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Mr. Davis Astronomy: 2018 Final Review Page 1
I. Our View of the Universe
1. What is astrology:____The belief that the stars influence our lives_______________
2. Which model of the universe assumes that the Earth is at the center?
Geocentric:________Earth Center______________________
Heliocentric:_______Sun Center___________________________________________
3. Dead Greek Guys
Eratosthenes:_____Measured circumference________________________________________
Ptolemy:_________Geocentric model_________________________________________
Aristarchus:______Heliocentric model__________________________________________
“The sun rises in the East and sets in the West.” What is really happening? Given an answer that explains what is really moving and in what direction it moves.__________________
____Earth rotates________________________________________________________________________________________________________________________
4. What did Eratosthenes measure and how did he do it?:___He determined the angle of the sun on the same day at noon in two different places and used trigonometry to determine the circumference of the Earth____________________
5. Who developed the first Heliocentric model and why was it not accepted?_Aristarchus; no observable parallax_______________________________________________
6. Who developed the model of the solar system that was used for 1500 years?_____________
_________Ptolemy______________________________________________
7. What type of model was it – heliocentric or geocentric?___geocentric____________
8. What problem visible in the motion of the planets were epicycles designed to solve?
___Apparent backward motion of outer planets__________________________________
9. What model of the solar system did Copernicus support?___Heliocentric___________
10. Whose model was more accurate – Ptolemy’s or Copernicus’s?__Ptolemy__________
11. What weakness in Copernicus’s model kept it from being an improvement to Ptolemy’s model?__Circular orbits_______________________________________________
Mr. Davis Astronomy: 2018 Final Review Page 2
12. What did Tycho Brahe fail to detect that caused him to continue to support a geocentric model?_____Parallax________________________________________________
13. What fundamental change to the preceding models did Kepler make which allowed his models to be successful?___Elliptical orbits_________________________________________________
14. What are Kepler’s three laws?
Law 1:__Ellipses_____________________________________________________________
Law 2:__Planets sweep out equal areas in equal times_________________________
Law 3:____p^2 = a^3___________________________________________________________
15. What tool did Galileo use that made his work so productive?__Telescope__________
16. What did Galileo see that showed that “heavenly bodies” were not perfect spheres?
_________Sunspots, craters, lunar mountains_____________________________
___________________________________________________________________
17. What did Galileo see that suggested that the stars were further away than previously thought?
___Milky Way, lots of stars not visible before___________________________________
Mr. Davis Astronomy: 2018 Final Review Page 3
II. Observations
18. What is a constellation?_____Collection of stars that are viewed as a group___________
19. Are all of the stars in a constellation close to each other?__Not necessarily_________
20. What is the ecliptic?___Plane in which lies the planets, the majority of the stars in the galaxy_
21. What is the Zenith?______Straight Up_________________________
22. About how many stars can you see standing at midnight on a dark cloudless night?_~5,000____
23. What is a circumpolar star?__Goes in a circle around the pole_________________
24. What is odd about the motions of Mars, Jupiter, and Saturn?__Appear to go backwards ____
25. Why does this odd thing occur?_Earth passes them as they move in their orbits_____________
26. What are epicycles?__Apparent backwards motion___________________________
27. What did the Greeks NOT see in the night sky that allowed them to continue to hold on to a geocentric model of the solar system?__Parallax______________________________________
28. On a clear night in an open, moonless desert far from any light source, give two reasons a constellation might not be visible to you
_Wrong hemisphere, wrong season________________________________
29. What is the (presumed) most important reason for early societies to keep close track of the celestial (astronomical) calendar?__Agriculture, when to plant___________________
Mr. Davis Astronomy: 2018 Final Review Page 4
III. Physics
30. What are the three hallmarks of modern science?
______Predict___________________________________________________________________
______Testable Hypotheses_______________________________________________________
______Reformulated hypotheses based on experiment_________________________
31. What is the speed of light? (Give a numerical answer) __3E8 m/s, 186282 miles / sec_________
32. Speed of the Earth’s rotation at the equator:__1000 mph______________________
33. Speed of the Earth’s rotation at Wappinger’s Falls:__700 mph_________________
34. Speed of the Earth around the sun:_70,000 mph_____________________
35. Mars has an average orbital radius of 230,000,000km and an orbital period of 690 days. How fast is it moving in its orbit?
