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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 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°)fρ (0.8 μm) in a 6500 km radius from the nucleus of 1483 ± 40 cm, and CN, C3, and C2 production of 5.43 ± 0.11 × 1025, 2.01 ± 0.04 × 1024, and 3.08 ± 0.5 × 1025 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.

 

Context. The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ≲ 21 mag. Aims. We showcase stellar variability in the Galactic colour-absolute magnitude diagram (CaMD). We focus on pulsating, eruptive, and cataclysmic variables, as well as on stars that exhibit variability that is due to rotation and eclipses. Methods. We describe the locations of variable star classes, variable object fractions, and typical variability amplitudes throughout the CaMD and show how variability-related changes in colour and brightness induce “motions”. To do this, we use 22 months of calibrated photometric, spectro-photometric, and astrometric Gaia data of stars with a significant parallax. To ensure that a large variety of variable star classes populate the CaMD, we crossmatched Gaia sources with known variable stars. We also used the statistics and variability detection modules of the Gaia variability pipeline. Corrections for interstellar extinction are not implemented in this article. Results. Gaia enables the first investigation of Galactic variable star populations in the CaMD on a similar, if not larger, scale as was previously done in the Magellanic Clouds. Although the observed colours are not corrected for reddening, distinct regions are visible in which variable stars occur. We determine variable star fractions to within the current detection thresholds of Gaia . Finally, we report the most complete description of variability-induced motion within the CaMD to date. Conclusions. Gaia enables novel insights into variability phenomena for an unprecedented number of stars, which will benefit the understanding of stellar astrophysics. The CaMD of Galactic variable stars provides crucial information on physical origins of variability in a way that has previously only been accessible for Galactic star clusters or external galaxies. Future Gaia data releases will enable significant improvements over this preview by providing longer time series, more accurate astrometry, and additional data types (time series BP and RP spectra, RVS spectra, and radial velocities), all for much larger samples of stars.