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CometsComets are celestial objects composed of frozen gases, rock, and dust. They are characterized by two tails as they orbit near the sun, whose radiation and solar wind vaporize and push gas and dust away from the comet. Comets serve as frozen archives of early solar system chemistry, and some models suggest they played a crucial role in bringing water to Earth during its formation.
Most comets come from two regions of leftover material from the formation of the sun and planets: the Kuiper Belt—a disc of material beyond Neptune, approximately 20 times wider than the asteroid belt—and the Oort Cloud—a spherical shell of icy objects orbiting between 5,000 and 100,000 times the Earth-sun distance. Minor gravitational disruptions can bring comets in these regions toward the inner solar system on highly elliptical orbits. Those originating from the Kuiper Belt can have orbits that repeat with periods of less than 200 years, while those from the Oort Cloud may have periods of about a million years.
Comets are named after the person, observatory, or mission that discovered them following a coded naming system developed by the International Astronomical Union. For example, I3/ATLAS was identified by the Asteroid Terrestrial-impact Last Alert System and is the third interstellar comet—from beyond the Oort Cloud—ever observed.Explore Comets
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Find which comets are currently visible in the night skyIncorporating sightings reported in the Comet Observation database and information from NASA's Jet Propulsion Laboratory, this list provides a finder chart, star map, tracker, simulated orbit, and key properties for each comet, all viewable based on a user's input position on Earth. The Sky LiveExplore a guide to observing cometsBinoculars or telescopes can be used to see vivid tails, glowing comas, and brief bursts of brightness from these celestial objects. For photography, a DSLR or mirrorless camera with a wide-aperture lens, long exposure settings, and accessories such as tripods and star trackers is recommended. Space.comDark comets appear to be rocky asteroids but move like cometsCometary orbits are known to exhibit accelerations independent of gravity that result from forces related to the release of gases. Dark comets exhibit this behavior but lack visible clouds of frozen material that have turned into a gas—the coma the comets display—indicating minor quantities of escaping subsurface ice. University of MichiganView a gallery of notable cometsThe collection features 1973's Kohoutek, which had been dubbed the "comet of the century," 1965's Ikeya-Seki—one of the brightest comets of the millennium—and 2002's NEAT, a comet that survived a coronal mass ejection as it passed near the sun. Astronomy.comThe ancient Greeks and Romans viewed comets and meteors as divine omensBoth considered the appearance of a comet or its fragments as a precursor to significant events, such as the birth of a notable figure or the death of a ruler. One observed in 44 BCE was believed to be a sign of the deification of Julius Caesar after his assassination. The ConversationShooting stars, or meteors, are fragments of asteroids and cometsThese objects range in size from a grain of sand to a pebble and originate from the breaking apart of rocky asteroids due to collisions or from the debris of icy comets' tails. As they enter Earth's atmosphere, they burn up, creating streaks in the sky called meteor showers. NASAThere may be over one trillion comets in the Kuiper BeltNamed after Gerard Kuiper, who theorized the existence of a band of icy objects beyond Neptune in 1951, direct evidence for its existence did not arrive until 1992, when the first trans-Neptunian object, besides Pluto and its moon Charon, was observed. Comets with periods of less than 200 years originate from this belt. NASAComets can be categorized based on their orbital periodShort-period comets orbit around the sun once every 200 years or less and are made up of Jupiter-family (less than 20 years) and Halley-type (between 20 and 200 years) comet subgroups. Long-period comets have orbits greater than 200 years, while exocomets originate in solar systems outside our own. ESAThe names of comets can change based on subsequent observationsThe International Astronomical Union's coded naming system uses the first letter to indicate a comet's category, which can change over time. "D" represents comets that have been lost or broken up, while "A" applies to former comets that are now asteroids or dwarf planets. ESAEarth's water may have come from comets, asteroids, or its magma oceanBefore