_____2 * PI * 230,000,000 / 690 = 2,000,000 km/day____________________________
36. (T/F) A light year is the distance light travels in 12 months. True
37. What causes the acceleration due to gravity?___mass_______________________________
38. How does the mass of an object affect its rate of fall?__No difference__Why?__All mass falls at same rate________________________________________
39. How does mass differ from weight?_Mass is due to matter, Weight due to gravity_______
40. What is inertia?__Resistance of an object to acceleration________________________
41. What are Newton’s three laws of motion?
__Inertia_____________________________________________________________________
__F = ma_____________________________________________________________________
__Every action has an equal and opposite reaction_________________________
42. What is meant by an inverse square law?__An effect whose intensity decreases with the square of the distance from the source___________________________________________
43. What things are affected by inverse square laws?_gravity, light, sound, radiation______
Mr. Davis Astronomy: 2018 Final Review Page 5
44. Forms of energy:
Kinetic energy:___Energy of motion_______________________________________
Potential Energy:__Stored energy (gravity, spring)____________________________
Radiative Energy:__Light_______________________________________________________
Thermal Energy:___Heat_______________________________________________________
Mass Energy:______E = mc^2______________________________________________________
45. Orbital Descriptions
Ellipse:___Egg-shaped________________________________________________________
Parabola:__Open passage, will not stay in orbit___________________________________
46. What is the escape velocity of an object? Going fast enough so it will never return___
47. Why are there tides?__Gravity due to the moon___________________________
48. What is the formula for the force of gravity?__Fg = G m1 m2 / r^2__________
49. If I double the mass of an object, what happens to the force of gravity it exerts?__Doubles____
50. If I double the mass of an object, what happens to the force of gravity acting on it?_Doubles__
51. If I double the distance between two objects increases, what happens to the force of gravity between them?___Divide by 4____________________________________________________
52. If I halve the distance between two objects increases, what happens to the force of gravity between them?___Multiply by 4_________________________________________
Mr. Davis Astronomy: 2018 Final Review Page 6
53. What are the colors of the spectrum of visible light? (Hint: ROYGBIV)Red, Orange Yellow Green Blue Indigo Violet
54. What other types of electromagnetic radiation is like light but just not visible to us?
1._gamma________________________2._______X-rays___________________3.____________UV______________4._______________IR_________________5._________________Radio________________
55. What are the three types of spectra?
1.__Incandescent______________________________2._____________Line Emission__________________3.________________________Line Absorption_______
Mr. Davis Astronomy: 2018 Final Review Page 7
56. What type of body emits a continuous spectrum?
_____HOT_______________________________________________________________
57. What type of body emits an emission spectrum?__glowing gas______________________
__________________________________________________________________________
58. What type of body is associated with an absorption spectrum?_backlit cloud_____
59. What two things about the blackbody radiation of an object are affected by its temperature?
___Color, Intensity_________________________________________________________
60. What is blue shifted light?__Light shifted toward the blue end of the spectrum__________
61. When is blue shifted light observed? Something coming toward us_______________
62. What is red shifted light?_ shifted toward the red end of the spectrum _____________
63. When is red shifted light observed?_Light moving away from us__________________
What can we learn from the following diagram?
Mr. Davis Astronomy: 2018 Final Review Page 8
IV. The Earth
64. What causes the seasons?___Axial tilt of the Earth___________________________
65. When is the Earth closest to the Sun?__Winter______________________________
66. Which is more important to the seasons – the distance from the sun, or some other cause?
_______________Axial Tilt__________________________________________________________ 67. The slow change in the direction of the North pole is called _precession__________ and has a
cycle of about 26,000 years.
68. The axial tilt of the Earth is about _23.5____ degrees.
69. List the phases of the moon in order starting with the new moon:
New _______
_Waxing Crescent________________
_First quarter________________
_Waxing Gibbous________________
_Full________________
_Waning Gibbous________________
_Third quarter________________
_Waning crescent________________
_New________________
70. Why do we see only one side of the moon?_The moon’s rotation matches its orbital revolution
71. During what part of the lunar cycle can lunar eclipses occur?_Full_________________________
72. During what part of the lunar cycle can solar eclipses occur?_New_________________________
Mr. Davis Astronomy: 2018 Final Review Page 9
V. Telescopes and Optics
Aperture_____E____ A. The bending of light as it goes through a medium
Refraction_A_______ B. The measure of the ability to distinguish between two different objects that are close together
Diffraction_____G_____ C. Different colors of light come to a focus at different points.
