Questions tagged [orbital-elements]

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

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43 views

How to calculate the orbital velocity, the high-orbit (quasigeostationary) holding force and the shadow of the disk on Earth? [closed]

[] The following data are given: • The circular orbit of the disk D (quasigeostationary orbit) parallel to the geostationary orbit. • Located 4,505 km to the north of the equatorial plane, above ...
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1answer
76 views

Orbital speed is (vector) sum of tangential and normal speed?

Orbital speed definition in wiki does not state clearly - it is just tangential speed component or square root of squares of normal and tangential speed (full speed vector). When we say that moon ...
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73 views

Could someone please explain to me how I can extract velocity component values from Stellarium, for a given planet?

For a project that I am currently working on, I would like to know how one could extract velocity component values ($v_x$, $v_y$ and $v_z$) for a planet from the Stellarium software. The current ...
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2answers
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Night-Day Cycles in S-Type Planetary Systems

I am a writer and space enthusiast. For a story I am currently writing I would like to have a planet which orbits a star which resembles the sun, which in turn orbits another star. In this situation ...
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1answer
58 views

Perihelion dates and parameters

I have to find the perihelion and aphelion data for the 20th century for Earth. I found this table http://www.astropixels.com/ephemeris/perap2001.html, but no such table for the past century. I ...
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1answer
86 views

How Long Will Earth's Year be When Our Sun Goes Red?

We live in a planet that orbits 93 million miles from a G-type main-sequence star, or "yellow dwarf". That is far enough for a revolution of 365 days. Such is the case of Kepler's Third Law of ...
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1answer
52 views

In System KIC 9246715, How Far Does One Star Orbit the Other?

I was going to ask if it's physically possible for one red giant to orbit another, but fortunately, I have just found such a thing--a red giant binary system known only as KIC 9246715. In this ...
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75 views

Clearing the Neighbourhood: Definition of 'Orbital Region'?

I am trying to determine how wide a 'neighbourhood' a planet is expected to clear. However, the Wikipedia article on the matter provides no clarity, simply stating that a planet is expected to clear ...
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63 views

periodic inclination change circumbinary planet

I am studying circumbinary planets and I made a python model to calculate certain properties of the orbits, and when I calculate the inclination I get a sine wave. I do not see a way to predict the ...
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Are occultation observations used/useful for orbit determination?

The IAU Minor Planet Center lists $(486958)\space 2014 \space MU_{69}$ "Ultima Thule" as having an uncertainty parameter of 2, based on the observation arc of 851 days, from its discovery in 2014, to ...
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43 views

Relationship between Periapsis and apoapsis longitude

What is the relationship between Periapsis and Apoapsis longitude ? Are they 180° apart ? (ie) Periapsis + 180° = Apoapsis ? Related question: if apoapsis is not known, what orbital elements are ...
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How was this interstellar fireball observed and its trajectory analyzed?

The short, interesting paper Discovery of a Meteor of Interstellar Origin describes a proposed discovery of a second interstellar object. This one hit the Earth, and was discovered not by telescope, ...
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How to draw an orbit from Orbital Elements using Transform3DGroup

I am trying to draw an orbit using the Transform3DGroup class in the C# .NET framework. I have orbital elements a, e, i, RAAN, ArgPer, trueAnom. The algorithm that spits these out for me also gives me ...
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1answer
36 views

Where can I find data on Mercury's orbit to fit a model to? [duplicate]

I have a project in which a Monte-Carlo method is used to find the optimal parameters for some model that is fit to a data set. I want to fit a model for the orbit of Mercury using this methods, but I ...
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2answers
101 views

How to calculate the argument of perihelion for exoplanets with incomplete orbital elements?

I'm trying to simulate the Kepler-444 exoplanetary system using data from this website. The problem is that there is no argument of periapsis parameter for the Kepler-444 system, so while I think I'm ...
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55 views

How to convert a function of keplerian elements to a function of equinoctial elements?

I need to convert the Keplerian orbital elements to the equinoctial elements and then use the converted elements"equinoctial" in the function "d" below. To do this, first, I converted the Keplerian ...
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3answers
105 views

Why is it impossible to estimate the inclination of an exoplanet with the Radial Velocity Method?

