The Solar System: The Solar System The Nebular Theory: The Nebular Theory The solar system began as a huge cloud of dust and gas, which later condensed to form the sun and its planets. The Sun Forms First: The Sun Forms First The nebula was composed of hydrogen and helium.
A star exploded in a supernova and new elements entered our nebula.
Shock waves from the supernova explosion disrupted our nebula and it began to collapse.
As gravity pulled in it spun faster and flattened into a disk, which would become our sun.
After millions of years, it became dense and hot enough for fusion to begin. The Planets Form: The Planets Form Gases and matter continued to spin around the sun.
Gravity caused them to pull into clumps of matter which became protoplanets. Inner Planets: Inner Planets Protoplanets near the sun became so hot, most of their gases burned boiled away.
The inner, hotter planets were left as collections of metal and rock.
The inner planets are Mercury, Venus, Earth and Mars.
The Gas Giants: The Gas Giants The protoplanets farther from the sun were less affected by the sun’s heat.
They retained their gases and grew to enormous sizes.
The gas giants are Jupiter, Saturn, Uranus and Neptune. Moons: Moons As the newly formed planets began to cool, clumps of matter formed around them.
These clumps became moons or satellites which revolved around the planets.
Asteroid Belt: Asteroid Belt Between Mars and Jupiter, small clumps of matter formed asteroids.
These rocklike objects are in a region known as the asteroid belt.
Comets: Comets Farther our in space, near the edge of the solar system a huge cloud formed.
This cloud is believed by some astronomers to be the home of comets. Motions of the Planets: Motions of the Planets The Greeks noticed that although the stars appeared to move across the night sky, their position relative to each other was constant.
The Greeks also noticed that some of the stars appeared to wander among the other stars.
The Greeks called these objects, planets, or wanderers. Ptolemy: Ptolemy In the second century AD, the Greek scientist Ptolemy proposed a theory that placed Earth at the center of the universe.
He also proposed that all objects in the sky traveled in orbits around an unmoving Earth.
He proposed that the orbits were circular. Nicolaus Copernicus: Nicolaus Copernicus Between 1500 and 1530 the Polish astronomer Copernicus developed a new theory about the solar system.
He proposed that the Earth and the other planets revolved around the sun.
He reasoned that the planets revolved in the same direction.
He stated that each planet took a different amount of time to complete their revolution in a perfect circle. Johannes Kepler: Johannes Kepler The sixteenth-century German mathematician and astronomer Johannes Kepler discovered something new. He proposed that the planets orbit in an ellipse, or oval orbit (egg shaped).
Today scientists know Kepler was correct. Law of Inertia: Law of Inertia An object’s motion will not change unless that object is acted on by an outside force.
A moving object will not change speed or direction unless an outside force causes a change in its motion. Sir Isaac Newton: Sir Isaac Newton Newton hypothesized that planets, like all other objects would move in a straight line unless some force causes them to change their motion. He reasoned that the force was the gravitational pull of the sun. Inertia and gravity: Inertia and gravity The elliptical orbit is caused by two factors: gravity and inertia.
Inertia causes the planet to move in a straight line.
Gravity pulls the planet toward the sun.
When the two combine, the planet moves in an elliptical orbit. Period of Revolution: Period of Revolution A planet’s period of revolution is called a year on that planet.
For example, Mercury takes 88 days to revolve around the sun and Pluto takes about 248 Earth years. Period of Rotation: Period of Rotation All planets rotate, or spin, on their axes.
The time it takes a planet to complete one rotation is called its period of rotation.
The Earth takes 24 hours to complete a period of rotation.
Mercury takes almost 59 Earth days to rotate once on its axis. Mercury: Mercury Mercury –Faster than a Speeding Bullet: Mercury –Faster than a Speeding Bullet Mercury is a rocky planet without almost no atmosphere or weather. In 1975 Mariner 10 found the many craters unchanged.
Mercury moves quickly around the sun at the pace of 48 km per second and was named after the speedy messenger of the Roman gods.
Mercury rotates 3 times for every 2 revolutions. Sunrise occurs every 175 Earth-days making it one of the hottest and coldest planets in the solar system. Exploration of Mercury: Exploration of Mercury Mariner 10 flew by Venus and Mercury in 1973-1975 and sent back images. Venus: Venus Venus – Greenhouse in the Sky: Venus – Greenhouse in the Sky Venus was named for the Roman goddess of beauty and love.
Venus rotates east to west, retrograde rotation.
Why Is Venus So Different From Earth?: Why Is Venus So Different From Earth? In early days, the sun was cooler.
Venus may have had oceans. (Remains of coastline and beds can still be detected.)
