Unit 2. The planets in the Solar System

The Solar System The Solar System consists of a central star, the Sun, and several other bodies bound by gravity that move around the Sun the bodies include planets, dwarf planets, satellites and another small bodies

In our Solar System there are: Eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Five dwarf planets: Ceres, between Mars and Jupiter, and the ones called the Plutoids (Pluto, Haumea, Makemake and Eris), located beyond Neptune

Among the planets, we can distinguish between the inner and the outer planets: The inner planets, are also called terrestrial planets, are the nearest planets to the Sun. They have a rock composition. They are Mercury, Venus, the Earth and Mars The outer planets are the farthest planets from the Sun. They consist mainly of gas. They are Jupiter, Saturn, Uranus and Neptune

2-THE EARTH, STRUCTURE AND GEOGRAPHIC COORDENATES

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About our planet The Earth is a rocky, almost spherical planet. Its radius is Km. The Earth is formed by four spheres: The Atmosphere surrounds the Earth. It is the outer sphere and lightest sphere of all, It is formed by a mixture of gases, called air. The Hydrosphere means all the water on the Earth: oceans, seas, lakes, rivers, subterranean water, etc. Water covers three quarters of our planet. The geosphere is the solid sphere, although in some parts it can be viscous due to its high temperature. It is formed by mineral rocks and metals. It has three layers: the crust, the mantle, and the core. The biosphere means the living beings which inhabit the Earth and which live in three other spheres

3. The Earth’s movements

The earth makes two types of regular movement: Rotation and Revolution. Rotation, occurs when the Earth spins on its axis every 24 hours. Revolution: the Earth makes a full orbit or revolution around the Sun in 365 days, 6 hours and 9 minutes. A sidereal year is the time the Earth takes to orbit around the Sun

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4. The Moon The Moon travels around the Earth once every 29,8 days. The Moon has no atmosphere There are maria (basaltic seas) and craters on the surface of the Moon The Moon has four phases: New Moon, Full Moon, Waxing Crescent and Waning Crescent

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Effects of the Moon on the Earth: Eclipses happen when the Earth, the Moon and the Sun are in a straight line. Tides are an effect of the gravitational attraction of the Moon and the Sun on the Earth

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