Podcaster: Jay Pasachoff
Title: The Indonesian total solar eclipse of 8/9 March 2016
Organization: Williams College and Caltech
Links: http://www.eclipses.info and http://www.totalsolareclipse.org
Description: Total Solar Eclipse 8/9 March 2016 From Indonesia
Bio:Jay Pasachoff, Chair of the International Astronomical Union’s Working Group on Eclipses, is Field Memorial Professor of Astronomy at Williams College and a Visitor at Caltech. He has viewed 64 solar eclipses, and is an expert on both their use for scientific observations and their use for public education. Pasachoff is a former president of the International Astronomical Union’s Commission on Education and Development and Chair of the Historical Astronomy Division of the American Astronomical Society. He received the Education Prize of the American Astronomical Society, the Janssen Prize of the Société Astronomique de France, and this year’s Richtmyer Memorial Lecture Award from the American Association of Physics Teachers. Pasachoff is the author or co-author of The Cosmos: Astronomy in the New Millennium, the Peterson Field Guide to the Stars and Planets, and Nearest Star: The Surprising Science of Our Sun plus, on a more technical level, The Solar Corona, as well as a new, 2017 book, The Sun, for the Science Museum, London.
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Transcript:
The most dramatic event on Earth that anyone on Earth can see is a total solar eclipse of the Sun. We have one about every year and a half somewhere in the world. This year’s, on March 9th, 2016, goes across Indonesia, and the Pacific.
In 2012, there was an eclipse in Queensland, Australia. In 2013, the eclipse went across Africa (I observed from Gabon). And in 2015, we were in the Arctic, at Svalbard.
This time, Indonesia is the only country in the path of the eclipse, though at the end there are some atolls in the Pacific that are very hard to get to. The eclipse goes across Sumatra and Borneo, and then up to the Spice Islands, The weather statistics, based on decades of satellite views, are not encouraging, but we do try and every once-in-a-while we miss, but most of the time we are successful in seeing the eclipse.
The event will take place around 10 o’clock in the morning in Ternate, in the Spice Islands, the Moluccas in Indonesia, and that corresponds to about 5 o’clock in the afternoon in California and 8 o’clock in the early evening the night before [in New York], both of them the night before, the 8th of March, in New York.
The Exploratorium, at exploratorium.edu, a San Francisco organization, is going to make a webcast from the island in the Pacific.
When we observe a total eclipse of the Sun, we get the Sun up in a dark sky, with the everyday Sun–what is called the photosphere–blocked out. So the sky is not blue and the faint corona of the Sun, which is about a million times fainter than the everyday Sun, becomes visible.
The corona is exceedingly beautiful. It is held in place by the Sun’s magnetic field, with streamers coming out many times the radius of the Sun itself, with polar plumes coming out, changing from minute-to-minute and hour-to-hour, and so we try to observe the eclipse over its whole path by having different people at different places and watch for changes in the corona.
We try to study the Sun’s magnetic field, which changes as the sunspots change, over an 11-year cycle and also from day-to-day. So we are always learning something new about the Sun.
We also break down the light into its spectra and we have discovered over decades that the Sun’s outer atmosphere, the corona, is millions of degrees hot. We therefore see emission in the green from iron atoms that have lost half of their normal 26 electrons and in the red from iron atoms that have lost 9 of their normal quota of 26 electrons. So realize that if you heat an iron atom a little bit, you lose an electron; if you heat it more, you lose three electrons; so to lose 13 of the 26 electrons, requires a temperature of a million degrees.
So the corona is a plasma out in space, the kind of thing that scientists on Earth are trying to control to make energy for peaceful fusion. The Sun does that fusion very well deep inside. The energy that comes out is radiated for a while inside, and then convected (like a boiling process) to the everyday surface of the Sun, and then, just how it is injected into the corona, heating the corona to millions of degrees, is still unclear. There are several different models–computing models–but basically it has to do with the Sun’s magnetic field.
There will be many people going to Indonesia for this eclipse, for land, travelling all around in the path of the eclipse, which is only 100 miles or so wide, so just anywhere won’t do. Also, there are some cruise ships that are going in the path. And it even turns out that a normal flight on Alaska Airlines from Anchorage to Honolulu goes through totality, and so some people have arranged with them to delay the takeoff for a few minutes in order to try to get the eclipse in the middle.
So: we are very hopeful of a beautiful eclipse on March 9th (March 8th in the evening in the United States) and then we look forward to the future eclipses: On September 1st, 2016, there will be an annular eclipse that goes across the Atlantic and then across Africa. The peak is in Tanzania. We will try to observe it from Tanzania. It goes then across Madagascar and then across the French island of the Réunion. That annular eclipse won’t be fully dark, because there will be some annulus (a ring of sunlight) around the edge, but will still be interesting to see.
Then, in 2017, on February 26th, there will be an annular eclipse that goes across South America: first Chile and then Argentina, in the southern part. We will have a workshop about eclipses in Esquel, in Argentina, and then travel to the path of annularity.
But the big event, that many people are looking forward to, is the Great American Eclipse of August 21st, 2017. At that occasion, the path of totality, which is only about 60 miles wide, will cross the continental from upper left [to] lower right, from Oregon to South Carolina, and certainly anybody listening [to] this who possibly can should try to get into the path of totality. The whole of the United States, and much of Central America and South America and Canada will be in the path of the partial eclipse, but a partial eclipse is thousands of times brighter than a total eclipse and you don’t get to see the wonderful phenomena of totality. So August 21st, 2017, is a day to look forward to.
End of podcast:
365 Days of Astronomy
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