 Comet Iwamoto photographed by Brandon Ghany on 26 February 2019 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | Masayuki Iwamoto |
| Discovery site | Awa, Tokushima, Japan |
| Discovery date | 18 December 2018 |
| Designations | |
| CK18Y010 | |
| Orbital characteristics[3] | |
| 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° |
| 147.48° | |
| Argument of periapsis | 358.06° |
| Last perihelion | 7 February 2019 |
| TJupiter | –1.286 |
| EarthMOID | 0.299 AU |
| JupiterMOID | 1.507 AU |
| Physical characteristics | |
| Comet total magnitude (M1) | 13.6 |
| 5.5[4] (2019 apparition) | |
C/2018 Y1 (Iwamoto) is anon-periodic comet with aretrograde orbit discovered on 18 December 2018, by Japanese amateur astronomerMasayuki Iwamoto.[5] Its orbital period is estimated to be 1,733 years, and it passed closest to Earth on 13 February 2019.[6]
Nearly a month after co-discoveringC/2018 V1 (Machholz–Fujikawa–Iwamoto), Masayuki Iwamoto spotted another comet on 18 December 2018, which was moving north on the constellationHydra.[a]Shuichi Nakano noted that the 13th-magnitude object has a bluecoma, where he also provided initial orbital calculations using Iwamoto's images two days later.[1]
It was expected to reach a magnitude of between 6.5 and 7.5, visible in binoculars or a small telescope.[6][7] On 13 February 2019, Juan Jose Gonzalez reported that it had reached a peak magnitude of 5.5,[4] before fading to 7.6 two weeks later.[8]
The comet was observed by iSHELL spectrograph at the NASAInfrared Telescope Facility (IRTF). Overall, the measured spatial distributions for polar molecules (in particular,H
2O andCH
3OH) were broader, exhibiting more complex structure compared with nonpolar or weakly polar species (CH4,C2H6, andCO). Compositionally, compared to their respective mean abundances among comets from the Oort cloud,C2H6 andCH3OH were enriched,CH4 andHCN were near normal, and all other species were depleted. The abundance ratioCH3OH/C2H6 was higher by45±8% on January 13 versus February 5, whereasCH4/C2H6 was unchanged within the uncertainty, suggesting nonhomogeneous composition among regions of the nucleus dominating activity on these dates.[9]
This article contains quotations from this source, which is available under theCreative Commons Attribution 4.0 Unported (CC BY 4.0) license.
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