Pluto is not the first: a brief history of the forgotten planets of our solar system

A kindergartener in 2005 and a kindergartener in 2006 would have known very different facts about the number of planets in the solar system. 2006 was, of course, the year that Pluto was reclassified as a dwarf planet – much to the chagrin of the public who wanted to make our solar system romantic.

But long before the Pluto “controversy”, other objects moved from the official list of solar system planets. In fact, a kindergartener in the early 1800s would have known that Ceres was a planet.

Although the argument about the planet may seem like a modern astronomical debate, 19th-century astronomers were confused by the question of how to actually define what constitutes a planet.

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And, as mentioned, Ceres overtook Pluto in his controversy. The asteroid belt, which sits approximately between Mars and Jupiter, is filled with asteroids and asteroids. One of those celestial bodies is a surface covered with minerals such as ceres, clay and carbonate, and water ice. This is a different world, to be sure: because it is not completely frozen and covered in salt water, scientists believe that Ceres microbes can live life. This location is completely different from Pluto, which is far from the solar system and has a completely frozen surface. In addition, Ceres is a dull monochromatic gray, with Pluto’s colors ranging from white and black to clear orange.

However, there is one important thing that is common to Cyrus and Pluto: astronomers at one point thought they should be classified as planets, but later changed their minds. It all comes down to size, which is really important in the case of planetary science.

Flashback to the beginning of the 19th century. Giuseppe Piazzi, an Italian priest and astronomer at the Palermo Laboratory, answered a question almost three decades old: Why did Mars or Jupiter’s orbiter point to a planet even though no orbit has been found? Piazzi answered this question on January 1, 1801, by announcing the discovery of a “star” moving from the constellation Taurus. Scientists soon decided that it must be a missing planet and that the matter was resolved.


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Then another “planet” was discovered. On March 28, 1802, the German physician and astronomer Heinrich Olbers discovered Pallas; It was quickly followed by Juno in 1804 and Vesta in 1807. Each was systematically designated as a planet, although astronomers began to doubt whether this increasingly complex system worked. Despite decades of suffocation for scientists, numerous new discoveries between 1845 and 1852 left the astronomical community. 15 Asteroids to take into account. Nothing new was labeled as planets, but it was clear that reforms were necessary. By 1867, it was clear that Ceris was too small to be grouped with an Earth-like body, so it was given a new designation: a small planet. Instead of giving more fancy names and symbols, they will be labeled with numbers based on when they were discovered or the resolution of their orbit.

This takes us to Pluto. Ceres is 588 miles in diameter (compared to 7918 miles in diameter on Earth), and Pluto is 1477 miles in diameter. When the International Astronomical Union met in 2006, it did not save Pluto from being axed. The reason is that, quite simply, astronomers have concluded that there are three criteria for being considered a sphere:

Therefore, the IAU’s three criteria for a full-scale planet are:

It is in orbit around the sun.

It has enough mass to achieve hydrostatic equilibrium (almost circular shape).

It has “destroyed the neighborhood” around its orbit.

Because Pluto did not meet the third requirement – it did not “destroy the neighborhood” around its orbit – it lost its status as a planet. Destroying the environment means that the area of ​​space around the sun is absorbed by the planet and without large bodies. Like Pluto, Ceres does not explicitly exceed this criterion: the asteroid belt inhabiting Ceres is evidence of a “failed” planet that did not destroy its surroundings. In fact, there are many more large bodies – Vesta, Pallas and Hygia – in the vicinity of Ceres.

This distinction of the planet Pluto was made in 1930 by the American astronomer Clyde W. It has been 76 years since the invention of the tomb. The transformation of Pluto into a dwarf planet has been controversial, not just among ordinary astronomers. A group of American scientists argued in December in the scientific journal Icarus that the “planet” should be defined as a geographically active celestial body. One co-author argued that “our solar system may have more than 150 planets”; The paper said that distinguishing planets from moons is culture, not science, and hinders a proper understanding of astronomy.

“The non-scientific public in the Latin West in the 1800s developed its own folk taxonomy of planets that reflected the concerns of astrology and theology, and this folk taxonomy eventually affected scientists,” the scientists explained. They later concluded that “the use of geophysical concept with subdivisions for individual features (including gravity dominance) makes planetary concept useful and deeply insightful for interaction with the general population.” This did not happen in 2006 because “not enough time was taken to sort out these issues” and as a result the referendum led to a “deep divide in society”.

Paradoxically, despite the ouster of Pluto, Ceres received almost a promotion. The previous 21st century proposition for defining a planet was that a planet would have enough mass to orbit a star without being a satellite or star of a planet. If this definition were accepted, Ceres would have become the fifth planet from the Sun.

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