Lectures 16-30 Flashcards
(168 cards)
1
Q
Formula for apparent brightness
A
b=L/(4πd2)
2
Q
Units for brightness
A
Watts/m2
3
Q
If two stars have the same luminosity but one appears 100 times dimmer, how much further away is it?
A
10x
4
Q
The sun is ___ times fainter at Pluto than here on Earth
A
900
5
Q
Apparent brightness depends on
A
(1) the intrinsic brightness of an object
and
(2) distance
6
Q
How do spacecraft like Galileo, Voyager, Cassini, and New Horizons differ from satellites orbiting Earth?
A
They rely on nuclear power instead of solar panels
7
Q
Luminosity is measured in
A
Watts (J/s)
8
Q
Brightness is an ___ property
A
observed
9
Q
Typical size of an atom
A
1 Angstrom
or
10-10 m
10
Q
Size, chemical reactions, and spectra of atoms are all determined by the
A
electrons
11
Q
A proton has a diameter of about 10-18 m. A hydrogen atom has a diameter of 10-10 m. If a proton were soft-ball size (10-1 m), how big would a hydrogen atom be in meters?
A
107
12
Q
A proton has ___ unit of positive electric charge
A
1
13
Q
A neutron has __ units of electric charge
A
0
14
Q
Electrons have ___ units of negative electric charge
A
1
15
Q
If an atom is missing one or more electrons, it is called an ___
A
ion
16
Q
Elements are defined by the number of ___ in their nucleus
A
protons
17
Q
Isotopes are the same elements with different numbers of ___
A
neutrons
18
Q
The mass number is ____ + ____
A
protons + neutrons
19
Q
Atomic number = # of ____
A
protons
20
Q
Some isotopes are not stable. This means they will
A
Spontaneously decay
21
Q
An isotope that spontaneously decays is called
A
radioactive
22
Q
An alpha particle is
A
an He nucleus
23
Q
a beta particle is
A
an electron
24
Q
a gamma particle is
A
a high-energy photon
25
carbon dating is a method of age determination that depends on the decay of C14 into
nitrogen
26
A half life is
the time it take for one-half of the parent isotope to decay to a daughter isotope
27
What properties does a photon have?
Energy, frequency, speed
28
Energy is produced when one end of the thermocouple is ____ than the other
hotter
29
A ______ powers outer solar system spacecraft
Radioisotope thermoelectric generator (RTG)
30
Moving electrons=
electric current
31
Equation for nuclear power
E=mc2
32
In the Sun, protons (hydrogen nuclei) are combined to form
a helium nucleus
33
Fusing hydrogen into helium releases energy. What can we conclude?
A heluim nucleus is less massive than 4 hydrogen nuclei
34
In practice, we can tap into E=mc2 energy via
nuclear fission and nuclear fusion
35
Nuclear fission is when
a massive nucleus is split into smaller nuclei
36
Nuclear fusion is when
light atomic nuclei are fused into a more massive nucleus
37
Nuclear power plants operate by
heating water to steam which moves a turbine
38
for a sustained fission reaction, you need additional
neutrons
39
a nuclear meltdown is when
the reaction is uncontrolled
40
in a nuclear bomb, ____ is the goal
rapid fissionn chain-reaction
41
To create a nuclear reactor or weapon, you must ___ the uranium
enrich
42
Enriching uranium is done in
centrifuges
43
in modern reactors, ___ is also used as ffuel
plutonium
44
What were the two Mars rovers launched in 2003?
Spirit and Opportunity
45
This launched in 2011 and transported the Mars Curiosity rover
Mars Science Laboratory
46
Cost of trip to Mars is about ___ dollars per person
$10 billion
47
How does SpaceX plan to reduce the cost to go to Mars?
Full Reusability
Refilling in orbit
Propellant production on Mars
Right propellant
48
Challenges travelling to Mars include
Cost
Exposure to radiation
prolonged exposure to weightlessness
psychological effects
49
The hoffmann transferorbit uses an elliptical orbit to ___ and requires \_\_\_
transfer from one circular orbit to another
two thrusts to reach Mars' orbit, taking ~250 days
50
NASA program to study effeccts of possible habitat on astronauts
HI-SEAS
51
What was Mars one?
Martian colonization as a vventure capital effort: raised tens of millions of dollars, but bankrupt in 2019. Original plan was to fund via reality tv.
