Science 10 Astronomy Unit Review PDF

## SCIENCE 10 - ASTRONOMY UNIT REVIEW ### MEMORIZE 1. How can astronomers directly observe events that took place in the early universe several billion years ago? - Because the light from those events are billions of years old due to light years 2. What is triangulation used to calculate? Wha...

## SCIENCE 10 - ASTRONOMY UNIT REVIEW ### MEMORIZE 1. How can astronomers directly observe events that took place in the early universe several billion years ago? - Because the light from those events are billions of years old due to light years 2. What is triangulation used to calculate? What information do astronomers need to perform a triangulation calculation? - Distance between celestial bodies, angles and baseline 3. Why does the accuracy of triangulation decrease with distance to a star under study? - All angles become similar to 90 degrees 4. Mars has a larger orbit than Earth. If you could use a rover on Mars to measure angles for triangulation, how would this be an advantage? - Larger baseline = More accurate results 5. How can parallax be used to explain the movement of objects on the celestial sphere? - Pax Parallax is the distance objects "move" when viewed from different angles. 6. What causes electromagnetic waves to stretch as they move through space? - Expansion of Universe 7. A star is moving through space. In January, most of the electromagnetic radiation from the star that reaches Earth is in the form of UV rays. In July of the same year, the radiation is now mostly X-rays. Is the star moving towards or away from Earth? - Away 8. Why are radio telescopes the most practical telescope for use in rainy climates? - It doesn't get blocked 9. Since the universe is still expanding, what type of electromagnetic waves will the CMBR eventually be when they reach us? - Radio waves from Microwave rays ## FORMATION OF ELLIPTICAL AND IRREGULAR GALAXIES - When equally sized spiral galaxies combine, they lose their structure. - Stable orbits are disrupted as stars near each other, resulting in chaos. - After the collision, the stars are still drawn together, but the resulting shape lacks structure, forming an elliptical or irregular galaxy. - When small galaxies collide with large galaxies, the large one tends to "cannibalize" the smaller one without changing shape. - The largest galaxies have undergone many collisions and merging events and many continue to evolve. ## GALACTIC EVOLUTION - **TIME** - Small young galaxy - Spiral galaxy grows as it engulfs small galaxies - A giant elliptical galaxy formed from multiple collisions. ## SCIENCE 10 ASTRONOMY LESSON 7 - GALAXIES (Part 2) ### KEY CONCEPTS - MAKE SURE YOU UNDERSTAND THE FOLLOWING: - Elliptical galaxies are large, round, and lack structure - Irregular galaxies are often small and have no clear shape or pattern. - As the universe expands, most galaxies are moving away from each other. However, galaxies that form in clusters are often pulled together by their gravity. - When spiral galaxies collide, they often form elliptical galaxies - Large galaxies are thought to be formed from the collisions of smaller galaxies. ### ELLIPTICAL AND IRREGULAR GALAXIES - **ELLIPTICAL** galaxies are circular or oval-shaped, puffy (instead of flat) and lack structure. They are usually made of older stars. - **IRREGULAR** galaxies are often small and chaotically shaped. Some unusual looking irregular galaxies are called "peculiar" galaxies ### REVISITING HUBBLE'S LAW - Hubble's law states that galaxies are moving away from each other as the universe expands. This is proven by the **red shift** that most galaxies possess when viewed from Earth. - **GALAXY CLUSTERS** - In the early universe, galaxies formed in regions that had higher density of matter. - Because of this, galaxies often formed in clusters. - A galaxy cluster is a structure in which hundreds to thousands of galaxies are bound by their shared gravity. ### MOVEMENT AND CHANGES IN GALAXIES - What causes galaxies to move away from each other? ANSWER: **Expansion of the universe** - What force could oppose this, pulling galaxies together? **Gravity** within galaxy clusters. - **GALACTIC COLLISIONS** - Galactic collisions happen within galaxy clusters. - The expansion of the universe has resulted in these events becoming less common over time. - The vastness of space and the size of galaxies result in collisions taking place over hundreds of millions of years. - The distances between stars are too vast to result in direct collisions. ## SCIENCE 10 ASTRONOMY LESSON 7 - GALAXIES (Part 1) ### KEY CONCEPTS - MAKE SURE YOU CAN ANSWER THE FOLLOWING: - Define the following