The Solar System PDF

THE SOLAR SYSTEM  What exactly is our solar system? Our solar system is the collection of planets, moons, asteroids, and other celestial bodies that orbit around the sun. It is a vast and complex system that has fascinated astronomers and scientists for centuries. The sun is at the center of...

THE SOLAR SYSTEM  What exactly is our solar system? Our solar system is the collection of planets, moons, asteroids, and other celestial bodies that orbit around the sun. It is a vast and complex system that has fascinated astronomers and scientists for centuries. The sun is at the center of the solar system and it is by far the largest object. It contains about 99.86% of the total mass of the solar system and it is the source of all the light and heat that sustains life on Earth. The eight planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. They range in size from the small and rocky Mercury to the massive gas giants like Jupiter and Saturn.  Why is it called “solar system”? There are many planetary systems in the universe, with planets orbiting host stars. Our planetary system is called “the solar system” because we use the word “solar” to describe things related to our star, after the Latin word for Sun, "solis."  The Milky Way – our galaxy If you’re on a dark countryside hill some night, look up at the sky. Arcing overhead, a faint band of light may appear that looks like milk spilled across the sky. The ancient Romans called the band via lacteal, which means “milky road” or “milky way.” The band of light that you see isn’t actually milk, of course—it’s a galaxy. A galaxy is a huge bunch of stars clustered together in space. Our solar system—which includes the sun, Earth, and eight other planets— is part of this galaxy, called … you guessed it … the Milky Way.  Can people see the Milky Way with the naked eye? Observing the night sky is a humbling and awe-inspiring experience, but many people wonder, “Can I see the Milky Way with my eyes?” Yes, you can see the Milky Way with your eyes. To witness it in all its glory, it’s essential to be in a dark sky area, away from the light pollution of cities and towns. Under ideal conditions, the Milky Way appears as a milky band of light arching across the sky, which is how it got its name.  What kind of galaxies are there? Astronomers classify galaxies into three major categories: elliptical, spiral and irregular. These galaxies span a wide range of sizes, from dwarf galaxies containing as few as 100 million stars to giant galaxies with more than a trillion stars. ELLIPTICAL Elliptical galaxies have shapes that range from completely round to oval. They are less common than spiral galaxies. Unlike spirals, elliptical galaxies usually contain little gas and dust and show very little organization or structure. The stars orbit around the core in random directions and are generally older than those in spiral galaxies since little of the gas needed to form new stars remains. SPIRAL Our Milky Way is one example of a broad class of galaxies defined by the presence of spiral arms. These galaxies resemble giant rotating pinwheels with a pancake-like disk of stars and a central bulge or tight concentration of stars. Spiral galaxies are surrounded by halos, mixtures of old stars, star clusters, and dark matter – invisible material that does not emit or reflect light but still has a gravitational pull on other matter. The youngest stars form in gas-rich arms, while older stars can be found throughout the disk and within the bulge and halo. IRREGULAR Irregular galaxies have unusual shapes, like toothpicks, rings, or even little groupings of stars. They range from dwarf irregular galaxies with 100 million times the Sun’s mass to large ones weighing 10 billion solar masses. Irregular galaxies born from galaxy interactions or collisions typically host a mix of older and younger stars, depending on the characteristics and composition of the original galaxies.  What is the closest galaxy to our Mily Way? The Andromeda galaxy, our Milky Way's closest neighbor, is the most distant object in the sky that you can see with your unaided eye — but only on a clear night from a location with a very dark sky. The galaxy is a beautiful spiral, but one fact you may not be aware of: We’re safe for a few billion years, but Andromeda is headed our way and on a collision course with the Milky Way.  What is a planet? This seemingly simple question doesn't have a simple answer. Everyone knows that Earth, Mars and Jupiter are planets. But both Pluto and Ceres were once considered planets until new discoveries triggered scientific debate about how to best describe them – a vigorous debate that continues to this day. The most recent definition of a planet was adopted by the International Astronomical Union in 2006. It says a planet must do three things: 1.It must orbit a star. 2.It must be big enough to have enough gravity to force it into a spherical shape. 