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Constellations in 3D. Sagittarius


Constellations are sets of stars whose grouping remind us of real or imaginary figures. As seen from the Earth, they appear to be drawn on the celestial dome. However, the stars that compose them are not small bright spots, but gigantic bodies emitting large amounts of energy in the form of electromagnetic radiation. Located at different distances from each other, the stars form groups that can only be seen in 3D. To measure such distances a very large unit is used. It is called “light-year” and it corresponds to the distance traveled by the light during a year. Its value is approximately 10 billion of kilometers.

Some constellations have been used since Antiquity to guide navigators and explorers, such as Ursa Major, Ursa Minor or the Southern Cross. And there is a set of 12 constellations especially known, included in a strip of the sky determined by the plane of the orbit of the Earth around the Sun. This set is called the Zodiac and each of the constellations that form it is particularly visible at some time of the year. In Antiquity, in some cultures, these constellations gave name to the so-called “signs of the zodiac”, since the apparent motion of the Sun on the celestial sphere places it, precisely, on each constellation during certain months of the year. But in reality, during its annual trajectory, the Sun travels to a total of 13 constellations. In chronological order, these are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Ophiuchus (the least known), Sagittarius, Capricorn, Aquarius and Pisces. Due to the complex motion of the Earth in its orbit around the Sun, the Sun passes in front of each of them approximately one month later! than the dates that were assigned to them several thousand years ago.

In these videos we take a spacewalk that shows us the real three-dimensional arrangement of the stars that configure each constellation.

The Sagittarius constellation, or “the archer”, is usually represented as a centaur holding a bow. The video shows 23 of its stars, of which the closest one to Earth is located at a distance of 89.09 light-years from us.