Questions tagged [celestial-mechanics]
Questions regarding the motions of celestial objects.
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How is Earth's Rotation Angle (ERA) defined and measured
UTC typically ticks with TAI. But to keep UTC from drifting far from the rotation angle of the Earth we occasionally add leap seconds to ensure that UTC does not drift too far from the UT1 timescale. ...
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How to find zero velocity contours for circular restricted 3-body problem in x-y plane?
(I am having physics background; I am not an astronomer/astrophysicist.)
How to solve a single nonlinear algebraic equation in two variables, $x$ and $y$?
(I know that - if there are two variables, ...
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Do the inner-Earth planets actually align with the constellations we see?
For example, because the Sun is the center of the solar system; when we think that the Sun is on the constellation of Aries, in actuality, isn't Earth lining up with the constellation opposite Aries: ...
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Different techniques for calculation of celestial bodies dynamics with different time-scales
Differential equations describing the dynamics of celestial bodies (rotation, nutation, precession and other effects) can be solved numerically, which makes it possible to study their general non-...
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What stars are brighter then any star nearer to the south celestial pole [closed]
What stars are brighter (apparent magnitude) then any star nearer to the south celestial pole?
I know that there’s no bright star within a few degrees of the south celestial pole.
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You find yourself on a random planet in the milky way 2000 years in the future. Can you figure out where/when you are? [duplicate]
Imagine you're on a planet in a distant part of the milky way, 2000 years from now. You don't know where you are or how much time has passed. You have access to modern astronomical data and technology ...
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What is the horizon-ecliptic angle formula?
For an observer in a city with latitude 35°, at what sidereal time is the angle that the ecliptic makes with the horizon equal to the angle that the equator makes with the horizon? What is the angular ...
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Positional astronomy - Speed of the sun in sky
Let $\vec{r}$ be the position of the Sun in the sky, from Earth. How could I estimate the magnitude of $d\vec{r}/dt$, to measure the rate of change in time of the arc it traces? I suppose it would be ...
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calculating MPC orbital uncertainty parameter U
I'm trying to understand how the orbital uncertainty parameter 'U' introduced by the Minor Planet Center (MPC) is actually calculated for minor bodies. This wikipedia page gives the formulae to be ...
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Celestial Coordinates and Sun's degrees below horizon
I am struggling to understand the how the coordinates work.
Example: At vernal equinox RA=0 DEC=0, Does this mean the Sun is at its highest point at the equator?
If my mean solar time is 2h 30min, ...
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constant semi-major axes of the planets
in Numerical Expressions for Precession Formulae And Mean Elements for the Moon And the Planets (Simon et al., 1994), the orbital elements of the planets are given for long time durations.
The semi-...
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different corresponding coefficients in formulae for a mean element
why do they take λ₁ = 1 295 977 422.834 29ʺ from subsection 5.8.3.¹ (mean elements referred to the mean dynamical ecliptic and equinox J2000), and not λ₁ = 1 296 027 711.034 29ʺ from subsection 5.9.3.¹...
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How to calculate the local time of sunrise and azimuth of rising point of Sirius?
I know that right ascension equals to $6^h45^m$ and declination equals to $-16°43'$. I need to calculate local time of sunrise and azimuth of rising point of Sirius on 23 of September for an ...
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Orbital terminology for satellites relative to one another
Basic question, but I'm trying to describe a planetary system and coming up short on vocabulary. Do either of the following exist?:
A word for the closest pass between two satellites orbiting the
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How can Io be tidally heated while it is in tidal lock?
According to its Wikipedia page:
Rotation period: synchronous
Eccentricity: 0.0041
But also
...extreme geologic activity is the result of tidal heating...
How is it possible? It should not be ...
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How to calculate the altitude of a star given the hour angle, declination, and latitude?
I'm trying to find the altitude of a star for observing, but all I have is the hour angle and declination of the star, along with latitude of the location I'm observing from. How can I find the ...
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What's the meaning of virial in Astronomy, and in particular the expression "a virialized cluster of galaxies"?
The virial theorem relates the kinetic energy of a system to the total potential energy of the system:
$
\Delta K = -\frac{1}{2}\Delta V
$
so it has lots of uses in mechanics, thermodynamics and ...
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Schmidt corrector plate on a Newtonian = Schmidt Cassegrain?
Went on with a wide range of telescopes and its mechanics. To my understanding, the only change in the optical function in Schmidt Cassegrain telescope is a Schmidt's corrector plate in front of an ...
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Why is Earth at centre of Celestial Sphere?
Why do we consider Earth to be at the centre for Celestial Sphere ? If so, then how will Sun revolve around Earth ? Doesn't it mean its like the geocentric model ?
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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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Can you compute the solar day?
For a given planet, if you know the sidereal rotation period and the sidereal revolution period, can you compute the length of one solar day?
For instance, for Earth, if you know one rotation is ...
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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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Virial theorem for a binary system
I am trying to derive the virial theorem but for two stars orbiting each other. I know the derivation for the general virial theorem with i particles but I am wondering if there is a quicker or more ...
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Degrees of freedom in restricted circular coplanar three body problem
How many degrees of freedom does a mechanical system consisting of three bodies, the Sun, Jupiter and an asteroid, have in the restricted circular coplanar problem of the three bodies?
I know that if ...
