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Chapter 0Charting the HeavensCopyright 2010 Pearson Education, Inc.

Copyright 2010 Pearson Education, Inc.

Charting The HeavensCopyright 2010 Pearson Education, Inc.2

Earth is average we dont occupy any special place in the universe Universe: Totality of all space, time, matter, and energy Astronomy: Study of the universe Scales are very large, measured in light-years, the distance light travels in a year about 10 trillion miles0.1 The Obvious View Copyright 2010 Pearson Education, Inc.3Figure 0.2

Stars that appear close in the sky may not actually be close in space.0.1 The Obvious View

Copyright 2010 Pearson Education, Inc.5Stars in a constellation areQuestion 1a) physically close to each other.b) usually equal in brightness.c) about the same age.d) about the same distance away.e) in the same part of the sky.

6Answer: eQuestion 1a) physically close to each other.b) usually equal in brightness.c) about the same age.d) about the same distance away.e) in the same part of the sky.Stars in a constellation areStars within a constellation might be very different distances, ages, types, and brightness.

7a) the Earth orbits the Sun.b) the Moon orbits the Earth.c) stars are in constant motion.d) the Sun orbits the Earth.e) the Earth spins on its axis.Question 2Constellations appear to move across the sky at night because

8Answer: eQuestion 11) the motion of Earth around the Sun2) the motion of the Moon around Earth3) the motion of Mars around the Sun4) the motion of the constellations around Earth5) the spinning of Earth on its axisWhat motion is responsible for the apparent motion of the constellations (east to west) across the sky?a) the Earth orbits the Sun.b) the Moon orbits the Earth.c) stars are in constant motion.d) the Sun orbits the Earth. e) the Earth spins on its axis.Question 2Constellations appear to move across the sky at night becauseThe Sun, Moon, planets, and stars all rise and set because our planet rotates once each day.

9Figure 0.5

The celestial sphere: Stars seem to be on the inner surface of a sphere surrounding the Earth. They arent, but we can use two-dimensional spherical coordinates (similar to latitude and longitude) to locate sky objects.0.1 The Obvious View

Copyright 2010 Pearson Education, Inc.11

Full circle contains 360 (degrees). Each degree contains 60 (arc-minutes). Each arc-minute contains 60 (arc-seconds). Angular size of an object depends on actual size and distance away.More Precisely 0-1: Angular MeasureCopyright 2010 Pearson Education, Inc.12

Declination: Degrees north or south of celestial equator Right ascension: Measured in hours, minutes, and seconds eastward from position of the Sun at vernal equinox0.1 The Obvious ViewCopyright 2010 Pearson Education, Inc.13Time for Earth to orbit once around the Sun, relative to fixed stars, is sidereal year.

Tropical year follows seasons; sidereal year follows constellations in 13,000 years July and August will still be summer, but Orion will be a summer constellation.0.2 Earths Orbital MotionCopyright 2010 Pearson Education, Inc.14 Daily cycle, noon to noon, is diurnal motion solar day. Stars arent in quite the same place 24 hours later, though, due to Earths rotation around the Sun; when they are in the same place again, one sidereal day has passed.0.2 Earths Orbital Motion

Copyright 2010 Pearson Education, Inc.15Question 3What is the path that the Sun, Moon, and planets follow through the constellations? a) the celestial equatorb) the north celestial polec) the Milky Wayd) the zodiace) the ecliptic

16Answer: ea) the celestial equatorb) the north celestial polec) the Milky Wayd) the zodiace) the eclipticQuestion 3What is the path that the Sun, Moon, and planets follow through the constellations? The ecliptic also marks the plane of Earths orbit around the Sun.

17How long does it take the Sun to complete one circuit of the ecliptic?Question 4a) one hourb) one dayc) one monthd) one yeare) one decade

18Answer: d1) one hour2) one day3) one month4) one year5) one decade

How long does it take the Sun to complete one circuit of the ecliptic?Question 4The Sun moves around the ecliptic once as the Earth orbits in one year.

19The 12 constellations the Sun moves through during the year are called the zodiac; path is ecliptic.0.2 Earths Orbital Motion

Copyright 2010 Pearson Education, Inc.20a) Wobble of Earths rotation axis b) the greenhouse effectc) 23.5 tilt of Earths rotational axisd) movement of Earth closer to or farther from the Sune) global warming and coolingWhat causes Earths seasons?Question 5

21Answer: ca) Wobble of Earths rotation axis b) the greenhouse effectc) 23.5 tilt of Earths rotational axisd) movement of Earth closer to or farther from the Sune) global warming and coolingWhat causes Earths seasons?Question 5Our planets tilt, and not its changing distance from the Sun, creates seasons.

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Ecliptic is plane of Earths path around the Sun; at 23.5 to celestial equator. Northernmost point (above celestial equator) is summer solstice; southernmost is winter solstice; points where path crosses celestial equator are vernal and autumnal equinoxes. Combination of day length and sunlight angle gives seasons. Time from one vernal equinox to next is tropical year.0.2 Earths Orbital MotionCopyright 2010 Pearson Education, Inc.23Question 6a) summer.b) fall.c) winter.d) spring.The vernal equinox marks the beginning of

24Answer: dQuestion 6a) summer.b) fall.c) winter.d) spring.The vernal equinox marks the beginning of The vernal equinox occurs around March 2122.

