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11 votes
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Why are asteroids with zero orbital inclination rare?

Short answer: The scarcity of asteroids with an inclination near zero is an expected result of normally distributed inclinations in 3-dimensions about the normal vector to the reference plane, rather ...
Connor Garcia's user avatar
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10 votes
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At what point are orbital resonances no longer "ordered" but "chaotic?"

Consider a child on a stationary swing. The fastest way to get them going is to push once every time they swing (a 1:1 resonance). If you push 581 times for every 137 swings, the pushes will mostly ...
Connor Garcia's user avatar
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9 votes

What exactly was the Moon's "Evection Resonance"?

The orbit of the moon is elliptical. But the direction of the major axis of this ellipse isn't fixed. Perturbation by the sun causes the axis to rotate towards the East. The time for the moon to go ...
James K's user avatar
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9 votes
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Planetary orbital resonances

This is actually a very subtle question, much more so than the answers to the similar questions provided in the comments give it credit for. When I was in graduate school at Ohio State I routinely ...
J. O'Brien Antognini's user avatar
9 votes
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How do tadpole, horseshoe co-orbital states arise and how are they stable?

If the body is in front of the planet (relative to the planet's orbital motion) and a little further from the sun, it will orbit the sun slightly slower than the planet. As it is slower, the planet ...
James K's user avatar
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8 votes

Orbital resonance and the precession of the periapsis

The revolution period of a body is the time it takes to return to pericenter. So, for example, Io will return to its perijove after 1.769 days, and Europa to its own perijove after 3.551 days. But ...
Pierre Paquette's user avatar
6 votes

Why are asteroids with zero orbital inclination rare?

In spherical polar coordinates, one of the coordinates used is an angle between the direction to a point in space and a "pole". Let this "pole" be the ecliptic north pole and call ...
ProfRob's user avatar
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6 votes

Can a solar system exist where the second planet rotates fast, and the third planet is tidally locked to their star?

The tidal locking timescale depends on several factors: $$\tau_{lock} \approx \frac{0.4 \omega_0 a^5 m Q}{3 G M^2 k_2 r^3}$$ such as the initial spin rate $\omega_0$, the semimajor axis $a$, the mass $...
Anders Sandberg's user avatar
5 votes
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When will Callisto be in orbital resonance with the rest of Jupiter's big moons?

we tried to answer to this question in this article: https://arxiv.org/abs/2001.01106 According to the current estimation of the tidal dissipation in the Jovian system, we expect that Callisto will be ...
Jerle's user avatar
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5 votes

What exactly was the Moon's "Evection Resonance"?

Does this simply mean that the angle formed by the Sun-Earth-Moon when the Moon was at perigee was the same every month? No. It means that one Earth year after the Moon was at perigee, the Moon would ...
David Hammen's user avatar
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5 votes
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How can orbital resonance sometimes have a stabilising effect, whilst other times, it has a destabilising effect?

According to my understanding, for an orbital resonance to be stable, there must be at least three circumstances present: The forces on the bodies in resonance have to cancel out over time, The ...
Jan's user avatar
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5 votes
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Why does the exoplanetary system TOI-178 challenges current theories of planet formation?

The original research paper is published is found on A&A and available via arxiv, too. One of the mysteries to understand in planet formation is the distinction between terrestrial planets and ...
planetmaker's user avatar
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5 votes
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Is it still called an orbital resonance if the ratio is irrational?

From various sources such as Wikipedia, NASA, and various published papers, an orbital resonance is: when orbiting bodies exert regular, periodic gravitational influence on each other, usually ...
zephyr's user avatar
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4 votes

Just how "locked" are resonant-chains of exoplanets thought to be? (e.g. K2-138 and TOI-178)

Short Answer: MMR (Mean Motion Resonance) chains seem to be mostly unstable over the lifetime of a planetary system, since we suspect most planetary systems begin in some resonance lock, but we ...
Connor Garcia's user avatar
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4 votes

Why are asteroids with zero orbital inclination rare?

