Studying and exploring space
Earth Science - Middle School
Our Solar System
Multimedia Lesson
Formation of Our Solar System
Presentation
The Sun
Presentation
Measuring Distances in Space
Presentation
The Inner Planets
Presentation
The Outer Planets
Presentation
Comets, Asteroids, and Meteors
Presentation
Pluto
Presentation
Planet Exploration
Virtual Lab
The Sun
Interactive
The Solar System
Interactive
Gravity and Orbits
Interactive
Studying and exploring space
Study Guide
Studying and exploring space
Quiz
Studying and exploring space
Flash Cards
Studying and exploring space
Worksheet
Studying and exploring space
Game
Studying and exploring space
Vocabulary List
Study Guide Studying and exploring space
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STUDYING AND EXPLORING SPACE Our ability to understand our solar system and the universe beyond has grown by dramatic leaps in the last few decades. The truth is, though, that all that lies beyond our own home planet has fascinated people for countless centuries. Using very basic as well as very complex tools, humans have been able to discover and understand amazing realities about our solar system, the universe, planets and stars, how they all formed and how they are all changing. The Early Space “Explorers” Using simple tools and the power of observation, early theories about our solar system and the planets within it proved to ultimately be remarkably accurate. Of course, much was inaccurate, too. The ancient Greek astronomer named Ptolemy carefully studied all the ancient knowledge he could gather about the planets and astronomy in general and from that information created what is now known as The Ptolemaic theory. Based on his studies he concluded that the Earth is the center of the universe and that the sun and the planets all revolve around it. Ptolemy’s picture of the universe It wouldn’t be until the mid 16th century that a new (and revolutionary) theory about our solar system would be proposed. In 1543, a Polish astronomer named Nicolaus Copernicus (1473-1543) concluded that the Earth rotates on its own axis, that the sun is the center of the universe and that all the planets revolve around it. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Some call this the Copernican Theory. In technical terms, it is called the principle of heliocentric planetary motion. Galileo Galilei (1564-1642) was the first person to use a telescope to study the moon and planets. He also discovered moons orbiting Jupiter. His observations supported Copernicus’s theory that the sun is the center of the universe. Galileo’s support of the Copernican theory was considered to be heresy by the Roman Catholic Church which ultimately forced Galileo to recant his position. Understanding of planets and our solar system continued to advance in the late 17th century. Isaac Newton (1642- 1727), the famous English mathematician, scientist and philosopher, explained that gravity is the force that causes planets to orbit the sun and moons to orbit their planets. This picture, drawn by Isaac Newton, shows his theory that if a ball were thrown hard enough it would leave Earth’s gravitational pull until it was in orbit around the Earth. Traveling into Space Our understanding of space, the planets, the stars and the universe as a whole made quantum leaps forward in the twentieth century. Edwin Powell Hubble (1889-1953) was an American astronomer who, in 1923, showed that the universe is expanding. He used photographs to prove that there are galaxies beyond our own. Prior to this, scientists believed that our galaxy was the entire universe. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Studying space from Earth has provided dramatic and rich information. But the Earth’s atmosphere distorts incoming light and images of objects in space. To get the clearest view of the universe, one must get beyond Earth’s atmosphere and use space-based telescopes. It may be very surprising to discover that some of the most basic information about our universe has been discovered very recently using space-based telescopes. In 1990, the Hubble Space Telescope (clearly named in honor of the great 20th century astronomer) was launched by NASA and has provided some of the most spectacular images of the universe ever seen. Dramatic advances in physics and optics have allowed space-based telescopes like Hubble to see a wide range of electromagnetic radiation, far more than just visible light. This information has revealed more about the universe than we would ever have been able to know from even the best land-based telescopes. Rockets and Rocketry Development Space-based telescopes would not have been possible without the development of rockets and space travel. One could say that rockets and space travel began in the mind of visionaries. The visions and stories of the French science fiction writer, Jules Verne, inspired a Russian teacher named Konstantin Tsiolkovsky to study the motion of rockets. Though Tsiolkovsky never actually built and experimented with rockets, this Russian became known as the Father of rocket theory. His work prepared the way, however, for the work of Robert Goddard who built and experimented with the very first rockets. Consequently, Goddard is commonly referred to as the Father of modern rocketry. From the standpoint of physics, rockets operate based on Newton’s third law of motion that states that for every action there is an equal and opposite reaction. Rocket fuel is burned inside the rocket in a combustion chamber. The force that is exerted out of the rocket’s exhaust nozzle equals the force of the gas pushing at the top of the combustion chamber. When the force pushing at the top of the combustion chamber is greater than the force of gravity holding the rocket on Earth, the rocket moves upward. This force that moves the rocket is called thrust. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
