EAS 1180 Prelim 1
what is earths mean density?
5.25 g/cc
nuclear fusion cannot proceed beyond....
56Fe
What is the Kuiper belt?
- lies beyond neptune - Kuiper belt is many times the size of the interior planets - Many objects found here → ex: Pluto - Contains enormous numbers of comets and ice balls
why is alpha decay diff from beta decay and electron capture?
Alpha decay actually ejects particles from nucleus. Beta decay and electron capture maintain the # of nucleons
universe composition percentages?
27% dark matter 68% dark energy 5% ordinary matter --> 4% H and He
how come He burning can only occur in large stars?
He has 2 protons and there is huge repulsion btwn them → this repulsion cannot be overcome by gravity in small stars. Only can happen in larger stars where gravitational force is larger
how does the band of stability relate to isobars?
The band of stability is the minimum mass along an isobar the elements that make the cut for the band of stability are those on the isobar who have mass minima
in general sum, how and when did earth and core form
Various lines of evidence suggest a dominantly homogeneous accretion of Earth → followed by widespread melting and rapid segregation of core from mantle by immiscibility and density separation in the first few tens of millions of years of Earth's history
creating elements heavier than H and He (and under 56Fe) requires....
nuclear fusion
mantle is mostly made up of...
olivine
Inorganic vs organic molecules
organic: C-H bonds Inorganic (no C-H bonds) molecules make up most planetary matter. They form minerals
the farther a shell is from the nucleus...
the larger it is, the more electrons it can hold, and the higher the energies of those electrons.
Organic molecules on Earth generally are associated with...
the liquid state of matter
which kind of elements are very chemically reactive?
those with only 1 or 2 electrons in their shells or those with 1 or 2 missing electrons --> they always try to combine w other elements so that their outermost shell is full
how is wave speed related to wavelength/frequency/period?
v = (wavelength)*(frequency) = (wavelength) / (period)
what is it zircon and why is important?
ZrSiO4 - Extraordinarily durable (both mechanically and chemically) - Persist essentially unchanged in the rock record throughout geologic time - When zircon-bearing rocks break down under weathering, the zircons will be preserved and can be incorporated in new 'detrital' sedimentary rock - Age dating of these zircons with the U-Pb system tells us about crustal ages and can be used to help understand how crustal volumes have grown throughout time
how do u create elements heavier than 56Fe?
neutron capture
the freq at which meteorites strike the earth depends on...
the size
diff classes of meteorites?
"Chondrites" have chondrules and are interpreted to be unaltered fragments from the "solar nebula" from which the planets formed → later accreted to form the rocky planets "Achondrites" have no chondrules and are fragments of broken up tiny planets, called planetesimals. - These broken up planets include iron meteorites - Planets that formed and underwent differentiation → faced collisions and broke up
Discovery of radioactivity has two major impacts on our understanding of the Age of Earth:
(1) Additional source of heat throughout Earth history, keeps planet from losing heat entirely (2) Acts as an absolute time keeper and allows us to move past relative dating
what is dark energy?
- A constant density of energy in the universe that exerts a negative pressure, counteracting gravity - explains the acceleration seen in the supernova data - However, it is still unknown what causes this acceleration
what are magmaphile elements?
- 'magmaphile': elements that want to be in liquids [magmas], as opposed to solids [crystals/minerals] - Magmaphile elements are generally those lithophile elements toward the bottom of the periodic table where the high atomic number generally creates large ionic sizes (e.g., K, Rb, Cs, Ba, Sr, La, Pb, Th, and U) - These elements are too large to fit into our silicate tetrahedra and other common polyhedra that form the building blocks of mineral/crystal structures!
What is the late heavy bombardment?
- 4Ga - A hypothetical epoch in which a large number of asteroids collided with bodies in the inner Solar System.
K-Pg boundary
- 66 Ma - Represents transition from cretaceous to paleogene - When the dinosaurs went extinct - This boundary is present in rocks all around the world
why is the Hf-W system so powerful in deciphering events early in earth/solar system's history?
- 9Myr half-life of the parent Hf182 - diff geochemical behavior of Hf (lithophile, crust) and W (siderophile, core)
transit method for detecting exoplanets
- A planet crosses directly between the observer and its star, blocking some starlight - Orbit must be at a very specific angle - Info about planet radius and orbital period obtained - Uses space telescopes - Larger planets block out more of the starlight, so they are easier to detect (especially around smaller stars) - planets with short orbits are statistically more likely to transit during observation, and are thus easier to detect - This method does not work if the planet's orbit is not perfectly aligned to the observer's viewpoint - Observation of wide swaths of the sky
what happens when u put a beam of visible light thru a prism?
- A prism disperses the colors (wavelengths) of visible light because the various wavelengths are slowed by different amounts as they enter the glass of the prism. - Since their speeds in the glass are different, they are refracted at different angles. -The higher the frequency of the light → the shorter the wavelength → the more its path is bent in the prism (so violet is most bent, red is least bent)
what is the magma ocean theory of earth? what was the justification of it?
- After observing rocks on the moon, showed that at one time, the moon was a magma ocean - since Moon and earth are v closely related → so what happened on moon likely happened on earth. So if moon had a magma ocean, it is likely that the earth did too - Early Earth was HOT, contrary to early beliefs → this heat is from impacts, gravitational compaction, radioactivity, core formation itself was also a heat-releasing process - All these heat-producing processes leads to development of a molten magma ocean on Earth's surface overlying the solid early mantle - Segregation of the metal is more efficient through liquid magma ocean. Creates a more plausible scenario for sinking metal to pawn thru silicates
What is blackbody radiation? relationship btwn temp and BBR freq?
- All bodies (objects) emit electromagnetic radiation at all temperatures above ~ 0 K. This is referred to as blackbody radiation, in reference to an idealized perfect emitter/absorber. - According to the electromagnetic wave model, it is the acceleration of charged particles near the surface of an object that causes this blackbody electromagnetic radiation to be emitted --> The temperature of an object determines the energy available for accelerating charged particles, so the higher the temperature the higher the average frequency of the blackbody radiation
how is earth an example of a natural system?
- All parts of the Earth are in movement - Every Earth component is involved in cycles - The cycles are inter-linked and have feedbacks with one another - This creates a steady-state, far from equilibrium, on short time scales. - On longer (tens of millions of years) time scales, the Earth system evolves - Earth is related to the larger solar system, and to the smaller geological and biological systems of the planet - Earth had a time of origin, and ultimately will end
exceptions to hubble's law? why do these exceptions arise?
- Andromeda, our nearest large galactic neighbor, is actually movingtoward us, not away, and will smash into the Milky Way Galaxy in 4.5 billion years - Galaxies can also have modest local motions as they mill around and gravitationally pull on one another—as the Milky Way and Andromeda are doing - Such exceptions arise because Hubble's law describes only the average behavior of galaxies
what are the characteristics of natural systems?
- Are invariably in movement at all scales bc they are in a disequilibrium state - Are sustained by external energy sources and flow (of energy and matter) through the system - Involve chemical transformations and cycles - Are maintained over a narrow range of states, far from equilibrium, by feedbacks - Contain and are nested within systems at smaller and larger scales - Change over time—creation, long term evolution, and eventual death
what are the important considerations when making molecules from atoms?
- Atoms need to fit together in terms of size as well as charge - in order to grow in a regular pattern, the particular arrangement of the atoms must be infinitely repeatable. --> mineral structures must have symmetry
Radial Velocity Method for detecting exoplanets
- Barycenter - the center of gravity of a system - Stars with orbiting planet(s) themselves orbit the barycenter of the stellar system - Why? Because gravitational force goes both ways. The planet exerts a force on the star, causing the barycenter of the system to be a bit off from the star's center. - Viewed from the side, the star appears to "wobble" → its position shifts slightly over time, in a periodic fashion that can be measured → These measurements can tell us the orbital period of the planet and its mass. - Uses ground-based telescopes - Lower-mass stars (e.g., M dwarfs) are more affected by planets' gravity, so they wobble more, making planet-detection easier - Larger planets, especially on short orbits, exert more gravitational force, so they are easier to detect - Observation of one star at a time
why are inner and outer planets made up of different things?
