 Comet Erasmus photographed from theZwicky Transient Facility on 14 November 2020 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | Nicolas Erasmus |
| Discovery site | ATLAS–MLO (T08) |
| Discovery date | 17 September 2020 |
| Designations | |
| CK20S030[2] | |
| Orbital characteristics[3] | |
| Epoch | 11 March 2021 (JD 2459284.5) |
| Observation arc | 436 days (1.19 years) |
| Number of observations | 861 |
| Aphelion | 389.268 AU |
| Perihelion | 0.3985 AU |
| Semi-major axis | 194.833 AU |
| Eccentricity | 0.99795 |
| Orbital period | ~2,720 years |
| Inclination | 19.861° |
| 222.993° | |
| Argument of periapsis | 349.886° |
| Mean anomaly | 0.032° |
| Last perihelion | 12 December 2020 |
| TJupiter | 0.762 |
| EarthMOID | 0.315 AU |
| JupiterMOID | 0.584 AU |
| Physical characteristics[5] | |
| Dimensions | 1.6–2.4 km (0.99–1.49 mi) |
Mean diameter | 2.0 km (1.2 mi) |
| Comet total magnitude (M1) | 13.0 |
| Comet nuclear magnitude (M2) | 14.8 |
| 3.9 (2020 apparition)[4] | |
Comet Erasmus, formally designated asC/2020 S3, is anon-periodic comet which passed perihelion on 12 December 2020. Its maximum brightness peaked around anapparent magnitude of 4, however its proximity to theSun at that time made it a difficult object to view from the ground.[6]
The comet was discovered as an 18.5-magnitude object from four 30-second exposure images taken on 17 September 2020 from theATLAS–MLO observatory inMauna Loa, Hawaii.[7] It was initially flagged as a potentialnear-Earth asteroid until Dr.Nicolas Erasmus analyzed the images and noticed a faintcoma around it shortly before announcing the discovery.[7]
It was visible in predawn skies as it made its closest approach toEarth at a distance of 1.09 AU (163 million km) on 19 November 2020.[8] Around this time, the comet was located within the constellationHydra.[9]
It was predicted to reach a maximum brightness of magnitude 3.0–4.0 during its perihelion on 12 December 2020 at a distance of 0.4 AU (60 million km) from theSun. However, the comet's position throughout December was too close to the Sun for ground observations, making it impossible to view at its brightest except fromSOHO andSTEREO-A.[6][10]
Several observers were able to capture it during thetotal solar eclipse on 14 December 2020.[11]
The comet'slinear polarization was measured between 13 and 23 November 2020, where astronomers have noted a similar performance as those seen fromC/1989 X1 (Austin) andC/1996 B2 (Hyakutake), with models suggesting a decrease in the abundance ofMg–rich silicate particles in the inner coma by 1/3, revealing a change in the emanations of dust particles from the comet'snucleus.[12] Chemical analysis of the comet showed that its coma is enriched informaldehyde (H2CO),ammonia (NH3), andacetylene (C2H2) compounds, however it is noticeably depleted of anymethanol (CH3OH).[13]
During perihelion in December 2020, the comet's tail had exhibited wagging behaviour due to its interaction with acoronal mass ejection from the Sun.[6] Its water production rate reached a maximum of 3.5×1029 sec-1 around this time.[14] By the time it reached 1.45 AU (217 million km) on its outbound journey, its water production rate was still seven times higher than previously observed before perihelion, which was estimated to be around 1×1028 sec-1.[14]
The nucleus is estimated to be around 1.6–2.4 km (0.99–1.49 mi) in diameter.[5]
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