Questions tagged [orbit]

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

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6answers
3k views

If an exoplanet transit we are seeing is 13000 light years away, are we seeing a 13000-year-old orbit? [duplicate]

If a star is 13000 light years away, doesn't that mean we are seeing 13000-year-old light? If it does, then does that mean when we discover a planet with dimming star light, we are seeing a planet ...
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“Periapsis” or “Periastron”?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
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After what time interval do the closest approaches of Mercury to the Earth repeat?

The sidereal period of Mercury's revolution is 88 days and the synodic period — 116d. my solution, but in the question featured "the greatest rapprochement." And this is no longer so easy. ...
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1answer
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How does the gravitation of Jupiter or other big planets affect Kepler's third law?

Does anyone know a good reference for this? I once read how Jupiter's gravitation can be treated as a perturbation. I think they expanded Jupiter's gravitation as an infinite sum of one of the special ...
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1answer
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Do planets have effect on velocity of Earth?

There is method for finding extrasolar planets called Transit-timing variation. If I understood correctly, exoplanets accelerate or decelerate each other (according on their position), so we can ...
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1answer
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Do space objects stay in orbit once they get sucked in? Can they escape?

Think of my question with respect to 2020 CD$_3$ minimoon that's been recently discovered. If an object gets caught into a planet's orbit, can it ever escape it? Obviously it may escape on the first ...
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How small could an orbital system be in our solar system?

Answers to How does the Sun's gravity have so much force and pull on the solar system? How does it scale? Newton's law of gravity scales on orbits so that we can theorize very small orbits with very ...
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1answer
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Is a trefoil orbit around a trinary star valid?

Recently, I have been experimenting with weirdly-shaped orbits with a program called "My Solar System 2.04." While looking for interesting orbits of a spacecraft in a trinary star, I found ...
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How to get the longitude of the perihelion to find the Heliocentric Equatorial coordinates of a planet

I'm writing a program to randomly generate star systems and I have been having a difficult time figuring this out. I've found the equations I need to get the heliocentric equatorial coordinates, but I ...
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1answer
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How to project an arbitrary elliptical orbit onto the night sky plane?

An ellipse E is arbitrarily oriented in 3-D space with the origin at one of its foci. Use the standard elements provided in the figure. Assume the reference direction $\gamma$ or $\gamma'$ is the ...
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What makes protoplanetary disks start rotating? (Initial energy needed to rotate)

Planets form from a protoplanetary disk that has been rotating around its star. The initial energy that makes them rotate really matters to me. Why did the protoplanetary disk start rotating around ...
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1answer
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Throwing a baseball from orbit to the earth

I just read a thought piece about what a war in space may look like, and it changed my thoughts on what orbit actually is. From what I read about orbits, it sounds like going faster in the velocity ...
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Why are orbits elliptical instead of circular?

Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
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If suddenly “knocked” or perturbed from its orbit, would gravity eventually return the Earth to its original orbit?

If suddenly "knocked" or perturbed from its orbit, would gravity eventually return the Earth to its original orbit? I am curious as to whether this is even possible. It seems to me that ...
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How does an object at L1 stay at L1?

I've recently been reading about the DSCOVR satellite, and I'm confused about it's orbit. According to NOAA A million miles away, DSCOVR orbits a unique location called Lagrange point 1, or L1. This ...
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Positions of planets before Christ?

All the solar system simulations I've come across showing the positions of planets only show the positions in a certain time period, at beginning of the first millenium the earliest. There was just ...
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How does a gravity slingshot actually work?

From what I know of elliptical orbits, an object speeds up near the periapsis and slows down at the apoapsis, much like we learned in high school physics how a sphere would roll down and back up a ...
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What are “non-Keplerian” orbits? What are some familiar examples in our solar system, and can some still be closed?

This excellent answer to Forms of stellar orbits around the galactic center invokes the following concepts: non-Keplerian orbits closed orbits I have a fairly good idea what these mean and so might ...
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What would a moon with a six-month orbital period look like from the earth?

This is a kind of follow-up question to "What orbital period would produce one New Moon (and one Full Moon) each year?" Given the six-month orbital period that is needed to produce one New ...
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1answer
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Is there anything like a timelapse showing the Alpha Centauri stars orbiting around each other?

It is my understanding that the angular separation between Alpha Centauri A & B is more than enough for even amateur telescopes to resolve as 2 separate stars. Going by the plot below, over the ...
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If the Moon were impacted by a suitably sized meteor, how long would it take to impact the Earth?

An answer to the question of How well would the Moon protect the Earth from a Meteor? mentions as a possibility that the Moon could get knocked into the Earth. What is the smallest change to the ...
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What point does Earth actually orbit?

If we consider the two largest masses in our solar system - the Sun and Jupiter, by themselves, they will orbit a common barycenter which is somewhere offset from the Sun's center in the direction of ...
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What shape do satellites trace as they wobble in orbit around another body?

What shape does the center of gravity of a satellite trace in 3-d space as it wobbles in orbit around another body? How is this shape modeled geometrically? Is it a topological torus? Is it feasible/...
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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 ...
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Circular orbits

First of all, I'm studying orbits for a hobby: world building. Unfortunately, my mathematical abilities approach a ridiculous low threshold, which means I am stuck with reading the simplest ...
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Why do the planets orbit in the same direction?

Theoretically, planets would have an approximately equal chance of going one way in their orbit or another but in reality, this is not the case (at least in our solar system). Why is this?
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What orbital period would produce one New Moon (and one Full Moon) each year? What other effects would this produce?