terms: single star system, binary star system, multi-star system and star cluster - What type of star system is our sun in? - What are the three shapes of galaxies? - In a spiral galaxy, identify the galactic center and spiral arms. - Where do new stars form in a spiral galaxy? Explain why. ### STAR SYSTEMS - Our sun is a **single star system**. It does not orbit around any other stars. But since stars are formed in nebulas, they tend to form in groups and become gravitationally bound. This is particularly common with high-mass stars. For this reason, single-star systems are relatively uncommon. They usually only happen with low-mass stars. - A **binary star system** is a system in which two stars orbit around each other. - A **multi-star system** is a system in which three or more stars orbit around each other (solar system only has stars- galaxies have many more things) - A **star cluster** is a large group of stars held together by gravity (not the same as a galaxy) ### GALAXIES - A galaxy is a vast system of stars, gas, dust, and dark matter held together by gravity. Most contain 100 million to 500 billion stars. - There are three shapes of galaxies: - Elliptical - Spiral - Irregular - **Spiral Galaxy - a thin disk of stars rotating around a galactic center** - Includes the Milky Way (our galaxy) - **Galactic center** (center of the galaxy) is primarily made up of older stars. - **Spiral arms** move faster than the galactic center. Their movement launches gas and dust outwards which combine to form large nebulas. - **Stars are formed in the spiral arms** (empty area is gas and dust). ## SCIENCE 10 ASTRONOMY LESSON 7 - GALAXIES ### PRE-READING ASSIGNMENT: - Read pages 326 and 331 in your textbook and the "Galaxies - Building Blocks of the Universe" article and answer the following: 1. What holds galaxies together? - Galaxies are mainly made up held together by gravity 2. When galaxies collide, do their stars crash into each other? Why or why not? - No, due to the large immense distances between them. 3. What did Vera Rubin initially notice about the rotation of the Andromeda Galaxy that contributed to the discovery of dark matter? - When she was studying the spin of galaxies, she realized the vast spiral of the Andromeda galaxy seemed to be rotating strangely, a violation of Newton & Kepler's laws: material moving at edges moving just as fast as material near the center are usually older, even though most mass is usually older. 4. Which type of galaxy is usually older? - Elliptical galaxies 5. What is a star cluster? - A star cluster is a concentrated collection of stars held together by its own gravity, inside or around the galaxies. 6. Which galaxy will eventually collide with the Milky Way? When will this occur? - The Milky Way galaxy is estimated to collide with the Andromeda galaxy in about 4 billion years. 7. Why do elliptical galaxies form? - Astronomers theorize that these are formed by the mergers of smaller galaxies. ## THE H-R DIAGRAM 1. What is the approximate surface temperature of the sun? - 6000°C 2. Would the surface temperature of white dwarf stars be higher or lower than red supergiants? (Circle one of the bold words). - lower 3. What is the color of the stars with the highest surface temperature? - Blue 4. What is the color of the stars with the lowest surface temperature? - Red 5. List the color of the stars from hottest to coldest: - Blue --> Blue-white --> White --> Yellow-white --> Yellow --> Orange --> Red 6. Most of the stars on the HR Diagram are classified as which type of star? - Main sequence stars 7. How is it possible for white dwarf stars to have lower luminosity than the sun even though the sun is cooler than white dwarfs? - They are much smaller and have less surface area. So, the luminosity given off is less energy. ## THE HERTZSPRUNG-RUSSELL DIAGRAM - The Hertzsprung-Russell diagram is actually a graph that illustrates the relationship that exists between the average surface temperature of stars and their absolute magnitude, which is how bright they would appear to be if they were all the same distance away. Rather than speak of the brightness of stars, the term "luminosity" is often used. Luminosity is a measure of how much energy leaves a star in a certain period of time. Generally, for stars that are at equal distances from the Earth, the more luminous a star, the brighter it is The luminosity of stars is affected not only by temperature but also by size. The most luminous stars would be those that are large and hot. Those that are the least luminous would be small and cool. The color of a star is determined by its surface temperature, which is illustrated