Comets
Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. When frozen, they are the size of a small town. When a comet's orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the Sun for millions of miles. There are likely billions of comets orbiting our Sun in the Kuiper Belt and even more distant Oort Cloud.
   Comets Blog
ALPO Comet News for NOV 2025
11/1/2025
November will be active with bright and interesting comets. Now past its peak brightness, C/2025 A6 (Lemmon) begins the month in the evening sky at around 4th magnitude. It will fade to 5th magnitude by mid-month and, unfortunately, will also disappear from our view at that time as it moves close to the Sun. Another bright evening comet, C/2025 R2 (SWAN), starts the month at 7th magnitude but should quickly fade as the month progresses.
In the morning sky, we will see the return of the interstellar comet 3I/ATLAS, which reappears in early November for northern observers and late November for southern observers. It may shine as bright as magnitude 9 or 10 early in the month. Also visible in the morning sky is the “red comet” C/2025 K1 (ATLAS), which is also about magnitude 9 to 10.
The monthly ALPO Comet News PDF can be found here. All are encouraged to join the discussion over at Cloudy Nights at https://www.cloudynights.com/forums/topic/983706-alpo-comet-news-for-november-2025/
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   Comets News Headlines
Irradiated Comet 3I/ATLAS Glows Green and Hides Its Tail in New Image
11/11/2025

TBD
New images of the interstellar comet 3I/ATLAS reveal it is glowing green and has a surprisingly minimal tail structure as it moves through the inner solar system. The intense green hue is believed to be caused by the irradiation of diatomic carbon, which is excited by the Sun's ultraviolet light. This unique coloration and the comet's overall appearance are providing astronomers with key data about objects originating from other star systems.

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Astronomer Reveals First Look at Comet 3I/Atlas as It Reappears
11/4/2025

TBD
An astronomer has captured the first new optical images of the interstellar visitor Comet 3I/ATLAS since it passed behind the Sun. The observations were made using both a powerful research telescope and a smaller amateur instrument, providing fresh data on the comet's appearance. The finding is significant because 3I/ATLAS originated outside our solar system, making it a unique object of study for clues about other star systems.

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Awakening an Interstellar Wanderer: Surprising Nickel Detection in Comet 3I/Atlas
10/27/2025

TBD
The detection of nickel, a typically rare element in comets, within the interstellar visitor 3I/ATLAS is providing scientists with new data on its nature. The finding, which required the high sensitivity of the Hubble Space Telescope, is unusual because nickel is often stripped away during a comet's long cosmic journey. Researchers believe this chemical signature may reveal clues about the comet's ancient origins and the unique conditions of its birth in another star system.

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More Comets News Headlines
   Event Calendar

Nov 03, 2021
Comet 67P/Churyumov-Gerasimenko will make its closest approach to the Sun, at a distance of 1.21 AU.

Nov 07, 2021
Comet 67P/Churyumov-Gerasimenko is forecast to reach its brightest magnitude in Gemini.

Jan 02, 2022
Comet C/2021 A1 (Leonard) will make its closest approach to the Sun, at a distance of 0.62 AU.

Full Comets Section Calendar