The romance of the universe will be captured: In 2061, we may see Halley's Comet again

Comet McNaught in the Pacific Ocean. This image was taken at Paranal Observatory in January 2007. ESO/Sebastian Deiries

Comet, commonly known as "broom star", is a celestial body orbiting the sun. So far, 1,600 comets have been discovered, but only a few can be seen with the naked eye. Halley's Comet can be regarded as a popular one among many comets. One of the reasons is that it has returned to the perihelion many times with a period of about 74 to 75 Earth years, which is close to the average human life span. In addition, its return in the early 20th century caused a great sensation, so people have great expectations and hope to see its heroic appearance in their lifetime.

Halley's Comet, officially known as 1P/Halley, is a famous short-period comet that can be observed from Earth every 75-76 years. It is also the only short-period comet that can be seen directly from Earth with the naked eye, and a person may experience its visit twice in their lifetime. Other comets that can be observed with the naked eye may be more spectacular and beautiful, but they may only appear once every thousands of years.

Edmond Halley, born on November 8, 1656, was a British astronomer, geographer, mathematician, meteorologist and physicist, and was a professor of geometry at Oxford University.

In 1695, Edmond Halley, who was already a secretary of the Royal Society, began to concentrate on studying comets. He selected 24 comets from the comet records from 1337 to 1698 and spent a year calculating their orbits. He found that the orbits of the three comets that appeared in 1531, 1607 and 1682 looked exactly the same. Although there was a one-year difference in the time of passing the perihelion, it could be explained as being caused by the gravitational perturbation of Jupiter or Saturn. An idea flashed through his mind quickly: these three comets might be the three returns of the same comet. But Halley did not draw this conclusion immediately, but searched forward tirelessly and found that there were records of great comets in history in 1456, 1378, 1301, 1245, and all the way to 1066.

Halley was very interested in observing and studying comets. After a lot of observations, studies and calculations, he boldly predicted that the comet that appeared in 1682 would return again in late 1758 or early 1759. At this time, Halley was nearly 50 years old, and it would take another 50 years to know whether his prediction was correct. He realized that he could not see the comet return again, so he said in a humorous and regretful tone: If the comet did return in 1758 according to my prediction, fair descendants would probably not refuse to admit that it was first discovered by an Englishman.

More than 10 years after Halley's death, in early 1758, Messier of the French Observatory began to observe, hoping to be the first person to confirm the return of a comet. On January 21, 1759, he finally found the comet. Unfortunately, the honor of being the first to observe the return of a comet did not belong to him. It turned out that on Christmas Eve in 1758, a farmer near Dresden, Germany, who was an astronomy enthusiast, had already spotted the return of a comet.

Halley's prediction in the early 18th century was finally confirmed after more than half a century, which was an amazing achievement in the history of astronomy. In order to commemorate him, later generations named this comet "Halley's Comet".

* In addition to his achievements in astronomy, in 1693, Halley used the death records classified by age in the city of Brislough, Germany, from 1687 to 1691, to calculate the number of deaths and births classified by age and gender, compiled three tables, and published a famous paper in the Philosophical Transactions of the Royal Society of London - "Estimates of Human Mortality from the Birth and Death Lists of Brislough", namely Halley's Life Tables, which laid the foundation for the calculation of life insurance and annuities. Many years later, some insurance companies began to calculate insurance premiums based on age and life expectancy according to Halley's method.

Halley's Comet commemorative stamps issued by countries around the world

Halley's Comet has an orbital period of 76 years, a perihelion distance of 88 million kilometers (0.59 AU), an aphelion distance of 5.3 billion kilometers (35.31 AU), and an orbital eccentricity of 0.967. The earliest and most complete records of Halley's Comet are all in China; according to research: from the seventh year of Emperor Qin Shihuang (240 BC) to the second year of Emperor Xuantong of the Qing Dynasty (1910), there were 29 records, which are consistent with the calculation results. There are records about it in "Spring and Autumn Annals" and "Huainanzi". The number of times and the details of the records are not available in other countries.

When Halley's Comet returned in 1910, the results calculated at that time showed that after passing the perihelion, the tail of Halley's Comet would sweep across the Earth. Some newspapers deliberately exaggerated the horror, saying that there was poisonous gas in the tail (spectral analysis of Halley's Comet found that the tail of the comet contained cyanide) that would penetrate into the atmosphere and poison most people on Earth. This caused extreme panic among people, and there were even reports that some people in Central and Eastern Europe committed suicide because of this.

According to calculations, Halley's Comet will reach its aphelion on December 9, 2023. After that, this comet of the century will embark on its homeward journey again, and will reach its perihelion again in 2061 and return to people's sight.

In addition, the return of Halley's Comet also left us with two major astronomical landscapes - the Orionid meteor shower and the Eta Aquarid meteor shower. The parent bodies of these two meteor showers both come from Halley's Comet.

The Orionids occur from October to early November, with the peak occurring between October 21 and 22, with about 25 meteors per hour observed from the radiant point near the edge of Gemini in Orion. The Eta Aquarids, with the radiant point near Aquarius, occurs from April 19 to May 28 each year, reaching its climax on May 5.

During its journey through the vast universe, Halley's Comet continuously ejects dust and gas. Since its last return, Halley's Comet has lost a total of 150 million tons of material, and the diameter of its nucleus has shrunk by 4 to 5 meters. Therefore, Halley's Comet's journey through the solar system is not a leisurely stroll. Every time it comes to the sun, it will be peeled off a layer of skin. At this rate, it can still circle the sun 2,000 to 3,000 times, and its lifespan may not reach 1 million years. This kind of material loss that has no return will lead to the demise of Halley's Comet in the distant future.