- Bc of the "differential volatility" of molecules in the temperature gradient that cools with distance from the sun - If u are forming a planet close to sun → temp is super hot → things that have low BP are just gonna evaporate/they will not condense/accrete to form a planet --> Rather REFRACTORY elements (Fe, Mg, Si) will not be vaporized and would be happy to form a solid (like a planet) in a hot environment - Elements are gonna distribute themselves according to their volatility/BPs --> which is why inner and outer planets will have different elemental compositions
Four Main Types of Organic Molecules Involved in the formation of life
- Carbohydrates-- molecules in which hydrogen and oxygen atoms form whole numbers of water molecules (e.g. sugars and starches) - Lipids-- much less oxygen than carbohydrates, and higher energy content per gram; fats in animals and oils in plants - Proteins—most diverse group, long chains of amino acids. - Nucleic acids—long double helix chains of alternating sugars and phosphates. Forms genes
how do we know that meteorites and sun have similar chemical compositions?
- Carbonaceous chondrites have the same nonvolatile element inventory as the sun (they form at super low temps) - Chondrites that form at rly low temperatures are most representative of the composition of our solar system nebula from which our sun/elements formed - Relative abundance of elements in sun match up w relative abundance of elements in carbonaceous chondrites - Fe, O, Mg, Si make up most of the composition of the inner planets, chondrites and sun - All of the nonvolatile elements form in tandem w Oxygen → which is why O is so high in composition
why are chemical transformations and cycles important for natural systems?
- Chemical cycles are a requirement for long term stability in disequilibrium systems. - Cycling itself implies lack of equilibrium because in equilibrium there is no movement. - For systems to have longevity, they must be able to persist over long periods of time → Materials cannot be exhausted, natural systems must recycle ex: rock, carbon, oxygen cycle
what are the requirements for isotopic dating?
- Closed system (did not lose or gain parents/daughters over time) - Decay rate is constant/unchanging - Initial concentration of daughter is known (zero is best) OR initial concentration of parent is known
what are comets? where do they orbit? how are tails formed?
- Comets are basically ice wrapped around a rocky core → mostly ice - Analogous to outer planets (gas giants like neptune, uranus, saturn, jupiter) - in orbits more distant than neptune - Comet tails are created when the ice starts to vaporize after coming too close to the sun
why is the convection of the liquid outer core important?
- Convection of liquid outer core → driven by changes in heat (rly hot core vs cooler mantle) → electrical and magnetic field is created → Earth's geodynamo - geodynamo protects the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from the harmful ultraviolet radiation
what do u see on a graph of distance of galaxy vs recessive velocity of galaxy? why is the origin important? what can u calculate from the data points and why?
- Distance and recession velocity are linearly related! - As distance increases, velocity increases - Straight line means everything started at one place at one time (big bang) - u can use the formula time = distance/velocity to determine when galaxy formed
how did the anorthosite crust form and Eu end up all in it?
- Early on in moon's history like right after the impact when it's energy is really high/hot, we have a lunar magma ocean: layer of unmelted silicate material covered by a completely melted magma layer - Over time the system cools and we form feldspar (Ca Al silicate), olivine, pyroxene (Fe Mg silicates) - Feldspar takes in all the Eu and leaves the magma (that it formed in) depleted of Eu - Feldspar is super light so it floats to the top and this is what forms the monomineral anorthositic crust
how does internal pressure/melting processes vary on earth vs moon?
- Earth has a much greater gravitational field than the moon, therefore the same mass weighs much more - If pressure is a function of the weight of rocks above u, the interior of the moon is under less pressure than an equivalent depth in the interior of the earth - On earth, a lot of the melting that creates crust happens bc of decompression (reducing the pressure) - Melting begins at much greater depths in the moon than on earth → bc it takes more depth to reach higher pressures
why are minerals important?
- Earth is made up of minerals. No minerals, no planet - Life emerges from interactions among minerals, water and atmosphere - Minerals may have established the first template for long repeating molecules that led to RNA and DNA - Minerals are the materials through which all geochemical cycles pass
what is the steady state of radioactive elements?
- Elements are always being created at some rate in stellar interiors (happening in a linear addition) - Elements that are radioactive are always decaying at some rate (exponential decay) - This leads to steady state in the amounts of radioactive elements in the universe when the isotope decays away at the same rate that it is produced
what is evidence for dark matter?
- Evidence for dark matter comes from measured rotation rates (using Doppler shifts) of galaxies as a function of distance from the center - Rotation rates are much higher at the edges of galaxies than those predicted by gravitational theory—this requires the presence of additional nonvisible mass
what is the Silica-oxygen Tetrahedra
- Four oxygens surrounding a silicon ion - Electron sharing between Si4+ and O2- - These tetrahedra combine to make the framework of the silicates
what is the oort cloud
- Furthest reach of our solar system - Billions of potential comets reside - Passing stars can perturb the orbits of oort cloud objects → send them rushing into interior of solar system → they impact other planets/objects and end up being accreted
Ceres
- Has thin/dusty outer crust - Rocky inner core - Water ice layer in between ->100 km in diameter - Smallest and closest dwarf planet
what is homogenous accretion? what makes this model make more sense?
- Initially homogenous body → over time, Fe and Ni settle out - separation predicted by properties of silicate and metal - Higher density of metal relative to silica leads to metal sinking through silicate due to force of gravity - Metal and silicate are immiscible → Think oil and vinegar (immiscible) vs. a mixed drink containing alcohol and water or pop (miscible)
what are the lunar puzzles?
- It is very large relative to its planet (Earth) - only large moon in inner solar system - It has a low density suggesting no (or minimal) core - The moon is younger than Earth by perhaps 50 million years+ - The moon is depleted in siderophile elements, despite having no significant core - The moon is also depleted in volatile elements (those that wanna be in the gaseous state) like H relative to Earth - apart from the volatiles, the composition of the moon looks like Earth's mantle
how do planets grow?
- Large gas giants can grow by gravitationally attracting material from protostellar clouds - Rocky planets form from clumping together of dust grains and grow by accretion and collisions with larger objects
What is anorthosite?
- Lunar highlands made up of Plagioclase → specific kind called anorthosite - it isA mono-mineralic rock made up largely of the mineral anorthite, a plagioclase feldspar with the formula CaAl2Si2O8 - Mono-mineralic igneous rocks are very unusual, and suggest a process of mineral separation and accumulation - Highlands Anorthositic crust is OLD
how is star mass related to temperature? how does this relate to element production?
- Mass is related to temperature for main sequence stars (including sun): hot stars are big, cool stars are small - Small stars will not become hot enough to move beyond H burning - Large stars are hotter and brighter and thereby
define meteor
- Meteors are glowing fragments of rock matter from outside the Earth's atmosphere that burn and glow upon entering the Earth's atmosphere - they are more commonly known as shooting stars - Some meteors, particularly larger ones, may survive passage through the atmosphere to become meteorites, but most are small objects that burn up completely in the atmosphere.
requirements for nuclear fusion to occur?
- Nuclear fusion happens as long as the mass of the product nucleus is lower than the reacting nuclei - Nuclear fusion requires the nuclei to "touch" so the strong force can operate, and this requires very high temperatures. A confined environment helps.
What is chaos? ex?
- Occurs in common mathematical equations where the outcome is so sensitive to minute changes in initial conditions or constants in the equations that long-term prediction is impossible - ex: Weather is a familiar example of a chaotic system, because its behavior cannot be precisely predicted
Indirect evidence for stellar nucleosynthesis (production of elements in stars)?
- Only conceivable source of energy that could keep stars hot is nuclear in its nature - Explosions of large stars (supernovae) have been directly observed - Technetium, a heavy, short lived (radioactive) element not on Earth has been observed in recent supernovae - Direct detection of energy (gamma rays) emitted by r-process during supernova - Observed relative abundances of elements generally matches predictions - Reproduction of stellar reactions in particle accelerators
How did the crust form?