Magnification____F_____ D. Light bouncing off a surface
Reflection________D________ E. The size of the opening of the telescope where light enters
Angular resolution__B________ F. An increase in the apparent size of an object
Chromatic aberration_C_______ G. Light bending around an edge
73. The real image formed by a convex lens is
o Right-side up c. Distorted due to atmospheric aberration o Upside-down d. Reflective
The two types of optical telescope are refracting and reflecting.
74. Which type of telescope is generally preferred by astronomers today?o Reflectingo Refracting
75. What are the major differences between reflecting and refracting telescopes?Reflecting is cheaper, greater aperture, shorter. Refracting is heavier, longer, more expensive
Refracting has more chromatic aberration
76. To reduce the effects of atmospheric turbulence, a telescope should be placed where it is o High and dryo Cold and darko Damp and foggyo Hot and dry
Mr. Davis Astronomy: 2018 Final Review Page 10
77. Adaptive optics involveo Changing the size of the apertureo Increasing the size of the lenso Using fans to stir the air aroundo Changing the shape of the mirror
78. What are the major problems with refracting telescopes?o Heavy, expensive, long, chromatic aberration__________________________o _______________________________________________________________
79. To increase the amount of light a telescope can gather, it needs to be madeo Longero Larger in diametero Higher in altitudeo With an eyepiece of shorter focal length
80. What is angular resolution? Ability to separate the images of two objects that are close
together
81. To decrease the angular resolution of a telescope (smaller is better), one should
o Increase the diameter and decrease the wavelengtho Increase the diameter and increase the wavelengtho Decrease the diameter and decrease the wavelengtho Decrease the diameter and increase the wavelength
82. In the table below indicate which measurements could reasonably be taken from a ground-based
telescope.
Indicate Ground (G) where appropriate
Radio G
Infrared
Visible Light G
Ultraviolet
X-ray
Gamma-ray
83. Stars twinkleo Due to imperfections in a refracting telescopeo Due to the presence of an atmosphereo Due to the Earth’s gravitational field
Mr. Davis Astronomy: 2018 Final Review Page 11o Due to variations in the brightness of a star
84. Two telescopes are linked together to simulate a telescope with a bigger aperture. For this we use the technique called
o Angular separationo Chromatic aberrationo Refractiono Interferometry
85. What are the three types of observations made using telescopes?
o _Images_____________________________________
o _Spectrum_____________________________________
o _Brightness_____________________________________
Mr. Davis Astronomy: 2018 Final Review Page 12
86. Label the diagrams for the two telescopes below:
a. Type of telescope: Reflecting
b. Type of telescope: Refracting
Mr. Davis Astronomy: 2018 Final Review Page 13
VI. The Planets
87. The plane of the __ecliptic________________ is close to the orbits of most planets.
88. Group the nine planets (including Pluto) into two groups: Big and small. Group them in irder from largest to smallest. Label them T for terrestrial and J for Jovian.
What terrestrial “world” is not on this list?
BIG small
___Jupiter_____________________ ____Mercury_____________________
Saturn_________________________ Venus_________________________
Uranus_________________________ Earth_________________________
Neptune_________________________ Mars_________________________
_________________________ Pluto_________________________
_________________________ _(Luna)________________________
89. List the nine planets in order from the sun
__Merc____________________________________
______Vensu________________________________
___________Earth___________________________
_______________Mars_______________________
__________________Jupiter___________________
________________________Saturn_____________
_____________________________Uranus________
___________________________________Neptune__
Pluto_____________________________________
Mr. Davis Astronomy: 2018 Final Review Page 1490. Which is the archetypal Jovian planet, and which is the archetypal terrestrial planet?
o _Jupiter__________________________________________o _______Earth____________________________________
91. How does the distance between terrestrial planets compare to the distances between the Jovian planets?__Terrestrial – close together; Jovian – far apart____________________
92. The Sun: o Composition: _H/HE___________________________________________________
93. Mercury:
o What makes it unique: Close to sun
94. Venus:
o What makes it unique: Thick atmosphere, very hot
95. Earth:
o What makes it unique: Life. Lots of liquid water
96. Mars:
o What makes it unique: May once have had water
97. Jupiter:
o Composition: H/He
o What makes it unique: BIG
98. Saturn:
o Average Density: Less than Water
o What makes it unique: Rings!
o What are Saturn’s rings made of?____Ice_______________________________________
99. Uranus:
o Composition: H/He/H compounds
o What makes it unique: Rotates sideways
100. Neptune:
Mr. Davis Astronomy: 2018 Final Review Page 15o What makes it unique: Boring in appearance
101. Pluto:
o Composition: Rock and ice
o What makes it unique: Shares orbit with Neptune
102. What features of our solar system provide clues to how it was formed?
o All revolve in same way
o Most rotate the same way
o Terrestrial close to sun
o All in same plane
103. Complete the table below that compares terrestrial planets to Jovian planets.
Terrestrial Jovian
Relative Size Small Big
Relative Density High Low
Composition Rock Gas
Physical nature of surface Solid ???
