Exploring Space

Section 1: Radiation From Space

A.Electromagnetic Waves

1. Light from the past

a. Light seen from stars, may have left

that star many years ago.

b. Light and other energy leaving a star

are forms of radiation.

c. Radiation is energy that’s transmitted

from one place to another by

electromagnetic waves.

d. Because of this radiation, its called

electromagnetic radiation

B. Electromagnetic Radiation

1. Sound waves, a type of mechanical

waves can’t travel through empty space.

a. Then how do we hear the voices of

astronauts while they are in space?

b. When they speak into a microphone, the

sound is converted into electromagnetic

waves called radio waves.

c. They are then converted back into sound by

electronic equipment and audio speakers.

2. Types of electromagnetic radiation

a. Radio waves, visible light, gamma rays, X-

rays, ultraviolet waves, infrared waves, and

microwaves.

3. Measured in wavelength and frequency.

a. Wavelength is the distance from the top of

one wave to the next.

b. Frequency is the number of wavelengths that

pass by a certain point in one second.

c. As wavelength increases; frequency

decreases and vice versa.

The Electromagnetic Spectrum

C. Speed of Light

1. Light is part electricity and part magnetism

2. Speed of light is 3.8 X 108 m/s or 300,000

km/s

3. All electromagnetic waves travel at the speed

of light.

4. Universe is so large it takes millions of years

from the light from some stars to reach the

Earth.

5. Once electromagnetic radiation from stars

and other objects reach Earth, we can use it

to learn about the source of the

electromagnetic radiation.

6. One tool used for observing electromagnetic

radiation from distant sources is a

TELESCOPE.

Water Found on Mars!

D. How we use Electromagnetic Waves

1. Light from the Past

a. Stars are images from the past.

b. Light from stars takes time to travel through

space.

c. Our Sun is about 150 million kilometers away

(about 8 minutes travel time)

d. Alpha Centauri (our closest neighboring star) is

about 40 Trillion Kilometers away; about 4.2 years

travel time.

e. Light travels at 300,000 km/sec or 186,000

miles/second.

f. Light travels 9.5 trillion kilometers in a year (this is

one light year).

g. A light year measures both distance and time!!!

E. Radio Waves

1. Longest wavelength: 105 to 10-1 meters.

2. Lowest frequency: 103 to 109 Hertz

3. Used for communication and information transfer.

F. Microwaves

1. Wavelength: 10 -1 to 10 -3 meters & Frequency: 109 to 1011 Hertz.

2. Used for communication, Information transfer and cooking.

G. Infrared

1. Wavelength: 10 -3 to 10 -6 meters & Frequency: 1011 to 1014 Hertz

2. Used for heat production and Thermography.

3. “Seen” by some insects and animals.

H. Visible Light

1. Wavelength: 10 -7 meters & Frequency: 1015 Hertz

2. Colors seen by human eyes

I. Ultraviolet

1. Wavelength: 10 -7 to 10 -9 meters & Frequency: 1015 to 1017 Hertz

2. “Seen” by some insects

3. Cause of tanning, sunburn, skin cancer

4. Degrades rubber & plastic materials (fades cloth & paper)

J. X-Rays

1. Wavelength: 10 -9 to 10 -11 meters & Frequency: 1017 to 1019 Hertz

2. Bone scans, Information transfer

K. Gamma Rays

1. High level radiation (Very Dangerous)

2. Shortest wavelength: 10 -11 to 10 -15 Meters

3. Highest frequency : 1019 to 1023 Hertz

L. How We Use Telescopes

1. We use the electromagnetic spectrum to

observe space.

2. Optical Telescopes

a. Produce magnified images of objects.

b. Visible light is collected by mirrors or lenses and

then focused.

3. There are two types of telescopes.

a. Optical Telescopes (You need light for these)

b. Radio Telescopes.

M.Refracting Telescope (Optical)

1. Light from an object passes through a

convex objective lens and is bent to from an

image on the focal point.

2. The images is then magnified by the

eyepiece.

3. Limited in size

4. Worlds refracting mirror is Yerkes Refracting

Telescope

a. Just over a meter in diameter (distance

across)

Diagram of a Refracting

Telescope

Focal

Point Convex Lens Eyepiece

N.Reflecting telescopes

1. Light passes trough the telescope housing to

a concave mirror

2. Mirror reflects light to a flat mirror

3. Flat mirror redirects light to a focal point

4. Light passes through the focal point, to the

eyepiece

5. Eyepiece magnifies image

6. Largest in the world = 10 meters wide

Diagram of a Reflecting Telescope

O. Optical Telescope Uses:

1. Most “home” use telescopes are optical.

2. Used to see moon features and close

planets.

3. Scientific optical telescopes are housed in

OBSERVATORIES.

a. Observatories have domed shape roofs that open.

b. Observatories built on mountains or deserts, far

away from cities.

1. Prevents city light interference and pollution blurring.

2. Decreases “down time” due to poor weather.

c. Not all telescopes are housed in observatories.

P. Radio Telescopes.

1. Designed to pick up radio

waves emitted from space.

2. Usable in any weather!!!

a. Radio waves are concentrated by

dish shaped body.

b. Concentrated waves are directed

to a focal point.

c. Focal point is fixed with a

receiver.

d. Receiver transmits information to

a computer.

3. Uses of a Radio Telescope

a. Detects objects deep in space.

b. Maps the Universe.

c. Searches for intelligent life in space.

4. Largest Radio Telescope in the world is 300

meters wide.

Radio Telescopes

Q. Hubble Telescope (Reflecting Telescope)

1. Launched in 1990 by the space shuttle Discovery.

2. Since Hubble did not have to view space through the

Earth’s atmosphere, it should have produced very

clear images.

3. However there was a mistake in the largest mirror

used in the Hubble Telescope!!!!

4. Images were not as clear as expected.

5. December 1993 first set of repairs were fixed by

astronauts.

6. Has been repaired numerous times since.

a. Hubble Telescope Link/

End of Section 1