52
What was the inspiration Mars foundation?
goal to send two people to fly by Mars
500 day loop around Mars
revealed in congress expected cost sharing with NASA and SpaceX-lead to downfall
53
Name 2 missions that studied the Sun
SOHO and Trace
54
Define solar prominances
huge flows of plasma (5000-10,000 K)supported by magnetic fields
55
Solar flares are
powerful energetic eruptions powered by the release of magnetic energy with temps up to 20 million K
56
What are coronal mass ejections?
Flows of hot gas blown outward at speeds up to 1500 km/s
57
What are the Van Allen Belts?
Van Allen belts arise due to charge particles being
trapped by the Earth’s magnetic field.
58
If solar wind particles move along magnetic field lines,
where should I go to see the aurorae?
To the poles
59
What causes the borealis?
the interaction of electrons in solar wind with atoms in
Earth’s atmosphere (particularly, oxygen and nitrogen)
60
Location of the borealis is set by
the orientation of Earth’s magnetic field (near N and S celestial poles).
61
NASA’s Orion Mission was
First mission (with a spacecraft capable of carrying people) to leave low
Earth orbit in 40+ years.
62
NASA's Orion mission passed through ____ and completed ___ orbits
the Van Allen Belts
2
63
Chandra X-ray Observatory was the heaviest payloadnever (50k lbs) due to
rocket booster system
64
Chandra X-ray Observatory was put into an _____ orbit
elliptical
65
Who wouldn’t want a 500-day space cruise?
Sources of Radiation:
Earth’s radiation belts
Solar radiation (wind and flares)
Galactic cosmic radiation
66
Why should you worry about radiation on Mars?
Because Mars lacks a magnetic field and has a thin atmosphere (both of which help
protect us here on Earth).
67
How do planets form?
Gas and dust in protoplanetary disks grow from smaller to larger bodies.
68
Total mass of main asteroid belt is
smaller than
mass of Moon
69
Asteroids are ____ and most are less than ___ km in diameter
small rocky bodies that orbit the sun
10 km
70
Most asteroids orbit the sun between
Mars and Jupiter
71
The largest asteroid is
Ceres, about 950 km in diameter
72
Dawn: NASA mission launched in 2007 to study ____ and was the first spacecraft to
Vesta and Ceres
orbit two different extraterrestrial
bodies, and first to orbit a dwarf planet.
73
Late Heavy Bombardment was a period of
intense comet & asteroid bombardment in the solar system.
74
Evidence of the late heavy bombardment comes from
craters on the Moon,
asteroids, terrestrial planets, etc.
75
Carbon from the meteorites may have reacted
with Earth’s nitrogen to form
hydrogen cyanide
76
The last sterilizing impacts occurred during the
Hadean Eon 4.3 – 3.8 Gya
77
Which equation describes the energy imparted in a meteor impact?
E = 1⁄2 mv2
78
Why would a comet’s orbital velocity
at 1AU be different from Earth’s?
Orbital velocity set by mass of sun and distance from it
79
what does change the orbital velocity?
The orbital eccentricity
80
Most comets come from
the Kuiper Belt
81
12 November 2014, the
ESA’s Rosetta mission w
lander “Philae” performed
the first soft landing on a
comet and returned data
from the surface
82
City Buster:
\_\_\_ m Meteroid.
Expect every ___ yrs
~\_\_\_\_ Megaton (MT) of TNT
30
50
1
83
People Buster:
\_\_\_ km Asteroid.
Every ____ yrs
~\_\_\_\_ MT TNT
- Hemispheric-scale/Global effects.
- Significant fraction of all humans killed.
1 km
100,000 yrs
100,000 MT
84
Planet Buster:
\_\_\_ km Asteroid.
Every ___ yrs
~\_\_\_\_\_ MT TNT
- Global effects, major extinctions of lifeforms
- Global winter, likely all humans extinct
10 km
100 Million
100 Million
85
NEOWISE is
Asteroid hunting mission between NASA and USAF
86
What are NEOs?
Near Earth Objects
Asteroids and comets that have orbits bringing them close to Earth
87
which equation did we use to describe the energy
required to overcome Earth’s gravity with a rocket?
E = Fd
88
If E=Fd, what can we conclude
about light?
It is capable of exerting a force.
89
Explain Radiation Pressure
Photons carry energy, and therefore exert a pressure, or
force, when they hit something.
