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Solar System Reese Measuring distance in space • Astronomers use astronomical units to measure distance in space because distances in space are VERY BIG. • 1 AU = 150,000,000 kilometers away (Distance between Earth and Sun) • If distances are even farther, then astronomers use lightyears. A light-year is the distance light travels in one year. • Light travels at 300,000 km/sec • 1 light-year = 10 trillion km • The next closest star (Alpha Centauri) is 4.3 light-years away! Measuring distance in space • Milky Way is 100,000 light-years across and has 100 billion stars. • The next galaxy is 60,000 light-years away. How did it all begin? Big bang proponents suggest that some 10 billion to 20 billion years ago, a massive blast allowed all the universe's known matter and energy to begin to expand. Our solar system which is located in one of the spiral arms of the Milky Way galaxy, began about 4.6 billion years ago when a cloud of dust, hydrogen gas, helium, and other elements drifted in our galaxy and began to condense. As more and more cloud began to clump together, the intense pressure and weight of the gases resulted in nuclear fusion and our sun formed first in the center. Once ignited, the Sun's powerful solar winds began to blow. These winds, which are made up of atomic particles being blown outward away from the Sun, slowly pushed the remaining gas and dust out of the Solar System. Big Bang Continued… With no more gas or dust, the planets, minor planets, moons, comets, and asteroids stopped growing. The inner planets which are much closer to the Sun, were impacted more by the solar winds and it gave them less time to grow. The outer planets grew larger and their gravity had time to accumulate massive amounts of gas, water, as well as dust. What is a Solar System? • Our solar system is a group of interacting celestial bodies(planets, moons, asteroids, comets, meteoroids, minor planets) that orbit around the Sun due to its gravitational pull on them. What is a galaxy? • A galaxy is a group of millions or billions of stars, gas, and dust, held together in space by the force of gravity. Our solar system belongs to the Milky Way galaxy. The Milky Way galaxy is a barred spiral-shaped galaxy. Geocentric vs Heliocentric • Geocentric = Earth is at the center of the revolving planets and stars. – Greeks (Ptolemy) • Heliocentric = Earth and other planets revolve around the sun. – Copernicus, Galileo, Kepler Geocentric Theory Scientist Copernicus • Nicolò Copernico; (19 February 1473 – 24 May 1543) was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe. Kepler • Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer, and astrologer, and key figure in the 17th century scientific revolution. He is best known for identifying the motion of the planets around the sun as an ellipse. Galileo • Galileo Galilei 15 February 1564– 8 January 1642)was an Italian physicist, mathematician, astronomer and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism. He is known as "the Father of Modern Science." SUN • Our sun is a star at the center of our solar system. Our sun supports life on Earth, affects seasons, climate, weather, and currents in the ocean. • Our sun is a medium size star (yellow main sequence star). SUN • The sun is basically a ball of gas (plasma). The main gases that it consists of are hydrogen and helium but it has other trace elements. Why is the sun’s gravity so strong? • The sun’s gravity is the strongest force in our solar system. It is strong enough to hold ALL of the planets and comets in orbit. The reason the sun has such a high gravity is due to its immense mass. • The sun contains 99.86 percent of the mass of the solar system! The sun is 330,000 times the mass of Earth. Example: If you weigh 80 lbs on Earth, you would weigh 2,244 pounds on the surface of the sun. What are some sun statistics? • 1,384,000 km in diameter • 149.6 million km away from Earth • It takes 25 Earth days for it to rotate on its axis Where does the sun’s energy come from? • The sun gets its energy from nuclear fusion.. • Nuclear fusion occurs when hydrogen atoms bond together to form helium. This bonding is the source of energy for the sun. • Nuclear fusion can only be achieved when temperatures are EXTREMELY HIGH (15 million degrees Celsius) and EXTREMELY HIGH pressure exists. • The