Planets off Science, Astronomy, Solar System

planets

Planets (from Greek plánetes "the wandering ones"), historically wandering stars A planet is a non-luminous celestial body that has a minimum mass (and thus has an approximately spherical shape) and moves on a Keplerian orbit around a central celestial body (sun, star) that illuminates it. A planet is also the dominant object in its orbit.

According to the new definition, our solar system now has eight known planets. In order of increasing distance from the sun they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Uranus and Neptune are not visible to us with the naked eye.

Until 2006, Pluto also counted as a planet. However, under the new planetary definition, it was classified as a dwarf planet because it does not meet the criterion of being the dominant object in its cosmic environment.

The earth`s orbit divides the planets into inner (lower) and outer (upper). Since the inner planets Mercury and Venus never stray far from the Sun in their apparent orbits in the sky, they can only be seen as evening stars or morning stars. The outer planets Mars, Jupiter, Saturn, Uranus and Neptune, on the other hand, can traverse the entire belt of the ecliptic and therefore also come into opposition to the sun. Moons are known for all planets except the inner planets. (exoplanet).

The first four relatively small planets (earth-like or terrestrial planets) are distinguished from the Jupiter-like or Iovian giant planets, which mainly consist of gaseous matter, due to their different structure.

The planets rotate in the correct direction around their axis, with the axes having a tilt similar to that of the Earth`s axis. Only Uranus has its axis of rotation almost in its plane, and Venus has been measured to rotate in the opposite direction. The distances between the planets and the sun are subject to a certain law called the Titius-Bode series. All planets except Mercury are surrounded by a more or less dense atmosphere.