Astronomy up to First Test! Flashcards
negative curvature
surface is curved so that it does not touch itself
curved down on top, and upside down U on sidesw
positive curvature
curved like a sphere, surface meets itself
angstrom
10^-10m
1 light year
10^16m
space dimensions
x, y, z, time
length of space called L
mass
scalar value, resistance to acceleration
electric charge
unit q. can be either + or -, related to electrical field. opposites attract
angles
theta and phi, theta is main angle phi is other. 365 degrees
Units of Arc
365° in a circle, 1°=60 minutes (‘), 1 minute = 60 seconds (“). Based on 365 days a year
Angles of Time
1 angular unit per hour, 24hrs per circle. 1 hour = 60 minutes, 1 minute = 60 seconds. min and sec instead of ‘ and “. based on 24hr day
vector
a quantity with magnitude and direction
scalar
a single-quantity number
velocity
change in position over change in time. VECTOR quantity.
acceleration
change in velocity over change in time. vector value
force
f, push or pull. vector
energy
the potential to do work, always conserved and converted
Ek
kinetic energy, 1/2mv^2
pressure
force/unit of area. vector
momentum
movingness of something, conserved, vector value. P
momentum equation
P = m * v
angular momentum
tendency of something to continue rotating, conserved, vector. L
angular momentum equation
L=MVR (v and r are vectors)
star formation
angular momentum causes ball of gas to collapse into a rotating disk w/ protostar at middle.
changing L (angular momentum)
if L and mass stay same, velocity and radius vary inversely
light
electromagnetic waves, electric wave perpendicular to a magnetic wave
photon
packet of light
field
property of space. take a point of space- what fields are there?
amplitude
highest to lowest point of a wave
wavelength
lambda, trough to trough or peak to peak
long wavelength
red
short wavelength
blue
time
T or t, period of time
gamma rays
10^-11 and down
X-rays
10^-8
UV
4x10^-7
visible
7x10^-7
infrared
10^-3
microwaves
10^-2
FM radio
10^0 to 10^ 1.5 kind of
AM radio
10^2.1-10^3
long radio
10^3
spectrum shortest to longest lambda
gamma rays, x rays, UV rays, visible rays, infrared, microwave, radio (Fm then AM), long radio
opacity
inability of certain EM wavelengths to get through different materials
atmospheric transparancy
in visible spectrum and over radio spectrum
angle of incident
the angle at which light hits a surface that refracts it, and the same angle bounces of refracts off surface
normal line
line perpendicular to straight refracting surface, makes angle with incident angle and reflected part of incident angle
theta and phi in refraction
theta- first refraction angle, phi- reflected part in refracted block
beam of light leaving square refracted block
leaves at same angle as it went into block
axis of lens
middle of lens
“infinite” source
light source is far enough away that light comes in as infinite parallel rays
as object recedes
image approaches
aperture
diameter of lens (height of lens in 2d drawing)
focal length lens property
width of lens
focal length
F (capital) where image is focused
focal ratio
F/A (aperture), brightness of image
focal ratio names
f = f/#, f = 2 == f/2
telephoto
thin lens, long focal length
wide angle
thick lens, short focal length
camera
lens focuses image onto film, kind of lens determines how much of image fits onto the film
eye
f/2, lens focuses image onto retina (upside down), eye changes thickness of lens biologically
pos lens vs neg lens
pos lens: curved out
neg lens: curved in
eye unable to see small things within focal length
use a diff lens/magnifying glass to refocus light
objective/primary lens
the first lens in a telescope
eyepiece/ocular lens
sometimes moving lens that focuses light from primary lens onto eye.
magnification
focal length of ocular/focal length of eyepiece, M = Fo/Fe
image reversal
going thru a lens makes an image upside down and backwards- BRAIN REVERSES retina image, retina can be upside down
star movement
stars move 15° west per hour
reflecting telescope
uses a mirror instead of lens to image focus
mirror properties
F and A, same as lens, concave mirror focuses to pt in front of mirror
newtonian telescope
a mirror at bottom of tube reflects light to a point, a second flat mirror a bit below point reflects light out side into eyepiece. second mirror makes image dimmer, not black spot
second mirror shape
cut at 45°, elliptical shape, to reduce interference with light coming in
adaptive optics
mirror in reflecting telescope made up of 100s of different mirrors, each can adjust on its own. changes shape/contours of mirror, 100hz changing. counters atmospheric turbulence to help focus light.
Why radio dishes are big
Radio waves are high wavelength and thus low energy and faint. A large reflective surface is needed to pick up more waves, which also sharpens e image.
solar day
24 hours mean. time it takes for one transit of the sun.
sidereal day
23hr 56 minutes. less because earth’s revolution around the sun means that it has to turn a bit farther around to line up perfectly with sun, but distant star’s pos does not change much
precession
change in the axis of a rotating body.
newton’s law of universal gravitation
G*(m+m)/r^2 = F, gravitational constant times mass of the two bodies over the radius between them sqaured equals gravitational force, or
(m+m)/r^2 proportional to F. G is the proportion
kepler’s 3rd generalized by newton
(m+m)p^2 = a^3
use of newtons generalization of keplers 3rd.
can be used for any gravitational orbit. kepler didn’t notice because mass of sun is so overwhelming its basically just mass of sun. can figure out mass if period and semi-major axis are known.
movement of stars
move 4 minutes westward each day (due to solar day being longer), moves 15° west/hr at night due to revolution
coriolis effect/low pressure areas
low pressure areas rotate backwards from their normal coriolis effect direction
atmospheric opacity
over visual range and over radio range
sodium laser for adaptive optics
creates an artificial star to calibrate instruments, high in the atmosphere so it also experiences turbulence
aricebo space telescop
in puerto rico. 1000’ aperture, biggest single telescope in world. moves feed instead of dish to tweak direction
hubble space telescope
F=189’
A= 94”
1480.49937 fstop
triangle on a curved surface
pos curve >180°
neg curve < 180°
getting spacecraft to mars
launch craft into an orbit so that earth is at perihelion and mars is at aphelion
beam width
width of the circle in the sky that a telescope is able to focus on, smaller means sharper. about half a degree often
transit
when a body crosses the middle of the sky
kinds of energy
chemical, potential, nuclear, kinetic, heat
mass and gravitational force
Fg pro m, Fg pro 1/r^2
random astro info
radio lobes, flung off axis of galaxy; wmap telescope in lagrange point found microwaves predicted left over from big bang
radio telescope layout
dish reflects radio waves into feed, feed turns them into oscillating electrical current representing intensity of waves at certain freqs
