Our Solar system YouTube - The Known Universe by AMNH

Why does the Earth travel around the Sun? THE LAW OF UNIVERSAL GRAVITATION The strength of the gravitational force between two objects depends upon the mass of the objects and the distance between them. Earth travels around the Sun because it is trapped within the Sun’s gravitational force of attraction.

How do we measure distances in space? ….everything is so far away!!! Light-year - The distance light travels in 1 year Light travels at 300,000 km/s in space, so light travels 9.46 trillion km in one year It takes light from the Sun 8.3 minutes to travel to the surface of the Earth Closest star to our Sun, Proxima Centauri, is about 4 Light-years away Closest galaxy to our Milky Way, Andromeda, is about 2.5 million Light- years away The farthest objects we can observe are more than 10 billion Light-years away Astronomical Unit (AU) – one AU is equal to the distance from the Earth to the Sun, or 93 million miles, or 150 million km

How are the planets of our solar system alike and different? Inner Planets Mercury, Venus, Earth, Mars dense and rocky surfaces smaller than the outer planets “terrestrial planets” Outer Planets Jupiter, Saturn, Uranus, Neptune large and composed mostly of gases all have rings hold more moons due to increased gravitational force “gas giants”

How are the planets of our solar system alike and different? Mercury has no atmosphere and no moons Venus is the hottest planet due to the greenhouse effect of its CO2 atmosphere; it has no moons Earth is 1 AU from the Sun and the only planet with liquid water Mars is red due to the presence of iron in its soil Jupiter is the largest planet with the most gravity Saturn has the largest and most complex ice rings Uranus has a very tilted axis of rotation Neptune is the coldest planet with an average temperature of -200˚ C

What are dwarf planets? Dwarf planets are spherical objects that orbit the Sun, but they do NOT have more mass than the objects in nearby orbits; they are made of rock and ice and are smaller than Earth http://chiawyuen99585.web.officelive.com/dwarf_planets.htm

What are Asteroids? Asteroids Mathilde, Gaspra , and Ida Asteroids – small rocky bodies diameter– a few meters to >900 km in size irregular shapes orbit the Sun in the Asteroid Belt between Mars and Jupiter asteroids can be rich in carbon, stony, or metallic the small moons of other planets may be captured asteroids

What are Meteoroids? Meteoroids – small rocky bodies, smaller than asteroids most are probably pieces of asteroids if the meteoroid burns up in Earth’s atmosphere before it hits the ground, we call it a meteor if a meteoroid enters Earth’s atmosphere and strikes the ground, we call it a meteorite meteor showers happen when Earth passes through the dusty debris that comets leave behind types of meteorites – stony, iron, and stony-iron http://meteorites.asu.edu/meteorite-facts/what-different-types-are-there

What are Comets? Comets (“dirty snowballs”) – small body of ice, rock, and cosmic dust loosely packed together ice is heated when comet passes close to the Sun, and comet gives off gas and dust in the form of a long tail many scientists think comets come from the Oort Cloud and Kuiper Belt http://apod.nasa.gov/apod/ap070331.html Comet Hale-Bop was visible in the sky from May 1996 through September 1997 http://www.classbrain.com/artteensb/uploads/comet_diagram.gif

The Oort cloud extends out beyond the Kuiper Belt (50AU +) and contains comets. The outer edge of the Oort cloud is considered to be the edge of our Solar System. Pluto’s orbit http://www.nasa.gov/pdf/145944main_Kuiper.Belt.Lithograph.pdf The Kuiper Belt is a disc-shaped region beyond Neptune (30 – 50 AU). It contains comets. The Spitzer telescope observes these objects in the infrared.

Technology is essential to science in order to learn about space Pioneer 10 and 11 (1972) – 1st probes to visit outer planets; sampled solar wind; Pioneer 10 traveled past Pluto (1983) Venera 9; Russian (1975) – 1st probe to land on Venus and found surface rocks similar to Earth, surface temperature of 464˚C, severe greenhouse effect Magellan Mission (1989) – mapped Venus and found volcanoes Viking 1 and 2 (1975) – probes had instruments to gather soil on Mars and test it for life Mars Pathfinder Mission (1997) – sent back detailed images of dry water channels on Mars

Technology is essential to science in order to learn about space Voyager 1 and 2 – 1st probe to detect Jupiter’s rings; 1st to fly by 4 gas giants Galileo (1989) – arrived at Jupiter in 1995 and sent a smaller probe to measure Jupiter’s atmosphere; gathered info about moons Cassini Mission (1997) explored Saturn’s moons; deployed a smaller probe called Huygens to study the atmosphere of its Titan moon