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Astronomy Chapter 22: Motions in the Heavens

22.3 The Renaissance and the heliocentric solar system. Galileo questioned the base of the Aristolean view and had a serious hardware (optics) upgrade from previous astronomers Observed the seas" (maria) on the Moon, and sunspotsJupiter had 4 objects circling itAs per a geocentric system, this

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Astronomy Chapter 22: Motions in the Heavens

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    1. Astronomy (Chapter 22): Motions in the Heavens Planetary Nebula, a cloud of gas ejected from a hot star (shown at center of nebula). Hubble Space Telescope image A Hubble Space Telescope image of the planetary nebula, NGC 6751. Glowing in the constellation Aquila like a giant eye, the nebula is a cloud of gas ejected several thousand years ago from the hot star visible at its center.A Hubble Space Telescope image of the planetary nebula, NGC 6751. Glowing in the constellation Aquila like a giant eye, the nebula is a cloud of gas ejected several thousand years ago from the hot star visible at its center.

    2. 22.3 The Renaissance and the heliocentric solar system Galileo questioned the base of the Aristolean view and had a serious hardware (optics) upgrade from previous astronomers Observed the seas (maria) on the Moon, and sunspots Jupiter had 4 objects circling it As per a geocentric system, this was not possible Observed Venus had Moon-like phases, which could not be explained with the geocentric model His Sun-centered system did not sit well with the Catholic Church of the day - he was forced to recant

    3. Galileo astronomer, mathematician, physicist Realized that the laws of nature must be understood by observation, experimentation, and analysis. Observed moving objects and derived the laws of motion Quantified and expanded later by Newton Inertia the tendency for an object to resist a change in motion Thus people traveling with the Earth would realize no motion A painting of Galileo and his students studying the heavens through his telescope. A painting of Galileo and his students studying the heavens through his telescope.

    4. Different constellations appear at different seasons. Figure 22.1 Different constellations appear at different seasons. This view shows the summer sky, as viewed by an observer facing north. The light shaded area is the Milky Way. Figure 22.1 Different constellations appear at different seasons. This view shows the summer sky, as viewed by an observer facing north. The light shaded area is the Milky Way.

    5. Orion Figure 1 (A) A seventeenth-century star atlas depicts the constellation OrionFigure 1 (A) A seventeenth-century star atlas depicts the constellation Orion

    6. A timed exposure of the night sky, at center is the North Star Figure 22.2 A time exposure of the night sky shows the rotation of the stars around the Pole Star, which is nearly motionless. Figure 22.2 A time exposure of the night sky shows the rotation of the stars around the Pole Star, which is nearly motionless.

    7. Figure 22.3 A planetarium simulation of the movement of Mars from August 1, 1990, through April 1, 1991. Mars appears to reverse direction, forming a retrograde loop. This motion was difficult to explain in the geocentric model. Figure 22.3 A planetarium simulation of the movement of Mars from August 1, 1990, through April 1, 1991. Mars appears to reverse direction, forming a retrograde loop. This motion was difficult to explain in the geocentric model.

    8. Figure 22.4 In Aristotles cosmology, water and the Earth lie in the center of the Universe, surrounded by air and fire. Beyond these four basic elements, The Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the stars lie in concentric celestial spheres. Figure 22.4 In Aristotles cosmology, water and the Earth lie in the center of the Universe, surrounded by air and fire. Beyond these four basic elements, The Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the stars lie in concentric celestial spheres.

    9. Figure 22.5 Parallax is illustrated by two photographs of a fence on the Montana prairie. (A) The photographer is nearly in line with the fence so the distant posts appear to be in line. Figure 22.5 Parallax is illustrated by two photographs of a fence on the Montana prairie. (A) The photographer is nearly in line with the fence so the distant posts appear to be in line.