- Partial melting of Earth's solid interior creates magmas (have diff compositions than the solid that they melted out of) that are buoyant and rise to surface - They then can erupt (like a volcano!), or cool in place form crystals and make the crust!
what was the major conflict btwn physicists and geologists in the late 19th century?
- Physicists: We calculate the age of Earth is 20-100 million years based on its current heat flow (the heat loss earth has faced) - Geologists: We know rock formations must form over very long timescales, so 20-100 million years must be too little time. - BUT If the geologists were right, there must be an additional source of heat in the earth → otherwise the earth would have cooled/lost its heat entirely
why is Eu diff from other REE?
- REE are particularly interesting because they mostly have the same valence (+3) and very similar chemical behavior. - Eu, however, under the reducing/oxygen depleted conditions of the moon, has a valence of +2, which permits it to be separated from the other REE --> since it is similar to ionic charge of Ca2+ it can sub readily for Ca in anorthite
what are the diff ways to determine distance in our solar system?
- Radar ranging (few AU) - Parallax (AU → few 1000 light yrs) - Main sequence fitting (100s → 10s of thousands of light yrs) - Cepheid variable stars (100s of thousands → 100s of millions) - Distant standards (white dwarf supernovae (SN1a) and others; 10s of millions to 10+ billion light years)
How does Isotopic dating work?
- Radioactive elements (parents) decay to stable, non-radioactive elements (daughters) - The rate at which this decay occurs is constant and can be measured (decay constant, λ) - If we know the rate of decay and the amount of parent and daughter present, we can calculate how long decay has been occurring.
what is the evidence that the solar system formed from meteorites?
- Relative abundance of elements in sun match up w relative abundance of elements in carbonaceous chondritic meteorites - Meteorites, Earth and Moon are all of the same age
what is the shadow zone? why is it impt?
- S waves can only travel thru objects that have shear strength - fluids do not sustain shearing—you can bend a stick or a metal rod, but not a fluid because it does not have the strength to sustain the shearing force → s waves cannot travel thru fluid - As s waves travel thru the earth, they cannot pass thru the liquid outer core → shadow zone - S- waves disappear in a 'shadow zone' in the Earth that has no shear strength—shows that a component must be a liquid
Self similarity
- Self-similarity is another characteristic of natural systems - This describes a system's tendency to exhibit fractal behavior - Fractals: look the exact same when it is examined over a very large range of scales - You cannot tell the size of a fractal object without a scale bar - Properties apparent from a larger scale often cannot be inferred from the individual parts of the smaller scale
define: siderophile lithophile magmaphile chalcophile atmophile
- Siderophile- prefers to reside with metal (core) Ex: tungsten (W), Fe, Ni - Lithophile- with rock (crust, mantle) -magmaphile- elements that wants to be in liquids (magmas) rather than solids (crystals/minerals) - Chalcophile- with sulfur Can behave like siderophiles when sulfur is not around - Atmophile- in the gaseous state
what are lava worlds?
- So close to their host stars that temperatures are above melting point of surface rocks - Tidally locked - gravity of the star causes one side of the planet to always face the star (typically; can be more complex) - Large day-nightside temp differences
what is a supernova? type 1a supernova?
- Supernova: Explosive death of a large star - Type 1a supernova: Explosive death of a white dwarf that is in the process of engulfing a companion star
what are the two pathways for neutron capture?
- Supernovas create a neutron "machine-gun" that makes neutron-rich isotopes. These then decay to create stable isotopes on the lower right hand side of the band of stability. This is called the " r-process " - In stellar interiors neutrons and protons can be added slowly. They migrate slowly along the band of stability, decaying before another nucleon is added. This is call the " s-process"
what happened immediately after the big bang?
- Temps are so high that no atoms exist → only fundamental particles smaller than neutrons and protons - After some cooling, atoms could begin to coalesce - The only elements produced in significant amounts during this very early phase of universe evolution were H and He
density is controlled by...
- The average number of particles in the nuclei --> Larger masses? Larger densities - How closely the atoms can pack together - High atomic # elements are much denser than low atomic # elements → so the density of a planet tells u lot abt its composition - Incr pressure → decr in volume
what is the contrast in inner vs outer planet density due to?
- The contrast in density is due to differing chemical compositions, which are a function of the planets distance from the sun - Inner planets formed under hot conditions where many volatile elements were not stable → which is why their composition is mostly of refractory elements instead!
how does the density of elements change when ur on surface of earth vs inside? why?
- The effect of pressure on density leads to a gradual increase of density with depth for Earth's crust and mantle - As u go deeper in earth, more material is above u and putting pressure on u --> Pressure helps to increase density of core in tandem with change in composition from silicate to metal
how has crustal growth varied thru time?
- The rate of crustal growth through time is still not known. - One could argue the mass of continental crust has been virtually constant over time (curve E) because the rate of creation has been matched by the rate of destruction. This idea cannot be ruled out. - Studies of detrital zircons show that surviving crust has been produced in pulses, perhaps related to cycles of supercontinent construction (ex: Pangea) and breakup.
how can u determine velocity of galaxies? hb distance of galaxies?
- The velocity of galaxies can be determined from their red shift- they are all moving away from us - The distance of galaxies can be determined by standard candles (and galaxy size)
how often do meteorites hit the earth?
- Tons of micrometeorites strike the Earth each day - Objects with sizes greater than 1 km are considered to produce catastrophic effects because their impacts would be felt around the globe - ≥1 km meteorites strike the Earth relatively infrequently—a 1 km sized object strikes the Earth about once every million years, and 10 km sized objects about once every 100 million years.
how does valence work?
- Total valence of a molecule has to add to 0 - valence tells u how many electrons an atom needs to gain or lose to have a full outer shell - Make sure to take into account the NUMBER of each element as well as its charge
What is the solution to Olber's paradox?
- Universe is not infinite - Universe is not static but is expanding and began with the explosion of a cosmic 'egg' - Power of egg explosion prevents stars from collapsing to universe's center - This is not provable with physical evidence
details of parallax method of determining distance?
- Uses geometric techniques - Rock from shore example (using position A and B, baseline and angles) → u can use the same way to measure distance of earth from nearby stars (use position of earth in January and in June as positions A and B) - Baseline = diameter of earth's orbit around sun - Method is limited to small portion of objects in our galaxy (3 * 10^15 km away from us)
what are the regularities of the solar system?
- all planets lie close to the plane of the ecliptic - All planets rotate in the same direction around the sun but at diff rates - The planets are regularly spaced (Spacing of the planets as u move away from the sun is relatively consistent) - There are systematic differences in planetary size and density with distance from the sun - Meteorites and the sun have similar chemical compositions - Meteorites, Earth and Moon are all of the same age.
what are the 3 modes of radioactive decay?
- alpha emission - beta emission - electron capture
to be maintained far from equilibrium... examples of this?
- an external source of energy is necessary ex: sun --> maintained energy by nuclear fusion ex: earth --> maintained by energy from decay of radioactive elements and energy from the sun
why is it likely that earth melted?
- bc the moon did and they are nearest neighbors - Heat sources are greater on Earth than on the moon, heat losses are less, therefore Earth likely melted in the early part of its history.
how do ions differ in radii from neutrally charged atoms?
- cations lose an electron and have their electron clouds pulled in by the positively charged nucleus - anions gain electrons, causing their electron clouds to expand anions are big, cations are small
What is the asteroid belt?
- circulates btwn the orbits of mars and jupiter - About 100 billion asteroids are in this belt - asteroids are analagous to rocky inner planets - The asteroid belt is the 'resting ground' for planetesimals (aka "protoplanets") that were not accreted/incorporated into a larger planet → aka failed planets
how is pluto an anomaly?
- does not orbit in the same plane as the rest of the planets - does not vary systematically in planetary size and density the same way as the rest of the planets
how can u roughly divide the history of crater formation into 3 periods?
