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Aardvark Communications:

A Practical Guide to Astronomy


Telescopes & Satellites


When astronomers go looking for new stars, comets or galaxies they use a number of different tools. To understand how these tools operate you must first understand the speed of light.

The distance light would travel in one year is 9460 billion km. For example, if you want to walk to the nearest star to us, Proxima Centauri, you better get started soon because its 40,678 billion km away, that is 4.3 light years. So when you view objects in the sky such as Proxima Centauri, you view them as they appeared 4.3 years ago, because that is how long its light took to reach us. .


Telescopes

Hale Telescope at Palomar Mtn (California) can detect objects less than one 10 millionth as bright as those the human eye can see.

Kitt Peak, Arizona-has a reflector 4 m (13ft) across. Kitt Peak also has the world's largest solar telescope.


Radioscopes

Radio Telescopes- detect a wide range of signal sources, from exploding stars to interstellar molecules. Radio waves pass through our atmosphere very easily.

Pluto Express-radioisotope, powered by non-weapons grade plutonium. To be launched in 2002, and will send back images of Pluto and its moon, Charon in 2014.

Arecibo, Puerto Rico has the world's largest radioscope in the world at 305m (1000 ft) across. It can pick up signals from 15 billions light years away.

VLBA (Very Long Baseline Array) is a series of listening dishes that are linked together throughout N. America. Consisting of 10 receivers, each dish in the series is 82 ft wide. All the info is gathered together at Sorocco, NM, and is sorted out to act as 'one giant ear to the sky'.

Max Planck Institute-Bonn West Germany has a huge steerable radio telescope.

Microwave antennas can detect residual radiation from the Big Bang (13-15 billion yrs ago).


Satellites

Satellites send data back to Earth where tracking stations receive the information for scientists to study. Typically, satellites are powered by solar panels that generate energy from the Sun.

There are several types of satellites:

  • Communications Satellites (comsats) used for telephone & television transmissions. They receive info from Earth and redirect it to another place on Earth.
  • ERTS- (Earth Resources Technology Satellites) used to moniter sea and land. ERTS helps with sea currents, weather and coastline monitering.
  • SAGE- (Stratospheric Aerosol & Gas Experiment) moniters the ozone layer.
  • IRAS- (Infra-Red Astronomy Satellite) looks for infra-red radiation from other galaxies.
  • OSO satellites were launched in 1962 to observe the Sun.
  • Uhura- was the name of a satellite that was sent up into space in the early '70's. It successfully discovered several binary systems (two star systems) that emitted X-rays, one pair was thought to have a black hole at its centre.
  • Copernicus- was a 2.5 ton orbiting observatory satellite which scanned the heavens for ultra-violet light.
  • COS-B (launched 1975) looks for gamma rays & X-rays.
  • Exosat (launched 1983) looks for neutron stars.
  • Hubble Space Telescope (launched in April 1990) -can detect ultra-violet & infra-red waves as well as visable light. Shortly after the launch of Hubble, it was found that one of the two mirrors was .002 millimetre off, making all the images out of focus. In 1993, NASA sent out a team of astronauts to make the adjustments. They were very successful.

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