Questions tagged [celestial-mechanics]
Questions regarding the motions of celestial objects.
94
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Where can i get epoch j2010.0 values for stars? [closed]
I just want to know that where can i find the epoch j2010.0 values for stars, their ra and dec values. is there any resource? any pdf or software library that gives these values?
Thanks ^^
3
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1answer
51 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?
0
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1answer
91 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
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2answers
96 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
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2answers
106 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
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1answer
119 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
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3answers
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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 ...
-3
votes
2answers
123 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 ...
5
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4answers
211 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 ...
3
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2answers
76 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
93 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
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0answers
61 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
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1answer
60 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
69 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
66 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
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1answer
62 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
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2answers
740 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 (&...
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0answers
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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 ...
5
votes
2answers
135 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 ...
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0answers
49 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
168 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
71 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 ...
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0answers
81 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
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1answer
42 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 ...
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0answers
41 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 ...
1
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1answer
54 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
120 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
52 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
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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
192 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&...
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1answer
63 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 ...
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0answers
55 views
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
...
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://...
0
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0answers
28 views
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 ...
9
votes
1answer
151 views
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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0answers
46 views
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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3answers
145 views
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:
(source)
2
votes
3answers
156 views
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 ...
4
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0answers
36 views
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 ...
4
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0answers
45 views
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:...
2
votes
1answer
129 views
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 ...
3
votes
3answers
363 views
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 ...
0
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0answers
66 views
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 ...
3
votes
1answer
418 views
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 ...
2
votes
1answer
480 views
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 ...
3
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0answers
94 views
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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1answer
55 views
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 ...
2
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1answer
244 views
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. ...
2
votes
1answer
95 views
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 ...
