Halley comet

Halley comet . Officially named 1P/Halley, it is a large, bright comet that orbits the Sun every 76 years on average, although its orbital period can range from 74 to 79 years. It is one of the best known and brightest of the “short period” comets of the Kuiper Belt. It was last observed in 1986 near the Earth’s orbit, it is estimated that the next visit will be in the year 2061; The previous one occurred in 1910. Although there are other brighter comets, Halley is the only short cycle comet that is visible to the naked eye, so there are many references to its appearances, being the best documented.

Summary

[ disguise ]

• 1 Origin
• 2 History
• 3 Orbit
• 4 Structure and composition
• 5 Study of the comet
• 6 Meteor shower
• 7 interesting facts
• 8 Sources

Origin

Comets are supposed to have two distinct origins in our Solar System, the Kuiper Belt , an icy flat disk of stellar debris, located about 50 astronomical units (AU), and the Oort Cloud , a sphere of cometary bodies, whose inner edge is located at about 50,000 AU. Short cycle comets, with an orbit that takes less than 200 years, generally come from the Kuiper belt; while those with a long cycle, such as Hale-Bopp, whose orbit takes thousands of years, seem to come from the Oort cloud.

Halley’s Comet is unusual in that it has a short cycle, although its origin is in the Oort cloud, and not in the Kuiper belt. Its orbit indicates that it was originally a long cycle, but that it has been captured by the gravitational attraction of the gas giants, so that it has been trapped inside the Solar System . Halley’s Comet is named after [Edmond G. Halley]], who was the first to suggest that comets are a natural phenomenon of the solar system, orbiting the Sun. Edmond G. Halley suggested that there was a certain comet that he was a regular visitor, returning every 76 years, and was the same one that had been seen since 240 BC, most particularly during the years 1531, 1607, and 1682, dates in history that were recent for him. In 1682, Edmond Halley predicted that this comet would return in the year 1758, and sure enough, the comet returned in March 1759. In 1910 Halley’s Comet made a particularly bright appearance. Likewise, its appearance in 1066 was captured in a famous ancient tapestry.

More than 2000 years ago, specifically in the year 239 BC, astronomers spotted a comet in the sky, which would be observed periodically every 76 years. It was what would ultimately be the best-known comet in the sky: Halley’s Comet. Its name is due to Edmund Halley, who was the astronomer who first calculated its orbit. Thanks to his calculations and descriptions of previous sightings, he stated that in 1757 the comet that had been seen in the year 1472, 1531, 1607 and 1682 would pass near our planet again. Edmund Halley was never able to verify that it would be true, since he died 16 years earlier, and he only got his calculations wrong by one year. The last time Halley’s Comet visited us was in 1986, and it will not pass near us again until the year 2061, when it has completed a new return to its orbit, which extends from 0.6 AU (between Mercury and Venus ) and moves away to 35 AU, slightly less than the distance to the dwarf planet Pluto .

Halley’s Comet also has its oddities. In our Solar System there are two types of comets, short cycle comets and long cycle comets. The first come from the Kuiper Belt, an area located between 30 and 50 AU that we have already talked about in space science, and the second, from the Oort cloud, located at more than 50,000 AU. Halley’s Comet can boast of belonging to both groups, since calculations of its orbit indicate that it initially came from the Oort cloud, but was trapped by the gas giant bodies of the Solar System and became a short-cycle comet. On the occasion of the comet’s passage near our planet in 1986 , the European Space Agency ( ESA ) launched the Giotto mission, initially planned by NASA , but declined due to financial cuts. The Giotto probe approached just 596 kilometers from Halley’s Comet.

History

Halley comet

Comets have always aroused terror and curiosity throughout the world. Whether due to their unforeseen appearances or their spectacular sizes, they have always been related to events, generally tragic, in the history of humanity . The word comet derives from Greek and means hairy star. With few exceptions, the ancients believed that they were atmospheric phenomena . For some they were terrestrial exhalations that became incandescent upon reaching the region of fire in the sky, for others, the spirits of important figures.

As an example, the Romans believed that the great comet that appeared in 44 BC was the soul of Julius Caesar , and even in the 17th century , figures as important as Hevelio believed that they were emanations from the Earth . In fact, Halley’s Comet has been very influential in the history of humanity, but not because of its ‘magical’ effects, but because of what men believed it could do. The ancient writers attributed terrifying images to them: ‘sabers, swords, severed heads with bristling hair and beards, shining among a glow of blood, yellow or livid’, of which the historian Josephus speaks, which appeared in the year 66 BC, four years before the destruction of Jerusalem. Today we know that it was Halley’s Comet in one of its first recorded passes.