    10. Figure 22.5 Parallax is illustrated by two photographs of a fence on the Montana prairie. (B) When the photographer moved, the posts appear to have shifted position. Now we can see spaces between the more distant posts. Of course, the posts have not moved, only the photographer has. The same effect has been observed in astronomical studies. As the Earth revolves about the Sun, the stars appear to shift position relative to one another. Figure 22.5 Parallax is illustrated by two photographs of a fence on the Montana prairie. (B) When the photographer moved, the posts appear to have shifted position. Now we can see spaces between the more distant posts. Of course, the posts have not moved, only the photographer has. The same effect has been observed in astronomical studies. As the Earth revolves about the Sun, the stars appear to shift position relative to one another.

    11. Figure 22.6 A nearby star appears to change position with respect to the distant stars as the Earth orbits around the Sun. This drawing is greatly exaggerated; in reality, the distance to the nearest stars is so much greater than the diameter of the Earths orbit that the parallax angle is only a small fraction of a degree. Figure 22.6 A nearby star appears to change position with respect to the distant stars as the Earth orbits around the Sun. This drawing is greatly exaggerated; in reality, the distance to the nearest stars is so much greater than the diameter of the Earths orbit that the parallax angle is only a small fraction of a degree.

    12. Figure 22.7 Series (A) shows the Earth revolving around the Sun, and series (B) shows the Sun revolving around the Earth. Now lay some thin paper over series (A) and trace the outlines of the Sun and Earth, but not the arrows or orbits. Lay this tracing over series (B) and note that they match exactly, after you shift the paper for each sketch to make sure the Sun and the Earth superimpose. Conclusion: There is no apparent difference between the Earth revolving around the Sun and vice versa, provided you do not refer to anything else, such as the outline of these diagrams or another star. Figure 22.7 Series (A) shows the Earth revolving around the Sun, and series (B) shows the Sun revolving around the Earth. Now lay some thin paper over series (A) and trace the outlines of the Sun and Earth, but not the arrows or orbits. Lay this tracing over series (B) and note that they match exactly, after you shift the paper for each sketch to make sure the Sun and the Earth superimpose. Conclusion: There is no apparent difference between the Earth revolving around the Sun and vice versa, provided you do not refer to anything else, such as the outline of these diagrams or another star.

    13. Figure 22.8 Ptolemys explanation of retrograde motion. Each planet revolves in a small orbit (the epicycle) around the larger orbit (the deferent). When the planet is in position x, it appears to be moving eastward. When it is in position Y it appears to have reversed direction and moves westward. Ptolemy did not realize that the planets moved in elliptical orbits. To compensate for this error, he placed the Earth away from the center of the deferent. Figure 22.8 Ptolemys explanation of retrograde motion. Each planet revolves in a small orbit (the epicycle) around the larger orbit (the deferent). When the planet is in position x, it appears to be moving eastward. When it is in position Y it appears to have reversed direction and moves westward. Ptolemy did not realize that the planets moved in elliptical orbits. To compensate for this error, he placed the Earth away from the center of the deferent.

    14. Figure 22.9 Nicolaus Copernicus. Figure 22.9 Nicolaus Copernicus.

    15. Figure 22.10 Retrograde motion is explained within the heliocentric model by changes in the relative positions of the Earth and the planet we are observing. Figure 22.10 Retrograde motion is explained within the heliocentric model by changes in the relative positions of the Earth and the planet we are observing.

    16. Figure 22.11 Galileo GalileiFigure 22.11 Galileo Galilei

    17. Figure 22.12 A comparison of Galileos drawing of the Moon with a modern photograph shows how accurately he drew topographical features, such as the maria A, B, and C. Although Galileo thought that the maria were seas, today we know that they are flat lava flows. Source: J. M. Pasachoff after Ewen Whitaker, Lunar and Planetary Laboratory, University of Arizona Figure 22.12 A comparison of Galileos drawing of the Moon with a modern photograph shows how accurately he drew topographical features, such as the maria A, B, and C. Although Galileo thought that the maria were seas, today we know that they are flat lava flows. Source: J. M. Pasachoff after Ewen Whitaker, Lunar and Planetary Laboratory, University of Arizona

