space

• advantages of using satellite-based telescopes

  - no atmosphere to absorb light

  - full range of EM waves can be observed

  - can be used in cloudy weather/ daytime

  - no light pollution
• uses of satellites


  - GPS

  - weather forecasting

  - communications

  - scientific discovery
• geostationary satellite


  - maintains its position above the same location on the Earths surface

  - placed above the equator

  - have an orbital period of 24 hours

  - placed at an altitude of 36 000 km
• challenges of space travel

  - manoeuvring in zero friction environment

  - fuel load on take-off

  - potential exposure to radiation

  - pressure differential

  - re-entry through an atmosphere
• moon


  a natural satellite of a planet
• dwarf planet


  an object that orbits a star but is not large enough or roughly spherical enough to be classed as a small planet
• planet


  a large ball of matter that orbits a star
• exoplanet


  a planet existing around another star, outside of our solar system
• star


  a large ball of matter that is undergoing nuclear fusion and emitting light and other forms of electromagnetic radiation
• sun


  the star in our Solar System
• solar system


  consists of a central star orbited by planets
• galaxy


  a large cluster of stars
• universe


  - many galaxies separated by empty space

  - continuously expanding
• asteroid


  an orbiting object which is even smaller than a dwarf planet
• big bang theory


  the theory that the universe originated in a huge explosion that released all matter and energy 14 billion years ago
• curved reflectors


  - a device which is used to strengthen a signal

  - brings waves of any kind (light, radio waves, microwaves etc.) to a focus

  - the aerial/receiver is placed at the focus where it can receive the strongest signal possible
• optical telescopes


  - detect visible light from space

  - objective lens should have a large diameter to detect as much light as possible

  - can only be used at night

  - cannot be used in cloudy or poor weather
• refracting telescope


  - objective lens is used to collect light from space, forms an image in the light-tight tube, the light cannot escape from the light-tight tube

  - the eyepiece lens then magnifies this bright image to make it bigger
• radio telescopes


  - very large and expensive

  - both land-based and mounted on satellites and are used to detect radio waves coming from space

  - can be used in bad weather because the radio waves are not blocked by clouds as they pass through the atmosphere

  - can also be used in the daytime as well as at night
• x-ray telescopes


  - detect x-rays from space

  - partly blocked by the Earth's atmosphere so these have to be at high altitude or flown in balloons
• space telescopes


  - used to detect other electromagnetic radiation such as infrared, ultraviolet and gamma rays which are blocked by the Earth's atmosphere

  - placed in orbit around the Earth

  - expensive to make and to launch and if faults occur, only astronauts can repair them
• continuous spectrum


  contains full spectrum of visible light
• line spectra (emission lines)


  specific colours emitted by specific elements when excited, like a finger print
• line spectra (absorption line)


  specific colours absorbed by specific elements when cold, like a finger print