U.S. Solar Eclipse of Aug. 21, 2017

[Borg]

That chart makes me wonder how the fusion rates and quantities change as the sun burns through its hydrogen. As you get more helium, its rate of fusion with other elements increases plus, as the hydrogen quantities decrease, the radiant pressure changes which affects the fusion rates as the effective gravitational pressure increases. So many variables...

 

[mfb]

The interior gets a bit hotter and denser, increasing the fusion rate a bit and making the sun a little bit larger and more luminous. Eventually that process will accelerate and the sun becomes a red giant.

Fusion changes the core composition - the surface composition is a different thing.Apart from the helium->hydrogen process, all the elements in the sun come from its initial composition.

 

[Borg]

Apart from the helium->hydrogen process, all the elements in the sun come from its initial composition.

Yes, I should have said a star vs. the sun such that the heavier elements are only created in larger stars and only escape by way of a supernova.

 

[mfb]

Well, the Sun will create carbon later in its life, and a little bit of heavier elements.

 

[OmCheeto]

Can someone please confirm that the Iron % by mass in the Space.com in Jim's image is incorrect due to a missing zero.

Thanks!

ps. This was making me want to cry this morning, as I'm really getting tired of my bad maths...

 

[Helios]

My Magic Square of Eclipse Prophesy will predict solar eclipses on or near August 21st. All rows, columns, and diagonals will add up to 10085. There could be a few misses, but it should work pretty good otherwise. The square can be reset to any other eclipse on another year by an additive constant.

 

[mfb]

Can someone please confirm that the Iron % by mass in the Space.com in Jim's image is incorrect due to a missing zero.

Good catch. There are three mistakes.
Iron should have 0.003 by abundance (a factor 10 less), and 0.14% by mass (a factor 10 more). Sulfur should have 0.0015 by abundance (a factor 10 less).

@Helios: Where is the prediction? Where are August 23, 2044 or August 24, 2062? 24 August 2101 and 26 August 2147 made it in.
A few misses? You missed 2 out of 5 in the 21st century.

22nd century? 26 August 2109, 15 August 2110 (okay, 6 days), 25 August 2128, 15 August 2129 (6 days), 16 August 2156, 25 August 2166, 27 August 2174 (6 days), 26 August 2193, 16 August 2194 - out of these 6-9 only 3 are in.

The square can be reset to any other eclipse on another year by an additive constant.

We can get eclipses close to August 11 if we adjust add 1 everywhere to have the August 11, 2018 eclipse in the center? Then it would predict an eclipse around August 11, 2037. The last eclipse of 2037 is July 13, 2037. That is about as far away as it can get.

Where does this square come from?

Edit: The most common distance is 19 years, which is close to the length of the Saros cycles of 18 years. 9 years as half a Saros appears as well. 46 is the only other difference. 46=18+9+19.
Starting from 11 August 2018: 9 years later we have August 2, 2027. 19 more for 2046? Indeed: August 2, 2046. +19? August 2, 2065 - spot on. +46? 4 August 2111. +19? 4 August 2130. +46? 4 August 2176
I can't directly link it to Saros cycles and it misses various eclipses, but it looks like a pattern.

 

[jim hardy]

Good catch. There are three mistakes.

Well ! So much for space dot com as a reliable source.

 

[Helios]

@mfb This square should be good! So August 21, 2017 isn't the best for the center. I'll tweak it and put 1998 in the center. That's subtracting 19 years from every date. This changes the sum to 9990. All these are solar eclipses, with only two partials. It doesn't catch all eclipses, just the close and reliable ones. These I think are Y = 19, 65, 84, 130, 149, 168, 177, 223, 242, 261, 307, 326. and I made the square from these.

 

[OmCheeto]

Well ! So much for space dot com as a reliable source.

It looks as though they misabsconded the table from Hyperphysics.
Which they claim to have absconded with from a textbook: Fraknoi, Morrison & Wolff Table 14.2, Published 2000

Trying to find a free copy, I accidentally downloaded a 1200 page, 178 megabyte different text by the same authors: Astronomy, published in 2016.
They have a similar table with all the same elements, though the numbers have been revised a bit.
page 526(text book) or 536(pdf)
Table 15.2

Elem      % by #    % by mass
H         92.0        73.4
He         7.8        25.0
C          0.02       0.20
N          0.008      0.09
O          0.06       0.80
Ne         0.01       0.16
Mg         0.003      0.06
Si         0.004      0.09
S          0.002      0.05
Fe         0.003      0.14

Trying to find it, I ran across some really fascinating things:

Galileo didn't invent the telescope. He was just the first person to use it for astronomy.​

And just below table 15.2, they mention the following:

The fact that our Sun and the stars all have similar compositions and are made up of mostly hydrogen and helium was first shown in a brilliant thesis in 1925 by Cecilia Payne-Gaposchkin, the first woman to get a PhD in astronomy in the United States (Figure 15.3). However, the idea that the simplest light gases—hydrogen and helium—were the most abundant elements in stars was so unexpected and so shocking that she assumed her analysis of the data must be wrong. At the time, she wrote, “The enormous abundance derived for these elements in the stellar atmosphere is almost certainly not real.” Even scientists sometimes find it hard to accept new ideas that do not agree with what everyone “knows” to be right.​

Don't overlook plastic plumbing fittings. All kinds of clever shapes in those bins .

