Learning Objective Check-Writing Assignment Essay

Describe the nuclear fusion reaction that occurs in stars. Page 294 Stars are made primarily of the almond hydrogen the most common material universe. As a star forms, gravity pulls the hydrogen into a dense ball that heats up. Electrons are torn from the hydrogen and other atoms, creating a plasma made up primarily of protons (the nucleus of the hydrogen atom) and electrons. Normally, protons would repel each other. As matter accumulates ending the new star however, the protons move faster as the temperature increases. Eventually they acquire enough energy to come over the electrical repulsion between them.

They start to fuse. The nuclear fusion process in the sun’s core does not take place all at once with four particles suddenly coming together to make a helium-4 nucleus. 2. Describe how the nebular hypotheses explain 3 major types of stars: main-sequence stars, red giants, and white dwarfs. Page 298 Stars such as our own Sun form from giant clouds on interstellar dust called nebulae-call that generally collapsed under the force and gravity. This collapse subjects the stars atoms, primarily hydrogen to tremendous temperatures and pressures.

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The life of the star is a continuous struggle against this gravitational Orca. Stars that are burning hydrogen to produce energy are said to be main sequence stars. Large stars burn hotter and admit more energy, while smaller stars are cooler and Radiate less energy. Main-sequence stars are found any simple band-like pattern on a Heartstrings-Russell diagram, which graphs a stars energy output versus its temperature. When a star like the sun consumes most of its core hydrogen, a hydrogen rich central region remains. The star once again begins to collapse under gravity, and internal temperature is rise again.

Hydrogen burning begins in shells outside the core while the cores helium may also combined in nuclear fusion reactions to form Carbon. These new nuclear processes may cause a star like the sun to expand briefly and become a red giant, a star is relatively cool outer layers glow red. Eventually however nuclear fuel must be exhausted. Gravity will dominate and the carbon rich star will collapse to a very small, very hot white dwarf. 3. Describe the size and history of the universe. Page 31 0 The history of the universe as being composed of a series of events called freezing.

Moving backward in time from the present, the most recent freezing kook place when the universe was about 500,000 years old. Before this time, it was too hot for atoms to stay together, whereas after this time atoms, once formed, could survive. After the universe was three minutes old nuclei could stay together where as before this was only elementary particles existed. When the universe was 10-5 Second old, quarks coalesced into elementary particles. The Milky Way is a rather typical galaxy. It is a flattened desk about 100,000 light- years across. A central bulge known as the nucleus holds most of our galaxies hundreds of billions of stars.

Bright region in the disk, known as spiral arms, mark areas where new stars are being formed. About 75% of the brighter galaxies in the sky are spiral type. 4. Differentiate normal matter, dark matter, and dark energy. Page 321 Dark matter is material that exists in forms that do not interact with electromagnetic radiation and that may constitute 90% of the matter of the universe. Dark energy is another force, a sort of integrative, acting to push galaxies apart. The search for dark matter mass that we cannot see with our telescopes is a research frontier that may help us determine whether the universe will continue expanding forever.

Recent data tells us that the expansion of the universe is accelerating in fact that scientists attribute to something called dark energy. 5. Discuss the structure and history of the solar system. Page 340 First formed along the Sun and other planets in our solar system form a nebula- a large gas and dust cloud rich in hydrogen and helium-approximately 4. 5 billion years ago. As the cloud began to contract as a result of gravitational forces, it also began to rotate and flatten out into the disk that’s now defines planetary orbits. More than 99% of the original nebulas Mass concentrated at the center, which became the sun.

Gradually, the matter in the flap desk began to form clumps under the influence of its own local gravitational forces. The largest of these masses swept up more and more debris as they orbit the early sun, and they begin to define a string of planets. Terrestrial planet, there is nearest the sun, were subjected to high temperatures and strong solar Wane’s comments so that most gases such as hydrogen, helium, and water vapors were swept out into space. Thus the dinner four planets, including Mercury, Venus, Earth and Mars, are dense rock places with a relatively low content of gaseous elements. . Explain how new knowledge in astronomy and cosmology is attained. Early in the 20th century, Edward Hubble made to extraordinary discoveries about the structure and behavior of the universe, the science was called cosmetology. First he demonstrated that our home, the collection of stars then is the Milky Way, is just one of countless galaxies in the universe, each containing billions of stars. By measuring the red shift of galaxies he also discovered that these distant objects are moving away from each other. According to Hubbub’s law, the farther the galaxy, the faster it is moving away.

This relative motion of implies that the universe is expanding. 7. Describe the effect of reediest. Page 31 1 Early in the 20th century, Edward Hubble made to extraordinary discoveries about the structure and behavior of the universe, the science was called cosmetology. First he demonstrated that our home, the collection of stars then is the Milky Way, is just one of countless galaxies in the universe, each containing billions of stars. By measuring the red shift of galaxies he also discovered that Hess distant objects are moving away from each other.

According to Hubbub’s law, the farther the galaxy, the faster it is moving away. This relative motion of implies that the universe is expanding. Hubble interpreted this red shift as an example of the Doppler effect. 8. Explain the nebular hypothesis. Page 332 According to the nebular hypothesis, long ago (about 4. 5 billion years ago based on radiometric dating) a large cloud of dust and gas collected in the region now occupied by the solar system. Such dust and gas clouds, called nebulae, are common throughout our galaxy, the Milky Way.

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