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"
Bright Perseids from Sweden
15 August 2026
Known for its bright and fast meteors, the annual Perseid Meteor Shower comes to planet Earth's skies from a radiant in the heroic constellation Perseus. The popular northern summer celestial spectacle is created as grains of dust cast off along the orbit of periodic comet 109P/Swift-Tuttle vaporize in Earth's dense atmosphere, tracing brief, but beautiful streaks through the night. Taken near the shower's peak of activity on August 12, this composite image recorded two bright perseid meteors and one meteor's watery reflection from a location near the coastal village of Grisslehamn, Sweden. Almost as bright as Altair, brightest star on the scene, the meteors appear along with the faint, diffuse background of the Milky Way. This year, the shower's peak activity coincided with a New Moon, so perseid meteor flashes were undiminished by bright moonlight. And for many skywatchers, this night of bright perseid meteors followed their viewing of the silhouette of the New Moon in a much anticipated solar eclipse. Growing Gallery: Solar Eclipse of 2026 August 12