when did halley's comet last visit earth

In 1986, the European spacecraft Giotto became one of the first spacecraft ever to encounter and photograph the nucleus of a comet, passing and imaging Halley's nucleus as it receded from the Sun. Credit: Halley Multicolor Camera Team, Giotto Project, ESA | More about this image

Halley is often called the most famous comet because it marked the first time astronomers understood comets could be repeat visitors to our night skies. Astronomers have now linked the comet's appearances to observations dating back more than 2,000 years.

Halley was last seen in Earth's skies in 1986 and was met in space by an international fleet of spacecraft. It will return in 2061 on its regular 76-year journey around the Sun.

The History of Halley's Comet

Until the time of English astronomer Edmond Halley (1656-1742), comets were believed to make only one pass through the solar system.

But in 1705, Halley used Isaac Newton's theories of gravitation and planetary motions to compute the orbits of several comets. Halley found the similarities in the orbits of bright comets reported in 1531, 1607, and 1682 and he suggested that the trio was actually a single comet making return trips. Halley correctly predicted the comet would return in 1758. History's first known "periodic" comet was later named in his honor.

The comet has since been connected to ancient observations going back more than 2,000 years. It is featured in the famous Bayeux tapestry, which chronicles the Battle of Hastings in 1066.

In 1986, an international fleet spacecraft met the comet for an unprecedented study from a variety of vantage points. The science fleet included Japan's Suisei and Sakigake spacecraft, the Soviet Union's Vega 1 and Vega 2 (repurposed after a successful Venus mission), the international ISEE-3 (ICE) spacecraft, and the European Space Agency's Giotto. NASA's Pioneer 7 and Pioneer 12 also contributed to the bounty of science data collected.

Halley's Connection to Meteor Showers

Each time Halley returns to the inner solar system its nucleus sprays ice and rock into space. This debris stream results in two weak meteor showers each year: the Eta Aquarids in May and the Orionids in October.

Halley's dimensions are about 9.3 by 5 miles (15 kilometers by 8 kilometers). It is one of the darkest, or least reflective, objects in the solar system. It has an albedo of 0.03, which means that it reflects only 3% of the light that falls on it.

Comet Halley moves backward (opposite to Earth's motion) around the Sun in a plane tilted 18 degrees to that of the Earth's orbit. Halley's backward, or retrograde, motion is unusual among short-period comets, as its greatest distance from the Sun (aphelion) is beyond the orbit of Neptune.

Halley's orbit period is, on average, 76 Earth years. This corresponds to an orbital circumference around the Sun of about 7.6 billion miles (12.2 billion kilometers). The period varies from appearance to appearance because of the gravitational effects of the planets. Measured from one perihelion passage to the next, Halley's period has been as short as 74.42 years (1835-1910) and as long as 79.25 years (451-530).

The comet's closest approach to Earth occurred in 837, at a distance of 0.033 AU (3.07 million miles or 4.94 million kilometers). At that time, April 10, 837, Halley reached a total apparent brightness of about magnitude -3.5, nearly that of Venus at greatest brilliance. The light of Halley was spread over an extended area, however, so its surface brightness was less than that of Venus.

During its 1986 appearance, Halley's nearest approach to Earth occurred on the outbound leg of the trip at a distance of 0.42 AU (39 million miles or 63 million kilometers). It was slightly brighter than the north star Polaris but again spread over a much larger area than a point-like star.

At aphelion in 1948, Halley was 35.25 AU (3.28 billion miles or 5.27 billion kilometers) from the Sun, well beyond the distance of Neptune. The comet was moving 0.91 kilometers per second (2,000 mph). At perihelion on Feb. 9, 1986, Halley was only 0.5871 AU (87.8 million km: 54.6 million miles) from the Sun, well inside the orbit of Venus. Halley was moving at 122,000 mph (54.55 kilometers per second).

With each orbit around the Sun, a comet the size of Halley loses an estimated 3 to 10 feet (1 to 3 meters) of material from the surface of its nucleus. Thus, as the comet ages, it eventually dims in appearance and may lose all the ices in its nucleus. The tails disappear at that stage, and the comet finally evolves into a dark mass of rocky material or perhaps dissipates into dust.

Scientists calculate that an average periodic comet lives to complete about 1,000 trips around the Sun. Halley has been in its present orbit for at least 16,000 years, but it has shown no obvious signs of aging in its recorded appearances.

How Comet 1P/Halley Got Its Name

Comets are usually named for their discoverer(s) or for the name of the observatory or telescope used in the discovery. Since Halley correctly predicted the return of this comet ​– the first such prediction – it is named to honor him. The letter "P" indicates that Halley is a "periodic" comet. Periodic comets have an orbital period of less than 200 years.

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A Brief History of Halley’s Comet

By: Evan Andrews

Updated: June 1, 2023 | Original: November 8, 2016

For much of history, comets were thought to be divine omens, atmospheric anomalies or celestial wanderers that flashed through the solar system before vanishing into interstellar space. All that started to change in 1705, when the English astronomer Edmond Halley published his “Synopsis Astronomia Cometicae.” By using Sir Isaac Newton’s gravitational theories to chart the paths of two dozen comets, Halley hit on a provocative new theory: three comets seen in 1531, 1607 and 1682 were actually the same object. Halley argued that the comet orbited the sun and whizzed by the Earth roughly once every 76 years, and he predicted that it would reappear sometime in late 1758 or early 1759. “If it should return, according to our predictions,” he vowed, “impartial posterity will not refuse to acknowledge that this was first discovered by an Englishman.”

Halley was eventually proved correct on all counts. Although he died in 1742, his comet appeared in the sky on Christmas night of 1758, right on schedule. Its discovery was hailed as a triumph of scientific reasoning and Newtonian physics. “By its appearance at this time, the truth of the Newtonian Theory of the Solar System is demonstrated to the conviction of the whole world, and the credit of the astronomers is fully established and raised far above all the wit and sneers of ignorant men,” the British publication the Gentleman’s Magazine wrote. Shortly thereafter, the French astronomer Nicolas-Louis de Lacaille named the comet in Halley’s honor.

Scientists now believe that comet 1P/Halley, as it is formally known, has been zipping through the solar system for as many as 200,000 years. Edmond Halley only identified a handful of occurrences of his comet, but other scholars have plotted its earlier appearances and uncovered historical references dating back to the ancient world. In a 2010 paper in the Journal of Cosmology, researchers Daniel W. Graham and Eric Hintz suggested that one of the earliest known sightings of Halley’s comet may have occurred around 466 B.C. in the skies over Greece. Ancient accounts of the incident mostly center on a “wagon-sized” meteorite that landed in the Hellespont, but they note that the strike was accompanied by a “huge fiery body” that was visible in the sky for 75 days. According to Graham and Hintz, the timetable matches up almost perfectly with Halley’s comet’s projected appearance in the fifth century B.C.

