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"
Where to See Comet Hyakutake
22 March 1996
People the world over are preparing to witness the closest approach of the brightest comet of the past twenty years. Comet Hyakutake, discovered just two months ago, will pass nearest the Earth Monday morning. All during the coming week, Comet Hyakutake will be visible in the northern sky as an unusual extended fuzzy patch. To see the comet is not difficult - just go outside and look up - no telescope is required! The comet's location in the sky during late March is charted above. The horizon is drawn for about 8 pm in your local time. By about 11 pm, Comet Hyakutake will be high in the sky and well placed for viewing. Although Comet Hyakutake is whizzing past the Earth at a blistering speed of almost 100,000 miles per hour, and it is practically streaking across the sky by astronomical standards, it will appear to move only a few degrees on any given night. Each night this weekend and in the coming week, the comet will be visible. Please don't miss this rare and exciting astronomical event! Latest Comet Hyakutake images: Crni Vrh Observatory, Slovenia, Fayetteville Observer-Times