Questions tagged [orbital-mechanics]
The application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.
334
questions
3
votes
1
answer
347
views
Moon's equation of the centre discrepancy
According to the Wikipedia Lunar Theory article, the first term of the Moon's equation of the centre is
$$22,639^{\prime\prime}\sin l,$$where $l$ is the Moon's mean anomaly. According to the Wikipedia ...
- 1,023
7
votes
1
answer
808
views
What is the most stable orbit around the moon?
Let’s say I wanted to build a space habitat in orbit around the moon. Better still, let’s say I want to build a ring of habitats occupying the same orbital path, encircling Luna, to oversee the mining/...
- 397
4
votes
0
answers
182
views
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-...
- 141
8
votes
2
answers
359
views
What is the mean inclination for randomly oriented orbits? How to derive it?
I know the answer is $60^o$. But I can't seem to be able to derive the result.
Specifically, how to define the probability density function (PDF) for this problem? Once I have that it should be ...
- 181
5
votes
1
answer
364
views
What's the meaning of "hard supermassive black hole binary"?
In this paper, the authors state in the Introduction that
A hard SMBHB [SuperMassive Black Hole Binary] can eject surrounding stars to transfer their orbital energy and angular momentum, which may be ...
- 2,394
2
votes
0
answers
57
views
Is there an orbit around the earth that experiences a total solar eclipse by the Moon at least every month?
Is there a way to design an earth orbit so that it passes through the Moon's umbra with greater frequency than total solar eclipses occur on earth's surface?
What is the maximum frequency of eclipses ...
- 21
2
votes
0
answers
41
views
From a given latitude on Earth, how to calculate the number of days in a year when the moon is lit on the bottom?
From a given latitude on Earth, is it possible to calculate the number of days in a year when there is a wet moon , that is when the moon is lit on the bottom?
If, for example, I want to do the ...
- 627
5
votes
2
answers
84
views
What is meant by " elliptical galaxies stabilize due to the chaotic motion of stars"?
I read that elliptical galaxies stabilize due to the chaotic motion of stars. As I understand that means that the stellar motions are more nearly random in direction. So they perform independent ...
- 711
1
vote
0
answers
41
views
How to call the fear of no gravity? [closed]
In opposite to barophobia I can't google out a fear of the case, when a man is taken out of the ship and he must go through the spaceship's docks and he can't get the direction of gravity - in the ...
- 119
2
votes
1
answer
137
views
Radial velocity
Is there a way to calculate the radial velocity without wavelength? I can only find two formulas so far. One of them needs wavelengths and the other one needs the velocity of the star, but I have none ...
- 61
3
votes
0
answers
148
views
How do star orbits, density wave theory and dark matter distribution work together?
I got confused while trying to combine these 3 concepts. Would love to hear some detailed explanation.
Density wave theory states that spiral arms are formed by tilted elliptic orbits. Bertrand's ...
- 31
2
votes
1
answer
85
views
Radial velocity of host stars and exoplanets
I am new to astronomy/astrophysics.
(1) In the CATALOG OF NEARBY EXOPLANETS, I came across the following terms.
Please see Table 2 of the above paper. 12th column lists $v \sin(i)$ - It is the radial ...
- 169
2
votes
1
answer
120
views
Orbital Stability of a Double Planet System
I recently found an article claiming a double planet system needs to be at least .5 AU from its parent star to be stable for billions of years. It was specifically talking about two same-mass bodies, ...
- 61
15
votes
2
answers
3k
views
Does the Inverse Square Law mean that the apparent diameter of an object of same mass has the same gravitational effect?
Someone else asked about various planets located at the orbital range of the Moon. It made me wonder if an object with the same density as the Moon, at a distance which would present the same angular ...
- 786
2
votes
1
answer
36
views
How can I determine a planet's orbital size if it is moving around an oscillating star?
I'd like to know how to calculate the size of the planet's orbit, given that it is the only one orbiting around a star, and that this star is oscillating with an amplitud of 0.026'' in 25 year periods....
- 21
3
votes
1
answer
147
views
How do times of lunar standstills vary over time? If we folded them back into a lunar month plot, would they have "prograde and retrograde motion"?
The recent question Are lunar phases and lunar standstills in sync with each other? brought me to a standstill because I don't fully know what a lunar standstill is. It's one of those words like "...
- 31.1k
6
votes
0
answers
92
views
Kepler ellipse orbit fit issues
I am helping my high schooler with a research paper that uses PyAstronomy to fit the orbit of stars around Sag A. It isn't working because the angles (parameters Omega, omega, and i) seem to have a ...
