Questions tagged [orbit]

Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.

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Time taken calculation to reach synodic degrees between planets

I have a software tool which calculate the synodic period with degree inputs with two planets. Synodic Period is the temporal interval that it takes for an object to reappear at the same point in ...
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3 votes
2 answers
472 views

Is this scaling of JWST halo reasonably correct

After thinking about accurately visualizing the size of the Andromeda galaxy I began to wonder about the halo orbit of the James Webb Space Telescope. Using an estimate of 1.5E6 km for halo width and ...
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3 votes
1 answer
194 views

When exactly was the last time that Earth's aphelion coincided (within 24 hours) with the northern winter (December) solstice?

I would like to know in what year precisely did Earth's aphelion coincide (within 24 hours) with the northern winter (December) solstice? From what I understand, the day (on any tropical calendar) on ...
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7 votes
3 answers
661 views

How can I calculate an orbital elliptic trajectory from the velocity vector?

I have been struggling for a few days with this. I know just my distance from gravity origin, gravity source mass and my actual velocity vector on the orbit. Can I calculate whole trajectory with this?...
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0 votes
1 answer
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Calculate how many days left for synodic period from particular planet

One of the many tools used in Astronomy are the formulas used to determine Orbital Motion. There are two basic forms of orbits: Sidereal Period Synodic Period For Jupiter: $$\mathrm{\frac{1}{P} = \...
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15 votes
3 answers
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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 ...
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1 vote
3 answers
230 views

Is there a Lagrange point between the earth and the moon?

Is there a Lagrange point between the earth and moon where a space station could sit forever without orbiting around either? Just curious, but it seems like a place like that would be perfect for ...
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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 ...
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1 answer
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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 ...
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-3 votes
1 answer
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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.
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1 vote
2 answers
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Comet Bernardinelli-Bernstein; could it be a "planet-killer" and what could prevent it from getting close to us?

The huge "mega" comet C/2014 UN271 (Bernardinelli–Bernstein) 80 miles wide is coming towards Earth from the edge of our Solar System. It is supposed to only get to the middle of our Solar ...
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7 votes
3 answers
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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, ...
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18 votes
3 answers
3k views

What is this 877-year cycle in the orbits of Jupiter & Saturn, and this multimillion-year cycle in the lunar orbit?

The book The Theory That Would Not Die (by Sharon Bertsch McGrayne, 2011) states the following on page 28: He [Pierre-Simon Laplace] used other methods between 1785 and 1788 to determine that Jupiter ...
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17 votes
2 answers
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On Mars, why are the seasons "strongly amplified" in the southern hemisphere and masked in the northern hemisphere?

In the Darian calendar entry on Wikipedia we read (emphasis mine): The Martian year is treated as beginning near the equinox marking spring in the northern hemisphere of the planet. Mars currently ...
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1 vote
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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 ...
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3 votes
0 answers
40 views

What's the angle between the sun's galactic speed and the ecliptic?

I know the sun wobbles up and down the galactic plane around 35myr. I don't mind about that component. I'd like the know the angle between the linear speed of sun around the Milky Way (just the ...
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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 ...
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7 votes
4 answers
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Units for orbital period and gravitational constant

Using this site for binary system orbital period calculations: https://www.omnicalculator.com/physics/orbital-period The formula given there is $$T_{binary} = 2 \pi \sqrt{\frac{a^3}{G (M_1+M_2)}} $$ ...
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6 votes
2 answers
208 views

The moon rises at a different time each day, but that difference changes. Why?

Let's say the moon rose at 5pm yesterday and 5:30pm today. The difference is 30 minutes – but that difference changes from day to day and can be anywhere between twenty-some to seventy-some minutes. ...
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orbital periods from mean longitudes

Is it a common practice in Astronomy to obtain orbital periods from mean longitudes? Do they use different techniques for different types of bodies?
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3 votes
2 answers
98 views

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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1 vote
1 answer
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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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1 vote
2 answers
89 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), ...
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What is the current radial position of the sun within the Milky Way relative to the MW's movement towards the Great Attractor?

If we imagine the Milky Way's movement towards the Great Attractor as the 0-rad mark on a disk parallel to the movement with a center at the Milky Way center, do we know roughly at what radian value ...
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4 votes
1 answer
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Why do stellar-mass black holes fall to the centers of their galaxies? [duplicate]

This answer here says that black holes will "sink" to the centers of the galaxies they're in. How does this happen? It's not like there's a buoyant force in the vacuum of space. Shouldn't ...
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-2 votes
1 answer
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Is it possible that Planet 9 was thrown out of the Solar System? [duplicate]

Is it possible that this planet changed other planet orbits (from which we assume that it exists) but then was thrown out of the Solar System in past when Sun was close to some other star? And it ...
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10 votes
1 answer
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Why is the L1 point (Lagrange) almost 1 million miles from Earth? Shouldn't it be closer to us?

Try to follow my simple logic: The Sun is almost exactly 333,000 times as massive as Earth, and gravitational strength increases linearly with mass, so the Sun's gravity is about 333,000 times ours. ...
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19 votes
1 answer
5k views

Is it possible to have a stable 3 body system that orbits in a perfect circle?

I.e. a system that has 3 objects of equal mass, rotating around the system's center of gravity like so: Please excuse the crude drawing, but I've just been reading The Three-Body Problem book by Liu ...
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1 vote
0 answers
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Convert Earth-centered coordinates to rotating libration point (RLP) coordinates?

