1. Chapter 4: Eclipse www.boyce-astro.org © BRIEF 20141

2. 2 Eclipse Overview: What is an Eclipse Orbital Planes Line of Nodes Elements of a Shadow Lunar Eclipse Solar Eclipse

3. www.boyce-astro.org © BRIEF 20143 Eclipse Eclipse: What is it: An astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer

4. www.boyce-astro.org © BRIEF 20144 Eclipse Eclipse: DO NOT occur every month…why? The orbits of Moon around the Earth, and Earth around the Sun are not on same plane Lunar orbit inclined 5 degrees. Eclipse only occurs when orbital planes line up Eclipses occur in pairs: Solar…Lunar, or Lunar…Solar Time duration of an eclipse: Lunar: up to a few hours Solar: a few minutes DEMONSTRATION: http://astro.unl.edu/classaction/animations/lunarcycles/mooninc.htmlhttp://astro.unl.edu/classaction/animations/lunarcycles/mooninc.html

5. www.boyce-astro.org © BRIEF 20145 Eclipse Eclipse: Orbital Planes When orbital planes do not line up, an eclipse does not occur

6. www.boyce-astro.org © BRIEF 20146 Eclipse Eclipse: Orbital Planes Nodes: Two points where the Moon’s orbit crosses the inclination to the ecliptic Two points line on the “Line of Nodes” Nodes rotates westward 19.4° per year due to Sun’s gravitational effect on orbits. Rotation of the nodes causes an eclipse season every 173 days.

7. www.boyce-astro.org © BRIEF 20147 Eclipse Elements of a shadow: Umbra: Darkest part of a shadow Penumbra: Light perimeter of a shadow

8. www.boyce-astro.org © BRIEF 20148 Eclipse Lunar Eclipse Examples: Red because of sunlight being reddened by Earth’s atmosphere and refracted onto the Moon.

9. www.boyce-astro.org © BRIEF 20149 Eclipse Solar Eclipse: Total Eclipse: The umbra of the Moon’s shadow reaches the Earth’s surface Annular Eclipse: The umbra of the Moon’s shadow does not reach the surface of the Earth

10. www.boyce-astro.org © BRIEF 201410 Eclipse Eclipse Map:

11. www.boyce-astro.org © BRIEF 201411 Eclipse Time lapse photography examples:

12. www.boyce-astro.org © BRIEF 201412 Eclipse Questions?

13. www.boyce-astro.org © BRIEF 201413 Eclipse Types of Eclipse: Solar eclipse: Moon is between Earth and Sun Partial when only part of Sun is blocked Total when it all is blocked Annular when Moon is too far from Earth for total