25a) every month at new moon.b) every week at the quarter phases.c) every month at full moon.d) about every six months at new moon.e) every year at new moon.A solar eclipse happens Question 7

26Answer: da) every month at new moon.b) every week at the quarter phases.c) every month at full moon.d) about every six months at new moon.e) every year at new moon.Question 7A solar eclipse happens

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Precession: Rotation of Earths axis itself; makes one complete circle in about 26,000 years0.2 Earths Orbital MotionCopyright 2010 Pearson Education, Inc.28a) the rotation of Earths molten core. b) the gravitational pull of the Sun.c) the gravitational pull of the Moon. d) the weight of the ice at the poles.e) gravitational attractions from comets.Precession is caused byQuestion 8

29Answer: ca) the rotation of Earths molten core. b) the gravitational pull of the Sun. c) the gravitational pull of the Moon. d) the weight of the ice at the poles.e) gravitational attractions from comets.Precession is caused byQuestion 8The Moons tug creates a slow wobble that takes 26,000 years for one rotation.

30a) one dayb) one hourc) one weekd) one monthe) one yearQuestion 9How long does it take the Moon to go around the ecliptic?

31Answer: da) one dayb) one hourc) one weekd) one monthe) one yearQuestion 9How long does it take the Moon to go around the ecliptic?The Moon orbits Earth in a month, and passes in front of the constellations of the zodiac, which are arranged around the ecliptic.

32The Moon takes about 29.5 days to go through whole cycle of phases synodic month.Phases are due to different amounts of sunlit portion being visible from Earth.Time to make full 360 around Earth, sidereal month, is about 2 days shorter than synodic month.0.3 The Motion of the Moon

Copyright 2010 Pearson Education, Inc.33a) during the new moon phase.b) when the Sun blocks the Moon.c) during the full moon phase.d) always around the summer solstice.A total lunar eclipse occursQuestion 10

34Answer: ca) during the new moon phase.b) when the Sun blocks the Moon.c) during the full moon phase.d) always around the summer solstice.A total lunar eclipse occursQuestion 10

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Lunar eclipse: Earth is between the Moon and Sun Partial when only part of the Moon is in shadow Total when all is in shadow0.3 The Motion of the MoonCopyright 2010 Pearson Education, Inc.36

Solar eclipse: the Moon is between Earth and Sun 0.3 The Motion of the MoonCopyright 2010 Pearson Education, Inc.370.3 The Motion of the MoonSolar eclipse is partial when only part of the Sun is blocked, total when all is blocked, and annular when the Moon is too far from Earth for total.

Copyright 2010 Pearson Education, Inc.38a) every month at new moon.b) every week at the quarter phases.c) every month at full moon.d) about every six months at new moon.e) every year at new moon.A solar eclipse happens Question 11

39Answer: da) every month at new moon.b) every week at the quarter phases.c) every month at full moon.d) about every six months at new moon.e) every year at new moon.Question 11A solar eclipse happens

40Eclipses dont occur every month because Earths and the Moons orbits are not in the same plane.0.3 The Motion of the Moon

Copyright 2010 Pearson Education, Inc.410.3 The Motion of the MoonEclipse tracks, 2010 - 2030

Copyright 2010 Pearson Education, Inc.42a)the same phase in 24 hours. b)different phases in 24 hours.c) a lunar eclipse once a month.d) different sides of the Moon.Considering the Moons phases, everyone on Earth seesQuestion 12

43Answer: aa)the same phase in 24 hours. b)different phases in 24 hours.c) a lunar eclipse once a month.d) different sides of the Moon.Considering the Moons phases, everyone on Earth seesQuestion 12The Moon goes through its cycle of phases in about 30 days; the Earth rotates once in only 24 hours.

So everyone has a chance to see the same phase!

44Triangulation: Measure baseline and angles, and you can calculate distance.

0.4 The Measurement of DistanceCopyright 2010 Pearson Education, Inc.45Parallax: Similar to triangulation, but looking at apparent motion of object against distant background from two vantage points0.4 The Measurement of Distance

Copyright 2010 Pearson Education, Inc.46Figure 0.21

The angle of parallax increases asQuestion 13a)distances to stars increase.b)the baseline gets larger. c) the baseline gets smaller.d) the Earth moves faster in its orbit.

48Answer: ba)distances to stars increase.b)the baseline gets larger. c) the baseline gets smaller.d) the Earth moves faster in its orbit.The angle of parallax increases asQuestion 13The greater the distance between two observation points (the baseline), the larger the angle of parallax.

49Scientific theories: Must be testable Must be continually tested Should be simple Should be elegantScientific theories can be proven wrong, but they can never be proven right with 100% certainty.0.5 Science and the Scientific MethodCopyright 2010 Pearson Education, Inc.50

Observation leads to theory explaining it. Theory leads to predictions consistent with previous observations. Predictions of new phenomena are observed. If the observations agree with the prediction, more predictions can be made. If not, a new theory can be made.0.5 Science and the Scientific MethodCopyright 2010 Pearson Education, Inc.51 Astronomy: Study of the universe Stars can be imagined to be on inside of celestial sphere; useful for describing location. Plane of Earths orbit around Sun is ecliptic; at 23.5 to celestial equator. Angle of Earths axis causes seasons. Moon shines by reflected light, has phases. Solar day sidereal day, due to Earths rotation around Sun.Summary of Chapter 0Copyright 2010 Pearson Education, Inc.52 Synodic month sidereal month, also due to Earths rotation around Sun Tropical year sidereal year, due to precession of Earths axis Distances can be measured through triangulation and parallax. Eclipses of Sun and Moon occur due to alignment; only occur occasionally as orbits are not in same plane. Scientific method: Observation, theory, prediction, observation Summary of Chapter 0, cont.Copyright 2010 Pearson Education, Inc.53