3.It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.  MERCURY The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth's Moon. From the surface of Mercury, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times brighter. Mercury spins slowly on its axis and completes one rotation every 59 Earth days. Mercury was named after the Roman god of travel. Mercury's surface temperatures are Mercury's surface resembles both extremely hot and cold. that of Earth's Moon, scarred Because the planet is so close to the by many impact craters Sun, day temperatures can reach resulting from collisions with highs of 800°F (430°C). Without an meteoroids and comets. atmosphere to retain that heat at night, temperatures can dip as low Most of Mercury's surface as -290°F (-180°C). would appear greyish-brown to Despite its proximity to the Sun, the human eye. The bright Mercury is not the hottest planet in streaks are called "crater our solar system – that title belongs to nearby Venus, thanks to its dense rays." atmosphere. But Mercury is the fastest planet, zipping around the Sun every 88 Earth days.  VENUS- “a place where robots go to die” Venus, the second planet from the sun, is the hottest and brightest planet in the solar system. The scorching terrestrial (rocky) type planet is named after the Roman goddess of love and beauty and is the only solar system planet named after a female. In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise. However, further observations of Venus in the space age show a very hellish environment. This makes Venus a very difficult planet to observe from up close because spacecraft do not survive long on its surface. Venus and Earth are often called twins because they are similar in size, mass, density, composition and gravity. Venus is only a little bit smaller than our home planet, with a mass of about 80% of Earth’s. Venus takes 243 Earth days to rotate on its axis, which is by far the slowest of any of the major planets. In fact, its day is longer than its year, and that may be due to the thick atmosphere of Venus serving as a big brake on the planet's rotation. The Venusian year — the time it takes to orbit the sun — is about 225 Earth days long. Normally, that would mean that days on Venus would be longer than years. However, because of Venus' curious retrograde rotation(clockwise), the time from one sunrise to the next is only about 117 Earth days long. The last time we saw Venus transit in front of the sun was in 2012, and the next time will be in 2117. EARTH Earth, our home planet, is a world unlike any other. The third planet from the sun, Earth is the only place in the known universe confirmed to host life. Every other solar system planet was named for a Greek or Roman deity, but for at least a thousand years, some cultures have described our world using the Germanic word “earth,” which means simply “the ground.” Earth orbits the sun once every 365.25 days. Since our calendar years have only 365 days, we add an extra leap day every four years to account for the difference. Earth rotates on its axis every 23.9 hours, defining day and night for surface dwellers. This axis of rotation is tilted 23.4 degrees away from the plane of Earth's orbit around the sun, giving us seasons. MARS- the red planet Mars is the fourth planet from the sun and has a distinct rusty red appearance and two unusual moons. The Red Planet is a cold, desert world within our solar system. It has a very thin atmosphere, but the dusty, lifeless (as far as we know it) planet is far from dull. Phenomenal dust storms can grow so large they engulf the entire planet, temperatures can get so cold that carbon dioxide in the atmosphere condenses directly into snow or frost— a Mars version of an earthquake — regularly shake things up. Therefore, it is no surprise that this little red rock continues to intrigue scientists and is one of the most explored bodies in the solar system, according to NASA Science. Befitting the Red Planet's bloody color, the Romans named it after their god of war. In truth, the Romans copied the ancient Greeks, who also named the planet after their god of war, Ares. The bright rust color Mars is known for is due to iron-rich minerals in its regolith — the loose dust and rock covering its surface. The Red Planet is home to both the highest mountain and the deepest, longest valley in the solar system. Olympus Mons is roughly 17 miles (27 kilometers) high, about three times as tall as Mount Everest while the Valles Marineris system of valleys — named after the Mariner 9 probe that discovered it in 1971 — reaches as deep as 6 miles (10 km) and runs east-west for roughly 2,500 miles (4,000 km), about