APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Comments and questions about the APOD on the main view screen.
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APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by APOD Robot » Sat Mar 28, 2015 4:11 am

Image Diamond Rings and Baily's Beads

Explanation: Near the March 20 equinox the cold clear sky over Longyearbyen, Norway, planet Earth held an engaging sight, a total eclipse of the Sun. The New Moon's silhouette at stages just before and after the three minute long total phase seems to sprout glistening diamonds and bright beads in this time lapse composite of the geocentric celestial event. The last and first glimpses of the solar disk with the lunar limb surrounded by the glow of the Sun's inner corona give the impression of a diamond ring in the sky. At the boundaries of totality, sunlight streaming through valleys in the irregular terrain along the Moon's edge, produces an effect known as Baily's Beads, named after English astronomer Francis Baily who championed an explanation for the phenomenon in 1836. This sharp composition also shows off the array of pinkish solar prominences lofted above the edge of the eclipsed Sun.

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epszteinbenoit

Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by epszteinbenoit » Sat Mar 28, 2015 9:59 am

The irregularities on some of the diamonds are the translation of lunar mountains obscuring sunlight.

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by JohnD » Sat Mar 28, 2015 11:21 am

In a previous thread about this eclipse, I asked if the fact that this occurred at the time of a "super-moon" would mean that there would be no "Baily's Beads", because the apparently larger Moon would cover the whole of the Sun's disc at totality. I didn't get an answer.
Baily's Beads occur at totality, when the Moon only JUST matches the Sun's diameter. The Moon has deep valleys that the sun shines through around the terminator. They can occur anywhere around the disc, and a very good example is shown on this website, about the recent eclipse: http://www.naasbeginners.co.uk/News/Sol ... ch2015.htm About half way down. Multiple 'beads' all around the disc.

Conversely, this Apod shows only one bright spot either just before or just after totality. This is the "Diamond Ring" effect that has a different origin. In the moments when the Moon's disc leaves one speck of the Sun visible just before it achieves totality, or moves away revealing the Sun again, that tiny sliver of brilliance appears at one single point on the disc, like a solitaire diamond. That this was also a 'super-moon' did mean that Baily's Baeds could not be seen this time.

The APOD is a great picture of the Diamond Ring, but does not show Baily's Beads.
The title and description of this APOD should be revised to remove all reference to the Beads.

John

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by geckzilla » Sat Mar 28, 2015 11:49 am

What are you talking about? there are clearly multiple bright spots before and just after totality.
Just call me "geck" because "zilla" is like a last name.

epszteinbenoit

Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by epszteinbenoit » Sat Mar 28, 2015 12:00 pm

Look toward the right ring number three and left number four: they both show a lack of sunlight on their lower part due to a moon mountain still obscuring sunlight. In other rings you have, albeit less visible smaller bits of extra sunlight due to the inverse phenomenon.

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by rstevenson » Sat Mar 28, 2015 12:26 pm

I also don't see any beads here. Diamond ring, yes; solar flares, yes; irregular illumination around the Moon's rim at totality, yes; but no beads.

Rob

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by JohnD » Sat Mar 28, 2015 1:59 pm

But if you look at the link I posted, you will see what I mean by multiple Beads.

Compare this video of the 2010 eclipse, when the Moon's disc was visibly SMALLER than that of the Sun: https://www.youtube.com/watch?v=MoqoruoVy-w
JOhn

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by neufer » Sat Mar 28, 2015 3:10 pm

JohnD wrote:
But if you look at the link I posted, you will see what I mean by multiple Beads.

Compare this video of the 2010 eclipse, when the Moon's disc was visibly SMALLER than that of the Sun: https://www.youtube.com/watch?v=MoqoruoVy-w
With but 2 beads today's APOD is a relatively poor example of Baily's Beads.

(RJN makes up some swell stories about APOD phenomena.
He gives them names and everything.)

Art Neuendorffer

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by Ron-Astro Pharmacist » Sat Mar 28, 2015 5:53 pm

Sometimes one might wonder if shadows could ever cast "light" onto our world?

http://www.popsci.com/science/article/2 ... oms-shadow

It's a wonder atoms even have shadows! :|
Make Mars not Wars

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by daddyo » Sun Mar 29, 2015 2:48 am

Looks like the black hole in the movie Interstellar

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by JohnD » Sun Mar 29, 2015 7:46 am

Thank you neufer!
That's the pic I linked to, showing multiple Beads, all around the disk.
At a "mini-moon" time?
John

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by JohnD » Mon Apr 20, 2015 9:05 am

The picture today (20th April 2015) on APOD's sister (rival?) webpage ESPOD, shows pictures from both Svalbard and the Faroes.
The latter is a 'close-up' showing solar flares, but also, apparently the Mountains of the Moon, as an irregular outline to the shadowed disc against the solar corona, and the flares.
See http://epod.usra.edu/ for that date.
Is this irregularity a real image, or is the outline made irregular by the atmosphere of the Earth?

John

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by Chris Peterson » Mon Apr 20, 2015 2:22 pm

JohnD wrote:The picture today (20th April 2015) on APOD's sister (rival?) webpage ESPOD, shows pictures from both Svalbard and the Faroes.
The latter is a 'close-up' showing solar flares, but also, apparently the Mountains of the Moon, as an irregular outline to the shadowed disc against the solar corona, and the flares.
See http://epod.usra.edu/ for that date.
Is this irregularity a real image, or is the outline made irregular by the atmosphere of the Earth?
The variation from the highest point on the Moon to the lowest is around 1% of its mean radius, which is about the scale of the edge variation seen in the image. But we never see such excursions in height because the gradients are so shallow. Mountains and crater walls which are prominent have deviations of only a few thousand meters, much less than a pixel at the scale of the image here.

Any image of the Moon that we can see as round will have an edge roughness below the resolution of our eyes. Images of the Moon where we actually see mountains rising along the edge are all at very high magnification (or taken from lunar orbit) and the lunar horizon looks nearly linear.

All of the bumpiness in this image is from atmospheric seeing effects.
Chris

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Re: APOD: Diamond Rings and Baily's Beads (2015 Mar 28)

Post by JohnD » Mon Apr 20, 2015 2:49 pm

Thanks, Chris!