Earth's atmosphere formed, any liquid water would have boiled off, preventing the accumulation of water early on to create today's oceans. Planetary scientists continue to debate whether this water was delivered later from comet or asteroid collisions or via reactions between iron oxide in Earth's molten surface and hydrogen gas from the planetary nebula. Short WaveComets serve as time capsules of the early solar systemThe frozen objects preserve the molecular composition of the solar system's formation, dating back about 4.6 billion years. Spectral analysis of the gases they release when heated upon approaching the sun in eccentric orbits reveals this composition and helps assess solar system formation models. In Our Time: ScienceThe composition of comets earned them the nickname 'dirty snowballs'The icy relics of the solar system are composed of rock, gravel, dust, and frozen molecules, such as carbon dioxide, carbon monoxide, methane, ammonia, and water. Once close to the sun, these compounds sublimate into gases, creating a fuzzy cloud that earned the comets another nickname in history: hairy stars. CrashCourseNASA monitors potentially hazardous asteroids and cometsEstablished in 2016, the Planetary Defense Coordination Office characterizes and tracks asteroids and comets passing within 30 million miles of Earth. Over 40,000 near-Earth asteroids have been discovered, although estimates suggest that about 14,000 more such objects remain to be found. NASA ScienceComets in Pluto's orbit contributed to its demotion from planetary statusIn 2006, the International Astronomical Union formally defined a planet as an object in orbit around the sun with a nearly spherical shape and an orbital path clear of significant debris. Because Pluto shares its neighborhood with comets from the Kuiper Belt, it was reclassified as a dwarf planet. Australian Academy of ScienceAmerican local government comes in five distinct formsCounties, municipalities, townships, special districts, and school districts are each created for a different purpose, operating under different rules, and answerable to the state in different ways. Special districts, the least known of the group, are created for specific purposes, such as transit or fire protection. National League of CitiesMalaria comes from the Italian term 'mal'aria,' meaning 'bad air'The term refers to marshy areas associated with the disease. An estimated 94% of malaria cases—215 million—occur in Africa. National Library of MedicineMold growth in space raises the hypothesis of life being brought to EarthPanspermia suggests that life could be carried throughout the cosmos by asteroids, comets, and other objects, but it requires organisms that can withstand the extreme cold of space travel, stellar radiation, lack of water, and intense heat of planetary impacts. The discovery of mold on the International Space Station and experiments showing it can withstand radiation in outer space-like conditions increase the plausibility of the hypothesis. StarTalkA year before Elvis appeared on 'Ed Sullivan,' Bill Haley brought rock 'n' roll to the programAlthough Elvis Presley's 1956 appearance on the popular TV show is viewed as a key moment in the rise of rock 'n' roll, the music appeared on the program a year earlier, on August 5, 1955, when Bill Haley and His Comets performed their hit "Rock Around the Clock." The Ed Sullivan Show'Graffiti' comes from the Italian for 'a scribbling'The word was first used in 1851 to describe the ancient inscriptions on Pompeii's walls. "Graffiti" is the plural form of "graffito," which means "a scribbling." EtymonlineThe word peptide comes from GreekOriginating from the Greek term "peptos," which means digestible, peptide as a word refers to two or more amino acids. (Some users may encounter a paywall.) Springer NatureThe word 'restaurant' comes from the Latin for 'restore'Many believe the word came into use thanks to Boulanger, an 18th-century Parisian soup vendor. According to legend, his shop claimed it served "bouillons restaurants," or "restorative broths." Merriam-WebsterThe word 'Peloton' comes from the word for the main group of riders in a cycling raceThe word itself is French for "ball," but became the inspiration for the word "platoon" in the 17th century to describe a group of soldiers. Now, it's a common cycling term and the main focal point in cycling races. Merriam-WebsterThe word ‘coupon’ comes from a French word meaning ‘to cut’The history of coupons starts in the US with the Coca-Cola coupon that was mailed to consumers, offering them a chance to come try the soda for free in a nearby pharmacy. A coupon created by cereal company Post is one of the earliest widely cited follow-ups—it offered a penny off a box of Grape Nuts in 1909. CNBCToasting with ‘cheers!’ comes from Anglo-FrenchEtymologists trace the word back to about 1200 CE, when Anglo-French became the vernacular after the Norman Conquest of 1066. “Chere” meant “the face,” or an expression, often of joy. After that, it was used in the 18th century as a form of encouragement before becoming a common toast in the 20th century. EtymonlineHalley's comet is named after the astronomer who predicted its next appearanceEdmund Halley realized that historical accounts of a celestial object passing in the night sky in 1531 and 1607 referred to the same object he observed in 1682. By applying Newtonian mechanics to his observational data, he calculated its orbit and accurately predicted its return in 1758. Penn MuseumDeep Impact was the first mission to probe beneath a comet's surfaceThe NASA mission sent a probe to deliberately crash into comet Tempel 1, producing an explosion equivalent to 4.7 tons of TNT. The payload included a compact disk with more than 625,000 names of people who participated in the "Send Your Name to a Comet!" campaign. NASAThe European Space Agency placed a lander on the surface of a comet in 2014Launched in 2004, the Rosetta spacecraft performed three flybys of Earth and one of Mars as gravitational slingshots to gain the necessary velocity to successfully place the Philae lander module on comet 67P/Churyumov-Gerasimenko. Philae achieved a soft landing only after bouncing twice from failed deployments of its anchoring harpoons. VoxThe Oort Cloud is a shell of icy objects surrounding the solar systemProposed in 1950 by Jan Oort, the theoretical structure is believed to be the origin of comets with periods of more than 200 years. Leftover planetary building blocks from the early solar system formed the Oort Cloud after being flung out by the gravity of planets like Jupiter. Space.comA comet's tails point away from the sun, rather than trailing its motionThe ion tail, composed of gases ionized by solar radiation and pushed by the solar wind, points away from the sun. In contrast, the dust tail is pushed away by radiative pressure and curves away from the comet's motion. As the comet approaches the sun, both tails get longer. Swinburne University of TechnologyVisualize the anatomy of a cometThe solid nucleus holds the frozen molecules, which are heated into a gaseous state once the comet is within three times Earth's distance from the sun. The surrounding coma, from which comets get their name, is a spherical cloud that can grow larger than Jupiter, from which tails develop. ESASee how CES comes to life with a massive setup across Las VegasThis behind-the-scenes video shows crews assembling the sprawling CES show—filling more than 2.5 million square feet of exhibition space with booths, lights, and tech from around the world ahead of the event’s opening. CESOne man in Arizona works to defend Earth from catastrophic space rocksDavid Rankin, an observer and operations engineer at the NASA-funded Catalina Sky Survey, spends his days scanning for solar system objects that could collide with our planet. The job requires employees to work long shifts to help prevent asteroids from destroying our planet. Smithsonian MagazineOil originates from from trillions of tiny algae and planktonDespite the misconception that oil comes from dinosaurs, the resource is the result of these tiny organisms being subjected to high-pressure and low-temperature environments once they were buried under layers of sediment over the course of tens to hundreds of millions of years. Today I Found OutThe name ‘tardigrades’ comes from the Latin word for ‘slow walkers’Before being renamed for their movements, German pastor Johann August Ephraim Goeze called them Kleiner Wasserbär—little water bears—in the first published observations of the creatures in 1773. He noted their voracious appetite made them seem like bears under a microscope. The Public Domain ReviewZora Neale Hurston's 'Spunk' spent decades languishing in the Library of CongressThe author, known for her masterwork "Their Eyes Were Watching God," wrote the play in 1935, but it was mostly unknown. In 1997, it was re-discovered in the Library of Congress' drama collection, a repository for plays that were not copyrighted because they were never staged. The New York TimesMagnetism comes from quantum properties of electrons aligning in specific structuresPermanent magnets exist because electrons have an intrinsic magnetic moment, which can align in certain atoms. When many such atoms line up their magnetic fields within regions called domains, the result is a visible, macroscopic