Astro 100 MW


 

         

          Astro 100 MW

             The Solar System

             IUPUI (Daytime MW)

                     

                    Brian Woodahl

                    bwoodahl@iupui.edu

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

                    Office: LD 156-S, 278-9244

                    Class: IT 160, Monday and Wednesday from 12:00 - 1:15

                    http://woodahl.physics.iupui.edu/Astro100MW

                    Is the University open/closed today?



Week 1 Images


Course Information (not available until Jan 9th)


The Most Commonly Asked Question in 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.


Amazon.com Links for Textbooks (New and Used)


Excellent Beginner's Telescope for General Astronomy



Imagining the Tenth Dimension


Gravity Simulator


FYI (and Just For Fun)



Department of Physics, IUPUI - Updated on Jan 1, 2019 at 3:05 PM EST