# Questions tagged [orbital-elements]

Questions about the parameters needed to specify the characteristics of an orbit.

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### Orbit equation solver giving wrong orbits

Recently I've become interested in simulating orbital mechanics using Kepler's equations, and in Unity I created my own equation solver by following this paper I found. However, inputting Earth's ...
1 vote
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### Does the inclination of an orbital plane change due to pull from other orbiting objects?

I don't mean precession. That's drift in the orbit around the center. I'm asking about drift of the tilt in the z-direction. Saturn's ring particles are held in a tight disk because when they drift ...
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### Is angular velocity of line of apsis equal to $\frac{d\omega}{dt}$ or $\frac{d\varpi}{dt}$ or something else?

As I understand it, the terms apsidal precession and nodal precession refer to the quantities $\frac{d\omega}{dt}$ and $\frac{d\Omega}{dt}$ (by definition). But what is the angular velocity of the ...
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### Why is rate of apsidal precession not consistent with the first time derivative of the argument of periapsis

The Wikipedia page on apsidal precession states that the rate of apsidal precession is the first time derivative of the argument of periapsis ($\omega$), which is related to the longitude of ascending ...
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### Finding the cartesian position of the lunar ascending node

What I'm trying to derive The cartesian position of the lunar ascending node relative to the true equator and equinox of date reference frame. My issue is I'm getting a bit tripped up with reference ...
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### Kepler to Cartesian and Cartesian to Kepler inaccuracies

I am programming a computer simulation set in a star system. I've used Rene Schwarz's wonderfully concise memorandi explaining converting from Kepler orbital elements into cartesian coordinates and ...
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### Is it possible to determine orbit orientation of exoplanet without direct imaging and astrometry?

Is it possible to determine orbit orientation (in space) of an exoplanet without direct imaging or astrometry (for example with transits and rv observations only)? I have read somewhere that orbits ...
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### Calculating Ephemeris from JPL Osculating Element

I've built some open source software that calculates Ephemeris from JPL osculating elements to simplify imaging and tracking of Comets, Asteroids, and Near-Earth bodies. This works very accurately a ...
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### Can there be multiple periapsides?

Consider the following image of a barycentric orbit of a binary star system. I could draw their relative orbits by drawing a line connecting both bodies at each point in their rotation. In this ...
1 vote
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### What is the duration of a year on the Moon (Tropical/Sidereal period) for orbit about the Sun ? How/why does length of lunar days vary ? Soltices?

The inclination of the lunar equator to the ecliptic is 1.543°. Synodic period or Length of a day on the moon = 708.7344 hours Moon Fact Sheet 100 Lunar Days - Parts I and II
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### Are the rotational axes of Earth and Mars parallel?

So I was stuck on a question involving the transformation of coordinates from geocentric to Mars-centric coordinates. The relative position of Mars and its orbital details are given. I thought that we ...
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### Code for Gauss's method orbit determination

I'm trying to calculate the state vectors of the ISS using Gauss's method with three sets of values (right ascension, declination and sidereal time). I'm following the method described in "...
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### Why does the tropical year have a ~161 years cycle?

Using PyEphem, I calculated the time difference between consecutive summer solstices in the south hemisphere for the last 4000 years, and plotted them in a graph. It seems like random noise around the ...
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### Find position of orbiting body along orbit efficiently

I'm coding a game, and a fundamental mechanic is celestial bodies moving in elliptical, Keplerian orbits around a single gravitational point in a planetary system (not our solar system). The bodies ...
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1 vote
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### Calculating the parameters of binary systems?

If I know the masses of the two bodies (they have equal mass), how do I calculate the two ellipse eccentricities, length of the apoapsis and speed at the apoapsis, that make stable system, as in this ...
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### Orbital period of a planet orbiting Delta Pavonis in habitable zone

I'm continuing my inquiry about the fictional planet I have described here: https://worldbuilding.stackexchange.com/questions/231162/length-of-seasons-on-a-planet-with-eliptical-orbit. I'm now settled ...
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### Is there an orbit around the earth that experiences a total solar eclipse by the Moon at least every month?

Is there a way to design an earth orbit so that it passes through the Moon's umbra with greater frequency than total solar eclipses occur on earth's surface? What is the maximum frequency of eclipses ...
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### How do times of lunar standstills vary over time? If we folded them back into a lunar month plot, would they have "prograde and retrograde motion"?

The recent question Are lunar phases and lunar standstills in sync with each other? brought me to a standstill because I don't fully know what a lunar standstill is. It's one of those words like "...
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### Time of comet at perihelion query

In Practical Astronomy With Your Calculator Or Spreadsheet by Duffett-Smith and Zwart, the authors write (in relation to calculating cometary positions): The longitude of the comet is not usually ...
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### A couple of questions about Earth's hypothetical planetary rings

From what little I know of this subject, It should be possible for Earth (Or a planet the size of Earth) to keep a system of Planetary Rings. However, looking around the internet only gives me info ...
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### Help me better understand how the plane of Moon's orbit around Earth behaves

Is the plane in which Moon orbits around earth, inclined with respect to earth's equatorial plane? If yes, is it constant or does it change with time? If it changes, how much time does it take to make ...
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### What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?

I was pondering this question recently, but most sites I can find only mention the speeds/velocities of the planets around the Sun when I look for 'orbital velocities' of the planets. I tried ...
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### What is the relationship between true anomaly and solar longitude?

