17 years ago, on August 24, 2006, the International Astronomical Union (IAU) made a decision that changed the solar system forever. Many people still take issue with the decision regarding the status of Pluto.
the International Astronomical Union Members voted in favor of the motion defining exactly what astronomers mean by the term “planet”. Thus Pluto was reclassified as a dwarf planet, and our solar system was reduced to eight planets. Seventeen years later, this proposal is still controversial among the people IFLScience.
What do we mean by the term “planet”?
The International Astronomical Union has repeatedly considered possible definitions that include planets orbiting other stars (outer planets) and planets that have escaped from their star system. But there were problems as to whether the planets had left their star system, straying or not interstellar planetsThey don’t fit between the planets.
Finally, on the last day of the ten-day conference in Prague, the current definition was presented, voted on, and approved. Three conditions must be met in the planet:
- It must revolve around the sun, so all outer planets and stray planets are eliminated.
- It should reach hydrostatic equilibrium, which means it should be roughly spherical.
- Finally, it has to “keep its orbit empty” in order to be the main gravitational object.
Why was Pluto “lowered”?
Pluto does not fulfill the third condition. It has not “cleaned” its orbit, which it shares in part with Neptune. Defenders of Pluto’s planetary position have claimed that Earth, Mars, Jupiter, and Neptune haven’t “cleaned up” their orbits either. But with the exception of the Moon, Earth is 1.7 million times heavier than the other asteroids that cross its orbit. Pluto is only 7% heavier than them.
Controversy within and outside academia called this a demotion rather than a classification. Interestingly, Pluto was chosen as the first example of two new classes of objects, dwarf planets and plutoids.
It is emphasized throughout the discussion that the definition is far from perfect, and that planets are often defined not only as planets, but with additional adjectives: rocky, gas giant, ice giant, and so on. Thus, the term dwarf may one day be considered a subcategory of “planet” rather than something separate.
Video: Why is Pluto not a planet?
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