Unit 1 The Universe Mrs. Williams 8th Grade Big Idea: The sun is one of billions of stars in one of billions of galaxies in the universe. Unit 1 The Universe Mrs. Williams 8th Grade

Big Idea:

Universe-space & all the matter & energy in it. Unit 1 Lesson 1 Structure of the Universe Our Place in Space Universe-space & all the matter & energy in it. Galaxy- a large collection of stars, gas, & dust There are an estimated 100 billion galaxies in the universe. Matter (stuff) which is made of elements and compounds, then there is energy (gravity, magnetism, electricity, etc) which connects and steers matter, and of course there is a lot of void (vacuum or nothingness) Have students draw 4 concentric circles in their notes. Explain that each of the circles can be used to represent a level of organization of space. Direct students to label each circle with the level it represents, from largest and most complex to simplest. (Answer: UNIVERSE, MILKY WAY, SOLAR SYSTEM, EARTH) Earth is one of eight planets that orbit the sun, which is a star. A star is a large celestial body that is composed of gas and emits light. Stars are grouped together in structures known as galaxies. A galaxy is a large collection of stars, gas, and dust. Throughout the universe, there are areas where galaxies are densely concentrated. These areas are called clusters and superclusters. Clusters contain as many as several thousand galaxies. Superclusters can be made up of 10 or more clusters of galaxies. The universe also contains huge spherical areas where very little matter exists. These areas are called voids. Astronomers have begun to think of the universe as having a structure similar to soap bubbles. Clusters and superclusters are located along the thin bubble walls. The interior of the bubbles are voids. It takes light hundreds of millions of years to cross the largest voids. Small galaxies, called dwarf galaxies, may contain a few billion stars. Giant galaxies may contain hundreds of billions of stars. Our solar system is located in the Milky Way galaxy. The Milky Way is classified as a spiral galaxy. Milky way galaxy Earth Universe Solar system

Unit 1 Lesson 1 Structure of the Universe Types of Galaxies Spiral galaxies are shaped like pinwheels. They have a central bulge from which two or more spiral arms extend. Elliptical galaxies look like spheres or ovals and do not have spiral arms. Irregular galaxies appear as splotchy, irregularly shaped “blobs.” They are very active areas of star formation. Draw a picture of all three. http://library.thinkquest.org/C0110277/images/galaxies.gif

What Makes Up the Universe? Unit 1 Lesson 1 Structure of the Universe What Makes Up the Universe? Solar system- the collection of large & small bodies that orbit our central star, the sun. Planet-spherical body that orbits the sun. The solar system has eight bodies called planets, which are generally larger than the other bodies. The contents of the solar system are numerous and stretch across a large area of space. For example, the solar system is so big that the distance from the sun to Neptune is 4.5 billion km. It would take a 9 month journey to get to Mars. My Very Educated Mother Just Served Us Nine Pizzas- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto (dwarf planet)

Unit 1 Lesson 1 Structure of the Universe Terrestrial Planets Terrestrial Planets- rocky, dense, and relatively small. Mercury, Venus, Earth and Mars The four planets that orbit nearest to the sun are called terrestrial planets. A terrestrial planet is mostly solid. Generally, they all have a core made of up of iron or other heavy metals. The terrestrial planets then have a mantle, which is usually composed of silicate rock. Because they are composed of heavy metals and rocks, terrestrial planets are denser than gas giants – which are mostly hydrogen and other gaseous materials – are. Terrestrial planets also have a very diverse landscape with craters, mountains, and valleys. Terrestrial planets have few or no moons. Venus and Mercury have no moons. Mars has two small moons called Phobos and Deimos after mythological Greek deities. Earth has one satellite, the Moon. Unlike the gas giants, the terrestrial planets have no planetary rings. They are also a fraction of the size of the gas giants. For example, Earth is the largest terrestrial planet, but over 1300 Earths could fit inside Jupiter the largest planet in the Solar System. Scientists have created several categories of terrestrial planets. Read more: http://www.universetoday.com/50289/terrestrial-planet/#ixzz2AB9W4YQu http://ut-images.s3.amazonaws.com/wp-content/uploads/2008/04/mercurycomparison.jpg

Unit 1 Lesson 1 Structure of the Universe Gas giant planets - have thick, gaseous atmospheres; small, rocky cores; and ring systems of ice, rock, and dust. Jupiter, Saturn, Uranus, and Neptune. The four planets that orbit farthest from the sun are called gas giant planets.

