Download Radio Telescopes

Space Technology Telescopes
Chapter 18 Section 2
Telescopes
• Telescope— an instrument that collects
electromagnetic radiation from the sky and
concentrates it for better observation.
• These can be used by professional
astronomers or amateur stargazers.
Optical Telescopes
• Optical telescopes are the most common
type of telescope.
• Used to study visible light from objects in
the universe.
• Makes it possible to see millions of stars
and other objects in space (You can only
see 3,000 stars without a telescope).
How Does an Optical Telescope
Work?
• An optical telescope collects visible light
and focuses it to a focal point for
observation.
2 Types of Optical Telescopes
• 1. Reflecting
• 2. Refracting
Reflecting Telescope
• Reflecting telescope— an optical
telescope that uses a curved mirror to
gather and focus light from distant objects
• The light is reflected from a curved mirror
to a flat mirror. The flat mirror focuses the
image and reflects the light.
Refracting Telescope
• Refracting telescope— an optical
telescope that uses a set of lenses to
gather and focus light from distant objects
• The objective lens bends light that passes
through it and focuses the light,
Optical Telescopes and the
Atmosphere
• Light gathered by the telescopes on Earth
is affected by the atmosphere.
• Pollution and light from large cities causes
faint objects to be less visible.
• For this reason optical telescopes are
placed on mountaintops where pollution
and lights are less visible.
Optical Telescopes in Space
• Scientists have put telescopes in space to
avoid interference from the atmosphere.
• Ex: The Hubble Telescope is an optical,
reflecting telescope. It uses mirrors.
The Electromagnetic Spectrum
• Scientists discovered that visible light isn’t
the only form of radiation.
• 1852—James Clerk Maxwell proved that
visible light is just part of the
electromagnetic spectrum.
• Electromagnetic spectrum— all of the
frequencies or wavelengths of
electromagnetic radiation
Detecting Electromagnetic Radiation
• Each color of light is a different
wavelength of electromagnetic radiation.
• Humans see from red light to blue light.
• Visible light is only part of the
electromagnetic spectrum.
• Radio waves, microwaves, infrared light, ultraviolet
light, X rays, and gamma rays are all invisible.
Weird Science
Shortly after Marconi invented the
radio in the 1890’s, people became
interested in listening for messages
from intelligent life in the universe. In
1901, a reward of 100,000 franks was
offered to the first person to
communicate with aliens.
Nonoptical Telescopes
• Used to study invisible radiation, light we don’t see.
• The entire electromagnetic spectrum is used
because different types of radiation reveal different
clues about the objects being studied.
• Examples of light we don’s see. It is detected as
heat/radiation: radio waves, x-rays, microwaves,
gamma rays and ultraviolet rays.
• 2 examples of Non-optical Telescopes: Radio
(land-based) and X-ray (Space-based).
Radio Telescopes
• Radio telescopes detect radio waves.
• These are much larger than optical
telescopes because radio waves are 1
million times longer than the optical
wavelength.
Linking Radio Telescopes
• Astronomers link
radio telescopes
together.
• When linked together,
they work like a giant
telescope.
• Very Large Array
(VLA) has 27 radio
telescopes spread
over 30 km.
Nonoptical Telescopes in Space
• Because most
electromagnetic waves are
blocked by the Earth’s
atmosphere, sciences
have placed telescopes in
space.
• Chandra X-Ray
Observatory— spacebased telescope that
detects X-rays.
• Some x-ray telescopes
can detect something the
size of a Frisbee on the
surface of the sun.
KNOW THIS!!
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Reflecting telescopes use mirrors.
Refracting telescopes use lenses.
Optical telescopes collect visible light.
Non-optical telescopes collect radiation that is not visible
to the eye, radio waves for example.
• Land-based telescopes are located on Earth.
• Space-based telescopes are located in space.
• The Hubble is an example of a space-based telescope.
Telescopes are placed in orbit in space to avoid
atmospheric interference like pollution and light from
cities.