This composite image captures close to what the human eye sees during a total solar eclipse. The ribbons of light are the sun's atmosphere, which is controlled by the magnetic field.
Credit: NASA/S. Habbal, M. Druckmüller and P. Aniol
Hello Dear Ramblers
Hope that you are enjoying your lazy days of summer (or frigid winter days in the south half of our planet). Today, on a special Looking Up episode, we are going to discuss a celestial event causing great excitement for many. This includes not just amateur and professional astronomers. This, also, includes many Americans who marvel at one of the cosmos' most awe-inspiring events: the TOTAL SOLAR ECLIPSE! This eclipse is especially anticipated as it is the first total solar eclipse to occur over the mainland United States in 40 years. Usually, you would have to travel to far-flung, remote places to witness this spectacle. In fact, the last total solar eclipse to occur was just last year in March, when the skies of Indonesia and the western Pacific were darkened. Now, it comes to your backyard, America! Take this chance and go witness this "once-in-a-lifetime" event. Go nuts, as only you can, USA!
Image Credit: NASA via Space.Com
COSMIC ALIGNMENT
So what is happening on August 21, 2017 that has millions of people all excited and thousands of dollars traveling hundreds of miles? I'll tell you! It is the so-called "Great American Total Solar Eclipse" (only in America would you find a moniker like that..that's because America knows how to do eclipses in a big way). Anyways, I digress. On this date, an area of the US about 70 miles wide will be experiencing midday darkness. This area will stretch across parts of 12 states; from Oregon and arc down to near Charleston, South Carolina. The moon, currently in its new phase, will blot out the sun's face. Anyone blessed to be within that 70-mile ribbon of shadow will experience one of nature's "once-in-a-lifetime" spectacle. Unlike it's counterpart, the lunar eclipse, the length of time of totality is only a few minutes at best. In this case, it will average about 2 minutes. What..only two minutes?? Why is that, you ask.
Well, dear Rambler, I will tell you. It is because the moon's shadow is traveling across the surface of the Earth at a whopping 2,240 miles per hour when it hits the Oregon coast. According to the folks at Space.com, that is the average orbital speed of the moon. As it travels east, it will travel "uphill" over the curve of the Earth. The shadow speed will slow to 1,323 mph (that is still faster than the Earth is rotating at that latitude). At this point will be the longest duration of totality at 2 minutes, 45 seconds near Tennessee/Kentucky. Then, it leaves the US at Charleston, South Carolina at 1,354 mph. To sum up, the reason totality cannot last longer is because the shadow will be trekking across the country 2,496 miles (4,017 km) in just 90.7 minutes, whizzing by at an average speed of 1,651 mph (2,657 km/h).
The table below better illustrates this point. It gives totality duration, mid-totality times and shadow speeds at various cities within the path of totality. There is, also, a great site called TimeandDate.com that tell you exactly how much of the sun will be covered, plus eclipse start time, time of maximum eclipse and end time at any location on Earth.
1) Go to www.timeanddate.com. Click on "The Great American Total Solar Eclipse August 21, 2017" banner.
2) Type the name of your city or place in the "Find Eclipses In Your City" search field. Click "Go". Select the correct city or location name if more than one search result appears.
3) You will come to a page titled, "Eclipses in (city name). There, you will see the information mentioned above in an easy-to-read, graphical format. If you scroll down a little, you will see a video animation of the eclipse as seen from that location.
Data, courtesy of NASA, Image Credit: Space.com
Oh, dear Ramblers, here is a fun fact: Did you know that the Earth is the only planet in our Solar System where the apparent sizes of the sun and moon are the same? The sun is 400 times larger than the moon, but the moon is 400 times closer to us. It is this little quirk of cosmic geometry that makes the sun and the moon appear the same size in our sky, and thus, makes total solar eclipses possible. See, that was fun, wasn't it?
PROTECT THOSE PEEPERS!!
Now, my dear Ramblers, growing up remember when our mothers and grandmothers would always tell us not to look directly at the sun? "You'll go blind!", they would say. That is very good advice, especially when in the context of a solar eclipse. While only a tiny fraction of the continental US will experience the wonder of totality, the rest of you will only get to see a partial eclipse--the more of the sun is covered the closer you are to the path of totality. It is just as dangerous trying to look at a partial eclipse as it is looking at the uncovered sun! Staring at a partial eclipse directly can lead to serious eye damage, or even blindness.
