 Comet C/2021 T4 (Lemmon) photographed by theZwicky Transient Facility on 21 December 2022 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | E. Bryssinck |
| Discovery site | Mount Lemmon Survey |
| Discovery date | 7 October 2021 |
| Designations | |
| CK21T040, C6131F2 | |
| Orbital characteristics[4] | |
| Epoch | 14 April 2023 (JD 2460048.5) |
| Observation arc | 3.63 years |
| Earliestprecovery date | 7 August 2021 |
| Number of observations | 2,107 |
| Aphelion | ≈44,000 AU (inbound)[3] ≈2,200 AU (outbound) |
| Perihelion | 1.483 AU |
| Semi-major axis | ~18,130 AU |
| Eccentricity | 0.99992 |
| Orbital period | millions of years (inbound)[3] ≈36,000 years (outbound) |
| Inclination | 160.78° |
| 257.88° | |
| Argument of periapsis | 329.81° |
| Mean anomaly | 359.99° |
| Last perihelion | 31 July 2023 |
| TJupiter | –1.426 |
| EarthMOID | 0.498 AU |
| JupiterMOID | 0.869 AU |
| Physical characteristics | |
| Comet total magnitude (M1) | 12.4 |
| 8.0 (2023 apparition) | |
C/2021 T4 (Lemmon) is anon-periodic comet discovered by theMount Lemmon Survey on 7 October 2021.[2] This passage through the planetary region of theSolar System will reduce the orbital period from millions of years to thousands of years.[3]
It has been south of thecelestial equator since October 2022. On 13 June, it was 1.5 degrees from the starBeta Ceti. Closest approach to Earth was on 20 July 2023 at a distance of 0.54 AU (81 million km).[5] The next day it reached its southernmost declination, at -56 degrees. On 25 July, it passed next to the globular clusterNGC 6397.[6] It reachedperihelion on 31 July 2023 at a distance of 1.48 AU (221 million km). The comet brightened to aroundapparent magnitude 8 at its peak.[7]
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