- 61
4
votes
2
answers
871
views
Radio signals between Mercury and the Moon during an eclipse
This is a hypothetical question. Thank you for your time and efforts.
A signal is sent from a transmitter on Mercury's surface while it is at its greatest western or eastern elongation. The signal is ...
- 71
3
votes
2
answers
104
views
How can we practically measure the perihelion/aphelion of a solar system planet from scratch?
I've searched online for an answer, but they all seem to require other parameters (e.g, eccentricity and semi major axis) to be able to mathematically solve for the perihelion/aphelion. If we don't ...
- 627
6
votes
1
answer
90
views
Do solar flares have a noticeable effect on asteroid orbits?
I've read that in advanced trajectory calculations, sunlight is even taken into account. Does this also apply to transient events like solar flares?
- 1,542
-1
votes
1
answer
81
views
If 16 million kilometers were added to Earth's semi-major axis, what measurable effect would there be on Mars' orbit?
I have some education in astronomy, but nothing extensive in astrophysics. I can follow mathematical procedure with assistance. Procedural responses are most welcome!
- 71
4
votes
2
answers
265
views
Could a planet theoretically have a stable orbit between Venus and Earth OR Earth and Mars
Take a planet, identical to Earth in size, mass, gravity, rotation, etc.(but without the moon). Could this planet theoretically maintain a stable orbit for many hundreds of millions of years orbiting ...
- 141
2
votes
1
answer
62
views
How would the synodic period of Venus appear to change if both planets were moved 10 million additional miles away from the Sun?
Let us say that Earth and Venus are both moved 10 million additional miles from the sun. How would the synodic period of Venus appear to change for an observer on Earth? If 584 days is Venus' current ...
- 71
2
votes
1
answer
142
views
How can I calculate the luminosity and mass of a star only knowing it's peak wavelength and it's subtended angle?
For example if a certain star subtends an angle of 32 arcminutes at the Earth’s orbit and it's light has a peak wavelength of 500 nm, how can I find the luminosity and mass of that star?
- 57
7
votes
2
answers
2k
views
What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?
I was pondering this question recently, but most sites I can find only mention the speeds/velocities of the planets around the Sun when I look for 'orbital velocities' of the planets.
I tried ...
- 4,159
4
votes
1
answer
240
views
Velocity Verlet algorithm creating odd orbits
I am using the velocity Verlet integration to make an N-Body simulator but the results are odd. If I use simple Newtonian physics I get a closed orbit (btw im testing with 2 planets at first) but if I ...
- 43
2
votes
0
answers
23
views
Confused about the derivation of the x co-ord of the focus in the Lambert solution? [closed]
I'm looking into how the Lambert solution works but there's one bit I'm stuck on. From Wikipedia's Lambert's problem; Solution for an assumed elliptic transfer orbit (starting at Eq. 11):
I don't ...
- 21
4
votes
0
answers
87
views
Why does the axis tilt (obliquity) of Earth change over time?
I have recently learned that the polar axis of Earth moves in a complex fashion. There are both precession and nutation. I have learned that Earth's obliquity varies between 22.1 and 24.5 degrees on a ...
- 141
5
votes
2
answers
155
views
What is Mercury and Venus’ apparent retrograde motion?
I was having a discussion about Mercury being in retrograde, and I had explained it as Earth moving faster tangentially than Mercury so it looks like it’s moving backwards when we compare it with the ...
4
votes
1
answer
152
views
Why are what end up being meteorites not in stable orbit as planets and large asteroids are?
We don't have to worry about Mars, etc. hitting Earth. Is it that, being smaller, small asteroids have less inertia and so are more affected by, I guess, the gravity of various planets?
- 141
15
votes
3
answers
6k
views
What is the **actual** average distance of the Moon from Earth?
The Moon orbits Earth at a semi-major axis of 384400 km, with its periapsis being 363300 km and apoapsis being 405500 km. (All figures from this NASA fact sheet.)
If the Moon orbited Earth at a ...
- 2,413
1
vote
0
answers
242
views
Nbody problem solving on python with Leapfrog
I am relatively new to astronomical programming and I am trying to code a simulation of the solar system as simplified as possible on python. To do so, I am using numpy in order to have one array ...
- 11
9
votes
3
answers
1k
views
How time-symmetric is orbital mechanics?
Kepler's first two laws tell us that in a two body orbit in which one of the bodies is much more massive than the other, that:
The smaller body orbiting the larger body has an orbital path that
...