on the Hertzsprung-Russell diagram. ## SCIENCE 10 LESSON 6 - HERTZSPRUNG - RUSSELL DIAGRAMS ### BACKGROUND INFORMATION: - Two major characteristics of stars are their **color** and their **brightness** AKA **magnitude** ### BRIGHTNESS IS MEASURED IN TWO WAYS: - **Absolute magnitude** = the brightness of the star if it was a **10 parsecs** away from earth (about 32.6 light years) - **Apparent magnitude** = the brightness of the star as seen from earth. - Magnitude is given with the value of a number. The smaller the number, the brighter the star. [000] - **Color depends on and is determined by the star's surface temperature: ** - Hotter temperatures are **blue** in color. - Cooler temperatures are **red** in color. - True brightness depends on the star's size. - The larger the star is the brighter it is. - The smaller the star is the less bright it is. (BlueshiftxRedShift). - Two astronomers used this information and created the Hertzsprung - Russell diagram. Star color or the temperature is plotted on a graph against true brightness. Sometimes luminosity is also plotted on the diagram. ### LUMINOSITY - Luminosity is a measure of **how much energy** leaves a star in a certain period of time. - Generally, the more luminous a star is, the brighter the star is. The luminosity of a star is not only affected by temperature but also by size. The most luminous stars would be those that are large and hot and the least luminous would be small and cool. In some cases, there are exceptions to this rule. ## SCIENCE 10 ASTRONOMY LESSON 5 - THE LIFECYCLES OF STARS ### KEY CONCEPTS IN THIS LESSON - What is a protostar? - What is a solar mass? - How do heavy elements form in the core of stars? - Why do stars run out of fuel and collapse? - What is the difference between luminosity and absolute magnitude? - What is the main sequence? - What is a red giant and how does it form? - What is a supernova and how does it form? ### NEBULAS AND PROTOSTARS - **A nebula** is a cloud of gas and dust, mostly made of hydrogen and helium from its **parent nebula** - **A protostar** is a young star that is still collecting matter ### SOLAR MASS - The standard unit for mass in stars is the solar mass, which equals the mass of our sun. - One solar mass = 10x10^30 kg - **Low mass stars**: <1 solar mass - **Intermediate-mass stars**: 1 - 10 solar masses - **High mass stars**: 10+ solar masses ### NUCLEAR FUSION - Nuclear fusion occurs in the star's core where temperature & pressure are highest - Main sequence stars convert hydrogen into helium, which continues for the majority of the star's lifespan - Eventually the core runs out of hydrogen and is entirely made of helium. - Helium then fuses into carbon until the core is entirely made of carbon. - This process continues with the fusion of heavier elements until the core is entirely made of iron. ### STAR DEATH - When a star's core is entirely made of iron, it is said to be out of fuel. This is because any further fusion reactions would not be exothermic (reactions after iron don't release any thermal energy. - The sudden lack of heat allows gravity to counteract the outward force, and the star begins to collapse. - What occurs after a star's core collapses depends on the mass of that star. ## SCIENCE 10 ASTRONOMY LESSON 4 - GRAVITY AND THE FORMATION OF STARS ### KEY CONCEPTS IN THIS LESSON - MAKE SURE YOU CAN ANSWER THE FOLLOWING: - What does gravitational force act on? - What are the two variables that affect gravity? - What two forces interact in the formation of stars? - How do stars avoid gravitational collapse? - What does it mean when a star is in equilibrium? ### GRAVITY - **Newton**: An **attractive force** between all objects with mass - **Einstein**: The bending of **space and time** - Every object with mass **attracts** every other object with mass. - Gravity is affected by the **mass** of objects **and their distances** from each other. - Gravitational force **increases** with mass. - Gravitational force **decreases** with distance between objects AND THE VELOCITY OF OBJECTS. ### THE FORMATION OF STARS - The process starts with a nebula - a large cloud of gas and dust in space. - There are two forces acting on the nebula that we will focus on: - **Gravity** between all particles pulls matter inwards. We'll call this the inward force. - **Kinetic energy** of all particles pushes matter outwards. We'll call this the outward force. - Eventually, as the nebula grows (from collecting more matter), the nebula starts collapsing on itself and forming a spinning disk with a hot and dense center. - Gravity continues to increase pulling matter in faster. - Eventually the **temperature and pressure** in the core of the gas cloud results in atoms breaking apart, forming **plasma**. - Small, light nuclei **collide** forming heavier nuclei and releasing **energy through nuclear fusion**. - Since the kinetic energy of the matter is now much higher, the outward force now matches the inward force. The star is in **equilibrium**. ## SCIENCE 10 ASTRONOMY LESSON 3 - THE BIG BANG ### PRE-READING IN-CLASS ASSIGNMENT - Read pages 354-361 in your textbook. - Read the provided article "Evidence for the Big Bang." ### ANSWER THE FOLLOWING QUESTIONS: 1. What does the big bang theory state? - The big bang theory is a theory which explains the origin of the universe, and questions such as how the universe began, will end, changed and has changed. 2. How has the Doppler effect provided evidence for the big bang? - The Doppler effect provided evidence for the Big Bang since it indicated to Hubble's law - the speed of the galaxy from Earth, which comes from red shift, is proportional to the distance of the galaxy. 3. What is Hubble's Law? - Hubble's Law states that the speed of a galaxy is proportional to the distance of the galaxy from Earth. (1 parsec = 3.26 light years) 4. What is the cosmic microwave background (CMB) radiation? - CMB radiation is radiation left over from the Big Bang, which is present beyond the Milky Way. It implies that the universe is expanding. 5. Why does the radiation left over from the big bang have longer wavelengths now than it did in the early universe? - It has longer wavelengths because they are stretched as the universe expanded, turning gamma rays to visible light to the microwave part of the spectrum. 6. How many years after the big bang did it become possible for electrons to bind to atoms? - It took around 380,000 years for electrons to bind atoms after light and gravity slowed the growth of the universe. ## SCIENCE 10 ASTRONOMY LESSON 2 - LIGHT IN SPACE ### KEY CONCEPTS AND SKILLS - MAKE SURE YOU CAN ANSWER THE FOLLOWING: - What is electromagnetic radiation? - What are the types of light included in the electromagnetic spectrum? - What is the relationship between wavelength, frequency, and energy? - What types of electromagnetic radiation are most effective at reaching Earth's surface? - What are two types of telescopes that detect electromagnetic radiation beyond visible light? - Where are they used? - What is the Doppler effect? What is it caused by? - What are red shift and blue shift? What do they say about an object's motion? ### THE ELECTROMAGNETIC SPECTRUM - **Electromagnetic radiation** is **radiant energy**. - **Consists of waves** that travel at the speed of light. - Includes radio waves, microwaves, infrared waves, visible light, ultraviolet light, x-rays, and gamma rays. - Each of these have different **wavelengths and frequency**. ### WAVELENGTH AND FREQUENCY - **Wavelength** is the distance between each repeating point of a wave. - **Frequency** is the number of wavelengths that pass through a point in a set amount of time. - Because long waves take more time to pass through a point, they lead to a lower frequency. Short wavelengths lead to higher frequency. - **What is the relationship between wavelength, frequency, and energy?** - High frequency = high energy = low wavelength ### ELECTROMAGNETIC RADIATION IN SPACE - Objects in space emit many kinds of electromagnetic radiation. A lot of this radiation doesn't reach Earth's surface. Some types are better at penetrating the atmosphere than others. - Visible light and radio waves reach Earth's surface most easily. Radio waves can also penetrate through clouds. ### TELESCOPES - A **radio telescope** is an antenna and receiver device that detects **radio waves** from space. - Radio telescopes can still be used if there are clouds. They can also be used at any time of day or night. ## SCIENCE 10 ASTRONOMY LESSON 1 - MEASURING DISTANCE AND MAPPING SPACE ### KEY CONCEPTS AND SKILLS: - Define the celestial sphere - 1 AU = distance from Earth to Sun - Explain the effect of parallax on the apparent positions of objects in the celestial sphere - Define light years and what they measure - Explain why light years are useful in astronomy - Identify what triangulation is used for and why - Understand and explain the roles of parallax and the baseline in triangulation - Explain the procedure of triangulation ### PART 1: READ THE FOLLOWING PASSAGES IN YOUR TEXTBOOK AND ANSWER THE QUESTIONS **Pages 308-309** 1. What is the celestial sphere? - The appearance and motions of objects we can visibly see can be described using a celestial sphere. The celestial sphere is an imaginary rotating sphere in which all objects of the night sky are located. 