This comet has passed through perihelion 30 times since 239 BC, which is the oldest known appearance. There is no historical data for the steps of the years 391 and 315 BC. A memorable step was that of the year 837, during the reign of Louis I the Pious. A chronicler of the time, known as ‘the Astronomer’, speaks of the comet in the following terms: ‘On the Holy Days of Easter, a phenomenon that was always disastrous and had sad omens appeared in the sky . Since the emperor saw him, always attentive to these phenomena, he has not had a moment of rest. A change of reign and the death of a prince is what this phenomenon announces, he says.’ On the advice of the bishops, he dedicated himself to prayer and founded monasteries, but despite this, he died three years later.

The Emperor’s terror is understandable, since on April 11 , 837 the comet passed very close to the Earth, at only 0.0323 AU (a little more than ten times the distance of the Moon). Its tail reached 90 degrees in length, with a magnitude of -3. It is the minimum distance at which Halley has passed from our planet. Another recorded step is that of the year 1066, when [[William the Conqueror]] invaded England . The chroniclers wrote ‘the Normans, guided by a comet, invade England’. In 1301, Giotto painted it in one of his works, which is why one of the spaceships that visited him in 1986 was named Giotto. One of the most famous steps was that of the year 1456, three years after the taking of Constantinople by the Turks. Europe was still not reacting to the event when the comet appeared. According to the chroniclers of the time ‘on May 27 , 1456 the comet appeared; It was large and terrible, its tail of two signs (about 60 degrees), had a bright yellow color and looked like a waving flame.’ No one doubted that this was a divine message that predicted great disasters.

Pope Calixtus III , who participated in the general panic, conjured all the Christian princes to concentrate their forces against the Muslim invasion. For this reason he also established that the Angelus be celebrated at noon, the use of which has been perpetuated ever since in all churches. Previously, in the year 1318, John XXII had established that the Angelus be recited in the afternoon. In 1531, it was observed by Appian and Fracastor, and in 1607 by Kepler and Longomontano.

Despite the ignorance that can be seen in the previous story, not everyone thought that way. Brilliant minds like Seneca’s, he wrote 2000 years ago, ‘because we would be surprised if comets are not subject to well-determined laws, the day will come when posterity will be amazed that we have ignored things that will then seem so clear.’ This is almost prophetic. But let’s leave these stories and go to another no less interesting one, which was the prediction of the arrival of Halley’s Comet in 1759 . Edmond Halley, English astronomer, published a catalog of 24 comets in 1705. With the help of Newton’s already well-established laws, he calculated each of the orbits of these stars and noticed that those of 1531, 1607 and 1682 had almost identical orbits, and the period differences were 75 and 76 years respectively. . With this he surmised that all three were actually the same comet and predicted its return for 1758.

A phenomenon had never been expected with such expectation, since it would allow us to predict many things about the Solar System. The year passed and the comet did not arrive. An astronomer named Clariaut took matters into his own hands. Analyzing the problem, he developed much more perfected equations for the prediction of planetary perturbations on the comet, but he left the terrible task of numerical calculation to two people, the astronomer Lalande and Mrs. Hortensia Lepaute. The process took 6 months – a computer today does it in a fraction of a second. Saturn would delay the passage by 100 days, and Jupiter 518, that is, a total delay of 618 days, so they set the passage through Halley’s perihelion in mid-April 1759, with an error of more or less 1 month. The comet actually passed through the positions predicted by the calculators and on May 12, 1759 it passed through perihelion, a month later than expected.

It was undoubtedly one of the greatest astronomical feats of that century, and thus Seneca’s prophecy was confirmed. Halley had unfortunately died in 1742, and was unable to see his prediction come true. Curiously, the greatest knowledge about comets was limited to scientists, which is why, around 1910, there were thousands of suicides by people fearful of the ‘certain’ destruction of the Earth, encouraged by pseudo-scientists and the press. As we see, there are things that do not change. The 1986 pass was not glorious, as it did not pass too close, nor at a good angle. Additionally, technology made cities so illuminated that it was almost insignificant. We will have to wait until 2061 for the next visit, and we will not know exactly what it will be like.

When can it be photographed again? In the current state of technology, it can be photographed even now. For example, it has been photographed with the ESO VLT ( Very Large Telescope ) telescope on Cerro Paranal – Chile , between March 6 and 8 , 2003 , in 81 individual exposures with the 8.2 meter telescope. Combined they are like a 9 hour exposure, showing Halley’s core of magnitude 28.8. It was at that time 4080 million kilometers from Earth. As you can see the telescope guided over the comet, so the stars are seen as traces. North is up and east is on the left.

