week one

properties of material objects

size, shape, color, mass, composition, living or nonliving, natural or artificial, mobile or stationary, temperature, age, history, intended purpose

why is the sun a white star

light from the sun peaks in the green (center of the visible spectrum)

cosmic rays

extremely high energy protons and atomic nuclei originating from outside the solar system (may be from supernovae or large black holes, may produce showers of secondary particles in the earth’s atmosphere)

inner solar system

small rocky planets

outer solar system

giant gas planets, large gas/ice planets

inner planets

mercury, venus, earth, mars -- solid bodies made of silicate, metal, and sulfide

astronomical unit (au)

mean distance between the earth and the sun

the planets \[ \] around the sun and \[ \] around their axes

revolve, rotate

aphelion

farthest point from the sun in the orbit

perihelion

nearest point to the sun in the prbit

semi-major axis

half of the long axis of an ellipse

eccentricity

how flat something is (e = 1 is a straight line)

bode’s law

method of estimating a planet’s mean distance from the sun

bode’s law procedure

start with 0, 3, double each number after 3, add 4 to each number, then divide by 10

order of planets

mercury → venus → earth → mars →jupiter → saturn → uranus → neptune

a planet

* must be in orbit around a star
* a solid body with sufficient gravity to have molded itself into a roughly spherical shape
* must be the dominant body in its orbit

a star

* a body of sufficient mass for fusion reactions in its core to transform hydrogen into helium.
* could be a single body or part of a multiple star system
* may (or may not) have an associated planetary system

age of the universe

\~13.8 billion years

cluster which contains the milky way

the virgo cluster

laniakea

a supersized supercluster consisting of 100,00 large galaxies arranged in filamentary streams flowing through space (*immeasurable heaven* - hawaiian)

the “local group”

several small satellite galaxies that accompany the milky way

what would happen if andromeda and the milky way collided

two billion years after the collision, the combined giant galaxy will merge and form a structure resembling a giant elliptical galaxy, this mixing of interstellar gas will induce a new burst of star formation

galactic year

how often the sun orbits the center of the milky way (once every 230 million years)

barred spiral galaxy

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elliptical galaxy

spiral galaxy

stephan’s quintet

five galaxies in the constellation pegasus that form a cluster of gravitationally interacting galaxies

when did the solar system form

4,567,000,000 (4.567 billion) years ago

observable universe

spherical volume of space, centered on earth, from which we could in principle receive photons (diameter estimated to be 93 billion light years)

the multiverse

a model in which there are many, possibly infinite, universes that constitute everything that exists

zenith

point directly above (in relation to an individual)

nadir

point directly below (in relation to an individual)

sun’s rays in winter vs summer

sun’s rays are more oblique/spread out over a larger area in winter, fewer photons when compared to the more direct rays over smaller areas in summer

star trails

when a fixed camera is pointed at the north celestial pole and able to capture the stars seemingly making counterclockwise circles as the earth rotates

tropics

* tropic of cancer - north of the equator
* tropic of capricorn - south of the equator

heliocentric model

the earth and other planets revolve around the sun

aristarchus of samos

concluded that the earth was a sphere because it cast a curved shadow on the moon during lunar eclipses

retrograde motion

* when a planet appears to move backwards relative to the background stars from the pov of an earth-bound observer
* outer (superior) planets → when the earth overtakes the planet
* inner (inferior) planets → when they overtake the earth

kepler’s three laws of planetary motion

1. the orbit of a planet is an ellipse with the sun at one focus
2. the line joining a planet to the sun sweeps out equal areas in equal times
3. the square of a planet’s orbital period is proportional to the cube of its mean distance to the sun (P² = a³)

copernicus

heliocentric system and retrograde motion

parallax

the difference in direction of a celestial object as seen by an observer from two widely separated points

tycho brahe

discovery of the supernovia in the constellation cassiopeia, showed that the heavens were not unchanging

kepler

introduced physics into astronomy

newton

new laws of motion for objects on earth and in the heavens, demonstrated that laws of gravity applied everywhere

laws of motion

1. objects in motion stay in motion unless an external force is applied
2. F (applied force) = m (mass) • a (acceleration)

laws of gravitation

1. every object with mass attracts every other objects with mass
2. the force between two objects is proportional to the product of their masses
3. the force of gravity decreases as the quare of the distance between the centers of the object increases

