Astro A-1,000


 

         

          Astro A-1,000

             The Solar System

             Purdue (Fall 2024)

                     

                    bwoodahl@purdue.edu

                    (Don't Use Brightspace to contact me, use email link)

                    Office: LD 156-S, 278-9244

                    Class: ES 2107 on Tues and Thur 10:30 - 11:45

                    http://134.68.135.8/AstroA1000



Exam 3 Study Guide


Week 14 Images


Week 13 Images


Week 12 Images


Week 11 Images


Exam 2 (Tuesday, October 29)


Exam 2 Study Guide


Quiz 8 (Thursday, October 24)


Quiz 7 (Tuesday, October 22)


Week 10 Images


Quiz 6 (Tuesday, October 15)


Week 9 Images


10 Bonus Points Opportunity


Final Exam Schedule


Week 8 Images (Thursday only)


Quiz 5 (Tuesday, October 1)


Week 7 Images


Week 6 Images


Exam 1 (Thursday, September 19)


Exam 1 Study Guide


Quiz 4 (Tuesday, September 17)


Week 5 Images


Quiz 3 (Tuesday, September 10)


Week 4 Images


Quiz 2 (Tuesday, September 3)


Week 3 Images


Quiz 1 (Tuesday, August 27)


Week 2 Images


Week 1 Images


Course Information


The TOTAL SOLAR ECLIPSE of 2017 (Monday, August 21st)


The Most Commonly Asked Question in Intro Astronomy

A solar eclipse only occurs if the New Moon is about within half a degree of the ecliptic plane (defined by the orbit path of Earth as it travels around the Sun). The Moon's orbital path, around the Earth, is (unfortunately) inclined by about 5 degrees to the ecliptic. Thus, there are only two opportunities each moonth (punning) when the Moon passes through the ecliptic. These points are called the nodes (ascending, descending). The Moon passing through a node is not sufficient, it must pass through the node during the New Moon lunar phase.

About twice a year, during an approximately 45 day window (based upon the orbital speeds of the Earth and Moon), the New Moon is close enough to a node that a solar eclipse can occur. Further complicating the motion, the Moon's orbital plane precesses relative to the ecliptic. Hence, the nodes precess around the ecliptic, completing one rotation about every 18.6 years. In addition, because the Moon's path around Earth is elliptical, during many solar eclipses the angular diameter of the Moon is not large enough to fully cover the Sun. Only when the New Moon is near a node and near perigee (i.e. closest to the Earth), does totality occur. On average, it takes about 400 years for totality to occur again at the same geographical location.


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Department of Physics & Astronomy - Updated on November 15, 2024 at 9:02 AM EST