Good idea! I actually found one that fit. But the camera was not designed for the addition of auxiliary lenses, so it ended up not working. But I did devise something that will work. I'm almost ready!

All I need now, is a cardboard box.

1963. Interesting solution when you don't have solar filter material. Actually, I think this is a brilliant idea, for people who can't make it to totality.

 

[Seymore Proof]

What do you mean ...The points of Greatest Eclipse...will be at the opposite sides of Kentucky. The closest place to me would be in Idaho since I live near Salt lake. So would I be driving up there just to view an almost full eclipse or what?

 

[mfb]

Huh?
Everyone in the band will see a total eclipse. In the center it is longer than close to the edges. At Shelley you have a very short phase of totality, at Idaho Falls it is longer already, and between Rigby and Rexburg you have the longest totality.

The duration of the eclipse in the center of the band varies a bit as well along the band, but that is a smaller effect.

 

[OmCheeto]

What do you mean ...The points of Greatest Eclipse...will be at the opposite sides of Kentucky. The closest place to me would be in Idaho since I live near Salt lake. So would I be driving up there just to view an almost full eclipse or what?

per NASA's GLOSSARY OF SOLAR ECLIPSE TERMS;

"greatest eclipse - For solar eclipses, Greatest Eclipse (GE) is defined as the instant when the axis of the Moon's shadow cone passes closest to Earth's center."​

Don't feel bad. I had to look it up. As far as I'm concerned, it's an "eclipse nerd" term.

I don't think it will make much of a difference where you see it from, as long as you're at or very near the blue centerline.

As, the closer to the blue line you are, the longer totality lasts.

On the blue line near Idaho Falls, totality lasts 2 minutes and 18 seconds.
On the red lines, totality last about 1 second.

Driving all the way to Kentucky to be at the "Greatest eclipse" point, will add about 20 seconds to totalities duration.

Hardly worth the petrol, IMHO.

 

[OmCheeto]

...
I don't think it will make much of a difference where you see it from, as long as you're at or very near the blue centerline.
...

Unless of course, you are using NASA's map, and then you want to be near the red line:

https://eclipse2017.nasa.gov/sites/default/files/interactive_map/index.html

 

[tony873004]

Being near the edge has the advantage of longer diamond ring and Bailey's Beads and perhaps prominences. But it comes at the expense of totality duration and darkness of sky. Areas just a mile away from you are in your direct line of sight and experiencing direct sunlight.

Being far from the "Greatest Eclipse" has the advantage of giving you a longer shadow along the track of the eclipse, perhaps giving you a darker sky at mid-eclipse. You also don't have to strain your neck as much as the eclipse is lower in the sky. These advantages come at the expense of totality duration.

I got a campsite in Madres at their Oregon Solarfest. It's a 20 x 20 foot plot for my car and my tent. They've planned a large 3-day party complete with classic rock cover bands. We will get 2:03 of totality beginning at 10:19 am, and the Sun will be a comfortable 42 degrees above the horizon.

 

[SetepenSeth]

The good news for me is that I´ll be out on vacations from college on this date, the bad news, I don´t think I can afford a trip to the US, being a broken college student in Mexico City does not allow much of my budget for traveling (shame, shame). Still here will be visible as a partial eclipse, so I got that going for me, which is fine.

 

[OmCheeto]

The good news for me is that I´ll be out on vacations from college on this date, the bad news, I don´t think I can afford a trip to the US, being a broken college student in Mexico City does not allow much of my budget for traveling (shame, shame). Still here will be visible as a partial eclipse, so I got that going for me, which is fine.

There will be one in your area in about 7 years. Start saving your money, and bookmark this thread.

I'm 58 years old, and this will be the first one I've had an opportunity to see.
I just checked my military records, and discovered I was in Florida the last time an eclipse was in the area.
It's kind of funny, as just two months later I was transferred to Idaho, very near the path.
But not too funny.

 

[Stavros Kiri]

Assuming the moon is moving outwards (away from earth) at a [current] rate of about 4cm a year (1m in 25ys; 100,000km in 2.5 bill. ys), can someone give a rough estimate of when will be the last total eclipse?

 

[mfb]

~600 million years

 

[Janus]

Assuming the moon is moving outwards (away from earth) at a [current] rate of about 4cm a year (1m in 25ys; 100,000km in 2.5 bill. ys), can someone give a rough estimate of when will be the last total eclipse?

