The Universe Preview Understanding Concepts Reading Skills Interpreting Graphics

Understanding Concepts 1. Inside a star’s core, hydrogen nuclei fuse to form deuterons, which consist of one proton and one neutron. When deuterons fuse with hydrogen nuclei, what do they form? A. plasma B. hydrogen atoms C. hydrogen nuclei D. helium nuclei

Understanding Concepts 1. Inside a star’s core, hydrogen nuclei fuse to form deuterons, which consist of one proton and one neutron. When deuterons fuse with hydrogen nuclei, what do they form? A. plasma B. hydrogen atoms C. hydrogen nuclei D. helium nuclei

Understanding Concepts, continued 2. The hottest stars appear to be which color? F. blue G. green H. red I. yellow

Understanding Concepts, continued 2. The hottest stars appear to be which color? F. blue G. green H. red I. yellow

Understanding Concepts, continued 3. What is the final stage in the life cycle of most stars in our galaxy? A. red giant B. white dwarf C. nebula D. supernova

Understanding Concepts, continued 3. What is the final stage in the life cycle of most stars in our galaxy? A. red giant B. white dwarf C. nebula D. supernova

Understanding Concepts, continued 4. What objects are thought to be the most distant objects in the universe? F. spiral galaxies G. elliptical galaxies H. quasars I. nebulas

Understanding Concepts, continued 4. What objects are thought to be the most distant objects in the universe? F. spiral galaxies G. elliptical galaxies H. quasars I. nebulas

Understanding Concepts, continued 5. About how long does it take light from the sun to reach Earth? A. 8 seconds B. 8 minutes C. 8 days D. 8 years

Understanding Concepts, continued 5. About how long does it take light from the sun to reach Earth? A. 8 seconds B. 8 minutes C. 8 days D. 8 years

Understanding Concepts, continued 6. Why is the light from distant galaxies almost always shifted toward the red end of the spectrum?

Understanding Concepts, continued 6. Why is the light from distant galaxies almost always shifted toward the red end of the spectrum? Answer: They are moving away from us (Doppler effect.)

Understanding Concepts, continued 7. What is the name for the process in which atoms combine to form larger atoms, and where does it take place?

Understanding Concepts, continued 7. What is the name for the process in which atoms combine to form larger atoms, and where does it take place? Answer: Fusion, inside of stars

Understanding Concepts, continued 8. If the Milky Way galaxy has a spiral shape, why do we see it as a streak across the sky?

Understanding Concepts, continued 8. If the Milky Way galaxy has a spiral shape, why do we see it as a streak across the sky? Answer: We are inside the Milky Way and can only see a side view.

Reading Skills AFTER THE BANG Astronomers and physicists generally agree that the universe began about 13 billion to 15 billion years ago in the big bang. For some time after the big bang occurred, the universe was much hotter and denser than it is today. In fact, it was so hot and dense that there were no individual atoms; instead, subatomic particles, including protons, neutrons, and photons (particles of pure energy) made a dense fluid called plasma. Every time that a proton and an electron combined, drawn together by their opposite charges, a photon collided with them and ripped them apart again.

Reading Skills, continued AFTER THE BANG, continued After a few hundred thousand years, the average temperature of the plasma was low enough that the protons could hold onto their electrons to form neutral atoms, and photons could escape without being absorbed.

Reading Skills, continued 9. Why couldn’t stable atoms form before the cooling of the superheated plasma? F. Protons and electrons were moving too fast to combine. G. Before the plasma cooled, subatomic particles carried no charge and therefore were not attracted to one another. H. Colliding with photons caused immediate destruction of any atom that formed. I. Cosmic background radiation prevented the atoms from forming.

Reading Skills, continued 9. Why couldn’t stable atoms form before the cooling of the superheated plasma? F. Protons and electrons were moving too fast to combine. G. Before the plasma cooled, subatomic particles carried no charge and therefore were not attracted to one another. H. Colliding with photons caused immediate destruction of any atom that formed. I. Cosmic background radiation prevented the atoms from forming.

Reading Skills, continued 10. Telescopes show images based on the photons they receive, in the form of light, radio waves, or other radiation. They show us events of the past, because photons take time to travel to us from those events. Why would it be difficult for telescopes to observe events that took place before the cooling of the superheated plasma?

Reading Skills, continued 10. Telescopes show images based on the photons they receive, in the form of light, radio waves, or other radiation. They show us events of the past, because photons take time to travel to us from those events. Why would it be difficult for telescopes to observe events that took place before the cooling of the superheated plasma? Answer: No photons escaped.

Interpreting Graphics The following chart shows the fusion reactions in a large-mass star, which create elements that are heavier than those found in stars like the sun. Use this diagram to answer questions 11 and 12.

Interpreting Graphics, continued 11. Which element fuses to become oxygen? A. carbon B. neon C. silicon D. iron

Interpreting Graphics, continued 11. Which element fuses to become oxygen? A. carbon B. neon C. silicon D. iron

Interpreting Graphics, continued 12. Do the elements that are produced by fusion get heavier or lighter as they get closer to the center of the large-mass star? Why?

Interpreting Graphics, continued 12. Do the elements that are produced by fusion get heavier or lighter as they get closer to the center of the large-mass star? Why? Answer: Heavier; the pressure of gravity.

Interpreting Graphics, continued Astronomers have determined that black holes, with masses from a few million to a billion times greater than the mass of our sun, reside in the centers of nearby galaxies. The graphic shows the relationship between the mass of black holes and the size of the bulge of stars at the center of these galaxies. Use the graphic to answer questions 13 and 14.

Interpreting Graphics, continued 13. How does the mass of the black hole at the center of a galaxy relate to the mass of the bulge of stars that surround the black hole? F. The two masses are always equal. G The two masses are directly proportional. H. The two masses are inversely proportional. I. The two masses are unrelated to one another.

Interpreting Graphics, continued 13. How does the mass of the black hole at the center of a galaxy relate to the mass of the bulge of stars that surround the black hole? F. The two masses are always equal. G The two masses are directly proportional. H. The two masses are inversely proportional. I. The two masses are unrelated to one another.

Interpreting Graphics, continued 14. Why would a black hole be surrounded by a bulge of stars?

Interpreting Graphics, continued 14. Why would a black hole be surrounded by a bulge of stars? Answer: The gravitational pull of the black hole’s enormous mass causes stars to move toward it.