Questions tagged [natural-satellites]

Questions on celestial bodies that orbit planets.

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39
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1answer
8k views

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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3answers
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Do moons have moons?

Have we discovered any natural satellites of natural satellites of planets or dwarf planets? Even very small, or relatively short-lived - e.g. ringlets around Saturn's moons, some meteorites orbiting ...
33
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2answers
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Why does Jupiter have so many moons?

Jupiter has a great many moons - in the hundreds, and they're still being discovered. What is the current theory for where all these moons came from? Are they rocks flying through space captured by ...
31
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2answers
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Is there any known moon of a moon? [duplicate]

As far as I understand, a moon is an object in permanent orbit around a planet, dwarf-planet, asteroid, etc. If there was another object permanently orbiting this moon, would that be a moon-moon? Is ...
27
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3answers
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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 ...
23
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6answers
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Can a natural satellite exist in a geostationary orbit?

While browsing through Physics SE, I noticed a question about satellites in geostationary orbit (unrelated to the one I'm asking here), and for a moment I interpreted it as referring to natural ...
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3answers
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Will Saturn's rings become a moon?

Planets form from disks of matter orbiting around a star; some moons form from disks of matter orbiting planets. If this were going to happen around Saturn, approximately how much time would it take?
19
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1answer
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Did we discover 10 or 12 new moons of Jupiter?

I saw multiple news sites reporting that a team discovered 12 new Jupiter's moons: c|net - Twelve new Jupiter moons found, including one reckless one Discover - Jupiter’s Got Twelve New Moons — One ...
18
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2answers
550 views

Moon orbits crossing each other

Some planets, such as Mars, have 2 or more moons. Giants, like Jupiter of Saturn have a lot of moons! How likely the orbit of one crosses another one's orbit? Is it possible for two moons to collide? ...
18
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4answers
6k views

Jupiter FM - What are practical and inexpensive ways for the amateur detection of signals from Jupiter, especially of the transit of her moons?

What modifications to a standard AM/FM or shortwave radio are needed in order to be able to detect radio-wave signals emitted from Jupiter? Would it be possible to detect the transit of the major ...
17
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2answers
1k views

Why haven't Earth and Venus got any tiny moons? Or have they?

Why haven't some meteoroids gotten caught in Earth's or Venus' orbit? AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities ...
15
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3answers
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Would an analogue of the definition for planets also work for moons?

This is a follow up question to What exactly is a "moon"? The conclusions I draw from James K's answer is that the IAU should define what a moon is. They haven't done so yet, but they should. The ...
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2answers
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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 ...
14
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8answers
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Moon's orbit around the Sun

The Earth revolves around the Sun and the Moon revolves around the Earth. Out of curiosity I started thinking about the orbit of the Moon around the Sun and expected (assumed) it to be as follows: ...
14
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1answer
395 views

Is it possible for a moon to orbit a planet floating free in the galaxy rather than orbiting a star

This article got me thinking, can a planet hold a moon in orbit if it is just floating in the galaxy by itself not as part of a star system? Can a celestial body even qualify as a planet if it is ...
13
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2answers
661 views

How can tidal heating lower Io's orbit?

This answer to the question Is Io a magic energy machine? suggests that the energy from the internal heating of Io due to tidal "squishing" as it moves cyclically closer and farther from Jupiter in ...
12
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1answer
123 views

Is there a pattern between the mass of a body and the mass of orbiting objects around it?

I was looking at Wikipedia's Solar system page, and it says that Sun represents 99.86% of the whole solar system mass. I found that pretty huge. So i calculated ratio of masses : Earth / (Earth + ...
12
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1answer
379 views

Why do planets and satellites in the Solar system look so wildly different if they came from more or less the same matter?

First, the planets. We have Mercury, which is rocky, no atmosphere. But then we have Venus, which is completely different: thick atmosphere, very hot, geologically active. Then Earth - blue, full of ...
11
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2answers
2k views

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 ...
11
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1answer
246 views

Are all satellites thought to be the result of collisions with the planets?

The leading hypothesis for how the Moon was formed was that another object collided with the Earth, throwing off a large lump of matter which formed into the moon. Is this thought to be the case with ...
11
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2answers
2k views

How do moons get captured?

A moon-sized object is running loose in the Solar System, perhaps after a planetary collision. As it approaches a planet, it's presumably following an approximately hyperbolic path. If it goes on ...
10
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2answers
617 views

Why does the Solar System have no (natural) satellites of satellites?

What are the conditions for a planetary moon to have a satellite of its own? How far do the Solar System's bodies fall from the necessary threshold?
10
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1answer
678 views

Why is Enceladus the only geologically active moon among its neighbours?

My understanding of why Enceladus is geologically active is that tidal forces from Saturn and - to a lesser extent - from the nearby larger moon Dione provide heat to the moon's interior, just like ...
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1answer
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Is it possible that Mercury was originally the moon of Venus after a giant impact?

Mercury looks like the Moon, and so it makes me think about a question: is it possible that Venus and Mercury were the a same planet originally, and a giant impact with that planet made it split into ...
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1answer
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Why haven't more captured small moons been found?

Shouldn't captured moons have the same size distribution as asteroids? And asteroids are more common the smaller size they are. Moons are likely captured if they are in highly inclined orbits, and ...
9
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1answer
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Which Saturn satellite passes closest to Saturn's rings and at what distance?