While it’s possible that the comet the Greeks saw was Halley’s, more reliable accounts of its flybys didn’t appear for another few centuries. One of the most famous references is found in China in the Han Dynasty’s “Records of the Grand Historian,” which describes a “broom star” that appeared in the sky in 240 B.C. Other early sightings came from the Babylonians, who recorded the comet’s 164 B.C. and 87 B.C. transits on clay tablets; and from the Romans, who made reference to it in 12 B.C.

Halley’s comet inspired both fascination and horror in its early observers. The celestial visitor was often considered a bad omen, and it was linked to everything from the death of kings to natural disasters. The historian Flavius Josephus described the comet of 66 A.D. as a “star resembling a sword” and considered it a portent of the destruction of Jerusalem by the Romans. Several centuries later, the comet of 451 was thought to signal Attila the Hun’s defeat at the Battle of the Catalaunian Plains. In 837, meanwhile, the Holy Roman Emperor Louis the Pious feared the comet was a signal of his downfall and tried to ward off its influence with fasting, prayer and alms for the poor.

By far the most famous appearance of Halley’s comet occurred in 1066, when it coincided with the Norman Conquest. According to the Anglo-Saxon Chronicle, in the months before William the Conqueror set sail for England, “a portent such as men had never seen before was seen in the heavens.” Contemporary observers considered the “long-haired star” a bad omen for the English King Harold II, and the prophecy was later fulfilled when William defeated and killed him at the Battle of Hastings. Halley’s comet was later included in a section of the famed Bayeux Tapestry, which depicts King Harold and a crowd of fearful Englishmen watching it streak through the sky.

The strange effects of Halley’s comet only continued over the next several centuries. Its 1222 appearance is sometimes credited with inspiring Genghis Khan to dispatch his Mongols on an invasion of Europe, and its 1456 return famously overlapped with the Ottoman Empire’s invasion of the Balkans. The comet may have also crept into works of art. After viewing it in 1301, the Italian artist Giotto is said to have depicted Halley’s comet as the star of Bethlehem in his painting “Adoration of the Magi.”

People began watching the comet with a more scientific eye in the 16th and 17th centuries, but it was still causing anxiety as recently as 1910. As the comet neared the Earth that year, the New York Times wrote that a French astronomer named Camille Flammarion had warned that poisonous cyanogen gas in its tail might “impregnate the atmosphere and snuff out all life on the planet.” Other scientists dismissed the claim as nonsense, but the prediction still sparked a minor panic. Before the comet passed by without incident that spring, many people sealed up their homes to keep out the fumes, stocked up on gas masks, and went to churches to pray for salvation. The more gullible among them even bought “anti-comet pills” from street vendors.

Halley’s most recent return in 1986 marked the first time that scientists were able to study it with sophisticated technology. High-powered telescopes were trained on the comet from Earth, and five unmanned space probes dubbed the “Halley Armada” conducted flybys as it made its transit. One of them, the European Space Agency’s “Giotto,” even inched within 370 miles of the comet’s nucleus. The high-quality images returned by the probes were the first of their kind and provided fascinating insight into Halley, including proving once and for all that its core is a solid mass primarily composed of dust and ice. So far, no space agency has announced plans for another mission in the future, but there’s still plenty of time: the famed comet is not scheduled to make its next visit to the inner solar system until July 2061.

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Halley’s Comet

A Frequent Guest in Earth’s Cosmic Backyard

By: Christina Griffith

Originally Published in 2019

Every 75 years or so, Halley’s Comet, also known as Comet Halley, passes through Earth’s neighborhood along its orbit. Since the dawn of man, many humans have been fortunate enough to see it twice in their lifetimes.

American astronomer Fred Whipple coined the phrase “dirty snowball” to describe the composition of comets we are familiar with today. Comets are made of ice, dust, and small particles of rock. They are solar system bodies that usually orbit the sun in highly eccentric orbits that could take them millions of years to complete. Comets that take less than 200 years to make the journey, like Halley’s, are called periodic. When these cosmic travelers pass closer to the sun, the warmth heats the icy nucleus and it begins to release gasses. This produces the characteristic “coma,” or what we call the comet’s tail.

Civilizations around the world have recorded the regular appearance of Halley’s Comet. The first confirmed sighting is believed to have been made by Chinese astronomers in 239 BCE, documented in the Shih Chi and Wen Hsien Thung Khao chronicles. However, in 2010 researchers with Brigham Young University at Provo, Utah reviewed Greek histories describing a meteor strike in the Hellespont region between 468 and 466 BCE, which occurred at the same time as a comet sighting. Based on the timing and trajectory of the comet described, this might possibly be the earliest recorded sighting of Comet Halley.

The Babylonians documented astronomical observations in cuneiform texts called astronomical diaries. Only a handful survive, but archaeologists have discovered tablets and fragments that date from ca. 750 BCE to possibly as late as 75 CE. Though heavily damaged, what remains of these texts tells us the Babylonians had meticulously mapped the sky and made daily observations of the movements of celestial bodies. In both 164 and 87 BCE the Babylonians recorded the apparition of a comet. Researchers have been able to use the astronomical data about the path and timing of the sightings to confirm these were both Comet Halley.

Roman records first document the appearance in 12 BCE and again in 66 CE by Flavius Josephus. This apparition was considered a harbinger of the Roman destruction of Jerusalem.

It was the return of Halley’s Comet in 1066 CE that cemented its place in the annals of historic omens. Its appearance in the skies that winter was taken as a portent of bad news for Anglo-Saxon King Harold II. William the Conqueror would lead the Norman invaders to victory months later at the Battle of Hastings.

Identifying Halley’s Comet

Edmund Halley (1656–1742), a British astronomer, mathematician, and physicist, determined in the 17th century that the comet that passed overhead in 1531, 1607, and 1682 was the same body. He was an accomplished scientist who throughout his career made invaluable contributions to star charts, recorded Mercury’s transit across the sun, and calculated the size of the solar system based on Venus’s orbit. A protégé of Sir Isaac Newton, Halley made observations to prove Newton’s laws of motion and funded the publication of the Principia Mathematica . From an observatory on Saint Helena island in the southern Atlantic in September of 1682 he observed the same comet reported 75 and 76 years earlier, calculated its orbit, and predicted its return. The comet was named after him posthumously when it appeared, as he predicted, in 1758.

