Download Chapter 21: Stars, Galaxies, Universe Section 1: telescopes

Chapter 21: Stars, Galaxies, Universe
Section 1: telescopes
• Key concepts: What are the regions of the
electromagnetic spectrum? What are
telescopes and how do they work? Where are
most large telescopes located?
• Key terms: Telescope, electromagnetic
radiation, visible light, wavelength, spectrum,
optical telescope, refracting telescope, convex
lens, reflecting telescope, radio telescope,
observatory
Telescopes
• A telescope is a device that makes distance
objects appear closer.
• Galileo was not the first to use a telescope,
but he helped make it famous.
Electromagnetic radiation
• Electromagnetic radiation is a
form of energy that can travel
through space in the form of
waves. Visible light is an
example of electromagnetic
radiation.
• Other forms: radio, infrared,
ultraviolet, x-rays, gamma
(listed from long wavelength to
short wavelength)
• Wait, what’s a wavelength???
• http://www.youtube.com/watch?v=snNwE6tx
xP0
Electromagnetic spectrum
• Wavelength – distance between the crest (high
point) of a wave and the crest of the next wave
• Spectrum – range of light colors with different
wavelengths
• Radio, infrared, visible light, ultraviolet, x-rays,
gamma
• ROYGBIV
• What kinds of radiation do you experience every
day?
Types of telescopes
• Telescopes are instruments
that collect and focus light
and other forms of
electromagnetic radiation.
• Optical telescopes –
telescope that uses lenses
or mirrors to collect and
focus visible light
– Two major kinds: refracting
and reflecting
Refracting telescopes
• Uses convex lens to gather and focus light
• Convex lens is a piece of transparent glass, curved
so that the middle is thicker than the edges
• Light enters the telescope through a large
objective lens at the top. It focuses the light at a
certain distance (focal length). The larger the
lens, the more light collected.
• The smaller lens at the lower end of the
telescope is the eyepiece lens. It magnifies the
image produced by the objective lens.
Reflecting telescope
• Uses a curved mirror to collect and focus light.
The curved mirror in a reflecting telescope
focuses a large amount of light into a small
area (just like the refracting telescope).
• The largest telescopes are all reflecting
telescopes.
Radio telescope
• Used to detect radio waves from objects in
space. Most have curved, reflecting surfaces.
They focus radio waves the same way a mirror
focuses light waves. The larger it is, the more
waves it can collect.
Other telescopes
• Can detect infrared, uv, x rays, gamma rays
• Many large optical telescopes are equipped
with systems that improve the quality of the
images. They use computers and lasers.
Observatories
• Observatories are buildings that contain one or
more telescopes.
• Many are located on mountains or in space.
• Earth’s atmosphere makes stuff in space look
blurry, so putting an optical telescope on a
mountaintop eliminates some light from the
cities and the sky is clearer.
• Radio telescopes do not need to be put on
mountaintops.
•
Telescopes
in
space
Hubble Space Telescope is a
reflecting telescope with a
mirror 2.4 meters in diameter
(big big big). It orbits Earth
above the atmosphere, so it
can produce very detailed
images.
• Hottest objects in space give
off x rays. Some telescopes
pick these up, like the
Chandra X ray observatory.
• 2003 – NASA launched Spitzer
Space Telescope – measures
infrared.