Questions tagged [orbital-elements]

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

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1 answer
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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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2 votes
0 answers
71 views

The causes of the nodal precession of a satellite in Earth orbit? [migrated]

All artificial satellites in Earth orbit between the polar orbit and the equatorial orbit are subject to a nodal precession caused by the equatorial bulge of the Earth at the equator. How the ...
7 votes
2 answers
2k views

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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5 votes
1 answer
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Question about Cowell's method

According to Wikipedia: “ ... for $n$ mutually interacting bodies, Newtonian forces on body $i$ from the other bodies $j$ are” given by the summation equation$$\ddot{\mathbf{r}}_{i}=\sum_{j=1,j\neq i}^...
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5 votes
1 answer
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Orbital modelling, three bodies, leapfrog numerical integration

Apologies for the length of this question. I'm modelling the motion of a single planet around the Sun using the equations: $$dv_{x_{i}}/dt=a(t)=-GM_{SUN}x_{i}/r^{3},$$ where $x_{1}=x$, $x_{2}=y$ and $...
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2 votes
1 answer
90 views

Orbital modelling - best choice for initial JPL Horizons data?

I'm modelling planetary orbits using a spreadsheet and Feynman's numerical method given here. I have put together a spreadsheet (10,000 rows) to model Mars' orbit in three $\left(x,y,z\right)$ ...
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2 votes
1 answer
106 views

Time taken calculation to reach synodic degrees between planets

I have a software tool which calculate the synodic period with degree inputs with two planets. Synodic Period is the temporal interval that it takes for an object to reappear at the same point in ...
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1 answer
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Calculate how many days left for synodic period from particular planet

One of the many tools used in Astronomy are the formulas used to determine Orbital Motion. There are two basic forms of orbits: Sidereal Period Synodic Period For Jupiter: $$\mathrm{\frac{1}{P} = \...
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1 vote
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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 ...
3 votes
0 answers
53 views

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 ...
7 votes
1 answer
253 views

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
2 answers
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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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10 votes
1 answer
2k views

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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1 vote
1 answer
107 views

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 ...
28 votes
2 answers
6k views

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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8 votes
1 answer
206 views

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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2 votes
1 answer
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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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8 votes
4 answers
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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'...
0 votes
1 answer
88 views

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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8 votes
1 answer
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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 ...
5 votes
1 answer
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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, ...
5 votes
1 answer
75 views

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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3 votes
1 answer
118 views

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. ...
2 votes
0 answers
106 views

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 ...
2 votes
0 answers
43 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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3 votes
2 answers
108 views

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 ...
2 votes
1 answer
72 views

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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3 votes
1 answer
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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 ...
2 votes
2 answers
133 views

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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8 votes
2 answers
170 views

If the hypothesized planet behind the Kuiper belt existed, would it have a barycenter outside the Sun?

In 2016, an additional object rotating our Sun has been suggested. Assuming it has 5 Earth masses, would the planet or black hole proposed by Brown and Batigyn have a barycenter within the Sun or ...
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2 votes
0 answers
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When an object revolves around an oblate planet, in near-circular orbit, does the oblateness ALWAYS make it moves FASTER?

tl;dr: The orbital period for a Keplerian orbit of a small body around a massive one with standard gravitational parameter $\mu=GM$ and semi-major axis $a$ is given by $$T = 2\pi\sqrt{\frac{a^3}{\mu}}....
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How likely are triple planet systems?

Is it likely to ever discover three planets of similar mass revolving around a common barycenter, or would such a system be too unstable? Such triple planet system would look like a triangle once in a ...
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3 votes
2 answers
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Nodal Precession of Planets

It is obvious that the longitude of ascending node ($ \Omega $) of a planet gradually changes with time. For example, the VSOP planetary theory accounts for this. In Astronomical Algorithms (Meeus ...
11 votes
2 answers
2k views

What is the difference between the two terms named "Eccentricity" and "Ellipticity"?

