final summary slides

what determines a moon’s level of geological activity?

moon’s size and proximity to the planet

why are jupiter’s gailean moons so geologically active

tidal heating drives geological activity leading to lo’s volcanoes and ice geology on other moons

what is special about titan

the only moon in our solar system with a thick atmosphere

why are small icy moons more geologically active than small rocky planets

ice melts and deforms at lower temperature enabling tidal heating to drive activity

why do saturn’s rings disappear?

they can become very thin making them difficult to see; earth orbits through the plane of rings every 15 years

what are saturn’s rings like?

extremely thin and made up of countless individual ice particles

how do other jovian ring systems compare to saturn’s

other jovian planets have much fainter ring systems with smaller, darker, less numerous particles

why do the jovian planets have rings

ring particles are probably debris from moons

why is it useful for an asteroid to have a moon?

its orbit around the asteroid tells us the total mass of the asteroid and its moon

how can we measure the shape of an asteroid?

radar and waiting for the asteroid to cover a background star: occulation

which explanation for the asteroid belt seems the most plausible

the belt is where all the asteroids happened to survive

does the earth produce meteorites on near by SS bodies?

yes, if there is a large enough impact

how long can comet tails be?

as long as the earth-sun distance

what are comets like

dirty snowballs

where are comets located

far from the sun

what happens when a comet nears the sun

when the nucleus of the comet heats up, it grows a tail

where do comets come from in the plane of solar system

kuiper belt, some from oort cloud

how is human activity changing our planet?

destruction of ozone, high rate of extinction, global warming from production of greenhouse gases

how would the apparent brightness of alpha centauri change if it were three times farther away?

it would only be 1/9 as bright

how do we measure stellar luminosity?

if we measure a star’s apparent brightness and distance, we can compute its luminosity wtih the inverse square law for light

what does parallax tell us

distances to nearest stars

how do we measure stellar temperatures

a star’s color and spectral type

how do we measure stellar mass?

newton’s version of kepler’s third law tells us the total mass of a binary star system, if we can measure the orbital period and the average orbital separation of the system

orbital period symbol in newton’s version of kepler’s third law

p

average orbital separation symbol in newton’s version of kepler’s third law

a

hertzsprung-russell diagram

plots the stellar luminosity of stars versus surface temperature (or color or spectral type)

what kind of stars fall on the main sequence of an H-R diagram

normal stars that fuse H to He in their cores

what determines a star’s position on H-R diagram’s main sequence

star’s mass; high-mass means luminous and blue, while low-mass means faint and red

giants and supergiants

what stars become after core hydrogen burning is exhausted

what do most stars become after fusion has ceased

tiny white dwarfs

why do the properties of some stars vary?

some stars fail to achieve balance between power generated in the core and power radiated from the surface

open cluster

loosely packed star clusters containing a few thousand stars

globular clusters

densely packed clusters containing hundreds of thousands of stars

how do we measure the age of a star cluster

roughly equals the life expectancy of its most massive stars still on the main sequence

neutron star

ball of neutrons left over from a massive star supernova and supported by neutron degeneracy pressure

how were neutron stars discovered

beams of radiation from a rotating neutron star sweep through space like lighthouse beams, making them appear to pulse

what can happen to a neutron star in a close binary system

mass transferred to the neutron star spins up and hten accretion disk around the neutron star can become hot enough to produce x-rays, making the system an x-ray binary

what happens in an x-ray binary system

sudden fusion events periodically occur on the surface of an accreting neutron star, producing x-ray bursts

doppler effect

blueshift objects are moving towards us; redshift objects are moving away from us; the width of an object’s spectral lines cna tell us how fast it is rotating

radial velocity method yielded…

~800 exoplanets

what do we know of leverrier

predicted the position of neptune

how would you discover vulcan

visit total solar eclipses, look at the calculated position then set up solar observatory, continuously monitoring the sun and wait for transits of vulcan

how many planets have been discovered by microlensing?

200

microlensing planets

looking for planets you can’t see around stars you can’t see

what does microlensing use?

exploits the deflection and amplification of light by mass

microlensing limitations

single measurement epoch, slim chance for detection, short-lived events, planets are far, cannot be studied in detail

microlensing strengths

signal magnitude is independent of planet mass; duration depends on mass, small mass planets have rare and brief signals; sensitive to large orbital separations and low mass planets

what can we measure for a transiting exoplanet

P period, and simple “observables” — depth, duration, ingress-duration

what do we typically know of transiting planets

their mass and radius

what are jupiter and saturn primarily composed of

H and He gaswh

what are uranus and neptune primarily composed of

H compounds (ice)

what are jovian planets like on the inside

layered interiors with high pressure and cores made of rock, metals, and hydrogen compounds

what can high pressure in jupiter and saturn produce

metallic hydrogen

what is the weather like on jovian planets

multiple cloud layers determine the color but all have strong storms and winds

what jovian planet has the largest magnetosphere

jupiter

if the earth didn’t have an atmosphere, what would happen to its surface temperature

it would go down a lot (more than 10C)

why is there sodium in the mesosphere?

meteors burn and produce sodium

what kind of clouds are in the mesosphere?

noctilucent clouds

why is the sky blue

air molecules scatter blue light more than red

why do atmospheric properties vary with altitude

depend on how atmospheric gases interact with sunlight at different altitudes

what creates wind and weather

atmospheric heating, spin of planet, and coriolis effectc

coriolis effect

conservation of angular momentum causes ball’s apparent path on a spinning platform to change direction; seen in earth’s wind patterns

how do gravity and energy together allow us to understand orbits?

change in total energy is needed to change orbits; add enough energy and the object leaves

why do all objects fall at the same rate?

mass of object in newton’s second law exactly cancels mass in law of gravitation

differentiation

potential energy converted to kinetic energy, kinetic energy is then converted to heat

what are terrestrial planets like on the inside

core, mantle, crust; denser material is found deeper inside; depending on viscosity, they have litosphere

what causes geological activity

interior heat caused by radioactive decay

why do some planetary interiors create magnetic fields

requires motion of charged particles inside planet

shape of craters

often circular but sometimes rectangular

what kind of craters does earth have

regular craters, central peak craters, and multi-ring impact basins

mimas

moon of saturn

what processes shape planetary surfaces

cratering, volcanism, tectonics, erosion

how do impact craters reveal a surface’s geological age?

the amount of cratering tells us how long ago a surface formed

why do the terrestrial planets have different geological histories?

planetary size, distance from sun, and rotation rate