Ch 2 – Earth’s Place in Space 2.1 – The Universe 2.2 – The Sun’s Family 2.3 – Earth’s Family 2.4 – The Year

Section 2-1 The Universe Universe - It consists of everything that ever existed or that still is physically present. Most of it is an endless sea of empty space with clusters of stars called GALAXIES Astronomical Distance – Light-year The distance light travels in one year.  Lights travels at 300,000 km per second  1 Light-year equals 9.5 trillion kilometers – 5.9 trillion miles  Closest Star – Proxima Centauri 4.3 Light-years  Closest galaxy – Andromeda 2 million Light-years

Stars and Galaxies A galaxy is a star cluster with a million to a trillion stars Galaxies are found in groups called “Galactic Clusters. Our Milky Way galaxy and 28 others make up what is called the “Local Group”

Electromagnetic Waves Electromagnetic Spectrum  Light is the only visible wave that can be seen.  All these waves travel at the same rate.  The study of these waves emitted by a star enables astronomers to determine the properties like temperature, relative brightness, chemical composition, size and distance from Earth.

Doppler Effect Effects both light and sound Frequencies will sound higher in pitch (shorter) as an object moves toward you. Frequencies will sound lower in pitch (longer) as an object moves away from you. This information is used to determine if a star is moving away from or towards Earth.

Section 2.2 The Sun’s Family Our solar system is ≈6 Billion years old The solar system began as a cloud of dust and gases. Gravitational forces caused the cloud to collapse into a spinning disk. Planets – As of today, our solar system contains 8 planets and their moons. Planets reflect light ; not radiate Diameter Relationships Sun – 1,390,000 km Earth - 12,750 km Jupiter – 142,800 km

Two Types of Planets Inner Planets – Terrestrial (solid, rocky) Mercury, Venus, Earth, Mars Outer Planets – Jovian (Small core with gaseous outer core and very large) Jupiter, Saturn, Uranus, Neptune

Interplanetary Debris Comets - composed of frozen gases with dust. Can have large orbits around our Sun. Asteroids – clumps of rocky material. They orbit between Mars and Jupiter. This debris may have tried to become a planet but Jupiter’s strong gravitational field broke it up. Meteoroids – Solid rocklike objects that orbit the Sun and sometimes strike Earth. Meteors – What meteoroids are called when they enter the Earth’s atmosphere. Meteorites – Meteors that actually hit the Earth’s surface.

Life in the Solar System Earth’s Biosphere is unique Contains liquid water, the right temperature, and the correct mix of oxygen, nitrogen, and water vapor to support carbon-based life forms. Mercury and Venus are too hot Mars does not receive enough heat energy and has little or no water. The Jovian planets are mainly have gases of hydrogen, helium with methane and ammonia surrounding a small rocky core.

Section Earth’s Family Moons – None around Mercury or Venus At last count there are 61 moons around Jupiter Tides – Our moon’s gravity pulls on the Earth; creating a bulge on the surface but the bulge is greater on the oceans.

Section 2.4 – The Year One year is equal to days (365 days 6 hours 9 min 9.64 s) The length of day and night changes because of the earth’s tilt on its axis; 23.5° All these variations are responsible for the changing weather patterns and seasons. June 21 - Summer solstice Dec 21 - Winter Solstice March 21 – Spring Equinox Sept 23 – Fall Equinox