Astronomy Third-Fourth Test Flashcards
meteoroid
Rocky body flying through the solar system
meteor
Fireball falling through Earth’s atmosphere. have radiant point, shower ones named after constellation they come from (leonids, perseids, etc) Both shower and sporadic types
meteorite
meteoroid that has survived meteor status and landed on earth’s atmosphere. falls vs finds, always sporadics.
meteorite impacts on earth.
Ranging from small rocks that bust through cars and houses to massive rocks that break up in atmosphere and cause events like Tunguska in 1908, Vladivostok in 1947, and Cheybalinsk (17m across) in 201(2). No human has even been killed by one.
Winslow Crater
Formerly called Barringer Crater. Impact crater in Arizona, not much weathered because Arizona. 1 mile across. Owned for a time by a rancher who tried to mine nickel from it. Once a passenger plane flew into it and couldn’t get out. Today, tourist destination.
Solar wind
Streams of charged particles (p+ and e- mostly) coming from sun, through empty interplanetary space. Interacts with magnetic fields and things throughout the solar system
Aurorae
Magnetic field lines around a planet cause charged particles (ie solar wind) to be directed towards the poles of a planet. These excite air molecules around poles, causing them to glow. Seen as green bands in sky, sometimes other colors. Once every 100 yrs in texas, 2-3x a year in VT, ALL THE TIME in northern canada. Can happen on any planet with mag field and atmosphere. borealis=N, australis=S.
interesting meteorites
ALHodsifjaoi, blasted off of Mars on impact, apparently greater than EV. Has life in it maybe?
Murchison asteroid from 1969 has amino acids.
Meteoroids in space
Rocky debris left over from comets. Showers when earth’s orbit crosses theirs.
corona of sun
outer layer of sun, really really hot (unknown why) but very not dense. flares from here sometimes due to magnetic fields crashing through surface. Coronal mass ejections send waves of charges particles at earth.
solar cycle.
11/22 year cycle of maximum and minimum solar activity, including number of sunspots. 11 years between maximum, but each maximum magnetic field flips and regrows.
solar wind
stream of charged particles e- and p+ flying from sun. wind is not net charged. magnetic fields of bodies directs them to poles, causing excitation of atmosphere and arorae. dangerous space radiation for astronauts.
aurorae
borealis in north and australis in south.
galiliean transformation
addition and subtraction of velocity. for example A going 90MPH south, B going 30 MPH north, C stationary. A sees B as 60mph, c sees him at 90mph. EVERYTHING IS RELATIVE, THERE IS NO ABSOLUTE FRAME OF REFERENCE.
planes and galilean xformation
Plane traveling left at 400mph, A traveling left at 300, b right at 100. A sees it at 300, because it “already has” some of the speed. B sees plane traveling at IDK
lumiferous aether
posited explanation for light in 1800s. If sound waves and water waves have a medium, so must light! It is found everywhere light permeates, excluding opaque materials. invisible to the senses. Earth revolving around sun MUST travel through it- does it drag, slipstream, around it?
michaelson-morley experiment
disproved aether theory. used split and recombined beams of light expected to show one beam slowed down as it moved through the aether. It didn’t however, showing that light does not experience galilean transformation. expected light from behind us to have to “catch up” a la the planes above. Didn’t happen.
how to account for light speed invariance
think of velocity as a change in position in space-time. space time varies with frame of reference, the dimensions of space-time are flexible depending on point of reference.
special relativity
published by einstein in 1905. wasn’t first to say it. said space and time can shrink, grow and bend. works only for non-accelerating fields.
Principles of special relativity
- The laws of physics are the same for all inertial frames of reference
- The velocity of light is the same for all observers
background of relatvity
Math worked out by Heinrich Lorentz, based on equations of James Clerk Maxwell that completely described EM fields.
changes of space-time at relativistic speeds
as an object moves faster towards speed of light, its length contracts, time passes more slowly than it, mass approaches infinity. these values become nonsensical for speed of light and beyond.
twin astronaut
works because faster twin SLOWS DOWN (outside special relativity) and returns to slower, earth frame of reference
frame of reference
an individual view of reality. THERE IS NO CORECT ONE. based on the speed of the body you are traveling on, in, for example in a car, on earth, running.
relativistic guy and skiw guy look at each other
both see each other as shorter, living, heavier. not a paradox because you can only be in one frame of reference at a time.
acceleration
outside of special relativity, part of general. is absolute, seen as the same from all frames of reference.
lorentz transformation
L’=Lo sq [1-v^2/c^2]. same with V’ and M’
Mathematically describes the relativistic transformation of something. If V is very high, close to c, the prime value is much smaller than the base.
lorentz factor
1/ sq[1-v^2/c^2] Just have no clue what this is
other lorentz stuff.