    18. Figure 22.12 A comparison of Galileos drawing of the Moon with a modern photograph shows how accurately he drew topographical features, such as the maria A, B, and C. Although Galileo thought that the maria were seas, today we know that they are flat lava flows. Source: J. M. Pasachoff after Ewen Whitaker, Lunar and Planetary Laboratory, University of Arizona Figure 22.12 A comparison of Galileos drawing of the Moon with a modern photograph shows how accurately he drew topographical features, such as the maria A, B, and C. Although Galileo thought that the maria were seas, today we know that they are flat lava flows. Source: J. M. Pasachoff after Ewen Whitaker, Lunar and Planetary Laboratory, University of Arizona

    19. Figure 22.13 (A) In Ptolemys theory, Venus could never move farther from the Sun than is shown by the dotted lines. Therefore it would always appear as a crescent. (B) In the heliocentric theory, Venus passes through phases like the Moon. Galileo observed phases of Venus through a telescope, and concluded that the planets must orbit the Sun. Figure 22.13 (A) In Ptolemys theory, Venus could never move farther from the Sun than is shown by the dotted lines. Therefore it would always appear as a crescent. (B) In the heliocentric theory, Venus passes through phases like the Moon. Galileo observed phases of Venus through a telescope, and concluded that the planets must orbit the Sun.

    20. Figure 22.13 (A) In Ptolemys theory, Venus could never move farther from the Sun than is shown by the dotted lines. Therefore it would always appear as a crescent. Figure 22.13 (A) In Ptolemys theory, Venus could never move farther from the Sun than is shown by the dotted lines. Therefore it would always appear as a crescent.

    21. Figure 22.13 (B) In the heliocentric theory, Venus passes through phases like the Moon. Galileo observed phases of Venus through a telescope, and concluded that the planets must orbit the Sun. Figure 22.13 (B) In the heliocentric theory, Venus passes through phases like the Moon. Galileo observed phases of Venus through a telescope, and concluded that the planets must orbit the Sun.

    22. Who is this? He invented calculus andaccording to him (and building on Galileos observations), a moving object travels in a straight path unless acted upon by an outside force. Why is Earth traveling in an elliptical path? What is considered the glue of the universe? Figure 22.14 Sir Isaac Newton. Figure 22.14 Sir Isaac Newton.

    23. 22.4 The motions of the Earth and the Moon By 1700, the heliocentric system was well established rotation the Sun and planets spin on their axes Revolution the Earth traveling around the sun in its orbit Precession the wobble of Earths axis

    24. Motions of Earth and Moon (ch. 22) and the Seasons (ch. 18): Sun and Moon rise in East, set in West (why?). Moon completes its entire cycle in about 29.5 days. Sun is the center of our Solar System. Earth completes its orbit (revolution) around Sun in about 365 days (one year), and spins on its axis (rotation) about 365 times during one complete orbit. Earths axis is tilted at 23.5 degrees; this tilt along with Earths revolution around the sun, produce the seasons. Seasonal change in our view of the night sky (from Earths revolution). Figure 22.15 The night sky changes with the seasons because the Earth is continuously changing positions it orbits the Sun. Figure 22.15 The night sky changes with the seasons because the Earth is continuously changing positions it orbits the Sun.

    27. Equator receives the most concen-trated solar radiation Temps cooler toward poles From Chapter 18

    28. Seasons (From Chapter 18) What happens at the Antarctic Circle on June 21? What causes weather changes and the seasons? What is the difference between the tropics of Cancer (you would cast no shadow on June 21 in the NH) and Capricorn? When is summer solstice in the Southern Hemisphere?

