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Astronomy > Midterm > Flashcards

Midterm Flashcards

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
Q

Newton’s Version of Kepler’s 3rd Law

A

(M1+M2)p^2=a^3
p= orbital period (yrs)
a= AU
M1+M2= sum of masses (solar masses)

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26
Q

Atomic Number

A

The number of protons in nucleus

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27
Q

Atomic Mass Number

A

The # of protons + neutrons

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28
Q

Molecules

A

Consists of 2 or more atoms
(H20, CO2)

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29
Q

Quantum Theory

A

Electrons in atoms are restricted to particular energy levels

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30
Q

In energy level transitions, what does jumping up or down cause?

A

Jump up= can occur by the absorption of a photon
Jump down= can lead to the emission of a photon of light

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31
Q

Wavelength

A

the distance between 2 wave peaks

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32
Q

Frequency

A

the number of times per second that a wave
vibrates up and down

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33
Q

The Electromagnetic Spectrum

A

Gamma rays S WL/ H F
X-rays
UV
Visible
Infrared
Microwave
Radio L WL/ S F

34
Q

Continuous Spectrum

A

contains all wavelengths of light in a certain range

35
Q

Emission Line Spectrum

A

the source emits specific wavelengths of radiation

36
Q

Absorption Line Spectrum

A

dark lines or gaps in the spectrum corresponding to wavelengths that are absorbed by the gas

37
Q

The Doppler Shift

A

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
Q

Hydrostatic Equilibrium

A

Inward gravitational force= outward pressure changes

39
Q

What does pressure depend on?

A

temperature and density

40
Q

Core

A

Hot enough for nuclear fusion

41
Q

Layers of the sun

A

Core
Radiation zone
Convection zone
Photosphere
Chromosphere
Corona
Solar Wind

42
Q

Proton-Proton Chain

A

The Sun releases energy by fusing 4 hydrogen nuclei into 1 helium nucleus

43
Q

What stays in the core and what is released as gamma rays?

A

Helium stays in the core
Energy is released as gamma rays

44
Q

Radiation zone

A

Hotter and is relatively transparent
(energy flow by light)

45
Q

Convection zone

A

Cooler and is more opaque
(energy flow by convection)

46
Q

Convection at surface of the Sun

A

The visible top layer shows granulation with areas of rising gas surrounded by areas of sinking gas

47
Q

Rising gas vs Sinking gas

A

Rising gas is hotter and brighter
Sinking gas is cooler and darker

48
Q

Sunspots

A

Cooler than other parts of the Sun’s surface

49
Q

Solar prominences

A

Erupt high above the Sun’s surface and caused by magnetic activity

50
Q

Solar flares

A

Send fast bursts of x-rays and charged particles into space caused by magnetic activity

51
Q

Coronal mass ejections

A

Send bursts of energetic charged particles out through the solar system

52
Q

The Hertzsprung-Russel Diagram (HRD)

A

Plots the luminosity and temperature of stars

53
Q

Distance from “spectroscopic parallax”

A
  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
Q

What 5 things does the H-R diagram depict?

A

Temperature
Color
Spectral Type
Luminosity
Radius

55
Q

Luminosity

A

from brightness and distance

56
Q

Temperature (stellar)

A

from color and spectral types

57
Q

Star clusters

A

Groups of stars with the same age, distance, motions, and chemical composition

58
Q

Open cluster

A

A few thousand loosely packed stars (Pleiades)

59
Q

Globular cluster

A

Up to a million or more stars in a dense ball

60
Q

Where do stars form?

A

In dark clouds of dusty gas in interstellar space

61
Q

Interstellar medium

A

The gas between stars

62
Q

Most of the matter in star-forming clouds is in the form of …

A

Molecules
(H2 and CO)

63
Q

Interstellar dust causes background stars to appear…

A

fainter and redder

64
Q

What passes through a cloud more easily than visible light?

A

Long-wavelength infrared light

65
Q

What from a newborn star is often blocked by dusty clouds where the star is formed?

A

Visible light

66
Q

Dust grain that absorb visible light heat up and emit…

A

Infrared light

67
Q

Gravity can create stars only if…

A

it can overcome the force of thermal pressure in a cloud

68
Q

Emission lines from molecules in a cloud can prevent a pressure buildup by converting thermal energy into…

A

Infrared and radio photons

69
Q

Disks

A

probable birthplace of planets

70
Q

Protostar

A

looks like a star but its core is not yet hot enough for fusion to take place
(baby star)

71
Q

What leads to disks and jets?

A

Angular momentum of cloud

72
Q

Main sequence star

A

Stars that are fusing hydrogen into helium

73
Q

Degeneracy Pressure

A

Laws of quantum mechanics prohibit 2 electrons from occupying same state in same place

74
Q

Brown Dwarfs

A

Starlike objects not massive enough to start fusion

75
Q

Low mass stars

A

<2 solar masses
core helium burning, end up as white dwarf stars

76
Q

Intermediate mass stars

A

2-8 solar masses
advanced nuclear burning, end up as white dwarf stars

77
Q

Massive stars

A

> 8 solar masses
very advanced nuclear burning, become neutron stars, black holes, or worse

78
Q

Stars become what 3 things after its time on the main sequence is over?

A

Larger, redder, and more luminous

79
Q

Life Stages of a High-Mass Star

A
  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
Q

H to He by the CNO cycle

A

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
Q

Why is iron a dead end for fusion?

A

nuclear reactions involving iron do not release energy

82
Q

Energy and neutrons released in a supernova explosion enable elements heavier than iron to form including …

A

Gold (Au) and Uranium (U)

Astronomy (2 decks)

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