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Physics, Astronomy & Cosmology / Re: Which stars by name or type emit polarised light?

« on: 22/03/2021 09:54:38 »

Found a Lengthy article on Polarised Light.
👍

https://www.microscopyu.com/techniques/polarized-light/introduction-to-polarized-light#:~:text=Common%20examples%20of%20surfaces%20that,than%20those%20with%20different%20orientations.

I'm still searching for Astronomical sources besides Regulus Egg Crab & Jupiter...a lil more time required.
🙏

P.S. C'ya soon.
😊

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Physics, Astronomy & Cosmology / Re: Contribution of latent heat of fusion of iron at the Earth’s inner core

« on: 22/03/2021 01:08:11 »

I'm interested in looking into this. I'll do a bit of research and get back to you.

EDIT: the latent heat of fusion of iron is about 0.21 kilojoules per gram, whereas the latent heat of fusion of an iron-nickel alloy called FeNi36 is 0.28 kilojoules per gram. I need to point out that the heat of fusion of iron and iron alloys is very probably different under extreme pressure than under atmospheric pressure. How much different, I don't know. Just to see where the calculations go, I'll just use these numbers.

The mass of the inner core is about 10²⁶ grams. If the inner core was right at its melting point (it isn't, but we're making simplifying assumptions), then going from a molten state to a solid state would involve the release of 2.1 x 10²⁵ kilojoules of heat (if it's pure iron) or 2.8 x 10²⁵ kilojoules of heat (if it's the iron-nickel alloy I'm using).

The Earth's inner core is estimated to be growing at a rate of about 1 millimeter per year (I assumed that was a radius increase of 1 millimeter for the calculations. Maybe I should have made that half a millimeter?). After crunching the numbers using that metric, I calculated that the inner core is currently losing heat at a rate of between 4.9 x 10¹⁶ and 6.5 x 10¹⁶ kilojoules per year (depending on whether one uses iron or the iron-nickel alloy for the math).

You said to assume that the rate of heat loss is constant (it isn't, but again, let's see where the math goes). If we do assume a constant rate of heat loss, you end up with the inner core right at its melting point going from pure liquid to its current size in about 430 million years. I'm honestly surprised that number turned out to be as close to your stated figure of 565 million years as it was.

But, as I pointed out before, my math made a lot of simplifying assumptions. It doesn't take into account the fact that the only place in the core that has a temperature around the core's melting point is roughly the boundary between the inner and outer core (obviously, since that's where it's solidifying). It doesn't take into account changes in heat of fusion due to pressure. It doesn't take frictional heating or radioactive heating into consideration either. Nor does it take the changing rate of heat loss over time into consideration.

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Physics, Astronomy & Cosmology / Re: Which stars by name or type emit polarised light?

« on: 21/03/2021 16:40:33 »

You mention dust in regard to this. Brian May's thesis, which has been published in book form is about dust. See https://spiral.imperial.ac.uk/handle/10044/1/1333

While this is not directly related to your post it is of interest generally.

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Physics, Astronomy & Cosmology / Re: Which stars by name or type emit polarised light?

« on: 20/03/2021 20:22:13 »

Hi @Astrogazer
🙋

You seem to have already figured out everything for yourself...so what exactly are you seeking...like a complete list of all such Stars with their precise locations in the Sky?
🤔

P.S. - 🔭

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Physics, Astronomy & Cosmology / Re: Please explain the ‘angles’ in this abstract.

« on: 11/03/2021 11:15:14 »

A draft of the paper is available from a pre-print server here:
https://arxiv.org/ftp/arxiv/papers/1804/1804.06576.pdf

One of the references in this paper is "INTRINSIC POLARIZATION OF RAPIDLY ROTATING EARLY-TYPE STARS"
It is available for free here: http://articles.adsabs.harvard.edu/pdf/1968ApJ...151.1051H