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Join us on a video field trip to learn about the fascinating life and death of stars. Discover what happens when stars run out of fuel and what will happen to the sun when it dies. Explore the characteristics of stars, including their temperature, colors, and properties. Learn about binary star systems and how they help us determine the most difficult star property to calculate - its mass. Dive into measuring the distance to stars through parallax and the concept of light-years. Understand the importance of stellar brightness, from apparent magnitude to absolute magnitude. Explore the Hertzsprung-Russell diagram and the different types of stars. Finally, delve into the mysterious world of interstellar matter, including nebulae and dark nebulae like the famous Horsehead Nebula. Watch the video and read Chapter 25, Section 1 to expand your knowledge about the captivating world of stars.
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Video Field TripStars: Life and Death • What happens when stars run out of fuel? • What will happen when to the sun when it dies?
Properties of Stars Chapter 25, Section 1
Characteristics of Stars • Color is a clue to a star’s temperature • Very hot (30,000 K) stars emit their light in the blue spectrum, red stars are much cooler, stars with temperatures between 5000 and 6000 K appear yellow • Binary Stars – pairs of stars, pulled together by gravity, that orbit each other • Binary stars are used to determine the star property most difficult to calculate – its mass • The mass of a body can be calculated if it is attached by gravity to a partner
Concept Check • What is a binary star system?
Measuring Distance to Stars • Parallax is determined by taking a picture of a star at one time, and another picture six months later; using the angle between its apparent shift, astronomers can determine how far away it is • The nearest stars have large parallax angles, while those of distant stars are too small to calculate • Light-Year – unit used to express stellar distance, the distance light travels in one year (~9.5 trillion kilometers) • Our closest star (besides the sun), Proxima Centauri, is about 4.5 light-years away from the sun
Stellar Brightness • Apparent Magnitude – a star’s brightness as it appears to Earth • Three factors control the apparent brightness of a star as seen from Earth: how big it is, how hot it is, and how far away it is • Absolute Magnitude – how bright a star actually is • To determine absolute brightness, astronomers measure how large the star is, what temperature it is, and what its apparent brightness would be at 32.5 light-years
Concept Check • What is the difference between apparent magnitude and absolute magnitude?
Hertzsprung-Russell Diagram • A Hertzsprung-Russell diagram shows the relationship between the absolute magnitude and temperature of stars • Main-Sequence Star –This category contains the majority of stars and runs diagonally from the upper left to the lower right on the H-R diagram • Red Giants – a large, cool star of high luminosity • Supergiants – a very large, very bright red giant star • Cepheid Variables – A star whose brightness varies periodically because it expands and contracts, a type of pulsating star • Nova – A star that explosively increases its brightness
Concept Check • The H-R diagram shows the relationship between what two factors?
Interstellar Matter • Nebulae – clouds of dust and gases in space • Emission nebulae consist largely of hydrogen, they absorb ultraviolet radiation emitted by nearby stars • Reflection nebulae merely reflect the light of nearby stars • Astronomers like to study nebulae because stars and planets form from them
Assignment • Read Chapter 25 Section 1 (pg. 700-706) • Do Section 25.1 Assessment #1-7 (pg. 706)
