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Astronomy > Midterm > Flashcards

Midterm Flashcards

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1
Q

Astronomical Unit

A

The average distance between the Earth and the Sun
(1.5 x 10^8 km)

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2
Q

Parsec

A

The typical distance between stars as defined by the angular wobble caused by Earth’s orbit
(3.1 x 10^13 km)

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3
Q

Light-year

A

The distance light can travel in one year
(9.5 x 10^12 km)

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4
Q

Let’s reduce the size of the solar system by a factor of
10 billion; the Sun is now the size of a large grapefruit
(14 cm diameter)
How big is Earth on this scale?

A

A ball point
(100x smaller than the Sun)

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5
Q

Light travels at a finite speed of…

A

300,000 km/s

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6
Q

Speed

A

Rate at which object moves
speed= distance/time
(units of m/s)

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7
Q

Velocity

A

Speed and direction

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8
Q

Acceleration

A

Change in velocity
Units of speed/time
(m/s^2)

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9
Q

What is the acceleration of gravity on Earth?

A

10 m/s^2

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10
Q

Galileo showed that g is the (same/different) for all falling objects, regardless of their mass

A

same

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11
Q

Momentum

A

mass x velocity

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12
Q

What changes momentum, causing acceleration?

A

a net force

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13
Q

Angular momentum

A

The rotational momentum of a spinning or orbiting object
mass x velocity x distance from axis

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14
Q

Mass

A

the amount of matter in an object

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15
Q

Weight

A

the force that acts upon an object; depends on the acceleration of gravity

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16
Q

Newton’s 1st Law of Motion

A

An object moves at a constant velocity unless a net force acts to change its speed or direction

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17
Q

Newton’s 2nd Law of Motion

A

Force= mass x acceleration

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18
Q

Newton’s 3rd Law of Motion

A

For every force, their is always an equal and opposite reaction force

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19
Q

Kinetic energy

A

The energy of motion
= 1/2 m v^2

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20
Q

Radiative energy

A

The energy of light

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21
Q

Potential energy

A

Stored energy

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22
Q

Thermal energy

A

A measure of the total kinetic energy of all the particles in a substance
Depends on temperature & density

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23
Q

Temperature (energy)