For rockets to move people and machinery into space and completely out of Earth’s gravitational pull, they must reach escape velocity. The escape velocity from Earth’s gravitational pull is 11 km/second. A rocket must travel at 8 km/s to achieve orbital velocity. Orbital velocity is the speed and direction needed to orbit the Earth. Lesson Checkpoint: What is ‘escape velocity’? Early Space Missions The first application of rocketry was military: they were used to deliver bombs. Late in the 1950’s, though, the former Soviet Union launched a rocket that put the first satellite, Sputnik, into orbit around the Earth. This marked the beginning of a space race between the United States and the Soviet Union. In 1961, the Soviet Union also became the first country to put a man into space, cosmonaut Yuri Gagarin. The United States responded to this accomplishment with an aggressive space exploration program of its own. (John Glenn was the first American to orbit the Earth. Neil Armstrong was the first human to step on the moon. Sally Ride was the first woman in space.) By the end of the 1960’s the United States had developed a complete program that not only developed rockets that could put heavy payloads into space, but had also developed a manned space program that put astronauts on the moon and returned them safely to Earth. The organization created by the United States to improve rocket technology and to explore the moon and space is called the National Aeronautics and Space Administration (NASA). There were a number of missions throughout the 1960’s that prepared for the moon landings. The Apollo missions were the space flights that eventually landed the United States on the moon. The first purpose of the moon landings was purely political in that we intended to strengthen American national pride in light of the accomplishments of the Soviet space program. However, the technologies developed for NASA and space travel proved to be invaluable for science, technology and use in everyday life. In addition, important scientific information about the moon was collected during the lunar missions, including © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
studies of solar wind activity, moonquake activity, and collections of rock and dust samples from the moon’s surface. By the mid-1970’s, the focus of space work for the United States and NASA shifted from moon landings to regular travel into space in a reusable craft. These missions would be used for a number of purposes including scientific studies of the effects of weightlessness on astronauts and for a variety of experiments from growing plants to growing crystals and more. The Space Shuttle has also placed telescopes and other equipment in space, such as large pieces of the International Space Station. The advancement of the Space Shuttle program was that the air craft is reusable. Remember that the Saturn V rocket that transported astronauts to the moon, for example, was a single-use vehicle. All the components of the Saturn V rockets, including the vehicles that landed on the moon and returned the astronauts to Earth, were used only once. The Space Shuttle was the first generation space vehicle designed to be used over and over again. Space Shuttle In addition to the Space Shuttle program, NASA has developed and launched a number of space probes that have gathered spectacular images and invaluable information about planets in the far reaches of our solar system. A space probe is a vehicle equipped with scientific instruments that travels to other planets and moons to study their features, compositions and movements. Magellan Space Probe © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The Viking 1 and Viking 2 probes were sent to study Mars in 1975. In 1997 the Mars Pathfinder mission sent two movable robotic rovers to study the surface of Mars. Mars is of particular interest because it is physically similar to Earth and it may have had significant quantities of water at one time that could have allowed the development of some form of life. The Pioneer, Voyager and Galileo missions were unique because the purpose of these space probes was to study the outer portions of the solar system. Specifically, these probes studied solar wind, Jupiter, Saturn, Uranus and Neptune. Stardust was the first space probe designed to study a comet. New concepts for space exploration are developing all the time. NASA has a New Millennium program that focuses on the development of new technologies in space probes. For example, Deep Space 1 is a new breed of space probes. Its purpose is to study the universe using new and potentially risky technologies. Deep Space 1 is unique because it is powered by an ion rocket that expels charged particles. This ion propulsion system functions on the same principle as traditional fuel probes, that is, Newton’s third law of motion. NASA is also a partner with other nations in the