Astro 7N Unit 1

Newton's 1st Law

object at rest or in motion in a straight line at constant speed will remain in that state unless acted upon by force

Newton's 2nd Law

- F = ma
- smaller mass moves faster, if same force

Newton's 3rd Law

for every action, there's an equal and opposite reaction

gravity equaton

g = M/R^2

more mass =

more gravity

larger separation =

less gravity

mass of planet = 2X another with same radius, gravity =

twice as strong

radius 2X another planet, gravity =

1/4 as strong

what causes day and night?

rotation of earth on its axis

how does sun appear to move in sky in course of day?

east to west bc of earths rotation (same with planets and stars)

what happens to earth in one year?

orbits the sun once

why do we have seasons?

tilt of earths axis of rotation - 23 degrees

how is earths axis tilted when we have summer in northern hemisphere?

north pole toward sun

what season is it in southern hemisphere when its summer in northern hemisphere?

winter

spring and fall day lengths

equal

winter day length

shorter than night

summer day length

longer than night

if earth's axis was not tilted...

seasons wouldn't happen

what happens to the moon in 1 month?

moves around earth once

what causes phases of the moon?

sun lighting up different fractions of part of the moon we see from earth

order of phases of moon?

new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent, new REPEAT

when is full moon visible?

- only at night
- highest in sky @ midnight
- rises 6 hours earlier (sunset)
- sets 6 hours later (sunrise)

when is new moon visible?

- during the day
- highest (transits) @ noon
- rises 6 hours earlier (sunrise)
- sets 6 hours later (sunset)

how are sun, earth, and moon positioned when new moon?

straight line: sun - moon - earth

how are sun, earth, and moon positioned when full moon?

sun - earth - moon

what is solar eclipse?

moon is blocking sun's light, or a location on the earth's surface passing under moon's shadow

how are sun, earth, moon positioned when solar eclipse?

sun - moon - earth (new)

what is lunar eclipse?

earth's shadow passes across the moon

how are sun, earth, moon positioned when lunar eclipse?

sun - earth - moon (full)

mars moons

- phobos and deimos
- tiny compared to earth's
- closer to mars and faster
- more frequent eclipses

constellation

- large defined areas of sky
- anything visibly in region in const.
- 88 total

ecliptic

- apparent path of sun over course of year with respect to distant stars
- plane in which earth orbits sun

zodiac constellations

12 or 13 that lie along ecliptic

how is ur zodiac determined?

sun was in constellation during the month you were born

winter zodiac constellations =

ones opposite sun in winter

summer zodiac constellation =

ones opposite sun in summer

photon

particle of light

forms of light, high to low NRG

gamma, X, UV, visible, IR, micro, radio

high NRG light =

high frequency = low/short wavelength = blue

low NRG light =

low frequency = high/long wavelength = red

wavelengths of radio waves =

meters and centimeters

wavelengths of visible light =

ten - billionths of a meter

wavelengths of x -rays =

EVEN SMALLER

prism

splits light into different colors by bending different wavelengths by different angles

blackbody spectrum

higher temp = more light AND peak intensity @ shorter wavelength

suns surface temp

5800 K

where does sun peak in spectrum?

visible light region around green!

room temp (K)

300 K

where does room temp peak ?

IR region

continuum spectrum

light at all wavelengths

absorption spectrum

- shows ABSORPTION lines - dark lines in spectrum @ certain wavelengths
- superimposed on continuum spectrum

what produces absorption spectrum?

less energetic gas cloud in front of light source

when/how absorption line produced?

- when electrons in atoms absorb photons and remove light of specific energies from spectrum
- electrons move from low to high NRG level

emission spectrum

shows EMISSION lines - bright lines at specific wavelengths in dark spectrum

how is emission spectra produces?

- emission of photons from atoms in gas that have elevated levels
- electrons move high to low

reflecting telescope

uses mirror to collect and focus light

refracting telescope

uses lens to collect and focus light

light- gathering power

collect light in proportion to area of mirror

angular resolution

ability to distinguish two nearby light sources

what does earth limit?

angular resolution "seeing" for ground - based telescopes -> makes stars twinkle !

magnification

zooms in on smaller portion of sky
*not super important quality of telescope

2 reasons telescopes above earth's atmosphere are better

1. some radiation can't get thru atmosphere all the way to surface (gamma, X, UV, IR)
2. conditions give clearer images w/out atm. blurring

1 reason telescopes above earths atmosphere are worse

hard and expensive to get very large light collecting area launched into space