2. What causes celestial objects to appear to move across the sky? - The Earth's rotation causes celestial objects to appear to move across the sky from east to west. The distance of celestial objects can also play a role in how they are observed from Earth. 3. What are the two types of motion that the earth undergoes, causing the appearance of the night sky to change over time? - The Earth's rotation causes celestial objects to appear to move across the sky from east to west. In addition, our view of the night sky changes with every passing season due to Earth's revolution around the Sun. **Pages 334-336** 1. What is a light-year? Is it a measure of distance or time? - It is a measure of distance. ## SCIENCE 10 ASTRONOMY LESSON 1 - MEASURING DISTANCE AND MAPPING SPACE ### PART 2: READ THE FOLLOWING PASSAGES IN YOUR TEXTBOOK AND ANSWER THE QUESTIONS 1. What are the two ways that astronomers can determine the distances to stars? - By using standard candles: When a star is a standard candle, it is an object whose luminosity can be determined with high certainty. - By using the trigonometric parallax method: The angle between the observer on Earth and the star changes as Earth moves throughout the year. This change in the angle can then be used to calculate the distance to the star. 2. Why is parallax needed for triangulation? - The apparent shift when viewing an object is the distance to that object. It allows astronomers to measure different angles between Earth and an object, which they can use to calculate distances. 3. How can astronomers use parallax to triangulate the distances to stars? - Astronomers observe a nearby star's position from different places. The distance between the two places where the astronomer observes the star is called the baseline. The angle between the distant star and the two ends of the baseline is the parallax. The closer the star is, the more parallax is observed. Then astronomers use trigonometry to find the distance to the star. 4. What is the relationship between the baseline and parallax? - The longer the baseline is, the greater the parallax will be. Conversely, the shorter the baseline is, the smaller the parallax will be. Therefore, the parallax of a star is inversely proportional to its distance. The greater the parallax, the closer the star is, and the smaller the parallax, the greater the distance to the star. 5. How can astronomers use parallax to determine the distance to faraway stars? - They observed the apparent positions of a star at two different times of the year when the Earth is at opposite location in its orbit — 6 months apart. They then calculated the parallax of the star. - Astronomers can determine the distances to stars up to about 100 parsecs using parallax. (1 parsec = 3.26 light-years) 6. What effects do the expansion of the universe and the Doppler effect have on the distances to stars? - Due to the expansion of the universe, the farther away a galaxy is, the faster it is moving away from us. It appears as if the galaxy is moving very quickly. - Astronomers use a phenomenon called **red shift** to track the expansion of the universe. This phenomenon allows astronomers to determine the movement of stars and galaxies by shifting the spectrum emitted by stars towards the red end of the spectrum as they move away from us. ## SCIENCE 10 ASTRONOMY LESSON 1 - MEASURING DISTANCE AND MAPPING SPACE ### PART 3: READ FOLLOWING PASSAGES IN YOUR TEXTBOOK AND ANSWER THE QUESTIONS. **Pages 308 - 309** 1. What is the celestial sphere? - The appearance and motions of objects we can visibly see can be described using a celestial sphere. The celestial sphere is an imaginary rotating sphere in which all objects of the night sky are located. 2. What causes celestial objects to appear to move across the sky? - The Earth's rotation causes celestial objects to appear to move across the sky from east to west. The distance of celestial objects can also play a role in how they are observed from Earth. 