The Solar System The Sun Our sun is considered a star. Right now the sun is considered a “main sequence” star, or one can consider the sun to be an “early adult”.
The sun was formed about 4.6 billion years ago and sits at the center of our solar system, around which every planet rotates.
As mentioned in the life science unit, the sun is the source of all heat and energy for life on Earth.
Note it takes about 8 minutes for light from the sun to reach Earth! Sunspots
Sunspots refer to dark areas on the surface of the sun. These areas are “depressed” into the sun’s surface and can be thought of as “storms” on the surface of the sun.
Solar Flare
Refer to bright eruptions of heat and light from the sun.
These eruptions eject atoms, ions, and electrons away from the sun and even toward us on Earth.
If the solar flare is strong enough, it can disrupt communication on Earth by interfering with our wireless signals!
The Inner Planets
The four planets closest to the sun comprise the inner planets of the solar system.
These planets are Mercury, Venus, Earth, and Mars.
Mercury • A small solid planet without an atmosphere and dotted with multiple craters. • Being the closest planet to the sun, the surface temperature can be very hot (973 degrees Celsius) to fairly “cold” (373 degrees Celsius) • Mercury also has the fastest orbit around the sun • No moons orbit this planet Venus • A hot and rocky planet nearly the same size as Earth • Like Mercury, Venus has no moons • Venus has an extremely dense atmosphere of carbon dioxide – Because of the atmosphere, there is a lot of pressure on the surface of Venus which can easily crush manmade objects – “Rain” falls on Venus, but this rain consists of sulfuric acid equivalent to our “acid rain”
Venus • A unique fact about Venus is that the planet spins “backwards” • In addition, Venus has the slowest rotation of any planet. It takes Venus 243 days to turn “once”. – Compare this to Earth, where it takes 24 hours to turn once. – A “year” on Venus is longer than it’s day!
Earth • Our planet, third from the sun in our solar system • One moon orbits our planet. • Atmosphere consists of the following gases: – 78% Nitrogen – 21% Oxygen – 1% Other Gases • We’ll talk more about Earth when we go further into this unit.
Earth’s Magnetic Field • One of the more important facts about Earth is the presence of a magnetic field which deflects the wind from the sun. • If this field was not there, the sun would strip away our ozone layer, allowing a lot more UV light to penetrate our atmosphere. Mars • Mars is about half the size of Earth and rotates around the sun every 687 days. • A martian “day” however, is close to ours, ~24 hours • No liquid water on the surface but there may be ice in the polar regions –It is thought that 3.5-4 billion years ago Mars did have oceans. • Two small moons orbit Mars, Phobos and Deimos
Moons of Mars
The two moons of mars are named Phobos (left) and Deimos (right). The Asteroid Belt Found between the inner and outer planets (i.e. between Mars and Jupiter).
The asteroid belt is a region in the solar system occupied by many asteroids, or irregularly shaped solid objects (rocks) in space.
Some are very large, some are very small.
It is thought that the asteroid belt was a “failed planet”, or that the material in the belt failed to form a planet in the system. The Outer Planets
Mainly consists of the four gas giants and the dwarf planet Pluto. Jupiter • The largest planet in the solar system (11 times the size of Earth), Jupiter consists of a metallic hydrogen core surrounded by a massive amount of hydrogen and helium • Jupiter rotates every 10 hours, giving the planet the fastest spin of any planet in the solar system.
Jupiter Moons
Jupiter has ~67 moons, with four large ones. The names of the large ones are from left to right: Ganymede, Callisto, Io, and Europa. The Great Red Spot • Metaphorically equivalent to being a massive “hurricane” or “storm” on Jupiter. • The great red spot is three times the size of the Earth!
Saturn • The second largest planet in the solar system, Saturn is perhaps best known for its rings • Like Jupiter, Saturn is a gas giant with an atmosphere of about 75% hydrogen and 25% helium • At the center of Saturn is a rocky core • Saturn rotates once every 11 hours and completes an orbit around the sun every 29 years
Saturn’s Rings • The rings on Saturn are composed of ice. • As light passes through the ice orbiting Saturn, it reflects and produces the colors that we associate with Saturn’s rings.
Saturn’s Rings • What an artist thinks Saturn’s rings would look like up close.
Moons of Saturn • Officially, Saturn has 53 moons. • Saturn has one large moon named Titan. • Titan’s environment is thought to resemble that of a primitive Earth. • Therefore, it is thought that given time, life as we know it may one day appear on Titan.
Uranus • The third largest planet, Uranus is 4x the size of Earth • Like Jupiter and Saturn, Uranus is a gas giant due to its large cloud layer. • The natural color of Uranus is light blue. • The planet has 27 “moons”, but none that are really well known or “famous” Tilt of Uranus • The most notable feature of Uranus is how the planet “spins”. • Unlike the rotation of other planets in the solar system, Uranus has a 90 degree “tilt”. Neptune • The last gas giant in the solar system, Neptune takes 165 years to orbit the sun once. • Neptune has 13 moons, with one large one named Triton. • Like Jupiter, Neptune used to have a large spot called the great dark spot • But this spot has been missing since the voyager 2 probe visited the planet back in 1989. Pluto • Demoted a few years ago from a “major planet” to a dwarf planet • Pluto takes 248 years to orbit the sun once and has one major “moon” named Charon • Light from the sun takes 5.5 hours to reach Pluto
Pluto’s Orbit • Unlike the other planets, Pluto has an elliptical shaped orbit. • Depending on where Pluto is, sometimes Pluto can be closer than Neptune is to the sun.