1. Comets
1.1. What Is A Comet?
1.1.1. Comets are loose collections of ice, dust, and small rocky particles whose orbits are usually very long, narrow ellipses.
1.2. A Comet's Head
1.2.1. Clouds of gas and dust form a fuzzy outer layer around a comet called a coma.
1.2.2. The nucleus is the solid inner core of a comet.
1.2.3. The brightest part of a comet, the comet's head is made up of the nucleus and coma
1.3. A Comet's Tail
1.3.1. As a comet approaches the sun and heat sup, some of its gas and dust stream outward, forming a tail.
1.3.2. Most comets have two tails-a gas tail and a dust tail.
1.3.2.1. Both tails usually point away from the sun.
1.4. Origins of Comets
1.4.1. Most comets are found in one of two distant regions of the solar system
1.4.1.1. The Kuiper Belt
1.4.1.1.1. Doughnut-shaped region that extends from beyond Neptune's orbit to about 100 times Earth's distance from the sun.
1.4.1.2. The Oort Cloud
1.4.1.2.1. Spherical region of comets that surrounds the solar system out to more than 1,000 times the distance between Pluto and the sun.
2. Asteroids
2.1. Rocky objects that are too small and too numerous to be considered full-fledged planets are called asteroids.
2.2. Most asteroids revolve around the sun between the orbits of Mars and Jupiter.
2.2.1. This region of the solar system is called the asteroid belt.
2.3. Most asteroids are small-less than a kilometer in diameter.
2.4. Scientists now hypothesize that the asteroids are leftover pieces of the early solar system that never came together to form a planet.
2.5. Some asteroids have very elliptical orbits that bring them closer to the sun than Earth's orbit.
3. Meteors
3.1. A chunk of rock or dust in space.
3.2. Meteoroids come from comets or asteroids.
3.3. How they form
3.3.1. Some meteoroids form when asteroids collide in space.
3.3.2. Others form when a comet breaks up and creates a cloud of dust that continues to move through the solar system.
3.4. When a meteoroid enters Earth's atmosphere, friction with the air creates heat and produces a streak of light in the sky-a meteor.
3.5. Meteoroids that pass through the atmosphere and hit Earth's surface are called meteorites.
4. The "Goldilocks" Conditions
4.1. Conditions needed by "life as we know it."
4.1.1. Earth has liquid water and a suitable temperature range and atmosphere for living things to survive.
5. Earth at the Center
5.1. Since geo is the Greek word for 'Earth," an Earth-centered model is known as a geocentric system.
5.1.1. In a geocentric system, Earth is at the center of the revolving planets and stars.
5.1.1.1. Ptolemy supported the Geocentric system
6. Sun at the Center
6.1. This sun-centered model is called a heliocentric system.
6.1.1. In a heliocentric system, Earth and the other planets revolve around the sun.
6.1.1.1. This model was not well received in ncient times
6.1.2. Nicolaus Copernicus further developed the heliocentric model.
6.1.2.1. Copernicus was able to work out the arrangement of the known planets and how they move around the sun.
6.1.2.2. Copernicus correctly placed the sun at the center of the planets. But he incorrectly assumed that the planets travel in orbits that are perfect circles.
6.1.2.2.1. In the 1500s Tycho Brahe and his assistants made much more accurate observations.
6.1.3. Galileo used the newly invented telescope to make discoveries that supported the heliocentric model.
7. Modern Discoveries
7.1. Today we know that the solar system consists of...
7.1.1. the sun
7.1.2. the planets and their moons
7.1.3. several kinds of smaller objects that revolve around the sun
8. The Sun
8.1. The sun's interior consists of the...
8.1.1. core
8.1.1.1. sun produces an enormous amount of energy in its core
8.1.1.1.1. sun's energy comes from nuclear fusion
8.1.2. the radiation zone
8.1.2.1. region of very tightly packed gas where energy is transferred mainly in the form of electromagnetic radiation.
8.1.3. the convection zone
8.1.3.1. outermost layer of the sun's interior.
8.2. The Sun's Atmosphere
8.2.1. The Photosphere
8.2.1.1. inner layer of the sun's atmosphere
8.2.1.2. sphere that gives off visible light
8.2.2. The Chromosphere
8.2.2.1. middle layer of the sun's atmosphere
8.2.2.2. "color sphere"