building, maintenance and staffing of the International Space Station. The ISS is a valuable endeavor for a number of reasons. First, it is an important source of very positive international relations, including relations between nations that have in other areas have been at odds with one another. (For example, two of the principal partners in the ISS are the United States of America and Russia.) Second, it is a platform for specialized scientific research in a weightless environment. Similarly, it allows the study of the effects of weightlessness on humans. Zero gravity has dramatic effects on bone density and muscle tone. Scientists are continually learning how to counteract these effects while living in space. The ISS promises to be an important base of specialized research designed to improve space travel and living in space as well as bringing benefits to life on Earth. Lesson Checkpoint: Name one advantage of the International Space Station. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Solar Radiation There are big dreams for activity in space. Some believe the moon will be a place where specialized materials and products can be manufactured. Perhaps the moon and Mars can be mined for important mineral resources. Perhaps a colony of people could live on the moon. For these goals to be achieved, astronauts will have to overcome many obvious challenges for living in space such as oxygen supplies, weightlessness and all its physical consequences, and temperature control. Another challenge is the danger from solar radiation. Radiation from a number of sources is moving throughout the universe. The sun produces the full spectrum of electromagnetic radiation. In addition, cosmic background radiation travels in all directions throughout the universe. Cosmic background radiation is faint microwave radiation. It was discovered in the mid 1960’s by A. Penzias and R.W. Wilson. It is thought that this cosmic background radiation is electromagnetic energy that is left over from the “Big Bang” or massive explosion which scientists theorize was the beginning of the universe. This so-called Big Bang Theory states that the universe began as a cosmic explosion 10 to 15 billion years ago. It is theorized that it was not really an explosion of matter, but an explosion of space itself. Some electromagnetic frequencies are dangerous to humans. (Ultraviolet radiation, for example, is known to cause skin cancer.) However, solar radiation is more than light waves of various frequencies. It also includes ionizing radiation, solar protons, and high-energy electrons and protons. Astronauts must be protected from these various radiation dangers. Space suits are designed to provide this protection. For example, the gold protective layer on the visor of the astronauts’ headgear protects them from ultraviolet radiation. Despite the exciting progress in space exploration, space is ultimately a hostile environment. Sending humans into space, particularly for extended periods of time, will always present significant technological challenges. While these challenges are being studied, unmanned space probes will continue to peek into the far reaches of the solar system and the universe. This is a very exciting time of human history to be an astronomer! © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Table Of Contents: Our Solar System
1. Formation of Our Solar System
2.1. Nebulae
Solar systems begin in dusty gas clouds called nebulae that are found between stars. The dust is composed of elements like iron and carbon. Nebula gases include hydrogen and helium.
2.2. Planetesimals
Within a nebula, dust particles collide and stick together to form larger particles. This process is called accretion. The particles grow from pebbles, to rocks, to boulders. The larger particles are called planetesimals.
2.3. Rocky and Gaseous Planet Formation
Rocky planetesimals near the Sun grew by accretion to become the rocky planets—Mercury, Venus, Earth and Mars. In the colder outer parts of the solar system, frozen gases accreted to rocky cores to form the gas giant planets—Jupiter, Saturn, Uranus and Neptune.
2. Geocentric and Heliocentric Systems
3.1. Geocentric Universe Concept
Before the invention of the telescope, the solar system was described in relation to the Earth. In 140 AD, the Greek astronomer Ptolemy believed that the Earth was the center of the universe, and the Sun and planets revolved around the Earth. This is the geocentric concept of the universe.
3.2. Heliocentric Universe Concept
In 1543 Copernicus published a theory about the universe. He claimed that the Sun is the center of the universe and all the known planets revolved around the Sun. This is the heliocentric concept of the universe.
3.3. A Heliocentric Solar System
Copernicus believed that the Sun was the center of the universe. Today we know that the Sun is the center of our solar system—a collection of planets orbiting a single star, the Sun. Our solar system is within the Milky Way galaxy, which is within a universe of galaxies.
3.4. Parts of Our Solar System
Our solar system includes the Sun, eight planets, the moons of each planet and other objects that revolve around the Sun. The four rocky planets closest to the Sun are known as the inner planets, and the four gaseous planets in the outer solar system are called the outer planets. The relative size of the inner planets is much smaller than the outer planets.
