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1500 questions
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From where does the energy for gravitational waves come from?
As far as I understand, in the events detected by LIGO, about 4% of the total mass of merging binary black holes was converted to gravitational waves.
Where does this energy come from, i.e. what exactly gets converted into gravitational waves?
Is…
tuomas
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Why is Enceladus's albedo greater than 1?
Enceladus, one of Saturn's moons, has a geometric albedo of 1.38 and a bond albedo of 0.81. How can the geometric albedo of Enceladus be greater than one? What are the similarities or differences between a geometric albedo and a bond albedo?
Cyclopropane
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Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?
My understanding is $\sim$ generally means "on the order of magnitude of" e.g. $T \sim 10^5$ K
$\approx$ is obviously "approximately equal to" so for example one might write $d \approx 400$ pc rather than $d=4 \times 10^2$ pc
$\simeq$ and $\cong$,…
imanorc
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12
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Are the Trappist-1 planets in stable orbits?
The Trappist-1 planets all orbit very close to each other. During NASA's press release, they mentioned that these planets are close enough to disturb each others orbits. Is this system stable over a long time scale? Or could we perhaps just have…
Phiteros
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12
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5 answers
What mechanism causes oscillations of the solar system's orbit about the galactic plane?
In a recent paper (news release here) Lisa Randall and Matthew Reece propose that a dark matter disk coinciding with the galactic plane together with the solar system's oscillations through the galactic plane could explain the 35 million year…
Chris Mueller
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12
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Is it possible to figure out your location in the Milky Way if you are suddenly wormholed to a random, distant location in the galaxy?
If you were flying along in your spacecraft somewhere in our solar system and then a large, stable wormhole suddenly opened and you flew into it and were whisked away to some distant location in the galaxy, would you be able to figure out where you…
Arbutus
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Why are most planetary orbits nearly circular
In our solar system, with the exception of Pluto all planets follow a relatively circular orbit around the Sun, at the same inclination. They also all rotate in the same direction, none are 'retrograde'.
An image of the orbits of our solar…
Vedant Chandra
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12
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What's the farthest object as determined only by parallax?
I'm wondering what the farthest object we know of, as measured only by parallax methods, from either earth or satellite based telescopes, and at either visible light or radio wavelengths.
Basically, if we had no other way of measuring distances,
…
Nathaniel Bubis
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How to discover Neptune from the Uranus orbit (by computer simulation)
I would like to demonstrate the existence of another planet (Neptune) by studying the discrepancy between the observation of the Uranus orbit and the mathematical prediction, this work was made from Le Verrier and I would like to understand his…
Sergio Piccione
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Why don't we have in-between planets?
The planets in our system are most often grouped into two categories:
Terrestrial:
Mercury
Venus
Earth
Mars
Gas Giants:
Jupiter
Saturn
Uranus
Neptune
Why is it that we don't see "in-between" planets in our system - large, rocky worlds larger…
Zxyrra
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12
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2 answers
Why don't we see "the milky way" in both directions?
We're (basically) in the middle of an arm of our galaxy. That is to say, we're sitting in the middle of a dense disc of stars.
It would seem to me that. You should see:
the thick line of the milky way all around you, i.e. on that plane, in all four…
Fattie
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How strong is the force between the Sun and the centre of the Milky Way?
I know the Sun is orbiting around the Milky Way, but how strong is the attractive force between them (e.g. what is the order of magnitude in terms of newtons)?
Gstestso
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When did the Moon become tidally locked to Earth?
According to various theories the Moon was created around 4.5 billion years ago. About all of these theories suggest that it was rotating around its axis at that time though. Currently, Moon is at tidal lock with Earth, despite some monthly…
SF.
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12
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1 answer
Energy deposition in planet Earth due to gravitational waves
The gravitational wave detected by the LIGO observatory acted on planet Earth streching and shrinking it a little bit. I assume that not all of this action was fully elastic and that some energy of the gravitational wave was lost by the passage…
Sir Cornflakes
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12
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Milky Way position on the sky
I'm looking for some sort of boundary data to be able to render the milky way on a star map, as visible from Earth. Something that looks like this:
For that, I need something like a collection of RA hours and DEC degrees of the "boundary points" of…
gphilip
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