- large and small craters formed - small craters only formed (since large objects have been gotten rid of) - Very few craters formed
what is dark matter?
- makes up 27% of the universe - Primary candidate: new elementary particle that has not yet been discovered - In particular, weakly interacting massive particles (subatomic, electrically neutral) - Many experiments and approaches to detect dark matter, including with particle colliders, but none have been successful
define meteorite meteorite vs asteroid
- meteorite: piece of rock from outer space that strikes the surface of the Earth. - Meteorites may have originated from an asteroid - Asteroids are much larger than meteorites - Meteorite is like a piece that got ejected from the surface of asteroid - Made up of metals and rock materials, just like asteroids are
What are quarks?
- particles that make up protons and neutrons (nucleons) - each nucleon is composed of 3 quarks
what is heterogenous accretion? what would it require? what showed that this is not possible?
- planets accrete from solid objects in the solar nebula, so heterogeneous accretion of the core would require a period when all solid objects in the early inner solar system were metal, and all the silicates remained in the gas. - That would require that metals would be the first material to precipitate from the nebular gas, followed at lower temperatures by materials containing rock-building elements like Si, Al, Ca, Ti, etc. - Diff elements precipitate out of gases as a function of their temperatures → condensation sequence shows that Al, Ti and Ca precipitate out first before Fe, Ni → would not be possible for metals to accrete first → so this hypothesis can be refuted → the metal cores of planetary bodies must have formed by separation of metal from rock after accretion.
what is the evidence for the idea that meteorites landing on Earth contain remnants of the earliest solar system materials that came together to form the planets?
- presence of chondrules in "chondritic meteorites" → chemical characteristics of chondrules show that they are some of the oldest object - age dates
methods for detecting exoplanets
- radial velocity - transit - Gravitational Microlensing - Direct Imaging - Astrometry
what is notable about the cosmic abundance curve?
- saw toothed pattern - odd elements and odd particle-numbered nuclides have lower abundances than their even-numbered neighbors --> reflecting nuclear architecture for even numbers - elemental abundances drop off with incr atomic #
what are some notable features when u look at a graph of the relative abundance of nuclides in the sun?
- saw-toothed pattern - abundance peak at 56Fe (bc its so stable/high binding energy) - from 1-100 on x axis, nuclides w particle #'s divisible by 4 have abundances far above those of their neighbors --> this is bc of alpha processes - there are 2 magic numbers- neutron # 82 or neutron # 126: nuclear configurations involving this # are v stable bc they are less likely to capture passing neutrons during r-processes --> they are created in greater abundances and are two bumps in the graph
exoplanet spectroscopy
- spectroscopy itself: Interaction of light with different materials reflects atomic structure - Atmospheres, mainly, but surfaces will become more accessible and important as more planets are detected - Transiting planet atmospheres can be probed - Secondary eclipse can reveal reflection and thermal radiation directly from the planet
what are the 4 forces and where are they each important?
- strong force: impt in the nucleus - electromagnetic force: impt everywhere, acts over infinite distances - weak force: impt for nuclear particles - gravity: impt well beyond atomic scale, infinite distances/large masses needed
types of exoplanets
- terrestrial - neptune like - super earth - gas giants
what determines the rate of a planet's heat loss?
- the ratio of its surface area to its volume. - the larger the SAV ratio, the faster a planet cools bc there is more surface to escape from
how are mass and energy related?
- they are diff forms of the same thing (think of mass as a form of energy) - if there is a loss of mass in nuclear reactions, then energy is released and vice versa
evidence for big bang?
- velocity and distance correlate --> showing that all galaxies were at same place at same time - the omnipresent background radiation of the universe (blackbody radiation is leftover from the big bang) - The H/He ratio of universal matter (the observed ratio of the universe corresponds to physicits' calculation of what H/He proportions should have formed during Big Bang atomic reactions)
what is neutron capture? how is it diff from alpha processes? where does it take u in the chart of nuclides?
- way to create elements heavier than 56Fe - can occur if there is a source of neutrons - nucleus combining with free neutron - diff from exothermic alpha processes bc this rxn consumes energy (endothermic) - takes u to the RIGHT horizontally
after 10 half lives...
0.1% of parent remains
what is the martian sequence of events?
1. In Noachian Period, Mars was hit with both large and smaller impactors and thus uniformly covered with both large and small craters. 2. Later, large impactors were mostly 'used up', leaving mostly small impactors. 3. Volcanism resurfaced what we know as Hesperia but not Noachia. The fresh Hesperian surface accumulated only small craters, while the Noachian surface also accumulated more small craters but the large craters remained. 4. Major resurfacing from volcanism in the Amazonis after the end of the Hesperian Period to remove evidence of even very small craters
what are the 4 models for the future of the universe? which one is the best fit to supernovae data?
1. Recollapsing universe: rn we are expanding but expansion will someday halt and reverse 2. Critical universe: will not collapse, but will expand more slowly with time 3. Coasting universe: will expand forever with little slowdown 4. Accelerating universe: expansion will accelerate with time Best fit to our supernovae data is the accelerating universe model
how many Ma in 1 Ga?
1000
how do u determine the usefulness of a given isotope system? in terms of how old it can date objects
10x its half life
how does 14C dating work? whats the key assumption?
14N is in the atmosphere + combines with neutron to make 14C all 3 isotopes of C (12C 13C 14C) can combine w oxygen to be taken up by living things as CO2 14C is a radioactive isotope aka it is unstable so it wants to decay again to 14N All living systems that react with CO2 have an initial 14C/12C value that is determined by the 14C/12C of the atmosphere. --> Organic material that is no longer exchanging CO2 with the atmosphere (ex: dead tree) would then decay back to 14N and gradually have lower 14C/12C depending on time elapsed since isolation from the atmosphere KEY assumption: If there are no changes in the rate of cosmic ray production of 14C and no changes in the amount of 12CO2, then the atmosphere has constant 14C/12C over time → 14C dating requires the assumption that the initial condition was the same as today's atmosphere.
why is 56Fe significant? what is the switch that happens at 56Fe?
56Fe represents peak in nuclear binding energy (sum of proton mass + sum of neutron mass - mass of nucleus) so it is super stable switch from exothermic --> endothermic fusion process creating heavier mass now requires energy input
what ages is 14C dating useful for?
<50,000 years
what is the strong force and why is it impt?
>100x stronger than the electric force keeping protons apart --> Strong force holds the nucleus together and overpowers the electrostatic repulsion of protons Operates only over very small distances
what is a criticism (and response) of the giant impact hypothesis?
A criticism of the giant impact hypothesis is that it requires a unique event However, models show that giant impacts are likely in early solar system history, and that most of the planets probably ultimately accreted from large protoplanets impacting one another
What is an exoplanet?
A planet that orbits a star other than the Sun
as u go farther away from sun what happens to moon densities? what does this indicate?
As u go farther away from sun, moon densities decrease substantially → indicating that instead of being composed of rocks, moons are prob composed of ices
relationship btwn luminosity, apparent brightness and distance?
At a particular luminosity, the more distant an object is, the fainter its apparent brightness becomes bc the energy is dispersed over a larger area
how has the rate of universe expansion been changing? which forces influence this?
At first, gravity acted to slow down the rate of expansion Dark energy acts on galaxies now, causing expansion rate to increase the expansion rate has been speeding up in the last ∼6 billion years!
why didnt all the objects in the asteroid belt accrete to form a planet?
Because of the rapid formation, and massive size (mass) of Jupiter right next door to the belt
is there a center of the universe? why?
Because theBig Bang happened everywhere, all at once, there is no center of the universe
what type of decay happens when atom is too neutron rich
Beta decay: atom gains a proton but loses a neutron n --> e- + p+
how was 2H and He first created?
Big Bang produces neutrons, which undergo radioactive decay to protons + electrons Neutrons collide with protons to make 2H Other collisions lead to masses 3 and 4 (He isotopes)
what are possibilities for the ultimate fate of the universe? which is most likely?
