Solar Eclipse Review Sheet
1. Given what you know about the phases of the moon, in what phase does the moon have to be in
order for a solar eclipse to take place? Why? It has to be a new moon. A solar eclipse occurs when
the disk of the moon moves between Earth and the sun (blotting out the sun’s disk). The new moon
phase is the only phase when the moon comes between the sun and Earth.
2. What is the corona? Why is it visible only during a solar eclipse? How is this related to the moon
and sun’s angular diameter? The sun’s corona is made up of hot, low-density gas, which has a
wispy appearance due to the solar magnetic field. The corona is also significantly hotter than the
sun’s surface (the photosphere).
The corona cannot be seen because the brightness of the sun obscures it; however, during an
eclipse, the moon covers up the sun’s disk, hiding the photosphere, which allows you to see the
corona clearly ringing the moon.
The moon’s angular diameter is the right size to completely cover up the sun’s disk during a total
solar eclipse. This fact allows us to see the corona during an eclipse.
3. How are sun spots, the sun’s magnetic field, and solar flares related? The sun’s magnetic field flips
every 22 year while sun spot cycles are 11 years long (exactly half that of the change in magnetic
field). The sun spots appear to be caused by intense magnetic activity. Solar flares increase as the
number of sun spots increases – hitting their maximum as the number of sun spots hits its
maximum.
4. What is the cause of the aurora borealis and the aurora australis? The aurora borealis and aurora
australis are the product of positively charged ions, released in a solar flare from the sun and driven
by the solar wind, hitting Earth’s magnetic field.