    29. Beaufort Sea, Northwest Territories Canadian Arctic at midnight during July. 70 degrees north latitude. From Chapter 18

    30. During equinoxes (equal nights) all areas on the Earth receive about 12 hours of daylight and darkness. Poles not tilted toward or away from the Sun. In fact, all areas of the Earth receive the same total number of hours of sunlight every year, so why is there such a variation in climates? From Chapter 18

    31. Other types of planetary motion (back to ch. 22) Precession: 26,000 thousand year cycle. In 12,000 years, axis will point toward Vega (Earth wobbles like a spinning top). Moons gravity pulls Earth slightly out of orbit (spiral affect). Entire Solar System is moving toward Vega. Sun orbits center of Milky Way (220 km/sec; 200 million year orbit). Milky Way Galaxy speeds along through intergalactic space. Figure 22.16 The Earths axis wobbles or precesses like a top, completing one precession cycle every26,000 years. Figure 22.16 The Earths axis wobbles or precesses like a top, completing one precession cycle every26,000 years.

    32. Motion of the Moon Moon causes Earths tides Earth causes Moon to bulge, so moon rotates on axis and orbits Earth at same rate. Moonquakes Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases. Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases.

    33. -New Moon (dark) -Gibbous (waning) -Crescent Moon (4 days later); waxing -Third Quarter -First Quarter (7 days later) -Crescent (waning) -Gibbous (sliver of dark), 10 days later -New Moon again -Full Moon (14-15 days after New Moon) Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases. Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases.

    34. Waxing (d shape) Why is the Moon illuminated? Waning (c shape) What is Moons relative position to the Earth and Sun during a full Moon? Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases. Figure 22.17 Approximately every 29.5 Earth days, the Moon passes through a complete cycle of phases. The upper part of the drawing shows the EarthMoon orbital system viewed over the course of a month. The lower portion shows what the Moon looks like from Earth at the various phases.

    35. Why does the Moon rise at a different time each day? Figure 22.19 The Moon moves13.2_every day. (A) The Moon is directly above an observer on Earth.(B) One day later, the Earth has completed one complete rotation, but the Moon has traveled 13.2_.The Earth must now travel for another 53 minutes before the observer is directly under it again. Figure 22.19 The Moon moves13.2_every day. (A) The Moon is directly above an observer on Earth.(B) One day later, the Earth has completed one complete rotation, but the Moon has traveled 13.2_.The Earth must now travel for another 53 minutes before the observer is directly under it again.

    36. Most of the time the Moons shadow misses the Earth, and the Earths shadow misses the Moon. Why? What happens when they dont miss? Figure 22.18 (A) The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. (B) A sideways look at the Sun, Moon, and Earth shows that most of the time the Moons shadow misses the Earth and the Earths shadow misses the Moon. Scales are exaggerated for emphasis. Figure 22.18 (A) The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. (B) A sideways look at the Sun, Moon, and Earth shows that most of the time the Moons shadow misses the Earth and the Earths shadow misses the Moon. Scales are exaggerated for emphasis.

    37. Normally the shadows miss because the Moon lies out of the plane of the Earth-Sun orbit; during a new Moon, the Moons shadow misses the Earth; during a full Moon, the Earths shadow misses the Moon. Figure 22.20 Eclipses of the Sun and Moon. The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. Scales are exaggerated for emphasis. (A) Normally the Moon lies out of the plane of the EarthSun orbit. (B) During the new Moon the Moons shadow misses the Earth. (C) During the full Moon the Earths shadow misses the Moon. Figure 22.20 Eclipses of the Sun and Moon. The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. Scales are exaggerated for emphasis. (A) Normally the Moon lies out of the plane of the EarthSun orbit. (B) During the new Moon the Moons shadow misses the Earth. (C) During the full Moon the Earths shadow misses the Moon.