Big crunch - assumes that the average density of the universe will be enough to stop its expansion and the universe will begin contracting ('recollapsing' universe) - Unlikely due to measured expansion of the universe Big freeze/heat death: MOST LIKELY - Continued expansion results in a universe that approaches absolute zero temperature - Supply of gas for star formation dwindles - Universe grows darker Big rip - Acceleration of the universe increases space between galaxies as Hubble Constant increases to infinity - All material objects disintegrate into unbound elementary particles - Universe ends as a singularity (region of space where density of matter becomes infinite)
how were astronomers able to estimate the relative abundances of the elements making up the atmospheres of neighboring stars?
By calibrating these absorption spectra with dark bands
what is the capture hypothesis and why doesn't it work?
Capture Hypothesis: The Earth gravitational field captures an already formed Moon (a small protoplanet) - not likely on dynamical grounds (because the moon's orbit is almost perfectly circular and almost all other moons are elliptical) - Doesn't explain moon's unique size and composition - Does not explain similarity to Earth's mantle
which methods use standard candles? which dont?
DO: Main sequence fitting Cepheid variable stars Distant standards (White Dwarf supernovae (SN1a) and others) DONT: Radar ranging Parallax/triangulation
how can cepheids in nearby galaxies be used as standard candles to measure distance?
Distances to nearby galaxies can be estimated by comparing the differences between the intensities of light received from these distant blinkers and the intensity of light received from one of its cousins in our own galaxy, whose distance had been determined by trigonometry ALSO Knowing the distances of these nearby galaxies, the astronomer could then determine their diameters
how are earth and mars' moon sizes?
Earth's moon is very large relative to its size Mars' two moons are very small
how has earth changed from 5.6 Bya to today?
Earth, 4.567 billion years ago: a homogeneous collection of rocky debris Earth, today: heterogeneous, stratified into layers (core, mantle, crust) with ingredients for life concentrated at the surface Earth has had same bulk composition throughout time, but differentiation has changed where certain elements reside in the Earth
what type of decay happens when atom is too proton rich
Electron capture: atoms loses a proton but gains a neutron e- + p+ --> n
what are volatile elements?
Elements that become liquid or gas at low temperature are called "volatile" elements → super low boiling points
formula for the energy of the photon so what kind of waves have high energies?
Energy of the photon = Planck's constant (h) x frequency High frequency (short wavelengths) waves have high energies
Eu pattern in diff parts of moon?
Eu is enriched in the highlands and depleted in the Mare basalts (complimentary)
why does it make sense that the core is made up of Fe if its density is so light? why is it ironic?
Even tho Fe is much lighter than what the core is at 1atm, it compresses so much under high pressure that its density goes up a lot The great pressures of Earth's interior increase the density of all substances. Iron at core pressures is a bit TOO dense → requires about 20% of a lighter element
what is the core composed of?
Fe and Ni
Three hypotheses for origin of the moon
Fission hypothesis: Moon 'thrown off' a rapidly rotating, young Earth in the beginning Capture Hypothesis: The Earth gravitational field captures an already formed Moon (a small protoplanet) Giant impact hypothesis: off-center impact between the newly formed Earth and a Mars-sized protoplanet
what is the fission hypothesis? pros/cons?
Fission hypothesis: Moon 'thrown off' a rapidly rotating, young Earth in the beginning Pros - Moon is composed of rocks from the Earth's mantle → they have the same composition so it would make sense that the moon flew off the earth - Explains iron depletion of moon → by the time the moon spun off the earth, the earth's core had already formed so all the siderophile elements went there Cons - Not clear why young Earth was spinning so rapidly or why moon wouldn't have formed earlier than it did - Theory requires young Earth spins with a ~2 hour day (not observed in our solar system) so is this fast spin even that plausible...
how do we get insight for galaxies at the largest distances from us?
For largest distances, insight comes from the apparent size of the galaxy because individual stars cannot be resolved
how is heat generated from nuclear fusion?
For nuclear fusion to occur there must be a release of E and this E release results in a reduction in mass → this lost mass reappears as heat
why do even elements have a larger # of isotopes than odd elements?
For odd numbered isotopes, there is no preference between odd-even and even-odd nucleon configurations so there is a single mass minimum. But for even numbered isotopes, movement along an isobar switches from odd-odd to even-even nucleon configurationsEven-Evens are preferred. So there can be two (or more) mass minima. --> So even numbers of protons can have both even-even and even-odd minima, leading to large numbers of isotopes for even elements.
why do elements with odd#s usually only have 1 isotope?
For odd numbered isotopes, there is no preference between odd-even and even-odd nucleon configurations so there is a single mass minimum. it depends on which elements on the associated isobar have the minimum mass.
how come cations and anions exist?
For some elements, having a filled shell structure is more important than charge balance, leading to the creation of ions (cations, anions)
what is the giant-impact hypothesis?
Giant impact hypothesis: off-center impact between the newly formed Earth and a Mars-sized protoplanet - oblique/angled impact - very energetic collision - vaporized the Earth's mantle and the impactor - vaporized material (which ended up forming the moon) will be iron depleted relative to Earth's composition (Earth's iron in core, formed before impact) - vaporized material settles into a disk about the Earth, and the Moon accretes very rapidly within disk
the big bang made...
H and He
what is the most effective means of converting mass into energy?
H burning
How come some elements are concentrated in crust and other in the core?
Has to do with the chemical affinities of the elements
What is Hubble's constant? how is related to age of universe?
Hubble constant represents the constant rate of cosmic expansion caused by the stretching of space-time itself v=H0L age of universe = 1/H0
what is the hubble parameter? why is it necessary?
Hubble constant represents the constant rate of cosmic expansion caused by the stretching of space-time itself --> the expansion rate is constant in all directions at any given time but this rate changes with time throughout the life of the universe When the Hubble Constant (Ho) is expressed as a function of cosmic time, H(t), it is known as the Hubble Parameter
structure of H and He atoms?
Hydrogen atom: simplest atom - Single electron cloud - 1 proton - no neutron Helium atom - 2 neutrons - 2 protons - 2 electrons - it's like 4H's - 2 electrons
what are the heat sources on earth?
Impacts Radioactive isotope decay Core formation (when Fe sinks)
what are the diff combos of tetrahedra?
Isolated tetrahedra - Olivine group: all O bond with other metals, like Fe and Mg (no Si-O-Si bonds) Single chains of tetrahedra - Pyroxene group: backbone is Si-O tetrahedra; each tetrahedra is joined to two others Double chains of tetrahedra - Amphibole group: two single tetrahedra chains join together - Holes in the middle → can take in a large variety of elements Sheets of tetrahedra - Mica group: silica tetrahedra create 2d sheets 3-D frameworks of tetrahedra - Feldspar group
What is about the Earth's moon that distinguished it from common moons in our solar system?
It is very large relative to its planet (Earth) Only large moon in inner solar system The Earth-Moon system is peculiar in many ways typically, the satellite / planet mass ratio is very small Hence, the Moon is remarkably 'heavy' for a satellite
where do comets come from?
Kuiper Belt and Oort Cloud
limits to reductionism?
Limits to reductionism - Despite its obvious successes, reductionism falls short when we try to calculate or understand many natural phenomena → very few natural phenomena can actually be calculated from the first principles - The real world is an open system, not an idealized one; and it changes with time --> natural systems' chemical and physical properties are not homogenous and are time-variable; energy and material constantly flow in/out - Some equations that govern real systems exhibit chaotic behavior, limiting long term predictions and certainty - The real world consists of "systems" not just objects - In principle, everything can be reduced to the smallest phenomena from which everything else derives but there is a gap between our practical experience of nature and the pure laws governing phenomena
why are mars' moons special?
Mars' moons (phobos and deimos) have retrograde orbits - Retrograde means it is spinning backwards relative to the planet - BUT our list of "solar system regularities" dictates that objects that formed contemporaneously in the solar system have similar orbits → SO Mars' moons were likely captured from neighboring asteroid belt
how do we measure isotopes?