3. What are the two types of motion that the Earth undergoes, causing the appearance of the night sky to change over time? - The Earth's rotation causes celestial objects to appear to move across the sky from east to west. - In addition, our view of the night sky changes with every passing season, due to Earth's revolution around the Sun. **Pages 334-336** 1. What is a light-year? Is it a measure of distance or time? - It is a measure of distance, as it is the distance that light travels in one year. 2. What are standard candles, and how can astronomers use them to find the distances to starts? - A standard candle is an object whose luminosity is determined with high certainty. An example of a standard candle that is commonly used is a **Cepheid variable star**. Cepheid variable stars have a period-luminosity relationship between the time it takes them to go through their pulsating cycles and their absolute magnitude. Astronomers can use this relationship to find the distances to these stars and galaxies. # SCIENCE 10 ASTRONOMY LESSON 3 - THE BIG BANG 1. What is the Cosmological Principle, and what are its consequences? - The Cosmological Principle is a fundamental principle in cosmology, and it states that the universe is homogeneous and isotropic on the largest scales. - Consequences: - The universe does not have a center or a special location. - The physical laws of the universe are the same everywhere. 2. What evidence supports the Big Bang Theory? - **Red Shift**: The redshift seen in the light from distant galaxies indicates that the universe is expanding, as predicted by the Big Bang theory. - **Cosmic Microwave Background Radiation**: The detection of the cosmic microwave background radiation (CMB) is a crucial piece of evidence supporting the Big Bang theory. The CMB is a faint afterglow of the Big Bang, and its properties are consistent with the theory. - **Abundance of Light Elements**: The abundance of light elements in the universe, such as hydrogen and helium, is consistent with the predictions of the Big Bang theory. These elements were created in the very early universe. # SCIENCE 10 ASTRONOMY LESSON 2 - LIGHT IN SPACE 1. Why do astronomers use telescopes to study the universe? - Telescopes allows astronomers to gather and focus light from distant objects in space to study them, which allows them to observe more detail. They also allow astronomers to detect electromagnetic radiation beyond the visible spectrum. 2. Why are ultraviolet telescopes often placed in space? - Because Earth's atmosphere absorbs most ultraviolet radiation. 3. What are the two main types of telescopes used to study the universe? - **Optical telescopes**: These telescopes are designed to detect and focus visible light. - **Radio telescopes**: These telescopes are designed to detect and focus radio waves. # SCIENCE 10 ASTRONOMY LESSON 4 - GRAVITY AND THE FORMATION OF STARS 1. How does gravity act on objects with mass? - Gravity is an attractive force that pulls objects with mass towards one another. The more massive an object is, the greater the gravitational pull it exerts. 2. How do astronomers use spectroscopy to study stars and galaxies? - Spectroscopy analyzes the light emitted by stars and galaxies to determine their composition, temperature, and speed. It can also be used to identify specific elements that have been absorbed or emitted by the object. # SCIENE 10 ASTRONOMY LESSON 7 - GALAXIES 1. How do astronomers determine the ages of galaxies? - Astronomers determine the ages of galaxies by observing the population of stars that they contain. Older galaxies have a greater proportion of older, redder stars, while younger galaxies have a greater proportion of younger, bluer stars. 2. What is a quasar, and how is a quasar related to a black hole? - A quasar is a very luminous, distant, and extremely energetic object in space. - A quasar is powered by a supermassive black hole at the center of a galaxy. - As material falls into the black hole, it gets heated up and emits huge amounts of energy in the form of electromagnetic radiation. 3. What is the difference between a spiral galaxy and an elliptical galaxy? - **Spiral galaxy**: These galaxies are characterized by their spiral arms, which are regions where new stars are still forming. - **Elliptical galaxy**: These galaxies lack spiral arms and have a smooth, rounded shape. Most of the stars in these galaxies are older and redder. # SCIENCE 10 ASTRONOMY LESSON 5 - THE LIFECYCLES OF STARS 1. What is the significance of the main sequence in the life cycle of a star? - The main sequence is the longest stage in the life cycle of a star. During this stage, a star is stable and is primarily fusing hydrogen into helium in its core. 2. What happens to a star when it runs out of hydrogen fuel in its core? - Once a star has used up all of its hydrogen fuel in its core, it begins to collapse under its own gravity. This results in the star becoming a **red giant**. 3. How does a white dwarf form? - A white dwarf forms at the end of the life of a low-mass star. - When a red giant runs out of fuel, it expels its outer layers into space, forming a planetary nebula. - The core of the star collapses into a very dense and small-mass object called a white dwarf. 