Halley’s Comet – What is it, when was it discovered and when will it come back

We explain what is the Halley’s Comet, its characteristics, origin and discovery. We also tell you when will it come close to Earth

What is Halley’s Comet?

Known officially as 1P / Halley and popularly as Halley’s Comet, is a large, bright comet, orbiting our Sun every 75 years approximately (between 74 and 79 years), that is to say, it has a short period. It is the only one of its kind that can be seen from the surface of the Earth, making it an extremely popular astronomical phenomenon.

The Halley has an irregular orbit around the Solar System. It is one of the best-known astronomical objects that come from the Oort Cloud, a spherical conglomeration of trans-Neptunian objects.

Its irregularity is due to the fact that its orbit is distorted by the gravity of the planets (especially the outer giants) of the Solar System. It is also due to its changing mass, as the comet loses tons of frozen water with each step around the Sun.

This comet It owes its name to the British astronomer Edmund Halley, who in 1682 was the first to observe it and detail it scientifically. However, Halley’s Comet had been observed and reported by various cultures since ancient times.

Origin of Halley’s Comet

The various comets that cross our solar system have two possible origins: the Kuiper belt, a collection of icy astronomical debris located about 50 astronomical units (AU) from the Sun, beyond the orbit of Neptune; or the Oort cloud, a set of icy bodies that is still a hundred times further away, at the very edges of the Solar System.

Although usually short period comets come from the Kuiper Belt. However, the case of the Halley is strange, since was born in the farthest body of the Oort cloud, as with other long-period comets, such as Hale-Bopp, whose orbit takes thousands of years.

This is because it was initially a long-cycle comet, which was captured in the gravity of the planets of the Solar System, especially that of Venus.

History and discovery

Although the comet was already known, Edmund Halley was able to calculate and predict its orbit.

Comet Halley has been observed by mankind since time immemorial. It is estimated that the year 239 a. C. was the first record of his passage. That is why it is not accurate to speak of its discovery in the seventeenth century. Nevertheless, his scientific discovery is attributed to Edmund Halley, who was also the first to calculate its orbit in 1705.

In fact, it is known that in 1456 the comet had been observed by the German astronomer and mathematician Johann Müller Regiomontano; in 1531 by the German humanist Petrus Arpianus; and in 1607 by Johannes Kepler in Prague.

Thanks to all these documents Halley was able to deduce that the comet’s cycle repeated every 76 years., thus predicting its appearance for 1757. A fairly accurate prediction, since the comet appeared on December 25, 1759, sixteen years after Halley’s death.

Since then the comet has haunted our planet in 1835, 1910 and 1986.

Halley’s Comet Study

The Halley Study was a recurring theme for medieval Chinese, Babylonian and European astronomers along the history. It was associated with cyclical rites, with changes of era, and it is even thought that this comet could have been the so-called Star of Bethlehem, which according to biblical mythology led the Three Wise Men to the birth of Jesus Christ.

The Halley is also the first comet to be observed from outside the atmosphere and studied in high detail by various space probes, such as the Vega 1 and 2, the Giotto, the Suisei (PLANET-A), the Sakigake and the ISEE-3 / ICE.

This set of space probes is popularly known as Halley’s Navy (Halley’s Navy) and to them we owe our extensive knowledge of the comet.

Characteristics of Halley’s Comet

The Halley is composed of a relatively small kernel, shaped like a peanut or peanut, 15km long and 8km wide and high. It has a low mass, 2.2 × 10¹⁴ kg and a density of 0.6 g / cm³. It reflects only 4% of the light received, more or less the same as coal, so it is a black body, although from Earth it looks white and bright.

What’s more, has a coma or hair (gas cloud) that extends over millions of kilometers in the space. Said gas is emitted when the Sun’s energy heats its surface, and is composed of 80% water vapor, 17% carbon monoxide and between 3 and 4% carbon dioxide, with eventual traces of hydrocarbons.

Halley’s scientific observation coincided with the predictions of the American astronomer Fred Lawrence Whipple, who claimed in 1950 that comets were “dirty snowballs.”

When will Halley’s Comet pass again?

The orbit of Halley’s Comet, as we said, is irregular and cannot be predicted with much accuracy, but considering that the last time it passed Earth was in 1986, the most likely date of return will be 2061.

Experts warn that, thousands of years from now, Halley’s orbit will change and be influenced by Jupiter, being able to lengthen in orbits of 300 years instead of the usual 75.