C/2018 Y1 (Iwamoto)

C/2018 Y1 (Iwamoto) is a long period comet with a retrograde orbit discovered on December 18, 2018, by Japanese amateur astronomer Masayuki Iwamoto.^[1] Its period is estimated to be 1,733 years. It passed closest to Earth on February 13, 2019.^[3] It was expected to reach a magnitude of between 6.5 and 7.5, visible in binoculars or a small telescope^[3]^[4] and was reported to reach a magnitude of 5.5 by Juan Jose Gonzalez on February 13, before fading to 7.6 two weeks later.^[5]

C/2018 Y1 (Iwamoto)
Comet C/2018 Y1 (February 25, 2019) from the infrared telescope NEOWISE
Discovery^[1]
Discovered by	Masayuki Iwamoto
Discovery date	December 18, 2018
Orbital characteristics^[2]
Epoch	19 July 2022
Observation arc	348 days
Aphelion	287 AU
Perihelion	1.287 AU
Semi-major axis	144 AU
Eccentricity	0.9911
Orbital period	1733 years
Inclination	160.4°
Longitude of ascending node	147.5°
Last perihelion	7 February 2019
Earth MOID	0.299 AU (44.7 million km)
Jupiter MOID	1.507 AU (225.4 million km)
Comet total magnitude (M1)	13.6

The comet was observed by iSHELL spectrograph at the NASA Infrared Telescope Facility (IRTF). Overall, the measured spatial distributions for polar molecules (in particular, H₂O and CH₃OH) were broader, exhibiting more complex structure compared with nonpolar or weakly polar species (CH₄, C₂H₆, and CO). Compositionally, compared to their respective mean abundances among comets from the Oort cloud, C₂H₆ and CH₃OH were enriched, CH₄ and HCN were near normal, and all other species were depleted. The abundance ratio CH₃OH/C₂H₆ was higher by 45% ± 8% on January 13 versus February 5, whereas CH₄/C₂H₆ was unchanged within the uncertainty, suggesting nonhomogeneous composition among regions of the nucleus dominating activity on these dates.^[6]

Animation of C/2018 Y1 orbit
Mercury · Venus · Earth · Mars · C/2018 Y1
Animation of C/2018 Y1 orbit 1600-2500
Sun · Uranus · C/2018 Y1
Comet C/2018 Y1 (Iwamoto) with M44, 13. February 2019, 23:04 Uhr
Comet C/2018 Y1 (Iwamoto) with the spiral galaxy NGC 2903, 13 February 2019, 23:19 Uhr
Comet C/2018 Y1 (Iwamoto) with nebulae IC 410 and IC 405

^ ^a ^b James, Nick. "C/2018 Y1 (Iwamoto) - A new comet for the new year". Britastro.org. Retrieved 2 February 2019.

^ "JPL Small-Body Database Browser: C/2018 Y1". JPL. Retrieved 15 October 2022.

^ ^a ^b "Speedy comet approaching Earth's vicinity". Earth & Sky. Retrieved 2 February 2019.

^ Hanneke Weitering (12 February 2019). "How to See Comet Iwamoto Fly Past Earth This Week". Space.com. Retrieved 15 October 2022.

^ "Weekly Information about Bright Comets (2019 Mar. 2: North)". www.aerith.net. Retrieved 15 October 2022.

^ DiSanti, Michael A.; Bonev, Boncho P.; Dello Russo, Neil; McKay, Adam J.; Roth, Nathan X.; Saki, Mohammad; Gibb, Erika L.; Vervack Jr., Ronald J.; Khan, Younas; Kawakita, Hideyo (9 November 2021). "Volatile Composition and Outgassing in C/2018 Y1 (Iwamoto): Extending Limits for High-resolution Infrared Cometary Spectroscopy between 2.8 and 5.0 μm" (PDF). The Planetary Science Journal. 2 (6): 225. Bibcode:2021PSJ.....2..225D. doi:10.3847/psj/ac07ae. ISSN 2632-3338. S2CID 229008642.

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C/2018 Y1 (Iwamoto)

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