90
Force of Radiation Pressure Equation
F=LR2/4d2c
91
Light exerts twice as much force if it is absorbed or reflected?
reflected
92
So what’s the best way to deflect a deadly
asteroid/comet using radiation pressure?
Paint it white
93
Gravity tractor:
use thrusters to keep a
spacecraft at fixed distance & direction
from an asteroid. The craft’s gravity will
slowly pull the asteroid off course.
94
Open-pit mining: environmental impacts
•Mining: Disrupts local ecosystems, releases radioactive
waste products.
• Refining: Releases heavy metals & other poisons into the
air, water, and ground.
• Disposal: Chemicals produced in mining & refining
contaminate water sources.
95
Types of Asteroids
C-type:
carbonaceous [low albedo]
| (~75% of known asteroids)
96
Types of Asteroids
S-type:
silicaceous [stony]
| (~20% of known asteroids)
97
Types of Asteroids
M-type:
metallic
| (~5% of known asteroids)
98
Ordinary Chondrite:
an agglomeration of dust and mineral grains
including chondrules
99
Carbonaceous Chondrite:
a chondrite with a high carbon content,
including complex organic molecules
100
Achondrite:
a stony meteorite that was once part of a larger
body that experienced melting and differentiation
101
Iron meteorites origin
the cores of asteroids that were large
enough to undergo differentiation
102
Why is there so much more metal in asteroids than Earth’s crust?
Earth’s metals are too deep for us to mine.
103
there are all sorts of spy satellites, whose purposes include
missile early warning, nuclear explosion
detection, imaging, electronic reconnaissance,
104
Gamma Ray Burst (GRB):
A massive star collapses into a
black hole, releasing a stream of particles along a jet.
105
Vela A and B satellites were designed to detect
explosions from nuclear bombs
106
define astronomical “seeing”
The smallest angular size that can be resolved
107
angular resolution of a camera in degrees is
57.3s/h
where s is scale can resolve and h is altitude
108
The Rayleigh Criterion
The physical limit (ignoring atmosphere) for a telescope’s imaging resolution is
set by the size of the telescope and the wavelength of light observed.
109
The Rayleigh Criterion Equation
Alpha=70Lambda/D
110
What combination will give us the best
resolution?
A. A big telescope and blue light
B. A big telescope and red light
C. A small telescope and blue light
D. A small telescope and red light
A big telescope and blue light
111
How to determine limiting image resolution
Is there an atmosphere in the way? → Limiting resolution = seeing
Otherwise? → Limiting resolution = Rayleigh criterion
112
Through use of various techniques such as speckle imaging, spy satellites are able to achieve spatial resolutions of
~4 inches.
113
Electromagnetic Pulse (EMP): A
nuclear detonation releases\_\_\_\_\_\_\_, which dislodge electrons from
the atmosphere.
These free electrons get caught in
Earth’s magnetic field, releasing
\_\_\_\_\_\_\_\_.
gamma rays
electromagnetic waves
114
Strategic Defense Initiative (SDI):
Founded by President Reagan in 1983. Derisively
dubbed “Star Wars” by Ted Kennedy.
115
Strategic Defense Initiative sought to develop
ICBM intercept systems
116
SDI Strategies
• Missiles and/or lasers fired from the ground to destroy ICBMs
• Brilliant Pebbles: missile interceptors held in geostationary orbit over
the Soviet Union.
117
Black Hole working def
an object so dense that its escape velocity exceeds the speed of light
118
from a general relativistic point of view, the ____ \_\_\_\_ around a black hole becomes \_\_\_\_
spacetime curvature
infinite
119
The ____ \_\_\_\_ is the distance to the object at which the escape velocity equals the speed of light
event horizon
120
black holes can have these properties:
Mass
Radius
Spin
Electric Charge
121
Which parameters determine escape velocity?
Mass of the object were escaping
Radius of object were escaping
122
Radius scales linearly with mass. The equation is:
RBH= (3 km)(MBH/MSUN)
123
What is a stellar mass black hole
When the core of a massive star collapses to form a black hole
124
Two ways to make a black hole:
1. Star collapse
2. Large amounts of mass settle in the middle of galaxies (supermassive black holes)
125
The supermassive black hole at the center of the milky way
Sagitarius A
126
Elements of a black hole
event horizon
accretion disc
relativistic jets
127
The two feasible targets for taking a picture of a supermassive black hole
Sagitarius A and M87
128
Which would offer a better resolution?