magnetic effect. minutephysicsThe standing ovation comes from an ancient Roman military traditionOvation is derived from the Latin for “I rejoice” and was a ceremonial salute to military generals who'd been victorious in battle. Mental FlossFireworks usage on Independence Day comes from their celebratory use in ancient ChinaBurning bamboo stalks produces a small explosion that was believed to ward off evil spirits. As knowledge of fireworks, which initially used these stalks, carried over into other cultures, so did their use to promote good luck and celebration. History.comScientists determine the smells of objects in outer spaceUsing spectrographic techniques, scientists determine the chemical composition of planetary atmospheres, comets, and other objects in space. Combining these chemicals in labs on Earth has revealed locations in space that smell like nail polish remover, rotten fish, and urine. BBCCan physics explain where consciousness comes from?Consciousness is a complex emergent phenomenon of the brain, which is primarily composed of neurons and glial cells. Since all matter is composed of atoms that follow the laws of physics, there may be quantum processes beyond classical electrochemical interactions that can explain where consciousness comes from. Big ThinkIn 1994, fragments of comet Shoemaker-Levy 9 crashed into JupiterHubble captured the collisions, which created massive black impact sites visible from space. It represented the first time scientists could prepare for and observe an interplanetary collision in real time, allowing them to gather valuable information about Jupiter’s atmosphere. NASA GoddardView galleries of images taken by the Hubble Space TelescopeWith more than 1.7 million observations made since 1990, the Hubble Space Telescope has captured images of space missions, planets, stellar nurseries, interstellar comets, star clusters, galaxies, and more. This search tool allows users to sort and filter across these celestial objects to explore over 35 years of Hubble's astrophotography. NASA ScienceCava is Spain's sparkling wineChampagne is delicious, but it’s not the most budget-friendly beverage. Cava is a Spanish wine produced through the same traditional method used to make Champagne but often sold at a lower price. Cava can be produced in several different regions, offering the possibility of more diversity than what is typically found in Champagne. Wine EnthusiastThe 1819 novel 'Ivanhoe' popularized the word 'freelancing'In the novel, the author wrote about “free-lances:” mercenary soldiers who were “free” to use their weapons (called, yes, “lances”) in service of whoever paid them the most. A video details that story and other gig economy basics. TED-EdThe dangerous comet behind the Perseids meteor showerEvery summer, Earth passes through the debris trail of the Swift-Tuttle comet, producing the spectacle of the Perseids meteor shower. The phenomenon is a glorious opportunity for amateur stargazers, but astronomers have long noted the comet's orbit... Big ThinkExplore the major asteroids in our solar systemThis 3D solar system visualization displays the positions of known asteroids, comets, and spacecraft involved in asteroid studies. Major asteroids include additional details, including orbital trajectories and discovery dates. NASACharting where federal revenue comes fromAbout 50 percent of federal revenue comes from individual income taxes, 7 percent from corporate income taxes, and another 36 percent from payroll taxes that fund social insurance programs. See breakdown in charts here. Tax Policy CenterWhen it comes to locavore, what we eat is more important than how far it traveledWhat we still misunderstand about climate change and local food. VoxVisualizing where happiness comes fromResearchers asked 10,000 participants to list 10 things that recently made them happy. One author broke down the responses into subject-verb-object categories, isolating the people and events that made responders satisfied. The result highlights how simple things like having dinner or watching a movie made someone happy. Dive in and look for some ideas or tips on feeling happy today with this fascinating visualization. FlowingDataThe black hole information paradox comes to an endQuanta Magazine provides a deep dive into black holes and the black hole information paradox. For a very long time it was believed nothing could escape a black hole. Therein lies the paradox. Per quantum mechanics, whatever falls into a black hole should not necessarily be lost forever, and may eventually return. In a landmark series of calculations, physicists have proved that black holes can shed information. Quanta Magazine