Space

Space:

The solar system:

Structure of the Solar System:

• The Sun is a star in a galaxy called the milky way.
• The Solar system consists of the sun, planets, dwarf planets, moons, asteroids and comets.
• Planets, dwarf planets, asteroids and comets orbit the Sun.
• A moon orbits a planet.

The Sun:

• The Sun formed from a cloud of dust and gas (a nebula) which was pulled together by gravity.
• As the nebula collapsed, it became sufficiently hot and dense for nuclear fusion reactions to start.
• In a stable star like the Sun, gravitational collapse is balanced by expansion due to fusion energy.
• A protostar is the early stage in the formation of a star, before nuclear fusion occurs.
• Nuclear fusion is the joining together of two smaller atomic nuclei to produce a larger nucleus. Radiation is released when this happens. Nuclear fusion happens in stars like our Sun, and in hydrogen bombs.

Orbital Motion:

• Planets follow circular orbits around the Sun.
• Satellites follow circular orbits around their planets.
• Gravity provides the force that causes planets and satellites to orbit.
• A satellite moving too quickly will leave orbit and move into space. A satellite moving too slowly will leave orbit and fall towards Earth.
• An artifical satellite in polar orbit travels faster and with a smaller orbital radius than one in a geostationary orbit.
• An object in a circular orbit at a constant speed is accelerating because its direction is constantly changing.
• For an orbit to be stable, the radius of the orbit must change if the speed of the orbiting object changes.
• The closer two bodies…