3. The Sun
4.1. What Is the Sun Made of?
The Sun is a massive burning ball of gases held together by gravity. It is primarily composed of helium and hydrogen gases.
4.2. Structure of the Sun
The Sun has three main layers—the core, the radiative zone and the convective zone. The Sun’s atmosphere is made up of the photosphere, chromosphere and corona.
4.3. The Sun’s Core and Nuclear Fusion
The core at the center of the Sun produces the Sun’s heat. This energy is produced by hydrogen nuclear fusion reactions. During nuclear fusion, two or more protons fuse to form helium, and large amounts of energy are released.
4.4. The Sun’s Radiative Zone
Energy produced in the Sun’s core is carried to the Sun’s surface in the form of light energy called photons. This energy moves from the core into a very dense radiative zone. It can take thousands of years for the light energy to move through this layer and into the convective zone.
4.5. The Sun’s Convective Zone
The outer layer of the Sun is called the convective zone. Hot gases in this layer rise toward the surface, where they become cooler and denser. The gases then descend back into the Sun. This circulating movement is called convection, and is similar to currents in the Earth’s mantle.
4.6. The Sun’s Photosphere
The photosphere is the inner layer of the Sun’s atmosphere. This gaseous layer is thick enough to be visible. When we look at the Sun, we are seeing the photosphere.
4.7. The Sun’s Chromosphere
Just beyond the photosphere is a thin layer called the chromosphere, which has a reddish color. The chromosphere can be seen during a total solar eclipse when the Moon covers the Sun.
4.8. The Sun’s Corona
The outer atmosphere of the Sun is called the corona. It extends for millions of kilometers beyond the Sun, and is composed of gases. It can only be seen during a total solar eclipse.
4.9. Sunspots
Sunspots are cooler, darker areas of gas on the Sun’s surface. Cooler gases emit less light than hotter gases. These areas are caused by the Sun’s magnetic field affecting the convection heat. Scientists have discovered that the number of sunspots varies over an 11-year cycle.
4.10. Solar Flares
Solar flares are enormous areas of extreme temperature on the Sun’s surface, caused by magnetic fields. Solar flares typically occur near sunspots. When a solar flare erupts, streams of charged gas particles extend thousands of kilometers into space.
4. Pause and Interact
5.1. Review
Use the whiteboard tools to complete the activity.
5.2. The Sun
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.
5. Measuring Distances in Space
6.1. Astronomical Units
The distance between the Earth and the Sun is approximately 150 million kilometers, or one astronomical unit (AU). Scientists use astronomical units to measure and describe distances in space. Another measurement is called a light-minute, which is the distance light travels in one minute, or approximately 18 million kilometers.
6.2. Distance Between the Planets and Sun
The dimensions of our solar system are vast. The four inner planets are much closer to the Sun than the four outer planets. There are numerous orbiting comets found beyond the planets in the outer solar system.
6. The Inner Planets
7.1. What Are the Inner Planets?
The four planets closest to the Sun, Mercury, Venus, Earth and Mars, are grouped together as the inner planets. They have rocky surfaces, and are often called the terrestrial planets. These planets are small and closely spaced, as compared to the outer planets.
7.2. Mercury
Mercury is the smallest planet, located closest to the Sun. Mercury revolves on its axis very slowly. A single Mercury day is about 59 Earth days long. Mercury does not have any moons or atmosphere. Its surface is covered with craters. A magnetic field suggests that it has an iron core.
7.3. Venus
Venus is the second closest planet to the Sun. It is often called Earth's sister or twin planet due to similar composition, gravity and size. Venus rotates very slowly in a clockwise direction, called retrograde rotation. Similar to the planet Mercury, Venus does not have any moons.
7.4. Atmosphere and Surface of Venus
Venus is surrounded by a very dense atmosphere composed of carbon dioxide and sulfuric acid clouds. Due to the greenhouse effect, Venus has the hottest surface temperature of any planet. The air pressure on Venus is 92 times that on Earth. Craters and active volcanoes cover the surface of the planet. From a geologic perspective, Venus is considered a young planet.
7.5. Earth
The Earth is the third planet from the Sun. The Earth's distance from the Sun allows for moderate temperatures that keep most surface water in liquid form. The presence of liquid water and an oxygen-rich atmosphere make Earth suitable for millions of living organisms.
