Located in the Kuiper Belt, this dwarf planet has five satellites

A tour of the surface of Pluto and the reason why it stopped being a planet

Children of my generation studied in school that the Solar System had nine planets and that the last of them was the smallest.

Phaethon, the hypothetical fifth planet that has never been found between Mars and Jupiter
Three possible dark stars have been detected, a celestial body that was only a hypothesis

Pluto has always been a world that sparks the imagination. It was the last planet in the Solar System to be discovered, specifically in 1930 and by the American astronomer Clyde Tombaugh (1906-1997). Its discoverer did not know the news that surprised many of us in 2006, when the International Astronomical Union stopped classifying Pluto as a planet, something that bothered many people.

After all, for many years we had been taught in school that the Solar System had nine planets and now we only had eight. For what reason? The reason was the discovery of other objects in the Solar System, today considered dwarf planets, like Pluto. One of them, Eris (discovered in 2005 in the scattered disk, a remote region of the Solar System) has a diameter of 2,326 kilometers, only 50 less than Pluto. If Pluto was a planet, why not Eris?

This complicates things even more, because in 2005 Makemake was also discovered, another spherical dwarf planet with a diameter of 1,430 kilometers and located, like Pluto, in the region known as the Kuiper Belt. Furthermore, in 1801 Ceres was discovered, another dwarf planet, in this case located in the asteroid belt between Mars and Jupiter, and with a diameter of 946 kilometers. This neighborhood of small planets in the Solar System is completed by Haumea, an ellipsoidal world in the Kuiper Belt and with a diameter of 1,632 km. In the end, it was easier and more logical to "demote" Pluto than to increase the neighborhood to 14 planets.

Humanity knew very little about the surface of Pluto. In 1978, its largest satellite, Charon, was discovered, whose size would almost allow it to aspire to be a dwarf planet itself, since it is 1,208 km in diameter. As a curiosity, Pluto and Charon are always looking at each other with the same faces, due to the fact that they form what is known as a double planet, that is, the center of the orbits in which they move does not are located inside none of them.

On July 14, 2005, NASA's New Horizons probe flew over Pluto, capturing some good images of its surface, which you can see in this article. Unfortunately, because it was a relatively brief pass (as the probe was flying at about 84,000 km/h), a part of Pluto was in shadow, so it could not be captured in detail, so its nature remains largely unknown.

A few months after that flyby of the New Horizons probe, in October 2005, the Hubble Space Telescope announced the discovery of two other satellites of Pluto: Nix and Hydra, much smaller than Charon. Finally, in 2011 a fourth satellite, Cerberus, was discovered, and in 2012 a fifth, Styx. Both the name of Pluto and those of its satellites have their origin in Greek mythology.

One of the greatest curiosities about Pluto is that this dwarf planet has a large heart that covers a considerable part of its surface. This heart was discovered in 2015 and was named Tombaugh Regio, in honor of the discoverer of the planet. It is estimated that it was caused by an oblique collision with an object which measured 643 km in diameter. If you want to know more about Pluto and its icy surface, I encourage you to watch this excellent video published today by V101 Space:


Photos: NASA.

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