Comet C/2022 E3 (ZTF) was discovered on March 2, 2022 using the 1.2-meter Samuel Oschin robotic telescope, part of the Zwicky Transient Facility (ZTF), located at Mt. Palomar in southern California. Since it was the 3rd one discovered in the fifth half-month E (i.e. A, B, C, D, E) of the year, it is named 2022 E3 ZTF. The inbound trajectory from the Oort cloud to the Sun of this long period comet is 50,000 years. However, the outbound trajectory suggests at best it will not be back for millions of years, or it may be ejected totally ejected from the solar system, never to return—time will tell…

The green color is due to diatomic carbon (C2) produced by the photolysis of organic molecules that evaporate from the nucleus (note, watch for the error, it is not due to CN which actually emits in the violet). The Sun’s UV radiation excites C2 which then emits green light with its peak at 518 nm. The excited organic molecules however are not stable in the UV radiation and thus they degrade within a few days. For this reason, the green emission is always close to the nucleus, it does not survive long enough to get out into  the tail. 

This animation was taken on the evening of January 31st, when the comet was 172.84 million km from the Sun and 42.63 million km from the Earth, about 12 hours before closest approach to Earth, around 42.4 million km. While the comet was near the closest approach the tails have faded considerably, perhaps it is running out of gas? 

The animation is 38 frames of 30 seconds each, with a separation of about 3 to 4 minutes between frames--I missed some time points as the comet was moving so fast across the field. So total time for the video is 2 hours. Note that the animation was taken using an L-eNhance HO filter, as my Bortle 8 light pollution is especially bad lower to the north, with a street light and a brightly lit neighbor, so white light images were totally washed out. Fortunately, the OIII bandpass of this filter covers the major Swan band for C2 green emission peaking at 518 nm, so captures most of the lovely green color. There also is some red glow from dust visible in the Halpha from the red channel. The sky conditions were poor with some haze to the north off the lake, the only “clear” night after two weeks of heavy cloud. BUT, at least I managed to capture it in the end!