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43 Cards in this Set
- Front
- Back
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parallax
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the directional change over a baseline of 1 AU
-the greater the distance the smaller the parallax |
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parsec
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distance at which parallax is one arcsec
-1 parsec = 206265 AU = 3.26 lyrs |
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arcmin
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1/60 of a degree
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arcsec
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1/60 of an arcmin
-1/3600 of a degree = 1/26265 radian |
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Stellar classification (temp)
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OBAFGKM (LT)
- -> high to low (T & M) -F is hotter than K / G has a lower mass than O -#1-5 --> hottest to coolest (O1 > O3) |
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Early stellar classification
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Done by Annie Cannon, alphabetical order
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binary star system
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a star system consisting of two stars orbiting around their common center of mass
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visual binary method
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the angular separation between the two components is great enough to permit them to be observed as a double star in a telescope
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spectroscopic binary method
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show pairs of Doppler-shifted lines that change over time
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eclipsing binary method
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one star passes in front of the other
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Fundamental property of a star is...
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mass
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More massive stars are...
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larger, more luminous, hotter
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fusion requires...
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ramming protons together at high speeds (high temps)
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Proton-Proton Chain
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Hydrogen -> Helium
1) Colliding protons creature deuterium ( ^2H) 2) Protons collide w/ deuterium nuclei to produce Helium-3 (^3He) 3) ^3He nuclei collide to create ^4He |
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Estimated lifespan of Sun
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10Gyrs
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Radiative zone
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Inner 71% of the radius of the sun (15m -100,000K)
-100,000 yrs for photons to escape |
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Convective zone
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Outer 29% of sun's radius
-takes a few hours to transport e out to surface |
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grannulation
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during convection the material that was in contact w/ energy source rises to the surface and cooler material circulates to to the bottom
-why sun looks speckled |
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Sun's atmosphere
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Photosphere - 300mi thick
Chromosphere - 1250mi thick Corona - outermost whisps of light -density drops rapidly, mostly @ corona -temperature is steady until corona where it skyrockets |
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Solar activity
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-differential rotation wraps up magnetic fields
-concentrated field lines can pop out and cause solar flares, sunspots, prominences, etc. |
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Evolutionary track of low-mass star
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MS -> RBG -> He Flash -> HB -> AGB -> Planetary nebulae -> White Dwarf
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Main Sequence Star
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1) H-burning core
-pp chain -uses up all the H in core, star swells |
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Red Giant Branch Star
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2) H-burning envelope
-He-degenerate core -Triple-alpha process -core becomes more and more dense until it becomes electron degenerate --pressure not from moving atoms but from quantum mechanical effect limited by electron packing |
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Helium flash
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3) Bc of high pressures, T in RBG rises to 10^8K star explodes
-triple alpha process -10-20% mass loss |
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Horizontal Branch Star
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4) Stable He core, similar to MS
-H-burning shell -when you exhaust He in the core, evolves off HB -triple alpha process -10-20% mass loss |
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Asymptotic Giant Branch
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5) H-burning shell
-He-burning shell -Degenerate C core w/ no nuclear fusion -no magnetic field, which allows for a lot of mass loss -20-30% mass lost |
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Planetary Nebulae
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6) Basically just the C core surrounded by all of the stuff it ejected. WD @ center ionizes gas via UV radiation
-takes ~30,000 to become a PN and stays that way -takes ~50,000 for ejected mass to clear and reveal WD |
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White Dwarf
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7) Final stage - leftover degenerate C core
-hot but not v luminous -spends rest of eternity cooling -about the size of Earth |
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Triple Alpha Process
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He-Burning
1) Two ^4He nuclei fuse to form an unstable ^8Be nucleus 2) If this nucleus collides w/ another ^4He nucleus before it breaks apart, the two will fuse to for a nucleus of ^12C 3) The energy released is carried off both by the motion of the ^12C nucleus and gamma rays |
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Age of Planetary Nebulae
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1 km/s = 1pc/Myr
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Roche Lobe
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Defines the gravitational territories of binary system stars
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Mass-transfer binary stars
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most stars are in binary systems; and they have different MS lifetimes
-more massive star evolves in RGB while other stays on MS -RGB can only expand so much bc of Roche Lobe, so material is lost to MS star's gravity |
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Type IA Supernovae
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A white dwarf's mass increases over time and if mass reaches 1.4 M(sun) (Chandrasekhar limit) then gravity can overcome electron degenerate pressure. The star collapses and explodes in a Type 1A Supernovae
-"C Flash" - happens in <1 sec and creates the heavier elements |
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High-Mass Star evolutionary track
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MS (10-100M(sun)) -> Supergiants -> Supernovae -> Neutron Star (lower m)/Black hole (higher m)
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CNO Cycle
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H-burning process in high-m stars w/ Carbon as the catalyst bc core temp is higher -alt. pp chain |
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Fusion in Supergiants
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Compression of the core ignites He-burning before core becomes degenerate. Fusion shells build up like layers of an onion
-more massive, heavier elements can fuse, up to Fe |
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Pulsar
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Rapidly rotating neutron star, HIGHLY magnetized. Beam of radiation sweeps over Earth like a lighthouse beam
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Special Relativity
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-E=mc^2
-c=ultimate speed limit -time dilation -compression |
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Time dilation
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Implication of special relativity. Time passes more slowly in a moving reference frame than at rest. "Stretching" of time
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Compression
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Implication of special relativity. An object appears shorter in motion than it is at rest - related to time dilation
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Singularity
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the point where a mathematical expression/equation becomes meaningless
-center of a black hole is a point of infinite density and zero volume (a singularity) |
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Event horizon
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"surface" of a black hole, nothing inside this surface, not even light, can escape
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Schwartzchild radius
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radius of a black hole's event horizon
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