# Questions tagged [rotation]

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

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### What can we learn from the rotation data of a star?

Knowing the speed of a star's surface rotation gives us what data and information. For example, if it is a big star, is it possible to measure distance using the doppler effect? Or can we calculate ...
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### How to model galactic rotation curves?

I have R (kpc)- distance from galactic center and v(km/s) rotational speed at that distance. I was thinking of creating a simple model comprising of 3 terms 1 for Keplerian component another for rigid ...
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### Where can I find galaxy rotational data?

I want to do a small project of generating rotational curves for different galaxies, and need data for some prominent stars in other galaxies (data needed: distance from center, rotational velocity) ...
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### Rotation direction of Pulsars

Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. It has a very strong magnetic fields which funnel ...
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### What else can we learn from a Foucault pendulum? Have they ever been used to determine anything more than that the Earth rotates on its axis?

Background Each semester we have to make up projects for each course. This semester I took Cosmology and Astrophysics and we covered a vast amount of topics, from luminosity of stars to Einstein's ...
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### Earth’s rotation speed vs rate of lunar cycle

Hypothetical Question If the earth’s rotation slowed down to align to the lunar cycle so that the orbital period began and ended at the same lunar phase, what other things would result? For example, ...
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### Does Earth's rotation cause any structural changes in the Earth? [closed]

I tried searching for this and while all results talks about changes of day and night, impact on direction of wind, cyclones, etc, they do not say whether it causes any structural changes in the long ...
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### Why would a freezing liquid layer accelerate a rocky body's rotation?

Titan, whose orbital period is 382 hours, is tidally locked, like all round moons in the Solar System. But Jonathan I. Lunine said of Titan: One thing that Titan could not have done during its ...
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### Could a magnetosphere be created for Venus by recreated by spinning-up the planet to a 24 hour day?

If Venus in it is current state, started rotating at the same rate as Earths 24hrs rotation, would it develop a magnetic field of roughly the same strength as Earth's? If so, would that help in any ...
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### If planets are ellipsoids why don't we have 3 diameters?

We know that each ellipsoid has 3 diameters named $2a$, $2b$, and $2c$. The Earth and all planets, in general, are ellipsoids (Saturn is the best example because it's the most oblate planet in the ...
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### The orbital period of Jupiter and Europa billions of years later

We know that the Sun gets so big billions of years later and the Earth will get destroyed. What will the orbital period of Jupiter (Sun-Jupiter system) and its moon Europa (Jupiter-Europa system) be ...
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### Databases for galaxy luminosity profiles and velocity rotation curves

I'm looking for databases of the following for a variety of different galaxies, but have so far struggled to find anything. Any help hugely appreciated. Firstly, I'm looking for observations which ...
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### Why does a timelapse video of a stationary Milky Way make the horizon appear to move from horizontal to vertical?

In this video, with a rotating camera keeping the Milky Way 'stationary,' the horizon appears to transition form horizontal to nearly vertical. I understand the Earth ...
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### What rotational speed would Mercury need to have to achieve a temperature comfortable for humans

I wondered what rotational speed would Mercury need to have to achieve a temperature comfortable to humans, let's say 20 °C. EDIT: My idea was that if Mercury is so cold on the night side and so hot ...
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### Is there any difference between tidal locking and synchronous rotation?

I'm trying to understand more about orbital mechanics, and I'm encountering a few terms which I'm not sure if they are exactly the same. The two terms are Tidal Locking and Synchronous Rotation. To my ...
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### Am I looking at the moon upside down here in the US?

This may be a very basic question, but I just learned that the moon orbits around the earth counterclockwise. I always thought the earth and the moon shared the rotation and orbit direction. Since the ...
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### Would tidally locked Earth-like exoplanets necessarily have hot pole/cold pole atmospheric circulation?

A tidally locked planet orbiting a red dwarf star in its habitable zone would have a rotational period equal to its orbital period, on the order of days or weeks. Given a thick enough atmosphere ...
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### Has Altair flung off its planets by rotation?

This might be a dumb question, but would it be possible that during the star Altair's formation, the centrifugal forces became so large that its planets were flung away into space? Or could a passing ...
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### What is the exact reason for the Sun's differential rotation to occur?

The following is an excerpt from the Wikipedia article for "Differential Rotation": Differential rotation is seen when different parts of a rotating object move with different angular ...
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### Solar Rotation Varies with Latitude. Effects?

From the Wikipedia article of "Solar Rotation": Solar rotation varies with latitude. The Sun is not a solid body, but is composed of a gaseous plasma. Different latitudes rotate at ...
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### Axial Tilt One or Two Angles

Why is the axial tilt of a planet expressed as a single angle when two angles are necessary to specify a point on a sphere? Imagine if the Earth’s axial tilt were 90 degrees, then the axis of rotation ...
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### Do relativistically measured rotation speeds (Special Relativity) change planetary mass slightly through Lorentz transformation?

Thanks @ConnorGarcia for your Answer. Avoiding 'Tidal Locking' for now - the rotational angular momentum Lrot is 10,000,000 times smaller, so negligible, but could it still be a factor in eccentricity?...
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### Is the 'spin' of Earth and the 'spin' of Mars a significant contribution to their angular momentum?

Is the 'spin' of Earth and the 'spin' of Mars taken into account as a contribution to the conservation of angular momentum? (and a contribution to the increasing/decreasing eccentricity?) Or - is the ...
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### Can you compute the solar day?