    38. Eclipses Eclipse of Sun occurs when Moon is directly between the Sun and Earth (Moon shadow on the Earth). Eclipse of Moon when Earth is directly between the Sun and Moon (Earth shadow on the Moon). Figure 22.20 Eclipses of the Sun and Moon. The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. Scales are exaggerated for emphasis. (D) However, if the Moon passes through the EarthSun plane when the three bodies are aligned properly, then an eclipse will occur.(E) An eclipse of the Sun occurs when the Moon is directly between the Sun and the Earth, and the Moons shadow is cast on the Earth.(F) An eclipse of the Moon occurs when the Earths shadow is cast on the Moon. Figure 22.20 Eclipses of the Sun and Moon. The Sun and the Earth lie in one plane, while the Moons orbit around the Earth lies in another. Scales are exaggerated for emphasis. (D) However, if the Moon passes through the EarthSun plane when the three bodies are aligned properly, then an eclipse will occur.(E) An eclipse of the Sun occurs when the Moon is directly between the Sun and the Earth, and the Moons shadow is cast on the Earth.(F) An eclipse of the Moon occurs when the Earths shadow is cast on the Moon.

    39. Solar Corona shown as a bright halo around the eclipsed Sun (1991). Figure 22.21 The solar corona appears as a bright halo around the eclipsed Sun. This photograph was taken during the July 11, 1991 total eclipse of the Sun, in La Paz, Baja California. Figure 22.21 The solar corona appears as a bright halo around the eclipsed Sun. This photograph was taken during the July 11, 1991 total eclipse of the Sun, in La Paz, Baja California.

    40. Moon relatively small, so shadow is narrow band on Earth during solar eclipse. Umbra is area of total eclipse (no greater than 275 km wide). Penumbra is wider band of partial eclipse outside of Umbra. Figure 22.22 A total solar eclipse is viewed in the narrow band, called the umbra, formed by the projection of the Moons shadow on the Earth. The penumbra is the wider band where a partial eclipse is visible. (Drawing is not to scale.) Figure 22.22 A total solar eclipse is viewed in the narrow band, called the umbra, formed by the projection of the Moons shadow on the Earth. The penumbra is the wider band where a partial eclipse is visible. (Drawing is not to scale.)

    41. Figure 22.23 During a partial solar eclipse, a dark shadow obliterates a portion of the Sun. Figure 22.23 During a partial solar eclipse, a dark shadow obliterates a portion of the Sun.

    42. Figure 22.24 Resolution is the degree to which details are distinguishable in an image. The photograph on the left has poor resolution and appears to show a single object. With increasing resolution (center and right photos)we clearly see two distinct objects. Figure 22.24 Resolution is the degree to which details are distinguishable in an image. The photograph on the left has poor resolution and appears to show a single object. With increasing resolution (center and right photos)we clearly see two distinct objects.

    43. Figure 22.25 In a refracting telescope, light is collected and focused by a large objective lens. A second lens, called the eyepiece, magnifies the image produced by the objective lens. Figure 22.25 In a refracting telescope, light is collected and focused by a large objective lens. A second lens, called the eyepiece, magnifies the image produced by the objective lens.

    44. Figure 22.26 A Newtonian reflecting telescope. Incoming light(right) is collected and focused by a curved objective mirror. The light is then reflected to the eyepiece by a secondary mirror. Figure 22.26 A Newtonian reflecting telescope. Incoming light(right) is collected and focused by a curved objective mirror. The light is then reflected to the eyepiece by a secondary mirror.

    45. Figure 22.27 (A) The 10-meterKeck Telescope is housed in the white dome on the left, located on Mauna Kea in Hawaii. In this photograph, a twin telescope, named Keck II, is under construction on the right. Figure 22.27 (A) The 10-meterKeck Telescope is housed in the white dome on the left, located on Mauna Kea in Hawaii. In this photograph, a twin telescope, named Keck II, is under construction on the right.

