Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
59 Cards in this Set
- Front
- Back
Kirchoff's Laws of Spectroscopy |
1. hot solid or hot, dense gas produces an emission-line spectrum (rainbow) 2. a hot, low-density gas produces an emission-line spectrum (black w/ color lines) 3. a continuous spectrum viewed through a cool gas produces an absorption-line spectrum (rainbow w/ black lines) |
|
continuous blackbody spectrum |
emitted by a hot solid or hot, dense gas |
|
emission-line spectrum |
produced by hot, low-density gas |
|
absorption-line spectrum |
continuous spectrum viewed through cool gas |
|
distance ladder |
find distances of stars using radar or parallaxes |
|
closer stars have _____ parallax angles |
larger |
|
further stars have _____ angles |
smaller |
|
limitations of parallax methods: |
hard to measure stars when they are far away |
|
luminosity |
rate at which a light source emits energy -use apparent brightness to measure B = L/4(pi)d^2 L = 4(pi)R^2(theta)T^4 |
|
stellar spectra |
the hot, dense photosphere at a star is surrounded by a thin, slightly cooler atmosphere |
|
OBAFGKML |
spectra determined by temperature, O is hottest, L is coolest |
|
HR Diagram |
luminosity v temperature |
|
Main Sequence |
where ~85% of stars lie; 3000K - 50,000K the Sun is a MS star |
|
giant |
brighter than MS stars of same temp, have larger R; |
|
supergiants |
top of the HR diagram |
|
white dwarfs |
fainter than MS of same temp, smaller R; bottom right corner of HR |
|
4 physical parameters |
luminosity (L): derived from App Brightness and Distance temperature (T): color of spectrum mass (M): measure for binary stars using Newton's version of Kepler's 3rd Law radius (R): direct imaging for giants and SG or other methods (eclipse) |
|
what keeps stars from flying apart? |
gravity |
|
when a star contracts, the radius goes down and the star becomes more ___ bound? |
gravitationally |
|
hydrostatic equilibrium |
the balance between gravity and pressure results in core/envelope structure |
|
the lifetime of a star equation: |
internal energy / luminosity |
|
energy sources: |
chemical, gravitational, nuclear |
|
chemical energy: |
burning by oxidation, muscle power |
|
gravitational energy: |
water running downhill, heat from meteorite impacts |
|
nuclear energy: |
fusion of H into Helium sun powered primarily by Proton-Proton chain nuclear fusion reaction |
|
Kelvin-Holmes Mechanism: |
way to use gravitational binding energy to power the Sun chemical and gravitational energy not enough to power the sun |
|
nuclear fusion happens two ways: |
1. P-P chain: low core, low temp; 4 H --> 1 He 2. CNO cycle: high core, high temp; C acts as a catalyst to fuse 4 H into 1 He nucleus w/ N and O as intermediate products |
|
Hydrostatic thermostat: |
controls nuclear fusion in stellar cores |
|
if fusion is too fast: |
core heats, increase pressure, core expands, core cools, and fusion slows |
|
energy is transported to the surface 3 ways: |
1. radiation: energy carried by photons 2. convection: when hot buoyant gas rises faster than it can radiate its heat away 3. conduction: when heat is transported from atom-to-atom in a dense medium |
|
thermal equilibrium |
occurs when energy generation is balanced by the transport of the energy to the surface to be radiated away |
|
red dwarfs |
lowest mass in MS, fully convective; p-p chain |
|
lower MS |
have radiative cores and collective envelopes; p-p chain |
|
upper MS |
convective cores and radiative envelopes; CNO cycle |
|
thermal equilibrium |
energy generation = luminosity |
|
low mass MS |
burns fuel slow so should last a long time (civic) |
|
high mass MS |
burns fuel quickly so should leave MS in shorter time (Jeepy) |
|
3 stages of formation: |
1. protostar phase: built up mass by accretion (hydrostatic eq) 2. pre-main sequence phase: energy from gravitational contraction (thermal eq) 3. zero-age main sequence: energy from core H fusion (Hydrostatic and Thermal Eq) |
|
GMC |
giant, cold interstellar clouds of molecular hydrogen (H2) supported by internal gas pressure, weak magnetic fields and gas motion |
|
how to trigger a collapse of GMC: |
1. cloud-cloud collision 2. shocks from nearby supernova explosions 3. passage through a spiral arm of the galaxy |
|
low-mass star evolution |
Pre-MS, MS, RG, HB, AG, WD |
|
Pre-MS energy source (LM) |
gravity |
|
MS energy source (LM) |
core H fusion |
|
RG energy source (LM) |
shell H fusion |
|
HB energy source (LM) |
He core and H shell fusion |
|
AG energy source (LM) |
He shell and H core fusion |
|
WD energy source (LM) |
residual internal heat |
|
white dwarf |
remnants of a low-mass star C-O WD or O-Ne-Mg WD |
|
white dwarf thermonuclear supernovae |
when the mass of a white dwarf exceeds 1.44, electron degeneracy fails and WD collapses and explodes as supernova |
|
how WD exceeds 1.44? |
1. binary accretion: WD gets matter from donor 2. double WD merger: double WD close binary and they converge -- BOOM too heavy |
|
neutron stars |
collapsed cores left after core collapsed supernova of massive stars |
|
pulsars |
pulsating radio sources |
|
black hole |
when a neutron star collapses, the remnant core becomes a black hole! a BH is the most extreme object, super strong gravity |
|
event horizon |
point of no return for objects near the black hole |
|
gravitational lensing |
bent light because of strong gravitational field of black hole |
|
continuous blackbody spectrum |
hot, dense gas |
|
star clusters |
groups of stars moving together through space; share common properties (distance, age, etc) |
|
open clusters |
space clusters containing 100s to 1000s of stars many hot, blue MS stars |
|
globular clusters |
rich spherical clusters w/ 10^5 or 10^6 stars many red giants, no blue, hot MS |