Stars And The Universe (continued 1)
Overview
The Sun is just one ordinary star among hundreds of billions in our galaxy, the Milky Way, and the Milky Way is just one galaxy among billions in the Universe. Across these vast distances, measured in light-years, stars are born, shine for ages, and die in spectacular ways.
In this lesson you will learn how galaxies, stars and the Milky Way fit together, what a light-year is and its value in metres, and the full life cycle of a star from a cloud of gas to a white dwarf, neutron star or black hole. You will see how the death of one star seeds the birth of the next.
Objectives
- State that: (a) galaxies are each made up of many billions of stars (b) the Sun is a star in the galaxy known as the Milky Way (c) other stars that make up the Milky Way are much further away from the Earth than the Sun is from the Earth (d) astronomical distances can be measured in light-years, where one light-year is the distance travelled in (the vacuum of) space by light in one year
- [Supplement] Know that one light-year is equal to 9.5 × 1015 m
- [Supplement] Describe the life cycle of a star: (a) a star is formed from interstellar clouds of gas and dust that contain hydrogen (b) a protostar is an interstellar cloud collapsing and increasing in temperature as a result of its internal gravitational attraction (c) a protostar becomes a stable star when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the centre of the star (d) all stars eventually run out of hydrogen as fuel for the nuclear reaction (e) most stars expand to form red giants and more massive stars expand to form red supergiants when most of the hydrogen in the centre of the star has been converted to helium (f) a red giant from a less massive star forms a planetary nebula with a white dwarf star at its centre (g) a red supergiant explodes as a supernova, forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole at its centre (h) the nebula from a supernova may form new stars with orbiting planets
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Lesson Evaluation
Congratulations on completing the lesson on Stars And The Universe (continued 1). Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
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Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- The Sun is a star in the galaxy known as the: A. Andromeda B. Milky Way C. Solar System D. Orion Answer: B
- One light-year is equal to: A. 9.5 x 10^12 m B. 9.5 x 10^15 m C. 3.0 x 10^8 m D. 365 m Answer: B
- A star much more massive than the Sun ends its life as a supernova, leaving behind a: A. white dwarf B. planetary nebula C. neutron star or black hole D. protostar Answer: C
- A stable star is one in which gravity is balanced by: A. the magnetic field B. the outward push from its high core temperature C. the solar wind D. nothing Answer: B
- A star 2.0 light-years away is a distance in metres of about: A. 1.9 x 10^16 m B. 4.75 x 10^15 m C. 9.5 x 10^15 m D. 2.0 m Answer: A
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Recommended Books
Further learning from open sources
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Textbook section
Cosmology and Particle Physics
Look at the sky on some clear night when you are away from city lights. There you will see thousands of individual stars and a faint glowing background of millions more. The Milky Way, as it has been called since ancient times, is an arm of our galaxy of stars—the word galaxy coming from the Greek w
"College Physics: Cosmology and Particle Physics" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/34-1-cosmology-and-particle-physics. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
Published by other organisations under open licences, credited as they ask. Links open their websites.
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