homework encyclopedia

12 Space

Astronomers gather information

about space in buildings called

observatories. Many astronomers use

an optical telescope to look at light

from space. Radio astronomers use

a radio telescope or an. ARRAY.

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.

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.

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-colour radio picture.

FIND OUT MORE. Astronomy 11 • Space Observatories 29 • Stars 24–25 • Telecommunications 192–

4 VERY LARGE ARRAY

The world’s largest radio telescope

array is the Very Large Array in

Socorro, New Mexico, USA. It has

27 movable dishes. Working

together, they see as much

detail as one dish 27 km

(17 miles) wide.

The New Technology Telescope has a

mirror 3.5 m (11 ft 6 in) wide and sits in

a rotating room, so that the astronomer

can turn with the telescope

OBSERVATORIES

Observatories

LA SILLA OBSERVATORY 3

The telescope domes at La Silla

Observatory, in Chile, are 2,400 m

(7,900 ft) above sea level and remote

from artificial light and pollution.

ARRAYS

1 RADIO MAP OF SKY

If our eyes could detect radio

waves, this is how we would see

the sky from Earth. The red band

shows the strongest signals.

Main building

houses a 3.6 m

(11 ft 10 in) telescope

Dome opens at

night to reveal sky

to telescope

Dish collects radio

signals and focuses

them onto aerial

Aerial picks up

signals and feeds

them to receiver

Rail track

allows dishes

to move

Pivot allows

dish to tilt

observatory