I'd like to plot the path of an object near L2 (like the Webb space telescope) in a rotating libration point coordinate system. That makes it is easy to distinguish halo orbits from more general ...
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27 votes
5 answers
6k views

Can a planet with no atmosphere be orbited at extremely low altitudes?

Can a planet that has absolutely no atmosphere be orbited by a spacecraft at extremely low "altitudes" (if you'd even call it altitude at such a low orbit. For instance, if this planet's ...
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1 vote
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What is the skypath of JWST?

JWST will be in a 6 month halo orbit around the Sun/Earth L2 point, which is located at the anti-solar point. Internet graphics give conflicting information on whether the skypath is clockwise or ...
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3 votes
1 answer
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Is it still called an orbital resonance if the ratio is irrational?

Previously, I asked At what point are orbital resonances no longer "ordered" but "chaotic?", and received an answer from @CarlWitthoft: Perhaps if the calculated fraction had an ...
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8 votes
2 answers
730 views

At what point are orbital resonances no longer "ordered" but "chaotic?"

Orbital resonances are typically in small valued integer ratios, like 2:1, 3:2, or 4:7. However, there are some resonances whose ratios have large reduced values, including the 73:69 Naiad:Thalassa ...
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6 votes
2 answers
197 views

What is the maximum latitude from which a satellite in a geostationary orbit around Saturn would be visible to an observer on the planet?

This question is part astronomy and part mathematics. I'm aware it involves “basic” trigonometry, but my brain is short-circuiting. From my calculations, the distance from the center of Saturn where a ...
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2 votes
2 answers
171 views

Incorrect Mars orbital time while calculating using Kepler formula in Java

Question: I am trying to make a simple java program to do planetary orbital calculation like how many days it takes to complete the orbital along with each Earth day data but I end up getting a 4 ...
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5 votes
1 answer
657 views

How long would it take to realize there are "star-like objects" (i.e. planets) that change position in respect to the "fixed stars"?

If you were using unaided observations and were unfamiliar with astronomy (and maybe just pen and paper for recording anything), how long should it take to notice that Mercury, Venus, Mars, Jupiter ...
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4 votes
3 answers
113 views

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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6 votes
1 answer
229 views

What's the difference between the Roche lobe and Roche sphere?

I am just beginning to look into this topic, so apologies if there are any striking misconceptions in the following. From Wikipedia, the Roche lobe is "the region around a star in a binary system ...
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5 votes
1 answer
234 views

Would a system consisting of Earth and Venus orbiting around a common center be stable in the long-term?

Earth and Venus and very close to each other in mass and would both orbit around a point in space positioned almost perfectly in between the two. Assume that this system is 1 AU from the Sun and the ...
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7 votes
2 answers
121 views

Could stars like S2 near the galaxy's center have planets in a stable orbit?

I read about one of the stars orbiting Sagittarius A* and according to Wikipedia, it reaches a maximum speed of 0.03c during its orbit. Would this (or any other factor) make it impossible for a planet ...
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11 votes
1 answer
783 views

How close to escape velocity are most Oort-cloud comets?

User @antlersoft wrote a nice answer to my question on the difference between barycentric and heliocentric models of the solar system when applied to comets (edge cases of the systems). In a comment, @...
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7 votes
2 answers
270 views

What is the difference between barycentric-centered and heliocentric-centered coordinates?

When talking about celestial bodies orbiting the sun with a decently circular orbit or small aphelion, the heliocentric orbital parameters are almost identical to the barycentric parameters. However, ...
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3 votes
0 answers
104 views

What was "wrong" about the motion of Neptune in 1984?

The cover story of the March 1984 issue of RUN, a popular computing magazine, was written by noted astronomer Charles T. Kowal. In the article, he describes how he uses his home computer, a Commodore ...
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2 votes
1 answer
73 views

Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?

If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles.... BUT, it is the precession of the periapses that is off, not 'just' its ...
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2 votes
0 answers
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Why are triple conjunctions in a resonance forbidden?

I was reading the Wikipedia article about orbital resonance and noticed that Laplace resonances forbid triple conjunctions. This seems to be supported by the Io-Europa-Ganymede system and the Nyx-Styx-...
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9 votes
2 answers
1k views

Repetition of orbital structure on many scales - what is it called?

I'm certainly not the first to notice this, but there is a commonality between the structures of objects in space at different levels of magnification. For instance... The moon orbits earth... The ...
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1 vote
1 answer
84 views

Why is there a deviation between the ratio of $a^3$ and $T^2$ for the outer planets?

The Wikipedia article about Kepler's third law includes a nice table about the ratio between $a^3$ and $T^2$. However, for Mars, Jupiter, Saturn, Uranus, and Neptune, the ratio $\frac{a^3}{T^2}$ in $...
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8 votes
2 answers
454 views

How was the speed of the Sun (around the Milky Way Galaxy) calculated?

The Sun travels around the Milky Way Galaxy with a speed of 220 km/s. The question is: where did this value come from? Is there any article about the calculation? Reformulated question: What are the ...
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3 votes
1 answer
181 views

Are intersecting orbits ever stable?

Ok, I'm asking this question because the obvious counterexample is trojans. Trojans typically intersect the orbit of its relative body. Typically, these are stable in the long-term, especially when ...
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1 vote
0 answers
31 views

Average DeltaV applied to a comet during outgassing?

Comets' orbits often change during perihelion passage due to the outgassing of volatiles. So I am wondering, how much change in velocity is applied each perihelion pass? What does this depend on?
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