The entire world is agog about the upcoming “Great American Solar Eclipse” on August 21, 2017. What is a Solar eclipse? Solar eclipse is the event when the moon comes in between and obscures the Sun from Earth's view. Yes, as simple as that. If it is that simple why all this excitement? That’s because it is really not that simple. Size First let’s take the sizes. To be able to block an object, the other object should be larger or the same size. We know how large the Sun is and how small our Moon is in relation to the Sun. If the Sun were a basketball our moon would be the size of a poppy seed.(Earth is a large mustard seed) So how could a poppy seed completely block the view of a huge basketball? When viewed from the Earth, the Sun, due to the immense distance, looks small. It actually appears to be the same size of our moon which is much closer to us. Explained in numbers, the Sun’s diameter is 400 times wider than the moon's. Also the Sun is 400 times farther out in space than the moon is from Earth. In other words, moon is 400 times closer to the Earth. Therefore both the sun and the moon are apparently the same size when viewed from Earth. Hence the moon is able to block the view of the sun from Earth’s perspective. The mechanisms of a solar eclipse. The picture below clearly shows what happens during the eclipse. Image courtesy: bbc.co.uk Two types of shadows, known as umbra and penumbra, fall on Earth when the moon eclipses the Sun. The umbra region is very small in area compared to the penumbra area. Folks living in the umbra region will get to see total eclipse, and folks living in the penumbra area will get to see partial eclipse. Why not an eclipse a month? If an eclipse happens when the moon is between the Earth and Sun, then why don’t we have a solar eclipse every new moon day? We all know that moon is between Sun and Earth on those days. That’s because the moon’s planar orbit is tilted about five degrees from Earth’s orbit. The moon’s shadow is cast every new moon. However because of the moon’s orbital tilt the shadow may fall just above or below the Earth, depending on where the moon is in its orbit. Sometimes just the penumbra falls on Earth and we get to see partial solar eclipse on those days. The points were the sun, moon, and Earth fall in a straight line is called the “line of nodes”. Only when the line of nodes align with each other, known as syzygy, we get the solar eclipse. Image courtesy: theflatearthsociety.org If the moon’s orbit was not tilted, we would see a solar eclipse and a lunar eclipse every month. That would be awesome, wouldn't it? What do we see/observe during a Solar Eclipse? Corona. Corona is the outer atmosphere of the sun. It is made up of fine gases and normally invisible due to the brightness of the sun’s photosphere. Corona is much hotter than the sun. Scientist will have good chance to study the Corona at the time of the eclipse. Image courtesy: nasa.gov Chromosphere. Chromosphere is the layer between the Corona and the photosphere (about 5,000 km). This appears as the crimson colored ring. I we are lucky we may see prominences if the sun is active. The picture below shows the prominence along with the diamond ring effect. Image courtesy: ase.tufts.edu Stars may be visible. The weather cools down Birds are said to fly back to their nests believing the day has ended. The most beautiful of all – The Diamond Ring Effect. Image courtesy: nasa.gov This happens just the moment the total eclipse ends and the moon just moves a tad bit away. At one single point the Sun becomes visible and a brilliant light is seen at a point accompanied by a faint annular ring. This creates an illusion of a diamond ring. ...continued in next post due to limitation of pictures.
...continued Types of eclipses Total The moon fully blocks (“occults”) the Sun. Image courtesy: sciencing.com Partial This happens when only the penumbra region of the moon’s shadow falls on Earth. The Sun appears to be partially covered by the moon. Image courtesy: nasa.gov Annular The moon does not block the sun completely. The sun appears are a round ring (May 20, 2012) This occurs because of the elliptical orbit of the moon around hte Earth. The apparent diameter of the Moon is smaller that that of the Sun when it is further from Earth. Hence we see an annular eclipse. Image courtesy: apod.nasa.gov We exist at the right time and the right place. When it comes to witnessing solar eclipses, humans are very fortunate to exist right now and not in another 600 million years. The last total solar eclipse will be witnessed by Earthlings in about 600 million years from today and after that there will be no more Total eclipses. Earth will witness only Annular and Partial eclipses. The moon is moving away from the Earth at the rate of 4 centimeters every year. In about 600 million years the moon will appear smaller than what it appears today and will not be able to obscure the Sun fully. ************* The next Total eclipse will be in Chile, Argentina, and South Pacific on July 02, 2019, lasting a long 4 minutes, 33 seconds. India will be witnessing an annular eclipse on Dec 26, 2019. ************ Just a joke Image courtesy: briankoberlein.com Information courtesy: NASA, Space.com, and a colloquium I attended.
Really nice write-up. While I am reading about this on every media, this was a great compilation. I didn't know the moon going away from earth every year part & not being able to see total solar eclipse at all after 600 million years ! Also loved the apocalypse joke in the end! Is this your area of work?
Thank you very much @Naari Yes, Naari. Our moon is going away from us. The below link may be of interest to you. Solar System -- Moon I first saw the apocalypse joke in the colloquium. It was so novel; admired the brilliant sense of humor. I have posted some more threads. If you are interested the links are here. Space Series By Kkrish -- Index Will be posting one on Mars shortly.
Sorry to disappoint you @Naari . I am not an astronaut (wish I was); just a person deeply interested in space. The credit for my avatar goes to @justanothergirl . She found it for me. It was a gift from the heart, and so it became my avatar.
Sure will go through! The mars one shd be interesting, I am really interested to see if all the talks about humans going to mars are serious or just a gimmick because it seems so unattainable to me on a lot of levels! You going to cover this?
Nice, cute avatar! Suits you for sure with your interest. No worries! It was just a guess. I was extremely fascinated with the space & the world above in my childhood too but ended up pursuing one of the popular professions/stereotypes. Don't think I was brave enough to pursue something so different.
Thanks @Naari My fundamental aim of writing these series is just to spark interest in those who may be overwhelmed about all the information about space and my main target are children. I am hoping parents here will take these articles to their children. If these become an instrument for even one child to take a career in STEM, my mission would be accomplished. I try to make it interesting for kids; hence the highly simplified tone of language. Mars is under works. An enormous amount of information is out there about Mars and everyday new ones come in. That, combined with the distractions life brings, it is taking me longer than intended. I was planning to write only about Mars the planet. However, because you asked, I'll briefly touch the topic of Mars travel. I could answer it here, but I will have to divulge some information that is already in that thread. I thank you for asking questions. You have no idea how happy your query has made me. It's given me a lot of encouragement and motivation to continue the series.
Yes, the avatar is really cute. I love it. I am so happy to learn that you too love space. Please do continue to follow your interests. Many of us choose professions compelled by various circumstances. Lack of bravery is not the reason. We need to be pragmatic rather than idealistic most of our lives. I am a product of circumstances too. Today I would have been a woman Albert Schweitzer had I pursued my heart's desire. But I have no regrets either. I am really blessed to be working where I currently do. My work brings me in contact with scientists and researchers who have and continue to contribute much to society. I also get to attend lectures and colloquiums such as the one about Solar Eclipse. Last week I attended another on SETI by Seth Shostak.
