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WHAT DO ASTRONOMERS STUDY TODAY?

Modern astronomers are trying to answer big questions

about the Universe. By studying stars at different stages

of life, they work out how stars are born, live, and die.

By studying galaxies, they are finding out how and

when the Universe began and how it might end. They also

explore the planets and other bodies in the Solar System.

WHEN DID PEOPLE FIRST STUDY THE SKY?

Records from the earliest civilizations show that people studied the

Sun, Moon, and stars more than 5,000 years ago. The priests of Babylon

and Ancient Egypt recorded the movements of the Moon and the

stars and used them to create a calendar for farming and religious

events – but people probably studied the sky long before that.

WHAT TYPES OF TELESCOPE ARE THERE?

Galileo’s telescope used glass lenses to gather and

bend light to a focus. This kind of telescope is called

a refractor, because the lenses refract (bend) light.

A telescope that uses mirrors is called a reflector – the

mirrors reflect light to bring it to a focus. Some

telescopes are launched into space for a clearer view.

Space telescopes gather light and invisible rays,

such as gamma, ultraviolet, infrared, and X-rays.

Astronomy is the science that studies the stars and all

the other bodies (objects) in space. The. TELESCOPE

is an astronomer’s most useful tool – it makes faint

and far-distant objects visible.

An astronomical telescope uses lenses

or mirrors to gather and focus the light

from distant objects. This makes it easier

to study them in detail. The first person to

observe the heavens using a telescope was

the Italian scientist Galileo Galilei, in 1609.

1 HOW A REFRACTOR WORKS

Light comes into the front of the

telescope. A large objective lens

focuses the light to a point near

the bottom. You look through

an eyepiece lens, which magnifies

the image and focuses it onto

your eye. You can move the

eyepiece in and out to bring

the image into sharp focus.

4 SMALL REFRACTOR

Amateur astronomers

use small telescopes,

which are easy to carry.

Refractors give sharp

images, and are

especially good for

looking at the

Moon and planets.

POWERFUL TELESCOPE 3

The William Herschel Telescope is

at the Roque de los Muchachos

Observatory on La Palma, in

the Canary Islands. It is a

large reflector telescope – its

primary (main) mirror is 4.2 m

(13 ft 9 in) wide.

ASTRONOMY

Astronomy

TELESCOPES

1 SIGHTING THE STARS
Early Indian astronomers watched
the stars with an astrolabe, an
instrument for measuring star
positions and movements.

Telescope can be pointed

to any part of the sky,

locked on to a star or other

body, and moved to follow

it across the sky

This objective lens (inside) focuses

all colours of light to the same

point to reduce colour blurring

Dewcap fits over top of telescope

to prevent dew forming on the

objective lens

Star diagonal

reflects image

so you can see

it from above

Open frame makes

the telescope lighter

and easier to move

Incoming light Objective lens

Finderscope helps

find a target

more quickly

Focus point

Eyepiece

Mounting

Eyepiece

Tripod

FIND OUT MORE. Lenses 181 • Light 178–179 • Observatories 12

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astronomy