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astronomy 3

exam 3

QuestionAnswer
parallax apparent position changes relative to background stars. _______, p, is half the apparent shift.
parsecs "par"allax "sec"ond. the distance where 1 AU in linear diameter subtends 1"
apparent magnitude VS. absolute magnitude depends on (1) Intrinsic brightness. (2) Distance VS. other removes those factors and assumes all stars are at a uniform distance of 10 parsec.
parallax (math) distance = 1/p or p= 1/distance
Atomic Structure # of electrons= # of protons - for a stable atom. PROTON- positive charge,mass= 1.6726x10^-27kg NEUTRON-no charge, mass= 1.675x10^-27kg ELECTRON-negative charge,mass= 9.1x10^-31kg
elements atoms with different #'s of protons
ions same element,different # of electrons
Isotopes same element, different # of neutrons
What can we learn from light? (slide 29) Temperature using Wien's Law Energy Flux using Stefan-Boltzman Law Luminosity- total energy emitted Radius- physical size mass using Kepler's 3rd law chemical composition from stellar spectra
3 types of spectra (1)Continuum Spectrum. (2)Emission Spectrum. (3)Absorption Spectrum.
Continuum Black Body Radiation. The radiation emitted by a heated object. Examples: light bulb, hot coals, ice cubes. Starlight can be approximated as a black body.
Emission or each atomic number Z there are infinite energy levels: n=1,2,3... A drop in energy levels releases a photon with the corresponding energy, delta E EVERY ELEMENT HAS A UNIQUE SPECTRUM
Absorption Continuum source viewed through an emission source. Electrons absorb specific wavelengths to raise up to a higher energy level. OPPOSITE OF EMISSION
Spectral classification original classes A-Q were merged and re-ordered to current 7 class: (hottest)O B A F G K M (coolest)
O temp-40000K Balmer-weak other lines- Ionized He mass-40 lifetime on MS- 1Myr
B temp-20000K Balmer-medium
A temp-10000K Balmer-strong Other lines-Ca Weak Mass-3.5 Lifetime on MS-440 Myr
F temp-7500K Balmer-Medium Other lines-Ca weak Mass-1.7 Lifetime on MS-3Gyr
G temp-5500K Balmer-weak Other lines-Ca medium Mass-1.1 Lifetime on MS-8 Gyr
K temp-4500K Balmer-Very Weak Other lines-Ca strong Mass-.8 Lifetime on MS-17 Gyr
M temp-3000K Balmer-very weak Other lines-TiO strong Mass-.5 Lifetime on MS-56 Gyr
Visual Binaries the two stars can both be resolved in a telescope
Spectroscopic Binaries evidence for two stars in the spectrum
Eclipsing Binaries variations in brightness when one passes in front of the other
Astrometric Binaries (not in textbook) companion not observed, but star wobbles from its gravity
types of stars- Main Sequence stars burning H into He in their cores position on H-R diagram- declining squiggly line
types of stars- Giants (supergiants) stars that have exhausted their core H, and burn larger elements position on H-R Diagram-above line (upper right)
types of stars- White dwarfs hot, dense remains of a giant star's C/O core position on H-R diagram- below line (lower left)
H-R diagram possible axis y-axis - (1)Luminosity (2)Radius (3)Luminosity class (4)Absolute Magnitude x-axis - (1)Temperature (2)Spectral Class (OBAFGKM)(3)B-V Color index
Luminosity Classes Ia Bright Supergiants – Rigel (Orion) Ib Supergiants – Polaris (Ursa Minor) II Bright Giants – Adhara (Canis Major) III Giants – Capella (Auriga) IV Subgiants – Altair (Aquila) V Main Sequence – Sun
Determining Luminosity with spectrum Width of lines indicate density. Higer density, more collisions in gas, broad lines. Low density, less collisions, narrow lines. Blue – Bright Supergiant, low density Red – Giant, broader lines, higher density Black – Main Sequence, very broad lines
Main Sequence Mass-Luminosity Relationship larger the mass the more luminous it is.
hydrostatic Equilibrium the condition in which the weight bearing down at a particular point within an object is balanced by the pressure within the object. Stars exist in this.
4 fundamental forces-Gravitional massive objects attract each other, infinite
4 fundamental forces-Electromagnetic Charged particles interact, EM radiation, infinite
4 fundamental forces-Weak Nuclear cause of B-decay (beta?), radioactivity,small scale 10^-18 m
4 fundamental forces-Strong Nuclear holds nuclei together, small scale 10^-15
the proton-proton chain- fusion details The Proton-Proton Chain 1H + 1H -> 2H + e+ + n 2H + 1H -> 3He + g These both occur twice, then 3He + 3He -> 4He +1H + 1H Energy is released in 3 Forms: e+ is a positron v is a neutrino (swirl thing) is a Gamma Ray -> carries of the energy from fus
anitmatter & annihilation 2 particles- same mass, different charge. positron-> + charge antiproton-> - charge its when they collide(?)
