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"
Tau Herculids from Space
4 June 2022
On May 31 tens of parallel meteor streaks were recorded in this 8 degree wide field of view of planet Earth's limb from space. The image is one of a series of 5 minute long observations by the orbiting Yangwang-1 space telescope. It was captured at 03:43 UT, near the peak of the Tau Herculid meteor shower. As predicted, the meteor shower was an active one this year, caused as Earth swept through a relatively dense stream of debris from disintegrating Comet 73P/Schwassmann-Wachmann 3, but was lacking bright meteors. Nearly all of the Tau Herculid meteors in the Yangwang-1 image are too faint to be detected by groundbased instruments. But on that date patient earthbound skywatchers under clear skies still enjoyed a memorable showing of the Tau Herculids.