Can we consider the moon a planet?




There are a lot of strange moons in our solar system, but ours is perhaps the strangest. Not least because it is very big. Almost as a planet. The moon is one-fourth the size of Earth. With the exception of Pluto and Charon, the ratio of the size of the Moon and the Earth is the largest of the satellites of the planets of our solar system.

The moon still so great that it was not in compliance with the Earth’s orbit. Both bodies orbiting around a point between them, it is the center of gravity. It is about one and a half thousand kilometers below the Earth’s surface – but still four thousand kilometers from the center of the planet. As a result of the rotation of the Earth-Moon system as they whirl around the sun like a bit of a promoted dumbbells with different weights on the ends.

Another point which separates the moon from other natural satellites in the solar system – its orbit at any point is not convex with respect to the Sun, that is not bent toward him. The reason is that the gravitational pull of the Sun on the Moon than the Earth.

Here is the orbit of the Earth and the Moon:

Орбита Луны

Or even this:

Траектория Луны

The trajectory of the moon around the sun much like a circle. You need to greatly increase one of the sites to detect changes. French artist Lucien Rudo showed this clearly:


In fact, the Moon’s orbit around the Sun is only slightly perturbed by the presence of the Earth. If the earth had disappeared, the moon would rotate around the sun in much the same way as now revolves. It would not be as damaging as if the moon disappeared .

Why, then, the Moon is not considered a planet? And that means that the Earth-Moon system – a system of double planets?

The main reason which can not be considered the Earth and the Moon as a double planet – the center of gravity lies below the surface of the Earth. If the moon were a third heavier or a third more, the center of gravity would lie above the Earth’s surface, and two of the world truly would be a double planet. And because the system itself is not the only possible destination for our moon – satellite.

No, the moon is not officially considered a planet, despite the fact of her many planetary parameters. Which underlines arbitrary definition of the word “planet” and blurs the criteria. Very many astronomers are unhappy definition of “planet” to date.

Why, for example, the worlds that have so much in common, Mercury, Ceres and Pluto considered a planet, an asteroid and a dwarf planet, respectively, and with the huge differences between worlds, Earth and Jupiter are considered planets? Maybe we need another category in addition to the dwarfs, the earth types, and the other gas giants, which can enable the moon?

By the way, not so long ago, the new moon found at Pluto .
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Tags: Moon , Planets , Solar System .


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