I don't get the difference between the two terms named "Eccentricity" and "Ellipticity", especially, in astronomy. I understand eccentricity as a measure of the curvature of a ...
1 vote
1 answer
238 views

Keplerian Elements

So, I've been doing endless research, and I've found a bit of information, all in different places, that is. Now, I'm getting really confused about it; I can't keep up with it all anymore, so, now, it'...
9 votes
3 answers
405 views

Asteroids conjunction

I am currently writing a C++ program to show asteroids in 3D, and find close approaches or collisions. I got my orbital elements from JPL https://ssd.jpl.nasa.gov/sbdb_query.cgi. So far so good, with ...
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3 votes
2 answers
177 views

How to calculate center (not focus) of planetary orbit?

I'm developing a website showing the movement of Solar System planets according to the passage of time. I'm using this reference to calculate all the necessary orbital parameters. These are two images ...
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Visual binary star with circular apparent orbit

Does anyone know a good example of visual (or interferometric) binary star apparent orbit of which looks circular due to projection though in fact is markedly elliptical? I need that for teaching.
5 votes
3 answers
255 views

Kepler's Law, focal points - Heliocentric or Barycentric?

It is known that all the mass in the Solar system moves around the Barycenter. For the two focal points in Kepler's law; is the first focal point $F_1$ a Heliocenter? Or is it actually a Barycenter? ...
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2 votes
1 answer
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Is Jupiter really shepherding the main belt, and Neptune the Kuiper belt?

By "dominating another object's orbit" my understanding is that the most massive body's gravity has so much influence that, when they come close, it makes the other body/bodies' orbits shift ...
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2 votes
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Based on discoveries of new TNOs since 2016, is planet Nine still necessary to explain the TNO's orbits?

It is almost five years since the announcement of the likelyhood of another planet that is responsible for clustering eTNO's orbits, very close perihelia of detached dwarf planets to the Sun, and high ...
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3 votes
1 answer
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Problem with Tychonian model of geocentric universe?

Just like other proposed models of universe in history, Since Tycho's aren't being used, there MUST be any flaws in compare with widely agreed today understanding Is there any detailed reference ...
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6 votes
3 answers
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"Periapsis" or "Periastron"?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
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1 vote
1 answer
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Are there any known low-inclination trans-Neptunian objects?

All the trans-Neptunian object's orbits I know are very inclined compared to those of the eight recognized planets, and Centaur's orbits are highly inclined as well. Are there any known Centaurs and/...
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16 votes
3 answers
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What are "non-Keplerian" orbits? What are some familiar examples in our solar system, and can some still be closed?

This excellent answer to Forms of stellar orbits around the galactic center invokes the following concepts: non-Keplerian orbits closed orbits I have a fairly good idea what these mean and so might ...
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6 votes
1 answer
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Forms of stellar orbits around the galactic center

Do all stars in orbit around Sagittarius A have approximately circular orbits or are there stars that orbit the Milky Way center very elliptically, like being in the Milky Way's outer rim at apoapsis ...
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0 votes
0 answers
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The possibility of rapidly changing the Earths orbit via a passing astronomical object

I assume that the Earth could be “gently” (without colossal tidal or volcanic catastrophe) displaced by a passing extra solar star, brown dwarf or planet and end up perhaps 10% further away from the ...
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3 votes
1 answer
622 views

Easy interactive visualization of orbital elements

To get a grip on orbital elements, I'd like to play with a ready interactive visualization like in Universe Sandbox. E.g. drag the inclination slider and see immediately what happens to the satellite ...
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Orbital Mechanics: where can I find initial conditions for orientations and angular rates of planets in our solar system?

I am looking to write the equations of motion (EOMs) for a 6DOF analysis of our solar system. I want to integrate the equations forward in time, and need a complete set of initial conditions to do so....
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1 vote
1 answer
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How do different formulas for calculating the mean anomaly of an elliptic orbit correlate?

I need to calculate the mean anomaly of an elliptic orbit at a specific point in time. I found two different formulas for $M(t)$ and I'd like to know how they correlate and if they result in different ...
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