AST 1002 Spring 2018 FIU Webb Test 1(Chp 1,2,3,4)

Astronomy is

an observational science-we cannot usually interact w/ our subjects

Steps of Scientific method

1. observe some phenomena, 2. propose a hypothesis, 3. make a prediction based on the hypothesis, 4. test the prediction

Theories

are ALWAYS subject to revision based on new data

1 circle

360° degrees

1 degree

60' arc minutes

1 arc minute

60" arc seconds

Moon and Sun both subtend

1/2°(30') in the sky

small angle formula

relates the apparent angle size to the physical size and distance of an object. If you know any two, you can calculate the third

What is the small angle formula?

D=θd/206265

D in small angle formula

physical size

θ in small angle formula

angular size you measure

d in small angle formula

distance to the formula

θ is

always in arc seconds

scientific notation

a method of writing and manipulating large and small numbers

Basic units

distance, time, mass

compound units

speed/velocity,density,acceleration

Astronomical Unit

the average distance between the Earth and Sun, usually used in discussing distances w/in the Solar System

1.5 x 10^8 km

Light Year

the distance light travels in one year at a vacuum, used for distance to stars and galaxies

9.5 x 10^12 km=63,240 AU

Light Year is important for

look back time

If we saw a star one light year away, we would see

what it looks like from one year ago

Parsec

the distance at which 1 AU subtends on one angle of one arc second. Used for distances to stars and galaxies.

1 parsec equals

3.1 x 10^13 km=3.26 light years β

constellation

a collection of stars that people see patterns in, different cultures throughout history have seen different patterns in the sky, ex: Orion, Sagittarius, the Big Dipper

How many official constellations are there according to the International Astronomical Union?

88

celestial sphere

an imaginary crystal sphere around the Earth onto which stars are attached

celestial equator

the intersection of the plane of the Earth's equator and the celestial equator

celestial poles

the extension of the Earth's rotational axis to the celestial sphere

ecliptic

the apparent path of the Sun along the celestial sphere or the plane of the Earth's orbit around the Sun

Seasons

changing weather patterns caused by the tilt of the Earth's rotational axis to its orbital plane(ecliptic)

pseudoscience

1. observe a phenomenon, 2. propose a hypothesis

real science

3.make a prediction, 4.test the prediction

Never..., ...

done testing, prove hypothesis

angle

opening between two lines

right angle

90°

acute angle

less than 90°

obtuse angle

more than 90°

straight angle

180°

science

a way of looking at the world, method to understand the universe not a body of knowledge

scientific method

"self-correcting" must be proven thus true

Where do astronomers work?

observatories(usually on mountains) and telescopes

altitude

distance an object appears to above the horizon

azimuth

the angular distance along the horizon to the object, measured from north towards the east along the horizon

zenith

the point on the celestial sphere directly overhead an observer

right ascension

like longitude on celestial sphere

declination

like latitude on celestial sphere

vernal equinox

starting point go right ascension and the point where ecliptic crosses the celestial equator going from south to north

Precession

the "wobble" of the Earth's rotational axis

Period of a precession

26,000 years

In a precession, it is the... the axis points, not the ... 23.5° that changes

direction, angle

Mean Solar Day

exactly 24 hours by definition

Apparent Solar Day

the time between two consecutive moons, time measured w/ respect to the Sun

Sidereal Day

time measure with respect to the "fixed" stars

23 hrs 56min long 4.01 sec

Sidereal Year

the time it takes the earth to make a complete orbit around the Sun

365.2524 solar days long

Tropical(seasonal) year

the time it takes the Sun to come back to the vernal equinox, because of precession

364.24 mean solar days

Lunar phases depend on...

the Earth-Moon-Sun position

New Moon

moon is 0° from the Sun in the sky

1st quarter

moon is 90° east of Sun in the sky

full Moon

moon is 180° from the Sun in the sky

3rd quarter

moon is 90° west of the Sun in the sky

additional phases

waning gibbous, waxing gibbous, waning crescent, waxing crescent

moon's orbit

elliptical, at a 5° angle with respect to the ecliptic plane, in an eastward direction, moves 13° further east everyday

synchronous rotation

Moon's rotational period is equal to its orbital period so we only see one side of the Moon

sidereal month

one orbit of the moon around the Earth with respect to the fixed stars

solar eclipse

Moon moves directly between Earth and Sun

1)phase must be new

2)line of nodes must point toward the Sun

lunar eclipse

Moon moves through Earth's shadow

1)phase must be full

2)line of nodes must point toward the Sun

total eclipse

observer is in the Umbra(darkest part of shadow)

partial eclipse

observer is in the Penumbra(lightest part of shadow)

annular eclipse

the angular diameter of the Moon is so small(Moon is at apogee) and cannot completely cover Sun in spite of precise allignment

cosmology

the theory of the creation and evolution of the universe

retrograde motion

apparent westward motion of the planets among the stars

geocentric cosmology

Earth-centered model, Ptolemy(100 AD), Earth in the center, celestial sphere around Earth, planets orbited Earth

heliocentric cosmology

Sun-centered model, Copernicus(1543), Sun was center of universe

What did Copernicus determine?

order of planets from Sun, sidereal periods, semi-major axes in AU

What was Tycho Brahe the first to prove?

meteors were no "shooting stars" but space debris in our atmosphere and to understand supernova are exploding stars

What did Johanes Kepler do with Tycho's data?

He deduced 3 laws of planetary motion

Kepler's First Law

orbit of a planet around the Sun is an ellipse w/ the Sun at one focus

Kepler's Second Law

planets sweep out equal areas in equal times

Kepler's Third Law

p^2=a^3 (sidereal period(yrs)=semimajor axis(in AU) cubed)

What was Galileo Galilei the first to do?

use a telescope to observe astronomical things

What were Galileo's five discoveries?

-showed Venus orbited the Sun(had phases)

-discovered 4 largest moons of Jupiter

-saw craters and mountains on the Moon

-showed the Sun had 'sunspots" and rotated

-started branch of physics known as mechanics(study of motion)

speed

how fast something moves

velocity

speed + direction

acceleration

change in velocity/change in time

momentum

mass x velocity

vector quantities

quantities that have both direction and magnitude "how much"

scaler quantities

quantities that have only magnitude "how much"

Newton's first law

(law of inertia) a body remains at rest or moves in a straight line at constant speed unless acted upon by an outside force

Newton's second law

the acceleration of an object is proportional to the force acting on the object

F=ma

Newton's third law

whenever one object exerts force on another object, the 2nd object exerts an equal but opposite force on the first object

formula: FA = −FB.

Newton's law of gravity

F= -GMm/d^2

Universal constant of gravity: 6.67 x 10^11 newtons m^2/kg^2