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OBSERVATORIES

Astronomers gather information about space in buildings called observatories. Most astronomers use an optical telescope to look at light from space. Radio astronomers use a radio telescope or an ARRAY.

WHY ARE MOST OBSERVATORIES ON TOP OF MOUNTAINS?

Optical telescope observatories are built on high ground above the thickest layers of Earth’s atmosphere. Astronomers can see into space more clearly from there because there are fewer air currents, and the air is cleaner and contains less moisture.

HOW DO RADIO TELESCOPES WORK?

Huge, dish-shaped radio telescopes pick up radio waves from space. The dish gathers the signals and reflects them onto an aerial. The aerial sends electrical signals to a receiver, then to a computer, which converts them into a false-color radio picture.

ARRAYS

Astronomers often use several radio telescopes working together as an array. An array creates a large total area for collecting signals, and can reveal far more detail than one dish on its own. The signals from each dish are combined using a technique called interferometry.

WHAT DO ASTRONOMERS USE ARRAYS FOR?

Using arrays, radio astronomers can make detailed radio maps of many different kinds of objects in space. The objects they study include quasars and radio galaxies with immense plumes of radio-emitting gas stretching for millions of light-years, the remains of supernovas (exploded stars), gas bubbles blown off dying stars, and the planets Jupiter and Saturn.

VERY LARGE ARRAY

The world’s largest radio telescope array is the Very Large Array in Socorro, New Mexico. It has 27 movable dishes. Working together, they see as much detail as one dish 17 miles (27 km) wide.

Copyright © 2007 Dorling Kindersley

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