Objectives 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 Explain how telescopes for nonvisible electromagnetic radiation differ from light telescopes
I. The Value of Astronomy 1. Astronomy the scientific study of the universe b. astronomers have discovered new planets, stars, black holes, and nebulas.
c. studying these objects, they have learned more about the origin of Earth and the processes in the formation of our solar system. d. how stars shine may one day lead to improved or new energy sources on Earth. e. Astronomers may learn how to protect us from potential catastrophes, such as collisions between asteroids and Earth.
II. Characteristics of the Universe A. Organization of the Universe 1. Galaxy: a collection of stars, dust, and gas bound together by gravity 2. The solar system includes: sun, Earth, the other planets, and many smaller objects (asteroids and comets). 3. The galaxy in which the solar system resides is called the Milky Way galaxy.
B. Measuring Distances in the Universe 1. astronomical unit: the average distance between the Earth and the sun; approximately 150 million kilometers (symbol, AU) a. Astronomers also use the speed of light to measure distance. b. Light travels at 300,000,000 m/s. In one year, light travels 9.4607 x 10 12 km, known as a light-year. c. Aside from the sun, the closet star to Earth is 4.2 light-years away.
III. Observing Space A. Electromagnetic Spectrum 1. electromagnetic spectrum: all of the frequencies or wavelengths of electromagnetic radiation. a. Examples: Light, radio waves, and X rays
B. Visible Electromagnetic Radiation 1. Though all light travels at the same speed; different colors of light can be seen through a spectrum. 2. Electromagnetic radiation (shorter or longer than wavelengths of violet or red light) cannot be seen by humans.
C. Invisible Electromagnetic Radiation 1. Invisible wavelengths: infrared waves, microwaves, radio waves, ultraviolet rays, X rays, and gamma rays, and detected only by instruments. 2. In 1852, a scientist named Sir Frederick William Herschel discovered infrared, which means below the red.
IV. Telescopes 1. telescope: collects electromagnetic radiation from the sky and concentrates it for better observation. 2. Telescopes that collect only visible light are called optical telescopes. a. The two types: refracting and reflecting.
A. Refracting Telescopes 1. refracting telescope: uses a set of lenses to bend and focus light from distant objects B. Reflecting Telescopes 1. reflecting telescopes uses a curved mirror to gather and focus light from distant objects
Telescopes, continued The diagram below shows reflecting and refracting telescopes.
C. Telescopes for Invisible Electromagnetic Radiation 1. Scientists have developed telescopes that detect invisible radiation, such as a radiotelescope for radio waves.
V. Space-Based Astronomy 1. In space, Earth s atmosphere cannot interfere with the detection of electromagnetic radiation.
A. Space Telescopes 1. Hubble Space Telescope collects electromagnetic radiation. 2. Chandra X-ray Observatory makes clear images using X rays. 3. Compton Gamma Ray Observatory detects gamma rays from black holes. 4. James Webb Space Telescope will detect infrared radiation after it is launched in 2011.
B. Other Spacecraft 1. The Voyager 1 and Voyager 2 spacecraft investigated Jupiter, Saturn, Uranus, and Neptune. 2. The Galileo spacecraft orbited Jupiter and its moons. 3. The Cassini-Huygens spacecraft will study Saturn s largest moon, Titan.
C. Human Space Exploration 1. Humans went into space in the 1960 s. Between 1969 and 1972, NASA landed 12 people on the moon. 2. The loss of the Challenger in 1986 and the Columbia in 2003, have focused public attention on the risks of human space exploration.
D. Spinoffs of the Space Program 1. Satellites provide information about weather. 2. Others broadcast television signals from or allow people to navigate cars and airplanes (GPS). 3. Medical equipment, like the heart pump, improved based on NASA s research on the flow of fluids.