C/2021 T4 (Lemmon)
The comet on 21 December 2022, by ZTF
Discovery
Discovery date7 October 2021
Designations
CK21T040, C6131F2
Orbital characteristics
Observation arc1.7 years
Aphelion≈44,000 AU (inbound)[1]
≈2,200 AU (outbound)
Perihelion1.4823 AU
Eccentricity0.99970
Orbital periodmillions of years (inbound)[1]
≈36,000 years (outbound)
Inclination160.76°
257.79°
Argument of
periapsis		329.78°
Next perihelion31 July 2023
Earth MOID0.497 AU (74.4 million km)
Jupiter MOID0.869 AU (130.0 million km)
Comet total
magnitude (M1)		6.9

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]

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

  1. ^ 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
  2. ^ "MPEC 2021-U187 : COMET C/2021 T4 (Lemmon)". minorplanetcenter.net. Retrieved 2021-10-30.
  3. ^ Earth Approach 2023 (delta. Close approach occurs when deldot flips from negative to positive.)
  4. ^ Dickinson, David (25 July 2023). "A Fine Southern Apparition for Comet T4 Lemmon". Universe Today. Retrieved 29 July 2023.
  5. ^ C/2021 T4 ( Lemmon ) mag chart by Seiichi Yoshida
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