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1500 questions
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Why did astronomers believe most or all stellar black holes had masses no greater than 15 solar masses?
The so-called 'mass gaps' for black holes, according to theoretical models, are between 2-5 solar masses and 50 to 150 solar masses. (Actually, I have read that there is no good theoretical reason for the lower, 2 to 5 solar-mass gap....)
But, I…
Kurt Hikes
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What is the longest natural bound orbit chain observed?
Define a bound orbit chain as a list of successively less massive bodies, each in a bound orbit with the bodies preceding it in the list.
Then an example of a bound orbit chain would be: , since the Earth orbits the Sun, and the…
Connor Garcia
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How much water on the earth is made from hydrogen comes with solar wind?
A great fraction of solar wind is protons or Hydrogen ions. Some part of it is captured by Earth. I am wondering how much water in my half a liter cup is made of hydrogen from the Sun.
ZAB
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How far apart is the dust in the Sombrero Galaxy's dust lane?
In his answer to this question, TildalWave made this remark:
I think that first, we have to properly appreciate the size of the Sombrero Galaxy. It is roughly 50,000 light years (15 kilo parsecs) in diameter. That might be only half of the diameter…
user19
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1 answer
How to measure mass of planets' core from orbit
I am told in an astrophysics lecture the following.
The mass of Saturn's core was measured by Cassini when it completed its final flyby between the rings and the planet itself. It was also found that its core has a sharp boundary.
Juno measured the…
zabop
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Why do people choose 0.2 as the value of linking length in the friends-of-friends algorithm?
The friends-of-friends algorithm (hereafter FOF) is commonly used to find halos in cosmological simulations. And FOF depends on only one parameter, linking length, $l_\mathrm{link}=b \left(\frac{V_u}{N}\right)^{1/3}$, where $V_u$ is the volume of…
Wang Yun
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Is there convection in Mars' mantle?
Mars is differentiated, with a core, a mantle and a crust. There are no (longer any) plate tectonics on Mars. Does this mean there is no convection in the mantle? Could there be convection in the mantle without it causing plate tectonics?
usernumber
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Where did the hydrogen come from in a type II supernova?
Type II supernovae have hydrogen. Where did the hydrogen come from if that is the first element used up in the star's life cycle? Also if our solar system was seeded from an ancient supernova where did the sun's hydrogen come from?
J.P. MacAllister-Knox
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Has the Earth-facing side of the Moon that we see today always faced us ever since the Moon got tidally locked? Or does it precess?
Title. Does the Earth-facing side of the Moon slowly precess due to perturbations and torques exerted by other bodies? Or is the side of the Moon we see today the same as when it first got tidally locked?
P.S. I know we don't see the exact same side…
user177107
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Why has Saturn stopped contracting gravitationally?
The following text is from here:
The Jovian planets get their heat from the Sun and from their
interiors. Jupiter creates a lot of internal heat and releases this
heat by emitting thermal radiation. In fact, Jupiter creates so much
internal heat…
Nilay Ghosh
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12
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1 answer
Are there auroras on Mercury?
Auroras on Earth are caused by interactions between the solar wind and the magnetosphere. I've also seen a few pictures of auroras on Jupiter and Saturn.
Mercury has a global magnetic field. Does it also have auroras? If so, what do they look like?
usernumber
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4 answers
How much does the sky change in a few thousand years?
The "fixed stars" are not actually fixed, the earth's tilt changes over time etc., but all that happens slowly on human timescales.
Imagine a Babylonian astronomer (or astrologist?) teleported to the present, e.g. to present-day Iraq. Would she be…
Toffomat
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When the sun "enters" a constellation, doesn't it make it impossible to see that constellation?
I was reading on NASA's website about how the Babylonians came up with dividing the sky into different slices and picked a pattern of stars in each slice to represent it. This ties in to astrological signs, and that being born "under" a sign means…
Magnus
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Why do gas giants have clearly delineated surfaces, whereas the Earth's atmosphere fades into space?
I've just seen this Forbes article.
Why do gas giants appear to have clearly delineated surfaces, whereas the Earth's atmosphere fades into space?
Is it just a matter of scale? Or is there some form of "surface-tension" for the hydrogen gas?
fadedbee
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Is there a relation between mass, radius, and luminosity in deuterium-burning brown dwarfs?
I'm a worldbuilder and my setting has a lot of brown dwarfs.
While I'm trying to keep my setting as science-compliant as possible, I can't seem to find any resources for brown dwarfs like there are for main sequence stars, just basic encyclopedia…
TerranAmbassador
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