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Questions tagged [rotation]

Questions regarding the action of or an object rotating along an axis.

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What maintains the high orbital eccentricity of many exo-planets near their sun?

Over the last decade we've discovered that many exoplanets not only have highly eccentric orbits, but also orbit very close to their sun. This is true of many classes of stars. I definitely have a ...
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Why doesn't the solar azimuth vary uniformly

For the past few dates, I've been observing the rotation of the earth around the sun and noticed that the azimuth of the sun doesn't vary uniformly throughout the day. The azimuth varies faster during ...
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Moon's revolution around the Earth and it's rotation around it's axis? [duplicate]

Does Moon rotate around itself while it makes one revolution around Earth or not?
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How to caclulate the chinese Three Gorges Dam impact on Earth rotation? [closed]

According to this January 2005 NASA JPL News item NASA Details Earthquake Effects on the Earth, the Three Gorges Dam has slowed down Earth's rotation by 0.06 microseconds per day. Having that weight ...
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1answer
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Are these real paths of planets as traced from Earth?

Few days a go, I came across these two pictures of paths of planets as observed from Earth. They have a perfect geometric shapes. Actually, to me they look so beautiful and perfect, that they appear ...
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How does a spinning black hole affect space-time compared to a non-spinning black hole?

I often see questions on this site that only apply to non-spinning black holes and often wonder how the answer would be different for a spinning black hole. As the title says, what are the major ...
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1answer
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Why is Earth's rotation considered fast?

I'm currently reading Atom (Krauss book), and in chapter 11 there is this text: This collision can explain many things, including the high rate of spin of the Earth (the grazing collision would ...
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1answer
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Are there known objects rotating at close-to-light speeds?

For example, $0.1c < v < c$? Is this actually possible? Background: is that true that the black hole in the center of the Milky Way rotates once per 20 minutes?
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The equation for calculating how many times Earth (or our solar system) has revolved around the Milky Way

I have seen it said on Quora and Reddit that it's about every 220-250 million years to go around the Milky Way from Earth. Wondering what the rough equation is for calculating it. That is, I guess, ...
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Why does the Sun have different day lengths, but not the gas giants?

The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force ...
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Official degrees of earth’s rotation per day

What is the official degree to one decimal point please, of the earth’s rotation in one single day. Can it be confirmed that it is exactly 360.0 degrees using official data? Thank you in advance.
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What causes random irregularities in the earth's rotation accounted for by dynamical time

I read in a book that the earth's rotation sometimes shows unpredictable irregularities(not caused by precession, nutation, tidal forces) which are accounted for using dynamical time. What would be ...
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Rendering asteroid orientation as seen from Earth

I am writing a program to render an asteroid as seen from various parts of the solar system. My goal is to roughly reproduce the image of Cacus according to information on its DAMIT detail page. ...
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How do we know that an exoplanet is tidally locked to the parent star?

Often in discussing exoplanets we hear that they are close to the parent star (usually a red dwarf) but then there's a caveat that the planet is tidally locked to that star and that that fact severely ...
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Is it possible for stars not to rotate?

I'm just curious about that the existence of non-rotating stars. Is it physically possible for a star not to rotate at all? Does magnetic braking eventually stop the stellar rotation?
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Will Earth at some point stop rotating anti-clockwise, stay still, and then rotate clockwise? [duplicate]

Will Earth at some point stop rotating anti-clockwise, stay still, and then rotate clockwise?
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If Earth suddenly stops rotating, will be thrown at 465 m/s? [duplicate]

If Earth suddenly stops rotating, will be thrown at 465 m/s ?
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1answer
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How a star's rotation affects a star in the main sequence?

I searched and have found that the questions mainly focus on neutron stars, white dwarves and black holes. This was not what I looked for. Basically, the bigger the star's mass is, the more intense ...
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2answers
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What is meant by sun's path through zodiac

I read somewhere that sun's daily course and complete cycle is visible in the ecliptic belt by zodiac constellations. I didn't understand what that means closest I could find online is: https://www....
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1answer
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Why is the shape of the Moon spherical? [duplicate]

The Moon does not rotate on its own axis. If I am right, for something to gain a spherical shape it has to rotate on its own axis. We know that the Moon does not rotate on its own axis. How can this ...
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Why don’t we feel the Earth rotating beneath us?

I’m not sure all of the details in the experiment but basically it went as follows. Someone marked their location of take off in a hot air balloon and went straight up in the air. They stayed ...
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1answer
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Cycles that are longer than the year, but less than 1000 years

Wondering what primary astronomical cycles there are that are greater than a year (which is a cycle around the sun), but less than 1000 years-ish (on that scale). There is the cycle of the moon phases ...
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2answers
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If a giant object would approach the Earth, would Earth start to turn faster or slower while the object starts to become nearer and nearer?

I am asking myself this question: if a giant celestial object would approach the Earth, would Earth start to turn faster (then day duration would be diminished) or slower (day duration increased) ...
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Does the rotation of galaxies precess?

Does the axis of a galaxy as a whole "wobble" the same way that the Earth does? If so do we have any idea how much or how fast the Milky Way is doing so?
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Can one detect from earth that angular momenta of its axial rotation and its orbital rotation are “almost parallel”?

I mean that the angle between these angular momenta is acute as opposed to obtuse (23.5 and not 180-23.5), so that the rotations are "roughly in the same direction". Related but distinct question -- ...
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2answers
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Can a planet's changing tilt be aligned with the rotation around its star? [duplicate]

What I'm asking is if the tilt of a planet can "follow" the rotation around its star so that, for example, its north pole would always lean towards the star, and thus always be under daylight. The ...
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1answer
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Identify Greek letters used in formulas [closed]

Could anyone tell me what the names of the Greek letters in the screenshot are? Is the first one alpha? They are used in calculating ICRF rotations. Wikipedia uses a different font for their list of ...
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Modeling planet rotations (time of day, obliqueness, etc.)

