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1500 questions
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Why are there no stars visible in cislunar space?
It’s very puzzling that the moon landing had no stars in the background, the ISS clips have no stars in the background. I listened to multiple astronaut interviews speak on what it looks like up in space and about half of them speak of the “darkest…
Autodidact
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How does the gravitation of Jupiter or other big planets affect Kepler's third law?
Does anyone know a good reference for this?
I once read how Jupiter's gravitation can be treated as a perturbation. I think they expanded Jupiter's gravitation as an infinite sum of one of the special functions (such as Bessel function, Legendre…
Youngsub Yoon
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What is the difference between the Yarkovsky effect and YORP effect?
As far as I understand, both the Yarkovsky effect and the Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect exert forces upon bodies as a result of thermal photon radiation. How do both effects differ from one another?
Nick Silvestri
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Is there any orbit at which the Roche limit can be "felt"?
Do any of the planets have a Roche limit that is strong enough to be felt by an astronaut whilst in orbit?
Muze
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Quasar mass and accretion rates
This page on Wikipedia -- Quasars mentions that the "The largest known [quasar] is estimated to consume matter equivalent to 600 Earths per minute". However, there is no citation for this comment. How can I find out where this information came from?…
Jim421616
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What fraction of a star's hydrogen store will be fused over its lifespan?
A main sequence star will fuse some of its hydrogen, but not all. In massive stars ($>1.5M_\odot$) the core is convective but the rest of the atmosphere radiative and hence does not mix much: as it undergoes shell fusion it will produce an…
Anders Sandberg
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Why does each and every planet of our solar system have an unique axial tilt angle?
Why do planets have an axial tilt? From the above image we can see that each planet's axial tilt angle varies and differs from the others.
What was the cause of this, was this from the beginning of our solar systems birth? Or did it happen later?
Paran
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How long after the Big Bang would CMB radiation have been between 273 and 373 K?
Cosmic microwave background radiation is 2.7 K today. When would it have been between 0 and 100 C?
user332336
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How can we detect water on Mars-like exoplanets?
According to data from Curiosity, Mars' dust holds about 2% water by weight
This wasn't previously detected, so the impression we have had of Mars being incredibly dry may need to be altered. Okay it is still very dry, but there is potentially…
Rory Alsop
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14
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How do I build a stargazing aficionado's Sun funnel to observe our nearest star safely?
How do I observe the Sun safely, with tools I could build myself and without breaking the bank? If I wanted to build a Sun funnel on my own and use it on my enthusiast grade telescope, how would I do that?
What supplies and tools would I need, how…
TildalWave
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How can tidal heating lower Io's orbit?
This answer to the question Is Io a magic energy machine? suggests that the energy from the internal heating of Io due to tidal "squishing" as it moves cyclically closer and farther from Jupiter in its elliptical orbit will come from the energy of…
uhoh
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What azimuth description systems are in use?
For a time, I thought Azimuth is always direction in degrees, 0 for local, geographic north, 90 for east etc.
Then, trying to observe moonrise I downloaded an app that gave azimuth in values between (if I recall correctly) -180 and 180, and I think…
SF.
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If Earth didn't rotate, would we feel heavier?
Suppose the Earth's rotation slowed for some reason. Would the lack of centrifugal force cause us to feel heavier than normal?
Likewise, if Earth's rotation increased, would we feel lighter as centrifugal force lifts us from the ground?
Spinmeister P
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How did the lighter elements end up in the center of the solar system? Solar System Formation
The previous generation of stars famously are the origin of all the heavier elements (up until iron?) in the solar system. So a big portion of the solar system mass actually is made up of Carbon, Silicon, Iron and the like because of that. But in…
lthz
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Is it possible neutron stars are actual elements?
As you go up the periodic table (more protons), the ratio of neutrons to protons steadily increases as well. Are we sure there are absolutely no protons and electrons in a neutron star, or could there be so much more neutrons that we cannot measure…
