Download - Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Compare refracting telescopes with reflecting telescopes.

$: Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Compare refracting telescopes with reflecting telescopes.$
Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 1 Section 2 Telescopes

• Compare refracting telescopes with reflecting telescopes.

• Explain how the atmosphere limits astronomical observations, and explain how astronomers overcome these limitations.

• List the types of electromagnetic radiation that astronomers use to study objects in space.

Objectives

Chapter 1



Telescopes

• A Telescope is an instrument that gathers electromagnetic radiation from objects in space and concentrates it for better observation.

• There are many different types of telescopes.

Chapter 1



Optical Telescopes

• Refracting Telescopes Telescopes that use lenses to gather and focus light are called refracting telescopes. A refracting telescope is shown on the next slide.

• Reflecting Telescope A telescope that uses a curved mirror to gather and focus light is called a reflecting telescope. A reflecting telescope is shown on the next slide.

Chapter 1



Refracting and Reflecting Telescopes

Chapter 1



Optical Telescopes, continued

• Very Large Reflecting Telescopes In some very large reflecting telescopes, several mirrors work together to collect light and focus it in the same area.

Chapter 1


ResourcesChapter menu

• Most optical telescopes used by professional astronomers are housed in buildings called observatories.

Using Optical Telescopes

• Observatories often have dome-shaped roofs that can be opened up for viewing.



• The twin Keck reflecting telescopes have segmented mirrors 10 m wide.

Large Reflecting Telescopes

• Until 2000, these mirrors were the largest reflectors ever used.



Large Reflecting Telescopes

• In 2000, the European Southern Observatory’s telescope, in Chile, consisted

of four 8.2-m reflectors, making it the largest optical telescope in use.



Optical Telescopes, continued

• Optical Telescopes and the Atmosphere The light gathered by telescopes on the Earth is affected by the atmosphere.

• Optical Telescopes in Space To avoid interference by the atmosphere, scientists have put telescopes in space



• The Hubble Space Telescope was launched in 1990 by the space shuttle Discovery.

Hubble Space Telescope

• In December 1993, a team of astronauts repaired the Hubble Space Telescope by installing a set of small mirrors designed to correct images obtained by the faulty mirror.



• Two more missions to service Hubble were carried out in 1997 and 1999.

Hubble Space Telescope

• Among the objects viewed by Hubble after it was repaired in 1999 was a large cluster of galaxies known as Abell 2218.



Nonoptical Telescopes

• Radio Telescopes Radio telescopes detect radio waves. Because radio wavelengths are much larger than optical wavelengths, radio telescopes much be very large.

• Linking Radio Telescopes Astronomers can get more detailed images of the universe by linking radio telescopes together. Working together, the telescopes function as a single giant telescope.



Radio Telescopes

• Unlike visible light, radio waves pass freely through Earth’s atmosphere.

• Because of this, radio telescopes are useful 24 hours per day under most weather conditions.

• Radio waves reaching Earth’s surface strike the large, concave dish

of a radio telescope.

• This dish reflects the

waves to a focal point

where a receiver is located.



Nonoptical Telescopes, continued

• Nonoptical Telescopes in Space Because most electromagnetic waves are blocked by the Earth’s atmosphere, scientists have placed ultraviolet telescopes, infrared telescopes, gamma-ray telescopes, and X-ray telescopes in space.


Chapter 1

Electromagnetic Radiation• The electromagnetic spectrum includes the

entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.


Chapter 1

Four Views of the Crab Nebula• Different type of telescopes collect

electromagnetic radiation at different wavelengths. Astronomers are able to learn a great deal about the Crab Nebula by examining these different images. The images are shown at different scales.



The Electromagnetic Spectrum

• What Is the Electromagnetic Spectrum? The electromagnetic spectrum is made up of all of the wavelengths of electromagnetic radiation.

• Detecting Electromagnetic Radiation Visible light is only a small band of the electromagnetic spectrum. Radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays— are invisible to the human eye.



The Electromagnetic Spectrum


Chapter 1

“Gamma Rays”1x10-12 m


Chapter 1

Individual Atoms! (Xe on Ni)5x10-11 m


Chapter 1

“X-Rays”1x10-10 m


Chapter 1

Width of DNA Helix2x10-9 m


Chapter 1

“Average Virus”7.5x10-8 m


Chapter 1

“Ultraviolet”5x10-8 m


Chapter 1

“Average Bacterium”0.2 – 2.0x10-6 m

StaphylococcusCredit: E. Coli; Rocky Mountain Laboratories, NIAID, NIH


Chapter 1

“Visible” light5x10-7 m


Chapter 1

“Infared”1x10-5 m


Chapter 1

“High Microwave”1x10-2 m


Chapter 1

Height of “Average” Human1.7x100 m


Chapter 1

“Radio/Low Microwave”1x10-2 – 1x103 m