2. Astronomy Astronomy the scientific study of the universe Scientists who study the universe are called astronomers Early Astronomers includes: Nicolaus Copernicus Galileo Galilei Tycho Brahe Johannes Kepler

3. Organization of the Universe Galaxy a collection of stars, dust, and gas bound together by gravity The solar system includes the SUN EARTH OTHER PLANETS Many smaller objects such as asteroids and comets The solar system is part of a galaxy. The galaxy in which the solar system resides is called the Milky Way galaxy. The nearest part of the universe to Earth is our solar system.

4. Measuring Distances in the Universe Astronomical Unit the average distance between the Earth and the sun; approximately 150 million kilometers (symbol, AU) Astronomers also use the speed of light to measure distance. Light travels at 300,000,000 m/s. In one year, light travels 9.4607 x 10 12 km. This distance is known as a light-year. Aside from the sun, the closet star to Earth is 4.2 light-years away.

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7. Observing Space Electromagnetic Spectrum Electromagnetic Spectrum all of the frequencies or w avelengths of electromagnetic radiation. Light, radio waves, and X rays are all examples of electromagnetic radiation. The radiation is composed of traveling waves of electric and magnetic fields that oscillate at fixed frequencies and wavelengths.

8. Visible Electromagnetic Radiation Different colors of light have different wavelengths. The human eye can see only radiation of wavelengths in the visible light range of the spectrum. Electromagnetic radiation shorter or longer than wavelengths of violet or red light cannot be seen by humans. The shortest visible wavelength of light are blue and violet, while the longest visible wavelength of light are orange and red.

9. Invisible Electromagnetic Radiation Invisible wavelengths include infrared waves, microwaves, radio waves, ultraviolet rays, X rays, gamma rays, They are detected only by instruments. In 1852, a scientist named Sir Frederick William Herschel discovered infrared, which means “below the red.” Infrared is electromagnetic radiation that has waves longer than waves of visible light. Ultraviolet means “beyond the violet” and has wavelengths shorter than waves of visible light.

12. Telescope an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation. In 1609, an Italian scientist, Galileo, heard of a device that used two lenses to make distant objects appear closer. Telescopes that collect only visible light are called optical telescopes. The two types of optical telescopes are refracting telescopes and reflecting telescopes.

13. Refracting Telescopes refracting telescope a telescope that uses a set of lenses to gather and focus light from distant objects The bending of light is called refraction. Refracting telescopes have an objective lens that bends light that passes through the lens and focuses the light to be magnified by an eyepiece. Reflecting Telescopes reflecting telescopes a telescope that uses a curved mirror to gather and focus light from distant objects

14. SPACE-BASED ASTRONOMY Spacecrafts that contain telescopes and other instruments have been launched to investigate planets, stars, and other distant objects In space, Earth’s atmosphere cannot interfere with the detection of electromagnetic radiation Space Telescopes The Hubble Space Telescope collects electromagnetic radiation from objects in space. The Chandra X-ray Observatory makes remarkably clear images using X rays from objects in space, such as remnants of exploded stars. The Compton Gamma Ray Observatory detected gamma rays from objects, such as black holes. The James Webb Space Telescope will detect infrared radiation from objects in space after it is launched in 2011. Other Spacecraft The Voyager 1 and Voyager 2 spacecraft investigated Jupiter, Saturn, Uranus, and Neptune, and collected images of these planets and their moons. The Galileo spacecraft orbited Jupiter and its moons from 1995 to 2003. The Cassini-Huygens spacecraft will study Titan, Saturn’s largest moon. Scientists hope to learn more about the origins of Earth by studying Titan.

15. Spinoffs of the Space Program Satellites in orbit provide information about weather all over Earth. Other satellites broadcast television signals from around the world or allow people to navigate cars and airplanes. Even medical equipment, like the heart pump, have been improved based on NASA’s research on the flow of fluids through rockets.