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Astronomy Pt. 1 > chapter 2 (pt. 2) > Flashcards

chapter 2 (pt. 2) Flashcards

Earth-viewed celestial cycle and time

1
Q

Sun Cycle

A

rotation, ecliptic

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2
Q

season

A

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

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3
Q

Moon Cycle

A

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

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4
Q

eclipses

A

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

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5
Q

time keeping

A

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

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6
Q

constellation

A

sky region and/or a star pattern

88 chosen by International Astronomical Union (IAU)

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7
Q

asterism

A

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

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8
Q

apparent visual magnitude

A

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

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9
Q

flux

A

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

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10
Q

celestial sphere

A

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

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11
Q

scientific model

A

way to think about nature, not necessarily true

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12
Q

star trail

A

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

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13
Q

circumpolar constellation

A

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

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14
Q

zenith

A

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

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15
Q

precession

A

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

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16
Q

Messier object

A

Catalogued by Charles Messier, 1760s

103 non-comet objects (all binocular viewable)

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17
Q

declination (dec)

A

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

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18
Q

right ascension (RA)

A

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

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19
Q

north celestial pole

A

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

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20
Q

angular distances

A

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)

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21
Q

Ursa Major

A

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

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22
Q

Canis Major

A

the Great Dog

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23
Q

Sirius

A

Dog Star, 8.6 ly

brightest star in the sky

24
Q

Ursa Minor

A

the Little Bear

25
Q

Polaris

A

the North Star (Alpha Ursa Minoris)

26
Q

axis

A

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

27
Q

rotation

A

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

28
Q

ecliptic

A

Earth’s orbit projected on the celestial sphere

29
Q

evening star

A

planet in the sunset sky, close to Sun over horizon

30
Q

morning star

A

in dawn sky

31
Q

seasons

A

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

32
Q

revolution (orbital motion)

A

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

33
Q

aphelion

A

Jul. 5 ~1.7% further from Sun

34
Q

perihelion

A

Jan. 3 ~1.7% closer, and seasonal cycle

35
Q

vernal equinox

A

March 20* spring begins (date varies)

36
Q

summer solstice

A

June 22* summer begins (date varies)

37
Q

autumnal equinox

A

September 22* fall begins (date varies)

38
Q

winter solstice

A

December 22* winter begins (date varies)

39
Q

synodic

A

meeting of the Sun and the Moon at new Moon

40
Q

month

A

with a phase cycle of the Moon cycle

41
Q

new Moon

A

dark, see no moon at all

42
Q

full Moon

A

fully lit

43
Q

solar eclipse

A

Moon passes between the Earth and Sun, always at new Moon

blocking part of the Sun and causes penumbra and umbra

44
Q

penumbra

A

partial shadow

45
Q

umbra

A

in total shadow

46
Q

annular eclipse

A

totality when the annulus (“ring”) of the Sun’s atmosphere is visible around Moon

47
Q

lunar eclipse

A

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

48
Q

Saros cycle

A

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

49
Q

solar day

A

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

50
Q

sidereal day

A

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

51
Q

sidereal month

A

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

52
Q

sidereal year

A

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

53
Q

synodic month

A

time for complete cycle of lunar phases, 29.52 days

54
Q

tropical year (solar year)

A

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

55
Q

apparent solar time

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

Astronomy Pt. 1 (11 decks)

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