8.2.3. The Corona
8.2.3.1. During a total solar eclipse, the outer layer that looks like a white halo around the sun is called the corona.
8.2.3.2. Extends into space for millions of kilometers
8.3. Features on the Sun
8.3.1. Sunspots
8.3.1.1. areas of gas on the sun's surface that are cooler than the gases around them
8.3.2. Prominences
8.3.2.1. Huge, reddish loops of gas
8.3.3. Solar Flares
8.3.3.1. The energy heats gas on the sun to millions of degrees Celsius, causing the gas to erupt into space. These eruptions are called solar flares
8.3.4. Solar Wind
8.3.4.1. formed when the corona gradually things into streams of electrically charged particles
9. Planets
9.1. Mercury
9.1.1. The orbit of Mercury has the highest eccentricity of all the Solar System planets. Mercury is similar in appearance to the Moon: it is heavily cratered with regions of smooth plains, has no natural satellites
9.1.2. Diameter (km)
9.1.2.1. 4,879 kilometers
9.1.3. Period of Rotation (Earth Days)
9.1.3.1. 59
9.1.4. Average Distance From Sun (km)
9.1.4.1. 58,000,000
9.1.5. Period of Revolution (Earth Years)
9.1.5.1. 0.24
9.2. Venus
9.2.1. Classified as a terrestrial planet, it is sometimes called Earth's "sister planet" because they are similar in size, gravity, and bulk composition. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. Venus has the densest atmosphere of all the terrestrial planets, consisting mostly of carbon dioxide
9.2.2. Diameter (km)
9.2.2.1. 12,104
9.2.3. Period of Rotation (Earth Days)
9.2.3.1. 243
9.2.4. Average Distance From Sun (km)
9.2.4.1. 108,000,000
9.2.5. Period of Revolution (Earth Years)
9.2.5.1. 0.62
9.3. Earth
9.3.1. Home to millions of species, including humans, Earth is the only place in the Universe where life is known to exist.
9.3.2. Diameter (km)
9.3.2.1. 12,756
9.3.3. Period of Rotation (Earth Days)
9.3.3.1. 1
9.3.4. Average Distance From Sun (km)
9.3.4.1. 150,000,000
9.3.5. Period of Revolution (Earth Years)
9.3.5.1. 1
9.4. Mars
9.4.1. Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is also referred to as the "Red Planet" because of its reddish appearance, which is caused by iron oxide that is prevalent on its surface. It is the site of Olympus Mons, the highest known mountain in the Solar System, and of Valles Marineris, the largest canyon. Of all the planets in the Solar System other than Earth, Mars is the most likely to harbor liquid water, and thus to have life.
9.4.2. Diameter (km)
9.4.2.1. 6,794
9.4.3. Period of Rotation (Earth Days)
9.4.3.1. 1.03
9.4.4. Average Distance From Sun (km)
9.4.4.1. 228,000,000
9.4.5. Period of Revolution (Earth Years)
9.4.5.1. 2
9.5. Jupiter
9.5.1. It is a gas giant. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium. An especially interesting feature of Jupiter's atmosphere is its Great Red Spot, a storm that is larger than Earth. Jupiter's four largest moons: Io, Europa, ganymede, and Callisto.
9.5.2. Diameter (km)
9.5.2.1. 143,000
9.5.3. Period of Rotation (Earth Days)
9.5.3.1. 0.41
9.5.4. Average Distance From Sun (AU)
9.5.4.1. 5.2
9.5.5. Period of Revolution (Earth Years)
9.5.5.1. 12
9.6. Saturn
9.6.1. Saturn has a thick atmosphere made up of mainly hydrogen and helium. Saturn's atmosphere also contains clouds and storms. Saturn is the only planet whose average density is less than that of water. Saturn has the most spectacular rings of any planet. Saturn's largest moon, Titan, is larger than the planet Mercury.
9.6.2. Diameter (km)
9.6.2.1. 120,500
9.6.3. Period of Rotation (Earth Days)
9.6.3.1. 0.45
9.6.4. Average Distance From Sun (AU)
9.6.4.1. 9.6
9.6.5. Period of Revolution (Earth Days)
9.6.5.1. 29
9.7. Uranus
9.7.1. Uranus looks blue-green because of traces of methane in its atmosphere. Like the other gas giants, uranus is surrounded by a group of thin, flat rings, although they are much darker than Saturn's rings. Uranus's axis of rotation is tilted at an angle of about 90 degrees from the vertical.
9.7.2. Diameter (km)
9.7.2.1. 51,120
9.7.3. Period of Rotation (Earth Days)
9.7.3.1. 0.72
9.7.4. Average Distance From Sun (AU)
9.7.4.1. 19.2
9.7.5. Period of Revolution (Earth Days)
9.7.5.1. 84
9.8. Neptune
9.8.1. Neptune is a cold, blue planet. Its atmosphere contains visible clouds. Neptune has a Great Dark Spot which was probably a giant storm.
9.8.2. Diameter (km)
9.8.2.1. 49,530
9.8.3. Period of Rotation (Earth Days)
9.8.3.1. 0.67
9.8.4. Average Distance From Sun (AU)
9.8.4.1. 30
9.8.5. Period of Revolution (Earth Days)
9.8.5.1. 164
9.9. Pluto
9.9.1. Pluto has a solid surface and is much smaller and denser than the outer planets. Pluto has three known moons. The largest of these, Charon, is more than half of Pluto's size. It used to be thought of as the ninth planet in our solar system, but recently scientists classify it as a dwarf planet.
9.9.2. Diameter (km)
9.9.2.1. 2,390
9.9.3. Period of Rotation (Earth Days)
9.9.3.1. 6.4
9.9.4. Average Distance From Sun (AU)
9.9.4.1. 39.2
9.9.5. Period of Revolution (Earth Days)
9.9.5.1. 248