    46. Figure 22.27 (B) The10-meter mirror of the Keck Telescope is composed of 36separate hexagonal sections, each adjusted by computer. This view shows the mirror under construction, with 18 of the mirrors installed. Note how small the worker appears compared with the overall size of the mirror Figure 22.27 (B) The10-meter mirror of the Keck Telescope is composed of 36separate hexagonal sections, each adjusted by computer. This view shows the mirror under construction, with 18 of the mirrors installed. Note how small the worker appears compared with the overall size of the mirror

    47. Orbiting Hubble Space-telescope. It has enabled astronomers to make many new discoveries of our Solar System, our galaxy and intergalactic space. Figure 22.28 The orbiting Hubble Space Telescope has enabled astronomers to make many new discoveries of the Solar System, our galaxy, and intergalactic space. Figure 22.28 The orbiting Hubble Space Telescope has enabled astronomers to make many new discoveries of the Solar System, our galaxy, and intergalactic space.

    48. Hubble Space-telescope photograph of exploding star. More detailed images than ground-based telescopes. Figure 22.29 When a massive star dies, it explodes, blasting filaments of gas into space. The Hubble Space Telescope has photographed these stellar shreds in much more detail than is possible from ground-based instruments. Figure 22.29 When a massive star dies, it explodes, blasting filaments of gas into space. The Hubble Space Telescope has photographed these stellar shreds in much more detail than is possible from ground-based instruments.

    49. Figure 22.30 The very large array (VLA) is a radio telescope consisting of 27 mobile antennas spread out over36 kilometers. Figure 22.30 The very large array (VLA) is a radio telescope consisting of 27 mobile antennas spread out over36 kilometers.

    50. A prism disperses a beam of sunlight into a spectrum of component colors. Each color represents a different band of wavelengths. Figure 22.31 A prism disperses abeam of sunlight into a spectrum of component colors. Each color represents a different band of wavelengths. Figure 22.31 A prism disperses abeam of sunlight into a spectrum of component colors. Each color represents a different band of wavelengths.

    51. First solar absorption spectrum taken in 1811. Dark bands are the absorption lines. When light passes from hot interior to cooler outer layers of a star, some wavelengths are absorbed by atoms of a particular element. Can determine chemical composition of a star. An atoms spectrum changes with temp and pressure, so can also determine surface temp and pressures of stars. Emission spectra also helpful, but harder to detect. Figure 22.32 A copy of the first solar absorption spectrum taken in 1811. The dark lines are the absorption lines. Figure 22.32 A copy of the first solar absorption spectrum taken in 1811. The dark lines are the absorption lines.

    52. Doppler Measurement If object moving toward you, you receive higher frequency waves (such as sound waves, more per second)same with lightan object moving away emits lower frequency light waves (toward red end of spectrum). An object moving toward Earth emits higher frequency light waves (toward blue end of spectrum). Astronomers can measure relative velocities of stars, galaxies and other celestial objects that are millions or billions of light-years away. Figure 22.33 Doppler effect. (A) When a stationary source emits a signal, the frequency of the signal is unaffected by the source, and observers in any direction detect the same frequency. (B) The Doppler effect is the change in the frequency of a signal when it moves. If the source is moving toward an observer (position 1), the observer detects waves squeezed close together and therefore with higher frequency than those detected from the same source when it is stationary. If the source is moving away from an observer (position 2), the observer detects waves stretched farther apart and therefore with lower frequency. Figure 22.33 Doppler effect. (A) When a stationary source emits a signal, the frequency of the signal is unaffected by the source, and observers in any direction detect the same frequency. (B) The Doppler effect is the change in the frequency of a signal when it moves. If the source is moving toward an observer (position 1), the observer detects waves squeezed close together and therefore with higher frequency than those detected from the same source when it is stationary. If the source is moving away from an observer (position 2), the observer detects waves stretched farther apart and therefore with lower frequency.

    53. 22.5 Modern astronomy Spacecraft 10/4/57, Russia launches Sputnik 1, America follows a few months after and the race is on 6 lunar landings 25 orbital and landing missions to Venus 4 successful Mars landings Many other probes to the outer planets and small bodies The Russian Mir station and the International Space Station (under construction)

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