1 What is in outer space? Celestial Objects are any natural objects that move through space. Star:_a huge sphere of gas in space _Nuclear fusion within stars give off enormous amounts of energy such as light and heat Stars are very large big/large_! The Sun The sun_ is just an average_-sized star, but still more than a million times larger in volume than Earth!! Is the closest star to Earth Light from the sun _heats_ Earth and provides light Galaxies: a collection of hundreds of billions of stars The sun is part of the Milky Way galaxy. The Milky Way is shaped like a pinwheel, or a Spiral_ galaxy. Solar System: a star and all the objects that revolve, or orbit, around it_ The sun_ is at the middle of our solar system Eight planets orbit (or revolve around) our sun
2 Planet: a large body made of rock, ice, or gas that orbits a star Inner planets: Mercury, Venus, Earth, Mars Closest to sun, generally warmer in temperature, small and rocky, densest Outer planets: Jupiter, Saturn, Uranus, Neptune Gas giants, lowest in density, farthest from sun, colder The inner planets and outer planets are separated by the _asteroid belt. Asteroid: an irregularly shaped celestial body made of rock or metal Comet: celestial object made of ice, rock, and dust that has a very long orbit
3 The force of gravity keeps all objects in the solar system in orbit around the sun. Year: the time it takes for a planet to make one revolution around the sun Revolution: Earth or a planet moving in its orbit around the sun Earth s year is days long, so its period of revolution _is days. Rotation: A planet spinning on its axis The axis is an imaginary line that runs through a planet s center. One rotation is equal to one complete _day Earth s rotation is almost 24 hours Earth rotates from _WEST to EAST o This makes the sun, moon, planets, stars APPEAR to rotate from East to West. Nighttime: Side facing away from sun Daytime: side of Earth facing sun
4 What causes the Seasons? Different parts of the Earth receive more intense energy from sun than other parts because Earth is _tilted. This makes it hotter/warmer where it is more intense/concentrated Earth s axis is tilted _23.5 degrees_ When Earth is tilted toward_ the sun in the Northern hemisphere, it is summer When Earth is tilted away_ from the sun in the Northern hemisphere, it is winter (**Note, when it is summer in the north, it is winter in the south!! When it is our winter, it is summer in the south! Look at the tilt!) Q: Why is it warmer in the summer? The sun s rays are more concentrated in the north Q: Why are there more hours of sunlight in the summer than the winter? Because of the tilted axis, the sun s direct ray is north of equator, making day s longer as rotate
5 How does latitude affect seasonal changes? Higher latitudes near _poles_ have larger changes in temperature and daylight Lower latitudes near _equator_ have much smaller changes For example, the North Pole gets _24_ hours of daylight during summer, but almost _zero_ hours during winter. The equator gets about 12 hours of daylight all year round. What causes the phases of the moon? Moon does not actually produce its own _light. It reflects_ light from the sun. The _light_ from sun shines on half of the moon at all times, but we don t always see it! Sunlight The change in the illuminated parts of the moon that we do see as the moon orbits Earth is called moon phases.
6 Waxing phases: The part of the moon that we see as illuminated gets larger and larger (right side) Waning phases: The part of the moon that we see as illuminated gets smaller and smaller (left side) Lunar cycle: the passing of one complete set of the Moon s phases (new moon to new moon) Length of lunar cycle is 29 days (about one month_) What causes an eclipse? Eclipse: when the shadow of a celestial object falls on another celestial object Caused when the _sun, Earth, and the moon_ line up perfectly Lunar Eclipse: when the moon falls into Earth s shadow and Earth blocks the sun s light from the moon
7 Solar Eclipse: when the moon blocks the sun s light from viewers at certain location on Earth What causes the tides? Tides: regular motion of ocean water produced by the gravitational attraction between the moon and Earth There are about 12 hours difference from one high tide to the next high tide, or one low tide to the next low tide Low Tide High Tide High Tide Low Tide