Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes...

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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

Transcript of Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes...

Page 1: 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

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Chapter 1 Section 2 Telescopes

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

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Chapter 1 Section 2 Telescopes

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

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Chapter 1 Section 2 Telescopes

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

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Chapter 1 Section 2 Telescopes

Refracting and Reflecting Telescopes

Chapter 1

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Chapter 1 Section 2 Telescopes

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

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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.

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ResourcesChapter menu

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

Large Reflecting Telescopes

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

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ResourcesChapter menu

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.

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Chapter 1 Section 2 Telescopes

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

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ResourcesChapter menu

• 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.

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ResourcesChapter menu

• 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.

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Chapter 1 Section 2 Telescopes

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.

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ResourcesChapter menu

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.

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Chapter 1 Section 2 Telescopes

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.

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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.

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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.

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Chapter 1 Section 2 Telescopes

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.

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Chapter 1 Section 2 Telescopes

The Electromagnetic Spectrum

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Chapter 1

“Gamma Rays”1x10-12 m

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Chapter 1

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

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Chapter 1

“X-Rays”1x10-10 m

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Chapter 1

Width of DNA Helix2x10-9 m

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Chapter 1

“Average Virus”7.5x10-8 m

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Chapter 1

“Ultraviolet”5x10-8 m

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Chapter 1

“Average Bacterium”0.2 – 2.0x10-6 m

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

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Chapter 1

“Visible” light5x10-7 m

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Chapter 1

“Infared”1x10-5 m

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Chapter 1

“High Microwave”1x10-2 m

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Chapter 1

Height of “Average” Human1.7x100 m

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Chapter 1

“Radio/Low Microwave”1x10-2 – 1x103 m