C/2021 T4 (Lemmon)

The comet on 21 December 2022, by ZTF
Discovery
Discovery date	7 October 2021
Designations
Alternative 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°
Longitude of ascending node	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

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