chapter 2 (pt. 2)

Question 1

Sun Cycle

Answer 1

rotation, ecliptic

Question 2

season

Answer 2

revolution, vernal/autumnal equinox, summer/winter solstice, perihelion, aphelion

Question 3

Moon Cycle

Answer 3

phase (waxing or waning of full, gibbous, quarter, crescent, new)

Question 4

eclipses

Answer 4

solar eclipse, penumbra, umbra, annular eclipse, lunar eclipse, Saros cycle
rare, the occurrence can be mathematically calculated, lunar is more common than solar

Question 5

time keeping

Answer 5

solar day, sidereal day/month/year, synodic month, tropical year (solar year), apparent solar time

Question 6

constellation

Answer 6

sky region and/or a star pattern

88 chosen by International Astronomical Union (IAU)

Question 7

asterism

Answer 7

star group (Big Dipper) not primary constellation, may cross regions (Great Square of Pegasus)

Question 8

apparent visual magnitude

Answer 8

measure of brightness (seen with human eye) (Sun ~.27, Sirius -1.47)
Hubble sees magnitude ~30 (faint)

Question 9

flux

Answer 9

measure of light energy reaching a m^2 in one second

Question 10

celestial sphere

Answer 10

ancient belief the sky is a ceiling (sphere) surrounding Earth with attached objects, now a scientific model to describe the observed sky

Question 11

scientific model

Answer 11

way to think about nature, not necessarily true

Question 12

star trail

Answer 12

bright line or curve left by star on untracked time-lapse image of the night sky

Question 13

circumpolar constellation

Answer 13

never rise or set, circling a polar star for latitudes away from the equator cardinal directions (north point, south point, east point, west point)

Question 14

zenith

Answer 14

centre of sky above (opposite is nadir on hidden half)

Question 15

precession

Answer 15

slow circular sweep in orientation of Earth axis of rotation (like a toy top spins)

Question 16

Messier object

Answer 16

Catalogued by Charles Messier, 1760s

103 non-comet objects (all binocular viewable)

Question 17

declination (dec)

Answer 17

latitude in degrees, arc min., arc sec. of north (+), or south (-), of celestial equator - equator (dec=0º), north celestial pole (dec = +90º)

Question 18

right ascension (RA)

Answer 18

extension of longitude, in hours (h), min. (m), sec. (s) within 24 h - longitudunal line of the spring equinox (RA = 0º)

Question 19

north celestial pole

Answer 19

apparent pivot point, opposite south celestial pole, divided by celestial equator

Question 20

angular distances

Answer 20

measured in units of degree, arc minute (1/60th degree), arc second (1/60th minute - from horizon to pole is the latitude of observer (the base principle of celestial navigation)

Question 21

Ursa Major

Answer 21

the Great Bear - part of the big Dipper (not a constellation) a pointer for Polaris

Question 22

Canis Major

Answer 22

the Great Dog

Question 23

Sirius

Answer 23

Dog Star, 8.6 ly

brightest star in the sky

Question 24

Ursa Minor

Answer 24

the Little Bear

Question 25

Polaris

Answer 25

the North Star (Alpha Ursa Minoris)

Question 26

axis

Answer 26

imaginary line through centre of rotation of planet (Earth tipped 23.5º, fixed as it revolves)

Question 27

rotation

Answer 27

motion around an axis (Earth produces day and night) [24 h, 1700km/h]

Question 28

ecliptic

Answer 28

Earth's orbit projected on the celestial sphere

Question 29

evening star

Answer 29

planet in the sunset sky, close to Sun over horizon

Question 30

morning star

Answer 30

in dawn sky

Question 31

seasons

Answer 31

change in the amount of solar energy in Northern and Southern hemispheres

Question 32

revolution (orbital motion)

Answer 32

about a point outside a body (earth almost a perfect circle, 30 km/s)

Question 33

aphelion

Answer 33

Jul. 5 ~1.7% further from Sun

Question 34

perihelion

Answer 34

Jan. 3 ~1.7% closer, and seasonal cycle

Question 35

vernal equinox

Answer 35

March 20* spring begins (date varies)

Question 36

summer solstice

Answer 36

June 22* summer begins (date varies)

Question 37

autumnal equinox

Answer 37

September 22* fall begins (date varies)

Question 38

winter solstice

Answer 38

December 22* winter begins (date varies)

Question 39

synodic

Answer 39

meeting of the Sun and the Moon at new Moon

Question 40

month

Answer 40

with a phase cycle of the Moon cycle

Question 41

new Moon

Answer 41

dark, see no moon at all

Question 42

full Moon

Answer 42

fully lit

Question 43

solar eclipse

Answer 43

Moon passes between the Earth and Sun, always at new Moon | blocking part of the Sun and causes penumbra and umbra

Question 44

penumbra

Answer 44

partial shadow

Question 45

umbra

Answer 45

in total shadow

Question 46

annular eclipse

Answer 46

totality when the annulus ("ring") of the Sun's atmosphere is visible around Moon

Question 47

lunar eclipse

Answer 47

Moon moves through the shadow of the Earth, always at a new Moon, up to 1h 45min

Question 48

Saros cycle

Answer 48

18y 11 1/3 day pattern of solar and lunar eclipses, due to Moon tip of 5º to the ecliptic

Question 49

solar day

Answer 49

average length of time between successive passes of Sun across local meridian, 23 hr. 52 min.

Question 50

sidereal day

Answer 50

time of successive passes for a star across the local meridian, 23 hr. 56 min.

Question 51

sidereal month

Answer 51

time for Moon to orbit Earth once relative to a star, 27.32 days

Question 52

sidereal year

Answer 52

time for a complete orbit of Earth around the Sun relative to the stars, 365.26 days

Question 53

synodic month

Answer 53

time for complete cycle of lunar phases, 29.52 days

Question 54

tropical year (solar year)

Answer 54

time between successive spring (or autumn) equinoxes, 365.25 days

Question 55

apparent solar time

Answer 55

``` used most Sun on the local meridian noon ante (before, a.m.) post (after, p.m.) ```