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### What is the solar diameter?

What is the solar diameter in SI units? Google tells me this is 1.3927 Gm. How accurate is that figure? I am looking for estimates with referenced data and calculations, and the uncertainties: due to ...
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1 vote
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### Does the Sun's atmosphere have a scale height?

Much of the Earth's atmosphere has a scale height $h$ of roughly 7 to 8 kilometers such that the local density varies as $\exp(-(r-r_0)/h)$ where r is the radius vector and $r_0$ would be some ...
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### At what depth below the Sun's surface does the density reach that of water?

I'd like to write a short supplementary answer to A probe floating in Sun's surface but in order to do so I need to know at roughly what depth relative to the Sun's surface the mass density reaches 1 ...
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### Is it ever possible to see Earth's shadow on other planets?

Is it ever possible to see Earth's shadow on other planets? How would the shadow present, and what would be the magnification, equipment, or other conditions necessary to see it? Is there any way of ...
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### Calculate how far we could see through Earth's atmosphere if it had the opacity of the solar photosphere?

I've newly started studying astrophysics. There is a question in the book "An introduction to modern astrophysics" by W. Carroll: Calculate how far we could see through Earth's atmosphere if ...
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482 views

### How to understand exactly why gravity darkening happens on rotating stars?

Phys.org's TESS delivers new insights into an ultrahot world links to KELT-9 b's Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin–Orbit Misalignment (readable in arXiv) The assymetric ...
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758 views

### Precision in the measurement of the distance to the Sun

How precisely can the distance to the Sun be measured? Wikipedia says the distance to the Moon can be measured upto millimeter precision. But Wikipedia article on distance to the Sun says only about ...
218 views

### Accuracy of Mercury transit calculations

What is the error range for calculations for the time of 1st-4th contacts for a given GPS coordinate on Earth? I observed through a telescope the 3rd and 4th contacts and compared against SkySafari ...
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### How is a planet (or star's) radius defined?

The radius of a rocky planet like earth is fairly easy to define based on the fact that the ocean's surface is fairly smooth, and it is a natural point to measure. Other planets like Mars, the surface ...
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