Incidentally, the name “Halley” is traditionally pronounced like valley . It is believed that the American pronunciation is due to an association with the 1950s band Bill Haley and his Comets. Halley’s Comet’s last pass was in 1986, which was unfortunately a poor opportunity to observe the comet for Earth-dwellers: not only were we on opposite sides of the sun, but the comet was relatively far away compared to earlier passages, and our modern visibility was diminished by pollution. Fortunately, for the first time in human history, we were able to go to it. The Soviet Union, the European Space Agency, and Japan launched probes to study and photograph the comet. The International Cometary Explorer, a satellite launched in 1978 in a heliocentric orbit to study solar winds and earth’s magnetosphere, was repurposed in 1982 to intercept comets. It flew through Halley’s tail, collecting vital data. Our next opportunity to see Comet Halley will be in 2061.Ä

CHRISTINA GRIFFITH is Associate Editor of Expedition.

FOR FURTHER READING Edwards, L. “First sighting of Halley’s Comet pushed back two centuries.” PhysOrg , September 13, 2010. https://phys.org/ news/2010-09-sighting-halleys-comet-centuries.html#jCp

Graham, D.W. and E. Hintz. “An Ancient Greek Sighting of Halley’s Comet?” Journal of Cosmology 9 (2010): 2130–2136. journalofcosmology.com/AncientAstronomy106.html

Stephenson, F.R., K.K.C. Yau, and H. Hunger. “Records of Halley’s Comet on Babylonian tablets.” Nature 314 (1985): 18.

Cite This Article

This digitized article is presented here as a historical reference and may not reflect the current views of the Penn Museum.

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Halley's Comet: Visitor from the Depths of the Solar System

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Everyone's heard of Comet Halley, more familiarly known as Halley's Comet. Officially called P1/Halley, this solar system object is the most famous known comet. It returns to Earth's skies every 76 years and has been observed for centuries. As it travels around the Sun, Halley leaves behind a trail of dust and ice particles that form the annual Orionid Meteor shower each October. The ices and dust that make up the comet's nucleus are among the oldest materials in the solar system, dating back to before the Sun and planets formed some 4.5 billion years ago.

Halley's last apparition began in late 1985 and extended through June of 1986. It was studied by astronomers around the world and even was visited by spacecraft. Its next close "flyby" of Earth won't happen until July 2061, when it will be well placed in the sky for observers. 

Comet Halley has been known about for centuries, but it wasn't until the year 1705 that astronomer  Edmund Halley  calculated its orbit and predicted its next appearance. He used  Isaac Newton 's recently developed Laws of Motion plus some observational records and stated that the comet—which appeared in 1531, 1607 and 1682—would reappear in 1758.

He was right—it showed up right on schedule. Unfortunately, Halley did not live to see its ghostly appearance, but astronomers named it after him to honor his work. 

Comet Halley and Human History

Comet Halley has a large icy nucleus, just as other comets do. As it nears the sun, it brightens up and can be seen for many months at a time. The first known sighting of this comet occurred in the year 240 and was duly recorded by the Chinese. Some historians have found evidence that it was sighted even earlier, in the year 467 BCE, by the ancient Greeks. One of the more interesting "recordings" of the comet came after the year 1066 when King Harold was overthrown by William the Conqueror at the Battle of Hastings.The battle is depicted on the Bayeux Tapestry, which chronicles those events and prominently displays the comet over the scene. 

In 1456, on a return passage, Halley's Comet Pope Calixtus III determined it was an agent of the devil, and he attempted to excommunicate this naturally occurring phenomenon. Obviously, his misguided attempt to frame it as a religious issue failed, because the comet came back 76 years later. He wasn't the only person of the time to misinterpret what the comet was. During the same apparition, while Turkish forces laid siege to Belgrade (in today's Serbia), the comet was described as a fearsome celestial apparition "with a long tail like that of a dragon." One anonymous writer suggested it was "a long sword advancing from the west... "

Modern Observations of Comet Halley

During the 19th and 20th centuries, the comet's appearance in our skies was greeted by scientists with great interest. By the time the late 20th century apparition was about to start, they had planned extensive observing campaigns. In 1985 and 1986, amateur and professional astronomers worldwide united to observe it as it passed close by the Sun. Their data helped fill in the story of what happens when a cometary nucleus passes through the solar wind. At the same time, spacecraft explorations revealed the lumpy nucleus of the comet, sampled its dust tail, and studied very strong activity in its plasma tail. 

During that time, five spacecraft from the USSR, Japan, and the European Space Agency journeyed to Comet Halley. ESA's Giotto obtained close-up photos of the comet's nucleus, Because Halley is both large and active and has a well-defined, regular orbit, it was a relatively easy target for Giotto and the other probes. 

Comet Halley's Schedule

Although the average period of Halley's Comet's orbit is 76 years, it's not that easy to calculate the dates when it will return by simply adding 76 years to 1986. Gravity from other bodies in the solar system will affect its orbit. Jupiter's gravitational pull has affected it in the past and could do so again in the future when the two bodies pass relatively near each other.

Over the centuries, Halley's orbital period has varied from 76 years to 79.3 years. Currently, we know that this celestial visitor will return to the inner solar system in the year 2061 and will pass its closest to the Sun on July 28th of that year. That close approach is called "perihelion." Then it will make a slow return to the outer solar system before heading back for the next close encounter some 76 years later.

Since the time of its last appearance, astronomers have been avidly studying other comets.The European Space Agency sent the Rosetta spacecraft to Comet 67P/Churyumov-Gerasimenko, which went into orbit around the comet's nucleus and sent a small lander to sample the surface. Among other things, the spacecraft watched numerous dust jets "turn on" as the comet got closer to the Sun . It also measured the surface color and composition, "sniffed" its smell , and sent back many images of a place most people never imagined they would see. 

Edited by Carolyn Collins Petersen.

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news From the Archives

Close Encounters: Halley’s Comet last came along in 1986

Tonight the remains of the visit can be viewed as part of the orionid meteor shower..

By Meagan Hurley

12:59 PM on Oct 21, 2019 CDT

Editor’s note: Take a look back in The Dallas Morning News Archives .

Comet Halley was last seen in the inner solar system in 1986 but shares its presence with the Earth annually as the planet passes through the remnants of debris left behind from its last visit. This event, known as the Orionid meteor shower, will reach its peak in 2019 between the early hours of Oct. 21-22. It is one of the quickest, brightest and most visible meteor showers.

The comet only appears once or twice in a lifetime, has only come along once since 1910, and will not appear again until 2061.

Take a walk through the Dallas Morning News’ coverage of the event that arrives only once every 75 years or so.

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The general consensus was that the visibility of Halley’s Comet in ’86 was not going to be as clear as its arrival in 1910. However, that did not keep people from doing whatever they could to see the comet in action.

Gayle Golden, science writer for The News , covered one of the recreational flights that had passengers who paid to get a better view of the infamous comet. This was just one of the options for people who wanted an up close and personal experience.