sun is currently about 5 billion years old and it has enough energy to last another 5 billion years. Nuclear Fusion SUN Layers Sun’s 4 main layers • CORONA: the outermost atmosphere layer (stands for crown in latin). The corona’s job is to eject out a stream of electrically charged particles called solar wind. You can only see this layer during a total eclipse of the sun. • CHROMOSPHERE: (inner atmosphere). The chromospheres' job is to create the reddish color for the sun. Sun’s 4 main layers • PHOTOSPHERE: visible surface layer. The photosphere’s job is to produce light. The visible light we see on Earth comes from this layer. Even though this layer is very hot, it is cooler than the core and therefore sunspots sometimes appear on this layer. • CORE: innermost layer. Nuclear fusion occurs at the core. The only place in the sun that is hot enough and has enough pressure for the process to happen. Sun’s unique features • Sunspots: areas of gas on the sun found of the photosphere that are cooler than the gases around them (we see as dark spots). Sunspots are magnetic storms with magnetic fields that occur in pairs. They can last for days or weeks before they disappear. Sunspots have an 11 year cycle. Magnetic Field Protection Sun’s Unique Features • Prominences: reddish loops of gas that connect different parts of sunspot regions. Prominences occur in the chromosphere. Solar Flare • Solar Flares: explosions of hydrogen gas that release large amounts of energy . Solar flares can lead to increases in solar wind (from corona) which can reach the Earth’s atmosphere and disrupt the magnetosphere. Disruptions in the magnetosphere can lead to electrical, satellite, radio, and telephone problems on Earth. Solar flares occur in the chromosphere. What is a solar eclipse? • A solar eclipse is when the Sun is fully or partially covered due to the moon (new moon) passing between the Sun and Earth in just the right alignment. Gravity • Gravity is the force that causes two particles to pull towards each other. For objects on Earth, the pull is towards the center of the Earth. • The amount of gravity one object exerts on another depends on the mass and distance between the two objects. The more mass an object has (like the Sun) the stronger its gravity. The more distance between two objects, the weaker the gravitational pull between them. Mass • The amount of matter (particles) that an object is made of. Mass never changes even if gravity changes. Weight • Weight is the mass of an object plus the force of gravity pulling down on the object. • Weight DOES change when gravity changes. If you are on a planet with less gravity, you “weigh” less. If you are on a planet with more gravity, then you “weigh” more. Inertia • An object in motion will stay in motion unless a force acts on it. An object at rest will stay at rest unless a force acts on it. Why planets orbit the sun What is a planet? • A planet is defined as a large spherical body that revolves around the sun in the solar system. How do the planets differ? • Planets differ in size, composition, mass, force of gravity, distance from the sun, temperature, and number of natural satellites. What do all planets have in common? • All our planet’s reflect light. They all revolve and stay in orbit because of gravity. They all have inertia. The amount of gravity a planet as is directly related to the mass of the planet. More massive planets have larger gravitational pulls. All planets have a core. All planets rotate on their axis. How many planets are in our solar system? • Scientist currently agree that there 8 planets and 1 dwarf planet. They are categorized into the inner and outer planets based on their characteristics. • The first four are called the inner planets. They are small and rocky. • The following four are very large in comparison to the first four and are gaseous. Planet Images (NOT TO SCALE) INNER PLANETS MERCURY JUPITER VENUS SATURN EARTH URANUS OUTER PLANETS MARS NEPTUNE What are satellites? • A satellite is any natural or artificial object that revolves around an object in space. Our satellites revolve around Earth. Man made satellites are used to photograph and relay information for weather systems, support our telephone and media communications, measure our atmosphere, spy and provide GPS location. • A space station is a satellite that people can live in for long