Phys 102 Astronomy Name ____________________Key POSITIONS OF THE PLANETS PLANETARY POSITIONS WITH RESPECT TO THE SUN: Use appendix 11 in the Field Guide for October 1, 2019 to complete the following table: Object Planetary Longitude Atlas Chart # Constellation Elongation Sol () 188 27 Virgo ZERO! Planets in order Mercury (☿) 207 28 Virgo 19° E of orbit Venus( ) 201 28 Leo 13° E distance ♀ from Mars ( ) 178 27 Virgo 10° W the Sun. ♂ Jupiter (♃) 258 41 Ophiuchus 70° E Saturn (♄) 284 42 Sagittarius 96° E PLANETARY POSITIONS IN THE SKY The digram below shows an observer looking south at sunset. From the planetary longitude of the sun and planets abovee, show where the planets will be in the observer’s sky (some may be below the horizon). Discuss how these positions correspond to the times the planets will be visible to this observer (eg. after sunset, before sunrise or most of the night). Sun’s PL + 90° _______278° ♃ ♄ Observer’s meridian Come look for the planets ☿ with me! ♀ Sun’s PL ± 180 Sun’s PL _______8° _______ E observer W 188° Sun setting on looking western horizon ♂ south Sun’s PL - 90°: _______98° Phys. 102: Astronomy Spring 2019 PLANETARY POSITIONS IN THE SOLAR SYSTEM A view of the solar system as seen FROM ABOVE THE NORTH ECLIPTIC POLE with the sun in the center is shown below. The line from the Earth ( ) to the Sun ( ) represents the planetary longitude of the sun. For each of the five visible planets, 1) Center a protractor on the Earth, measure the elongation angle from the sun's longitude. 2) Use a ruler to determine where this crosses the orbit of the planet you're plotting, and mark the planet's position on its orbit. Special Note: Can you be certain where Mercury and Venus are in their orbits? How many positions for each planet are possible? What information will help you figure this out? Sol’s Planetary Longitude: __________188° Eastern Elongation Western Elongation Mars, Jupiter & Saturn motion seen from Earth Venus & Mercury motion seen from Earth Venus: Mars: 201°-188° = 13° E 188°-178° = 10° W Jupiter: 2 58°- 188° = 70° E Mercury: 207°-188° = 18° E Saturn: 284 ° - 188° = 96° E Mercury’s elongation on 10/1: 207 - 188 = 19° W. On 10/15 it will be 226 – 202 = 25° E. Since elongation is increasing, Mercury is on the far side of its orbit and approaching greatest elongation on 10/20/19. Venus’ elongation on 10/1: 201 - 188 = 13° E. CENTER PROTRACTOR On 10/15 it will be 218 - 202 = 16° E. Since elongation is increasing, Venus is on the far ON EARTH! side of its orbit, just past superior conjunction (greatest eastern elongation on 3/24/20). .