Comet
A comet is a small Solar System body composed mainly of ice, dust, and organic compounds. As they approach the Sun, cometary ices sublimate, releasing gas and dust that form the glowing coma and distinctive tails—often extending millions of kilometers.
Comets originate from two primary reservoirs: the Kuiper Belt—home to short-period comets with orbits under ~200 years—and the distant Oort Cloud, which sends long-period comets with orbits spanning thousands of years. Occasionally, interstellar objects like ‘Oumuamua pass through our system, appearing comet-like.
They are “dirty snowballs” and among the most primitive remnants of the early Solar System, preserving original ices and organic material from 4.6 billion years ago.
Landmark missions include ESA’s Rosetta—with its lander Philae—which orbited and sampled Comet 67P/Churyumov–Gerasimenko (2014–2016). NASA’s Deep Impact struck Comet Tempel 1 in 2005 to analyze interior composition.
These missions discovered complex organic molecules, including amino-acid precursors, and supported the theory that comets may have delivered water and prebiotic compounds to early Earth.
Looking ahead, ESA–JAXA’s Comet Interceptor (launch planned for 2029) intends to perform a rapid flyby of a dynamically new or interstellar comet, using multiple spacecraft to sample both nucleus and coma environments.
Comets are studied across the electromagnetic spectrum—from radio to gamma rays—using telescopes and spacecraft to understand composition, internal structure, activity, and their roles in planetary formation, the evolution of the solar system, and the origin of life.
Sources
APODs including "Comet"
Perseids Over a little Planet
12 August 2026
It looks like a view from the Little Prince's planet. The featured image is a throwback to the 2024 Perseid meteor shower, surrounded in this projection by the Bieszczady Mountains in Poland. Visible in the sky is the arch of the Milky Way, along with several nebulas in red and over a hundred meteors pointing to the radiant. The Perseids are easily visible and quite popular in the Northern Hemisphere summer. (Watching meteor showers in the winter is less convenient for a good reason). This year they are expected to offer an even more dazzling spectacle than usual, because the peak coincides with a new moon. The 2026 Perseid meteor shower will peak tonight with as many as 50-100 meteors per hour, when the Earth's path crosses through debris left behind by Comet Swift-Tuttle. Typically, the best times for seeing the meteors are between midnight and pre-dawn. You won't need binoculars to see the meteors, but a lawn chair and a dark sky location help. There is total solar eclipse happening today! See here if you are in the path of totality.