Moons and Rings Few / None Lots
Relative distance from Sun Close Far
Relative surface temperature High Cold
104. What is meant by differentiation?____Separating out into different densities________
___________________________________________________________________________
105. What are asteroids and where are they found? Rocky planetesimals mostly between Mars and
Jupiter
106. What are comets and where are they found? Chunks of ice and rock, mostly past Pluto
Mr. Davis Astronomy: 2018 Final Review Page 16107. What are the exceptions to the planetary rules? Venus (backwards), Uranus (sideways)
108. What are lunar “seas” (maria)?_____Lava flows_______________________________________
109. Why do we think there was once liquid water on Mars?_river beds, deltas_________________
110. Why is it hard to observe the features of the surface of Venus?___Thick clouds____
__________________________________________________________________________
111. What is evidence of plate tectonic motion on earth?
___Earthquakes, fault lines____________________________________________________
112. How do seismic waves help us understand what the Earth is composed of?Determine velocity of sound through different layers of the Earth, how they bend__________
113. Which planets have moons?___Most, not Mercury or Venus______________________
114. What are the rotation rates of each world? (VS, S, ~Earth, F)
Mercury______VS_______________
Venus_________VS____________
Earth:_________E______________
Mars:________E_______________
Luna:________S_______________
Jupiter:_______F_______________
Saturm:_____F_________________
Uranus:_____F_________________
Neptune:_____F_________________
Pluto:_______F_______________
115. What is the effect of the fast (~10 hour) rotation of Jupiter and Saturn on the shape of the planets?______Oblate Spheroid_________________________________________
116. (Probably) Why do Jupiter, Saturn, and Neptune emit twice as much heat as they receive from the sun?______Continued gravitational contraction________________________
Mr. Davis Astronomy: 2018 Final Review Page 17117. Which planet has a mostly nitrogen / oxygen atmosphere?_____Earth___________________
118. Which planet has thick atmosphere that is mostly carbon dioxide (CO2)?__Venus___________
119. Which planet has a thin but noticeable CO2 atmosphere?____Mars_____________________
120. Which planets have Hydrogen, Helium, or Hydrogen compounds as the major portion of their atmospheres?_____Jup, Sat, Ur, Nep_______________________________________________
121. How does the greenhouse effect work?__Heat is trapped in atmosphere__________
122. What are the major greenhouse gases?_____CO2___________________________
________Methane________________________
_______________H2O_________________
123. What is the primary source of terrestrial atmospheric gases?___Volcano___________________
124. What is the primary source of the Earth’s oceans?__Volcano____________________________
125. What is albedo and why does it matter?___Reflectivity, reflects away heat___________
126. What are the major moons of Jupiter?______Ganymede_______________________________________
_Europa____________________________________________
Callisto_____________________________________________
______Io_______________________________________
Which is the biggest?________Gany__________________
Which is the most volcanically active?______Io_________________
What is the source of the internal heat for Jupiter’s moons?__Tidal interactions with Jupiter_
127. What is the major moon of Saturn?_______Titan___________________________________
128. What is significant about Saturn’s largest moon?__Atmosphere, liquid methane_____________
129. Which other of Saturn’s moons might be a place where life could exist? It is geologically active in spite of its small size. __Enceladus_________________________________________
130. What is the likely source for Jupiter’s ring?____Io’s volcanos_____________________
131. What is significant about Europa? Describe its likely construction
Mr. Davis Astronomy: 2018 Final Review Page 18
___Ice covering liquid ocean________________________________________________
VII. Nebular Hypothesis
132. What is a nebula?____Cloud of gas________________________________________
133. What are the general outlines of the nebular hypotheses for solar system formation?__________
__Cloud of gas collapsed due to gravitation, formed planets and star______________________
134. What is the hypothesis of galactic recycling?_Stars explode spewing gases and metals which are absorbed into later stars_
_______________________________________________________________________________
135. What is the difference between a “first generation” star and “second generation” or later stars?
_First generation starts with H only, later have more elements____________________________
