Stars - Evolution and using the HR Diagram

Master star life cycles & the HR Diagram! Understand luminosity, temperature & stellar evolution.

ESRT p. 15 - HR Diagram Review Correctly fill in the blanks. Stars are spherical, luminous masses of gasses, mainly hydrogen. They produce energy by nuclear fusion. Fusion occurs in a star's very hot core where hydrogen protons combine to form helium and energy. Stars vary in color and luminosity. The color is caused by its temperature. Cool stars (2,000 - 3,000 K) are the red; hottest starts (~20,000 K) are blue. A star's luminosity is the amount of energy compared to the Sun. Generally the larger the star, the more luminous it is. Dwarf stars are dim; giant starts are bright. Stars are classified based on temperature and luminosity. The "Characteristics of Stars" diagram illustrates the classification system for stars. Ninety percent of stars are main sequence stars. Main sequence stars increase in luminosity as their size and temperature increases. Red dwarfs are small, cool, and dim. The cool red supergiants and giants are bright because of their huge size. The very hot white dwarfs are dim because of their very small size. A star forms within a cloud of gas and dust called a nebula. The mass of dust and gas in the nebula begin to contract because of the force of gravity. This makes the nebula denser and hotter. The nebula will first become a protostar. Then the center of the protostar is dense and hot enough for fusion of hydrogen, a star is "born". The star will spend most of its life as a main sequence star. After millions to billions of years, the star will expand to become a red giant or supergiant. A very massive giant star will eventually supernova (explode) and then become an object so dense that no light can escape called a black hole. A low mass red dwarf star will collapse to form a white dwarf which is extremely hot and dense. Over time, the white dwarf will cool to become a black dwarf. Hotter starts will go through the life cycle more quickly because they use their hydrogen "fuel" faster. Match the vocabulary word with the correct definition. Astronomical Unit A unit of measurement equal to the distance from the Earth to the Sun Light-Year The distance that light travels in one year 13.7 Billion Years The age of the universe 4.6 Billion Years The age of the solar system Galaxy A system of millions or billions of stars Luminosity The brightness of a celestial (space) object Nebula A cloud of gas and dust in space Nuclear Fusion Process by which stars make energy (H+H = He + energy) Star Life Cycle Label the steps in the life cycle correctly. Use the word back in the bottom EXACTLY as shown. Nebula Average Main sequence star Red Giant White dwarf Massive Main Sequence Super Red Giant Neutron star Black hole Supernova Use the HR Diagram to answer the questions. Based on what you know, where on the chart would the sun fall? Upper left region Close to the center Lower right region Which of the following star types ends up bring brightest? blue giants red giants white dwarfs Which of the following star types ends up being coolest in temp? blue giants red giants white dwarfs Determine which statements are true and which are false. True Stars are classified by temperature and luminosity Stars spend the majority of their life as main sequence stars. The Sun is an average, main sequence star. The mass of a star determines its life cycle. The Sun will become a red giant then a white dwarf. False The Sun is a supergiant. Blue stars are coolest and red stars are hottest. The color of a star determines its life cycle. All stars become blackholes Polaris is a white dwarf. The Sun will become a blackhole. Use ESRT p. 15 to answer the questions below. Which star indicated the hottest star surface temperature? blue white yellow red Compared with our Sun, the star Betelgeuse is smaller, hotter and less luminous smaller, cooler and more luminous larger, hotter and less luminous larger, cooler and more luminous Which star is hotter and many times brighter than Earth's Sun? Barnard's Star Betelgeuse Rigel Pollux Which two stars have the most similar luminosity and temperature? Betelgeuse and Barnard's Star Rigel and Betelgeuse Alpha Centauri and the Sun Sirius and Procyon B Compared to the temperature and luminosity of the star Polaris, the star Sirius is hotter and more luminous hotter and less luminous cooler and more luminous cooler and less luminous In nuclear fusion what occurs? Lighter elements are converted to heavier elements Lighter elements are converted to even lighter elements Heavier elements are converted to lighter elements Heavier elements chemically combine with lighter elements Compared to the surface temperature and luminosity of massive stars in the Main Sequence, the smaller stars in the main sequence are hotter and less luminous hotter and more luminous cooler and less luminous cooler and more luminous The temperature of Spica is closest to 2,500 K 3,200 K 4, 000 K 25, 000 k Bellatrix has a surface temperature of 21, 000 K. What is its color? Red Yellow White Blue What is the relationship between Temperature and Luminosity of Main Sequence stars? As temperature increases, luminosity increases. As temperature increases, luminosity decreases. As temperature increases, luminosity stays the same. THE ELECTROMAGNETIC SPECTRUM The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves, infrared light, ultraviolet light, X-rays and gamma-rays. Vocabulary Matching Match the term with the best definition Wavelength the distance between successive crests in a wave. Frequency the rate at which a wave occurs or is repeated over a particular period of time. Electromagnetic Spectrum The range of all possible energy levels of electromagnetic radiation from radio waves to gamma waves. Electromagnetic Radiation The type of energy released by stars consisting of electric and magnetic waves that travel at the speed of light. Fill in the parts of the EM Spectrum on the image below. Use the word bank and write answers exactly as written in the word bank. Word Bank:Infrared UV X-rays Radio Visible Light Microwaves Gamma Radio Microwaves Infrared Visible Light UV X-rays Gamma How does frequency change as you move across the electromagnetic spectrum from radio waves to gamma rays? Increases Decreases Says the same How does wavelength change as you move across the electromagnetic (EM) spectrum from radio waves to gamma rays? Increases Decreases Stays the same When looking at a distant star, an astronomer notices the spectral lines are shifted to the red side (red-shift). What does this indicate to the astronomer? The star is moving towards him. The star isn't moving at all. The star is moving away from him. The star is changing from a main sequence to a red giant.