Advertisers also took advantage of the event. There were several vendors selling “experience packages” to view the Comet in various locations, as well as those using the excitement over the event to offer discounts.

In addition to the fanfare caused by Comet Halley, there were also many scientific observations made. The News reported on the importance of these advances and created educational graphics that helped explain the details behind the events.

In 1910, Halley’s Comet was photographed for the first time. While the comet has been tracked for centuries, the level of physical evidence has varied.

There was a lot of comet-related coverage in The News from January to June of 1910. The Earth passed through the comet’s tail on May 18, 1910. People were worried about what would happen, but the best astronomers concluded there would be no disturbance.

On Jan. 23, 1910, it was reported that the most recent occurrence of the comet was in 1835 when Andrew Jackson was president of the U.S., much of which was still wilderness, and “not a single observatory had yet been established." The year 1910 was a groundbreaking one for astronomers looking at Halley’s Comet.

Want to read more about the events that shaped our history? Become a Plus member at archives.dallasnews.com .

Meagan Hurley , Researcher . Meagan is a researcher in the Research and Archives department. Before joining The Dallas Morning News, she worked in academic libraries and law firms. She graduated from the University of Texas at Austin and loves college football, dogs, and writing about history.

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Halley's Comet has begun its return journey to Earth

Halley's Comet was predicted to reach its farthest point from the sun on Dec. 9, beginning a 38-year journey toward Earth that culminates in 2061.

After zooming away from Earth for nearly 40 years, Halley's Comet has finally turned tail and started heading back our way — setting the stage for a spectacular close-up in 2061.

On Saturday, Dec. 9, the famous comet was predicted to reach its farthest point from the sun , also known as its aphelion, at a distance of about 35 astronomical units (AU) — or about 35 times the distance between Earth and the sun, according to NASA . That puts the comet well beyond the orbit of Neptune, and nearly in the front yard of Pluto , which orbits at about 39 AU.

In a sense, this is the midway point of Halley's routine, 76-year orbit of the sun. For the last 38 years or so, the comet has moved millions of miles farther away from us every day; now, it will spend the next 38 years moving closer.

Related: 'Planet killer' asteroids are hiding in the sun's glare. Can we stop them in time?

Halley's last close approach of the sun (or its perihelion) was on Feb. 9, 1986, when it swooped to within 54.6 million miles (87.8 million km) of the sun, according to NASA; that's about 0.58 AU from the our home star, or just interior to the orbit of Venus. Astronomers haven't seen the comet at all since 2003 , after which it became too small and dim to see. 

Comets are balls of ice and dust that orbit the sun. These celestial objects are best known for their "tails," which form when solar radiation vaporizes ice particles in the comet's body, causing gas and dust to stream behind it.

Halley's Comet was the first comet predicted to return to Earth's skies. Astronomer Edmond Halley observed the comet in 1682 without knowing exactly what it was — he first dubbed it a "hairy star," according to skywatching news site EarthSky .

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Halley compared his observations to similar sightings reported in 1531 and 1607, and he hypothesized that all three sightings were repeat appearances of the same object. Halley predicted the object would appear again in 1758 — and so it did. Halley, who died in 1742, never got to confirm his predictions, although future scholars eventually named the comet in his honor.

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Halley's Comet makes its next close approach to the sun on July 28, 2061. Until then, you can experience the "hairy star's" shimmering legacy twice a year, during two meteor showers associated with icy debris left behind by the comet on prior trips across Earth's orbit. The Delta Aquariid meteor shower in May and the Orionid meteor shower in October both occur when old debris from Halley's Comet falls through Earth's atmosphere, burning up as "shooting stars." Editor's note: This article was updated on Dec. 11 to reflect that the comet has reached its aphelion and is now headed toward the inner solar system again.

Brandon is the space/physics editor at Live Science. His writing has appeared in The Washington Post, Reader's Digest, CBS.com, the Richard Dawkins Foundation website and other outlets. He holds a bachelor's degree in creative writing from the University of Arizona, with minors in journalism and media arts. He enjoys writing most about space, geoscience and the mysteries of the universe.

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Apocalypse postponed: how Earth survived Halley's comet in 1910

In case you haven't heard, the world ends tomorrow. Friday 21 December 2012 is the date that the Maya Long Count Calendar reads " thirteen b'aktun ". This has somehow snowballed into a full-blown doomsday prophecy with the apocalypse involving –  against all verifiable evidence – black holes, solar flares, previously unknown planets, and comets targeting Earth.

Comets have long been thought harbingers of disaster. As recently as 1910, Halley's comet was the subject of great public concern. Although it has nothing to do with the present Mayan Apocalypse, the parallels are interesting.

Back then, in an age when telescopes were unable to track the comet around its 76-year orbit, the search for its return was reported by the newspapers. The anticipation of a spectacular view, as a result of the comet's calculated close passage to Earth, turned to concern when astronomers realised that the Earth would pass through the comet's 25-million-kilometre-long tail.

Then things got worse. Much worse.

The technique of spectroscopy, in which light is analysed to show the composition of celestial objects, was brought to bear on Halley and on 7 February 1910 the Yerkes Observatory announced the discovery of cyanogen, a deadly poison, in the comet's tail.

The New York Times reported that the French astronomer and author Camille Flammarion believed that the cyanogen "would impregnate the atmosphere and possibly snuff out all life on the planet."

In a somewhat misguided attempt to allay fears, the director of the Cambridge Observatory, Sir Robert S Ball, quoted English astronomy doyen Sir John Herschel as saying that the whole comet could be squeezed into a suitcase.

Herschel was probably seeking to emphasise the ephemeral nature of the comet's gaseous tail, nevertheless it produced a tongue-in-cheek rejoinder in The New York Times that he was clearly talking nonsense because he had failed to state who would do the packing. "Experience teaches that mighty little can be packed in a suitcase by any man. It takes a woman to pack one properly," said the paper. The light-hearted piece concluded that it would be better to leave the comet where it is in order for everyone to feel safer.

It didn't work. Concern among the public grew in the weeks leading to the Earth's 19 May passage through the comet's tail. Charlatans sold comet pills that would supposedly protect against the effects of the poison. Churches held all night prayer vigils, and doomsayers wrote to the Royal Greenwich Observatory, England, to say that the comet would cause massive tides across the Americas as the Pacific emptied itself into the Atlantic .

(As a rule of thumb, anything that invokes gravity or tides to end the world or trigger volcanoes and earthquakes is bound to be wrong because gravity is the weakest force of nature. Remember how a magnet picks up an iron tack – that's the small magnet defeating the entire Earth's gravity.)

As dawn arrived on 20 May 1910, the world had not ended. Oceans had not emptied, people had not choked, though tragically 16-year-old Amy Hopkins lost her life falling from a roof , while watching for the comet with friends.

