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C/2021 T4 (Lemmon) 
Summary
C/2021 T4 (Lemmon) is an inbound long period comet discovered by the Mount Lemmon Observatory on 7 October 2021.[2] This passage through the planetary region of the Solar System will reduce the orbital period from millions of years to thousands of years.[1]
 The comet on 21 December 2022, by ZTF | |
| Discovery | |
|---|---|
| Discovery date | 7 October 2021 |
| Designations | |
| CK21T040, C6131F2 | |
| Orbital characteristics | |
| Observation arc | 1.7 years |
| Aphelion | ≈44,000 AU (inbound)[1] ≈2,200 AU (outbound) |
| Perihelion | 1.4823 AU |
| Eccentricity | 0.99970 |
| Orbital period | millions of years (inbound)[1] ≈36,000 years (outbound) |
| Inclination | 160.76° |
| 257.79° | |
| Argument of periapsis | 329.78° |
| Next perihelion | 31 July 2023 |
| Earth MOID | 0.497 AU (74.4 million km) |
| Jupiter MOID | 0.869 AU (130.0 million km) |
| Comet total magnitude (M1) | 6.9 |
It has been south of the celestial equator since October 2022. On 13 June it was 1.5 degrees from magnitude 2 Beta Ceti. Closest approach to Earth was on 20 July 2023 at a distance of 0.54 AU (81 million km).[3] The next day it reached its southernmost declination, at -56 degrees. On 25 July it passed next to the globular cluster NGC 6397.[4] It reached perihelion on 31 July 2023 at a solar distance of 1.48 AU. The comet brightened to around apparent magnitude 8.[5]
References edit
- ^ a b c Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2021 T4 (Lemmon)". Retrieved 2023-04-26. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0) Epoch 1800 has PR= 1E+9 / 365.25 days = millions of years
- ^ "MPEC 2021-U187 : COMET C/2021 T4 (Lemmon)". minorplanetcenter.net. Retrieved 2021-10-30.
- ^ Earth Approach 2023 (delta. Close approach occurs when deldot flips from negative to positive.)
- ^ Dickinson, David (25 July 2023). "A Fine Southern Apparition for Comet T4 Lemmon". Universe Today. Retrieved 29 July 2023.
- ^ C/2021 T4 ( Lemmon ) mag chart by Seiichi Yoshida