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12

The same reason (almost) all of them rotate in the same direction: because of the conservation of angular momentum. Before a star and its planets exist, there’s just a cloud of disorganized gas and small molecules. The Solar System formed from such a cloud around 4.6 billion years ago. On that scale, there is some small amount of rotation within the cloud....


7

The moon is gravitationally locked to the Earth. Because gravitational field depends on distance, the Earth's gravity does not affect the moon uniformly: the farthest side is not attracted as strongly as the closest side, these are tidal effects. This causes the heaviest side of the moon to face the earth, i.e. the moon is tidally locked to the earth. The ...


6

The sun is slowly losing mass, partly from the conversion of mass to energy (which then escapes as neutrinos and light) and partly from the solar wind (particularly in coronal mass ejections). Solar wind accounts for a loss of about 1.5 million tons per second, fusion accounts for 4 million tons per second. However compared to the mass of the sun (about 2 ...


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I worked out the math, it's pretty straight forward. If we take the Hill sphere, which is an estimate for the furthest possible orbit, and I'm going to just run the math on circular orbits. Eliptical orbits are harder to put in resonance anyway. the simple Hill Sphere formula. $3\frac{r^3}{a^3} = \frac{m}{M}$, where $a$ is the semi major axis planet to ...


5

In a simplified sense, yes. Relative to the sun, the Earth moves at approximately 30 km/s. So if we could launch a rocket in the opposite direction of Earth's rotation at 30 km/s, it would have a velocity of 0 relative to the Sun, and would be accelerated directly towards it ("falling towards it"). This assumes that a rocket could be accelerated to 30 km/...


4

As the Sun's mass is reduced and it's gravitational attraction is thus reduced the Earth will slowly spiral out from the Sun and yes slow down (to preserve angular momentum). But the effect is ridiculously small (do the math yourself) it will not be measurable directly.


2

Nothing in your description sounds wildly implausible. I'll just go through and extend some of your properties to make sure they make sense though. The planet has three times Earth's mass I'll assume that your new planet is Earth-like in composition and density. That implies that it's radius should be about $R_p \approx 1.4 \: R_\oplus$. Let's put that ...


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I see no reason why this wouldn't work. The innermost Galilean moons are in a 1:2:4 resonance so it's clearly a stable orbital configuration. They could all be tidally locked if you want, but the planet itself can't be tidally locked with all of them. If the planet were tidally locked it would likely be locked with the innermost moon. Also of note, the ...


2

The apparent motion of planets is complex but predictable. The apparent motion is due to the combination of three different motions: The rotation of the Earth, the motion of the Earth around the Sun, and the motion of the planet around the Sun. The Planets move in ellipses, slightly perturbed by other planets. These motions are predictable, and ...


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NO The differences between a brown dwarf and a low mass star are based upon their mass. A brown dwarf does not have central temperatures and pressures to create energy using hydrogen fusion. The mass is too low to create these conditions. A star by definition is an object where energy is created using hydrogen fusion. This happens when the core temperature/...


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Yes If a brown dwarf count as a star in this case, the solution is as easy as a smaller brown dwarf orbiting a larger one. If not, it is still possible if you have two brown dwarfs orbiting close to each other, both just too small to be red dwarfs, together out-massing an orbiting red dwarf, just large enough to be counted as a star. While I have no ...


1

I guess that depends on how much radiation they're getting. I should also point out that astronauts are not 100% protected from radiation, as discussed in this question. One of the most common affects on actual astronauts is the development of cataracts. They can also receive damage to their nervous system over time, among other effects. But it appears that ...



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