be seen in the summer of 2022. Taking advantage of its approach, on 3 May 2021, I took my first photo of the "dirty snowball", then 920 million kilometres from Earth. The then 13.1 magnitude "resurgent" C/2017 K2 (PANSTARRS) did not hold many surprises, but at the time there was no sign that the previously stable comet would fall slightly short of expectations.
In the spring of 2022, the light curve already showed some signs of a break and by early summer it became clear that we could expect the comet to reach 7.5-8 magnitude during its visibility in Hungary. The lack of a long tail and the compact green coma are a distinct disappointment for a comet that has rarely or never been close to the Sun. The comet, which can be observed with binoculars and is heading steeply south, will be visible in the constellation of Ophiuchus and Scorpius in the summer and later exclusively from the southern hemisphere. Although the chances are very slim due to its relatively distant perihelion (1.79 AU), southern observers can still hope for an unexpected outburst.
The Comet C/2017 K2 (PANSTARRS) approached Earth on the 14th of July 2022, and a few hours later apparently passed by the Messier 10 cluster, more than 14 000 light-years away. Capturing this kind of conjunction is never an easy task, especially when you have to bring out the faintest parts of the comet under the full moon.
C/2017 K2 (PANSTARRS)
R.A. 16 h 56 m 20 s Dec. -3° 43′ 25″
Distance from Sun:
396 million km
Distance from Earth:
271 million km
Coma: 5'; tail: 45' (PA: 15°)