Sun- Radiative & Convective Zones R- photons absorbed & re-emitted in hot, dense interior regions C- pockets of hot gass rise up to sun's surface
sun- photoshpere the visible surface, only 500km thick (spectrum>) Lower ____________- Dense enough to emit light, not so dense that light cannot escape Continuum Upper_________- even thinner gas, where some photons are absorbed Absorption
Sun-Chromoshpere prominences-pink color is a blend o the balmer series lines of hydrogen. there's a temperature increase from the chromosphere to the corona
sun-corona spectrum the sun's crown. A 3 component spectrum: Absorption–reflection of Sun’s spectrum from dust in corona. Continuum–Lacking absorption lines due to high temps, many collision, and Doppler shifts smearing out the lines. Emission–Line from highly ionized gases
solar wind Gas flow along magnetic field lines. 300-800 km/s sun loses 10^7 tons of matter per year. that's only 10^-14 of its mass per year.
sun-corona the sun's crown. The Gas: Temperatures range from 500,000 K to 2,000,000 K Very low density, 1-10 atoms/cm3 Extends for several Solar radii
graules evidence of convection. each about the size of texas. Doppler shifts show: centers rising, Edges falling. CAUSED BY CONVECTION hot plasma rising up, releases energy & sinks back down
supergranules over 2x earth size caused by large convection currents
filaments dark streaks are large arcs of flame reaching up from surface. just prominences from a different point of view
spicules jets of plasma reaching from the surface a few earth radii into the corona
sunspot a cooler,transitory region on the solar surface produced when loops of magnetic flux break through the surface of the sun. go through an 11 year cycle because of magnetic polarity of the sun.
solar flares violent explosions, occur in minutes. 10^9 MT (Megatons of TNT) 3 CLASSES--- C- little effect on earth M-Brief radio blackouts at poles X-global blackouts and intense radiation storms
Coronal mass Ejections Massive Explosions. Plasma sent into solar system (electrons,protons,some He, O,Fe) 10^11kg of material at 1000km/s cause blackouts and geomagnetic storms
Dynamo Effect Origin of the Magnetic Field of the Sun (and Earth)CONDUCTING MATERIAL, RAPID ROTATION, CONVECTION. occurs at the bottom of the convective layer
Zeeman Effect having a magnetic field allows it to carry through the spectra and transitions through the energy levels
Differential rotation the top of the sun spins slower than the equator. the day at the north pole is 35 days and at the equator it is 25 days
babcock model because of differential rotation the sun's magnetic field gets twisted "meridional magnetic field is transormed into azimuthal magnetic field"
sun's core the energy producing center. the hottest layer
Main Sequence Lifetimes lifetime, (weird curly T, Tau)= fuel/rate of consumption. More Massive stars lead shorter lives: More gravity, so they must burn fuel faster to maintain balance
Main sequence Lifetime (math) tau= M/L = M/M^3.5 = 1/M^2.5 tau= M^-2.5 (10^10 yr)
stages of Evolution- Main Sequence as nuclear burning continues in these stars, He ash begins to build up in core. (after sun's 10^10 yr lifetime, no H is left in core)
stages of Evolution-Red Giant Branch temperatures too low in core for He fusion, He core collapses. Gravitational Potential Energy becomes Thermal Energy around core. H burning shell forms and star RG (Outer layers expand)
stages of Evolution-Horizontal Branch core temp. increases until it can overcome the electromagnetic repulsion and begin fusion. HELIUM FLASH runaway He burning, lasts for a few minutes. can't achieve 100MK some oxygen can form as well at this stage. Radius decreases, surface temp. increases
stages of Evolution-Asymptotic Red Giant Branch core He burning complete, C & O remain. Temperatures too low for C fusion, C/O core collapses. He burning shell forms. Star becomes a red giant again.
stages of evolution- Planetary Nebula low mass stars cannot start C burning T< 600MK Strong Stellar Wind carries off mass.
stages of evolution- White Dwarf C/O core continues to contact. Gravitational Potential Energy becomes Thermal Energy. Matter becomes degenerate again.
triple alpha process happens during the horizontal branch. core temp. increases until it can overcome the electromagnetic repulsion and begin fusion. HELIUM FLASH runaway He burning, lasts for a few minutes HELIUM FUSION INTO CARBON some oxygen can form as well at this stage
Electron degeneracy pressure it balances Gravitational pressure, compression ceases.