For a given planet, if you know the sidereal rotation period and the sidereal revolution period, can you compute the length of one solar day? For instance, for Earth, if you know one rotation is ...
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### Special case of rotation period

Rotation period is either prograde, like the Earth, or retrograde, like Venus. How likely is it for a body orbiting its parent object (either a planet around a star or a moon around a planet) to have ...
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### If a black hole is spinning, does its singularity have a new name and what is the name? [duplicate]

Think of a spinning black hole. (Kerr black hole) Every black hole has a point of infinite density, called a singularity. When a singularity is spinning, does it have a different name? But when a ...
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### Can the pebbles growth model be applied to the rotations of planetary systems? [duplicate]

I've just read the University of Amsterdam 2019 News item Pebbles determine the direction in which planets rotate (which links to R.G.Visser et al (2020) Spinning up planetary bodies by pebble ...
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### When will Mercury have rotated an extra round around its axis?

It is well known that Mercury orbits slightly differently from a pure Newtonian orbit. Every year a slight deviation is found. Now if we observe a lot of these orbits then Mercury should at one point ...
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### Are there non-rotating objects in the universe?

All celestial bodies I can think of rotate. The sun, the planets, the moon, the galaxies, clusters of galaxies, the supermassive black hole at the center if the Milky Way, accretion discs, etc. It ...
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### How are constellations intact if the stars are rotating around galactic nuclei?

From what I understood, the Milky Way (or stars in the Milky Way) doesn't rotate like a collection of points in a disc due to the presence of some invisible matter. In theory, the angular velocities ...
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### App Stellarium and hourly wobbling motion of Neptune

In Stellarium when I zoom in on Neptune to be able to see your daily rotation. I select Neptune, center it (space bar) and then make increments of one solar hour (command +). I notice that the axis ...
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### Does precession affect this measurement?

I don't have the astronomy vocabulary to ask this question. You can find a better picture at https://www.timeanddate.com/astronomy/axial-tilt-obliquity.html. I want to know if the distance between ...
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### Converting Invariable plane to J2000 ecliptic

I've been following the answer given by Mike G here: How to calculate the orientation of planets at current epoch to get planets to have the correct orientation in my program, but all the angles are ...
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### How galactic density falls using Oort constants

I am given the observations that Oort constants $A$ and $B$ are, respectively: $14.5 \text{km s}^{-1} \text{kpc}^{-1}$ and $-12 \text{km s}^{-1} \text{kpc}^{-1}$. From these, I am supposed to conclude ...
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### How would one estimate the rotation period of a star from its spectrum?

The figure is shown; the measurements were taken on two consecutive observing nights. The Ordinate is the flux normalized to continuum and the abscissa is the wavelength scale. You can see the "...
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### can i use heliocentric velocity as a rotation speed? [closed]

In the research of the galaxies, does heliocentric velocity involves space's expanding velocity? and can i use heliocentric velocity by galaxy's rotation speed?
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### Astrophysical black holes deviating from Kerr black holes?

Rotating black holes are formed due to the gravitational collapse of massive spinning objects. And, it is generally believed that Kerr black hole solutions are valid for the empty space outside of the ...
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### How is it possible for a collision to be responsible for Uranus's axial tilt?

I realize that the collision explanation is in any case highly (purely?) speculative, but I'm curious how it would work. If Uranus is a ball of gas, why wouldn't any colliding object just pass ...
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### Accelerations on the Moon due to its orbit and its spin

A gyroscope is placed on the equator of the Moon. It detects among others 2 accelerations: one due to the orbit and one due to the spin. What is the module of the second one compared to the first one? ...
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### How was the axial tilt of planets measured?

https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ? I guess it's "easy&...
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### How fast do the poles of Jupiter and Saturn precess?

As Jupiter and Saturn have very fast rotation periods, about 10 and 11 hours, respectively, I am assuming that their poles will precess much faster then Earth. Since Earth's poles precess every 26000 ...
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### Do some comets spin? If so, how fast?

The GIF below is copied from my question earlier What might a CN filter be in the context of comet watching? Is it showing dust, or gas, or something else? where I'd said: In this post on the website ...
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### Will there be any more planets come into our solar system and make it their "home"?

Could we have more planets come into our system and get trapped by our suns gravitational field and rotate?
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### Will Earth rotate backwards in the future?

Hello recently I heave heard the earth will eventually start rotating in the opposite direction (ie sunrise from the west) . I am not sure if this is true, but a lot of sites are claiming it to be ...
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### Calculating the Solar Day of an Exoplanet?

I am currently in the process of compiling a list of stars and their planets, given the information in the European Star Catalogue found here, but I'm struggling to find out how to calculate a planets ...
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### What is the YORP effect exactly? Is it just the non-central component of the Yarkovsky effect?

This answer to Where have all the Vulcanoids gone? links to the aptly-titled The YORP Effect Can Efficiently Destroy 100 Kilometer Planetesimals At The Inner Edge Of The Solar System which says in ...
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### Is a three body gravitating system doomed to collapse?

Suppose we have two gravitating bodies, which are rotating around each other. They are bodies and are affected by deformation caused by tidal forces. Moving tidal waves suck energy from the axial ...
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### Are there any bodies in the solar system whose rotation is almost tidally locked or barely tidally locked?

The Moon's rotation is firmly tidally locked to the Earth and the Earth's rotation is firmly tidally unlocked with respect to the Moon. I gather that Mercury's rotation is tidally locked in a 3:2 ...
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### Do the axes of rotation of most stars in the Milky Way align reasonably closely with the axis of galactic rotation?

The axis of rotation of the Solar System makes a large angle of about 60 degrees relative to the axis of rotation of the Milky Way. That seems unusual - for example, most of the bodies within the ...
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