The Solar System Astronomy Unit

Motion of the Earth Rotation is the spinning of the earth on its axis. This movement determines the length of a day, 24 hours. Revolution is the movement of one object around another object. This movement determines the length of a year, 365.25 days. Every four years is a leap year.

Seasons Seasons are caused by the tilt of the earth’s axis as the earth revolves around the sun. Vernal equinox is the beginning of Spring. Summer solstice is the beginning of Summer. Autumnal equinox is the beginning of Autumn. Winter Solstice is the beginning of Winter.

What causes Earth to experience different seasons? It rotates on its axis while it revolves around the sun. It revolves on its axis while it rotates around the sun. It is tilted while it rotates around the sun. It is tilted while it revolves around the sun. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

During which season is the axis of the Earth pointed towards the sun? Autumn Spring Summer Winter 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

How does the length of day compare to the length of night during the Vernal Equinox? Day is longer than night. Night is longer than day. The day and night are equal in length. The day and night are not equal in length. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Phases of the Moon The moon is illuminated by the sun. The moon reflects sunlight to the earth. The different phases of the moon is affected by the moon revolving around the earth as the earth revolves around the sun. The complete cycle of phases takes 29.5 days, this is known as a synodic month. Each phase takes about 3.5 days.

Phases of moon New Moon Waxing Crescent First Quarter Waxing Gibbous Full Moon Waning Gibbous Last Quarter Waning Crescent

Our Moon Orbits the earth. Has 1/6 the gravity as earth. Causes the tides on Earth. High tides are 12.5 hours apart Spring tide is the highest high tide (Full & New moon). Neap tide is the lowest high tide (First & Last Quarter moon).

Other Facts About Our Moon The length of rotation is the same as the length of revolution, 27.3 days. We only ever see one side of the moon. The side facing away from the earth is more heavily cratered. The Apollo mission sent seven manned missions to land on the moon.

Which phase occurs when the moon is in between the Earth and the sun? Full moon New moon 1st Quarter moon 3rd quarter moon 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Solar Eclipses In a solar eclipse, the moon is in between the sun and the earth. The complete shadow is the umbra. The partial shadow is the penumbra. Only occur during a new moon.

Lunar Eclipse In a lunar eclipse, the earth is between the sun and the moon. Only occur during a full moon. Eclipses don’t happen every month because there is a tilt in the orbit of the moon around the earth and the moon, sun & earth don’t line up in a straight line.

Use a refracting telescope Use a pinhole camera Use a magnifying glass When studying a solar eclipse, which is the proper method for viewing the sun? Wear sunglasses Use a refracting telescope Use a pinhole camera Use a magnifying glass 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Forces that Hold Earth in Orbit around the Sun Gravity is the attraction between any two objects. Inertia is the tendency of an object to resist change in motion. The balance between gravity and inertia keeps earth in orbit around the sun.

Members of the Solar system Sun (closest star to earth) Planets Moons Asteroids Meteoroids Comets

Inner Planets: Mercury 0.4 AU from the sun. Rotational period 59 Earth days. Revolution period of 88 Earth days. No moon. Average temperature range is 670 K to 103 K. Almost no atmosphere and no water.

Inner Planets: Venus 0.7 AU from the sun. Retrograde rotational period 243 Earth days. Revolution period of 225 Earth days. The day on Venus is longer than a year. No moon. Average temperature range is 700 K. Atmospheric pressure 90 times that of Earth. Atmosphere of sulfuric acid. Large amount of CO2 causing the Greenhouse Effect.

Inner Planets: Earth 1.0 AU from the sun. Rotational period 24 hours. Revolution period of 365.25 days. One moon. Atmosphere 78% nitrogen, 21% oxygen & 1 % carbon dioxide. 71 % of Earth’s surface is covered by water.

Inner Planets: Mars 1.5 AU from the sun. Rotational period 23.9 Earth hours. Revolution period of 687 Earth days. Two moons: Phobos & Deimos. Average temperature range is 144 K to 300 K. Thin atmosphere of carbon dioxide and some water. Largest volcano is Olympus Mons. Polar caps of dry ice.

Asteroid Belt Found between the orbits of Mars & Jupiter. Trojan refers to asteroids or moons that share the same orbit as a larger planet or moon, but does not collide because it orbits.