Chandrasekhar Mass Limit more mass -> smaller radius Above 1.4 Mo electron degeneracy FAILS Models indicate stars up to 8 Mo can lose enough mass to form White dwarfs
star clusters groups of stars, formed from same cloud (composition), at the same time (age), at the same distance, but different masses
open cluster 10-1000 stars. 25 parsecs in size. plane of galaxy. Mostly young stars. loosely bound gravitationally, will eventually be pulled apart
globular clusters 10^4-10^6 stars. 10-30 parsecs in size. Halo around galaxy. Tightly bound. Made up of old (metal poor) stars, ages similar to age of the Galaxy
Classical Nova Mass transfer onto White Dwarf from companion. H on surface burns off. Star Brightens for a few days. Original White Dwarf remains. Periodic over 10-1000 years.
Type Ia Supernova Explosions white dwarf star in binary system accretes mass and exceeds the 1.4Mo Limit. Subsonic burning of C/O creates runaway fusion reactions which results in the explosion. serves as a "standard candle" since every Ia event are from stars with identical masses.
CNO Cycle 4 H atoms in -> 1 He atom out C,N, & O just the catalysts & gamma ray photons per reaction. (pp chain produces 6 gamma rays)
Cepheid Variables Period= 5.37 days. Apparent magnitude varies from 3.6 to 4.3. Spectral class goes from F5 to G3
Period- Luminosity Relationship For Cepheids ONLY. Observe period and apparent magnitude, P-L relation gives absolute magnitude, with m and M we can determine DISTANCE
Mass star evolution- Onion Layer Core Cycle of shell burning and core burning continues. Shells of different burning processes surround core
Mass star evolution- Iron Limit After Si burning, we have an inert Fe core. We cannot gain energy from Fe fusion. No new round of core burning can take place, so GRAVITY begins to collapse the core.
Neutron Degeneracy Pressure 1934 ->The prediction of stars supported by neutron degeneracy (Baade & Zwicky) Mass>1.4 Mo but mass<3 Mo. NEUTON STAR Electrons+protons combine to form neutrons, they run out of room to move around. Neutrons prevent further collapse, much smaller!
types of explosions- Type I explosions have no H lines and are further classified by Si and He lines. Ia- Si and He Ib- no Si,He Ic no Si, no He
types of explosions- Type II explosions have H lines
Specifics- Type II and Ib, Ic gravitational core collapse fo a massive star. Birth of a Neutron Star and Supernova Remnant. Black Holes can form fromt the neutron star if the initial mass is > 20-25 Mo
Specifics- Type Ia thermonuclear Detonations of a White Dwarf Star. NO neutron star (or black hole), no Flux of Neutrinos
Core collapse VS Type Ia Both types: E= 10^44 J Core Collapse only: neutrino flux of 10^46 J difference seen in ejected solar material: TYPE Ia- 1,4Mo of ejecta O/Fe=0.765 CORE COLAPSE- 5-20Mo of ejecta O/Fe=72.3
Neutron Star properties Mass-1.4 to 3 solar masses radius- 10 km Density- 10^14 g/cm^3 sugar cube would weigh 100,000,000 tons very small size and spin very fast, STRONG magnetic field (10^12 G)
Binary Neutron Stars Mass transfer can "spin-up" star to periods of milliseconds
X-ray Binary accretion disk bright in X-rays with temperature > 10^6K
X-ray Bursters similar to "classical" nova, just in X-rays not visible
Neutron Star Structure Superfluids rotate without viscosity. Flow create by rotation will NEVER slow down. VERy strong dynamo effect
Special Relativity- Postulate 1 laws of Physics are the same in all INERTIAL reference frames (an inertial reference frame is one that moves at a constant velocity NOT accelerating relative to the observer's rest frame)
Special Relativity- Postulate 2 the speed of light is CONSTANT and independent of source's speed
Special Relativity-Length Contraction moving objects are shorter.
Special Relativity- Time Dilation Moving Clocks Run slower
General Relativity matter curves space-time. light must follow the curve
Equivalence Principle Expanding Special Relativity to include non-inertial (accelerating) reference frames, like GRAVITY. Inertial Mass=Gravitational Mass An accelerating system behaves completely identical to a system in a gravitational field. Textbook=: free fall=free float
Schwarzchild radius Rs= 2GM/c^2 Schwarzchild solved Einstein's equations to describe the gravity around a singularity. Rs defines the EVENT HORIZON
Black Holes All mass collapses to a single point. No volume implies INFINITE density. What we know about the Four Fundamental Forces, what we know about PHYSICS, breaks down inside a black hole. Get to close, and you will become human spaghetti due to tidal forces
Hypernova Gamma Ray Bursts Neutron Star that formed to start explosion, collapses when degeneracy fails. Black Hole formation releases powerful jets of energy. Jets detected before light signal of explosion
E=mc^2 can also be written M=E/c^2 c= 3x10^8
Energy=Luminosity x time from chapter 11 example problem 68
Mass Luminosity Relation L=M^3.5
luminosity the total amount of light emitted L=fxA L=T^4
temperature ranking core is the hottest then corona then photosphere
reconnection when the magnetic field of the sun sort of unwinds. it is responsible for solar flares.
Created by: emilyclawson