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C/2021 T4 (Lemmon)

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For other comets discovered by the Mount Lemmon Survey, see Comet Lemmon.
C/2021 T4 (Lemmon)
The comet on 21 December 2022, by ZTF
Discovery[1]
Discovered byE. Bryssinck
Discovery siteMount Lemmon Observatory
Discovery date7 October 2021
Designations
CK21T040
C6131F2
Orbital characteristics[3]
Observation arc2.91 years (1,064 days)
Number of
observations		2,107
Aphelion≈44,000 AU (inbound)[2]
≈2,200 AU (outbound)
Perihelion1.4833 AU
Semi-major axis48,585.76 AU
Eccentricity0.99997
Orbital periodmillions of years (inbound)[2]
≈36,000 years (outbound)
Inclination160.78°
257.88°
Argument of
periapsis		329.81°
Last perihelion31 July 2023
Earth MOID0.4975 AU (74.42×10^6 km)
Jupiter MOID0.8699 AU (130.14×10^6 km)
Comet total
magnitude (M1)		6.9

C/2021 T4 (Lemmon) is a long period comet discovered by the Mount Lemmon Observatory on 7 October 2021.[1] This passage through the planetary region of the Solar System will reduce the orbital period from millions of years to thousands of years.[2]

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).[4] The next day it reached its southernmost declination, at -56 degrees. On 25 July it passed next to the globular cluster NGC 6397.[5] It reached perihelion on 31 July 2023 at a solar distance of 1.48 AU. The comet brightened to around apparent magnitude 8.[6]

References

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  1. ^ a b "MPEC 2021-U187: COMET C/2021 T4 (Lemmon)". minorplanetcenter.net. Retrieved 2021-10-30.
  2. ^ 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
  3. ^ "C/2021 T4 (Lemmon) – JPL Small-Body Database Browser". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 29 October 2024.
  4. ^ Earth Approach 2023 (delta. Close approach occurs when deldot flips from negative to positive.)
  5. ^ Dickinson, David (25 July 2023). "A Fine Southern Apparition for Comet T4 Lemmon". Universe Today. Retrieved 29 July 2023.
  6. ^ C/2021 T4 ( Lemmon ) mag chart by Seiichi Yoshida
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