As sun grew hotter, the water evaporated into the atmosphere.
Water vapor and later carbon dioxide in the atmosphere created a greenhouse. Greenhouse Effect on Earth: Greenhouse Effect on Earth The Earth’s atmosphere acts like a greenhouse.
This effect helped life evolve and survive.
Burning of fossil fuels, such as coal and oil, add carbon dioxide to the atmosphere.
Some scientists fear Earth may suffer the fate of Venus.
Exploration of Venus: Exploration of Venus Astronomers believed Venus to be the twin of Earth until explored by the Soviet spacecraft Venera, Pioneer Venus Mariner 2 (1962), and Mariner 5 (1967) which found land forms due to once active volcanoes. Clouds are made of sulfuric acid. The atmosphere is very thick.
Mars: Mars Mars – the Rusty Planet: Mars – the Rusty Planet Mars known as the rusty planet.
Mars was named after the Roman god of war.
Mars has two moons, Phobos (fear) and Deimos (terror).
Exploration of Mars: Exploration of Mars Viking I and II landed on Mars in 1976 and found that soil is covered in iron oxide.
Mariner 4 (1964-65) and Mariner 6 & 7 (1969) were pass by flights.
Mariner 9 (1971) was an orbiter.
The Rover landed in 2004.
Phoenix Lander will arrive in May 2007 to search for water.
Life on Mars?: Life on Mars? Scientists found no sign of life on Mars.
There is a possibility life once existed since frozen water can be found in the northern icecap. The southern icecap has frozen carbon dioxide.
Since the atmosphere is so thin, Mars temperature always stays below 0 degrees C.
The Asteroid Belt: The Asteroid Belt The Asteroid Belt: The Asteroid Belt Asteroids are made of rock, metal or a combination of the two.
Asteroids are sometimes called the minor planets. The largest is Ceres (100 km) which is classified as a dwarf planet.
It is believed this matter did not form a planet due to the strong gravitational pull of Jupiter. Death of Dinosaurs?: Death of Dinosaurs? One theory states that the collision of a huge asteroid 65 million years resulted in the extinction of dinosaurs and almost 90% of all other life on Earth.
It is believed the force of the collision was 10,000 times greater than the force of all nuclear weapons on Earth.
Jupiter: Jupiter Jupiter: Jupiter Our sun contains 99.8% of all the matter in our solar system.
Jupiter contains 70% of all the remaining matter in the solar system.
Romans named this planet after the king of the Gods. Jupiter – Almost a Star: Jupiter – Almost a Star Jupiter is main primarily of hydrogen and helium gases.
The core reaches 30,000 degrees C (5 times the surface of the sun).
If Jupiter had grown larger during formation, it would have become a star.
Jupiter gives off more heat than it receives from the sun. Galileo: Galileo Galileo plunged into Jupiter's crushing atmosphere on Sept. 21, 2003. The spacecraft was deliberately destroyed to protect one of its own discoveries - a possible ocean beneath the icy crust of the moon Europa.
The spacecraft was the first to fly past an asteroid and the first to discover a moon of an asteroid. It provided the only direct observations of a comet colliding with a planet.
Galileo was the first to measure Jupiter's atmosphere with a descent probe and the first to conduct long-term observations of the Jovian system from orbit. It found evidence of subsurface saltwater on Europa, Ganymede and Callisto and revealed the intensity of volcanic activity on Io.
New Horizons arrived at Jupiter in 2007. Features of Jupiter: Features of Jupiter Astronomers have observed a Great Red Spot which is hurricane-like.(20,000 yr old)
Jupiter has a small solid core.
Jupiter has s liquid hydrogen ocean which causes a magnetic field (magnetosphere).
Jupiter has at least 62 moons. (Io, Europa, Gannymede and Callisto) Saturn: Saturn Saturn – A World of Many Rings: Saturn – A World of Many Rings Saturn has seven major rings (A-G) made of icy particles ranging in size from 1/1000mm to 100km in diameter.
Saturn, like Jupiter, is made mainly of hydrogen and helium gases and has violent storms. It is the least dense planet.
Saturn spins so fast, it flattens at the poles and bulges at the equator.
Saturn has 33 known moons.
Uranus: Uranus Uranus – A Planet on its Side: Uranus – A Planet on its Side Uranus was named for the father of Saturn.
Uranus was discovered by Sir William Herschel in 1781.
Voyager 2 found Uranus is covered by a thick cloud of hydrogen, helium and methane and an ocean of superheated water.
