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1500 questions
27
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5 answers
Can a planet with no atmosphere be orbited at extremely low altitudes?
Can a planet that has absolutely no atmosphere be orbited by a spacecraft at extremely low "altitudes" (if you'd even call it altitude at such a low orbit.
For instance, if this planet's highest peak was 1km above sea level, could a spacecraft orbit…
veezy_101
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27
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3 answers
Why do some electromagnetic waves continue travelling while others disappear?
Cosmic background radiation emitted when the Universe was very young still exists. But my wifi signal seems to disappear a short distance from my apartment. Why?
David
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27
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2 answers
What causes a star to become a pulsar?
What processes does a star undergo to become a pulsar? Does it take a very specific star with a certain set of qualities such as "Just the right mass, diameter, and composition," or is it a freak accident that certain stars live out their remaining…
David Freitag
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27
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2 answers
27
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3 answers
What is the accepted theory as to why Uranus' axis is tilted so severely?
The planet Uranus is another solar system anomaly, where according to the NASA profile has an axial tilt of 97.8 degrees, also considered to be retrograde. This NASA summary "Uranus" suggests the current theory of a large planet-sized impact…
user8
27
votes
1 answer
Why don't (or can't) stars be more than 325 or so times the mass of the sun? What limits their size?
Is there a particular reason why stars cannot grow as massive as they want to?
And why doesn't this limit apply to supermassive black holes?
Kurt Hikes
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27
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3 answers
Why don't the inner moons of Jupiter have tidally-induced volcanism?
Volcanism on Io is caused by the fact that it is tidally heated. There are four moons that are closer to Jupiter than Io with higher eccentricities, yet they don't seem to have any volcanism at their surface. Why isn't the tidal heating enough to…
usernumber
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27
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2 answers
Where do we have it from that the Moon is migrating away from Earth?
I know Neil Armstrong placed a mirror on the Moon and people shoot lasers there which get reflected, thus measuring the time the light needs they can conclude the current distance of the Moon. But the Moon is periodically moving away from the Earth…
Ioannes
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3 answers
Is it possible to detect gravitational lensing of stars behind the Moon?
Eddington waited for a total solar eclipse to happen to be able to observe gravitational lensing of the stars behind the Sun. And nowadays, amateurs can do the same thing.
Of course, the Moon is much less massive than the Sun, so it doesn't bend…
usernumber
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27
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2 answers
Why didn't the Event Horizon Telescope team mention Sagittarius A*?
At the press conference this morning, the Event Horizon Telescope team didn't say much about Sagittarius A*, which was the target many of us have been waiting for.
Is there any explanation anywhere for this omission?
White Prime
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27
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2 answers
Amateur observing targets for binary star systems?
Are there any easily resolvable, binary star, observing targets visible from ~N40°?
I'd like to be able to show, in one observing session, Mizar and Alcor (naked eye resolvable), another with binoculars, and finally one in a small (say, 4 to 6"…
Craig Constantine
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27
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1 answer
Why do satellites arcs end abruptly when observed from Earth
I recently got an app that let me track the ISS. I noticed that during the time it's visible, it disappears before reaching the horizon, and sometimes reappears soon after for a bit.
Can somebody explain to me how the ISS and other satellites orbit?…
Mav
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27
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6 answers
Can we (theoretically) spin the black hole so strong that it will be broken apart by centrifugal force?
I can't imagine the forces involved in black holes' lives. So please, help me to find out, if it is possible or not to destroy black hole in this specific way.
Pavel Voronin
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27
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4 answers
Terrestrial Exoplanet Skies – I've Built a Visual Sky Chart. Is it Accurate?
I'm an artist (and science enthusiast) and I've been trying to find a comprehensive resource that would help me clearly identify likely sky colors (as perceived by human vision) for exoplanets that have atmospheres with a similar chemical…
n_bandit
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27
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3 answers
Does the Sun have permanent geographical features?
Equivalent formulations of this question:
Would it make any sense to draw a map of the Sun?
Is the Sun heterogeneous with respect to latitude and longitude? (I know that it is heterogeneous with respect to altitude/depth)
I know that the Sun does…
Joshua Meyers
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