- 15.6k
2
votes
1
answer
139
views
How to calculate the minimum number of satellites needed to maintain constant link between themselves? [closed]
Suppose we want to build a number of space stations, all orbiting Earth at the same altitude, equally distanced from one another, and with the same inclination. How many of those stations are needed ...
- 627
-2
votes
1
answer
971
views
Angular velocity of planets around Earth, and Sun
What are the values of angular velocity of planets around Earth, and Sun? I am looking for these two sets of values.
- 545
7
votes
2
answers
226
views
What is pseudo-synchronisation when a planet is orbiting a host star?
I understand the term synchronous rotation - when the plant spin frequency is the same as the orbital frequency. However, I've seen the term pseudo-synchronization coming up in a few places and I'm ...
- 597
5
votes
1
answer
118
views
If the Earth became tidally locked with the moon, would that last forever?
If the Earth and the moon became tidally locked, would this last theoretically forever (assuming no external gravitational force modifies their orbits, for example, ignoring the effects caused by the ...
- 341
7
votes
3
answers
144
views
Is there a limit to how many objects can orbit eachother in a chain?
I was wondering if there is a theoretical limit to how long a chain of orbiting objects can be, for instance you can orbit the moon which orbits the earth which orbits the sun which orbits the galaxy, ...
1
vote
1
answer
95
views
How is a comet visible when far from the Sun
The latest news tells of a super large "mega" comet C/2014 UN271 (Bernardinelli–Bernstein)
approaching the Solar System in about 9 years.
It must be very far from the Sun, so how do we ...
- 650
-2
votes
2
answers
221
views
Which is closer to the Earth, Phobos, Deimos or Mars? [closed]
Which one is closer to the Earth, Phobos, Deimos or Mars? None of the answers that I find actually answer my question.
4
votes
1
answer
339
views
What is a Keplerian frequency, why do we specifically say Keplerian?
I am assuming that it means the frequency of a planet on its orbit.
But why do we specifically say Keplerian? Is there some other kind of definition of frequency we use for astronomical bodies in ...
- 405
4
votes
2
answers
543
views
Deriving the apparent angular speed of a star
The angular speed of stars in the sky is constant but the apparent angular speed is not, due to the star moving faster on the celestial equator and slower near the celestial pole. The apparent angular ...
- 55
2
votes
0
answers
163
views
What is the relationship between true anomaly and solar longitude?
So, my ultimate objective is to map solar longitude values onto a pseudo-Gregorian calendar. I thought this would be simple, but it has turned out to be anything but.
I have asked several questions on ...
- 131
4
votes
2
answers
241
views
With only seemingly two measurements 30 minutes apart, how were astronomers able to determine that asteroid 2022 EB5's trajectory intersected Earth?
Earthsky.org's Asteroid discovered hours before Earth impact begins
Hungarian astronomer Krisztián Sárneczky at the Piszkésteto Mountain Station – part of Konkoly Observatory near Budapest – ...
- 31.1k
5
votes
1
answer
175
views
Discrepancy in Horizons planet ephemerides for equivalent times in TT and UTC in dates during 1969
I have recently been experimenting with JPL Horizons planet ephemerides web App, and found a puzzling discrepancy.
Horizons allows to specify the time at which the planet ephemerides should be ...
- 351
2
votes
0
answers
63
views
In a multi-planet system, what mechanism can cause the innermost planet's semi-major axis to increase?
I've been toying around with n-body simulations (using research-grade software) and I've noticed a particular effect in many of my simulations: In many arbitrary multi-planet systems I simulate, there ...
- 615
2
votes
1
answer
57
views
Meteroids escaping the system
So the sun or any star has a certain gravitational pull. Technically the gravity extends infinitely only it will just become really small. If there is a meteroid around a star how do I calculate when ...
- 53
2
votes
0
answers
176
views
Non-stable vs non-linear orbits
In orbital dynamics there are often two 'classes'- stable and non-stable, or periodic and non-periodic. Is this just a specific class of linear and non-linear harmonics? Would Klemperer's rosette ...
- 437
4
votes
1
answer
201
views
Why circularization of an orbit has longer time scale than tidal locking?
I'm trying to understand the basic physics of orbital evolution. I know that in a two-body system (a planet orbiting a sun for example), eccentric orbits become circular, and the spin of the planet ...
- 597
1
vote
2
answers
138
views
Planet's distance data from JPL Horizons - Mars Curiosity mission
I am looking for distance measurement in AU between planets and Earth.
E.g. For Mars, Current distance, or distance of Mars from Earth at any given datetime, along with minimum (closest approach), ...
- 545