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

Abstract

Long-period comets are planetesimal remnants constraining the environment and volatiles of the protoplanetary disc. We report the discovery of hyperbolic long-period comet C/2022 E3 (ZTF), which has a perihelion $\sim$1.11 au, an eccentricity $\gtrsim$1 and an inclination $\sim$109${}^{\circ }$, from images taken with the Palomar 48-inch telescope during morning twilight on 2022 Mar 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 $\sim$0.28 au of the Earth and reached a visible magnitude of $\sim$5. We measure g-r = 0.70$\pm$0.01, r-i = 0.20$\pm$0.01, i-z = 0.06$\pm$0.01, z-J = 0.90$\pm$0.01, J-H = 0.38$\pm$0.01 and H-K = 0.15$\pm$0.01 colours for the comet from observations. We measure the A(0${}^{\circ }$)f$\ddot{I}$ (0.8~$\hat{I}¼$m) in a 6500~km radius from the nucleus of 1483$\pm$40~cm, and CN, C${}_3$, and C${}_2$ production of 5.43$\pm 0.11\times$10${}^{25}$~mol/s, 2.01$\pm 0.04\times$10${}^{24}$, and 3.08$\pm 0.5\times$10${}^{25}$~mol/s, similar to other long period comets. We additionally observe the appearance of jet-like structures at a scale of $\sim$4,000 km in wide-field g-band images, which may be caused by the presence of CN gas in the near-nucleus coma.

Accepted for publication in MNRAS:L, 9 pages, 6 figures, 2 tables