C/2018 Y1 (Iwamoto)

For the 2013 and 2020 comets of the same name, see C/2013 E2 (Iwamoto) and C/2020 A2 (Iwamoto).

C/2018 Y1 (Iwamoto) is a long period comet with a retrograde orbit discovered on 18 December 2018, by Japanese amateur astronomer Masayuki Iwamoto.^[1] Its period is estimated to be 1,733 years. It passed closest to Earth on 13 February 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 Iwamoto photographed by Brandon Ghany on 26 February 2019
Discovery[1]
Discovered by	Masayuki Iwamoto
Discovery date	18 December 2018
Orbital characteristics[2]
Epoch	3 March 2019 (JD 2458545.5)
Observation arc	348 days
Number of observations	2,771
Aphelion	287.25 AU
Perihelion	1.287 AU
Semi-major axis	144.27 AU
Eccentricity	0.9911
Orbital period	1,733 years
Inclination	160.40°
Longitude of ascending node	147.48°
Argument of periapsis	358.06°
Last perihelion	7 February 2019
TJupiter	–1.286
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]

Gallery

• 
  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
• 
  C/2018 Y1 (Iwamoto) as seen from the infrared telescope NEOWISE on 25 February 2019

See also

• C/2018 V1 (Machholz–Fujikawa–Iwamoto)