Childrens Illustrated Encyclopedia

47

Astronomy 47-

ObservatOry

astronomers study space

from observatories (above)

that are often at the top of

a mountain where there is

a clear view of the sky. this

photograph took several

hours to make. the stars

trace circles because the

rotation of earth makes

them appear to move

across the sky.

there are amazing sights to be seen in the heavens—other worlds

different from our own, great glowing clouds of gas where stars are born, and

immense explosions in which stars end their lives. astronomers are scientists

who study all the objects in the universe, such as planets, moons, comets, stars,

and galaxies. astronomy is an ancient science. the early arabs and greeks

looked up to the sky and tried to understand the moons, stars, and planets.

however, most of these objects were too distant for early astronomers to see in

any detail. it was only after the invention of the telescope in the 17th century

that people really began to learn about the universe. today, astronomy makes

use of a vast array of equipment to explore space. astronomers use ground-

based telescopes of many kinds, launch spacecraft that visit the other planets

in the solar system, and send up satellites to study the universe from high

above earth’s surface.

space telescOpe

the optical telescope is

one of the main tools of an

astronomer. most astronomical

optical, infrared, and ultraviolet

telescopes focus light from

distant stars using a large

curved mirror instead of lenses.

this is because it is not possible

to construct a lens big enough,

and even if it were, a lens would

produce distorted images.

launched in 1990, the hubble

space telescope is an optical

telescope that orbits high above

earth in order to avoid the

blurring effect produced by

earth’s atmosphere.

High-gain antenna

receives commands

from Earth and returns

Hubble pictures as

TV signals.

Main (primary)

mirror, 7.8 ft (2.4 m)

in diameter, collects

and focuses light.

Computers

coordinate all

the onboard

systems.

Second

high-gain

antenna

Light is reflected from the main

mirror to the secondary, and

then to the cameras and

other detectors behind

the main mirror.

Reaction wheels

point Hubble at

stars and other

targets in space.

Space

Telescope

Imaging

Spectrograph

breaks up light

into its constituent

wavelengths.

Sunshade protects the telescope

at launch, and helps prevent

bright sunlight from spoiling

the images.

Fine guidance

sensors lock on to

bright stars, to

ensure that the

telescope is steady

and the images are

not blurred.

Handrail for

astronauts

Magnetometer senses

Hubble’s movements

through Earth’s

magnetic field.

Secondary mirror

is supported within

the telescope

tube.

Solar arrays

provide power

by converting

sunlight into

electricity.

Near-Infrared

Camera and

Multi-Object

Spectrometer

contains three

infrared

detectors.

Wide Field

Camera (WFC3)

is the main camera

Cosmic for visible light.

Origins

Spectrograph

(hidden from

view) analyzes

ultraviolet light.

RECEIVING DATA ON EARTH

communications with the hubble space telescope

are relayed by satellites to and from large microwave

dishes in new mexico. all data passes through nasa’s

goddard space Flight center. here, engineers

constantly monitor the spacecraft’s health (right).

hubble astronomers work at the space telescope

science institute, and control the telescope’s

observing schedule. the schedule is set in

advance down to the last second.

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