(ORDO NEWS) — Astronomy is one of the most ancient natural sciences, which people have been doing for at least 17 thousand years, as evidenced by ancient rock inscriptions.
However, a serious leap in its development occurred 2200 years ago, when the Greek astronomer Hipparchus came up with a new way to track the position of stars in the sky.
To do this, he used a newly developed coordinate system similar to longitude and latitude, with the Earth represented as the center located inside the celestial sphere.
This system is used by astronomers to this day.
But the most striking thing is that the map of the night sky he created contained amazingly accurate coordinates of the stars, despite the fact that telescopes did not exist at that time.
But how, then, did the ancient astronomer manage to calculate the position of the stars?
The oldest map of the starry sky
Many ancient Greek scientists believed that the Earth is the center of the universe, respectively, the stars and other celestial bodies, in their opinion, revolved around our planet.
But despite the fact that the geocentric model turned out to be incorrect, it did not make it possible to compile the first star catalog known to science, and to propose an optimal system for mapping objects in the sky.
It was she who was used to create a map of the Milky Way, which you can learn more about by clicking on the link.
The correct model, according to which the Earth revolves around the Sun, was proposed as early as the 3rd century BC, but most astronomers, including Hipparchus, considered it erroneous.
According to many modern scholars, Hipparchus was the greatest astronomer of antiquity, or at least the greatest known astronomer.
His star catalog is the oldest attempt known to science to document the position of a large number of objects in the night sky. And for the first time in the history of mankind, two coordinates were used for this.
An ancient map of the constellations of the starry sky – how it was found
Unfortunately, the original catalog of Hipparchus, created 2200 years ago, has been lost. We only know of its existence from the writings of later scholars such as Ptolemy, who created his own star catalog around 150 BC.
Until recently, the oldest evidence of stellar coordinates from Hipparchus was a Latin translation of a constellation poem written in the 8th century AD. The poem contains the coordinates of the stars as a kind of annotation.
But recently, scientists have discovered even earlier records indicating stellar coordinates from Hipparchus.
They are contained in the Greek version of the same poem, The Phenomenon, dated to the 5th or 6th century AD. The poem itself was originally written by the Greek poet Aratus in the 3rd century BC.
Arata’s poem “The Phenomenon” was an ancient bestseller, but Hipparchus did not like it very much.
The only work of the astronomer that has survived to this day is a criticism of Arat’s poems, since he did not accurately describe the constellations.
Therefore, Hipparchus would hardly be pleased that his name for posterity is firmly associated with the poet Arat.
The accompanying stellar coordinates were written on parchment, and subsequently erased several times for re-use.
The parchment itself is part of a library from the monastery of Saint Catherine in Egypt. The collection contains monastic writings in Syriac, as well as the ancient language of Western Asia.
Astronomical records were first discovered in 2012. Then one of the researchers at Cambridge University, Jamie Clare, noticed the Greek inscriptions under the Syriac text.
In 2017, the parchments were photographed using state-of-the-art multispectral imaging tools, clearly revealing the original text.
According to researchers in the Journal for the History of Astronomy, fragments of Arata’s poem have been found in some documents.
At the same time, the poem is accompanied by illustrations and mythological stories about the constellations. In 2021, while studying multispectral images of the poem, researchers noticed numbers that turned out to be stellar coordinates.
As it turned out, the ancient text contained the dimensions of the constellation Northern Crown, as well as the coordinates of its most distant stars.
It must be said that the coordinates of the stars from the constellation Northern Crown are only a tiny part of the work of the ancient astronomer. According to some reports, he plotted the coordinates of about 800 stars on his map.
What is the accuracy of the oldest map of the starry sky
Scientists compared the coordinates of an ancient astronomer with the data of a modern map of the starry sky.
At the same time, they took into account the precession, that is, the oscillation of the Earth around its axis during rotation (Hipparchus also discovered precession, which we talked about earlier).
As a result, it turned out that the coordinates really correspond to the positions of the stars in the Northern Crown in 130 BC, if they would be looked at from the island of Rhodes.
It is believed that it was at this time that Hipparchus worked on Rhodes and made most of his observations.
The coordinate error was no more than one degree.
For someone who worked 1,700 years before the invention of the first telescope, this is incredibly high accuracy. But how did you manage to achieve such results?
How an ancient astronomer created a map of the starry sky
At present, it is no longer possible to say exactly how Hipparchus determined the exact position of the stars in the sky. According to historians, he may have used an armillary sphere.
This is an astronomical instrument designed to determine the equatorial or ecliptic coordinates of celestial bodies.
It is a mechanical device with rotating rings, each of which represents a certain part of the celestial sphere, for example, the celestial equator (an imaginary plane extending outward from the Earth’s equator), the annual path that the Sun follows through the sky, etc.
It is possible that Hipparchus also used a diopter sight that could be attached to a rotating platform (diopter).
The diopter was a kind of surveying instrument that could be used to measure angles in surveying operations. But, theoretically, the device can also be used to measure angles in the sky.
Most likely, Hipparchus was influenced by the earlier work of the Babylonian astronomers, who measured the distances to certain constellations from the ecliptic (the annual path of the Sun).
By tracking the movements of the zodiac constellations, as well as some other constellations, the Babylonians could measure the seasons and predict astronomical events such as eclipses.
It is the combination of the Babylonian practice of measuring and predicting the movement of stars with the Greek concepts of mathematics and geometry that is considered the fundamental achievement of Hipparchus.
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