I'll propose that it can be understood trivially. What would the inclination distribution of circles randomly distributed in three dimensions about some point? We could generate them by distributing ...
uhoh's user avatar
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4 votes
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What exactly are the "ν6 secular Sun-Jupiter-Saturn" and the "1:4 Sun-Jupiter" resonances?

The 1:4 (or 4:1) Jupiter resonance is a mean-motion resonance: an asteroid there takes 1/4 as long to orbit the Sun as Jupiter does. Perturbations by Jupiter at recurring ecliptic longitudes alter the ...
Mike G's user avatar
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4 votes
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Mercury's spin-orbit resonance

The first accurate determination of the rotation period and the first hints that the rotation period was different from the orbital period (as originally expected) was in 1965 from 430 MHz radar echo ...
astrosnapper's user avatar
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4 votes

Relative orientation in a 1:1 resonance of a planet and a satellite

The mean motion $n$ and the time-derivative of the true anomaly ${\nu}$ are related by $$ n\,=\,\frac{(1-e^2)^{3/2}}{(1+e\cos \nu)^{2}}~\dot{\nu}~~. $$ Therefrom it is clear that in the pericentre (i....
Michael_1812's user avatar
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4 votes

Could a planet or its moon be synchronously tidally locked with the sun, but still in orbit with its moon/planet?

The negative (decelerating) tidal torque of the star is trying to synchronise the planet's rotation with its mean motion $n_p$ about the star. (Rare exceptions are close-in planets with a high ...
Michael_1812's user avatar
  • 1,486
3 votes

Could a Trappist-like planetary system exist around a sun like ours?

That is a fascinating question due to the fact that planetary orbits have both absolute and relative spacing. The absolute spacing between planetary orbits is the number of kilometers that the semi ...
M. A. Golding's user avatar
3 votes

Hypothetical planet jump: Will it perturb star systems?

There is essentially no room in our habitable zone for another Earth-sized planet. The exact timescale for instability would depend on the details of where you put it, but the system couldn't survive ...
Eric Jensen's user avatar
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3 votes
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How do higher numbers affect orbital resonance?

General Explanation In the history of our Solar System, the orbits of Solar System bodies have gradually evolved, passing through many "higher number" orbital resonance ratios. Only the ...
Connor Garcia's user avatar
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3 votes
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Are there other possible Laplace resonances? (e.g. 1:3:9)

The Wikipedia article you linked contains several other examples, both in our own Solar system, e.g. 18:22:33 for some of Pluto's moons, as for exoplanets. There are all kinds of ratios to be found (...
Glorfindel's user avatar
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3 votes

How do tadpole, horseshoe co-orbital states arise and how are they stable?

How, when approaching the planet, does the body "fall behind" instead of continuing to accelerate toward the planet? This is fundamentally the gravity assist problem. In the 2 body system, the ...
userLTK's user avatar
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3 votes
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Explanation of resonance stability and instability

Mercury and Spin-orbital resonance is pretty straight forward. Planets and Moons are gravitationally lumpy and large bodies are somewhat fluid, even rocky bodies. Both aspects are prone to tidal ...
userLTK's user avatar
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3 votes
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Is this a stable system?

Seems like it would be subject to Kozai oscillations at least-- see https://www.cfa.harvard.edu/research/ta/kozai-lidov-mechanism. That mechanism tends to swap obliquity for eccentricity, without ...
Ken G's user avatar
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3 votes

Orbital eccentricity variation of the other planets?

You may take a look at the lates parametrization file by JPL-NAIF for the precession, nutation and pole orientation of the largest known bodies. Although, for the large time scales you are asking, I ...
Ela's user avatar
  • 116
3 votes

Where can I build my house on Mercury so that I can see double sunsets (and sunrises)? Can I do it near the poles where it's cooler?

A quick look at Stellarium (if we trust its accuracy) suggests longitudes ~90 east and west (Edit: it seems that each of these corridors get to enjoy both double sunrise and sunsets, not only one or ...
we'll see's user avatar
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