C/2021 T4 (Lemmon) is a non-periodic comet discovered by the Mount Lemmon Survey on 7 October 2021. Its current passage through the planetary region of the Solar System will reduce the orbital period from millions of years to thousands of years.
It has been south of the celestial equator since October 2022. On 13 June, it was 1.5 degrees from the star Beta Ceti. Closest approach to Earth was on 20 July 2023 at a distance of .Earth Approach 2023 (delta. Close approach occurs when deldot flips from negative to positive.) The next day it reached its southernmost declination, at -56 degrees. On 25 July, it passed next to the globular cluster NGC 6397. It reached perihelion on 31 July 2023 at a distance of . The comet brightened to around apparent magnitude 8 at its peak.C/2021 T4 ( Lemmon ) mag chart by Seiichi Yoshida
References
External links
C/2021 T4 at Seiichi Yoshida's website