one-fifth of the distance around Mars and close to the width of Australia. Mars lies farther from the sun than Earth does, so the Red Planet has a longer year — 687 days compared to 365 for our home world. The two planets have similar day lengths, however; it takes about 24 hours and 40 minutes for Mars to complete one rotation around its axis, versus 24 hours for Earth. The axis of Mars, like Earth's, is tilted in relation to the sun. This means that like Earth, the amount of sunlight falling on certain parts of the Red Planet can vary widely during the year, giving Mars seasons. The first person to observe Mars with a telescope was Galileo Galilei, in 1610. In the century following, astronomers discovered the planet's polar ice caps. JUPITER Jupiter is the largest planet in the solar system and the fifth planet from the sun. The gas giant has a long, rich, history of surprising scientists. Named after the kind of the gods in Roman mythology this "king of the planets" is a stormy enigma shrouded in colorful clouds. Its most prominent and most famous storm, the Great Red Spot, is twice the width of Earth. Jupiter is a gas giant planet, as such it does not have a true solid surface. A spacecraft would not be able to land on the giant planet nor could it fly right through unscathed due to the crushing pressures and extreme temperatures it would experience during its journey. Jupiter has the shortest day in the solar system. One day on Jupiter takes only about 10 hours (the time it takes for Jupiter to rotate or spin around once), and Jupiter makes a complete orbit around the Sun (a year in Jovian time) in about 12 Earth years (4,333 Earth days). Jupiter has between 80 and 95 moons. The four largest moons – Io, Europa, Ganymede, and Callisto – were first observed by the astronomer Galileo Galilei in 1610 using an early version of the telescope. These four moons are known today as the Galilean satellites, and they're some of the most fascinating destinations in our solar system. Jupiter also has several rings, but unlike the famous rings of Saturn, Jupiter's rings are very faint and made of dust, not ice.  SATURN- the “ringed planet” Saturn is the sixth planet from the sun and the second- largest planet in the solar system. It has a whopping 146 moons. Like fellow gas giant Jupiter, Saturn is a massive ball made mostly of hydrogen and helium. The planet is named for the Roman god of agriculture and wealth, who was also the father of Jupiter. It's the farthest planet from Earth that's visible to the unaided eye, but the planet's most outstanding features — its rings — are better viewed through a telescope. The Ringed Planet is the least dense of all the planets and is the only one less dense than water. If there were a bathtub big enough to hold it, Saturn would float. Galileo Galilei was the first to see Saturn's rings in 1610, although from his telescope the rings looked more like handles or arms. As scientists developed better instruments, they continued to learn more about the structure and composition of the rings. Saturn actually has many rings made of billions of particles of ice and rock, ranging in size from a grain of sugar to the size of a house. The particles are believed to be debris left over from comets, asteroids or shattered moons. Saturn has the second-shortest day in the solar system. One day on Saturn takes only 10.7 hours (the time it takes for Saturn to rotate or spin around once), and Saturn makes a complete orbit around the Sun (a year in Saturnian time) in about 29.4 Earth years (10,756 Earth days). Its axis is tilted by 26.73 degrees with respect to its orbit around the Sun, which is similar to Earth's 23.5-degree tilt. This means that, like Earth, Saturn experiences seasons. URANUS- the “weirdest” & coldest planet in the solar system Uranus is one of two ice giants in the outer solar system (the other is Neptune). Most (80% or more) of the planet's mass is made up of a hot dense fluid of "icy" materials – water, methane, and ammonia – above a small rocky core. Uranus gets its blue-green color from methane gas in the atmosphere. Sunlight passes through the atmosphere and is reflected back out by Uranus' cloud tops. Methane gas absorbs the red portion of the light, resulting in a blue-green color. The seventh planet from the Sun with the third largest diameter in our solar system is surrounded by 13 faint rings and 27 small moons as it rotates at a 98-degree angle from the plane of its orbit. This unique tilt makes Uranus appear to spin sideways, orbiting the Sun like a rolling ball. