Questions tagged [celestial-mechanics]
Questions regarding the motions of celestial objects.
111
questions
6
votes
1answer
531 views
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 ...
10
votes
3answers
1k views
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 ...
1
vote
1answer
45 views
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 ...
1
vote
0answers
76 views
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 ?
2
votes
1answer
32 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 ...
3
votes
1answer
79 views
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 ...
3
votes
1answer
122 views
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 ...
1
vote
0answers
46 views
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 ...
7
votes
1answer
289 views
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 ...
3
votes
2answers
106 views
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 ...
1
vote
0answers
71 views
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 ...
2
votes
1answer
56 views
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 ...
3
votes
1answer
62 views
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 ...
1
vote
1answer
44 views
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 ...
0
votes
0answers
35 views
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?
0
votes
1answer
162 views
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 ...
9
votes
2answers
1k views
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 ...
5
votes
1answer
507 views
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,...
3
votes
1answer
53 views
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?
1
vote
1answer
163 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'...
2
votes
2answers
273 views
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 ...
2
votes
2answers
250 views
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 ...
1
vote
1answer
255 views
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 ...
21
votes
3answers
5k views
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 ...
-2
votes
2answers
204 views
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 ...
6
votes
4answers
238 views
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 ...
4
votes
2answers
113 views
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 ...
3
votes
2answers
99 views
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 ...
1
vote
0answers
63 views
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, ...
1
vote
1answer
64 views
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 ...
1
vote
1answer
106 views
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 ...
3
votes
1answer
83 views
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 ...
0
votes
1answer
64 views
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 ...
6
votes
2answers
753 views
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 (&...
1
vote
0answers
25 views
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 ...
5
votes
2answers
160 views
How to derive Kepler's 1st Law?
I was going through the derivation of Kepler's 1st Law in the textbook "An Introduction to Modern Astrophysics" by Carroll and Ostlie. From there, I got stuck in a few places in their ...
1
vote
0answers
50 views
Variation in g acceleration due to gravity
I want to find a routine which will enable me to calculate the variations in g
as a result of the motion of sun and moon. I need to have the date as a variable.
I realise that Dennis Milbert's earth ...
4
votes
2answers
178 views
Discrepancy between my results of Great Conjunction 2020 and Wikipedia
Using python-skyfield to calculate the upcoming conjunction of Jupiter and Saturn. I'm off a few minutes with the times on Wikipedia.
Wikipedia Great conjunction times (1800 to 2100)
Using Right ...
1
vote
1answer
73 views
Does the Honey moon have a precession problem?
In Steven Colbert's interview with Neil deGrasse Tyson after about 03:16 the following is explained:
But wait, all the moons - all the full moons of the year have ...
1
vote
0answers
82 views
Will the United States Presidential Election (day asteroid) be back soon?
My google news feed is awash with mono-themed articles, including a near Earth asteroid that passed by around election day 2020 in the US.
We can all hope that neither will lead to an extinction level ...
1
vote
1answer
49 views
Is there an antonym for 'transit', i.e. the transit of a celestial body through the meridian
I'm writing software to calculate the rising, transit, and setting of a body on the celestial sphere for a specific location and date. It seems to me that the opposite of transit, at least in the case ...
0
votes
0answers
44 views
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 ...
0
votes
1answer
58 views
Historical Lunar Tables and the Associated Error Bound
Consider as an example, AstroPixel's ``Six Millennium Catalog of Phases of the Moon''---
http://astropixels.com/ephemeris/phasescat/phasescat.html
My question is two-fold:
How are these tables which ...
2
votes
2answers
141 views
Why doesn't Earth's leading tidal bulge cause the Moon to start spinning in the opposite direction than its original spin?
Please refer to the image below:
My question is, why doesn't Earth's leading tidal bulge (encircled in the green circle 1) pull on the moon's tidal bulge (encircled in green circle 2), leading to a ...
3
votes
1answer
100 views
How to calculate the point on the globe with maximum magnitude with given Besselian elements and given time for a partial solar eclipse?
I am currently working on improvement of an Android app that calculates solar eclipses. For many days now I have not been able to solve a mathematical problem concerning solar eclipses, so I decided ...
4
votes
0answers
61 views
Charged black holes selective eaters
We have a charged black hole which is negatively charged. For this simple case the black hole is not rotating.
If a negatively charged particle approaches the singularity the electromagnetic repulsion ...
27
votes
2answers
9k views
Where do we have it from that the Moon is migrating away from Earth?
I know Neil Armstrong placed a mirror on the Moon and people shoot lasers there which get reflected, by this, measuring the time the light is needing, they can conclude the current distance of the ...
2
votes
2answers
253 views
How can the Earth and the Moon be in synchronous rotation if the Moon won't be in geostationary orbit?
It is said that the Moon moves away from Earth and that during the Sun's red giant or white dwarf phase the Moon will be about 40% farther than now and in a synchronous rotation ("hantle rotation&...
1
vote
1answer
66 views
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 ...
34
votes
3answers
7k views
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://...