Mass spectrometry: useful for measuring extremely small quantities of isotopes (present in parts-per-million [ppm] or parts-per-billion [ppb] range) These instruments generally are not great at measuring absolute concentrations of isotopes, but can measure isotope ratios very precisely.
how does melting in earth's interior typically take place?
Melting in Earth's interior often occurs because of a decrease in pressure not necessarily bc of a temperature increase
what are the 2 models for the timing of core formation? which one is correct and why?
Model 1: Earth accretes as a homogenous body (iron and silicate uniformly mixed) and stays that way for at least 50 Myr. → Core formation occurs later. - After 50 Myr, a significant amount of 182Hf should have decayed to 182W - so then when core formation occurs later, the 182W/184W of core and BSE should be equal (= chondritic value) Model 2: still homogeneous accretion BUT core formation occurs very early (during accretion, or at least within the first few million years of Earth's history). - if core formation occurs early, 182Hf decay to 182W is incomplete --> Hf is partitioned into BSE - later, the remaining 182Hf decays and since BSE has most of the earth's Hf it ends up with more 182E than the core (not = chondritic value) Model 2 reproduces the observed increase in 182W/184W of the BSE relative to chondrite meteorites.
where and when do molecules form?
Molecules form in interstellar clouds shortly after supernovas distribute the elements ex: silicate minerals and organic molecules are present in interstellar clouds
How is the moment of inertia related to earth's composition?
Moment of inertia: quantifies the distribution of mass of an object relative to an axis Earth is slightly ellipsoidal in shape/ an equatorial 'bulge' that is a result of its spin (radius in x axis direction is greater than radius in y axis direction) Size of bulge tells us how mass is distributed within Earth Of particular interest for planetary structure is the how the moment of inertia changes as one goes from a homogenous solid sphere with a uniform density to a sphere with higher density material at its core (like earth) Earth has a moment of inertia that is about 20% less than if it were a sphere of uniform density throughout its entire structure
most of our universe is made up of.... a sliver is made up of...
Most of our universe is made up of dark energy and dark matter, only a sliver (5%) of it is made up of ordinary matter Of that 5%, 4% is H and He
Radioactive decay equation
N = No * (e^-(lambda*t)) N = quantity of parent isotope No = initial concentration Lambda = decay constant OR D = Do + N(e^(lambda*t) -1)
What is a nebula?
Nebula is the product of supernovae explosion → body of interstellar material that has a lot of gas and dust
what is the prevailing hypothesis for the origin of the solar system?
Nebular hypothesis - Sun and all planets began as giant cloud of molecular gas/dust (aka nebula) - Gravitational force in the interior of nebula is attempting to collapse the cloud and countering the pressure/expansion force - Gravity overcomes internal expansion → collapse in center of nebula → accrete gas/dust into denser bodies and denser regions pull in more and more matter → conservation of angular momentum acts: collapsed nebula begins to rotate while there is increasing pressure in its interior → causes it to heat up - Most of material in collapsed nebula ends up in center to form the protosun - Rest of material flattens into elliptical disk around the sun --> Protoplanets form by accretion in this disk (gas and dust pulled together and coalesce into larger bodies)
what are pauling's rules?
Negatively charged oxygen ions are arranged in polyhedra around positively charged metal ions The number of oxygen atoms in the polyhedra controls the size of interior spaces where the cation resides --> so the space between the oxygen atoms determines which metal can fit
how come stable nuclei have roughly same amounts of protons and neutrons?
Neutrons and protons are convertible → if a nucleus has too many neutrons, they decay to protons and vice versa n ←→ p+ + e- Can go in both directions to obtain minimum mass This balance reaction causes stable nuclei to have roughly coequal amounts of both particles
Since all galaxies are moving away from the Milky Way, does this mean we are at the center of the Universe? explain w analogy
No, because what Hubble's Law really describes is an expansion of space in such a manner that the shape or configuration of space remains the same. the space btwn stars and galaxies is increasing but the basic configuration remains the same --> analogy: rising loaf of bread. raisin positions/orientations stay the same but their separation increases
do galaxies increase in size?
No. While the space btwn galaxies incr, galaxies themselves do not incr in size bc gravity holds them together
oceanic vs continental crust
Oceanic - mostly mafic rocks, like basalt - higher in Fe, Mg, Ca - contains denser elements so it denser overall than continental crust Continental - mostly more felsic rocks like andesite and granite - Contain a lot of potassium and sodium, lighter in color - Higher in silica than oceanic - Buoyant, almost floats on top of mantle
How does oceanic crust form? How does continental crust form?
Oceanic crust forms from partial melts of the mantle → these have a different composition than the mantle itself and the melts are less dense, which causes them to rise Generating continental crust requires many partial melting and subsequent cooling steps; these types of rocks cannot be produced by melting of the mantle. "The end point of many partial melting processes"
how do the age of our planets compare to those in other solar systems?
Planets in other solar system may be older, younger or same age as planets in our solar system
some moons have no craters. what does this suggest?
Others have no craters at all, suggesting an actively changing surface that is continuously regenerated. (ex: on IO jupiter moon, the many volcanoes can erupt and repave the crater impacts. Ex: on europa jupiter moon, movement of ice regenerates the surface)
How do the outer and inner core differ?
Outer core = liquid, inner core = crystalline still hot topic of when exactly the inner core crystallized out from liquid
What are Steno's Laws?
Principle of Superposition - Younger rocks develop on top of older rocks Principle of Original Horizontality - Rocks are originally deposited in nice horizontal layers - Plate tectonics can cause rocks to fold
what drives radioactive decay? when will A-->B happen?
Radioactive decay occurs if there is some other reachable state that would have a lower mass per # of nucleons (proton and neutrons). This lower mass state is energetically preferred. So if A → B and B has a lower mass than A, radioactive decay will happen
what is red shift?
Red shift states that as a star moves away from an observer on Earth, the wavelength of the light emitted from the star will increase and the wave will be stretched Red shifting causes all the black bands to be shifted the same amount towards the red end
when did the core form in relation to Hf isotope decay?
SO The core must have formed before the completion of Hf isotope decay. less than 100 mya after earth accreted
what are the 2 approaches to understanding systems? what is the diff btwn them?
Reductionism - Understanding comes from our ability to "reduce" the whole to the fundamental laws of physics from which all phenomena arise - Phenomena calculated at the most fundamental level can, at least in theory, explain and predict the whole - Once the laws are understood, everything can be accurately described and predicted thru calculation → this is often understood as the fundamental scientific approach - An aspect of this approach is the belief that understanding complex phenomena comes from breaking them down to their simplest parts - Ex: if we wish to accurately describe a crystal or a gas, the behavior of individual atoms provides the ultimate answer "Systems" thinking - The whole is greater than the sum of the parts - Relationships between those parts matter - If you break it down, you lose essential aspects that are characteristic only of the whole - Opposing view to reductionism
Where did all the additional dust and gas go aka how did the nebula get cleared?
Remains of the protostellar nebula were cleared away by: - Radiation pressure from the Sun - Solar wind - Sweep-up of space debris by planets - Ejection by close encounters with planets
what is the nucleus band of stability? what happens if ur outside the band?what principle does it build off?
Reps the most favorable ratio of protons to ratio. Band of stability is when protons and neutrons are in balance and so no loss of mass by decay is possible all nuclei outside the band are radioactive and decay to the band based off the principle that convertibility occurs: n ←→ p+ + e-
what are the 3 rules pertaining to electron configuration?
Rule 1: Electrons occupy the lowest energy orbitals available. This is complicated by "crossover" of energies above the 3p level. Rule 2: Each orbital can hold only two electrons, which must be of opposite spin Rule 3: Two or more orbitals with the same energy are each half-filled by one electron before any one orbital is completely filled by addition of the second electron.
define: Silicates Carbonates Oxides Sulfides Sulfates Halides
Silicates - Si, O combined with other cations Carbonates - Ca, Mg and CO3 Oxides - O2− and metallic cations Sulfides - S2− and metallic cations Sulfates - (SO4)2− & metallic cations Halides- F- , Cl- and other halogens
what is the black-line bar code in absorption spectra and why is it important?