Small Bodies in the Universe Unit 1 Lesson 1 Structure of the Universe Small Bodies in the Universe Moons- orbit most of the planets. Earth has only one moon, but Jupiter has more than 60. The solar system has other small bodies, including Dwarf planets Comets Asteroids Meteoroids http://home.earthlink.net/~meshellwg/w/www/images/comet.jpg Altogether, there are up to a trillion small bodies in the solar system. Comets are made of ice, rock and dust. When they travel by the sun it makes the ice melt giving it a tail. There are about 3200 comets Asteroids are made of metal and rock material. They tend to clump together. Some found between Mars and Jupiter Meteoroids enter the Earth’s atmosphere. Shooting stars are meteoroids.

Measuring the Universe Unit 1 Lesson 1 Structure of the Universe Measuring the Universe Distances between most objects in the universe are so large that astronomers measure distances using the speed of light. Light-year -the distance that light travels through space in one year. Light travels through space at about 300,000 km/s, or about 9.5 trillion kilometers in one year. Light year- 9.46 trillion km. Ask students to describe in measurements how far their house is from school. Did they use inches, centimeters, miles, light years. Explain how scientists use measurements to describe such large distances (scientific notation again, too) The closest star to the sun and Earth is Proxima Centauri. It takes light about 4.3 years to travel from Proxima Centauri to us. Therefore, the distance from Proxima Centauri is around 4.3 light-years. Light travels to Earth in about 8 minutes. Thus, the distance from the sun to Earth is around 8 light-minutes (b/c light-years is too big). We know light travels at 299,792 km/sec (186,322 miles/sec). At that speed, the light-year becomes a convenient unit of distance in the Milky Way. THIS CAN EXPLAIN WHY WE KNOW THAT PROXIMA CENTAURI IS 4.3 ly AWAY. Look to that star in the sky tonight and you're seeing it as it was 4 years ago. The center of our Galaxy is 26,000 light-years away. The light we see from there left when our ancestors were painting primitive scenes in caves. The farthest object we can see with our eyes, in a dark sky without the aid of a telescope, is the Andromeda Galaxy, more than 2 million light-years away. What was happening on Earth 2 million years ago?

Unit 1 Lesson 1 Structure of the Universe Reach For The Stars! Star - large celestial body that is composed of gas & emits light. Most stars are composed almost entirely of hydrogen and helium. Stars emit light and vary in brightness, size and temperatures. Energy is produced in the core of the star by the process of nuclear fusion. Energy escapes in the form of light, other forms of radiation, heat, and wind. Stars range in size from about the size of Earth to as much as 1,000 times the size of the sun. The temperatures of stars vary, resulting in differences in color. Stars range in color from red, which indicates a cool star, to blue, which indicates a very hot star. The sun is a relatively cool yellow star. Stars have different sizes, ranging from 1/100 the size of the sun to 1,000 times the size of the sun. Two or more stars may be bound together by gravity, which causes them to orbit each other. Three or more stars that are bound by gravity are called multiple stars or multiple star systems. WE WILL DISCUSS THE STRUCTURE OF THE SUN IN A DIFFERENT UNIT. The sun is a star and is composed mostly of hydrogen and helium. It also contains oxygen, carbon, neon, and iron. At the center of the sun lies the core, where gases are compressed and heated and temperatures reach 15 million degrees Celsius. The sun’s core is where matter is converted into energy. The sun’s atmosphere has several layers and extends millions of kilometers into space. The photosphere is the layer of the sun’s atmosphere we see from Earth. It has an average temperature of 5,527 °C. Energy is transferred from the sun’s core to the photosphere and escapes into space as visible light, other forms of radiation, heat, and wind. The sun’s middle atmosphere is called the chromosphere. Its temperatures range from 4,225 °C to 6,000 °C. In the sun’s outer atmosphere, or corona, temperatures may reach 2 million degrees Celsius http://www.le.ac.uk/ph/faulkes/web/images/stars.jpg