periods of time. What is a moon? • A moon is a natural satellite of a planet. A satellite is an object that stays in orbit around the planet. • The Earth has one moon. The moon’s surface is thick with dust and has many rocks of various sizes. • The moon is lit by sunlight bouncing off of it (reflecting). The shape appears to change (moon’s phases) as it revolves around the Earth every 27.3 days. Moon • Notable features of the moon are its plains (made out of volcanic rock), its lunar mountains, and craters. • The moon has no water and no atmosphere (no air). Temperatures range from -172 degrees Celsius to 114 degrees Celsius. • The mass of the moon is 1/6 that of Earth therefore it has a lower gravitational pull. • Moon is 384,400 km away from Earth and is 3,476 km in diameter. Moon’s Features Moon causes tides on Earth • The moon causes the tides on Earth. The tides occur due to the pull of the moon’s gravity. What is a lunar eclipse? • An eclipse of the Moon is caused by Earth passing between the Sun and the Moon aligned in a specific way. Comet • Comets: a mixture of frozen gases and tiny dust particles that are sometimes called “dirty snowballs.” • Nucleus = solid portion of a comet (inner layer). • Coma = halo of dust and gas that forms around the nucleus of a comet. Comets have “tails” that may extend millions of km into space! They face away from the sun. • Like other objects in space, comets orbit the sun. Comets have an elliptical shaped orbit. • Most comets exist in the Oort Cloud > 50 AU away(long period) and Kuiper Belt (30 AU away)(short period). • A famous comet know as Halley’s comet was last seen in 1986. It revolves around the sun every 76 years. Comet Kuiper Belt What are ASTEROIDS? • Asteroids: they are the next largest objects in our solar system after the (sun, moons, and planets) and look like lumpy potatoes. Asteroids are large rocks that are sometimes called “minor planets.” Some think that asteroids are remnants of a planet that never formed. Most asteroids revolve around the sun between the orbits of Mars and Jupiter. This is known as the asteroid belt. Have asteroids stuck Earth? Many astronomers and biologists think a big comet or asteroid caused the dinosaurs to go extinct 65 million years ago, when a 10- to 15-kilometer wide uncontrolled flying object whacked the Caribbean Sea, forming a crater about 180 kilometers in diameter near the Yucatan Peninsula. The heat of impact with the atmosphere and surface caused a firestorm over much of North America. Then vast clouds of dust and smoke shaded the planet, causing a cold spell that terminated the million-century plus reign of the dinosaurs. Yucatan Peninsula Meteoroid and friends… • Meteoroid = a chunk of rock or dust in space that usually comes from a comet or a asteroid. • Meteor = A meteoroid that enters the Earth’s atmosphere and burns up. They are also known as shooting stars. • Meteorite = If the meteoroid does not burn up and hits the Earth’s surface. Crater Images Types of Craters • Some craters are volcanic craters. The top of the volcano collapses and leaves a hole. This is called a “caldera.” Usually, these fill up with water and form a lake. • Impact craters happen when “impactors” crash onto the surface of the celestial body and leave a hole. How do they know? • Scientist identify impact craters by identifying certain key clues: – Shape of crater (round shape) – Overturned rocks at the edge of the crater – Highly fractured rocks that have been ejected out in rays outside the craters – Chemistry of the rocks in the crater (rare elements) Ejecta Famous Craters on Earth (~100) • Barringer Crater— Arizona (1200 meters in diameter) • Vredefort Crater –Africa (250 - 300 km in diameter) LARGEST CRATER ON EARTH • Sudbury Crater ---Canada (200 km in diameter) • Chicxulub Crater—Mexico (170 km in diameter) • Woodleigh Crater—Australia (60 km in diameter) Changes in Craters • Over time; ice, water, and wind weather and erode craters which lead to changes from their original appearance. • Some craters have been filled with water or soil. Craters on Moon • Only impact craters are found on moon. • Estimated 3 million impact craters • No atmosphere on the moon allows so many meteorites to strike the surface. • Largest craters on the moon are called Aristarchus, Copernicus, and Tycho. • Satellites have helped map both sides of moon. Moon Craters