7.6. Mars
Mars, the fourth planet from the Sun, has two moons. A day on Mars is slightly longer than a day on Earth, and it takes about 687 days for Mars to revolve once around the Sun. Space probes and rovers have successfully gathered much information about Mars.
7.7. Atmosphere and Surface of Mars
Mars has a very thin atmosphere composed primarily of carbon dioxide. The surface is cold, dry, and dusty, with frozen ice caps found at the poles. Landforms and rover samples indicate that in the past there were large amounts of liquid water on the surface. Mars has a volcanic history, and the largest volcano in the solar system, Olympus Mons, is found there.
7. Pause and Interact
8.1. Review
Use the whiteboard tools to complete the activity.
8. The Outer Planets
9.1. What Are the Outer Planets?
The outer planets beyond Mars are the gas giant planets, Jupiter, Saturn, Uranus and Neptune. They are also known as the Jovian planets. These planets are much larger and spaced further apart than the inner planets. They are primarily composed of hydrogen and helium.
9.2. Jupiter
Jupiter, the fifth planet from the Sun, is the largest planet in the solar system. Although primarily composed of gases, its magnetic field indicates that it may have a rocky core. It has a giant red spot that is actually an enormous storm in its atmosphere. There are 64 known moons that orbit Jupiter.
9.3. Saturn
Saturn, the sixth planet from the Sun, is the second largest planet in the solar system. Winds can blow as fast as 1,800 km on this planet. Saturn's rings are primarily composed of ice particles with some dust and rock particles mixed in. There are 62 known moons that orbit Saturn.
9.4. Uranus
Uranus, the seventh planet from the Sun, is the first planet to be discovered with the use of a telescope. Its cloudy atmosphere is primarily made of helium and hydrogen, but also has higher concentrations of frozen ammonia, water and methane. Uranus is sometimes referred to as an ice giant. This planet has two sets of rings and 27 known orbiting moons.
9.5. Rotation and Tilt of Uranus
Similar to Venus, Uranus spins on its axis in a clockwise direction, called retrograde rotation. It also has a rotation axis that is tilted almost parallel to its orbital plane. This makes it appear that Uranus is rotating on its side.
9.6. Neptune
Neptune is the furthest planet from the Sun. This gas giant is similar to Uranus in that it has a higher amount of frozen gases like methane, water and ammonia, and therefore it is also called an ice giant. The highest known wind speeds in the solar system, measuring up to 2,100 kilometers per hour, are found on Neptune. Thirteen moons orbit Neptune.
9. Pause and Interact
10.1. Review
Use the whiteboard tools to complete the activity.
10. Comets, Asteroids, and Meteors
11.1. Comets
A comet is a small body composed of rock and ice that orbits the Sun. A comet's tail of ice particles can stretch for millions of kilometers behind it. Comets originate in the outer regions of the solar system and have a wide range of orbital periods, up to a thousand years long. Scientists have identified thousands of comets, but this is just a fraction of the total number that exist.
11.2. Asteroids
Asteroids are irregularly shaped, rocky bodies that circle the Sun. They are found mostly in an area between Mars and Jupiter called the asteroid belt. Asteroids range in size from quite small to 100 kilometers in diameter. There are over 500,000 known asteroids.
11.3. Meteoroids
Meteoroids are smaller pieces of rock that have originated from asteroids. A streak of light called a meteor is seen when a meteoroid enters and burns in the Earth's atmosphere. When a meteoroid strikes Earth, it is called a meteorite. Meteor Crater in Arizona shows the impact and size of meteorite collision.
11. Pluto
12.1. Pluto and the Kuiper Belt
Up until 2006, Pluto was considered the ninth planet from the Sun. After intensive studies, a group of international astronomers concluded that Pluto was actually a dwarf planet in a region called the Kuiper Belt. Asteroids and other planetesimals are found in this far distant region of our solar system.
12. Pause and Interact
13.1. The Solar System
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.
13. Vocabulary Review
14.1. Vocabulary Matching Review
Use the whiteboard tools to complete the activity.
14. Virtual Investigation
15.1. Planet Exploration
In this virtual investigation you will explore our solar system by comparing several characteristics of the planets. Complete the four activities and record your data during this exploration.
15. Assessment
16.1. Our Solar System
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