Do not despair, my partial-eclipse-viewing Ramblers, there are a number of ways to safely view the partial eclipse (and even the moments leading up to and following totality, as well). They are listed below:
1) Solar-viewing or "eclipse" glasses--According to the safety recommendations published by NASA, these are a special type of glasses hundreds of thousands of times darker than regular sunglasses. The sun's disc should be the only thing visible. You can even use these to view any sunspots on the sun's surface. The current international safety standard of eclipse glasses is ISO 12312-2. Space.com lists a few manufacturers of glasses meeting this standard. They are: Rainbow Symphony, American Paper Optics and Thousand Oaks Optical.
2) Homemade pinhole projector--A pinhole projector is simply a box outfitted to safely view a partial eclipse. They are very simple to make, as the materials needed can be found at home. This short video will illustrate the materials needed and the steps of creation.
Note, you can also punch a small hole in a sheet of paper. Then take a second sheet of white paper and move it away from the first sheet until you can see the image of the partially eclipsed sun. Same principle.
Image Credit: "MrStarGuy 95mm Thread-in White-Light Solar Filter" byTodd Vorenkamp, B&H PhotoVideo, April 2017
3) Through your binoculars or telescope properly fitted with a solar filter--Now this is especially important. According to Rick Feinberg, press officer for the American Astronomical Society, or AAS, "Never view the disk of the sun through a telescope, binoculars or camera without a proper solar filter". The magnified sunlight through the telescope lenses would render even a regular pair of eclipse glasses useless and cause serious eye damage. You need to put a properly-fitted solar filter on the aperture end of your scope. That filter will achieve the same effect as the aforementioned eclipse glasses, but you will be able to see the the sun's disc in greater detail. The AAS's website also has a page that lists reputable manufacturers of telescope solar filters.
4) Natural "pinhole cameras" formed by shadows of leaves on a tree--Standing under a tree during an eclipse is a sight in itself. On a white surface like a sidewalk, you will start to notice little crescents appearing between shadows of the leaves. The openings between the leaves acts as a pinhole projector.
5) Watching the eclipse online--If you are in an area with uncooperative weather (or it's night), then you can still view the eclipse online.for free, I might add! The first way is via the Slooh Space Camera, where they will have in-depth coverage of the whole event. I watched coverage of the total lunar eclipse last year and it is a must-watch. Another live feed is provided via the folks at NASA, with coverage from 12 on-the-ground locations, as well as from research planes, high-altitude balloons and satellites.
THE MOMENT OF TOTALITY: THE BEFORE, DURING AND AFTER
Now my dear Ramblers, the moment we have all been waiting for: TOTALITY!! Congratulations, my lucky Rambler, you are about to witness one of nature's most spectacular cosmic happenings! You smile and pat yourself on the back in the satisfaction for beating the massive traffic jams that will, surely, be snarling highways leading to the path of totality by getting to your spot days early! What a little forward planning will get you! Now that you have secured your space within the path of totality, have your eclipse glasses on and ready and even your protected telescope with a quality solar filter, now you are ready! Now what? What do you expect to experience when it goes dark at mid-afternoon?
Well, my dear Rambler, a lot of neat things start to happen when totality nears. Well, as Rick Feinberg (named above) states, " It's an assault on the senses!" He couldn't be more correct (how many of you just read this in Chandler Bing's voice? ). First of all, the obvious: it's darker now. "But it's only 2:30pm", you exclaim as you start to notice the world around you take on an otherworldly hue. You look up. First, you notice that you can see stars! That's right, stars in the daytime. Plus maybe a couple of planets, too. Planets like Mercury, which normally orbit the sun too close to be seen as with the other planets.
Besides the jewels now sparkling up the firmament like diamonds at a coal party, you notice that a circle of twilight now encircles you along the horizon. Plus, the air now feels cooler than it did an hour ago. This especially is nice if you are watching in the humid environs of the American Southeast. Plus, the changing amount of light makes shadows appear extra-sharp on the ground. You can see the shadows of the individual hair strands on your head!