The formula of the radial velocity is: $$v_i= V - K(\sin(f_i+\omega)\ + e\sin\omega),$$ with $$K = \frac{m_p}{m_s+m_p}\frac{na\sin i}{\sqrt{1-e^2}}.$$ Being $V$the systematic velocity of the system, ...
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1answer
287 views

Calculate the orbital phase when plotting the Radial Velocity data of a transitting exoplanet

I'm not quite sure how I find the orbital phase ($\phi$) of a transitting exoplanet. For example, I have this RV data in this article: First of all, I don't know how that phase or "cycles" is ...
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1answer
85 views

What is the range of the zenith angle between velocity and position vectors?

I'm coding on a space simulator and I want to draw a predictable orbit for a satellite. I have read about orbits on http://www.braeunig.us/space/ and under the section "Launch of a Space Vehicle" they ...
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1answer
292 views

Why is Neptune true anomaly decreasing?

So I've been having fun with trying to determine where the perihelia of different planets are (using JPL Horizons). And by the time I got to Saturn, something weird started happening. I've noticed ...
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2answers
179 views

Explanation of Longitude of Periapsis [duplicate]

I'm looking for a mathematical justification of the longitude of periapsis as it makes no mathematical sense to me as a notion. By definition, it is the sum of the argument of periapsis and the ...
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1answer
53 views

Moonkeps PC program

Does anyone know where I could obtain a program called Moonkeps? It was an old MsDos based program that produced, I believe, the Keplerian elements for tracking the Moon and also the Sun. I wish to ...
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1answer
67 views

Problems with computing X,Y,Z positions of planets at a certain time in Unity3D (C#)

I'm trying to create a little program in Unity3D that positions the planets in 3D space at a given time. I've followed this document: http://stjarnhimlen.se/comp/ppcomp.html. Using the data from ...
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314 views

Semi-major axis, vs aphelion, vs mean orbital distance?

The website Swinburne University of Technology (AU) gives the definition of semi-major axis as: ...half of the longest diameter of an ellipse. This website give the definition of semi-major axis ...
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404 views

Tables of aphelion/perihelion dates for other planets?

It's relatively easy to find tables for Earth aphelion and perihelion dates and times, such as this one: http://www.astropixels.com/ephemeris/perap2001.html But what about the other planets in the ...
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1answer
175 views

Saturn's tropical year?

What is the value of Saturn's "tropical year" (as opposed to its "sidereal year"). I am seeing it listed as 10 days shorter (10,747 days) than the sidereal year (10,759.22 days). How could this be ...
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1answer
148 views

Given sunrise, noon, sunset, longitude and latitude can I calculate the “hight” or “ascension” of the sun?

I'm trying to make a simple app for my own use to be able to check which of my favorit restaurants have outdoor seating sun and for how long etc. Given the data in the title (sunrise, noon, sunset, ...
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1answer
127 views

Calculating obital velocity from radial velocity

I'm not really a physicist so I don't know if it's possible to get the real orbital velocity of a star from its radial velocity. I'm working on a paper for school and I want to get the mean velocity ...
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1answer
44 views

Calculate eccentricity from apside altitudes? [closed]

I need to calculate the eccentricity of a satellite orbit with only the apside altitudes (height above the surface of the Earth), 400 and 1500 km. However, I don't know the semi-major axis ($a$) or ...
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1answer
341 views

Longitude of Perihelion at J2000?

My textbook (and lots of other sources) shows the earth's longitude of perihelion at the epoch around 103 degrees. I understand that this means (in the neighborhood of J2000) the earth will reach ...
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1answer
408 views

How would one calculate the synodic period between 3 planets?

I don't know if this is the correct term, but how would one calculate the time it takes for 3 planets to lie on the same line?
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How do I calculate the hour angle of a planet's moon from a point on that planet's surface?

I'm worldbuilding and I'm trying to construct a standing stone calendar that'll accurately denote where to look for my planet's moon at its four major phases from 53.8 degrees South. So, I need the h0,...
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80 views

Does habitable zone take tidally locked bodies into account?