With doomsday averted for all but Amy's parents, stories of Halley's comet disappeared from the papers and things carried on as normal. Now, a century later, the mania is back for the Mayan Apocalypse.

People around the world are stockpiling food and survival equipment . In China, "doomsday rumour-mongers" are reportedly being arrested . It is a sad state of affairs that we have clearly not learned from the folly of 1910.

Although Halley's comet did not trigger an apocalypse, it does have something important to teach us about prophecy.

Edmond Halley astonished the 18th century world by predicting the return of the comet that now bears his name. He used Newton's law of gravity to achieve the feat. At a stroke, he proved that science could do what astrologers and prophets had always claimed but failed to achieve: to predict a future occurrence.

The ability to predict future events is a powerful property of "classical physics". It relies on measurement and the clockwork rigidity of certain physical laws. Without these, prediction is impossible – even within a science.

So if someone claims to have made a prediction, or even a prophecy, ask what exactly has been measured? What exactly has been calculated? What exactly has been predicted? If the answer to any of these is effectively "not sure" or "nothing", then disbelieve it.

The Mayans made no prediction that the world will end on 21 December 2012, but science tells us with some certainty that Halley's comet will be back in 2061. Stuart Clark is the author of The Sensorium of God (Polygon) a novel featuring Edmond Halley

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Halley is often called the most famous comet because it marked the first time astronomers understood comets could be repeat visitors to our night skies. Astronomers have now linked the comet's appearances to observations dating back more than 2,000 years.

Halley was last seen in Earth's skies in 1986 and was met in space by an international fleet of spacecraft. It will return in 2061 on its regular 76-year journey around the Sun.

The History of Halley's Comet

Until the time of English astronomer Edmond Halley (1656-1742), comets were believed to make only one pass through the solar system.

But in 1705, Halley used Isaac Newton's theories of gravitation and planetary motions to compute the orbits of several comets. Halley found the similarities in the orbits of bright comets reported in 1531, 1607, and 1682 and he suggested that the trio was actually a single comet making return trips. Halley correctly predicted the comet would return in 1758. History's first known "periodic" comet was later named in his honor.

The comet has since been connected to ancient observations going back more than 2,000 years. It is featured in the famous Bayeux tapestry, which chronicles the Battle of Hastings in 1066.

In 1986, an international fleet spacecraft met the comet for an unprecedented study from a variety of vantage points. The science fleet included Japan's Suisei and Sakigake spacecraft, the Soviet Union's Vega 1 and Vega 2 (repurposed after a successful Venus mission), the international ISEE-3 (ICE) spacecraft, and the European Space Agency's Giotto. NASA's Pioneer 7 and Pioneer 12 also contributed to the bounty of science data collected.

Halley's Connection to Meteor Showers

Each time Halley returns to the inner solar system its nucleus sprays ice and rock into space. This debris stream results in two weak meteor showers each year: the Eta Aquarids in May and the Orionids in October.

Halley's dimensions are about 9.3 by 5 miles (15 kilometers by 8 kilometers). It is one of the darkest, or least reflective, objects in the solar system. It has an albedo of 0.03, which means that it reflects only 3% of the light that falls on it.

Comet Halley moves backward (opposite to Earth's motion) around the Sun in a plane tilted 18 degrees to that of the Earth's orbit. Halley's backward, or retrograde, motion is unusual among short-period comets, as its greatest distance from the Sun (aphelion) is beyond the orbit of Neptune.

Halley's orbit period is, on average, 76 Earth years. This corresponds to an orbital circumference around the Sun of about 7.6 billion miles (12.2 billion kilometers). The period varies from appearance to appearance because of the gravitational effects of the planets. Measured from one perihelion passage to the next, Halley's period has been as short as 74.42 years (1835-1910) and as long as 79.25 years (451-530).

The comet's closest approach to Earth occurred in 837, at a distance of 0.033 AU (3.07 million miles or 4.94 million kilometers). At that time, April 10, 837, Halley reached a total apparent brightness of about magnitude -3.5, nearly that of Venus at greatest brilliance. The light of Halley was spread over an extended area, however, so its surface brightness was less than that of Venus.

During its 1986 appearance, Halley's nearest approach to Earth occurred on the outbound leg of the trip at a distance of 0.42 AU (39 million miles or 63 million kilometers). It was slightly brighter than the north star Polaris but again spread over a much larger area than a point-like star.

At aphelion in 1948, Halley was 35.25 AU (3.28 billion miles or 5.27 billion kilometers) from the Sun, well beyond the distance of Neptune. The comet was moving 0.91 kilometers per second (2,000 mph). At perihelion on Feb. 9, 1986, Halley was only 0.5871 AU (87.8 million km: 54.6 million miles) from the Sun, well inside the orbit of Venus. Halley was moving at 122,000 mph (54.55 kilometers per second).

With each orbit around the Sun, a comet the size of Halley loses an estimated 3 to 10 feet (1 to 3 meters) of material from the surface of its nucleus. Thus, as the comet ages, it eventually dims in appearance and may lose all the ices in its nucleus. The tails disappear at that stage, and the comet finally evolves into a dark mass of rocky material or perhaps dissipates into dust.

Scientists calculate that an average periodic comet lives to complete about 1,000 trips around the Sun. Halley has been in its present orbit for at least 16,000 years, but it has shown no obvious signs of aging in its recorded appearances.

How This Comet Got Its Name

Comets are usually named for their discoverer(s) or for the name of the observatory or telescope used in the discovery. Since Halley correctly predicted the return of this comet – the first such prediction – it is named to honor him. The letter "P" indicates that Halley is a "periodic" comet. Periodic comets have an orbital period of less than 200 years.

Quick Facts

Length of Day 2.2 Earth Days

Length of Year 76.1 Earth years

Diameter 6.8 miles miles | 11 kilometers

Comet Type Short-Period (less than 200-year orbit)

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Halley's Comet has begun its long trek back toward Earth

Mark your diary for 2061 – if you're over the disappointment of 1986's fuzzy blob.

Halley's Comet, officially 1P/Halley, has begun its long journey back towards Earth after making it to aphelion – the point in its orbit farthest from the Sun – on December 9.

For Halley, that point is so far away, it extends past the orbit of Neptune.

The famous comet is slated to sling back by Earth in the year 2061. Its last visit was in 1986, when it was met with much fanfare but disappointed many – its appearance was not the imagined blazing celestial fireball, but more of a dim smudge in the sky that could not be seen with the naked eye.

But while Halley disappointed, six spacecraft from four space agencies were able to observe its structure.

