The Sun and the Life Cycles of Stars
Read the article below about the Sun, its characteristics, and its importance in the solar system. Study the diagrams and images below carefully. After reading, answer the short answer questions using information from the article.
Group 1
Source 1.1
The Sun: Our Star and Its Role in the Solar System
The Sun is a medium-sized star located at the center of our solar system. It is classified as a G-type main-sequence star (G dwarf) and is the closest star to Earth. The Sun’s gravity holds the solar system together, keeping planets, asteroids, and comets in orbit around it.
Source 1.2
Nuclear Fusion and Energy Production
The Sun produces energy through a process called nuclear fusion. In its core, hydrogen atoms are fused together to form helium, releasing enormous amounts of energy in the form of light and heat. This energy travels outward from the core and eventually reaches Earth, providing the light and warmth necessary for life.
Source 1.3
Size, Temperature, and Color
The Sun has a diameter of about 1.39 million kilometers (about 109 times the diameter of Earth). Its surface temperature is approximately 5,500°C (9,932°F), while the core can reach temperatures of about 15 million°C (27 million°F). The Sun appears yellow to our eyes, but it actually emits all colors of visible light. Its color is due to its surface temperature, which places it in the middle of the Hertzsprung-Russell (H-R) diagram, a graph that classifies stars by their luminosity and temperature.
Source 1.4
Size, Temperature, and Color cont.
Source 1.5
The Hertzsprung-Russell Diagram
The H-R diagram is a tool that astronomers use to study the properties and life cycles of stars. Most stars, including the Sun, are found along the main sequence, where they spend most of their lives fusing hydrogen into helium.
Source 1.6
Life Cycle of the Sun and Other Stars
The Sun is about 4.6 billion years old and is considered a middle-aged star. In the future, it will expand into a red giant as it uses up its hydrogen fuel. Eventually, it will shed its outer layers and leave behind a dense core called a white dwarf. More massive stars end their lives in spectacular explosions called supernovae, which can leave behind neutron stars or black holes.
Source 1.7
The Sun’s Importance
The Sun’s energy drives weather, climate, and photosynthesis on Earth. Without the Sun, life as we know it would not exist. Studying the Sun helps scientists understand not only our own star, but also the life cycles and behaviors of stars throughout the universe.
Question 1a
Explain how the process of nuclear fusion in the Sun’s core is essential for life on Earth. Use evidence from the article to support your answer.
Question 1b
Based on the Hertzsprung-Russell diagram, why is the Sun classified as a main-sequence star, and what does this classification tell us about its current stage in the stellar life cycle?
Question 1c
Compare the future life cycle of the Sun to that of a much more massive star. What are two key differences in how they end their lives?
Question 1d
The Sun appears yellow to us, but it actually emits all colors of visible light. What does this tell us about the relationship between a star’s temperature and its color?
Question 1e
Describe one way in which studying the Sun can help scientists learn about other stars in the universe. Use information from the article and your own reasoning.
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