A

Measures average kinetic energy of the many particles in a substance

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24
Q

The Universal Law of Gravitation

A
  1. Every mass attracts every other mass.
  2. Attraction is directly proportional to the product of their masses.
  3. Attraction is inversely proportional to the square of the distance between their centers
    Fg= G (M1M2/d^2)
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25
Newton's Version of Kepler's 3rd Law
(M1+M2)p^2=a^3 p= orbital period (yrs) a= AU M1+M2= sum of masses (solar masses)
26
Atomic Number
The number of protons in nucleus
27
Atomic Mass Number
The # of protons + neutrons
28
Molecules
Consists of 2 or more atoms (H20, CO2)
29
Quantum Theory
Electrons in atoms are restricted to particular energy levels
30
In energy level transitions, what does jumping up or down cause?
Jump up= can occur by the absorption of a photon Jump down= can lead to the emission of a photon of light
31
Wavelength
the distance between 2 wave peaks
32
Frequency
the number of times per second that a wave vibrates up and down
33
The Electromagnetic Spectrum
Gamma rays S WL/ H F X-rays UV Visible Infrared Microwave Radio L WL/ S F
34
Continuous Spectrum
contains all wavelengths of light in a certain range
35
Emission Line Spectrum
the source emits specific wavelengths of radiation
36
Absorption Line Spectrum
dark lines or gaps in the spectrum corresponding to wavelengths that are absorbed by the gas
37
The Doppler Shift
Tells us only about the part of an object's motion toward or away from us Approaching us- smaller wavelength Moving away from us- longer wavelength
38
Hydrostatic Equilibrium
Inward gravitational force= outward pressure changes
39
What does pressure depend on?
temperature and density
40
Core
Hot enough for nuclear fusion
41
Layers of the sun
Core Radiation zone Convection zone Photosphere Chromosphere Corona Solar Wind
42
Proton-Proton Chain
The Sun releases energy by fusing 4 hydrogen nuclei into 1 helium nucleus
43
What stays in the core and what is released as gamma rays?
Helium stays in the core Energy is released as gamma rays
44
Radiation zone
Hotter and is relatively transparent (energy flow by light)
45
Convection zone
Cooler and is more opaque (energy flow by convection)
46
Convection at surface of the Sun
The visible top layer shows granulation with areas of rising gas surrounded by areas of sinking gas
47
Rising gas vs Sinking gas
Rising gas is hotter and brighter Sinking gas is cooler and darker
48
Sunspots
Cooler than other parts of the Sun's surface
49
Solar prominences
Erupt high above the Sun's surface and caused by magnetic activity
50
Solar flares
Send fast bursts of x-rays and charged particles into space caused by magnetic activity
51
Coronal mass ejections
Send bursts of energetic charged particles out through the solar system
52
The Hertzsprung-Russel Diagram (HRD)
Plots the luminosity and temperature of stars
53
Distance from "spectroscopic parallax"
1. Measure the star’s apparent magnitude m and spectral classification 2. Use spectral classification to estimate luminosity (absolute magnitude M) from HRD 3. Apply inverse-square law to find the distance Magnitude version: m – M = 5 log d - 5
54
What 5 things does the H-R diagram depict?
Temperature Color Spectral Type Luminosity Radius
55
Luminosity
from brightness and distance
56
Temperature (stellar)
from color and spectral types
57
Star clusters
Groups of stars with the same age, distance, motions, and chemical composition
58
Open cluster
A few thousand loosely packed stars (Pleiades)
59
Globular cluster
Up to a million or more stars in a dense ball
60
Where do stars form?
In dark clouds of dusty gas in interstellar space
61
Interstellar medium
The gas between stars
62
Most of the matter in star-forming clouds is in the form of ...
Molecules (H2 and CO)
63
Interstellar dust causes background stars to appear...
fainter and redder
64
What passes through a cloud more easily than visible light?
Long-wavelength infrared light
65
What from a newborn star is often blocked by dusty clouds where the star is formed?
Visible light
66
Dust grain that absorb visible light heat up and emit...
Infrared light
67
Gravity can create stars only if...
it can overcome the force of thermal pressure in a cloud
68
Emission lines from molecules in a cloud can prevent a pressure buildup by converting thermal energy into...
Infrared and radio photons
69
Disks
probable birthplace of planets
70
Protostar
looks like a star but its core is not yet hot enough for fusion to take place (baby star)
71
What leads to disks and jets?
Angular momentum of cloud
72
Main sequence star
Stars that are fusing hydrogen into helium
73
Degeneracy Pressure
Laws of quantum mechanics prohibit 2 electrons from occupying same state in same place
74
Brown Dwarfs
Starlike objects not massive enough to start fusion
75
Low mass stars
<2 solar masses core helium burning, end up as white dwarf stars
76
Intermediate mass stars
2-8 solar masses advanced nuclear burning, end up as white dwarf stars
77
Massive stars
>8 solar masses very advanced nuclear burning, become neutron stars, black holes, or worse
78
Stars become what 3 things after its time on the main sequence is over?
Larger, redder, and more luminous
79
Life Stages of a High-Mass Star
1. Main Sequence: H fuses to He in core 2. Red Supergiant: H fuses to He in shell around He core 3. Helium Core Burning: He fuses to C in core while H fuses to He in shell 4. Multiple Shell Burning: Many elements fuse in shells 5. Supernova leaves neutron star or black hole behind
80
H to He by the CNO cycle
High-mass main sequence stars fuse H to He at a higher rate using carbon, nitrogen, and oxygen as catalysts (helpers) He fuses to C in core Then He can fuse with C and heavier atoms
81
Why is iron a dead end for fusion?
nuclear reactions involving iron do not release energy
82
Energy and neutrons released in a supernova explosion enable elements heavier than iron to form including ...
Gold (Au) and Uranium (U)

Astronomy (3 decks)

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