93 years have passed since the discovery of Pluto

17 Feb. () –

This February 18 marks the 93rd anniversary of the discovery of Pluto by the American astronomer Clyde William Tombaughfrom the Lowell Observatory in Flagstaff, Arizona.

It was considered the ninth and smallest planet in the solar system by the International Astronomical Union and by public opinion from its location in 1930 until 2006, –when it was reclassified as a dwarf planet–, although its definition has always been the subject of controversy among astronomers.

For many years there was a belief that Pluto was a satellite of Neptune that had ceased to be a satellite by reaching a second cosmic speed. However, this theory was rejected in the 1970s.

After an intense debate, and with the proposal of the Uruguayan astronomers Julio Ángel Fernández and Gonzalo Tancredi before the General Assembly of the International Astronomical Union in Prague, Czech Republic, it was unanimously decided in 2006 to reclassify Pluto as a dwarf planet, requiring that a planet must have orbital dominance. Its classification as a planet was proposed in the draft resolution, but it disappeared from the final resolution, approved by the General Assembly of the UAI. Since September 7, 2006, it has the number 134340, granted by the Center for Minor Planets.

But since then, many scientists believe that Pluto must once again be a planet. But not because it has a climate, a layered atmosphere, possible organic compounds, liquid oceans and its own moons, as experts reason based on scientific evidence, but because that is how it has been learned in schools, an argument also valid for the Society for the Preservation of Pluto as a Planet.

Pluto has an eccentric orbit and highly inclined with respect to the ecliptic, which it travels approaching at perihelion to the interior of Neptune’s orbit. It also has five satellites: Charon, Nix, Hydra, Cerberus and Styx, which are celestial bodies that share the same category, Wikipedia reports.

Its great distance from the Sun and the Earth, together with its small size, prevents it from shining above magnitude 13.8 at its best moments (orbital perihelion and opposition), for which reason it can only be appreciated with telescopes from 200 mm aperture, photographically or with a CCD camera. Even at its best it appears as a stellar-looking, yellowish, featureless point star (apparent diameter less than 0.1 arcseconds). It was not until 2015 when the New Horizons space probe passed over the planet and allowed its real appearance to be clearly appreciated for the first time.