the near side of the moon

the same face that always points towards earth

phases of the moon

new moon → first quarter → full moon → last quarter

eclipse of the sun

moon’s shadow is on the earth

eclipse of the moon

earth’s shadow is on the moon

total solar eclipses

occur at new moon, when the moon is near perigee (closest point to earth)

annular eclipse

occurs when the moon is near apogee (farthest point from earth)

why might the moon turn red

some light from the sun passes towards the earth’s atmosphere and is bent towards the moon. other colors are blocked and scattered by the atmosphere, but red makes it through more easily

inclinations between 0 and 90

direct orbits

inclinations between 90 and 180

retrograde orbits

what causes the diversity of rotational periods and inclinations of equators to the ecliptic>

giant impacts and tides

ocean bulge

caused because the moon is pulling on the oceans more strongly on side facing the moon, and because the moon is pulling the earth more strongly on the far side

spring tides

moon and sun are aligned, occur during the full moon and the new moon

neap tides

moon and sun are perpendicular, occur during quarter moons

atoms

tiny nuclei surrounded by an electronic shell \~10,000 larger

atomic number

positive charge of a nucleus, equal to the number of protons

neutral atom

equal number of electrons and protons

elements

atoms with different atomic numbers

ions

atoms with wither more or fewer electrons than neutral atoms

anions

negatively charged ions with more electrons

cations

positively charged ions with fewer electrons

neutrons

* subatomic particles found in the nucleus
* same mass as protons but have no charge
* found in all atoms except common H

atomic weight of an atom

number of neutrons + number of protons (electrons weigh very little)

neutron decay

a free neutron decays in 15 min into a proton (+1 charge) and an electron (-1 charge)

neutrino

tiny particle with no charge and very little mass produced as a free neutron decays

quarks

elementary particles

up quark and down quark

* combine to form protons and neutrons
* fractional charges (up quark = 2/3, down quark = -1/3)
* proton = 2/3 + 2/3 - 1/3
* neutron = 2/3 - 1/3 - 1/3

normal matter

consists mainly of up quarks, down quarks, electrons, and photons

photons

particles that carry momentum and energy that are affected by gravity

isotopes

atoms with the same number of protons but different numbers of neutrons (different atomic weights but same element)

half-life

the time it takes for half the atoms of a radioactive element to decay

compounds

elements that are chemically bound together simplest unit of a compound is a molecule)

the periodic table

* elements are grouped based on their chemical properties
* elements in the same column have the same amount of electrons in their outermost orbitals
* upper right = gases
* lower left and center = solid forms

elemental abundance

H is the most abundant, followed by He. abundances tend to decrease with increasing atomic numbers

meteoritic abundances

only elements able to form solids in the nebula condensed to form chondritic meteorites (building blocks of asteroids and planets )

most abundant elements in the earth

silicate rock and metallic iron (Fe, O, Si, Mg, Ni, S, Ca, Al, Na)

why outer planets have low densities

contain mostly H, He, and ices

as temperature increases

refractory (silicates) and density increases, volatiles decrease

rare earth elements

* also lanthanides
* tend to partition into silicate materials
* most are trivalent (+3 charge)

lithophile

elements that preferentially partition into silicate minerals

chalcophile

elements that partition into sulfides

siderophile

elements that form metals

atmophile

elements that form gases

refractory

elements that melt or vaporize at high temperatures

volatile

elements that melt or vaporize at low temperatures

flat pattern

all elements behaved as a group during geochemical processing

fractioned

some elements were removed or added during processing

to determine the geological history of the earth, mars, the moon, and asteroids

use chemical analyses of minerals and rocks coupled with the ages of these samples

molecular hydrogen

a molecule consisting of two hydrogen atoms

metallic hydrogen

forms at very high pressures, likely exists as a liquid and is an electrical conductor

sublimation

transition of a substance directly from a solid to the gas without passing the liquid state

crystallization

* process of forming solid crystals from a liquid
* nucleation - the molecules begin to form clusters in the liquid
* when nuclei reach a critical size, the atoms arrange themselves into an orderly manner

fractional crystalization

* precipitation and segregation of certain minerals from the parent liquid (changing the liquid’s composition)


* the next solid to form is crystallizing from a liquid of different composition

second law of thermodynamics

the state of entropy of the entire universe, as an isolated system, will always increase over time

conduction

process by which heat energy is transmitted through collisions between neighboring molecules