I get roughly 787 million years. This is assuming the last possible total eclipse will occur when the Earth is at aphelion while the Moon is at perigee. This does not however take into account any change in the Earth/Sun distance during that time period.

 

[Stavros Kiri]

~600 million years

Sounds reasonable, and thanks for the source (I saw the earth-solar system etc. timeline table ... - other useful deadlines/timelines on your source too).
But I mostly meant with a rough calculation, assuming noticable changes on the moon phenomenal diameter, assuming at first stage that the Earth is not moving away from the Sun ... (but it does! ...).

I get roughly 787 million years. This is assuming the last possible total eclipse will occur when the Earth is at aphelion while the Moon is at perigee. This does not however take into account any change in the Earth/Sun distance during that time period.

Sounds reasonable too, and it's about of the same order of magnitude as mfb's.

This does not however take into account any change in the Earth/Sun distance during that time period.

I agree.

 

[Janus]

Sounds reasonable, and thanks for the source (I saw the earth-solar system etc. timeline table ... - other useful deadlines/timelines on your source too).
But I mostly meant with a rough calculation, assuming noticable changes on the moon phenomenal diameter, assuming at first stage that the Earth is not moving away from the Sun ... (but it does! ...).

Sounds reasonable too, and it's about of the same order of magnitude as mfb's.

I agree.

It also doesn't take into account other factors, such as continental drift, which by changing the arrangement of the continents, alters the value of the tidal drag and thus the recession rate of the Moon.

 

[anorlunda]

It also doesn't take into account other factors, such as continental drift, which by changing the arrangement of the continents, alters the value of the tidal drag and thus the recession rate of the Moon.

Wow, I think that's pretty amazing that the models are so refined as to make effects that small significant. How big is that effect. $10^{-1}$? $10^{-3}$? $10^{-5}$?

 

[mfb]

It should be quite significant, as water tides are an important part of the process. Unfortunately it is hard to model that.

The size of Sun increases over time, this is relevant as well.

 

[Stavros Kiri]

Furthermore, both moon's recession rate as well as Earth's rotation seem to be slowing down over time (with a connection between the two effects).
E.g. see:
http://rationalwiki.org/wiki/Recession_of_the_Moon

Note: precise current moon retreat rate: (3.82±0.07) cm/yr

 

[Stavros Kiri]

looks interesting,i am looking forward for watch them

Let's enjoy the total solar eclipses for the next ~600 million years, starting with the one coming up ...
Yeah, we got time!

 

[MalcolmB]

I traveled to Penzance in the UK for the August 11 1999 eclipse and it rained!

I had better luck for the March 29 2006 one in Side,Turkey. We were right on the eclipse track and the BBC team were in the next hotel. Unfortunately dear old Patrick Moore was too ill to attend. I got some great video and stills of the event. I still had time to see it in all its glory despite fiddling with cameras!

Truly awesome is the only way to describe a total solar eclipse.

 

[Battlemage!]

This one will pass right over me. I'll be out there watching, probably in Gallatin Tennessee, or wherever in the state the best weather is.

 

[Borg]

Today's APOD put up a nice video of the path.
75% of totality across nearly the entire continental U.S.
Eclipse Across America: Path Prediction Video

 

[Borg]

NASA's Great American Total Solar Eclipse Preview @ 1 pm ET Today

On Wednesday, June 21 - the summer solstice - NASA will hold two major press conferences to provide an overview of the Aug. 21 total solar eclipse, which will be visible to potentially millions of people as the moon's shadow crosses the continental United States from Oregon to South Carolina. You can watch the briefings here, courtesy of NASA TV, beginning at 1 p.m. EDT (1700 GMT) - See more at: https://www.space.com/17933-nasa-television-webcasts-live-space-tv.html#sthash.HLP2eYtS.dpuf

 

[Stavros Kiri]

1. Science Briefing about the eclipse by NASA (a bit lengthy, but good video):


2. Interesting and short ... :

 

[Stavros Kiri]

New & interesting (excellent videos from NASA):
1. Eclipse Primer on "This Week @NASA" (Today, Fri June 23, 2017):

2. Ways to watch the Eclipse (came out on 6/21/17):

3. Safety Briefing (6/21/17):

 

[stoomart]

Today's APOD put up a nice video of the path.
75% of totality across nearly the entire continental U.S.
Eclipse Across America: Path Prediction Video

This makes me glad to be living in Salem, I just hope the weather doesn't do anything crazy. :)

 

[Borg]

For those who haven't gotten glasses yet (like me), 2 million free eclipse glasses will be available at libraries throughout the US.

An interactive map of libraries participating in the eclipse project across the country can be found online.

 

[Stavros Kiri]

For those who haven't gotten glasses yet (like me), 2 million free eclipse glasses will be available at libraries throughout the US.

I still have my packet of "Science&Telescope" eclipse glasses from the Aug. 11, 1999 eclipse in Europe. Who thinks they are still safe to use them?

Here's also a couple of short videos from back then: