Questions tagged [celestial-mechanics]

Questions regarding the motions of celestial objects.

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What celestial mechanics parameters define a lunar occultation of Venus visible from Earth?

As a carry on from the following thread Are lunar occultations visible to the naked eye? Is it correct that the following parameters must hold true if we use Moon occult Venus as an example [LongMoon ...
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How to calculate eclipses the heliocentric way?

It is my understanding that modern methods for calculating the time and location of solar and lunar eclipses (e.g. NASA website https://eclipse.gsfc.nasa.gov/eclipse.html) are integrating equations of ...
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Is Venus in some way tidally locked to… Earth?

The video here demonstrates how Earth sees the same face of Venus every inferior conjunction (i.e., two planets are the closest to each other): https://www.youtube.com/watch?v=4m_ouMC61-w (or https://...
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Rotating observer plane inside celestial sphere with a given coordinates, time and date [duplicate]

I have plotted stars around the surface of a celestial sphere. At the centre of this sphere, I have a brown plane which is the land. This plane can be rotated in the x,y and z axis. When x,y,z ...
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If Saturn's rings cannot coalesce into a moon because of tidal forces, then how are shepherd moons able to exist?

From Wikipedia: In celestial mechanics, the Roche limit, also called Roche radius, is the distance within which a celestial body, held together only by its own force of gravity, will disintegrate due ...
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When and why was zero right ascension defined to be at the vernal equinox?

When (and why) was zero right ascension defined to be at the vernal equinox? Who established or defined this standard?
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Why does east and west appear to be mirrored in the celestial sphere?

I'm wondering why East is left and West on the right of the celestial sphere if you look at images of it? Example below: http://jrjohnson.net/wp-content/uploads/2015/01/Annotated_Sky_Map.png
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Why does the latitude of an observer affect the hour angle of a body in Stellarium?

I am using Stellarium for astronomical data to help in studying celestial navigation. While trying to track down a source of errors in my sextant reading or sight reductions I noticed that the local ...
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Explanation about the resonance, mean motion resonance and libration

I am studying for a project the dynamics of multi-planetary system in resonance. I have two questions about this domain. In many articles they speak about 'mean motion resonance', what is the ...
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Strange asymptotic behavior on the Kozai-Lidov cycles

So, in Naoz et al. (2013) is described the Kozai mechanism on three-body systems. I've tried to solve the equations (B1) - (B17) for the example described in the Figure 3 and I got something like this:...
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How to calculate local position, knowing the RA and Dec of the center of an image, RPY of the camera, and precise time?

Given a picture of stars - assume it is possible to identify the stars and their Right Ascension (RA) and Declination (Dec). By choosing one near the center of the image (or interpolating RA/Dec to ...
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Why does the Sun track out a seemingly sinusoidal path on the celestial sphere?

The question arose because I wanted to understand the path of the ecliptic after reading about it here: https://community.dur.ac.uk/john.lucey/users/solar_year.html Is the sinusoidal path due to ...
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Ecliptic line data [duplicate]

I would like to get the data of ecliptic line with respect to celestial equator for a particular day. Is there any specific URL that can give me this. I only have data for declination of Sun and the ...
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Hohmann transfer orbit (Earth-Jupiter system)

Consider the Hohmann transfer orbit of a probe launched from Earth to Jupiter. Assume the orbits of Earth and Jupiter are circular. I want to calculate the following: The semi-major axis and ...
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Planetary Declination and Axial Tilt

Is it a coincidence that Earth's axial tilt and maximum declination are both approximately 23 degrees? Mechanically speaking, do planets physically cross the Solar equator, or is declination due to ...
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Eccentricity from Analemma

Can the eccentricity of a planet's orbit be found just from the analemma of its star? We can draw an analemma given the axial tilt and eccentricity, but how do we find the reverse? Note: I already ...
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Undisturbed planetary alignment after galactic collision

How do planets still orbit around the empty space where a black hole was after a black hole absorbs the milky way's black hole and keeps moving through space without disturbing surrounding planets ...
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Determine Julian Date from Gregorian without formula

As an exercise, I am trying to calculate the JD from a given date in the Gregorian Calendar at a time given in UT. Furthermore, I want to do so from first principles without relying on any formula. ...
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How was Cruithne's orbital time calculated?

How was it determined that Cruithne takes 770 years to complete its cycle with Earth? Janus and Epimetheus were disovered long enough ago, and have short enough cycle times, that we've had time to ...
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What variables are needed to calculate simple horseshoe orbit times?

EDIT This was NOT a duplicate of Horseshoe orbit cycle times. But that other question has been deleted, regardless. My original question asked for the answer to the equation(s), and provides many of ...
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If Earth suddenly stops rotating, will be thrown at 465 m/s? [duplicate]

If Earth suddenly stops rotating, will be thrown at 465 m/s ?
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Why is Uranus able to support a regular satellite system?

Uranus has an obliquity of 98° which means that the mutual inclination between a satellite orbiting in its equatorial plane and the orbit of Uranus around the Sun would exceed the critical angle for ...
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How does the gravitation of Jupiter or other big planets affect Kepler's third law?

Does anyone know any good reference on this? I remember reading once about how Jupiter's gravitation can be treated as a perturbation, but I cannot find it again now. I think they expanded Jupiter's ...
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What does “all stop” mean in reality?

In science fiction, when a starship captain commands "all stop," the audience simply assumes that, like a terrestrial naval ship anchored to the ocean floor, the ship literally comes to a complete ...
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How does the Sun orbit the Sun-Jupiter Barycenter?

