Module 16 Flashcards
1a. Define: nuclear fusion
the process by which two or more small nuclei fuse to make a bigger nucleus
1b. Define: nuclear fission
the process by which a large nucleus is split into smaller nuclei
1c. Define: critical mass
the amount of isotope necessary to sustain a chain reaction
1d. Define: absolute magnitude
The brightness of a star, corrected for distance, on a scale of -8 to +19. The smaller the number, the brighter the star.
1e. Define: apparent magnitude
The brightness of a star as seen in the night sky. The smaller the number the brighter the star.
1f. Define: light year
the distance light could travel along a straight line in one year
1g. Define: galaxy
a large ensemble of stars, all interacting through the gravitational force and orbiting around a common center
- From the inside to the outside, name the four regions of the sun.
the core, the radiative zone, the convection zone, and the photosphere
- How does the sun get its power? In which region of the sun does this process occur?
the sun gets its power from nuclear fusion that occurs in the core
- What part of the sun do we see?
the photosphere
- A (251Cf) nucleus is bombarded with a neutron. It breaks down into a (124 Sn) nucleus, a (120Cd) nucleus and seven neutrons. Is this nuclear fission or nuclear fusion?
nuclear fission
- Two (4He nuclei collide and turn into a (7Be) nucleus and one neutron. Is this nuclear fusion or nuclear fission?
nuclear fusion
- For both the nuclear fusion that occurs in the sun and the nuclear fission that occurs in a nuclear power plant, what can we say about the mass of the starting materials compared to the mass of what’s made in the end?
the mass of the starting materials is larger than the mass of the materials the process makes
- Why is it impossible for a nuclear power plant to have a nuclear explosion?
a power plant does not have significantly more than the critical mass of the large nucleus that is breaking apart
- Why is nuclear fusion considered a better option for energy production than nuclear fission?
Nuclear fusion is a better means of producing energy because there are no radioactive byproducts, there is no chance of meltdown, and the starting materials are cheap.
- If nuclear fusion is a better option, why don’t we use it?
We cannot use nuclear fusion yet because we cannot master the technology to make it economically feasible.
- look in book on page 421, #11
a- Red Giant b-Main Sequence c- Supergiant d-White Dwarf
- look in book on page 422, #12
star (b) is most like our sun
- look in book on page 422, #13
(d), (b), (a) and (c)
- look in book on page 422, #14
(d), (b), (a), and (c)
- look in book on page 422, #15
(a) is the coolest
- What similarity exists between novas, supernovas and pulsating variables?
all three of these are variable star types; thus, their brightness changes radically with time
- What is the big difference between novas, supernovas, and pulsating variables?
The big difference between these star types is lifetime. Pulsating stars last a long time, supernovas exist very briefly, and novas are somewhere in between.
- What most likely formed the crab nebula?
most likely formed by a supernova
- What are the two methods for measuring the distance from earth to a star? Which of the two is most accurate? Which can be used to measure long distances?
The two methods are the parallax method andf the apparent magnitude method. The parallax method is exact, but the apparent magnitude method can be used to measure longer distances.
- Why are Cepheid variables so important for measuring long distances in the universe?
Cepheid variables are important for measuring long distances because they seem to have a relationship between their period and their magnitude. That allows them to be used in hte apparent magnitude method for measuring long distances in the universe.
- What are the four basic types of galaxies? To which type does the Milky Way belong?
spiral, lenticular, elliptical, and irregular; the Milky Way is a spiral galaxy
- Fill in the blanks: stars group together to form—, which group together to form—-, which group together to form—-, some of which group together to form——–.
galaxies…groups…clusters… superclusters
- For the first three answers you gave in #22, give the names that apply to those in which earth’s solar system belongs.
Milky Way….Local Group…Virgo Cluster
- Why do most astronomers believe that universe is expanding?
Most astronomers believe that the universe is expanding because the light from nearly every galaxy experiences a red shift before it reaches the earth, and the red shift increases the farther the galaxy is from the earth.
- If the universe is expanding, does the geometry of the expansion matter? If so, why?
Yes, the geometry of the universla expansion makes a great deal of difference. The theories that can be developed for the fromation of the universe depend on that initial assumption.
