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Viewing the Universe
Chapter 26 section 1
Objectives
• Describe characteristics of the universe in terms of
___________________________
• Identify the __________________ parts of the
electromagnetic spectrum.
• Compare ____________ telescopes and
________________ telescopes.
Astronomy
• ______________ - the scientific study of the universe
• _______________ - scientists who study the universe
The Value of Astronomy
By studying astronomy, scientists have learned more about
the origin and
_________________________________Earth.
Potential benefits include the potential discovery of new
_______________ and protection from collisions between
_________________________________
Characteristics of the Universe
• __________________ - the study of the origin, properties,
processes, and evolution of the universe
• ________________ - event that began the universe—NOT
an explosion—__________________________________
Organization of the Universe
Earth is part of our solar system which is contained in the
_______________ galaxy which resides within the
universe along with billions of other galaxies.
• ____________- a collection of stars, dust, and gas bound
together by gravity
Measuring Distances in the Universe
• _____________________________ - the average
distance between the Earth and the sun: ≈ 150 million km
• __________________- the distance that light travels in
one year: 9.46 x 1012 km
Electromagnetic Spectrum
• _________________________ - all of the wavelengths of
electromagnetic radiation; e.g. light, radio waves, X rays
• _________________ - energy that travels through space
as waves
Visible Electromagnetic Radiation
Light is the ____________ visible form of electromagnetic
radiation.
Visible Electromagnetic Radiation
• Light is the ONLY visible form of electromagnetic radiation.
• The shortest wavelengths of visible light are _____________
• The longest wavelengths of visible light are____
• Wavelengths shorter than violet (ultraviolet) or longer than red
(infrared) can not be seen.
Invisible Electromagnetic Radiation
• Ultraviolet means “________________”—includes X rays
and gamma rays.
• Infrared means “__________________”—includes radio
waves and microwaves.
• Invisible EM radiation was discovered by Sir William
Herschel using a thermometer that he placed beyond the
red end of the spectrum.
Telescopes
• ____________- an instrument that collects EM radiation
from the sky and concentrates it for better observation
• Optical telescopes- telescopes that collect only visible
light—2 types:_____________ __________________
Refracting Telescopes
• Refracting telescopes- telescopes that use a set of
____________ to gather and focus light from distant
objects
Problems
• 1. Chromatic Aberration- focusing different _________ at
different _________________
• 2. It is difficult to make very _____ lenses for use in
telescopes—they _______ when supported by their edges.
The amount of light gathered by refracting telescopes is
limited by the size of the objective lens.
Reflecting Telescopes
• Reflecting telescopes- telescopes that use a
______________________ to gather and focus light from
distant objects
Solving Problems
• Mirrors do not focus different colors at different distances
• Mirrors can be made very large by putting many
______________________ together without compromising
the quality of the image
BIG Telescopes
• The largest reflecting telescopes in the world are a pair in
Hawaii—the Keck telescopes. Each one has a mirror that
is _____ m in diameter.
• Astronomers are building the OWL—OverWhelmingly
Large telescope—with a mirror ________ m in diameter.
‘Scopes for Invisible EM Radiation
• There are telescopes for all forms of invisible EM radiation.
• PROBLEMS—(1) Earth’s _____________ blocks much
EM radiation. (2) _________ ___________ prevents
much EM radiation from reaching the Earth’s surface. So,
ground based telescopes must be placed at
_______________________________.
Space Based Astronomy
• When telescopes are out in space, our atmospheric
interference is eliminated.
• Hubble Space Telescope, Chandra X ray Observatory,
Spitzer Space Telescope, James Webb Space Telescope
Space Exploration
• Robotic spacecraft- craft carrying only instruments and
computers—can travel
__________________________________
• Crewed spacecraft- spacecraft that carry humans—have
never been beyond
__________________________________
• NASA wants to send people to Mars but it will be
extremely ________________ and __________________.
Reminders
• Space Shuttle Challenger ___________.
• Space Shuttle Columbia _____________.
Spinoffs of the Space Program
• Technology- all types of satellites, GPS, improved
electronics
• Medical- _____________________
Objectives revisited
• Describe characteristics of the universe in terms of time,
distance, and organization.
• Identify the visible and nonvisible parts of the
electromagnetic spectrum.
• Compare refracting telescopes and reflecting telescopes.