I got the Orbital Elements of Jupiter around the Sun, which describe how it orbits relative to the "fix" Sun. Jupiter Semi Major Axis (AU): 5.20336301 Eccentricity: 0.04839266 Inclination to ...
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Why does the precession of the earth affect other planets?

In the Wikipedia article on numerical integration of planetary motion it states: ...the flattening of the Earth causes precession, which causes the axial tilt to change, which affects the long-...
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Is the Milankovitch calendar provably better than the Gregorian one considering a non-constant tropical year?

It's somewhat of a no-brainer the revised Julian calendar (attibuted to Milankovitch) is more accurate than the Gregorian one just because it started with a more accurate estimate of the duration of ...
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Why planets and stars are always round/oval in size? [duplicate]

What kind of stability it provides to each and every celestial body that each one them are round in shape?
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Implementation of formulae for Meeus for the Moon

With Astronomical Algorithms by J. Meeus (1998) I have obtained the relevant illuminated fraction of the disk and position angle. But they're numbers (all Greek to me!) I know, Meeus explains that ...
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How to compute the perihelion precession of Earth's orbit?

I want to simulate the perihelion precession of Earth. I tried searching other posts in stack exchange as well relating this question but may be it's my fault that I couldn't understand their answers....
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Can Two Stars of One Same Type Orbit Each Other?

This is a simple, textbook definition of a binary star orbit. One low-mass star orbits a higher-mass star in a narrow but definitive center. For example, the high-mass star would be our own sun--a G-...
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How can Earth-Sun Lagrange points L1 & L2 even be semi stable considering the moon?

I know that the Earth-Sun Lagrange L1, L2, and L3 points are not considered stable over longer periods, especially when compared to L4 and L5... But, with the moon orbiting the Earth in the general ...
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Calculate NEO object position with nasa Near Earth Object data

I wish to create a 3D visualisation of NEO's by date in relation to earth, but calculating their position at that time has got me stuck. From this question I was able to fine Nasa's NEO object data: ...
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Equations of motion for Earth and Moon

One of the simplest versions of Newton's equations of motion for the Sun, Earth and Moon can be obtained by making the approximation that the three bodies are perfect spheres. In this approximation, ...
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Is it true that open clusters have $E > 0$ and globular clusters have $E < 0$?

I just need to confirm or refute something I'm believing since a very long time, maybe without real evidence. Can we distinguish stellar clusters by their total mechanical energy ? Is it true that ...
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Celestial navigation from scratch

Is it possible to establish one's longitude and latitude by observing the stars? Can you use observations of the stars to find the relative distance between two locations, which would be useful in map-...
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Angles in Moon, Earth and Sun system

Consider the vector positions of the center of mass of Moon, Sun and Earth, $\vec{r}_{\rm M}$, $\vec{r}_{\rm S}$, $\vec{r}_{\rm E}$, respectively, in a given reference frame. Consider: the angle ...
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Requirements for a satellite/planet to be tidally locked to a planet/star

The Moon is tidally locked to the Earth, the Four Galilean are tidally locked as well, and the recently found planetary sistem TRAPPIST-1 has seven tidally locked planets, but Venus or Mercury are not....
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Sky in the very far future / past

Motivated by this question about a stranded submarine in the Jurassic I would like to know: Is there anything remotely left of our current skyline if we go back or forward millions of years so that ...
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Is Pluto a “proto-planet”?

My question is this : could the Charon-Pluto system becomes in the coming few millions years a full fledged planet, as in the IAU classification ? I ask this because there are two facts that bother ...
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How can the next supermoon be analytically predicted?

The lunar motion can be predicted with basic celestial mechanics, but the perigee and apogee are not always the same, basically because the attraction of the Sun makes some oscilations in the semi-...
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Is there any way for a planet orbiting a red dwarf in the habitable zone to not be tidally locked?

Is there any way to avoid the tidal locking of a planet orbiting a red dwarf in the habitable zone? For example, could a planet with a 90° obliquity and large moon avoid such a situation?
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The deduction of the Hill Sphere formula

This question may be a little lazy, but can anybody give me a proof of the Hill sphere formula? Acording to wikipedia, the formula for the radius, $r$, is $$r\approx a(1-e)\left(\frac{m}{3M}\right)^{...
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On orbital mechanics of evaporating planets

A planet orbits around its sun on an elliptic orbit, and loses mass slowly due to evaporation. How will the parameters of the orbital ellipse change as a function of time? Could we do a generalisation ...
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Creating a basic “fixed” solar system to host a 3D space travel simulation

I'm trying to simulate a virtual/imaginary "solar system" in software--just a hobby project for now. Unfortunately this has made me realize exactly how much math I've forgotten since college. ...
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The path of the planets on the celestial sphere

I know that planets have a "wandering" movement on the celestial sphere. I also know that their period around the Sun vary largely as compared with the period of the Earth (one sidereal year), ...
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Question about the Figure-eight periodic planar three-body motion

If this is a posible periodic solution for a three-body problem, can anybody tell me where is the center of mass of the system? As we know, in a n-body problem the bodies orbit around their center of ...
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Need Simple equation for Rise, Transit, and Set time

I've been looking, unsuccessfully, for hours for a simple set of equations: Input: RA and Dec of an object Observers Lat and Lng Current Time Output: Rise Time Transit Time Set Time (and, ...
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Is Io's orbit or rotation affected by its volcanism?

The rotations of comets and asteroids are affected by outgassing volatilities. Io is very volcanically active. Does this give Io a varying orbit and a slow rotation? Tidal forces should take longer ...
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Two body orbit of equal masses

Given two bodies of equal mass in an elliptical orbit: I know they will be orbiting about a common center of mass, i.e. the barycenter. But, do the velocities have to be equal in magnitude and ...