Chapter 1 Section 2 Telescopes Objectives Compare refracting

$Chapter 1 Section 2 Telescopes Objectives • Compare refracting telescopes with reflecting telescopes. •$

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

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

$Chapter 1 Section 2 Telescopes Optical Telescopes • Refracting Telescopes that use lenses to$

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

$Chapter 1 Section 2 Telescopes Optical Telescopes • Refracting Telescopes that use lenses to$

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

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.

Using Optical Telescopes • Most optical telescopes used by professional astronomers are housed in buildings called observatories. • Observatories often have dome-shaped roofs that can be opened up for viewing. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Large Reflecting Telescopes • The twin Keck reflecting telescopes have segmented mirrors 10 m wide. • Until 2000, these mirrors were the largest reflectors ever used. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

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 Copyright © by Holt, Rinehart and Winston. All rights reserved.

Hubble Space Telescope • The Hubble Space Telescope was launched in 1990 by the space shuttle Discovery. • 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. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Hubble Space Telescope • Two more missions to service Hubble were carried out in 1997 and 1999. • Among the objects viewed by Hubble after it was repaired in 1999 was a large cluster of galaxies known as Abell 2218. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.

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. Copyright © by Holt, Rinehart and Winston. All rights reserved.