August 21, 2017 Total Solar Eclipse Across the United States
On Monday, August 21, 2017, the contiguous United States will experience the first total solar eclipse since February 1979 when it was visible only in the Pacific Northwest!
The Moon’s approximately 70-mile wide umbral shadow will travel across the U.S. at an average speed of 2,300 miles per hour (the Moon’s approximate orbital speed) passing through 12 states, beginning on the Oregon coast and leaving the U.S. near Charleston, SC at approximately 2:49 p.m. EDT. That’s just over 90 minutes after making contact on the Oregon coast!
See a wonderful animation of the upcoming eclipse at the link below:
At this link, check out a very wonderful animation on the New Moon’s ~70-mile wide umbral shadow traveling across the United States on August 21, 2017.
WHAT ARE THE TIMES FOR THIS ECLIPSE AND ITS PATH THROUGH OUR REGION?
In the Asheville region the approximate times (which will vary depending upon where you observe this event) for this eclipse are: 1:08 p.m. EDT marks the beginning of partial phases; 2:38 p.m. EDT is the mid-point of the eclipse; and 4:01 p.m. EDT marks the end of partial phases. For more precise times at your particular observation site, go to this link, and click-on your location on the map. Remember to subtract 4 hours from the time shown on this linked web page in order to get to EDT, as these timings are using UT (GMT).
Total solar eclipses can last from as short as a few seconds to about 7 minutes and 31 seconds. Totality for this eclipse will last around 2 minutes and 35 seconds in our region, if you are on the centerline of the path of totality. The farther you are from that centerline under the path of totality, the shorter the duration of the total eclipse.
This total solar eclipse will pass across the western portion of the Great Smoky Mountains Nat’l Park, Brevard, Franklin and Murphy regions here in NC. In SC the total solar eclipse will be visible in the Greenville, Columbia and Charleston areas.
WHAT WILL YOU SEE (in the NC/SC region) DURING THE APPROXIMATE 2 MINUTES, 30 SECONDS OF TOTALITY UNDER THE “NIGHT” SKY? (click on the image below to enlarge the view)
HOW RARE ARE TOTAL SOLAR ECLIPSES?
Many of you will be surprised to read that total solar eclipses are not rare! They occur somewhere on Earth about once every 18 months on average. There are actually 68 total solar eclipses predicted to occur this century alone!
What is rare is for a total solar eclipse to occur near where you live. That’s because the frequency of a total solar eclipse occurring at the same place on Earth is very rare – about once every 4 centuries on average!
So make the short journey to position your eyes under the Moon’s shadow in the path of totality, and enjoy an unforgettable, magical, lifetime experience.
HOW CAN YOU SAFELY AND EFFECTIVELY OBSERVE THIS TOTAL SOLAR ECLIPSE?
Never look directly at the Sun, even during the partial eclipse phases, without proper eye protection. Serious damage to your vision could easily result.
So then, how do you observe the eclipse safely? You must use proper eye protection during all the partial phases of the eclipse. Sunglasses are not proper eye protection! If you are observing with your unaided eye, consider using a pair of “safe solar shades” (pictured above) to be placed directly over your eyes or prescription glasses.
For a $2 donation per pair, you may obtain these solar shades from the Astronomy Club of Asheville. Send an e-mail to contact@AstroAsheville.org for more information.
If you are under the path of totality, you will definitely want to remove your eye protection during the few minutes of totality, and enjoy the views of the Sun’s Chromosphere and Corona, the “night” skies, the stars, the constellations, and the 4 naked-eye planets! Soak-in this magical experience as those few minutes will appear to last only a few seconds!
For those of you who will use binoculars or telescopes to observe the eclipse, see this link for more information about image projection, proper and safe filters to use, and more.
If you are new to observing a total solar eclipse, consider leaving the telescope at home! This way you won’t find yourself manipulating the telescope and missing the brief few minutes of totality! Even many experienced eclipse observers leave their telescopes at home. It’s best to take it all in with your unaided eyes or a pair of properly filtered binoculars. This leaves you more mobile, should you need to move away from some cloud cover to a clearer location.