You’re a Shining Star How is star brightness measured? Unit 1 Lesson 2 Stars You’re a Shining Star How is star brightness measured? Apparent magnitude -measure of a star’s brightness as seen from Earth. Luminosity- actual brightness of a star. Absolute magnitude -measure of how bright a star would be if the star were located at a standard distance. Ancient astronomers, using only their eyes, described star brightness by magnitude. They called the brightest stars they could see first magnitude and the faintest stars they could see sixth magnitude. Using telescopes, astronomers see many stars that are too dim to see with the unaided eye. They added to the magnitude system. Rather than changing what the ancient astronomers did that just added to it. Today, the brightest stars have a magnitude of about –2, and the faintest stars that we can see with a telescope have a magnitude of +30. Dim stars have positive (larger) numbers, and bright stars have negative (smaller) numbers. Absolute magnitude is a measure of the brightness of a star whose distance from Earth is known. Stars with the same absolute magnitude may have different apparent magnitudes. Pg. 20 SE explains the picture with the flashlights. Do this with 2 flashlights that are exactly the same, using exact same battery.

Unit 1 Lesson 2 Stars Too HOT to Handle Surface temperatures of Stars are measured by their COLOR COLOR SURFACE TEMPERATURE (˚C) Blue Above 25,000 Blue-white 10,000-25,000 White 7,500-10,000 Yellow-white 6,000-7,500 Yellow 5,000-6,000 Orange 3,500-5,000 Red Below 3,500 Stars have different colors. The differences in the colors of stars are due to differences in their surface temperatures. The same is true of all objects that glow. If an object’s color depends only on temperature, the object is called a blackbody. As the temperature of a blackbody rises, it glows brighter and brighter red. As it gets hotter, its color changes to orange, yellow, white, and blue-white. Stars that have the lowest surface temperatures (below 3,500 °C) are red. Stars that have the highest surface temperatures (above 25,000 °C) are blue.

Stars differ greatly in size Unit 1 Lesson 2 Stars Stars differ greatly in size White dwarfs - Very small stars have about the same radius as Earth, which is approximately 0.01 solar radius. Giant stars - Very large stars, typically have sizes between 10 and 100 times the sun’s radius. Supergiants - Some rare, extremely large stars have sizes of up to 1,000 solar radii. . Some are about the same size as Earth, and others are larger than the size of Earth’s orbit around the sun. Astronomers use the size of the sun to describe the size of other stars. Pg. 23 SE; Compare the sizes and temperatures of the red, blue, and yellow stars.

A Star Is Born Stars form in nebulae. Unit 1 Lesson 3 The Life Cycle of Stars A Star Is Born What is the life cycle of a star? Stars form in nebulae. Nebula -large cloud of gas and dust. It is composed mainly of hydrogen and helium, with small amounts of heavier elements. An outside force, such as the explosion of a nearby star, (or gravity) may cause the nebula to contract and cool. As particles within the nebula are pulled closer together, gravitational attraction increases. As a result, dense regions of gas and dust form within the nebula. The densest regions, called dense cores, form new stars. The temperature within dense cores increases for millions of years. At about 10 million °C, the process of hydrogen nuclear fusion begins, marking the birth of a star. A star can remain actively fusing hydrogen into helium for billions of years. This stage ends when the star runs out of hydrogen. http://dsc.discovery.com/convergence/hubble/hits/gallery/garden4_lrg.jpg

Unit 1 Lesson 3 The Life Cycle of Stars Birth of a Star Nuclear fusion –high temp & pressure cause two or more low-mass atomic nuclei to form a heavier nucleus. Gives off light. Occurs for most of the stars life. The active fusion stage is the longest stage in the life cycle of a star. This stage can last for billions of years. The active fusion stage ends when a star runs out of Hydrogen. When nearly all the hydrogen in a star’s core has fused into helium, the core contracts under its own gravity and its temperature rises. Energy is transferred to a thin shell of hydrogen surrounding the core, where hydrogen fusion continues and the shell expands. When fusion ends completely, the star begins to eject matter, until only the core remains.

