Why can the Moon be considered a planet?

The moon can be considered a planet (Image: AP).

The International Astronomical Union (IAU) has a very strict definition of the word "planet". According to the definition, which was drafted, revised and agreed in August 2006, a body is officially considered a planet if it orbits the Sun, has enough mass to be spherical, and has " clean up" the entire neighborhood around its orbit.

Under this strict rule, only 8 celestial bodies in the Solar System can be considered planets, including: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Interestingly, this definition would remove Pluto from the list of planets in the Solar System, which is an extremely controversial move with many scientists. Over time, they have called for a reconstruction of a broader, more precise definition, based solely on the physical properties of the celestial body in question.

Led by scientist Phillip Metzger of the University of Central Florida, the researchers are calling for recognition of a third criterion, which is that on the surface it is or has been physically active. Geological.

This would place many of the Solar System bodies in the ranks of "planets", including Earth's Moon and many others, and even some "dwarf planets", or "asteroids". .

The Solar System may be redefined by the recognition of "new planets"

It may sound like a no-brainer, but the fact that these celestial bodies qualifies them the same means that they share a common definition, say the researchers behind the new study. "It's like identifying mammals," Metzger said. "They're mammals whether they live on land or in the sea. It's not their place. It's about how intrinsic characteristics make them."

Over a period of five years, the team conducted an in-depth review of the 400 years of scientific literature on the planets. They found that, over time, the definition set forth by Galileo in the 1630s was dropped.

At the time, Galileo argued that planets were objects made of elements that changed over time, like the Earth. Or, as the researchers explain, they are geologically active. The team also cites Galileo's argument that the planets reflect sunlight, rather than produce their own light.

Metzger et al. point out that this definition was in use until around the 20th century. However, when Pluto was discovered in 1930, it was already classified as a planet. But by the mid-1950s, researchers noticed that interest in planetary science was dwindling, at least according to the research literature, as the number of articles published during this time decreased. decrease.

Galileo's definition of the planets in the Solar System was gradually overlooked, and changed to suit the weak market.

"We have shown that through biometrics there was a time when astronomers didn't pay much attention to the planets," Metzger explains. "And it was during that forgotten period that the spread of Galileo's pragmatic definition was interrupted."

That void was eventually filled by folklore, typically published books that made meteorological predictions and theories based on the positions of a handful of planets. In other words, they are astrology.

"This may seem like a small change, but it undermines the central idea about planets that was passed down from Galileo," Metzger said. "Planes are no longer defined by complexity, with active geology and the potential for life, and civilization. Instead, they are defined by simplicity, following those patterns. certain idealized path around the Sun."

Metzger insists he will try to once again bring Galileo's theory "out of the shadows", so that his insight into the universe becomes "crystal clear".