• James Webb, Halley's Comet may be set for cosmic dust-up
• Eta Aquariid meteor shower peaks this weekend, and will be one for the ages
• That's gotta hurt: NASA suffers attack of the lame Orionids
• NASA's OSIRIS-REx spacecraft is returning with its first-ever asteroid sample

Named after its discoverer, astronomer Edmond Halley, 1P/Halley completes an orbit of the Sun roughly every 75 to 79 years. This length of time earns it a designation as a "short-period" comet – which means it orbits the sun in less than 200 years.

Its short period and predictable behavior is what led to its discovery. Prior to Halley, it was not known that comets were on an orbital path that would see them return. The astronomer predicted its reappearance in 1705 based on recorded observations in intervals going back at least 2,000 years.

A sighting of 1P/Halley was even woven into the Bayeaux Tapestry – the 70-meter cloth that depicts the Battle of Hastings in 1066 and portrays the comet as large and bright.

As 1P/Halley approaches again, the possibility of a crewed mission that visits the comet – the subject of 1986 Sci-Fi classic Heart of Comet – will doubtless be debated.

Humanity has already landed a bot on a comet - the ESA's Rosetta probe reached 67P/Churyumov-Gerasimenko in 2014 before its Philae lander touched down.

We're quite good at this visiting tiny distant rocks thing now. NASA's OSIRIS-REx even took a sample from asteroid Bennu and returned it to Earth in 2023. Japan's space program has chalked up two asteroid sample return missions. Maybe by 2061 we'll be able to pay the famous comet a visit, too?

Scientists believe Halley has been around at least 16,000 years and has displayed little signs of aging. An average periodic comet completes around 1,000 trips around the Sun, according to NASA.

There's more to see from Earth that just the comet itself. Every year cometary dust from 1P/Halley creates two meteor showers: the Eta Aquariid meteor shower in May and Orionid in October.

This year's Eta Aquarii was particularly intense – with between 120 and 160 meteors visible per hour. An average meteor shower displays between 50 and 60 per hour. ®

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Photos of Halley's Comet Through History

Halley's comet in 1986.

An image of Halley's Comet taken in 1986.

Halley's Comet from Table Mountain Observatory

This photograph of Halley's Comet was taken January 13,1986, by James W. Young, resident astronomer of JPL's Table Mountain Observatory in the San Bernardino Mountains, using the 24-inch reflective telescope. Streaks caused by the exposure time are stars in the constellation Aquarius. Visible in the photo are the coma of gases and about 725,000 kilometers (450,000 miles) of the charged ion tail.

Halley's Comet in 1910

Halley's Comet as photographed May 13, 1910, by a wide-angle camera at Lowell Observatory, Flagstaff, Ariz., during the comet's last appearance. A streak across the comet near the coma is a meteor trail, and not a scratch on the negative. Streaks at the bottom right are the city lights of Flagstaff Bright spot above the city lights is the planet Venus.

Halley's Comet Seen by Europe's Giotto Probe

This view of comet Halley's nucleus was obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft, as it passed within 600 km of the comet nucleus on March 13, 1986.

Giotto at Halley

The Giotto space probe, launched in 1985 on an Ariane 1 V14 launcher, brushed past the hidden nucleus of Halley's comet in 1986.

Approaching Halley's Nucleus

Giotto approaching the nucleus of Halley's Comet at 68km/s, protected by its white dust shield.

Two Views of the Galaxy

These two views show the position of Halley's comet and six planets on Jan. 7, 1984. At that time, Halley was about 800 million miles from the sun, traveling at an 18-degree tilt with respect to the plane of the solar system.

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Halley's Comet from Diamond Head, Hawaii

These images show Comet Halley as it was photographed on various dates in 1910 from Diamond Head, Hawaii, by Ferdinand Ellerman. The points or short streaks are background stars.

Halley's Comet in 1985

These two photographs of Comet Halley were obtained the night of Nov. 14, 1985, by JPL astronomer Eleanor Helin. Halley was about 105 million kilometers (65 million miles) from Earth and traveling about 33 kilometers per second (74,000 mph) with respect to our planet.

The Adoration of the Magi

'The Adoration of the Magi' is a scene in a fresco cycle decorating the interior of the Scrovegni Chapel in Padua. The fresco was painted by the Florentine master Giotto di Bondone, probably in 1303 and 1304. Halley's Comet had appeared in 1301, and inspired the artist to depict the Star of Bethlehem as a fiery comet. When the European Space Agency elected to send a spacecraft to encounter the comet, the spacecraft was named after the artist. Reproduction of the painting is by the courtesy of the Comune di Padova.

Halley's Comet and Others May Be Stolen Goods

The detailed tail photograph of Halley's Comet was obtained by Jet Propulsion Laboratory astronomer Eleanor Helin with the 48-inch Schmidt telescope at Caltech's Palomar Observatory on Dec. 13, 1985.

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Explosive 'devil comet' returns for 1st time in 71 years during April 8 eclipse, NASA says

Officially named 12P/Pons-Brooks, the "devil comet" has periodic explosions.

A rare and massive comet with a devilish nickname is set to pass by Earth for the first time in 71 years and may be visible during the highly anticipated April 8 total solar eclipse , according to NASA .

Officially named comet 12P/Pons-Brooks, the cryovolcanic comet is known as the "devil comet" due to its formation of two "horns" made up of ice and gas and periodic explosions.

Comets are made up of dust, frozen gases, ice and rocks bound together following the formation of the solar system, NASA says.

MORE: What to know about the 'devil comet' expected to pass by Earth in the summer

The devil comet is heading for its next perihelion passage, when it will reach its closest point to the sun and shine the brightest, on April 21, according to NASA. The agency says this astronomical event coincides with the April 8 total solar eclipse in North America, which will shadow parts of the United States from Texas to Maine when the moon passes between the sun and the Earth.

In the abrupt absence of sunlight during totality, NASA said skywatchers will have a view of the vast sky, dark enough to observe stars, planets and perhaps 12P/Pons-Brooks as it travels through the solar system.

"Comet 12P's April 21 perihelion passage will be only two weeks after the April 8 total solar eclipse, putting the comet in planet Earth's sky along with a totally eclipsed sun," the agency said.

Continuing its route through the solar system, 12P/Pons-Brooks will make its closest approach to Earth on June 2, offering another opportunity to see the devil comet, however, its distance from the sun will make it less visible than during the eclipse, experts previously told ABC News .

Likened to Halley's comet , which has an orbit of 76 years around the sun, 12P/Pons-Brooks is a short-period comet, meaning one that has an orbital period of between 20 and 200 years. The devil comet travels on an orbital period of 71 years and was last seen in 1954.

Scientists have estimated the devil comet has a diameter of at least 17 kilometers, or 10.5 miles, according to the American Astronomical Society .

