Chapter 18: Section 1AstronomyAstronomy- the study of the universeYear- time for the earth to orbit around

the sunMonth- time for the moon to orbit once

around the earth- Came from the word “moon”Day- time for the earth to rotate once on

its axis

Ptolemy: An earth- Centered Universe

Earth was the center of universe and other planets and sun revolved around the Earth

Copernicus: A Sun-Centered Universe

Sun is the center of the universe and all planets including earth orbit the sun.

Tycho Brahe (TIE koh BRAW uh) : Wealth of Data

Brahe recorded very accurate observations of the movement of bodies in the solar system.

Johannes Kepler: Laws of Planetary Motion

- used Brahe’s data .

-all planets revolve around the sun in elliptical orbits

- Stated the 3 laws of planetary motion still used today

Galileo: Turning a telescope to the sky

Galileo proved that planets, moon and sun are physical bodies like Earth.

Isaac Newton: Laws of Gravity

All objects in the universe attract each other through gravity.

His work helped explain why planets orbit the sun and moons orbit planets.

Edwin Hubble: Beyond the Edge of the Milky Way

In 1924, he proved that other galaxies existed beyond the Milky Way Galaxy.

Section 2: Telescopes

Telescope- instrument that gathers electromagnetic radiation from objects in space and concentrates it for better observation.

Refracting Telescope

- Uses lenses to gather and focus light from distant objects

Reflecting telescope

- Uses a curved mirror to gather and focus light from distant objects

How does the atmosphere affect the images produced by optical telescopes?

The motion of air pollution, water vapor and light pollution distort the images produced by optical telescopes

To avoid interference in the atmosphere, scientists put telescopes in space.

Ex. Hubble Space Telescope- can detect very faint objects in space.

Electromagnetic Spectrum: All wavelengths of electromagnetic radiation

Radiation that can pass through the atmosphere includes radio waves, microwaves, infra red light and ultraviolet light.

Nonoptical Telescopes:

-used to study invisible radiation

Ex. Radio Telescopes- detect radio waves

Nonoptical telescopes in space

-put in space because most electromagnetic waves are blocked by the

earth’s atmosphere

ex. Chandra X-ray Laboratory

Section 3: Mapping Stars

Constellations- sections of the sky that contain recognizable star patterns

As the earth revolves around the sun, location of constellations change from season to season.This sky map shows some of the constellations in the Northern Hemisphere at midnight in the spring. Ursa Major (the Great Bear)is a region of the sky that includes all of the stars that make up that constellation.

Why are different constellations visible in the Northern and southern hemispheres?

Different constellations are visible in the N and S hemisphere because different portions of the sky are visible from the N and s Hemisphere.

Measuring Distance in space

• Stars are much farther away than the planets are.

• Light- year is used to measure their distance.

Light year- Unit of length equal to the distance that light travels in one year

I light year= 9.46 trillion kilometers

How far does light travel in 1 year?

9. 46 trillion kilometers