C/2025 A6 (Lemmon)
non-periodic comet
C/2025 A6 (Lemmon) is a non-periodic comet discovered by the Mount Lemmon Survey in images obtained on 3 January 2025. It made its closest approach to Earth on 21 October 2025 and was visible to the naked eye.
Observational history
Discovery
C/2025 A6 (Lemmon) was discovered as an asteroidal object with an apparent magnitude of about 21.5 by the Mount Lemmon Survey in images obtained on 3 January 2025 when it was 4.5 AU from the Sun. Consequently, precovery images by PanSTARRS dating from 12 November 2024 were found. The object was found to have a very condensed coma, 2.2 arcseconds across. A short tail, two arcseconds long was found in images from 21 February 2025.
When first discovered the comet was expected to only brighten to apparent magnitude 10, but brightened to apparent magnitude of about 3.5, which would make it about 400 times brighter than original expectations.
Approaching perihelion
After being hidden in the Sun's glare during June and July as it came to solar conjunction on 2 July 2025, the comet was spotted again in the morning sky, significantly brighter than predicted. On 12 August the comet had a coma about one arcminute across and an apparent magnitude of 13.9. By August 19, when the comet was 1.7 AU from the Sun, its total magnitude (nucleus+coma) was estimated to be 11, but the comet did not show an obvious tail.
“C/2025 A6 (Lemmon)” enters the record as non-periodic comet. Crown Archives preserves that source wording while asking what Lemmon, non-periodic and comet can confirm, complicate or overturn.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jul 31, 2026. The linked authority identifier is Q135957518. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2025 and 2024.
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This entry incorporates text from “C/2025 A6 (Lemmon)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.