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1500 questions
22
votes
4 answers
Black Hole / Hawking Radiation: Why only capture anti-particle?
I may have some specifics wrong here. If so, don't focus on those. Just focus on the general thrust of my question.
I "understand" (cough) that particle/anti-particle pairs form spontaneously in space. I understand that they can form near the…
user3355020
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So, what exactly is an 'ultra-cool' dwarf star?
The TRAPPIST-1 system is around an ultra-cool dwarf star. I went looking for more information on that kind of star, and found very little. The Wikipedia article on it lengthened from a minimal stub to one paragraph in the 15 minutes from when I…
kim holder
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22
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Why are wavelengths shorter than visible light neglected by new telescopes?
The diagram below, which I stole from this post by @HDE226868, shows that angular resolution as a function of wavelength suddenly drops by three orders of magnitudes from visible to UV-light. The resolution of wavelengths shorter than what the Very…
LocalFluff
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22
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Does the recent news of "ten times more galaxies" imply that there is correspondingly less dark matter?
Nature: Universe has ten times more galaxies than researchers thought
NASA feature: Hubble Reveals Observable Universe Contains 10 Times More Galaxies Than Previously Thought
Headlines sometimes oversimplify. But if this is really true, that there…
uhoh
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22
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Where does the energy of light go, when it red-shifts?
When talking about the expansion of the universe, it is said that it can be proven by the red-shifting of light.(As we would need higher than lightspeed to get this redshift by the Doppler effect)
I am an amateur, so I am not sure I am correct, but…
akaltar
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22
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Multi-messenger astronomy: what is the potential of simultaneous detection of gravitational waves and neutrinos from a supernova?
Thanks to the efforts of the aLIGO team, gravitational wave astronomy is a reality. At the same time, neutrino detectors like Hyperkamiokande are becoming much more sensitive.
My question is: what are the prospects for the pseudo-simultaneous…
ProfRob
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22
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2 answers
Was the Milky Way ever a quasar?
Is there any evidence that the Milky Way could have been a quasar in it's early history? Is it thought that most galaxies come from quasars?
Stu
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22
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Explaining Dark Matter and Dark Energy to layman
With my little knowledge, I know this:
Dark Matter
The center of a galaxy controls/attracts its objects (stars, planets, comets etc.) towards itself because of gravity. But the mass of the center of this galaxy appears to be less than what it should…
Farhan
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22
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1 answer
Is the moon moving further away from Earth and closer to the Sun? Why?
According to The NASA Moon Facts page:
The moon is actually moving away from earth at a rate of 1.5 inches per year.
Why is the moon moving further away from the Earth? Is this a result of the moons formation that set it in motion to spiral away…
user96
22
votes
4 answers
How Would a Neutron Star Actually Appear?
Having seen many pictures produced by artists of neutron stars and planets that orbit some of them, I was wondering how a pulsar would appear to a human being, in visible light (assuming the intense radiation etc. doesn't kill us in the process).
As…
user10106
22
votes
4 answers
How would the night sky look from inside a globular cluster?
When the weather is clear, we can look at the stars. And we normally would see several thousands of them, they all being more than a $\textrm{pc}$ away from us.
Now, there are globular clusters, which consist of some $10^5$ stars concentrated is a…
Alexey Bobrick
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22
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1 answer
How did Mars come to have a 24 hour 39 minute day?
Mercury rotates three times for every two revolutions around the Sun, apparently due to a gravitational resonance with the Sun.Venus takes about 225 days to rotate, and rotates in the opposite direction of any of the inner planets. Maybe because its…
Howard Miller
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22
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4 answers
Why are galaxies disk shaped?
I always see galaxies in "disk" shape in pictures. It is like, there is a rotational movement on a plane and the system is balanced by the pulling-in gravitational force which prevents the stars to leap out of the galaxy. What is the physical reason…
hkBattousai
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22
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3 answers
Escaping a black hole
I often hear that nothing can escape a black hole because its "escape velocity" is greater than c. If that is accurate, what about the following? I know that the following has a lot of most likely impossible assumptions, but I'm trying to understand…
Mitchell Kaplan
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21
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What are the main differences between solar flares and coronal mass ejections?
Specifically, what causes them, what sort of damage can they cause, and what are the differences in their composition?
David Freitag
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