Partial Solar Eclipse
Total and partial solar eclipse
While a total solar eclipse can be seen only from the very narrow path traced out by the umbral shadow, if you’re anywhere within the significantly larger penumbral shadow you can see a partial eclipse. What it will be like depends on how far you are from the path of totality. If you’re fairly close, you’ll experience an eerie twilight. You won’t see the sun’s magnificent corona, though, because as long as any amount of sunlight is peeking around the edge of the moon it will wash out the much fainter coronal light. If you’re far from the path of totality, you might be unaware that an eclipse is even taking place. On some occasions, only the penumbral shadow reaches the earth. Then no one sees a total eclipse.
Watch a partial eclipse from the front porch of the Exploratorium.
Annular Solar Eclipse
Annular and partial solar eclipse
Image courtesy NASA.
Sometimes, when viewed from the earth, the disk of the moon appears smaller than the sun. If you’re in a direct line with the moon and the sun—along the path of annularity—you’ll see a bright ring of sunlight surrounding the dark disk of the moon when the eclipse is at its maximum point. Known as “the ring of fire,” an annular eclipse is a beautiful sight.
The apparent change in size of the moon’s disk compared to a total solar eclipse is because the distance between the earth and moon varies by about 30,000 miles (48,00 km). When the moon is close to the earth it seems larger, and we see a total eclipse; when it’s farther away it seems smaller, and we see an annular eclipse.
In the diagram showing a side view of an annular eclipse, you’ll notice that its umbral shadow doesn’t reach the earth. Instead, there’s an antumbral shadow that touches the earth during an annular eclipse.
Once in awhile, an eclipse will be total along parts of its path and annular along other parts because the umbral shadow touches the earth and then doesn’t quite touch it. This is the least frequent solar eclipse.