The axis of Uranus is tilted at a 90 degree angle.Uranus has rings and 27 known moons. Triton – a moon of Neptune: Triton – a moon of Neptune Neptune – the Mathematician’s Planet: Neptune – the Mathematician’s Planet The orbit of Uranus is affected by Neptune.
Mathematicians predicted the location as early as 1845.
Neptune was named for the Roman god of the sea.
Neptune, like Uranus, is covered by clouds of hydrogen, helium and methane.
Voyager found Neptune to have 13 moons and 5 rings. Triton orbits in a retrograde pattern. Pluto: Pluto Pluto – a Dwarf Planet: Pluto – a Dwarf Planet When discovered, Neptune did not orbit as predicted. Although astronomer Percival Lowell predicted the existence of Pluto in the early 1900’s, it was not located until 1930.
Pluto was named for the Roman god of the underworld.
The discovery still did not explain the orbit patterns of Uranus and Neptune. Pluto was too small to account for the change. When Charon, a moon, was found in 1978, this helped solved the riddle. Reclassification of Pluto: Reclassification of Pluto Planets must
A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape, and (c) has cleared the neighbourhood around its orbit.
Pluto is considered a dwarf planet because it does not clear the neighborhood and is not a satellite. Other Dwarf Planets: Other Dwarf Planets The mass of Pluto and its moon is too small to account for the irregular orbits of Uranus and Neptune.
Ceres and Xena are the other two dwarf planets. Comets: Comets The Oort Cloud is a collection of ice,gas and dust located 15 million km from the sun.
Sometimes these comets are pulled toward the sun. As they near the sun, they begin to melt which forms a cloud around its core. Composition of a Comet: Composition of a Comet The core of a comet is called the nucleus.
The cloud of dust surrounding the nucleus is called the coma. Together they form the head.
The solar wind of the sun blows the coma outward into a long tail. The tail of an incoming streams behind, an outgoing streams in front.
Most of 100,000 comets in the solar system orbit over and over.
Halley’s comet returns every 75-79 years. Some take thousands of years. Meteoroids, Meteors and Meteorites: Meteoroids, Meteors and Meteorites Meteoroids are chunks of metal or stone that orbit the sun.
When the meteoroid rubs against the gases in the atmosphere, friction causes it to burn, producing a streak of light known as a meteor or shooting star.
Most burn up in the atmosphere, a few survive to strike the Earth and are called meteorites.
These meteorites can cause craters. Life in the Solar System: Life in the Solar System The two conditions necessary for life are moderate temperatures and liquid water.
7.5 million km closer to sun would have been too hot.
1.5 million km farther away and the water would be frozen. Rocketry: Rocketry Rocketry is based on Newton’s Third Law of Motion – Every action produces an equal and opposite reaction.
In a reaction engine, the rearward blast of gases causes the rocket to shoot forward. The force of this movement is called the thrust. History of Rocketry: History of Rocketry The Greeks and Romans used steam to move toys.
The Chinese developed rockets for use in war in the year 1000. They were hollow bamboo filled with gunpowder. When ignited, gases shot out the end causing a forward reaction. Escape Velocity: Escape Velocity In order to escape the Earth’s gravitational pull, the rocket must achieve the proper velocity.
The escape velocity depends on the mass of the planet and the distance of the rocket from the planet’s center.
Tsiolkovsky (Russian, 19th c) predicted a solid fuel would not be able to accomplish this feat. A solid burns too quickly. It cannot maintain the thrust. Dr. Robert H. Goddard: Dr. Robert H. Goddard In 1926, Dr. Goddard combined gasoline with liquid oxygen and launched a small rocket.
He eventually developed multistage rockets in which empty fuel containers are dropped off.
Today the fuel is a combination of liquid hydrogen and liquid oxygen. Probes to Inner Planets: Probes to Inner Planets In 1962, Mariner 2 probed Venus. Later Magellan studied Venus. Galileo was crushed in the atmosphere in 2003. New Horizons, on the way to Pluto, sent back images in 2007.
Mars was studied by Mariner 4 in 1965, Mariner 7 in 1969 and Mariner 9 in 1971.
Mariner 10 flew past Mercury in 1974.
Viking 1 (1975) and 2 landed on Mars.
Rover landed on Mars in 2004.
Probes to Outer Planets: Probes to Outer Planets Pioneer 10 studied Jupiter in 1973 and sent back 300 photographs. Pioneer 11 later studied Jupiter. Both are now beyond the solar system.
The Galileo mission to Jupiter ended in 2003.
Voyager 1 and 2 flew by Jupiter (1983) Saturn and Uranus and Neptune (1990s). Voyagers left our solar system at the end of the century.
New Horizons arrived at Jupiter in 2007. It will travel on to Pluto and the Kuiper belt.