Outer Planets: Jupiter 5.0 AU from the sun. Rotational period 9.9 hours. Revolution period of 11.9 earth years. 63 moons including Io, Europa, Ganymede & Callisto. Has rings. The Great Red Spot is a major storm on the surface of the planet. Average temperature of 163 K.

Outer Planets: Saturn 9.6 AU from the sun. Rotational period 10.7 Earth hours. Revolution period of 29 Earth years. Has 47 moons including Titan. Has a ring system. Density is less than water. Average temperature of 133 K.

Outer Planets: Uranus 19 AU from the sun. Retrograde rotational period 17.2 Earth hours. Revolution period of 83.7 Earth years. 27 moons. Has rings. Discovered by William Herschel in 1781. Average temperature is 78 K.

Outer Planets: Neptune 30 AU from the sun. Rotational period 17 Earth hours. Revolution period of 164 Earth years. 13 moons. Has rings. Discovered by John Galle in 1846. Average temperature is 73 K.

Planet diameters Mercury - 4879 km Venus – 12,104 km Earth – 12,756 km Mars – 6794 km Jupiter – 142,982 km Saturn – 120,536 km Uranus – 51,118 km Neptune – 49,528 km

Oort Cloud The Oort Cloud is the area surrounding the solar system where the comets are found. Comets are dirty snow balls. Comets have a head (nucleus & coma) and a tail. Halley’s comet appears every 76 years.

Meteors Meteoroids are pieces of rock from object such as asteroids that fly through space. Meteors are meteoroids that are burning up in the earth’s atmosphere (shooting stars). Meteorites are meteoroids that have landed on the earth’s surface.

Models of the Solar System Geocentric model placed the earth in the center of the solar system (Aristotle & Ptolemy). Heliocentric model placed the sun in the center of the solar system and that all the planets orbited the sun (Copernicus). Newton stated that gravity kept the planets in orbit around the sun.

Theories of the Formation of the Solar System Nebular Theory states that the sun formed from a cloud of gas and dust and that collapsed because of the gravity. As the cloud collapsed, it formed into a flat, rotating disk. Planetesimals formed when small particles collide and stick together (accretion). The radiation from the sun burned off most of the gases of the inner planets

Formation of the Moon Earth collided with a large body. The debris began to clump together to form the moon. The moon began to orbit the earth, being pulled in by the earth’s gravity.

Kepler’s Laws of Planetary Motion LAW 1: The orbit of a planet/comet about the Sun is an ellipse with the Sun's center of mass at one focus.

Kepler’s Laws of Planetary Motion LAW 2: A line joining a planet/comet and the Sun sweeps out equal areas in equal intervals of time.

Kepler’s Laws of Planetary Motion LAW 3: The squares of the periods of the planets are proportional to the cubes of their semi major axes. This means, the longer the orbital period, the farther the distance from the sun.

Chapter 19 Test – The Solar System November 20th or 21st.

Review Questions: Which forces are responsible for keeping the planets in orbit around the sun? (gravity & inertia) What causes the phases of the moon? (the relative positions of the Earth, moon & sun) Which planet has the Great Red Spot? (Jupiter)

Review Questions: Which planet has a longer day than its year? (Venus) Which planet lies on its side as it rotates? (Uranus) What happens when the moon goes between the sun and the earth, casting a shadow on the earth? (solar eclipse)

Review Questions: Which planet is the largest in our solar system? (Jupiter) Where do you find all of the comets in our solar system? (Oort cloud) What is located between Mars and Jupiter? (Asteroid Belt)

Review Questions: What do you call a piece of rock that is burning up as it goes through the Earth’s atmosphere? (meteor) Which planet has the most moons? (Jupiter) Which planet has the Greenhouse Effect? (Venus)

Review Questions: What is the shape of planetary orbits according to Kepler’s First Law of Motion? (ellipse) What causes the seasons on Earth? (tilt of the Earth’s axis) Which theory explains the creation of the solar system? (Nebular theory)

Review Questions: Why do we only ever see one side of the moon? (the length of rotation & revolution are the same) Nate Hoff weighs 240 pounds on Earth. What is his weight on the moon? (40 pounds-1/6 the gravity)

Review Questions: Which model of the solar system states that the sun is in the center of the solar system and everything revolves around it? (Heliocentric) What do we call the highest, high tide? (Spring Tide)