136. What does angular momentum mean, and how does it apply to our understanding of the formation of the solar system?
___The tendency of a rotating object to keep rotating__________________________________
137. As a solar nebula collapses,
a. What happens to its temperature?______Up________________________________________
b. What happens to the spin of the nebular?_____Faster_____________________________
c. What happens to the general shape?____Pancake________________________
138. What evidence to we have from telescopic observation that supports the nebular hypothesis?
_____Have seen nebulae forming solar systems_____________________
139. What is the proposed composition of the solar nebula?_Mostly H and He___________
140. What event is believed to have transformed the solar nebula?___Ignition of Sun_____
141. Is the sun’s output (luminosity) constant?__No, slowly increases_______________
142. What is the frost line?_Water, H, He mostly driven out past the frost line_/ Solar heat________
143. What stayed within the frost line and what was forced outside it?____Rock stayed inside_________
144. What are planetesimals?____Chunks of rock and Ice that collected as nebula collapsed
Mr. Davis Astronomy: 2018 Final Review Page 19145. What would happen to planetesimals over time?___Aggregate under influence of gravity_____
146. What is the solar wind?__Nuclei and electrons streaming out from the sun___________
147. What does the period of “heavy bombardment” mean and why would it have occurred?________
__Planetesimals coalescing and colliding into a larger body until most of them were absorbed_______
148. Over time, a large enough object will become __round________________ in shape. 149. What causes planets to be hot inside?
Initially, ____leftover heat___________________ __________________ ____________ from the initial aggregation of the material into a single body.
Additional energy comes from the _kinetic energy_____________ ____________ of meteors as they strike the planet.
Most energy currently comes from __radioactive decay____________________ __________.
The interior of the planet cools by _convection__________________ of material from the core to the upper mantle, then _cunduction ___________________ of heat through the crust, and finally __radiation_________________ of energy into space.
150. Given two planets of the same composition, which cools faster – a large one or a small one?___Small________________
151. Which terrestrial worlds are now probably geologically dead?_Mercury, Luna______________
152. Which terrestrial worlds are probably still geologically active?_Earth, Venus_________________
153. Which terrestrial planet has the largest magnetic field?__Earth_____________________
154. What 3 things appear necessary for a strong magnetic field in a terrestrial planet? Moderate rotation, conductive material inside, energy source
155. What 4 things change the surface of a planet?
_Erosion_______________________________ __Vulcanism________________
_Meteors_______________________________ __Tectonics____________
156. There are more _Small_________ craters than __big____ craters.
Mr. Davis Astronomy: 2018 Final Review Page 20157. Small planets tend to have ___less atmosphere___________ _____________________ and
therefore less surface erosion.
158. The slower the _rotation______________ rate the less weather!
159. How do seismic waves help us understand what the Earth is composed of?______S and P waves travel differently through different materials._____________
160. What is the solar wind and what affect might it have on planetary atmospheres?______
___Solar wind impacting atmosphere might slowly strip it off into space____________
161. What shields Earth from the solar wind?___magnetic field_________________
162. What other planets have similar shielding?__Joviam planets__________________
163. What planet’s atmosphere argues against this shielding being important in maintaining an atmosphere?____Venus_________________________________________________
164. What is a comet made of?___Ice, dust, rocks______________________________
165. Which way does the comet’s tail point?___Away from the sun_________________
166. Comets appear to come from two general locations.
Which one is closer?__Kuiper belt_______________________________________________
Which one is in the plane of the ecliptic?__Kuiper belt_______________________________
Which one is farther away?___Oort cloud_________________________________________
Which one is a spherical halo of cometary material?_Oort cloud_______________________
167. Why do we believe the asteroids did not condense into a planet?_Jupiter’s gravity____
168. What is the life cycle of a comet?_Cold, warm (loses material), cold, warm, cold, eventually runs out of stuff and meteor shower is left___________
169. What are the characteristics of a planet and which does Pluto lack?
_Spherical, cleared orbit of other stuff, orbits star__________________________________________
_Pluto has not cleared orbit__________________________________________
170. How can we detect extrasolar planets?
Mr. Davis Astronomy: 2018 Final Review Page 21
1 ) _Doppler effect_ __ __ __ __ __ __ __ __ __ __ __ __ 2) __Transit __ __ __ __ __ __
3) Direct observation__ __ __ __ __ __ __ __ __ __ __ __ __
171. What types of extrasolar planets have been discovered?
__Terrestrial_____________________________________________
__Hot Jupiters_____________________________________________
172. How do the orbits of most planets discovered thus far compare to the orbits in our solar system?___Highly eccentric_________________________________________
Mr. Davis Astronomy: 2018 Final Review Page 22
VIII. Review – The Sun
173. Label the layers of the Sun in the figure below. Fill in each box with the appropriate label
and approximate temperature.
