Eclipse 101

On Monday, August 21st, 2017, for the first time since 1979 people in the continental U.S. will get to experience a solar eclipse of the Northern Hemisphere. These celestial events have inspired wonder and awe throughout human history.

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On this day all of North America will be treated to an eclipse of the sun. Anyone within the path of totality can see one of nature’s most awe inspiring sights – a total solar eclipse.

The first fact to understand about solar eclipses is that they occur because of a remarkable cosmic coincidence: the Sun is just about the same apparent size in our sky as the Moon. While the Sun is actually about 400 times larger in diameter than the Moon, the Moon is also about 400 times closer than the Sun. Therefore, the Sun and the Moon appear to be about the same size in our sky.

This single fact explains why we see total solar eclipses – the Moon has an apparent size that just barely covers the Sun completely, yet is not too large that the Sun’s atmosphere, its corona, is eclipsed as well. We on Earth occupy a celestial sweet spot to witness this sight.

Diagram showing the Earth-sun-moon geometry of a total solar eclipse. Not to scale: If drawn to scale, the Moon would be 30 Earth diameters away. The sun would be 400 times that distance. Image Credit: NASA 2017 Total Solar Eclipse event page

What is It?

This celestial event is a solar eclipse in which the moon passes between the sun and Earth and blocks all or part of the sun for up to about three hours, from beginning to end, as viewed from a given location.  For this eclipse, the longest period when the moon completely blocks the sun from any given location along the path will be about two minutes and 40 seconds.  The last time the contiguous U.S. saw a total eclipse was in 1979.

Where & When Can You See It?

You can see a partial eclipse, where the moon covers only a part of the sun, anywhere in North America. To see a total eclipse, where the moon fully covers the sun for a short few minutes, you must be in the path of totality. The path of totality is a relatively thin ribbon, around 70 miles wide, that will cross the U.S. from West to East.  Here in St. Vrain the Eclipse will begin at 10:23 AM and last until 1:14 PM, with peak coverage (93%) occurring at 11:46 AM.

2017 Solar Eclipse Guide

Information Compiled From NASA.gov