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel, although he originally thought it was either a comet or a star. Uranus has the coldest atmosphere of any of the planets in Uranus has two sets of rings. The the solar system, even though it is not the most distant from inner system of nine rings the sun. That's because Uranus has little to no internal heat to consists mostly of narrow, supplement the heat from the sun. dark grey rings. There are two One day on Uranus takes about 17 hours (the time it takes outer rings: the innermost one is for Uranus to rotate or spin once). And Uranus makes a reddish like dusty rings elsewhere complete orbit around the Sun (a year in Uranian time) in the solar system, and the outer in about 84 Earth years (30,687 Earth days). ring is blue like Saturn's E ring. In order of increasing distance from Uranus is also one of just two planets that rotate in the opposite direction than most of the planets (Venus is the the planet, the rings are called other one), from east to west. Zeta, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda, The planet was named for Uranus, the Greek god of the sky, Epsilon, Nu, and Mu. Some of as suggested by Johann Bode. the larger rings are surrounded by belts of fine dust. NEPTUNE- the windiest planet in the solar system Dark, cold and whipped by supersonic winds, giant Neptune is the eighth and most distant major planet orbiting our Sun. More than 30 times as far from the Sun as Earth, Neptune is not visible to the naked eye. In 2011, Neptune completed its first 165-year orbit since its discovery. The planet’s rich blue color comes from methane in its atmosphere, which absorbs red wavelengths of light but allows blue ones to be reflected back into space. Neptune was the first planet located through mathematical calculations. Using predictions sent him by French astronomer Urbain Le Verrier, based on disturbances in the orbit of Uranus, German astronomer Johann Galle was first to observe the planet in 1846. The planet is named after the Roman god of the sea, as suggested by Le Verrier. Neptune is surrounded by unusual rings, which aren't uniform but possess bright thick clumps of dust called arcs. There are at least 5 rings around Neptune — called Galle, Leverrier, Lassell, Arago, and Adams — and they are considered relatively young and short-lived. One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). And Neptune makes a complete orbit around the Sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days). Neptune’s axis of rotation is tilted 28 degrees with respect to the plane of its orbit around the Sun, which is similar to the axial tilts of Mars and Earth. This means that Neptune experiences seasons just like we do on Earth; however, since its year is so long, each of the four seasons lasts for over 40 years. ASTEROID BELT Within the main asteroid belt, scattered in orbits around the sun are bits and pieces of rock left over from the dawn of the solar system. Most of these objects, called planetoids or asteroids — meaning "star-like" — orbit between Mars and Jupiter in a grouping known as the main asteroid belt. KUIPER BELT The Kuiper Belt is a doughnut-shaped region of icy objects beyond the orbit of Neptune. It is home to Pluto and most of the known dwarf planets and some comets. OORT CLOUD- home of comets The Oort cloud is a shell of icy bodies that surrounds the solar system. It begins beyond the Kuiper Belt and even beyond the influence of the sun’s magnetic field, technically in interstellar space. Because the orbits of long-period comets are so extremely long, scientists suspect that the Oort Cloud is the source of most of those comets. Though long-period comets observed among the planets are thought to originate in the Oort Cloud, no object has been observed in the distant Oort Cloud itself, leaving it a theoretical concept for the time being. But it remains the most widely-accepted explanation for the origin of long-period comets. BLACK HOLE Black holes are some of the strangest and most fascinating objects in space. They're extremely dense, with such strong gravitational attraction that not even light can escape their grasp. Black holes form when a star collapses in on itself and dies. As the star runs out of fuel, its mass eventually flows into the core where the gravitational force becomes so heavy the core collapses and a supernova occurs. What's left is the black hole, which has since been compressed down into an extremely dense point called a singularity. DARK MATTER/ ENERGY Dark matter is the mysterious stuff that fills the universe but no one has ever seen. One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy- of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the universe. REFERENCES: https://science.nasa.gov/solar-system/facts/ https://kids.nationalgeographic.com/space/article/milky-way https://www.livescience.com/our-solar-system.html https://universe.nasa.gov/galaxies/types/ https://www.space.com/15590-andromeda-galaxy-m31.html https://science.nasa.gov/solar-system/planets/what-is-a-planet/