Comets

Comets are frozen bodies of ice, rock and dust that grow a glowing head and a tail when their orbits bring them near the Sun.^[1] They are leftovers from the formation of the solar system about 4.6 billion years ago, arriving from the Kuiper Belt beyond Neptune and from the far more distant Oort Cloud.^[2] The first three objects known to have come from other star systems passed through between 2017 and 2025; the third was comet 3I/ATLAS.^[3]

Happening now

Comet

Comet C/2026 C1 (Tsuchinshan)

Long-period comet · 1.15 AU from the Sun at closest

November 6, 2028

Guides

Comets: what they are and how to see oneWhat comets are made of, where they come from, how they are named, and how to find one in the sky with your eyes or binoculars.
Interstellar visitorsThe first three objects known to have come from other star systems, 1I/'Oumuamua, 2I/Borisov and 3I/ATLAS, and how they were recognized.

Terms

Coma Comet tail Long-period comet

All terms in the Glossary

Sources

[1]NASA, Comets — science.nasa.gov, retrieved October 26, 2026
[2]NASA, Comets: Facts — science.nasa.gov, retrieved October 26, 2026
[3]NASA, Comet 3I/ATLAS — science.nasa.gov, retrieved October 26, 2026