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Solar System. Inner Planets, and Pluto. Solar System. Solar System, plus Sun. Medium Stars. Large Stars. Our Solar System. The Earth, as we know, is just one planet of many in our “small” region of space.
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Our Solar System • The Earth, as we know, is just one planet of many in our “small” region of space. • The collection of planets, asteroids, comets, and other natural objects that are held by the gravity of the sun form our solar system.
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What makes our Solar System? • The central point in the solar system is the Sun. The pull of its gravity is so great that all the planets and objects within a huge distance are held in its sway. • Surrounding the sun are 8 or 9 planets, thousands upon thousands of asteroids, comets, and other astronomical debris. • All together, this forms our solar system.
A little note on measuring. • In astronomy, the distances we will discuss are immense! Special units have been designed just to compare distance. • The Astronomical Unit (AU) is roughly the distance from the Earth to the Sun, about 93 million miles. • We also use light years, or the distance light will travel uninterrupted. • The furthest object in the solar system, the Oort Cloud, is about 100,000 AU from the sun, or about 1 light year. • The closest star (not including the sun )is 4.5 light years.
Mercury • One of the smallest planets in the solar system, Mercury is the closest planet to the sun. • It makes one revolution around the sun every 88 days. The planet rotates once every 58 days. • With a distance of about 33 million miles from the sun, Mercury is rarely seen by people on Earth. • It is only visible right after sunset, or before sunrise.
Mercury • Surface temperatures on the planet range from –292 to 806 F. • Mercury has no moon, and almost no atmosphere. • Mariner 10 satellite mapped the planet in the early 1970s.
Venus, Earth’s Sister • Named after the Roman goddess of love. • Atmosphere is composed almost entirely of carbon dioxide. • Some have predicted that Earth will end up like Venus if global warming goes unchecked.
Venus • There is no moon around Venus. • Average Temp on Venus is around 750 F. • One year on Venus takes 224 days. • One day on Venus takes 243 days!
Mars, the Red Planet • The fourth planet from the sun is named after the Roman god of War. • The red colouring comes from iron oxide in the soil (similar to rust). • Mars also has polar ice caps of carbon dioxide and ice. • These ice caps often melt and reform, depending on the planets position to the sun.
Mars • Olympus Mons (left)is the largest volcano in the solar system. • It stands 17 miles above the surface. • By comparison, Mt. Rainier is less than 3 miles high.
Moons of Mars • Mars has two moons that orbit the planet. • Both are small, and appear almost like asteroids that orbit the planet. • The moons are Phobos (left) and Deimos (right).
Mars • Located 138 million miles from the sun (1.5 AU), Mars takes 687 days to orbit the sun. • One day on Mars lasts 24 hours, 39 minutes, and 35 seconds.
Asteroid Belt • Between Mars and Jupiter, there is a band of asteroids. • The asteroid belt consists of meteors in a whole range of sizes: from small dust particles to asteroids more than 500 miles across.
Jupiter • Jupiter, named for the supreme Roman God, is the largest planet in the solar system. • It is composed primarily of hydrogen, with some helium, and possibly a rocky core of heavier elements.
Jupiter • Located about 480 million miles from the sun, Jupiter takes 11.8 years to orbit the sun. • One rotation of the planet takes only 10 hours! • This high rotation speed causes the planet to bulge slightly at the equator.
Jupiter • Jupiter is about 83,000 miles across, and has a mass of 1.89 x 1027 kg • To put some perspective on that: • Jupiter is about 22 Earths wide • It mass is the same as 318 Earths. • It would take 1321 Earths to fill the volume of Jupiter!
Jupiter • The most well known feature on Jupiter is the Great Red Spot. • This feature is basically a giant hurricane that has lasted for centuries. • It is about the 2 times the size of the Earth! • Wind speeds on Jupiter can be over 220 miles per hour.
Jupiter’s Moons • Jupiter has 63 moons that have been discovered. • Most of these are less than 6 miles across. • The four main moons are referred to as the Galilean moons.
Jupiter’s Moons • Io is one of the most dramatic. • It shows dramatic volcanic activity, including ongoing eruptions and huge geysers erupting miles above the surface. • It is being pulled violently by Jupiter’s immense gravity, constantly pulling the surface of the moon open.
Saturn • The sixth planet, Saturn is named for the Saturnus (Greek equivalent of the Titan Kronos, father of Zeus). • Saturn is primarily composed of hydrogen, with small proportions of helium and trace elements. • It is nicknamed the Ringed Planet, and is the second largest planet in the solar system.
Saturn • Saturn is an oblate spheroid; that is, it is flattened at the poles and bulges at the equator. • Saturn is the only planet of the Solar System that is less dense than water. • That means the planet would literally float in water.
Saturn • Saturn is 9.5 AUs from the sun, or around 880 million miles. • Saturn takes 29.5 years to orbit the sun. • Unusually, different latitudes on Saturn rotate at different rates. • This is between 10 and 11 hours. • It has 57 moons, the largest being Titan.
Saturn • An odd feature on Saturn is a hexagonal cloud feature rotating at Saturn’s North Pole. • This feature was originally seen in the Voyager mission in the early 80s, and is still there when Cassini recently arrived.
Saturn’s Rings • The rings were originally discovered by Galileo, but he didn’t know what they were. • Huygens later idenitified them as a ring. Then Cassini showed they were mutliple smaller rings. • How exactly they were made is still up to much debate.
Saturn’s Rings • Between the rotation of Saturn and the Earth, the rings appear to change appearance as the planets move.
Titan, Saturn’s Moon • Titan is a unique moon in the solar system. • It is 50% larger than Earth’s moon, and is the only moon in the solar system with a dense atmosphere. • We have sent a probe onto the surface to explore the possibility of humans living on Titan.
Two more Moons of Saturn to Note: Iapetus and Mimas • Iapetus: two different colours, odd ridge around equator • Mimas: looks like the Death Star
Uranus • Discovered in 1781 by William Herschel. • Named after the Greek personification of Heaven. • First planet discovered without using the human eye. • Located about 1.8 billion miles out, or 19 AUs.
Uranus • One revolution (year) on Uranus is equal to 84 years on Earth. • It rotates every 17 hours. • Uranus is unique in that it is tilted almost 90 degrees to its orbit. • Its poles face the sun! (one at a time)
Uranus • The reason for Uranus' extreme axial tilt is not known. • It is thought that during the formation of the Solar System, an Earth-sized object collided with Uranus, causing the skewed orientation.
Uranus • The planet is made mostly of Hydrogen, with some helium, methane, and trace amounts of acetylene. • Its diameter is about 8.5 times that of Earth, and it would take 63 Earths to equal its volume.
Uranus • Only one satellite, Voyager 2, has ever been to Uranus. • It then moved on to be the only satellite to ever fly by Neptune.
Moons of Uranus • There are 27 known moons that orbit Uranus. • Since it was discovered by an Englishman, the moons have been named after characters in Shakespeare and Alexander Pope.
Miranda • The appearance of Miranda has confused astronomers since the first photos were observed. • It is believed to have formed similar to Io, and been tugged and pulled by the gravity of Uranus, and that now has stopped. • Other theories?