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Can we learn anything from the chaotic movement of Hydra and Nix?
The NASA Visualization Explorer Moons In Chaos says Hydra and Nix, two of the moons of Pluto, show chaotic movement due to the shifting gravitational field.
How long a day lasts and where the sun ...
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Orbital resonance 2:1
I considered the motion of an asteroid around the sun, in a $2:1$ orbital resonance with Jupiter. Following the study of this resonance, it was observed that the angle between the major axis of the ...
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Orbital resonance - basic aspects
In the following lines, I will ask you some questions regarding the notion of orbital resonance. I know that the orbital resonance of two celestial body represents the driving of a dynamical system by ...
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Orbital resonances - expansion of disturbing function
I want to study the orbital resonance type 3:1 between an asteroid and Jupiter. For this purpose, I found the expansion of the disturbing function, $R$, in Celletti A., Stability and Chaos in ...
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Orbital parameters of the Sun [duplicate]
What are the orbital parameters of the Sun such as orbit velocity etc in it's orbit around the Solar System's center of mass? Consider the Sun pointlike or alternatively when talkin about the Sun's ...
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Accretion disk formation
Why a mass transfer in a binary star system, from the less dense star to the denser star forms an accretion disk? Why the material does not fall directly to the denserstar?
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Trajectory: What would happen if the sun disappeared one day?
So, let's just assume, to no aspect explainable to humans, the sun just magically popped out of existence on January 1st next year (2022), that'll never happen, this is just a scenario to explain my ...
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Spotting the booster rocket of the Chinese space station?
SpaceWeather.com's newsletter states
Sky watchers are reporting two new objects in the night sky: China's new space station and an out-of-control booster rocket that helped launch it. The tumbling ...
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Coordinates in the Night Sky
I've learned about Orbits recently, and there are 6 orbital elements. Now, I've heard of three coordinate systems whereas, they can help you measure positions of stars in the night sky. The Altazimuth,...
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What is the longitude of the winter solstice for the various planets?
I am looking for data showing the longitude at which the various planets in the solar system reach their winter solstice. Where could I find this data?
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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'...
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Accuracy of calculating the vernal equinox?
Calculating the exact time of the vernal equinox is essential for many ephemeris calculations. NASA Goddard Institute for Space Studies uses (at least for some purposes) the following, rather short ...
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Open source code for the maths behind a heliostat?
Theoretically, using a Raspberry Pi, (at least) one mirror, and two motors, one should be able to build a heliostat, i.e. a device which redirects sunlight to a fixed spot, like a scrub in the shadow ...
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Why temperature of dark side of moon is not 3 Kelvin
The temperature of the space between Earth and the Moon is around 3 Kelvin ($\approx -270^\circ {\rm C}$). The moon has no atmosphere, therefore the heat convection is not possible from the bright ...
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Why won't the Sun set for days at N66.2 which is below the arctic circle?
Correct me if I am wrong, but if we count sunsets by the center of the Sun apparently crossing the horizon then the Sun is supposed to set every day at latitudes under the arctic circle. (Yes if you ...
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What pulls the Sun above the galactic plane and pulls it below the galactic plane?
Since the sun climbs above the galactic plane and it even dives below the galactic plane we can't deny that it wouldn't climb upward unless there is something above the galactic plane that pulls it ...
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Apsides Calculation
I’m trying to calculate the precise moment of Earth’s apsides (perihelion and aphelion). The only formulas I find are in Astronomical Algorithms by Jean Meeus (1998). However, they give erroneous ...
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Why are solar systems stable and not chaotic?
I am not trained in applied mathematics and am asking as a layperson.
It seems that the motions of the planets can be reliably predicted for thousands of years. Yet, if we consider a relatively simple ...
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Do moons experience periods of no sunlight when orbiting "behind" their planet?
I'm writing a story that takes place on the Saturn moon Iapetusand I was thinking that especially since Iapetus only has an inclination of about 17 degrees from the ecliptic, wouldn't there be a point ...
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North Stars of each Solar system planet?
What are the North Stars of each individual body points too?
E.g.
Earth points to Polaris.
Mars points to Deneb/Alpha Cygni.
What about Sun, Mercury, Venus, Moon, Jupiter, Saturn, Uranus, Neptune, ...
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How to track orbit of an exoplanet?
I was wondering if there is an established method to keep track of the orbit of an exoplanet assuming we know a - the semi-major axis of the orbit, e - the eccentricity of the orbit, and i - the ...
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Launch windows for Venus transit; how to convert heliocentric longitudes to date?
Being a bit familiar with celestial mechanics, I know that the Hohmann transfer orbit is the quickest way to transfer between two circular orbits of different radii around a central body in the same ...
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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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Researching mechanics without “fixed stars”
In the history of humanity, easily observable extra-(Solar System) objects greatly helped understanding certain phenomena inside the Solar System. Importantly, the “precession of the equinox”, and ...
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Has any moon achieved "retrograde equatorial orbit"?
There are many moons which have low (almost negligible) inclination and can be considered to rotate at the planet's equatorial plane. For instance, Galilean moons have almost negligible inclination (&...
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Constants of three body problem(2 fixed centers)
I was solving two fixed centers problem and got answer in quadratures. After that i want to find constants of motion. First one is full energy - E. Second is $p_{\varphi}$. And third one comes from ...
