Palomar discovery and initial characterization of naked-eye long-period comet C/2022 E3 (ZTF)

Long-period comets are planetesimal remnants constraining the environment and volatiles of the protoplanetary disc. We report the disco v ery of hyperbolic long-period comet C/2022 E3 Zwicky Transient Facility (ZTF), which has a perihelion ∼1.11 au, an eccentricity ≳1 and an inclination ∼109 °, from images taken with the Palomar 48-inch telescope during morning twilight on 2022 March 2. Additionally, we report the characterization of C/2022 E3 (ZTF) from observations taken with the Palomar 200-inch, the Palomar 60-inch, and the NASA Infrared Telescope Facility in early 2023 February to 2023 March when the comet passed within ∼0.28 au of the Earth and reached a visible magnitude of ∼5. We measure g -r = 0.70 ±0.01, r -i = 0.20 ±0.01, i -z = 0.06 ±0.01, z -J = 0.90 ±0.01, J -H = 0.38 ±0.01, and H -K = 0.15 ±0.01 colours for the comet from observations. We measure the A(0 °)f ρ(0.8 μm) in a 6500 km radius from the nucleus of 1483 ±40 cm, and CN, C 3 , and C 2 production of 5.43 ±0.11 ×10 25 , 2.01 ±0.04 ×10 24 , and 3.08 ±0.5 ×10 25 mol s -1 , similar to other long-period comets. We additionally observe the appearance of jet-like structures at a scale of ∼4000 km in wide-field g -band images, which may be caused by the presence of CN gas in the near-nucleus coma.