Questions tagged [natural-satellites]

Questions on celestial bodies that orbit planets.

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Slow moving, flashing star-like object in the sky. What could it be?

The sky was particularly clear last night and I noticed an extremely bright star. I thought it was venus possibly but it was too low down and was flickering craziy. That meant that it couldn't be a ...
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Could an orphan/rogue planet have a moon?

Is there some reason why an orphan or rogue planet wouldn't have a moon? Let's say it started out in a normal system and then just got flung out by an unstable orbit.
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Do moons experience periods of no sunlight when orbiting “behind” their planet?

I'm writing a story that takes place on the Saturn moon Iapetusand I was thinking that especially since Iapetus only has an inclination of about 17 degrees from the ecliptic, wouldn't there be a point ...
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Can we see traces of exo-moon formation?

Our Moon was likely formed by the collision of a Mars-size object with the Earth soon after the planets first formed. Would traces of such an event be detectable by observing the protoplanetary disc ...
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How many Kuiper Belt objects have moons? How do we know this?

On 2012 in the New Horizons' The PI's Perspective Alan Stern wrote The Kuiper Belt at 20: Paradigm Changes in Our Knowledge of the Solar System (more also archived) which includes: Most of the known ...
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Are there any moons of minor planets that orbit at high inclination to the plane of rotation of the parent body?

It occurred to me that one of the ringed asteroids or minor planets may answer this question about the alignment of planetary rings. However, it appears that the rings of Chariklo, Haumea and Chiron (...
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Has any moon achieved “retrograde equatorial orbit”?

There are many moons which have low (almost negligible) inclination and can be considered to rotate at the planet's equatorial plane. For instance, Galilean moons have almost negligible inclination (&...
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Moons with curlicue paths around our Sun?

I naively believed that since our Moon orbits Earth, and since Earth orbits the Sun, the path our Moon might take around the Sun would be this type of epitrochoid curve: I was surprised and delighted ...
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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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What is the naming convention for temporary moons?

Is there a naming convention for temporary moons? Or do they follow the naming conventions of other small bodies? In the case of 2006 RH$_{120}$, 2015 HP$_{116}$, 2020 CD$_3$ and 2020 SO, the first ...
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1answer
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What celestial body (inside the solar system) has the highest flattening ratio?

As a planet, Saturn has the highest flattening(ellipticity) which is 0.09796. So, it makes Saturn with the largest equatorial bulge as a planet and as such Saturn is the flattest planet. However, I ...
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Why are the moons of Neptune sorted by diameter?

The five moons closest to Neptune are sorted by increasing size. Naiad < Thalassa < Despina < Galatea < Larissa. The trend continues with Proteus and Triton, only interrupted by Hippocamp, ...
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Why does an irregular moon point its longest axis towards its parent planet?

I'm reading the book Ice Worlds of the Solar System. Page 62, it states that an irregular moon should point its longest axis towards its planet. Why is this the more stable configuration?
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What caused these strange craters on Hyperion?

I was looking at pictures of the moons of Saturn and noticed that the craters on Hyperion have a strange shape, somewhat resembling sinkholes. They look a lot deeper than the impact craters on other ...
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How to calculate the frequency of a gas giant eclipsing the sun from a moon?

Say you have a moon around a gas giant which goes around a star. If the moon has an inclination of around 0° relative to the gas giant's orbit, the gas giant will eclipse the star every orbit of the ...
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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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Does tidal locking also slowly reduce the orbiting body's axial angle?

The Moon is tidally locked to the Earth, and it has an axial angle of 6.687 degrees relative to its orbital plane. I'd like to know: did the Moon start out with a higher axial angle? In other words, ...
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Do celestial objects need to be big to have liquid water on their surfaces?

I mean no asteroid, planetoid that I am aware of has water on its surface. It is way more common to see ice in it. So I figured that the size of the celestial body has something to do with the cycle ...
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Is there a name for a planet and its moons/satellites?

I'm wondering if there's a name that encapsulates the concept of a planet and the objects that orbit in its gravity. There's a solar system that encapsulates a star and its multiple planets and other ...
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111 views

Is a literal instance of Russell's teapot possible?

Much has been said about Russell's teapot, and I accept as obvious that a teapot would be too small to be detectable in an orbit around the Sun by any reasonable method today, or by any method that ...
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How to find the mass of a planet not knowing the gravitational constant?

So I found this problem, I know the gravity of earth $g_0$, I found the orbital speed of one satellite using this equation $\frac{GM_em_s}{(R_e+h)^2}=m_sa$ ($M_e$ is the mass of earth, $m_s$ is the ...
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How did the orbits of Phobos and Deimos circularize?

The satellites of Mars might be captured asteroids. But Phobos has an eccentricity of $0.015$, and Deimos of $3\times10^{-4}$. If they were captured, they likely were captured with rather eccentric ...
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Angular diameter result confirmation

Not being a math-minded person at all, however basic it might appear to be to all of you in this particular question, I would like to get the following calculation confirmed. I'm trying to calculate ...
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Why don't the inner moons of Jupiter have tidally-induced volcanism?

Volcanism on Io is caused by the fact that it is tidally heated. There are four moons that are closer to Jupiter than Io with higher eccentricities, yet they don't seem to have any volcanism at their ...
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Which moons do have neutrospheres?

Or in other words: which moons do have ionospheres but not surface-bound ones? The space beneath an ionosphere is called a neutrosphere. I only know of Titan. I know that the Galilean moons and Triton ...
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How many satellites orbit their planet faster than the planet rotates?