174. The layer of the Sun we see is called the Photosphere .
175. The Sun produces its energy through fusion by converting four atoms of
Hydrogen into one atom of Helium
Chromosphere 10,000-100,000K
Radiation zone 10,000,000K
Corona 1,000,000K
Convection Zone
Photosphere 6,000K
Core 15,000,000K
Mr. Davis Astronomy: 2018 Final Review Page 23
. In order for this process to occur, there must be very high pressure
and temperature in the core.
.
176. Nuclear power plants produce energy through a process called fission .
177. Scientists expect our Sun to last for another 5,000,000,000 years.
178. Define solar flare. An ejection of material (plasma) from the surface of the sun after a
recombination of magnetic field lines
179. Define solar prominence. Solar plasma rising from the surface of the sun and returning
to the surface following magnetic field lines.
180. What’s a sunspot? A cooler region on the sun’s surface (where magnetic field lines leave
the surface)
181. Solar prominences are often associated with sunspots.
182. The sunspot cycle lasts about 11 years.
183. Solar flares have been known to disrupt
electrical power distribution and damage satellites.
184. What two processes, working together, keep the sun in balance?
Process 1:_______Gravity___________________________________________________________
Process 2:_______Fusion___________________________________________________________
185. Where does fusion occur?__Core____________________________
186. Through what layer do gamma ray photons travel by diffusion?_radiation zone_____________
187. Through what layer does energy convect toward the surface?__convection zone_____________
188. What is the layer that produces most of the ultraviolet radiation?_Chromosphere___________
189. What is the layer we see in an eclipse?____Corona__________________________
190. What is the outer layer of the sun’s atmosphere which extends far out into space?________
____Solar wind_____________________________________________________________________
Mr. Davis Astronomy: 2018 Final Review Page 24
191. What is stellar luminosity?_The inherent brightness of a star______________________
192. What is the difference between apparent luminosity and actual luminosity?__Apparent luminosity is how bright it looks from here. Actual luminosity si how bright it looks from
a standard distance._________________________
193. What do the colors of stars tell us about their temperature?__More blue = hotter, red = cooler – black body radiation_
194. List the spectral types from hottest to coldest:__OBAFGKM_____________________________
195. How do we measure stellar masses?__Period of a binary system___________________
196. What is a Hertzsprung-Russell diagram?__A diagram showing stellar temperatures and luminosities_________
197. What is the Main Sequence?____hydrogen burning stars___________________________
198. What are giants and supergiants?__Helium burning stars that have left the main sequence____
199. What is the difference between main sequence stars and Giants / Supergiants in terms of the fuel consumed?___Hydrogen vs. Helium_________________________________
200. What are white dwarfs?_Stars that have burned up fule, shrunk down, and are now just cooling_____
201. Which stars have the shortest lifetimes?_Large blue_________________________
202. Which stars have the longest lifetimes?__Red dwarf___________________________
203. What is the relationship between luminosity and lifetime?_more luminous – shorter life_____
204. What is a Cepheid variable? A variable star running on a branch of the main sequence_______
Mr. Davis Astronomy: 2018 Final Review Page 25
IX. The End
205. When a large cloud of gas in a galaxy ejected from a supernova runs into a large cloud of gas ejected from another supernova, what may occur?
______Star formation________________________________________________
206. Why do astronomers look at light at different frequencies (wavelengths)?_____Different features visible at different wavelengths___________________________
207. What is probably at the center of most galaxies?__Black Hole_______________
208. What do astronomers measure that causes them to think that the universe is accelerating?___red shift____________________________________________
209. What is Hubble’s Law?_Further away – moving faster away___________________
210. What would be needed to keep the universe from accelerating?__More mass_
211. What does the acceleration of the universe tell us about its origin?_It started out as a compact object_______
212. What is “dark matter”?__Material producing gravity we cannot otherwise see or detect._
213. What is “dark energy”?__Something causing the universe to accelerate its expansion_____
214. What proportion of the universe appears to be made of “normal” matter?__5%___________
215. What is a WIMP?__Proposed dark matter particle (Weakly interacting massive particle)_____
216. What do we mean when we say that the universe is expanding?o Average distances are increasing between galaxies?o The statement is not meant to be literal; rather, it means that our knowledge of the
universe is growing?
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