So, my ultimate objective is to map solar longitude values onto a pseudo-Gregorian calendar. I thought this would be simple, but it has turned out to be anything but. I have asked several questions on ...
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### How to determine the time of periastron passage (T) of a single lined spectroscopic binary?

I am working on finding spectroscopic elements of a single lined spectroscopic binary. All I have is irregularly spaced radial velocity data which needs to be phase folded to plot a velocity curve (RV ...
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### Earth-Moon Barycenter Perihelion

I am trying to implement an algorithm I created to get the sun rise, transit and set accurately, but in order to do that I need to get the Earth-Moon barycenter (EMB) perihelion, and not the Earth ...
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1 vote
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### Planet's distance data from JPL Horizons - Mars Curiosity mission

I am looking for distance measurement in AU between planets and Earth. E.g. For Mars, Current distance, or distance of Mars from Earth at any given datetime, along with minimum (closest approach), ...
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### Why is the L1 point (Lagrange) almost 1 million miles from Earth? Shouldn't it be closer to us?

Try to follow my simple logic: The Sun is almost exactly 333,000 times as massive as Earth, and gravitational strength increases linearly with mass, so the Sun's gravity is about 333,000 times ours. ...
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### What is the difference between inclination and obliquity?

I'm trying to understand the differences between obliquity and inclination when it comes to a system of a planet orbiting a star. From what I understand, obliquity is the angle between the orbital ...
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### Is the science in "Don't Look Up" realistic?

In the new movie "Don't Look Up", astronomers discover a comet in the outer Solar System that's going to hit the Earth about 7.5 months later. I think they calculate its trajectory within a ...
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### Post-Keplerian orbital parameters; is there a generally accepted set with definitions?

Strong-Field Gravity Tests with the Double Pulsar is a pretty big deal! 16 years of precision timing including "timing parallax" via VLBI has provided a dataset for which analysis requires (...
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### Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?

If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles.... BUT, it is the precession of the periapses that is off, not 'just' its ...
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### How does NASA figure out orbital period and mass data for planets and other celestial bodies?

Does NASA calculate orbital periods using Kepler's Laws, or do they measure and observe it in some way? If the latter, how do they do so? Similarly, does NASA calculate the mass of bodies using Kepler'...
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### Using Kepler's 3rd law to calculate $\mu$ (standard gravitational parameter)

I'm trying to calculate $\mu$ (the standard gravitational parameter) with this formula $\mu = 4\pi^2a^3/T^2$ I'm using Earth's orbit is $a=1$ and $T = 365.2564$ for $a^3/T^2$ I'm getting $\approx7.496$...
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### Could Planet X have a perihelion much closer than 300 AU and still be responsible for the gravitational interaction with 19 TNOs?

In August, Michael Brown and Konstantin Batigyn proposed new data concerning the hypothetical Planet X to explain the orbits of the 19 TNOs. They suggest a perihelion of 300 AU, but might Planet X be ...
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### Confused on how you are supposed to calculate eccentricity without apsides

I'm kinda confused on how to calculate either the apsides or the eccentricity without knowing one or the other. Let's say you have an object in orbit around another. If you know the current distance, ...
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### Have we indirectly measured GW driven orbital decay in anything besides binary pulsars?

Binary systems decay for all sorts of reasons. I'm asking specifically about orbital decay due to gravitational wave emission. All of direct GW detections of binary systems have come with orbit ...
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### How to translate from local laplace plane to ecliptic J2000 (or ICRF)

The NASA JPL websize gives mean orbital elements for e.g. Iapetus or Titan in relation to the local laplace plane. ...
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### What's the formula for change in argument of periapsis over time due to J2 perturbations for a geocentric satellite?

I'm trying to propagate the orbit of the ISS, but it became very clear to me very quickly that the J2 perturbations were nothing to scoff at. A quick google search gave me the equation for the change ...
62 views

### Precision of orbital period of exoplanets vs solar system planets (Extrasolar Planets Encyclopedia)

I noticed that the Extrasolar Planets Encyclopedia lists the orbital period of L 98-59 b in days to 7 decimal places. Can astronomers really measure orbital period of exoplanets to greater precision ...
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### What are the values of the Mean Anomalies of the planets in the Solar System?

I am trying to find a list of all the Mean Anomalies of the planets in the Solar System at the Epoch Jan 2000. I tried to Google it up but couldn't find any result. Can you please share the values or ...
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### Querying MPC data : P and Q vectors of any use to compute the eccentricity vector?

While querying the Minor Planet Center orbital data for asteroids, among the returned data, I noticed 6 variables corresponding to x,y and z components of two 3-D vectors namely P and Q. The ...
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### Mars is getting closer to Earth through its elliptical orbit becoming more eccentric. Do Earth and Mars keep getting closer? [closed]

A NASA Mars article says: Mars' orbit is more elliptical than Earth's, so the difference between perihelion and aphelion is greater. Over the past centuries, Mars' orbit has been getting more and ...
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### Does Soter take into account Pluto's and Orcus' masses when determining Neptune's planetary discriminant µ?

Does Steven Soter's planetary discriminant µ1 for Neptune take into account the masses of Pluto, Orcus and other Kuiper belt objects crossing or coming very close to Neptune's orbit? If so, Neptune ...
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