MORE: Eclipse glasses: What to know to keep your eyes safe

The comet's periodic explosions or "outbursts" make it brighter, easier to spot with telescopes and, in some cases, "something people can see from their backyard," Dr. Theodore Kareta, a postdoctoral researcher at the Lowell Observatory in Flagstaff, Arizona, previously told ABC News .

12P/Pons-Brooks experienced a major outburst in July 2023, when it suddenly became 100 times brighter, and continued to have periodic explosions on Oct. 5, Nov. 1, Nov. 14, Dec. 14 and Jan. 18, 2023, respectively, according to Space.com .

"These outbursts ... [have] brought this object from being dim enough that you can only really see it with big professional telescopes to, in a couple of cases, something people can see from their backyard," Kareta said.

"There aren't that many comets that have outbursts, these sudden increases in brightness, that are so strong, and even fewer that have them a couple of times during one orbit. It seems like Pons-Brooks ... is just really active," he continued.

MORE: Asteroid that passes nearby could hit Earth in the future, NASA says

Dr. Eliot Herman, a retired professor at the University of Arizona and an amateur astronomer who has captured images of 12P/Pons-Brooks with a remote telescope, encourages viewers to keep an eye out for the devil comet in the coming months.

"People have historically looked up at the sky since people first became self-aware, and being amazed at the events that occur above us is something that goes back far before civilization," he previously told ABC News. "The events in the sky touches all, I think, in a very historic way. The universe is a big place and a lot of amazing things are occurring all around us. It's worth getting out there and just looking at it and be awestruck."

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"Devil comet" visible in night sky now won't swing by Earth again for decades

By Ashley Strickland

March 21, 2024 / 1:23 PM PDT / CBS/CNN

An unusual horned comet notable for a series of recent outbursts will be visible in the night sky for the remainder of March — and astronomers expect the so-called devil comet to make a rare appearance during the  total solar eclipse on April 8 .

Exactly why the dynamic comet takes on a shape that has drawn comparisons to the Millennium Falcon spacecraft from the "Star Wars" films when explosively active is still an enigma to scientists. But the celestial object only completes one orbit around the sun about every 71 years, similar to Halley's Comet, which make the odds of observing it for close study a once-in-a-lifetime opportunity.

Given that the comet won't pass by Earth again for decades, collective observations by astronomers could provide key insights into the true nature and behavior of Pons-Brooks.

Officially known as Comet 12P/Pons-Brooks, the celestial object will make its closest pass of the sun on April 21, coming within 74.4 million miles (119.7 million kilometers)   of our star. The comet will then make its closest pass of Earth on June 2, but it will be 139.4 million miles (224.4 million kilometers) away from our planet and won't pose a risk.

For those in the Northern Hemisphere, the last 10 days of March will offer the best view, according to Dr. Paul Chodas, manager of the Center for Near-Earth Object Studies, and Davide Farnocchia, navigation engineer, at NASA's Jet Propulsion Laboratory in Pasadena, California.

"The comet will brighten a bit as it gets closer to the sun, and it should be visible to the naked eye low in the west about an hour after sunset," according to a joint email from Chodas and Farnocchia. "You should go to a location away from city lights and with an unobstructed view of the western horizon. It would be advisable to use a pair of binoculars, since the comet may be hard to locate without them."

After April 2, the comet is on track to move into the daytime sky and won't be visible to sky-gazers at night — but it will be visible when the moon's shadow temporarily blocks the sun's face from view on April 8.

"The comet would be located about 25 degrees away from the eclipsed sun," Chodas and Farnocchia said via email. "The comet should be fairly easy to find during the total solar eclipse, as well as a number of planets, but the main focus during those 4 minutes should be on the  eclipse  itself!"

After the comet's closest approach to the sun, known as perihelion, in late April the celestial body will shift to the southern night sky and only be visible to those in the Southern Hemisphere.

Two prolific discoverers, Jean-Louis Pons and William Robert Brooks, independently observed the devil comet for the first time in 1812. But the comet has likely made many trips around the sun over thousands of years, long before astronomers thought of comets as anything other than "something weird in the atmosphere," said Dr. Dave Schleicher, astronomer at Lowell Observatory in Arizona.

Astronomers estimate the massive comet to be between 6.2 to 12.4 miles (10 to 20 kilometers) in diameter, said astronomer Dr. Teddy Kareta, a postdoctoral associate at Lowell Observatory.

The rare visitor has a green appearance typical of most comets because they contain diatomic carbon molecules that absorb sunlight and emit a color that appears green from our perspective, Schleicher said.

A series of cosmic outbursts

Pons-Brooks recently captured the attention of astronomers after exhibiting intriguing behavior that caused the comet to have a horned appearance and soar through our solar system.

The comet has experienced a number of outbursts during the past eight months, causing it to eject gas and dust. While such releases are not uncommon in comets and a crescent or Pac-Man shape has been observed in other ones, it's difficult to tell what is normal for Pons-Brooks.

"I would say it's somewhat unusual in the number of outbursts it's been having," Schleicher said. "On the other hand, it's not like you have good records from the past to really let you know what is typical. And I suspect given the fairly large number of outbursts that have happened over the last eight months, that this is very clearly a usual occurrence for Pons-Brooks."

Comets are chunks of dust, rock and ice, essentially frozen remnants from the formation of the solar system. They also contain frozen elements such as carbon dioxide and carbon monoxide.

Comets heat up and brighten as they approach the sun, and some of the frozen gases stored in comets don't need to warm up much before they begin to turn into vapor, Schleicher said.

"We think the ultimate driver, of course, is heating from the sun," he said. "The comet is coming in; it's been sitting out in a deep freeze for years. The heat is going to be working its way from the surface down to wherever that carbon dioxide or carbon monoxide ice is located."

Astronomers suspect Pons-Brooks outbursts have occurred over the course of repeated events as heat vaporizes material inside the comet, which causes pressure to build up and break through the surface. While an explosion of gas wouldn't be visible in telescopes, the dust it kicks up would create the kind of events observed from Pons-Brooks, Schleicher said.

Scientists have traced the jets of material observed releasing from the comet during its outburst to two source regions on its surface. Astronomers are puzzled as to why "the whole surface isn't going off like mad," Schleicher said.

The observations imply that ice has crusted over the majority of the surface, or the ice has been vaporized away, leaving only dirt behind, but astronomers are "not quite sure which of those mechanisms runs the show," he said.

What we can learn from comets

An overlapping series of events   likely   has contributed to Pons-Brooks' distinctive look, but it could also be due to our perspective of the comet, Kareta said.

"These are three-dimensional objects," Kareta said. "When we take images of the night sky, we're taking them in a limited range of colors all flattened down in two dimensions. This will make things that might make perfect sense to you, if you're able to go up and walk around and see it in a couple of different perspectives, look much more complicated than they really are."