I am interested to know whether it's possible for the moon to orbit the earth at such a rate that we would see only one New Moon and one Full Moon a year. If so, what other effects would we experience?...
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Ramifications of black hole stellar system

Recently, I got around to seeing the movie Interstellar. In it, the characters of the movie visit a stellar system that appears to be built around a black hole instead of a star. On top of this, their ...
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Is the “mean orbit” centered on ellipse center or ellipse focus?

Mean longitude and mean anomaly of a body are calculated as the angle covered by the body along a fictious circular orbit, and this is ok. But where is this orbit centered? Five different sources say ...
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Orbital Mechanics: where can I find initial conditions for orientations and angular rates of planets in our solar system?

I am looking to write the equations of motion (EOMs) for a 6DOF analysis of our solar system. I want to integrate the equations forward in time, and need a complete set of initial conditions to do so....
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Do we know if there are asteroids leading or following Earth in Earth's orbit around the Sun?

A search of the Internet is so clouded with discussions about the asteroid belt or asteroids orbiting the planet Earth that I couldn't see an answer to my question. Do we know if there are asteroids ...
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Does the Milky Way orbit around anything?

We know most of the objects in the Universe have a spherical or elliptical shape. The object which has less mass and gravitational pull orbits around the nearest object with more mass and ...
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Does Halley's Comet travel past the outer bounds of the Oort Cloud?

We know Halley's Comet returns every 75-76 years. We can reasonably compute its elliptical orbit. We know that the Oort Cloud is a cloud of predominantly icy planetesimals proposed to surround the Sun ...
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Does Sun have a reflection on Earth?

The new Google Maps1 presents an actual view of Earth, with the current position of Sun illuminating half part of Earth in real time. It is quite an exquisite view. My question is based on the ...
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1answer
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Cannot identify mistake in calculating orbital eccentricity vector; magnitude equals one instead of zero (with python code)

I have a gravitational nbody simulation, for which I would like to determine various orbital parameters. For each body, I have 3-D vectors (x,y,z -space) for position, velocity, and acceleration. I am ...
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1answer
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Exercise: 2D orbital mechanics simulation (python)

Just a little disclaimer beforehand: I have never studied astronomy or any exact sciences for that matter (not even IT), so I am trying to fill this gap by self-education. Astronomy is one of the ...
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1answer
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To several decimal places, how many days are in one year?

This morning I was interested in finding out how many days are in one year on average, to several decimal places (because I am a mathematician, so I like to be accurate). Unfortunately, Googling the ...
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1answer
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Why is the height of a satellite greater than the apogee of its orbit?

I read in the German Wikipedia for the Indian Technology Experiment Satellite, that the apogee (Apogäumshöhe) is 567 km, while the height of the orbit (Bahnhöhe) is 572 km. I had always thought that ...
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1answer
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What is the tightest orbit binary planets can orbit each other?

If there were two Earth-like planets in a tight orbit around each other, how close could they be to each other without colliding? How quickly would they have to orbit to be stable? Would they be ...
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Why is the time between equinoxes different?

The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse. Since an ellipse, by definition, is symmetrical with respect to the foci, I ...
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Was the Geocentric Model correct at all?

It's easy to find resources stating that the heliocentric model is right and geocentric is wrong. But how wrong was it? Was it correct in any way? It was built on incorrect assumptions, but despite ...
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1answer
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Why do the planets in our solar system orbit in the same plane?

(Yes I'm excluding Pluto from this the same way it was excluded for not being a planet) Observing the planets orbit of the Sun they all seem relatively planar and roughly all orbit along the same ...
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1answer
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Is there a possibility of finding a system where a star is orbiting a planet?

Is it possible for a star to orbit a planet IF the planet is bigger than the said star? Or is it possible even if the star is bigger than the planet and still the star is orbiting the planet? I have ...
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0answers
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How is solar radiation pressure included in the SGP4 orbital propagator?

TLE sets serve as input elements for the SGP4 orbital propagator. Several orbital perturbation effects are considered in the SGP4. However, it is not obvious to me how (or if) the solar radiation ...
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2answers
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What is exactly the “longitude of the perigee”

Some moon phase calculation algorithms (apparently derived from Duffet-Smith's book, example here) seem to use a parameter called "longitude of perigee at epoch". What exactly is this? Can I assume ...
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Is there an optimum orbit for a Hipparcos/Gaia-like parallax observatory

The Gaia spacecraft is currently mapping the stars in the Milky Way by parallax. It orbits in the Earth-Sun L2 Lagrange point. The parallax observed from the spacecraft orbiting around the sun allows ...
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Have Earth, Mars and Jupiter and Neptune not cleared their orbits of space debris? [closed]

According National Geographic's Space Encyclopedia (p68, column 3) written and illustrated by David A Aguilar Pluto has not cleared its orbit of space debris but neither have Earth, Mars, Jupiter and ...
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2answers
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Could there be a planet at the barycenter between two or more stars revolving around each other?

In binary star systems, could there be a planet the stars revolve around, with eternal day on all sides? 1st scenario: Imagine a binary system consisting of two Sunlike G5V stars of 1 solar mass each, ...
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2answers
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Planet orbit circumbinary planet

I was wondering about a planet who orbits two stars. Could it be that it moves as in the image?
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How long for a complete solar system cycle

Considering the solar system as a closed system, how long until all the planets pass twice by the same position relative to each other? I would say that you'd have to get the length of the year in ...

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