Phobos is so close to Mars that it orbits Mars much faster than Mars rotates. This means that it rises in the west and sets in the east, even though its orbit is prograde. Are there any other known ...
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How many moons do we know are shepherds?

Shepherd moons are natural satellites near the edge of a planetary ring that have an influence on the shape and size of the ring due to their gravity. So it is possible for a satellite to be near the ...
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358 views

What is the minimum mass of a celestial object so that it can have a moon?

I was wondering how massive something have to be so that it it can attract moons by pop culture standards (ellipsoid/round shape). Could a planetoid have a moon? What is the relation between the mass ...
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If a planet gained too many moons could the tidal forces of those moons rip the planet apart?

Or would the planet just be subject to extremely intense tidal forces instead?
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Keplerian Elements for the Moon and Earth around their Barycenter

So I'm looking to replicate the inner Solar System to a decent degree of accuracy. So far I've been utilizing the Keplerian Elements and Equations for the planets, as shown here. There is one issue ...
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Why was the diaeresis removed from Pasiphae?

The Gazetteer of Planetary Nomenclature notes that the spelling of Jupiter's moon Pasiphae was changed from Pasiphaë in July 2009, i.e. they removed the diaeresis. I've been unable to track down the ...
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Why doesn't the moon always follow the same path? Or why aren't the moon's apoapsis and periapsis fixed?

I have seen many times that the moon doesn't follow the same path. Sometimes the moon gets very close to earth which is shown in the news. If the periapsis of the moon is soo close then why doesn't a ...
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Why isn't there a large gap in the number of captured moons Jupiter and Saturn have?

Given that Jupiter is roughly 3x as massive compared to Saturn and is located right next to the asteroid belt, it feels that Jupiter should easily have a larger amount of captured moons. However ...
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Ladakh India where the moon (Ramadan moon) is sighted but not in rest of India [duplicate]

Today 22 May 2020 around 3 p.m Ladakh India sighted new moon(Ramadan moon) but not in rest of India.I read many articles acc. To them it is not visible today, then how it was seen from Ladakh... .
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What would happen to the Galilean moons and Titan if Jupiter and Saturn disappeared?

The Moon reportedly doesn't "need" the Earth to revolve around the Sun. If the Earth wasn't there, the Moon would continue its current path from a heliocentric reference frame around the Sun. My ...
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Is a Procyon - brown dwarf - Jupiter - superearth - Mars - Pluto system theoretically possible? [closed]

I once conducted a thought experiment and with some amateurish calculations based around Hill sphere and Roche limit came up with semi-major axis distances like this: ...
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Would magnetic reversals on Ganymede affect radiation levels at the surface?

Currently the intrinsic magnetic field of Ganymede is anti-aligned with respect to the Jovian magnetic field. If this situation changed to become aligned, either due to magnetic reversals of the ...
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Help identifying a very slow-moving object during meteor shower photography

I just wonder if anyone could shed any light on this puzzle. Two nights ago whilst I was out photographing the Lyrids meteor shower from the UK something else showed up on my images when I checked ...
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1answer
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Brightness, altitude & azimuth for satellites?

I'm using the heavens-above website to identify a satellite I've seen several nights this week. The question is related to how I can search the satellites table with the information I can provide. ...
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Is the process responsible for Triton's nearly perfect circular orbit going to happen in my fictional world?

First of all, I'd like to point out that I'm a worldbuilder and I like my worlds to be as physically possible as... possible. I am in the process of building a world with a habitable moon orbiting ...
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New temporary moon of earth [duplicate]

A new temporary moon named 2020 cd3 has been discovered. How can we determine that this is temporary and why does it have such an orbit which is such irregular in shape ?
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What is the precise definition of a moon? [duplicate]

With the recent discovery of Saturn's 20 new moons (elevating its position on the rank of planets with the greatest amount of moons, surpassing Jupiter), it makes me wonder: what are the requirements ...
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Up to 384 minor planets (including Pluto) qualify as planets?

In 2006, the International Astronomical Union redefined the definition of planet in order to exclude Pluto, Eris, and several other objects whose category was disputed. This new definition of a planet ...
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What's the first written record of the moon being tidally locked to the earth?

I couldn't find references as to who first noticed (wrote down) that the moon was tidally locked to the Earth. This, to me, doesn't seem obvious from first glance, and looks like something only found ...
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Is Earth's moon the only one where a total eclipse of the sun covers the entire sun?

Is Earth's moon the only one where a total eclipse of the sun covers the entire sun? Are any other moons the same size as the sun as viewed from their planet like Earth's moon?
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Should only spherical satellites be considered 'moons'? [closed]

Since Titan and Ganymede fall into the same category as Deimos and Phobos or the components of planetary rings, the category of moons, it's like if all asteroids were considered planets. Tiny ...
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1answer
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Can there be a three-moon system where only two are visible most of the time?

I am trying to build a moon system for a sci-fi work in collaboration with my boyfriend. He's the main writer and wants there to be three moons circling the planet in a way that most of the time, only ...
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1answer
109 views

Why is Io's volcanism chemically so different from Earth's?

Volcanic gases on Earth are mainly water, carbon dioxide and sulfur dioxide, but on Io there is a notable absence of water and carbon dioxide in volcanic gases, since sulfur dioxide is the dominant ...
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1answer
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How long do solar eclipses last on Metis?

How long does Jupiter obscure the sun, from the perspective of Metis, the innermost moon of Jupiter? In other words, how long does Metis remain in the shadow of Jupiter? If it varies by time of year,...
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Would it be possible for life found on moon of rogue planet

I have heard that there are at least three Basic requirement for life exist in the universe, they are: Source of Energy Complex chemistry (including solvent/medium for chemical reaction) Protection ...