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A GUIDE TO OUR SOLAR SYSTEM FOR THE CLUELESS In the summer of 1969 I was ten years old. On a warm night in July my parents woke me up around midnight to watch (on our black and white TV) Neil Armstrong walk on the moon. Apollo 11 was launched from the Earth on July 16th, landed on the Moon on the 20th, and returned to Earth on July 24, 1969. Neil Armstrong was the Commander, Edwin Aldrin, Lunar Module Pilot, and Michael Collins, Commander Module Pilot. I looked forward to this event for about a week, which is a long time when you are ten years old. I always loved gazing at the stars, but after that sleepless night our solar system, the galaxies, and what lies beyond became even more mysterious. Unfortunately, I never had the time to take Astronomy in college. My schedule never permitted it. But when my god-son began to question me about the stars in the sky, I explained them to him as best as I could. Hold on to your seat, we are going into outer space... OUR SOLAR SYSTEM THE SUN Our Solar System is made up of the Sun, nine planets that revolve around it, 43 moons which revolve around the planets, and a band of space rocks called the Asteroid Belt. Our Solar System is heliocentric, which means the Sun is in the center. A long time ago it was believed that the earth was in the center. In order from the Sun the planets are: Mercury, Venus, Earth, Mars, (Asteroid Belt), Jupiter, Saturn, Uranus, Neptune, and Pluto. The Sun holds all the planets in their positions in space and provides light and heat. The Sun is a ball of fiery gases of helium and hydrogen. It does not burn like a fire would on Earth; the Sun burns by turning hydrogen into helium. Solar flares are jets of gases that shoot up from the Sun. Our friend the Sun is the hottest thing in the Solar System. Its center reaches 15 million degrees centigrade. Ouch! The Sun's surface is much cooler at about 6000 degrees centigrade. This is 60 times hotter than boiling water. The Sun is so large that it would take over a million Earths to fill a hollow Sun. It is bigger than all the other planets put together. LIGHT Light is the fastest thng in the Universe, always traveling at the same speed. What speed? I don't know, VERY FAST. Light is so fast that it could go around the Earth 7.5 times in a second. A "light year" is the distance light can travel in one Earth year. Light hours, light minutes, and light seconds are used to measure things which are closer in space. Stars are so far away that there had to be a name invented to measure the distance between them--that is when "light years" was created. The Moon is 1.5 light seconds away, the Sun 8 light minutes away, Pluto 6 light hours away. And the nearest star to the Earth is 4.5 light years away. THE MOON The Moon shines brighter than anything in the night sky (except during the New-Moon, but we will get there later). It appears to shine, but it does not make its own light; it is reflecting light from the Sun. The Moon is the Earth's closest neighbor, but it is still a long way away. A journey to the Moon would take as long as going around the Earth about ten times. (Even if you were riding with Dave). The Moon orbits around the Earth every 27 and 1/3 days. It always keeps the same half facing the Earth. It wasn't until the 1960s, when a spacecraft orbited the moon and sent pictures back to us, that we were shown the farside of the moon. The Moon is much smaller than the earth. It would take 80 moons to weigh as much and 50 Moons to fill a hollow ball the size of the Earth. Mercury and Venus are the only two planets that do not have moons. While Earth has only one, Saturn and Jupiter each have 16. Why the Moon Changes Shape We see the Moon change its shape every night. It grows from a thin sliver into a bigger crescent, then a half-Moon, which becomes a Full-Moon. It slowly shrinks back again going the other way to a crescent and so on. These different shapes are called phases. The Moon is not really changing shape; it just appears that way from the earth because we see different parts of it light up as it orbits around the Earth. When the Moon is directly between the Earth and the Sun we do not see any of the illuminated side. This phase is called a New-Moon. When the Earth is between the Sun and the Moon we see the Full-Moon, which is all of the lit up side. When on the moon, the Earth can been seen in the sky, and it seems to change its shape and go through phases from the moon. (As you can see in the picture on Amy's Home page). If you were on the moon the sky would always be black, even in the daytime. The moon has days and nights that are each 14 Earth days long. The Sun shines all the time during the day and makes the Moon hotter than boiling water. (100 degrees centigrade). At night, the Moon is dark and