P7.1 Naked-eye astronomy 4.0 / 5 based on 1 rating ? PhysicsAstronomyGCSEOCR Created by: nnenna2koolCreated on: 30-04-16 11:46 What is the solar system? Solar system - Collection of planets, comets and all other objects that orbit the Sun. The Earth takes 365 1/4 days to complete one orbit (a Year). It also rotates around an imaginery line called its axis. The moon orbits the earth and takes 28 days for one orbit. 1 of 8 The movement of the Sun The sun appears to move from East to West as the Earth is spinning on its axis. Solar day - The Sun reappears in the same place every 24 hours. Sidreal day - Time it takes for the Earth to spin around once on its axis (23 hours and 56 mins). Earth also moves further along its orbit of the Sun so for the same part of the Earth to be facing the Sun, it needs to turn for an extra 4 mins. 2 of 8 The movement of the stars As the Earth rotates on its axis, the stars appear to be moving in circles around the Pole star. They appear to be back in the same place after 23 hours and 56 mins ( Sidereal day). Constellation - A group of stars that form a pattern. We see different constellations in summer and winter as the Earth moves around the Sun. 3 of 8 The movement of the Moon Like the Sun, the Moon appears to move from East to West. The moon takes longer, it reappears in the same postition every 24 hours and 49 mins. As well as the Earth's rotation allowing a different view of the moon, the Moon is also orbiting the Earth (every 28 days). 4 of 8 Moving planets Mercury, Venus, Mars, Jupiter and Saturn can be seen with the naked eye. As the planets orbit the Sun, their positions appear to change each night against the background of fixed stars. Most of the time, planets seem to move from East to West like the sun. Sometimes the planets seem to go backwards - Retrograde motion. Retrograde motion happens as different planets take different amounts of time to orbit the Sun. Their postion depends on where the planet and the Earth are in their orbits. 5 of 8 The phases of the Moon We can only see the part of the Moon that is lit up by the sun. As the Moon orbits the Earth, we can see different parts of it lit up by the Sun. 6 of 8 What causes an eclipse Solar eclipse - Moon blocks the Sun's light. Lunar eclipse - Moon moves into the Earth's shadow. Moon and Earth both have shadows with areas of total darkness (Umbra) and areas of partial darkness (penumbra). When the Moon's Umbra touches the surface of the Earth, there is a solar ecipse formed inside the Umbra. When the moon passes into the Earth's Umbra, there is a lunar eclipse which are more common as the Earth's shadow is bigger than the Moon's. Eclipses are rare as the Moon doesn't often line up exactly with the Sun. Its orbit is tilted by 5' relative to the Earth's. 7 of 8 Locating objects in the sky Stars can be described like lights on the inside of a spinning sphere (the celestial sphere). It has an axis from the Pole star through the axis of the Earth. Also, a celestial equator which is an extension of the Earth's equator. 8 of 8
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