I was using Stellarium to watch Saturn from its moon Pan and I saw the rings were very close to this moon. Now Saturn's rings extend for a large distance so several moons see them from close. I was ...
9
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2answers
296 views

Natural satellites for Mercury

Would it be possible that Mercury had a natural satellite but the gravitational pull from the Sun became so overwhelming from it growing over the years that it just sucked in Mercury's moon?
9
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2answers
549 views

Why does Saturn have both moons and rings?

From my understanding, a ring can form around a planet when a moon gets too close to its Roche limit, and gets ripped appart by the planet's gravity pull. That makes sense to me, but I don't ...
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Can you explain the pattern of Hill sphere sizes of the objects of the Solar system?

I found this image on calculations of Hill sphere for planets/dwarf planets of the Solar system. From http://en.wikipedia.org/wiki/File:Hill_sphere_of_the_planets.png I found it interesting that ...
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2answers
307 views

Is it possible for a moon to continuously have a side facing its star whilst orbiting a planet?

For example; is there any possibility for the moon to always have a side facing the Sun whilst orbiting Earth? And if so then what would the day cycle be like?
8
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1answer
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When was it realised that most major moons orbit in the equatorial plane of their parent planets?

Inspired by the discussion of the moons of Uranus providing a clue to the planet's axis of rotation in this question, I'm wondering when it was realised that the major satellites are typically located ...
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4answers
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What exactly is a “moon”?

Recently some new moons of Jupiter were discovered. However the moons are pretty damn small indeed - only a few kilometers wide. That makes me wonder if they should even be called moons in the first ...
8
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1answer
476 views

Effect of Charon on Pluto

Even though Pluto is not known as a planet anymore, theroetically it has/had a moon, called Charon. I've heard about something that their size are so close to each other that while Charon rotates ...
8
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2answers
377 views

Eventual outcome of tidal acceleration and deceleration

So, I know the Moon experiences tidal acceleration from the Earth. And, from what I've read, if not for the fact that the sun would boil away the oceans and engulf both of them first, about 50 billion ...
8
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2answers
702 views

Why do Uranus' and Pluto's moons orbit the equator? What makes a moons' inclination tilt with the rotational axis of their planet?

Uranus and Pluto have their axes of rotation almost 90 degrees towards the ecliptic. But why do their moons tilt the same way? Does it mean that their tilts were caused by passing near some external ...
8
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1answer
313 views

Which celestial object in the solar system has the fastest tangential velocity at its surface?

Consider all of the naturally-occurring objects in the solar system : in the reference frame of the object's center (ie, ignoring the orbital velocity around the sun or, in the case of satellites, ...
8
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2answers
297 views

How long is a “lunar month” in Jupiter?

For Earth, the lunar month is well known. But Earth has only one moon. But on Jupiter, how long does it takes for the same moon configuration to appear in the "sky" of the planet? For the sake of ...
8
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1answer
297 views

Why is Uranus able to support a regular satellite system?

Uranus has an obliquity of 98° which means that the mutual inclination between a satellite orbiting in its equatorial plane and the orbit of Uranus around the Sun would exceed the critical angle for ...
8
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1answer
201 views

Why does Titan have an atmosphere while similar moons such as the Galilean moons don't?

The Galilean moons of Jupiter are similar in size to Titan and are also protected by their parent planet's magnetic field. How come only Titan is able to maintain an atmosphere?
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Official Definition of Satellite?

So I had an argument with a friend, which was about whether the Moon is a planet or a satellite. IAU 2006 Resolution B5 gives definitions on what it is to be a planet, but there is a vagueness, as I ...
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520 views

Can a gas giant have an other gas planet as satellite?

Is it possible for a gas giant (A very big one) to have an other smaller gas planet as satellite?
7
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1answer
385 views

Wouldn't the rings of Saturn experience tidal effect?

The "Lord of the Rings" has more than 60 moons, some of which are larger than Mercury. My question is, wouldn't the ring, which is mostly comprised of rocks, experience tidal effect whenever a moon is ...
6
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2answers
173 views

Is there a timekeeping word for the orbit of a moon?

For a planet, we can colloquially refer to its period of rotation as a "day" and its period of revolution around its parent star as a "year." Some worlds have unique terms, such as Martian days being ...
6
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2answers
153 views

horseshoe orbits

I'm designing a moon system for a fictional setting, and recently came across the idea of horseshoe orbits. The gist of my question is how many objects can share a horseshoe orbital at a time? I ...
6
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1answer
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Can a gas moon exist? [duplicate]

Could a gaseous moon exist in the same way as a giant gas planet? All the moons in the solar system are rocky, or icy. Why shouldn't gas planets have gas moons?
6
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1answer
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Could a cryo-volcano be the reason behind this colour difference in Iapetus's hemispheres?

Iapetus's hemisphere facing Saturn is dark, whereas the opposite one is bright. Could a cryo-volcano be the reason behind this colour difference in Iapetus's hemispheres?
6
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1answer
335 views

Theoretical limits for natural satellites having natural satellites

Is there an inherent instability or limit that prevents natural satellites like the moons of Jupiter from having their own natural satellites? I looked at other questions such as do moons have moons ...
5
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3answers
968 views

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 ...
5
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3answers
1k views

Are moons geologically active?

Are there natural satellites in the Solar System that are geologically active? This includes volcanism, existence and motion of tectonic plates, et cetera. Is it a common or a rather rare feature ...
5
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2answers
207 views

What variables are needed to calculate simple horseshoe orbit times?

EDIT This was NOT a duplicate of Horseshoe orbit cycle times. But that other question has been deleted, regardless. My original question asked for the answer to the equation(s), and provides many of ...