A solid 5 meter mirror
A 10 meter mirror with a 5 meter hole in the middle
A 10 meter mirror with a hole in the center
129
Interferometry combines
signals from multiple telescopes
130
LISA- European space-based Gwave detector- will
probe gravitational waves at frequencies not accessible to LIGO
131
True or False: an oxidizer has to be oxygen
False
132
How to rocket engines differ from jet engines
Rockets have all fuel on board
133
The space shuttle solid rocket boosters were most powerful rocket engines ever flown; provided about \_\_\_\_% of space shuttle thrust to reach orbit and accounted for about ____ % of launch mass
80%
50%
134
ion drive
Propulsion generated by accelerating ions throguh a magnetic or electric field
135
Pros and cons of solar sailing:
Pros:
No fuel, continuous propulsion
Cons:
modest acceleration, radiation pressure weakens with diistance
136
\_\_\_\_ have been proposed as an alternative to redirecting asteroids
Solar Sails
137
Electric/magnetic sail
charged particles from solar wind bounce off sheet-like electric field
138
The interstellar medium is made up of mostly ____ gas
hydrogen
139
Ramscoop/ Bussard Ramjet:
giant electromagnetic field collects hydrogen from around the spacecraft
140
Explain the difference between fusion and fission
Fusion creates energy by combining atoms, fission creates it by splitting atoms
141
A staged thermonuclear device uses
a small fission device to start a fusion reaction
142
fission bombs release energy equivalent to ____ of tnt whereas fusion bombs (h-bombs) release ____ tnt
tens of kilotons
tens of megatons
143
Project Orion was
nuclear pulse propulsion project
144
how would nuclear pulse propulsion work for space travel?
Explosions propel mass away from ship
145
What were some potential hazards of nuclear pulse propulsion?
potentially lethal g forces
radiation exposure
explosions could blind bystanders for hundreds of miles
nuclear fallout
146
Which is true of our ability to deflect asteroids?
1. our bombs arent powerful enough
2. radiation pressure is untested
3. we cannot accurately target
4. our rockets cannot reach most NEOs
4. our rockets cannot reach most NEOs
147
Breakthrough Listen is mainly focused on
surveying stars and examining interesting objects
148
Breakthrough Message involves
understanding how intelligent civilizations might encode a message
149
Two early attempts at sending messages into space
Arecibo message (1974)
Pioneer 10 (1972)
150
What is starshot?
A mission to send a light sail at ~20% the speed of light to another star system
151
The mission concept that preceeded Starshot
Starwisp
152
Why hasnt Starshot been done yet?
Need to improve laser tech
Need to shrink science payload
Need better energy storage
Challenge of constructing nanocraft
Better adaptive optics
Collisions with interstellar dust
153
The starshot electronics board will include
1. multiple detectors
2. lasers (thrust and comms)
3. power storage
4. ability to point (beam info back to Earth)
154
Starshot spacecraft will use the ___ as the antenna
Light sail
155
The habitable zone is
a region around a star where a planet could have liquid water
156
The habitable zone of a star is set by
type of star (how bright) and orbit of planet
157
Explain the Science of Starshot:
1. on the way: \_\_\_\_
2. Almost there: \_\_\_\_
3. Closest approach: \_\_\_\_
1. Study interstellar medium
2. Study Proxima and planets
3. Take high resolution photos and measurements
158
The Drake equation is
An organizational tool to make an educated guess on how many technological, communicating civilizations in the galaxy
159
Approximately how many stars are in the Milky Way galaxy?
Tens of billions
160
According to the Drakes equation, approximately how many intelligent communicating civilizations are there?
45
161
How long would it take to travel to Próxima Centauri with current tech?
Tens of thousands of years
162
Which are true, A. Proxima is a binary B. Proxima orbits the center of the galaxy C. The sun orbits the center of the galaxy
All of the above
163
Glides 710 (m dwarf star) will
Be within the Oort Cloud in 1.4 million years
164
The Fermi paradox
We should have been visited by aliens by now but haven’t
165
What is the great filter
An evolutionary barrier that prevents most civilizations from becoming technological and space fairing
166
Seti- search for extraterrestrial intelligence- detects life by
Looking for powerful signals, probes, or visitors. Perhaps prime numbers.
167
Two ways to find ETI
Technosignatures (evidence of alien tech without intentional comms) Communication ( electromagnetic signals)
168
Exoplanet mapping
Mapping surface by measuring light that reflects off it