Orbit

The orbit of Halley’s Comet is very elliptical, with a focus on the Sun , its shortest distance from the Sun, the perihelion is 0.6 AU, between the orbits of Mercury and Venus , while its aphelion, the greatest distance from the Sun , is 35 AU, almost the distance of Pluto’s orbit. As a curiosity, among the objects of the Solar System, its orbit is retrograde, since it orbits in the opposite direction to the planets, with an inclination of 18º with respect to the ecliptic .

Structure and composition

The Giotto Mission provided astronomers with their first view of the structure and surface of Halley’s Comet. Its coma extends across millions of kilometers in space, although its core is relatively small, being about 15 kilometers long, 8 wide and 8 high, shaped like a peanut. The comet’s mass is quite low, about 2.2×1014 kg, with a density of about 0.6 g/cm³. Its albedo is approximately 4 percent, which indicates that only 4% of the light received is reflected, more or less, the same behavior as coal. Although it appears very bright and white when observed from Earth, Halley’s Comet is, however, a black body.

Upon entering the interior of the Solar System, and approaching perihelion, the Sun heats its surface, causing the sublimation of its matter, and passing directly from the solid to the gaseous state, emitting a large amount of volatile gas from its dark surface. The nucleus rotates every 52 hours, and on its daytime side it is much more active than on its dark side. The gas emitted is 80% composed of water vapor, 17% carbon monoxide, 3-4% carbon dioxide, and the rest are traces of hydrocarbons. The core is covered with a layer of powder that retains heat. Within this layer of dust, there are holes, some with ice, and others empty, and there are also several craters, some measuring 1 km. Diameter. As it approaches the Sun, temperatures can approach 77º C, and tons of gas are then emitted per second.

Halley is almost unique among comets in that it is both large and active, and has a regular, well-defined orbit. This makes it a relatively easy target for astronomers, although it is not the most representative of comets. Halley’s Comet will approach the Sun again in the year 2061. It has been the comet from which we have begun to understand the rest and the first to be photographed from space. Photographs from space probes show us a potato-shaped comet (8x8x16 km). The analyzes of several space probes, one month after perihelion, when the comet was at a distance from the Sun similar to that of Venus, give the following results for the composition of the gas expelled from the nucleus :

• Water 71%
• Carbon monoxide 16%
• Formaldehyde 6%
• Carbon dioxide 5%
• Methane 1%
• Ammonia 1%
• Hydrocyanuric acid 0.1%

Comet study

Halley’s comet was the first to be recognized as periodic, its orbit was first calculated by the astronomer Edmund Halley in 1705. It was previously observed in Europe in the year 1472 by the German astronomer Regiomontano, observation data show that It was first observed in 239 BC. C. In his observations, Edmund Halley verified that the characteristics of the comet coincided with those described in 1682, and also with those of 1531 (described by Petrus Apianus and 1607 (observed by Johannes Kepler in Prague). Halley concluded that they corresponded to the same celestial object, which returned every 76 years. With this, he made an estimate of the orbit, and predicted its reappearance for the year 1757. This prediction was not entirely correct, since the return was not seen until December 25, 1758 , made by the German amateur astronomer Johann Georg Palitzsch. In this case, the attraction of Jupiter and Saturn was responsible for the delay. Halley was unable to witness the return of his comet, dying in 1742.

Meteor shower

The southern hemisphere of the Earth, but especially some countries in South America, such as Argentina , were privileged witnesses of the passage of the shower of shooting stars, pieces of Halley’s Comet, whose wake once again passed close to the atmosphere. land. NASA’s Meteorite Office had reported the passage of the comet, which 25 years ago amazed the world when it was completely visible. The next time an event of this magnitude will happen will be in 51 years.

The “Eta Aquariid” meteor shower, which comes from the constellation of Aquarius, could be seen in different countries in Latin America . Shooting star showers occur every year, but those of Halley’s Comet are the most visible, due to their proximity to the planet. Last night, and for just a few moments, the world once again witnessed very bright flashes of light of variable colors. Halley’s Comet is the only short cycle comet that can be seen with the naked eye, which has always allowed it to be documented in the best way.

Interesting data

• Longest tail on record: 150 degrees, in 1910.
• Maximum approach to Earth: 4.8 million kilometers, in 837.
• Average orbital period: 76.7 years.
• It has been known to have this orbit for at least 7000 years. (until that moment it did not pass near any planet that would substantially modify its movement).
• Halley steps: -239, -164 (not observed), -86, -11, 66, 141, 218, 295, 374, 451, 530, 607, 684, 760, 837, 912, 989, 1066, 1145, 1222, 1301, 1378, 1456, 1531, 1607, 1682, 1759, 1835, 1910, 1986, 206