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30 votes
Accepted

The newly discovered comet NEOWISE has been given the name C/2020 F3. What is the meaning of the F3 and the C in this name?

C means "comet": it has a coma which means that volatiles are being released due to solar heating. Other possible letters are "A" for asteroid, "P" for (short) periodic ...
James K's user avatar
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20 votes

What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?

The formula for orbital velocity is $\sqrt{GM/r}$ and for a "low" orbit you would mean orbit at, or close to the surface, ie with a radius equal to the radius of the planet. This makes ...
James K's user avatar
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10 votes

Does the Giant Impact Hypothesis explain how the Moon circularized its orbit?

I want to point out that the Moon's orbit isn't circular now. A 0.055 mean eccentricity isn't that circular. But, onto your question. I think you're making a bad assumption on the "must have ...
userLTK's user avatar
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9 votes
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How to mathematically describe a planet's eccentric orbit?

The formula is Kepler's equation, but to understand it you need to know three values: $M$ is the "Mean Anomaly". It increases linearly from 0 to 360 over the period of one orbit, measured from ...
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
7 votes

Why didn't Johannes Kepler use data about more planets?

Kepler could, with a lot of work, apply his analysis to other planets of course - but it won't help in proving his point of elliptical path. There are only two planets where this elliptical path could ...
d_e's user avatar
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7 votes
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Kepler's equation and eccentric anomaly

Both formulae are correct. The discrepancy is because the formula from the eccentric anomaly article uses the centre of the ellipse as the origin, but the formula from the Kepler's equation article ...
PM 2Ring's user avatar
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7 votes

What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?

"Low-Earth-Orbit" is kind of arbitrarily defined, and I don't believe there's a widely accepted general definition of a low orbit that can be applied to other planets. If you know what the ...
toxicPsychotic's user avatar
5 votes
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Lagrange points for bodies in elliptical orbits?

One of the answers to the researchgate question What are the equation of motion for elliptical restricted three body problem? says: https://www.sciencedirect.com/search?qs=equation%20of%20motion%...
uhoh's user avatar
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5 votes
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How can I find the width of an orbit knowing some values?

To find the width (semi-major axis, see Wikipedia) of an orbit, you only need two of the following: perihelion, aphelion, and eccentricity, represented by the variables $P, A, $ and $e$, respectively, ...
WarpPrime's user avatar
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5 votes
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Can the Moon provide momentum to an object in Earth's orbit? Gravity Assisted Boost

The Moon has a "Roche lobe", where the Moon's gravity dominates, and all you need for the situation you describe is that the Roche lobe lies physically outside the Moon. That will be true, because ...
Ken G's user avatar
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5 votes

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

The maths says that the semi-major axis is not a good measure of average distance for high eccentricity (elliptical) orbits. There are basically two ways to measure this : (1) an average over the ...
StephenG - Help Ukraine's user avatar
5 votes
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Velocity Verlet algorithm creating odd orbits

I'm not a Java coder, but it looks like you aren't implementing the velocity Verlet algorithm correctly. You need to update the velocity vector with the mean of the old acceleration and the new ...
PM 2Ring's user avatar
  • 14.8k
4 votes

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

Just to provide an analytical formula for @uhoh's correct time-averaged distance, here the derivation of $\langle r\rangle_t=1+\epsilon^2/2$: $$a=1 \qquad c=e\qquad b=\sqrt{1-e^2}\\ \vec{r}=(\cos \...
Markus Schmassmann's user avatar
3 votes

Why are asteroids with circular orbits rare?

Orbital eccentricities cannot be normally distributed around zero, since the minimum eccentricity is zero. Thus, in the same way that the Maxwell-Boltzmann distribution for particle speeds is zero at ...
ProfRob's user avatar
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3 votes

Is the process responsible for Triton's nearly perfect circular orbit going to happen in my fictional world?

Tidal circularisation is produced by a combination of tidal dissipation in the planet and that in the satellite. Calculations performed for the Jovian and Saturnian moons inducate that for them the ...
Michael_1812's user avatar
  • 1,456
3 votes

What is the difference between barycentric-centered and heliocentric-centered coordinates?

Inspired by this excellent question,I found this page that describes the issue in some detail for non-specialist readers. If I'm not botching the explanation, the reason for the difference is that ...
antlersoft's user avatar
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3 votes

Does the Giant Impact Hypothesis explain how the Moon circularized its orbit?

Does the Giant Impact Hypothesis explain how the Moon circularized its orbit? No, it does not. The giant impact hypothesis says that the Moon formed a handful of Earth radii from the center of the ...
David Hammen's user avatar
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3 votes

Does the Giant Impact Hypothesis explain how the Moon circularized its orbit?

Well, I don't really think the GI Hypothesis can answer the orbital plan of the moon, I would say that the circular orbit of the moon today regarding the GIH is also due to other variables, like ...
Michael P. Jouanneau's user avatar
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
2 votes

Actual observable horizon for satellites on an orbit line map?

My first thought would be that the apparent path of a satellite across the sky can appear to turn even when it is straight. Your brain doesn't easily understand straight lines in all cases. (Look up ...
BowlOfRed's user avatar
  • 2,085
2 votes

Actual observable horizon for satellites on an orbit line map?

It is not that satellite. As it passes over Finland, it has an altitude of 27000km and a magnitude of about 12. You won't see it. All Molniya orbits are similar. The website Satflare to shows the ...
James K's user avatar
  • 123k
2 votes

Would we be able to feel the acceleration of a planet with a highly eccentric orbit?

No. While you're on that planet, you are also in the same orbit around the star as the planet is. As long as you're in the same orbit as your vehicle (planet, spacecraft), you don't experience any ...
Florin Andrei's user avatar
2 votes

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

This was intended to be a supplemental answer to StephenG's answer. However, there appears to be a problem with the expression for time-averaged distance in that answer. I think it's great to seek a ...
uhoh's user avatar
  • 30.7k
2 votes
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Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

The gist of this, is that your assumption is incorrect. It's the semi-major axis that defines the period, not the average distance. Newton worked this out when he invented calculus and derived ...
userLTK's user avatar
  • 24.1k
2 votes
Accepted

snapshot of solar system

You can get a position and velocity snapshot easily using the Python package Skyfield. It downloads a JPL Development Ephemeris and then interpolates the positions for whatever time you choose for ...
uhoh's user avatar
  • 30.7k
2 votes

Neptune's eccentricity stability

tl;dr: It will be around the year 14,800 that Earth's eccentricity drops below that of Neptune's. It's unusual to post two answers, but this one is sufficiently different that in this case I think it'...
uhoh's user avatar
  • 30.7k
2 votes

Neptune's eccentricity stability

Earth's Eccentricity varies between about 0.000055 and 0.0679. This is the first Milankovich cycle. When Earth' eccentricity is at its lowest, it is lower than that of Neptune. The Earth's orbit ...
James K's user avatar
  • 123k

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