When picking a location along the path of totality in our region, you need to consider a couple of factors: cloud conditions during totality and outdoor lighting. During the month of August in the southeast U.S., there is a very high probability that you will have clouds to contend with. Use your smart phones to look at the cloud cover forecasts in your region that afternoon, and then attempt to move to a clearer location under the path of totality. Remember also that many of the outdoor lighting fixtures (like street lights and parking lot lights) operate using light sensors. It is very likely that those lights will turn “on” during totality (when the sky darkens) and diminish your view of this special event. Find a location away from those lights!
HOW AND WHY DO TOTAL SOLAR ECLIPSES OCCUR?
Although the Sun is about 400 times larger in diameter than the Moon, the Moon is able to cover the entire disk of the Sun because it is about 400 times closer to Earth than the Sun. It is this geometry that provides us with the unique total eclipses seen from Earth.
Consequently, the Sun and the Moon each appear as similarly-sized disks of about ½ degree across in the Earth’s sky! So how large is that? If you extend your arm upward as far from your body as possible, you could completely cover the disk of the full Moon with a pea held between your thumb and index finger! Although this same technique could also completely cover the Sun’s disk, please do not try it, as looking directly at the Sun can be harmful to your eyes.
A total solar eclipse occurs when a) the New Moon, passing between the Earth and the Sun, is also b) at or near one of the two lunar nodes (where the Moon’s orbit crosses the ecliptic – the orbital plane of the Sun and Earth) and c) the Moon is at or near perigee (closest approach to Earth in its elliptical orbit). These conditions cause all 3 bodies (Sun, Moon and Earth) to be aligned in a straight line where the Moon briefly covers the entire disk of the Sun, while the Moon’s umbral shadow cone reaches the surface of the Earth.
WHY DON’T TOTAL SOLAR ECLIPSES OCCUR MORE OFTEN, i.e., AT EVERY NEW MOON?
The Moon, in its elliptical orbit, moves between the Earth and the Sun from 12 to 13 times each calendar year – an event that astronomers call the New Moon. But why then don’t total solar eclipses occur more often – at each New Moon – when the Moon is passing between our planet and the Sun?
Although our Moon’s orbit generally lies near the Earth-Sun ecliptic plane, the plane of the Moon’s orbit is tilted relative to the plane of the Earth’s orbit about the Sun by an angle called its orbital inclination. The tilt of the Moon’s orbit relative to that of the Earth’s ecliptic is about 5 degrees – its orbital inclination. This is rather large, considering that the Sun and Moon appear as objects in our sky of only one-half degree.
During most of its orbit, the Moon is seen above or below the plane of the Earth’s orbit with the Sun – the ecliptic. This is also true for most of the New Moons when the Moon is passing between the Earth and the Sun. So most New Moons do not result in a total solar eclipse (see the illustration below).
For the Moon’s orbit, there are two nodes, one where the Moon is crossing the Earth-Sun orbital plane from South to North (called the ascending node), and one where the Moon is crossing the Earth-Sun orbital plane from North to South (called the descending node). The two nodes are exactly opposite each other as seen from above the Earth. These are the only 2 places in the Moon’s orbit where the Earth and the Moon can both be aligned on the same plane with the Sun.
This is exactly what happens on August 21, 2017: The Moon is crossing the Earth’s orbital plane (at the ascending node) very close to the same time as it reaches the New Moon phase with the Earth, that is, positioned between the Earth and the Sun. Couple that with the Moon being within a few days of perigee (closest approach to Earth), and this special set of circumstances results in a “total solar eclipse”.
WHEN IS THE NEXT TOTAL SOLAR ECLIPSE ACROSS THE U.S.?
The next total solar eclipse (after 2017) across the U.S. is on April 8, 2024, but, to get under the Moon’s umbral shadow (where totality occurs), you will have to travel hundreds of miles west of Asheville.
WANT EVEN MORE INFORMATION ON THIS 2017 TOTAL SOLAR ECLIPSE? Check out these two excellent website links: