KOMPAS.com – Planets, in a simple sense, are celestial bodies that orbit around the sun as the center of the solar system.
However, not all celestial bodies that orbit the sun can be called planets, because they need to meet a number of certain criteria.
Reported by NASA, a celestial body can be defined as a planet if it meets all of the following criteria:
- Orbiting a star in our cosmic neighborhood, namely the Sun
- It must be large enough to have enough gravity to force it into a spherical shape
- It must be large enough so that its gravity clears out other objects of the same size near its orbit around the Sun.
Planets are also generally round, and this is proven by the eight planets in the solar system which are all round.
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So, why are all the planets in the solar system round?
The reason planets are round
The sun and planets in the solar system are round because the gravitational force of their mass pulls all the material towards the center, this smoothes their surfaces into a round shape.
Preferably, many small celestial bodies in the solar system are not spherical because gravity is not strong enough to smooth their shape.
Quoted from the Britannica page, when an object has a diameter of more than several hundred kilometers, its shape tends to be more rounded than not.
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The simplest examples are the round earth and the irregular comet 67P. The diameter of the Earth is about 12,700 kilometers and comet 67P is about 4 kilometers in diameter.
The Earth has enough gravity to pull all material towards the center. The Earth has a mass of 6 x 10^24 kilograms and is quite round.
To escape Earth’s gravity, you need to travel at a speed of about 11 kilometers/second. That kind of speed requires the biggest rockets.
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In contrast to the smaller gravity of Comet 67P. To avoid gravity you only need to travel at a speed of about 1 meter/second.
The small gravitational mass means that comet 67P is not round at all. It has a mass of 10^13 kilograms, almost a trillion times lighter than Earth.
How are planets formed?
iStockphoto/coffeekai
Illustration of a supernova explosion. The beginning of the formation of the solar system.
Reported by the American Museum of Natural History, the sun and planets formed together from a cloud of gas and dust called the solar nebula, 4.6 billion years ago.
The shock wave from a nearby supernova explosion triggered the collapse of the solar nebula. This phenomenon causes the sun to form in the center.
At the same time the planets formed in a thin disk that orbited around him. In the same way, moons form and orbit giant planets.
Also read: Is Pluto a Planet? The following is the explanation
Planets are large enough to have enough gravity to force them into a spherical shape.
Comets condense in the outer solar system, and many of them are flung to great distances by close gravitational encounters with giant planets.
After the sun flares up, powerful solar winds cleanse the solar system of gas and dust, and asteroids represent the remaining rocky debris.
The solar system that exists today was formed.
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2024-02-27 13:30:00
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