APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Comments and questions about the APOD on the main view screen.
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APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by APOD Robot » Sun Feb 19, 2017 5:06 am

Image Black Sun and Inverted Starfield

Explanation: Does this strange dark ball look somehow familiar? If so, that might be because it is our Sun. In the featured image from 2012, a detailed solar view was captured originally in a very specific color of red light, then rendered in black and white, and then color inverted. Once complete, the resulting image was added to a starfield, then also color inverted. Visible in the image of the Sun are long light filaments, dark active regions, prominences peeking around the edge, and a moving carpet of hot gas. The surface of our Sun can be a busy place, in particular during Solar Maximum, the time when its surface magnetic field is wound up the most. Besides an active Sun being so picturesque, the plasma expelled can also become picturesque when it impacts the Earth's magnetosphere and creates auroras.

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tetrodehead

Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by tetrodehead » Sun Feb 19, 2017 10:14 am

Great image! Must be a night shot...

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Ann
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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by Ann » Sun Feb 19, 2017 10:45 am

tetrodehead wrote:Great image! Must be a night shot...
Midnight Sun on Altafjord, Norway.
Photo: Vberger at French Wikipedia.
Probably not, because it's usually hard to see the Sun at night.

(But yes, today's APOD is a great image. It looks surreal, as if it was taken straight out of a fantasy novel.)

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by danhammang » Sun Feb 19, 2017 6:30 pm

Kudos to Jim Lafferty. It's a very appealing image that also offers an intriguing glimpse of solar dynamics. Thank you for sharing your hard work.

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by De58te » Sun Feb 19, 2017 10:00 pm

This image isn't new. I have seen it before. In the iconic movie 2001: A Space Odyssey, when Dave arrives at Jupiter and meets the alien black monolith, the aliens send him at light speed to their home planet. That is when we see that fantastic light show of the galaxies whipping past. Around when Dave in his life pod slows down again we see planets in rainbow colors some pink planets, some purple planets, etc. There are also some stars with the inverted colors, and some black suns with the universe around them white, just like this APOD picture.
You can just marvel at how Stanley Kubrick was ahead of his time.

heehaw

Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by heehaw » Sun Feb 19, 2017 10:39 pm

Professional astronomers almost always work with inverted images: white background, black stars, I think because in the pre-electronic days, it was better to work with the negative; always a loss of signal in creating a print.

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by Wadsworth » Mon Feb 20, 2017 11:22 pm

When I saw this, I wondered how the background stars were visible and not saturated out by the light of our sun. I figured it must be a composite image. It seems that is the case.
Does the starfield in the image carry any accuracy in our stars superimposed position?

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by Chris Peterson » Tue Feb 21, 2017 12:07 am

heehaw wrote:Professional astronomers almost always work with inverted images: white background, black stars, I think because in the pre-electronic days, it was better to work with the negative; always a loss of signal in creating a print.
No, it's because our eyes are better at detecting faint darker structure against white than faint lighter structure against black.

I would not say that astronomers almost always work with inverted images. We routinely apply false color mapping to monochrome images, replacing one set of color (which includes gray scale) with another. Inversion is just one example of this. The mapping chosen is selected to maximize specific detail peculiar to the image itself.
Chris

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by neufer » Tue Feb 21, 2017 2:08 am

Chris Peterson wrote:
heehaw wrote:
Professional astronomers almost always work with inverted images: white background, black stars, I think because in the pre-electronic days, it was better to work with the negative; always a loss of signal in creating a print.
No, it's because our eyes are better at detecting faint darker structure against white than faint lighter structure against black.
http://www.atnf.csiro.au/outreach/education/senior/astrophysics/photometry_photographicastro.html wrote:
<<In normal photography the image produced is a negative which then needs to be printed as a positive image. Astronomers tend to work directly with the negative images for several reasons; to reduce chances of further errors, to maximise the image quality and often because it is easier to pick out a faint black object on a clear or white background than vice versa. Some cruel people also suggest that astronomers' dandruff falling on a positive image could be mistaken for stars!>>
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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by BillT » Tue Feb 21, 2017 11:54 pm

"Some cruel people also suggest that astronomers' dandruff falling on a positive image could be mistaken for stars!"

Makes me wonder if some star catalogues have any dandruff listed in them and what the spectral type would be.

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by Chris Peterson » Tue Feb 21, 2017 11:59 pm

BillT wrote:"Some cruel people also suggest that astronomers' dandruff falling on a positive image could be mistaken for stars!"

Makes me wonder if some star catalogues have any dandruff listed in them and what the spectral type would be.
Well, there are certainly artifacts in some catalogs caused by defects on film or CCD images.
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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by geckzilla » Wed Feb 22, 2017 2:09 am

I ran into some fingerprints in some old DSS data before. The fingerprint nebula... remarkable resemblance to the human fingerprint
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by BDanielMayfield » Wed Feb 22, 2017 4:40 am

geckzilla wrote:I ran into some fingerprints in some old DSS data before. The fingerprint nebula... remarkable resemblance to the human fingerprint
That's funny. You should print it up and run it past the FBI to see if the culprit can be identified. Then it can be accurately labled as _____ ______ 's Fingerprint Nebula. Observatories might love it as a teaching aid. :lol2:

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Re: APOD: Black Sun and Inverted Starfield (2017 Feb 19)

Post by Robert Nufer » Fri Feb 24, 2017 11:14 am

I would like to learn how the Sun's image relates to the stellar background.
(e.g. exact timepoint, imaging technique, overlay technique).