very cold, much colder than ice. (Zero degrees centigrade). For quick weight loss, a trip to the Moon would appear to be the answer. Everything on the moon weighs less that on Earth, about 1/6 less. In your spacesuit on Earth you might weigh 300 pounds (135kg), but on the moon you would weigh in at 50 pounds (23kg). This is because the moon has less gravity than the earth. That is why you might remember seeing the astronauts jumping around on the moon. There they could jump higher than on earth--I am sure it was fun. The Moon is a totally silent place, as noises can not be heard because there is no air to carry sounds. There is no weather on the Moon; no wind, rain or water there. This means the footprints left by the astronauts will never be blown or washed away. Neither will a whole mess of stuff they left up there, including parts of the lunar module and the land rovers. The Moon is covered by millions of craters. Some are so large that we see them from Earth. These craters were believed to be made by stray space rocks called meteorites, which crashed into the Moon millions of years ago. MERCURY Mercury is a small planet, only slightly larger than our moon. The surface resembles that of our Moon as it is covered with craters and stony soil. There is no air or water on Mercury. It is the closest planet to the sun, making it very hot during the day. (Not on my list of vacation spots). VENUS Venus is the hottest planet in the Solar System. It reaches 480 degrees C. which is hot enough to make things glow a dull red color. Thick clouds of sulfuric acid cover Venus. These clouds never clear to let the sunshine through. These clouds help contribute to the heat on Venus as they trap in the Sun's heat. Heat can get through the clouds to the surface of the planet, but cannot get out again. The air on Venus is made of carbon dioxide gas. It is 60 times thicker than the air in Earth. Venus spins in the opposite direction to the other planets. It takes 243 Earth days to spin one time. This is longer than the time Venus takes to orbit the sun (225 Earth days), so a day on Venus is longer than a year. Here in Connecticut, Venus is the first and brightest light in the night sky and can be seen from April to October almost directly South in the evening sky. I saw her last night and she reminded me that, as weird or inconsistent as life can be for us humans, the planets are very dependable and orderly. It is often a comforting thought for me. MARS Mars is sometimes called the "Red Planet" because it is made up of red rocks and dust. Even the sky is pink on Mars from the red dust. It is about half the size of Earth. Mars has ice caps at the North and South poles. Mars has 2 tiny moons named Deimos and Phobos. Phobos orbits Mars three times a day. Mars has the largest volcano in the Solar System. All of the volcanoes on Mars are dead and no longer erupt. The Asteroid Belt The Asteroid Belt is made of thousands of rocks going round the sun in space between Mars and Jupiter. Some asteroids are the size of pebbles; some as big as buildings; a few larger than cities; and my guess is that out there is one bigger than the State of Rhode Island. (Just a New England joke). Asteroids may be the remains of a planet that exploded millions of years ago. JUPITER Jupiter and Saturn are very much alike. Perhaps so much alike that soon there will be a car manufacturer called Jupiter. They are both made up of cold gases and liquids: Hydrogen, Helium, methane ammonia and water. Jupiter is the giant of the Solar System, about 2.5 times more massive than all of the planets combined. It would take 1400 Earths to fill a sphere the size of Jupiter. A huge storm has been blowing on Jupiter for hundreds of years. It is called the Giant Red Spot for obvious reasons. Two Earths could fit into Jupiter's Giant Red Spot. Voyager 1 gave NASA beautiful photographs of Jupiter in 1979. Voyager also took pictures of Jupiter's two moons, Io and Europa. SATURN Saturn is circled by a series of rings . They orbit around the middle of the planet. The rings are made of pieces of rock and ice. They stretch out far from Saturn, about the same distance as our Moon is from Earth. I hear they make good cars up there too. URANUS Uranus is a giant gas planet. It appears greenish-blue because of the chemical composition. It is circled by nine rings made of ice and rocks. These rings were only discovered by scientists in 1977. Uranus spins around in a different way than all the other planets. It seems to be lying down, as opposed to the others which appear to stand up. Due to this lying down position, Uranus has very strange days. Days and nights are 42 Earth years long on some parts of Uranus. NEPTUNE Neptune is so far from the sun that is takes 165 Earth years to orbit the sun. PLUTO Pluto, the last planet in our Solar System takes 247 Earth years to orbit around the Sun. Until 1915, Neptune was thought to be the last planet of the Solar System. An astronomer, Percival Lowell, worked out that there should be another planet beyond Neptune. He named it planet X and searched for many years but did not find it. In 1930, another astronomer, Clyde Tombaugh, was taking photographs of stars. He noticed a stray "star" in a picture which he could not identify. It was realized that he had photographed the mysterious Planet X. It was later named Pluto. STARS Stars are giant balls of hot fiery gases, like our Sun. They appear smaller than the Sun and planets because they are much farther away. Stars are not all the same; they come in a variety of colors, shapes, sizes, temperatures, and brightness. The Sun is a common type of star. All stars form in huge clouds of gas and dust. After time these gases combine together and begin to heat up as a clump. Eventually the dust and gases get so hot that they start to glow and "shine." It is then that this combination has become a star. Stars last for thousands of millions of years, but they do not stay the same forever. Changes occur as they age. Stars are so far away that we measure the distance between them and between the earth in "light years". (Discussed earlier). While the nearest star is 4.5 light years away, many stars are hundreds of light years away. Our Sun will spend most of its life as a yellow star, about 10,000 million years. Eventually, it will expand and change from yellow to red and become a Red Giant Star. Red Giants are a hundred times larger than the Sun, but cooler and brighter. This type of star is at the end of its life. After a star like our Sun turns into a Red Giant, it slowly cools down and shrinks. The outer layers will separate and go off into space. This new "thing" is called a White Dwarf Star. Stars larger than the Sun also become Red Giants. A Supernova is a massive Red Giant star that has expanded and exploded. The explosion is called a Supernova. Supernovas occur with stars that have masses greater than five times that of our Sun. For several months Supernovas may shine 10 billion times brighter than a normal star. A Supernova leaves behind a Black Hole which acts like a gigantic cosmic vacuum cleaner that sucks in anything that goes near it, including comets, planets, and clouds of gas. Not even light can escape the gravitational pull of a Black Hole's intensity. As a result they remain black and invisible and disappear forever. (IMHO, that is probably where all the lost socks go). Supernovas are rare, occurring only about once per century in a galaxy the size of the Milky Way. Most Supernovas leave behind a cloud of gas, and a tiny spinning star called a Neutron Star. If a black hole and a visible star revolve around one another, the black hole with its massive gravitational field, pulls gases from the visible star into itself. When this happens the gas emits strong X-rays which astronomers can detect. GALAXIES Our galaxy measures about 80,000 light years across. Stars are not really scattered randomly about the Universe, they are gathered in enormous groups each containing hundreds of millions of stars. These groups we call galaxies. Our Sun is a star in the galaxy called the Milky Way--which is shaped like a spiral. (I prefer the dark chocolate Milky Way bar, if you can find them). More stars are located in the middle of the galaxy than around the outside. As you haved guessed by now, galaxies do not just hang out in space, they slowly spin. The complete spin is called a galactic year. The Milky Way takes 225 Earth years to spin one time. There are millions of galaxies in the Universe. Some look similar to ours, others are different in shape. COMETS Comets are made up of gases, ice and dust. Only about 20 come close to the Earth each year, but only a few are bright and large enough to be seen without a telescope. About every ten years we may be lucky enough to see a large comet. These comets can be viewed from Earth for weeks or months. Some comets are regular visitors to our Solar System, and they will appear and reappear after a certain number of years. Halley's Comet returns every 76 years. It was last seen by Earthlings in 1986, and is due to return in 2026. Comets do not shine by their own light. They reflect the light of the Sun and become visible to us when they get as close to the Sun as Saturn. The comet's tail is always pointed away from the Sun. In 1893, a comet had a tail so long that it stretched the length of the distance from the Sun to Mars. Comets leave bits of dust from their tails in space. We see them as shooting stars or meteors. Is there life outside our solar system you ask? I don't know, ask this dude! Space Travel Would you travel in the Space Shuttle given the chance? Yes! No Way! Don't know. Results