can do above lorentz transformation for length, time and mass. if the same mass applies to all of these- they must be the same thing. Leads to the conclusion that space = time and that E=mc^2.
spacetime
4d spacetime. x, y, z, T. T is weird, we can’t move through it or see through it. Still math says its same thing- we’re weird, not it.
light cone
can only see as far out as speed of light (cosmic speed limit) has reached. on an x,y coord plane with lines going left and right at C with time being up on y axis, creates x shape, in 3d space becomes cone.
tachyon
hypothetical FTL particle from 50s and 60s. not real.
elsewhere
area outside of light cone that we will never be able to see- it is so far that the speed of light will never be enough to see it.
acceleration and space-time vectors
imagine a xy graph of time on y and distance on x.
at 0c, straight up line. a speed increases, line points more righter as you go further in a shorter period of time. do it in discrete steps, starts to look like a curve. this is ACCELRATION- acceleration causes space-time to curve.
gravity
acceleration, curvature of space-time.
bullet fired in elevator in free-fall
goes straight seen from inside, from outside, has curved path
first verification of general relativity
1921 after failed in 1917. During an eclipse, saw the bending of light from distant stars around sun, as predicted by curvature of space-time.
general relativity effects
gravitational time dilation, gravitational redshift
gravitational time dilation
objects in more curved areas of space-time (stronger gravity) experience time more slowly
gravitational redshift
wavelength of light escaping from high-gravity areas (high space-time curvature) will redshift. it expends energy escaping.
atomic clock in basement of harvard
ran slower than that on roof.
gravity probe B
used four nearly perfect spheres to measure frame dragging while orbiting earth.
verifications of general relativity
precessing orbit of mercury d. 1910, gravitational lensing of light d1921, pound experiment grav time dilation 1960, earth’s frame dragging in grav probe b, mass limits of collapses stars-1935.
QED
developed by richard feynman- interaction of light with massive particles.
t and q parity
Basiclaly, all of these equations are symmetrical and look the same going back in time. A positron is just an electron back in time, e+ and e- combine to make gamma rays or a gamma ray makes them. If e- and e+ hit at 11, see both of them at 10.
4d scattering
Think 3d scattering- can go any direction. normally from past to future, by why not hit something back into time? when an e- and an e+ hit, is it not one of them hitting the other back in time?
stars
born only within galaxies and their higher density. live and die there usually.
galaxies
milky way is milky band in sky, andromeda is closest group to us.
galaxy facts
100,000ly is average diameter. 10^11 stars, 100 billion, ours has 200 bil. 1 billion galaxies in observable universe
alpha centauri
closest star system to us, is actually 3 stars, two close orbiting binaries and one far that is actual closest- proxima centauri.
pilars of creation
stellar nursury in eagle nebula. huge mass of gas and dust, stellar eggs collapsing into stars, stellar winds blowing away gas and dust.
crab nebula
remnant of supernova. neutron star/pulsar in center size of burlington.
stellar sizes
beleguese much larger than sun and it keeps goooing
layers of stars
core-where fusion happens. interior-radiative and convective zones, most of star. photosphere-visible “disk” of sun. chromosphere- spectral/absorbtion lines. corona- 3x size of photosphere, magnetic lines plunging around taking sun with them.
stellar properties
luminosity, mass, radius, surface temperature (chromo or photo), age, distance
measure distance of star
for close stars, stellar parallax from earlier units. only works for closest 10k or so. R = 1/p, R in parsecs, p in arc seconds. only works for angles big enough from 2 diff positions of earth-aka closer stars.
parsec
one parsec is 3ly. the distance from one arc second.
luminosity
stellar brightness. most obvious star trait as seen in night sky. greeks had a way of measuring apparent magnitude.
measuring luminosity
until 1850, naked eye was used to measure luminosity, 1850-1940, photographic plates were used, negative image as with blinker, but chemical emulsion does not do nice things to photographic exposure. after 1940, photo electric detectors.
photo electric luminosity detector
what einstein won nobel for. light comes in, sends off electrons, positive plate and voltage source create current, strength of current is how many electrons come off plate= how intense the light is.
magnitude system
adapted from ancient greek method. from one to ten mainly, with others. higher magnitude means dimmer- a mag one object is bright, mag 10 is much dimmer.
each level of magnitude is 2.512x dimmer than the last. So, a mag 10 object is 2.512^10 dimmer than a mag 1.
some important mags
sun : -26.7 full moon: -12.6 venus : -4.4 sirius : -1.6 naked eye limit: 6.0 binocular limit: 10.0
abs mag-luminosity conversion
-5 is 10,000
-2.5 is 1,000
0 is 100
2.5 is 10
and so on.
