Paul Derrick's Stargazer



[The following is an enhanced version of Stargazer #502 (April 4, 2009).]
Eclipsed Sun showing corona
Of all astronomical phenomena, probably none are as captivating as total eclipses of the Sun, and with good reason. What could be more dramatic than having the Sun briefly disappear during a clear, cloudless day, or more alarming?

Until they figured out what was going on, our ancestors came up with many different explanations, and most didn't view eclipses as good things. Some thought an animal was eating the Sun and had to be frightened off with noise. Others saw eclipses as portends of bad events to come.

We now know total solar eclipses result when the Moon passes exactly between the Earth and Sun, blocking the Sun from view for up to several minutes.

While many have seen total eclipses of the Moon, most (including myself) have never seen a total solar eclipse. Lunar eclipses are more easily seen because, when the Moon passes through Earth's shadow in a lunar eclipse, the darkened Moon can be seen by everyone on the side of Earth facing the Moon.

But when the Moon passes in front of the Sun, it casts a narrow--on average 100-mile wide--shadow across Earth called the path of totality. The total eclipse is visible only from that narrow path, beyond which only a partial eclipse can be seen. Thus, the occurrence of a total solar eclipse over any given location on Earth is rare, explaining why most of us have never seen one.

Solar eclipse diagram Lunar eclipse diagram
LEFT: When the Moon passes exactly between the Earth and Sun, the result is a total solar eclipse.
RIGHT: When the entire Moon passes through the shadow of the Earth, the result is a total lunar eclipse.

On average less than one per decade occurs over the lower 48 states, the last three being in 1979, 1970 and 1963. And none of these passed over our southwestern quadrant of the U.S.

Between now and the end of the century, there will be 8 total solar eclipses where the path of totality passes over the lower 48 states: 2017, 2024, 2044, 2045, 2052, 2078, 2079, and 2099. That's not a lot, but the next two should be well worth the wait.

August 21, 2017, an eclipse enters the U.S. in Oregon, moves southeasterly across the heartland, and exits in South Carolina, with it's point of maximum duration of 2 minutes and 40 seconds being in western Kentucky. That's just 8 years away and during vacation season, so start making your plans.

Then, the one I'm anxiously awaiting is occurs Apr. 8, 2024. The eclipse reaches it's point of maximum duration of 4 minutes and 28 seconds in central Mexico, then enters the U.S. near Eagle Pass, Texas. It moves northeasterly, exiting the U.S. in Maine. My excitement comes from the fact that it will pass directly over my home in Central Texas, so I won't have to go anywhere. Since it will be here in only 15 years, the rest of you can start calling me to book our guest room or a camping spot in our side yard--for free, of course. We'll have a grand party.

Path of 2017 total solar eclipse Path of 2024 total solar eclipse
LEFT: Path of the Monday, Aug. 21, 2017, total solar eclipse.
RIGHT: Path of the Monday, Apr. 8, 2024, total solar eclipse.

Someone cited only as A. Sinclair has created a great animated diagram showing the path of the 2017 eclipse as it moves across the planet. The tiny black dot is the path of totality from which a totally eclipsed Sun can be seen. People in the gray area will see a partial eclipse; the nearer one is to the path of totality, the greater the percentage of the Sun will be eclipsed.


This diagram was posted on Wikimedia -- a great site for free-use and public domain materials.

ADDENDUM: Note that we have not listed or discussed partial or annular eclipses here.

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