Since all stars contain at least some of the same elements, the characteristic black lines become a fixed "bar code", with spacings and relative intensities controlled by fundamental characteristics of atoms When astronomers looked at very distant objects, they found that the characteristic "bar code" shifted with respect to the rainbow background → The spacing and relative intensity of lines remained the same
stars vs nebula
Stars - High temps (millions of degrees) - Releasing nuclei but no electrons are bound to the nucleus (plasma) - Nuclear changes (physics) Interstellar clouds/nebula: all material btwn stars - Lower temperatures (thousands of degrees) - Electrons are bound to nucleus (since things are cooling down, can create more stable atoms) - Electron sharing creates molecules (chemistry)
what determines the length of time it takes an element to reach its steady state?
Steady state is governed by half life → elements w short half lives will approach their steady state condition faster than those w longer half lives
what is the r-process?
Supernovas create a neutron "machine-gun" that makes neutron-rich isotopes. These then decay to create stable isotopes on the lower right hand side of the band of stability temporarily displaces the band of stability far to the right. when neutron flux dissipates, the unstable nuclei returns to the band by beta decay
which planet is an exception to the temp-distance from sun relationship and how?
Temperature of the planet usually correlates with the distance from sun - Except venus! This is farther from sun than mercury but it is HOTTER - this is bc venus' composition fenables huge greenhouse gas emission → keeps the planet hot AF
relationship btwn star size, gravity and heat?
The bigger the star, the stronger the gravity, and the more heat is required (from nuclear fusion) to keep it from contracting
What are the dark bands in the solar spectrum?
The dark bands were later found to be produced by the absorption of certain frequencies of light by the element-containing halo of gas surrounding the star that is producing the light. While transparent to some frequencies of light, the excitation of elements in the gas absorbs other frequencies so that specific wavelengths of light do not get through.
define asteroids vs. comets
The main difference between asteroids and comets is their composition - asteroids are made up of metals and rocky material - comets are made up of ice, dust and little bit rocky material.
What is Hubble's Law?
The faster a galaxy is moving, the farther away it is.
what other things could the giant-impact hypothesis explain?
The giant impactor hypothesis may not only explain the origin of the Moon → it may be responsible for the Earth's (24 hr) rather rapid spin AND the Earth's obliquity to the ecliptic (tilt of the spin axis with respect to its orbit about the Sun)
relationship btwn BBR and temp of object? how can this be seen?
The intensity and frequency of the blackbody radiation increase with increasing temp So as objects grow hotter, they radiate energy dominated by shorter wavelengths, causing the object to change color
relationship btwn distance and red shift?
The more rapidly a galaxy is retreating from us, the larger the shift of its light toward the red Galaxies that exhibit the greatest red shift are also the farthest away
how is the x-axis wavelength location of the intensity peak of a star (on a BBR graph) related to its temperature?
The peak is highly dependent on the temp of the star → higher the temp? Shorter the wavelength where the peak is radiated so like a star that most intensely radiates purple wavelength of light is hotter than one that most intensely radiates red wavelength of light
what is dispersion?
The separation of white light into its constituent wavelengths
what could explain large size of mercury's core?
Thin Mercurian mantle Ni-Fe core accounts for 75% of radius Impact event may have removed outer crust
what are refractory elements?
Those stable as solids to very high temperatures are called "refractory" elements → super high boiling points
V high temp objects emit blackbody radiation in ____ part of spectrum V low temp objects emit blackbody radiation in ____ part of spectrum
V high temp objects emit blackbody radiation in UV part of spectrum V low temp objects emit blackbody radiation in IR part of spectrum At the right temperatures, some of the radiation enters the visible part of the spectrum
what did newton see when he observed the solar spectrum? what happened later?
When Newton described the laws of refraction and dispersion in optics, and observed the solar spectrum, all he could see was a continuous band of colors In 1802, William Wollaston built an improved spectrometer that included a lens to focus the Sun's spectrum on a screen. With this device, Wollaston saw that the colors were not spread out uniformly, but instead, some ranges of color were missing, appearing as dark bands in the solar spectrum.
what is the composition of the lunar crust?
When u look at the surface, some areas are light grey and some splotches are dark grey - Highland Crust: light grey, composed of the mineral Plagioclase (d=2.7 g/cm3) - Maria: Giant Lava flows → eruption causes dark grey spots
which planets have moons?
all 4 outer planets: jupiter, saturn, uranus, neptune earth and mars
All EM waves... so their frequency depends on their ...
all EM waves travel at the speed of light they have a frequency that depends on their wavelength—that is, long wavelengths travel at the same speed as short ones, so the time for a complete wave (its frequency) is longer
what type of decay happens when atom is too big
alpha decay: loses 2 protons and 2 neutrons
what is a standard candle? why is it impt
an object of known intrinsic luminosity W the exception of radar and parallax, all methods to measure distance rely on this concept
How do ions arrange themselves into minerals?
anions are generally larger than cations --> most of the volume of mineral is made up of anions Structure of mineral will be determined largely by how the anions are arranged and how the cations fit between them.
why does a flame change from red to blue in color?
as it grows hotter, the wavelength gets shorter --> blue has shorter wavelength than red
atomic mass vs atomic number
atomic mass (A)= protons (Z) + neutrons (may have a decimal) atomic number (Z)= # of protons (also electrons)
all main sequence stars...
burn H
how come we can see evidence of differentiation events on the moon but not the earth?
bc moons surface is not being regenerated
how come big bang did not allow for collision that lead to masses 5-8? what does this mean about the proportions of elements produced by big bang?
bc only rare reactions can "jump" over mass 5 to yield masses 6, 7 or 8 these rxns rare enough that the # of nuclei formed w mass > 4He was insignificant Big bang produces 1 He for every 10 H and negligible amounts of Li, Be and B
why are supernovae important for creating elements heavier than 56Fe?
bc supernovae release a lot of free neutrons --> in a closed environ, these neutrons will enter a nucleus long before they can decay to a proton + electron
why can't elements heavier than Fe be made by alpha addition process?
bc the repulsion btwn large, positively-charged nuclei and alpha particles is too strong
why do super heavy elements have such short half lives?
bc we are packing so many protons together that don't wanna be together
what are the modes of decay? what are their directions of movement on chart of nuclides?
beta decay - atom gains a proton but loses a neutron n --> e- + p+ - happens when atom is too neutron rich and unstable - moves upward left diagonally electron capture - atoms loses a proton but gains a neutron e- + p+ --> n - happens when atom is too proton rich and unstable - moves downward right diagonally alpha decay - happens when atom is too big - atoms loses two protons and two neutrons - moves downward left diagonally
blue shift is ___ red shift is ___
blue shift is negative red shift is positive when given the key value, subtract IT from the observed values
What can u tell about the solar gas-halo by looking at the wavelengths/intensity emitted?
by looking at the wavelengths emitted, you can tell what elements are present --> Each element has electrons that can move from one energy state to another. The jumps in energy either absorb or emit light of a very specific wavelength. From the intensity of the light you can say something about how much of the element is present
how does the silicate earth differentiate into crust and mantle?
by partial melting
how do stars form? how do gravity and heat interact within?
contraction of massive clouds of gas, driven by gravity As the cloud contracts → all of its E is confined to a smaller volume and it heats up → keeps contracting/heating up until some force operates to offset the gravitational contraction → that force is the heat generated by nuclear fusion
how does alpha decay change atomic mass and atomic #?
decreases mass by 4 decreases # by 2
siderophile elements are concentrated in...
earth's core
magmaphile elements are concentrated in...
earth's crust
lithophile elements are concentrated in...
earth's mantle
what are the two hypotheses for how the earth's core formed?
heterogeneous accretion - earth assembled in step-wise fashion - Fe and Ni core formed first --> then the Mg, Si, O layer accreted after homogenous accretion - Earth initially assembled from silicate and iron particles uniformly mixed → later heat-up causes catastrophic differentiation by core in-fall - Iron sinks out bc of the diff in density
what are the capture and close encounter hypotheses?