Astronomers are observing Pons-Brooks in the hopes of uncovering more details about its rotation rate, or the rate at which comets spin as they move through space. Pons-Brooks has a rotation period of 57 hours, which is longer than expected, and astronomers want to know if the jets of material releasing from the comet are speeding it up or slowing it down.

But Schleicher recommends keeping an eye out for the comet now rather than during the eclipse.

"In all my years, I've seen a lot of comets. I've only seen two total eclipses, and this will be No. 3. The first one I saw was back in 1991, from Baja. And that was just extraordinary. I remember realizing, no wonder this is considered the most magnificent sight in the heavens that any person on Earth can see. Get onto the path and see it in totality. You don't understand it until you've seen one."

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‘Devil comet’ visible in night sky now won’t swing by Earth again for decades

Sign up for CNN’s Wonder Theory science newsletter.  Explore the universe with news on fascinating discoveries, scientific advancements and more .

An unusual horned comet notable for a series of recent outbursts will be visible in the night sky for the remainder of March — and astronomers expect the so-called devil comet to make a rare appearance during the total solar eclipse on April 8 .

Exactly why the dynamic comet takes on a shape that has drawn comparisons to the Millennium Falcon spacecraft from the “Star Wars” films when explosively active is still an enigma to scientists. But the celestial object only completes one orbit around the sun about every 71 years, similar to Halley’s Comet, which make the odds of observing it for close study a once-in-a-lifetime opportunity.

Given that the comet won’t pass by Earth again for decades, collective observations by astronomers could provide key insights into the true nature and behavior of Pons-Brooks.

Officially known as Comet 12P/Pons-Brooks, the celestial object will make its closest pass of the sun on April 21, coming within 74.4 million miles (119.7 million kilometers) of our star. The comet will then make its closest pass of Earth on June 2, but it will be 139.4 million miles (224.4 million kilometers) away from our planet and won’t pose a risk.

For those in the Northern Hemisphere, the last 10 days of March will offer the best view, according to Dr. Paul Chodas, manager of the Center for Near-Earth Object Studies, and Davide Farnocchia, navigation engineer, at NASA’s Jet Propulsion Laboratory in Pasadena, California.

“The comet will brighten a bit as it gets closer to the sun, and it should be visible to the naked eye low in the west about an hour after sunset,” according to a joint email from Chodas and Farnocchia. “You should go to a location away from city lights and with an unobstructed view of the western horizon. It would be advisable to use a pair of binoculars, since the comet may be hard to locate without them.”

After April 2, the comet is on track to move into the daytime sky and won’t be visible to sky-gazers at night — but it will be visible when the moon’s shadow temporarily blocks the sun’s face from view on April 8.

“The comet would be located about 25 degrees away from the eclipsed sun,” Chodas and Farnocchia said via email. “The comet should be fairly easy to find during the total solar eclipse, as well as a number of planets, but the main focus during those 4 minutes should be on the eclipse itself!”

After the comet’s closest approach to the sun, known as perihelion, in late April the celestial body will shift to the southern night sky and only be visible to those in the Southern Hemisphere.

Two prolific discoverers, Jean-Louis Pons and William Robert Brooks, independently observed the devil comet for the first time in 1812. But the comet has likely made many trips around the sun over thousands of years, long before astronomers thought of comets as anything other than “something weird in the atmosphere,” said Dr. Dave Schleicher, astronomer at Lowell Observatory in Arizona.

Astronomers estimate the massive comet to be between 6.2 to 12.4 miles (10 to 20 kilometers) in diameter, said astronomer Dr. Teddy Kareta, a postdoctoral associate at Lowell Observatory.

The rare visitor has a green appearance typical of most comets because they contain diatomic carbon molecules that absorb sunlight and emit a color that appears green from our perspective, Schleicher said.

A series of cosmic outbursts

Pons-Brooks recently captured the attention of astronomers after exhibiting intriguing behavior that caused the comet to have a horned appearance and soar through our solar system.

The comet has experienced a number of outbursts during the past eight months, causing it to eject gas and dust. While such releases are not uncommon in comets and a crescent or Pac-Man shape has been observed in other ones, it’s difficult to tell what is normal for Pons-Brooks.

“I would say it’s somewhat unusual in the number of outbursts it’s been having,” Schleicher said. “On the other hand, it’s not like you have good records from the past to really let you know what is typical. And I suspect given the fairly large number of outbursts that have happened over the last eight months, that this is very clearly a usual occurrence for Pons-Brooks.”

Comets are chunks of dust, rock and ice, essentially frozen remnants from the formation of the solar system. They also contain frozen elements such as carbon dioxide and carbon monoxide.

Comets heat up and brighten as they approach the sun, and some of the frozen gases stored in comets don’t need to warm up much before they begin to turn into vapor, Schleicher said.

“We think the ultimate driver, of course, is heating from the sun,” he said. “The comet is coming in; it’s been sitting out in a deep freeze for years. The heat is going to be working its way from the surface down to wherever that carbon dioxide or carbon monoxide ice is located.”

Astronomers suspect Pons-Brooks outbursts have occurred over the course of repeated events as heat vaporizes material inside the comet, which causes pressure to build up and break through the surface. While an explosion of gas wouldn’t be visible in telescopes, the dust it kicks up would create the kind of events observed from Pons-Brooks, Schleicher said.

Scientists have traced the jets of material observed releasing from the comet during its outburst to two source regions on its surface. Astronomers are puzzled as to why “the whole surface isn’t going off like mad,” Schleicher said.

The observations imply that ice has crusted over the majority of the surface, or the ice has been vaporized away, leaving only dirt behind, but astronomers are “not quite sure which of those mechanisms runs the show,” he said.

What we can learn from comets

An overlapping series of events likely has contributed to Pons-Brooks’ distinctive look, but it could also be due to our perspective of the comet, Kareta said.

“These are three-dimensional objects,” Kareta said. “When we take images of the night sky, we’re taking them in a limited range of colors all flattened down in two dimensions. This will make things that might make perfect sense to you, if you’re able to go up and walk around and see it in a couple of different perspectives, look much more complicated than they really are.”

Astronomers are observing Pons-Brooks in the hopes of uncovering more details about its rotation rate, or the rate at which comets spin as they move through space. Pons-Brooks has a rotation period of 57 hours, which is longer than expected, and astronomers want to know if the jets of material releasing from the comet are speeding it up or slowing it down.

But Schleicher recommends keeping an eye out for the comet now rather than during the eclipse.

“In all my years, I’ve seen a lot of comets. I’ve only seen two total eclipses, and this will be No. 3. The first one I saw was back in 1991, from Baja. And that was just extraordinary. I remember realizing, no wonder this is considered the most magnificent sight in the heavens that any person on Earth can see. Get onto the path and see it in totality. You don’t understand it until you’ve seen one.”

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