If you are part of a larger group of experienced eclipse viewers and astronomers, they begin to yell strange things just before the sun is blotted out. Phrases such as "Bailey's beads" and "diamond ring!" "Filters off" can also be heard around this time, as there are things happening that are not visible while wearing your eclipse glasses.
Image: COURTESY OF A.FAZEKAS, SKYSAFARI via NatGeo
Bailey's Beads 2016 & Prominence 2016 by Robert Slobins
Diamond Ring Effect courtesy of NASA TV via Space.com
Shadow Bands Image Credit: Dr. Wolfgang Strickling
Bailey's Beads
"What are Bailey's beads?" You ask one of your fellow eclipse-watchers. "Well.." he answers, "Bailey's beads are dots of sunlight shining through valleys and craters on the edge of the moon's disk." He continues, the sun's corona shines around the black circle of our satellite like a bright lion's mane on the Serengeti, "these last not even one second and they occur in the final seconds just as the moon's silhouette covers the sun. That's why when they yelled that just now, you should look up or look through your scope to see."
Diamond Ring Effect
"I also heard someone yell out 'diamond ring'!" you say with the same inquisitiveness as before. Your friend answers you just as eagerly as before, "Interesting that you ask. "As the moon's disc covers the sun's face.." he pauses. "In the last seconds, just before the sun is completely covered, a very thin crescent of light is left visible. That, plus the last Bailey's bead, will form what looks like a diamond ring..hence the name. Plus, the reason they yell 'filters off' is that you won't be able to see any of this with those eclipse glasses of yours."
Corona, Solar Flares & Shadow Bands
"Now.." your friend continues on quite the verbal pace.."now that the moon is completely covering the sun..this is the only time that you get to see the corona!". Of course, you had to ask, "The corona?" 'Wow, he doesn't even know what the corona is.' the friend thinks to himself. Of course, he uses his outer voice though when he replies, "that is the sun's outermost layer of it's atmosphere. It can only be seen by us mortals on the skin of this planet during this time." "How big is it?" you ask again. "For about a million miles out into space. It is much fainter than the sun's photosphere, the visible layer of the sun".
"You see those loops curling from the moon's disc?' "Those are solar flares. They are giant loops of solar material that go millions of miles into space. Again, they can only be seen at this time." "They look beautiful!" as you gaze upon loops colored a deep magenta-red. You are taken aback at your newfound knowledge.
"In the last few minutes before the sun is covered (yep, a lot does happen in a short period of time!), you may notice rippling light and gray shadow bands flitting across the ground. This is one of the most mysterious elements of a total solar eclipse, as not everyone can see them, plus they are extremely difficult to photograph as the contrast is very low due to the decreasing amount of sunlight." your friend quickly tells you as he goes back to attend to his equipment. This is caused by light from the sun become point-like (as with the nighttime stars) as the moon's disk covers the sun and the turbulence of the Earth's atmosphere causes that filament of light to twinkle, just like the diamonds that appeared in the firmament close to totality.
As totality draws to a close (gosh, that was fast!), you thank your newfound friend for his time in sharing his knowledge. As the events of totality act in reverse now, with the sky starting to lighten a bit again. You can't wait to go experience this again.
Ramblers, I hope that you enjoyed this special blogisode about the "Great American Solar Eclipse 2017" as much as I enjoyed writing it. Please stay tuned to this space as I will be covering an annular eclipse set to grace the skies of the Eastern Hemisphere. This will happen the day after Christmas in 2019, sort of a late Christmas present to my astronomy-loving faithful Ramblers.
Final Note (I promise): Ramblings of Robert as just introduced a new community forum called "Rambling Corner". It is a place where we can join together and share knowledge, stories, etc about the topics discusses. You can sign up by pressing the button "Login/Signup" appearing on the home page. Then, once you log in, then click "Forum" on the navigational menu to enter Ramblers' Corner.Once you sign up, you will be a part of an exclusive community of your fellow Ramblers (and maybe the "Robert" of "Ramblings of Robert", you never know!) There will be different forums about the different topics discussed. Rules of the forum will be posted on the forum page. Please follow them to ensure a good time by all.
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