Term
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Definition
| When the electrons and protons in the nucleus are crushed together till only neutrons are left. |
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Term
| neutron degeneracy pressure |
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Definition
| very stiff! Neutrons are touching. |
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Term
Neutron Stars:
Mass
Radius
Density |
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Definition
Mass: 1-3Msun
Radius: 10 km (6 miles)
Density: 10^11 kg/cm3 |
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Term
| Why do neutron stars spin so rapidly? |
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Definition
Because Angular momentum is conserved! L=L
Mass doesn't change. |
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Term
| Why do neutron stars have a very strong magnetic field? |
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Definition
| Core contracts and carries field with it. |
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Term
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Definition
| occur from strong magnetic field and rapid rotation in Neutron stars. |
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Term
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Definition
| strong magnetic fields at magnetic poles. |
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Term
| "beamed" radiation comes from... |
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Definition
| accelerated particle emissions at "hot spots" |
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Term
| "searchlight" rotates when... |
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Definition
| rotation axis does NOT equal magnetic field axis. |
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Term
| Pulse period is the same as the... |
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Definition
|
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Term
| typical pulsar periods are... |
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Definition
| .03-1 sec long. (1-30 spins a second) |
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Term
| What happens when white dwarves are in close binaries? |
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Definition
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Term
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Definition
| happen in neutron star binaries and show up as x-rays because of a MUCH stronger gravity. |
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Term
| Millisecond pulsars form when... |
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Definition
| accretion causes neutron star to spin 1000 times faster. |
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Term
| infallible matter orbits much faster than the neutron star spins.. |
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Definition
| but can speed up neutrons spinning over time. |
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Term
| A neutron star can be crushed further. T/F |
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Definition
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Term
| White dwarves are roughly ____ sized. |
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Definition
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Term
| Black holes are the end of stars that exceed _____solar masses. |
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Definition
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Term
|
Definition
1. light always travels at the same speed.
2. nothing is faster than light
3. all things including light are attracted by gravity |
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Term
| What happens when the escape speed becomes faster than light? |
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Definition
|
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Term
|
Definition
| the critical radius where the escape speed=the speed of light |
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Term
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Definition
| the sphere around the schwarzchild radius |
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Term
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Definition
| when light loses its energy around a black hole and appears red |
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Term
| light slows down near a black hole. |
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Definition
| FALSE. it gets redshifted. |
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Term
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Definition
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Term
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Definition
| When oscillations slow down near a black hole's event horizon and therefore time slows too... |
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Term
| What happens at the event horizon? |
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Definition
| her clock would stop, we'd never see her cross over, everything would stay the same to her, our light would appear bluer, and our time would speed up. No physical boundary at event horizon. |
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Term
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Definition
| everything being crushed to a point in a black hole |
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Term
| How can we SEE black holes? |
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Definition
| Through close binaries. Accretion disks have strong X-rays, and the matter getting sucked in also heats up, and emits light which we can measure. |
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Term
|
Definition
example of black holes existing.
spectral class 25Msun
STRONG XRAY SOURCE |
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Term
| Why can't black holes in binaries be X-ray bursters? |
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Definition
| Because there is no surface for the material to accumulate on |
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Term
|
Definition
|
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Term
| 3 main parts to a spiral galaxy |
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Definition
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Term
|
Definition
| change with time because they pulsate luminosity |
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Term
| 2 types of Variable Stars |
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Definition
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Term
| RR Lyrae Variable Stars... |
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Definition
pulsate the same way.
Have 0.5-1 periods a day.
LOW MASS |
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Term
|
Definition
pulsate differently
1-100 days of period
HIGH MASS |
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Term
| Why are variable stars unstable? |
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Definition
| Because their temperature and radius vary regularly causing pulsations. |
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Term
| What is the relationship between period and luminosity? |
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Definition
| FLUX = luminosity/distance^2 |
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Term
| Where can RR Lyraes only be seen? |
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Definition
| Globular Clusters in OUR galaxy. |
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Term
| Shapely determined WHAT about Globular Clusters? |
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Definition
1. far from the sun
2. 3D spherical
3. map out true extent of our galaxy
4.make up the galactic halo |
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Term
| The galactic center is how far from the sun? |
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Definition
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Term
| Globular Clusters and Halo stars are what color and how old? |
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Definition
| red, 10-15 billion years. |
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Term
|
Definition
1. approx. Solar metallicity
2. mostly young stars (less than 7 bil.)
3.contains HI and HII gasses. |
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Term
|
Definition
1. metal-poor
2. mostly old stars
3. HI gas but no HII
4. Little dust |
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Term
|
Definition
1. Metal-rich
2. intermediate to old stars
3. little gas or dust |
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Term
| How long does it take the sun to orbit the galactic center? |
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Definition
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Term
| Spiral arm structure theories. |
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Definition
| Spiral Density Waves, Self propagating Star formation |
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Term
| Spiral Density Waves Theory |
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Definition
| Spiral wave pattern is stationary and particles move through it. (Traffic example!) |
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Term
|
Definition
Spiral
Barred Spiral
Irregular
Elliptical |
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Term
|
Definition
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Term
|
Definition
| object at center of our galaxy a million times more luminous than the sun. |
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Term
|
Definition
swarzchild radius .1 AU or 15 million km
mass 4-5 million times the sun
radiation from accretion disk
less than 10 AU across |
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Term
|
Definition
white dwarves
brown dwarves
very low mass stars
neutron stars
black holes
WIMPS |
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Term
|
Definition
| Unaccounted Mass in other galaxies. Lensed light. |
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Term
|
Definition
| galaxies with an energy source beyond that of stars. MUCH more luminous! |
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Term
| 3 types of active galaxies... |
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Definition
|
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Term
|
Definition
luminosity comes from a small region in the galactic nucleus (1000x brighter than ours)
fluctuations origination from a very tiny object |
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Term
|
Definition
emit their energy in radio waves
STARS CANT DO THIS
emissions originate from "core-halo" regions or "lobe" regions |
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Term
| "Core-Halo" emissions come from... |
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Definition
| small nucleus with halo of weaker emissions around it. |
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Term
|
Definition
have HUGE luminosities.
powered by larger scale version of a pulsar.
creates jets. |
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Term
| What percentage of infalling mass is converted to energy before entering the event horizon of a black hole? |
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Definition
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Term
| Direct evidence of the Accretion Disk hypothesis can be found in... |
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Definition
| The HST image of the Lobe radio galaxy called NGC4261 |
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Term
| What is the connection between Quasars and Black Holes? |
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Definition
| Black holes start in center of young galaxies, shine as a quasar until all infalling gas is used up and a regular black hole is left. |
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Term
| What happens as the fuel depletes in a Quasar? |
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Definition
| It turns into a Seyfort galaxy or a radio galaxy, then eventually a normal galaxy with a black hole at the nucleus. |
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Term
| The Milky way shows evidence for a dormant black hole. T/F |
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Definition
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Term
|
Definition
| a gravity-bound group of less than 20 galaxies including our own. |
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Term
| What cluster is found within 30 mpc of our local group? |
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Definition
|
|
Term
| What cluster makes up 150 mpc of galaxies? |
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Definition
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Term
|
Definition
| radiates energy away in the form of light because of gravity being released by contraction. |
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Term
| ___ determines luminosity! |
|
Definition
|
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Term
|
Definition
| Gravity and internal pressure is balanced. |
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Term
| Main Sequence to Red Giant... |
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Definition
| H (91%) and He (9%) burn in the core. When H gets used up, nuclear reactions stop, the core contracts, gets hotter, heats outside layers, creates a hot shell, star gets brighter, shell causes outer layers to expand and cool, RED GIANT (takes 100 million years) |
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Term
|
Definition
when helium fuses into carbon at 10^8 K degrees.
... 3He-->C |
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Term
| Red Giant to Red SuperGiant |
|
Definition
Core reaches 10^8K
HELIUM FLASH
core expands, luminosity decreases
Helium runs out
Outer layers expand and cool again.... SUPERGIANT (10,000 yrs) |
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Term
| Supergiant to White Dwarf (and planetary nebulae) |
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Definition
| core heats up and contracts, shell He burning increases, Helium flashes occur INSIDE the shell, surface layers pulsate and are ejected. White dwarf is revealed and planetary nebulae. |
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Term
|
Definition
have nothing to do with planets! much smaller than emission nebulae. (contain C,N,O)
emit line radiation |
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Term
| White Dwarf characteristics |
|
Definition
1/2 sun's mass
size of earth
low luminosities |
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Term
|
Definition
| when a white dwarf in a binary system forms an accretion disk, and the surface ignites. |
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Term
| Higher Mass Stars and their deaths... |
|
Definition
gravity squeezes core and ignites CNO cycle (600 years)
each fuel creates shell
eventually core collapses, neutron's touch (neutron degeneracy pressure)
Density reaches 100 billion kg/cm^3
core bounces and EXPLODES (SUPER NOVAE) |
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Term
|
Definition
|
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Term
|
Definition
| long term effects of Nova situation |
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