Unit 1 Lesson 3 The Life Cycle of Stars The Lightweights Low-mass stars- The sun is a low mass, medium size star. Giants-large red stars due to star’s outer atmosphere expanding after active fusion ends. White dwarf -hot, dense core of matter that remains from the collapse of a low-mass star. It is about the size of Earth. The outward pressure generated by a star’s fusion reaction is in balance with the inward gravitational pull. When the active fusion stage ends, these forces are no longer in balance, and the star’s outer atmosphere expands. The gases in the outer shell grow cooler, and the star is much larger and glows red. These large red stars are called giants. Giant stars shine brightly because of their large surface areas. Giants are at least 10 times the size of the sun. Low-mass stars, which contain about as much mass as the sun, will become red giants. Over time, a giant’s outer gases drift away, and the remaining core collapses, becoming denser and very hot. White dwarfs shine for billions of years, becoming fainter as they cool. This is the final stage in the life cycle of low-mass stars.

The Heavyweights High mass stars Unit 1 Lesson 3 The Life Cycle of Stars The Heavyweights High mass stars Supergiant-produces heavier elements like carbon Supernova -gigantic explosion in which a high-mass star collapses, throwing its outer layers into space. But its core remains. Neutron star -small, incredibly dense ball of closely packed neutrons. Black hole -invisible object with gravity so great that nothing, not even light, can escape it. When hydrogen fusion in a high-mass star ends, other types of fusion begin, producing elements heavier than carbon. The star expands to become a supergiant. A star with 10 times the mass of our sun will become a supergiant in just 20 million years. In the supergiant stage, the high-mass star fuses larger and larger nuclei until all its nuclear fuel is used up. The core then rapidly collapses and heats up. This halts the collapse, and the supergiant becomes a supernova. As the core of a supernova continues to collapse, its protons and electrons smash together to form neutrons. Neutron stars rotate very rapidly. Some emit a rotating beam of electromagnetic radiation. These stars are called pulsars. Some supergiants are so massive that their cores are unable to stop collapsing under the force of gravity. As the core collapses, the mass of the star is compressed into a single point, which is called a black hole. Although black holes are invisible, they can be observed by the gravitational effect they have on their surroundings. Matter swirls around a black hole just before being pulled in. The matter becomes so hot that it emits X-rays. Astronomers use X-rays and other means to locate black holes, even within our own galaxy.

Unit 1 Lesson 3 The Life Cycle of Stars A Graphic Display H-R diagram –graph that shows the relationship between the stars surface temperature & absolute magnitude (brightness/luminosity) Main sequence -region of the diagram where stars spend most of their lives. (actively fusing hydrogen) Astronomers refer to brightness as luminosity. Luminosity is a measure of the total amount of energy a star gives off each second. When the surface temperatures of stars are plotted against their luminosity, a consistent pattern is revealed. The hottest stars are located on the left side of the H-R diagram and are blue. The coolest stars are located on the right side of the diagram and are red. The brightest stars are located at the top of the diagram, and the dimmest stars are located at the bottom. The temperature and luminosity of most stars fall within a band that runs diagonally through the middle of the H-R diagram. Stars within this band are actively fusing hydrogen and are called main-sequence stars. The sun is a main-sequence star. When nuclear fusion ends in the sun, it will become a giant and will move to the upper right quadrant of the H-R diagram. When the outer layers of the giant are lost to space, the sun will become a white dwarf and move to the lower left quadrant of the diagram.