Imagine a tidally locked planet orbiting a red dwarf, where habitability is not situated close to terminator zone, but on a "small" cap normal to incident starlight (zenith) with permanent average +15 ...
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4answers
3k views

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

Kepler's 3rd Law (regarding the relation between orbital period and the semi-major axis of an orbit) applies to all elliptical orbits. But as I understand it, the only reason it is safe to use the ...
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1answer
761 views

How to calculate true equinox position?

I'm trying to calculate the state of the Earth at a given time using Keplerian orbital elements from this page. It has the following instruction: Compute the coordinates, $\mathbf r_{ecl}$, in ...
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40 views

If the moon's orbit decays- how would it effect the moon's phases? [closed]

If a planet passed near the moon and caused its orbit to decay down to earth- how long could it take and how would that effect the visible phases of the moon on earth?
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1answer
229 views

Can a binary star optically “orbit” a planet?

I was watching a science fiction anime from the mid 70's. In it, there was a star orbiting a planet. Since this seemed impossible, and I had never heard of it, I looked on the internet to see if this ...
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1answer
277 views

How Can I Interpolate Ephemerides?

I have two ephemerides for orbital elements—that is, each contains $a$ (semi-major axis), $e$ (ecc.), $i$ (incl.), $\Omega$ (long. asc. node), $\omega$ (arg. of peri.), $\tau$ (time of peri.), $T$ (...
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Ecliptic plane, its precise definition useful for calculations

My question is similar to the one posted by Abtract, whom however never got a useful answer. I am trying to calculate from scratch the exact times of sunrise and sunset anywhere on earth taking into ...
4
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1answer
300 views

Orbits using Newtons laws

I am making a small orbit simulator. I figured out Kepler's laws and know how to work with them to "update" an orbit based on time. So now I want to know how I can describe orbits with newton laws. ...
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1answer
138 views

Is there a preference for orbital planes of planetary systems to be aligned with the galactic disk?

I'm not sure for how many planetary systems we have a fairly good idea of the inclination and "argument of periapsis" of the orbital plane. I'm assuming there are a number of them that we can estimate ...
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1answer
2k views

How Wide is Earth's Roche Limit?

My question is simple: Given the gravitational relationship between Earth and the moon, how wide is Earth's roche limit? How close does the moon have to orbit before getting disintegrated by Earth's ...
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1answer
190 views

VSOP87D: What are the purpose of the initial columns in the VSOP87D data?

I am trying to write an app to determine planetary positions, using Jean Meeus' Astronomical Algorithms as a reference. His guidance on using the VSOP87D data is straightforward, as are many other ...
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2answers
395 views

Sun's orbital elements

I have the orbital elements of an asteroid's heliocentric motion (the orbit has non-zero inclination and is elliptical). But I want to simulate the motion of the sun around the asteroid. So without ...
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1answer
225 views

How to calculate planetary position over vast time spans

Ignoring the turbulent beginnings of our solar system I wonder if there is a meaningful way to calculate the relative position of the planets of our solar system 100 million years into the future ...
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1answer
604 views

Orbital elements of solar system using Pyephem

I'm using the astrometric python module Pyephem, and I would like to get the orbital (keplerian) elements for the solar system planets. The only values I found is the heliocentric latitude, ...
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1answer
356 views

Orbital velocity of a planet - why is my calculation off by about 10%?

I am not sure if I am doing something wrong, or misunderstanding Reider and Kenworthy (2016). I'm just trying to reproduce the orbital velocities listed in Table 1. The second paragraph of Section II ...
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1answer
151 views

Calculate eccentricity with altitude and semiminor axes

Following on from this question, I wish to know how to find the reverse - how to find eccentricity given a Semi-minor axis & altitude. I want to use something based on $$b=a\sqrt{1−e^2}$$ but ...
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1answer
209 views

How to correctly create planetary orbits from kepler elements

I would like to build a gravity model (with 3D graphics) that would build the orbit of the planets based on orbital elements input and the gravity calculation for each element. My initial code is ...
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1answer
86 views

orbital angular momentum and the longitude of ascending node

Consider the motion of a planet around an oblate star. Because of the oblateness the star has a non-zero quadrupole moment which causes the orbital angular momentum of the planet to precess around the ...