hypotheses for solar system formation - Capture: Planets wandering through space were captured by the Sun's gravitational pull - Close Encounter: The planets formed from debris torn off from the Sun by a close encounter with another star. these do NOT work
What are the outer planets made of? what are the densities?
ice and gas density: 0.6-1.6 g/cc
if we know an object's __ and __, we can find its distance
if we know an objects luminosity and measure its apparent brightness, we can find its distance
what must happen in star interior before nucleosynthesis can begin?
ignition temperature must be reached
what is the alpha addition? what is the limit to this?
in a massive red giant, successively heavier elements can be synthesized by the addition of alpha particles (He nuclei) to C it can continue up to 56Ni --> which decays to 56Fe. mass loss thru fusion stops at 56Fe
when do cepheids not work as a standard candle? what can be used instead and why?
in the cases where individual stars in very far away galaxies cannot be resolved (with even the biggest or most advanced telescope) so need a new standard candle --> type 1a supernovae bc they can be detected from very far away in space and time
how does density vary within earths layers?
inner core is most dense --> outer core --> mantle --> crust
what are the phases of earth's layers?
inner core: crystal outer core: liquid mantle: solid crust: solid
inner vs outer planets? what are they and how do they vary?
inner: mercury, venus, earth, mars outer: jupiter, saturn, uranus, neptune Inner rocky planets are much more dense than outer gaseous giant planets → so outer planets are made up of mostly lighter molecules then (bc their size is so much bigger but density is smaller)
diff btwn intrinsic luminosity and apparent brightness?
intrinsic luminosity - measures total e output by star - distance independent apparent brightness - measures how bright a star appears to be from a distance - distance dependent
equilibrium applies to...
isolated systems that move toward and maintain a minimum energy state
where are the decays located on chart of nuclides relative to the band of stability?
isotopes in the top left region above the band are too proton rich and decay by electron capture to a stable isotope on the band of stability isotopes in bottom right region below the band are too neutron rich and decay by beta decay to stable isotope on band of stability
Where do moons of the outer planets come from?
kuiper belt
___ pressure or ___ temp can often have similar effects on state of matter
lowering pressure or raising temp
Only certain combinations of neutrons and protons form stable units --> what combo is most stable?
lowest mass nucleus
compare age of mare basalts and highlands anorthositic crust
lunar basalts are much younger
what is the mass defect?
mass defect: The mass of a nucleus is less than the sum of the protons and neutrons would have if they were free when nucleons bind together to form nucleus, they release energy and lose mass
why does He weigh less than we might expect (4H's)?
mass defect: The mass of a nucleus is less than the sum of the protons and neutrons would have if they were free when nucleons bind together to form nucleus, they release energy and lose mass
the mass of the atom mostly in ____ the size of atom determined by ___
mass is mostly in nucleus size is determined by electron cloud
how old is oceanic crust? how is it generated/destroyed?
mean age is 60Ma it is generated at ocean ridges and subducted at convergent plate boundaries
molecules are the building blocks of....
minerals
what are the 2 waves caused by earthquakes?
p- wave (or primary wave): compressional wave, transverses in direction of motion, higher V than s wave s-wave (or shear wave): transverses perpendicular to direction of motion
continents are mostly...
quartz and other light minerals like feldspar
how does red shift explain olber's paradox?
red shift is tied to an expanding universe The expansion of space over time causes the energy of emitted light to be reduced via redshift, eventually to frequencies humans cannot visually observe
what are the inner planets made of? elements? what are the densities?
rock and metal primarily O, Mg, Si, Fe density: 4-5g/cc
what is the s-process?
sequential neutron absorption followed by beta decay: target nuclei absorb successive neutrons until a very short-lived nucleus decays before another neutron can be absorbed In stellar interiors neutrons and protons can be added slowly. They migrate slowly along the band of stability, decaying before another nucleon is added.
how does atom size vary in periodic table?
size Increases with increasing number of shells (down the rows of the periodic table) size decreases with more positive charge in nucleus (across the columns of the periodic table
what are minerals?
solid, naturally occurring, inorganic compounds with homogeneous physical properties, symmetrical structure and a chemical composition that can be written as a formula (like SiO2 or Mg2SiO4)
what allows protons to be so close to each other in the nucleus? what abt e's?
strong force overpower repulsion of protons Since the cloud is so much bigger than the nucleus, the e's can avoid each other pretty well
what is nuclear binding energy? what does it say about nucleus stability?
sum of proton mass + sum of neutron mass - mass of nucleus the energy released when a nucleus is formed from nucleons the higher the binding energy, the more stable the nucleus
how do the elements created inside stars get dispersed to the universe?
supernovae!
minerals must be ___ to grow
symmetrical
define EM waves
synchronized oscillation of coupled electric + magnetic waves emitted by charged particles
tetrahedron vs octahedron? # faces # edges # corners # oxygens
tetrahedron # faces: 4 # edges: 6 # corners: 4 # oxygens: 4 octahedron # faces: 8 # edges: 12 # corners: 6 # oxygens: 6
what is nucleosynthesis?
the cosmic formation of atoms more complex than the hydrogen atom.
What is Olber's paradox? What are some alternative options and why do they not work?
the darkness of the night sky conflicts with the assumption of an infinite static universe bc any line of sight from earth should end at the surface of a star other options: 1) the universe is not infinite— in a finite universe, we would look between the stars and see voids --> BUT in a universe of finite extent there would be nothing to hold the stars apart because matter would be drawn to the center of the universe - clouds of non luminous matter float in the voids between stars and intercept light --> BUT this would impact light of stars at intermediate distances—we would see them as 'headlights through the fog
what happens to the alpha particle byproduct of alpha decay?
the expelled alpha particle will acquire 2 electrons to become a helium atom
the ___ a star is, the __ the red shift is
the faster the star or galaxy is moving away, the greater the red shift is.
since the age of oldest rock does not align with the age of earth, how can we find out wht happened in first 600 Ma?
the moon gives us a record of early solar sys history not available from rocks on earth Since moon is our nearest neighbor we can assume that what happened on moon happened on early earth
the most common, important molecules for earth make use of...
the most abundant elements: Fe, Mg, Si, O, Ca, Al, C, H, O
the larger a crater is...
the older it probably is
the more craters appear on a surface...
the older that surface is
Doppler/red shift tells us ONLY about...
the part of an object's motion toward or away from us
feedback occurs when...
the system is maintained at steady state because the response 'feeds back' to control the input
molecules are most stable when....
their outermost shell is full
in terms of Hf-W system, if the core formed 100mya or more after earth accreted...
then all of the 182Hf would have decayed into 182W before core formation and the tungsten isotope ratio of the late-forming core would be the same as bulk silicate earth (ratio when only considering the mantle and crust)
what are the 2 types of electromagnetic spectra?
thermal/blackbody radiation spectrum - aka continuous spectrum - Intensity and position of thermal radiation spectrum can be used to determine stellar temps absorption spectrum - Cooler atoms in the outer atmosphere of the star absorb light at the specific wavelengths corresponding to electronic transitions within those atoms - Details of the spectrum can be used to determine the composition of stars
why are metals so conductive?
they cannot fill their shells using covalent or ionic bonding electrons from the incomplete shell move freely
type 1a supernova will always...
type 1a supernovae will always be about the same size so will have the same intrinsic luminosity
What is a Cepheid variable star? why are they important?
type of star whose luminosity/energy output varies in a periodic way (lighthouse analogy) cepheids in other nearby galaxies can be used as standard candles
the total heat contained in a planet depends upon its...
volume
frequency vs period vs wavelength? relationships?
wavelength: distance btwn wave crests/troughs period (T): time it takes for a full wave cycle frequency: # of cycles per second T= 1/f
the behavior of electron shells controls...
what molecules can form
Chemical affinities of the elements determines...
where they reside in the earth. the distribution of elements among earth's layers
how long ago did element production begin in relation to when the solar system came into being?
~10 billion yrs before
