Answer Key_
Name: _
Pretest Score: _____/ 59
Posttest Score: _____/ 59
Ch 20.1 & 20.2: Stars and Galaxies
O__ the name of our galaxy
1. __
I
2. __ __ when a star is in “balance” and will not
A. absolute magnitude
B. apparent magnitude
C. black hole
change; energy pushing out = gravity
pulling in
D. cluster
E. convective zone
and explodes
F. corona
G. elliptical galaxy
Y__ when a massive star collapses in on itself
3. __
D__ a group of galaxies, ours is called
4. __
The Local Group
E__ the 2nd layer outside the core of a star
5. __
where hot plasma moves up and down
bringing energy to the surface
A__ one measure of the brightness of a star,
6. __
H. galaxy
I. hydrostatic equilibrium
J. HR Diagram
K. irregular galaxy
L. light year
M. luminosity
assuming they are all the same
distance, negative numbers are brighter
N. main sequence
O. Milky Way
shapes/types
P. nebula
Q. photosphere
H__ a collection of thousands of stars, 3 main
7. __
P__ a cloud of gas/dust by which many stars
8. __
R. protostar
begin and end their lives
S. quasar
we see are this type
T. radiative zone
U. red dwarf
N__ an area on the HR Diagram, 90% of stars
9. __
L__ the distance light travels in one year,
10. __
9.5 trillion m
V__ very large, but colder and dimmer stars
11. __
C__ the ultimate ending for a massive star, so
12. __
V. red giant
W. spiral galaxy
X. stellar spectrum
Y. supernova
Z. white dwarf
dense not even light escapes its gravity
J__ chart used to classify stars by temperature and brightness
13. __
K__ an older galaxy with no definite shape, may have old or new stars, lots of
14. __
interstellar matter or a little
T__ area inside a star, right outside of the core where energy begins to move
15. __
towards the surface
S__ a very young galaxy that is also very bright and very far away
16. __
U__ a small, cool star much less massive than our Sun
17. __
R__ an “infant” star, hard to see because they are still in their nebula
18. __
G__ a galaxy that is round or oval, has mostly old stars and little interstellar
19. __
matter
X__ the specific wavelengths of light given off/absorbed by a star. Looks like a
20. __
rainbow
F__ outermost layer of Sun’s atmosphere, extends far into space
21. __
B__ how bright or dim a star looks, can be affected by temperature, size of star
22. __
or distance from earth
Z__ a small, very hot star. Our Sun will eventually become one
23. __
M__ a measure of the brightness of a star by measuring the actual energy
24. __
output, uses factors of 10 (102, 104, 106)
Q__ visible surface of the Sun
25. __
W__ a galaxy with “arms”, has a mix of old and new stars with interstellar
26. __
matter
Label this picture of the layers of the Sun and its atmosphere:
28. Chromosphere
27. Photosphere
29. Corona
30. Convective zone
31. Radiative zone
32. Core
Stars, like the Sun, stay the same size for long periods of time because of something
called hydrostatic equilibrium.
33. Describe what hydrostatic equilibrium is.
Balance between two forces, star does not
change size/temperature
34. – 35. Describe the two forces at work to maintain hydrostatic equilibrium.
Force of energy pushing out
Force of gravity pulling in
36. – 37. What is a star’s spectrum and what info can we gain form it?
Wavelengths of light given off (or absorbed),
tells us what it’s made of, how far away it is,
how fast it’s moving, how fast it’s spinning
38. How is a star’s temperature related to its color?
Color indicates temperature, they match
red = ~ 3,000 K
orange = ~5,000 K
yellow - ~6,000 K
white = ~ 10,000 K
blue = ~15,000+ K
39. – 41. What three things determine the brightness (apparent magnitude) of a star?
Explain how they do this.
Temperature: hotter = brighter
Diameter: bigger = brighter
Distance from earth: Closer = brighter
Below is an H-R diagram. It is used to classify stars. Label the diagram with the type
of star
42. Blue
supergiants
Main
Sequence
43. Red
Supergiants
46.
44. Red Giants
45. White dwarfs
47. – 48. What two things are measured/used to classify stars?
Temperature (usually in K)
Brightness (absolute magnitude or luminosity.
Abs. mag. is how bright if same distance from
Earth…lower number = brighter.
Lum. is compared to Sun and goes by factors of 10)
Use the HR Diagram to classify these stars and answer these questions:
White dwarf_ Sirius A: temp of 15,000 K and luminosity of 10-2
49. _
Red Giant_ Mira: temp of 3,000 K and luminosity of 102
50. _
10,000 – 20,000 K_ Van Maanan’s star is a white dwarf and has a
51. _
luminosity of 10-4. What could be its temperature?
1_________ Eridani is a yellow main sequence star. Its temperature
52. ________
is 5,000 K, what could be its luminosity?
53. Stars change over their lifetimes. What property of matter will decide which
pathway a star takes? Describe how.
Mass…more mass = more likely to be a
bigger/hotter star
Put the following phrases in order to show this.
54. For a star like our Sun….
A. after the star’s core uses up its supply of helium, it contracts even more and the
outer layers start to escape into space (called planetary nebula)
B. heat from Hydrogen undergoing fusion causes an outward force that balances the
contracting force of gravity. (Main Sequence star)
C. when the temperature inside the nebula reaches 10,000,000 K fusion begins and
A protostar forms.
D. when the hydrogen in the core is exhausted there is no longer a balance. The star
expands and cools. Now there is fusion of helium to form heavier elements (red
giant)
E. the core contracts under the force of gravity into a small, hot star (white dwarf)
F. there is a large, swirling cloud of gas and dust (nebula)
G. the star runs out of fuel and ends its life as a small, cold dark ball of carbon (black
dwarf)
F__-->__C__-->__B__-->__D__-->__A__-->__E__-->__G__
__
55. For a star much more massive than our Sun….
A. if the core that is left is still 3x the mass of the Sun, it will collapse again
(black hole)
B. there is a large, swirling cloud of gas and dust (nebula)
C. stars 10x the mass of our Sun or more evolve more quickly. The core heats up to
higher temperatures and elements up to iron form (blue giant)
D. the collapsed core shrinks to about 10-15 km, protons and electrons are combined
and only neutrons exist (neutron star)
E. As the star runs out of fuel, it gets even bigger, but colder (red supergiant)
F. eventually iron forms and fusion can no longer occur. The core collapses violently,
sending out a shockwave. The outer portion of the star explodes. (supernova)
G. when the temperature inside the nebula reaches 10,000,000 K fusion begins and
A protostar forms
B__-->__G__-->__C__-->__E__-->__F__-->__D__-->__A__
__
56. What is a galaxy? What’s ours called?
Collection of millions of stars
Ours is called the Milky way
57. – 59. There are three types of galaxies. Name/draw them.
Spiral (and barred spiral)
Elliptical
Irregular