I created this solar system model using POV-Ray: by following these instructions: https://ssd.jpl.nasa.gov/txt/aprx_pos_planets.pdf The next thing I want to do is orient/rotate each globe correctly ...
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1answer
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What is the difference between the Yarkovsky effect and YORP effect?

As far as I understand, both the Yarkovsky effect and the Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect exert forces upon bodies as a result of thermal photon radiation. How do both effects ...
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1answer
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Is it possible to define a state of zero absolute angular momentum anywhere in the universe?

Conservation of angular momentum doesn't seem correct to me. I think this because radiation is present everywhere, no space is completely void, and no object perfect. Thus all objects will have uneven ...
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1answer
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Relationship between galactic rotation and stellar lifetime

I have read that the lifetime of stars is much less than the period of rotation for a spiral galaxy. For example https://www.coursera.org/learn/evolvinguniverse/lecture/wlYhz/the-origin-of-spiral-arms ...
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2answers
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Are harmonic relationships among the rotation periods of the planets well known? Are they factors in other planetary phenomena? [closed]

Every 39.88 minutes 10 degrees ($\frac{360^\circ}{36}$) of arc passes over the zenith. It can also be stated that the 36th harmonic of the rotation period of the earth (1435.8 min) is equal to 39.88 ...
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Which direction do the constellation revolve in?

If I am standing looking towards the East from the Northern Hemisphere, do the constellations appear to rotate towards the West via the North or the West via the South or am I completely off target ...
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How can a rotation period of a planet's satellite/moon be “chaotic” (like Hyperion around Saturn)?

According to wikipedia (see info below image) Hyperion's rotation period around Saturn is "chaotic". What does that mean? The period (in days/hours) is different every rotation without any law ...
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2answers
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Why isn't the Sun hollow? [closed]

[Edited to remove incorrect geological assumptions] The sun is self-rotating, i.e. it spins on its axis. When something spins, there's an apparent force away from the centre, and matter gets flung ...
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3answers
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angle to the equator of the Sun on sky at a given time

Is there an easy way to tell at what angle the solar equator is wrt the horizon at any given time of the day? I would think that it rotates 180 degrees from sunrise to sunset, but not in a linear ...
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2answers
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Does Polaris have a trail in the sky timelapse?

I came across few sources that claim Polaris movement cannot be observed with the naked eye. But then, I saw images of the star trails (timelapse), and they clearly show Polaris not quite at the true ...
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1answer
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Do the number of moons a planet has affect the speed of the planet's rotation?

Would the tidal forces of multiple moons interacting upon a planet speed up or slow down the day length of the planet? I was thinking that maybe the planet's day length would be slowed down due to all ...
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How can I calculate how far through the day the prime meridian is of different planets

I'm trying to create a widget that shows the 'time' on different planets. It will show how far through the day/night cycle (as a percentage) a point on the planet is. It has been easy to scale down ...
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If the Earth is rotating counter clockwise, how does the sun rise from east?

I was very confused when I watched this video from 2:18 till 2:45. And it seems very clear that if the Earth is really rotating from west to east, shouldn't be the Sun rising from west and setting in ...
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IAU rotation model

I'm looking at this IAU WGCCRE Report: http://aa.usno.navy.mil/publications/reports/Archinaletal2011a.pdf It gives expressions for Earth orientation relative to the International Celestial Reference ...
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Why most planets don't spin retrograde? [duplicate]

Edit: just found duplicate Since orbital velocity is greater on small orbits, and smaller on large orbits, why don't planets spin retrograde around their own axis? One portion of planet's mass is ...
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Any method to apply inverse TPoint model?

I have an automated telescope that I have written some software for. I am currently using TPoint to compensate for some of the irregularities of my system. However with TPoint you apply an offset (...
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2answers
178 views

Circular velocity in axisymmetrici potential [duplicate]

If a matter distribution is spherically symmetric, the circular velocity is straightforwardly related to the mass via: $v_{circ} = \sqrt{GM/r}$ In an axisymmetric potential, on the other hand hand, ...
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1answer
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What contributes the most to the seasonal temperature variation?

The seasonal temperature is ultimately due to the precession of the Earth around the axis. But what I'm curious about is... is it due more to the side experiencing winter being farther from the sun ...
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What are evidences of stationarity of rotation of galaxies

Recently I have found the article Does There Really Exist the Problem of the Dark Matter in Spiral Galaxies? which states that dark matter does not exist because astronomers are wrong assuming ...
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Earth shape and rotation

Imagine a helicopter that took off from point A and goes vertically in the air to a certain fixed point B in the atmospheric area at a certain fixed altitude with enough fuel to stay there (at point ...
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Why do certain moons have their rotational period equal to their orbital period?

Our moon and Saturn's moon, Titan, have this feature. Because of this we only observe one side (hemispere) of our moon. Why is this? What is the Newtonian or astrophysics that would explain this? ...
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Is the Sun prograde or retrograde with respect to the rotation of the Milky Way?

I recently learned about the terms prograde and retrograde. I've seen these terms used to describe the rotations and orbits of moons with respect to their planet, and planets with respect to their ...
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Does the Abell 1689 supercluster have angular momentum?

The Abell 1689 is a large group of galaxies, containing a lot of elliptical galaxies : https://en.wikipedia.org/wiki/Abell_1689 Usually, an elliptical galaxy don't have large angular momentum around ...