4. What happens during a supernova? - In a supernova, a very massive star explodes at the end of its life. - The explosion releases an immense amount of energy, creating heavy elements, and scattering them into space through the shock waves. - The core of the star may collapse into a neutron star or black hole. # SCIENCE 10 ASTRONOMY LESSON 6 - HERTZSPRUNG - RUSSELL DIAGRAMS 1. What is the relationship between a star's mass and its lifetime? - The more massive a star is, the shorter its lifetime. - More massive stars burn through their fuel much faster than less massive stars, because they have a higher density of hydrogen in their cores. 2. Where are white dwarfs located on the Hertzsprung-Russell diagram? - They are located in the lower left portion of the diagram. 3. What is the significance of the main sequence on the Hertzsprung-Russell diagram? - The main sequence represents the stage in a star's life during which the star is stable and is primarily fusing hydrogen into helium in its core. - It includes most of the stars in the universe and is the longest stage of a star's life. - The location of a star on the main sequence is determined by its mass and temperature. # SCIENCE 10 ASTRONOMY LESSON 1 - MEASURING DISTANCE AND MAPPING SPACE 1. How do astronomers use trigonometry to determine the distances to stars? - They measure the angles between the distant star and two ends of the baseline. - The longer the baseline is, the greater the parallax will be. Conversely, the shorter the baseline is, the smaller the parallax will be. Therefore, the parallax of a star is inversely proportional to its distance. The greater the parallax, the closer the star is, and the smaller the parallax, the greater the distance to the star. 2. What are the advantages and disadvantages of using parallax to determine distances to stars? - **Advantages**: Parallax is a direct and reliable method for measuring distances to nearby stars. - **Disadvantages**: Parallax measurements get less accurate for stars that are farther away. It becomes extremely difficult to measure parallax for stars that are beyond a certain distance. 3. Why are standard candles important for astronomers? - Astronomers can use standard candles to find the distances to galaxies that are too far away for parallax measurements. 4. What are some examples of standard candles used in astronomy? - Cepheid variable stars - Type Ia supernovae 5. How is the size of the observable universe related to the age of the universe? - The size of the observable universe is related to the age of the universe because light has a finite speed. - The observable universe is the portion of the universe that we can see from Earth. - The farther away an object is, the longer its light has taken to reach us. - Therefore, we can only observe objects that are within a certain distance from us, limited by the age of the universe. # SCIENCE 10 ASTRONOMY LESSON 3 - THE BIG BANG 1. What is the relationship between the wavelength of light and the Doppler effect? - The Doppler effect causes a change in the wavelength of light when the source of the light is moving relative to the observer. - If the source of the light is moving towards the observer, the wavelength of the light is compressed, resulting in a **blueshift**. - If the source of the light is moving away from the observer, the wavelength of the light is stretched, resulting in a redshifted. 2. Why is the Cosmic Microwave Background Radiation considered evidence for the Big Bang? - It's the faint afterglow of the Big Bang, a prediction made by the Big Bang theory. - It's a uniform, low-energy background radiation that fills the entirety of the universe. - This radiation is very consistent with the model of an expanding universe after the Big Bang. 3. How do astronomers use the Doppler effect to confirm the expansion of the universe? - Astronomers observe the light emitted by distant galaxies. - They notice that the light from these galaxies is redshifted, implying that the galaxies are moving away from us. - The more distant the galaxy, the greater the redshift, suggesting that the universe is expanding. # SCIENCE 10 - ASTRONOMY LESSON 2 - LIGHT IN SPACE 1. Why are optical telescopes often placed on mountain tops? - The higher altitude reduces the amount of the atmosphere, which can distort light. This is a structured markdown format of the information provided. All the text and any image descriptions available are shown in order with the correct formatting. There were some repeated headings and descriptions, so I only showed them once. For example, there were two explanations of the Doppler effect, but the text is the same, so I only showed it once.