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Questions tagged [natural-satellites]

Questions on celestial bodies that orbit planets.

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42 votes
1 answer
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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?
MB34's user avatar
  • 519
41 votes
3 answers
4k views

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 ...
SF.'s user avatar
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35 votes
3 answers
22k views

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 ...
user avatar
34 votes
1 answer
6k views

Why do Jupiter’s moons have so much water?

Why do Jupiter’s moons have so much water by mass? Did all the bodies in the solar system start out with this much water and the planets closer to the Sun simply lost it to space?
Elhammo's user avatar
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33 votes
1 answer
2k 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 ...
stackzebra's user avatar
  • 1,449
33 votes
2 answers
5k views

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 ...
Everyday Astronaut's user avatar
27 votes
3 answers
5k views

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 ...
usernumber's user avatar
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26 votes
6 answers
6k views

Definition of a moon in an exam: "A satellite of a planet that *doesn't produce light itself but reflects it*" - is there relevance for the emphasis?

In a 5th-grade exam (for 10-11-year-old pupils in Finland), there was a question, "What is a moon?" The model answer was: "A satellite of a planet that doesn't produce light itself but ...
tputkonen's user avatar
  • 369
25 votes
3 answers
3k views

Why is there a mountain inside the Herschel crater on Mimas?

If the Herschel crater was caused by an impact, why does it have a mountain at its very center, its peak up to 5 mi (8 km) in elevation?
John's user avatar
  • 1,538
24 votes
6 answers
7k views

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 ...
HDE 226868's user avatar
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21 votes
3 answers
2k views

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?
Eduardo Serra's user avatar
19 votes
3 answers
6k views

Is it possible to have satellites (natural or not) orbit the same celestial object in different directions ? (clockwise, counterclockwise)

Is it possible to have satellites (natural or not) orbit the same celestial object in different directions, or is the orbital direction dependent on the celestial object's spin? Also, is the direction ...
Demis's user avatar
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19 votes
1 answer
3k views

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 ...
Yannick Huber's user avatar
18 votes
6 answers
13k views

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: ...
Umang Chaudhari's user avatar
18 votes
2 answers
2k 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 ...
LocalFluff's user avatar
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18 votes
2 answers
771 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? ...
Zoltán Schmidt's user avatar
18 votes
4 answers
7k 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 ...
user avatar
17 votes
3 answers
4k views

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 ...
inquisitor's user avatar
16 votes
2 answers
3k views

At what distance from the Sun can planetary moons exist?

Mercury and Venus are theorized to have no moons because they are so close to the sun. Is there a theoretical distance in which moons tend to exist based on simulations?
William's user avatar
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15 votes
3 answers
3k views

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 ...
Allure's user avatar
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15 votes
1 answer
2k views

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 ...
Edward Loveall's user avatar
14 votes
2 answers
1k 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 ...
uhoh's user avatar
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14 votes
2 answers
1k 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?
Max0815's user avatar
  • 1,862
13 votes
1 answer
626 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 ...
chaonomy's user avatar
  • 1,119
12 votes
3 answers
5k views

If the Earth had another moon would it be better protected from asteroids?

Would the moons get struck by asteroids instead of the Earth or would the moons attract more asteroids and make it more likely the planet gets hit?
user avatar
12 votes
2 answers
1k views

What is the longest natural bound orbit chain observed?

Define a bound orbit chain as a list of successively less massive bodies, each in a bound orbit with the bodies preceding it in the list. Then an example of a bound orbit chain would be: <Sun, ...
Connor Garcia's user avatar
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11 votes
2 answers
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 ...
usernumber's user avatar
  • 17.5k
11 votes
1 answer
286 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 ...
komodosp's user avatar
  • 213
11 votes
2 answers
3k 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 ...
David Garner's user avatar
11 votes
1 answer
4k views

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 ...
Gstestso's user avatar
  • 2,209
11 votes
1 answer
167 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 + ...
Thibault's user avatar
  • 1,344
11 votes
1 answer
336 views

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 ...
LocalFluff's user avatar
  • 11.4k
10 votes
2 answers
2k views

Can individual rings of Saturn be considered satellites?

By this definition, is every small rock orbiting Saturn considered a natural satellites? What is the widely accepted terminology for moons? The Wikipedia article is ambiguous on this. So, what terms ...
EMS's user avatar
  • 103
10 votes
2 answers
670 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?
Anixx's user avatar
  • 1,265
10 votes
4 answers
2k views

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 ...
Allure's user avatar
  • 4,554
10 votes
1 answer
821 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 ...
user avatar
9 votes
3 answers
3k views

Why don't we find planetoids at L4/L5?

We find small objects (asteroids and dust) in the stable Lagrange points (L4 and L5), but AFAIK no moons (by which I mean a mass that accreted into a body, as opposed to debris that has been captured ...
feetwet's user avatar
  • 390
9 votes
1 answer
2k views

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 ...
Pablo's user avatar
  • 1,113
9 votes
2 answers
3k views

How would ocean tides work on a tidally-locked planet?

Since the tidal bulge is always in the same place, how would that affect ocean tides? Would they change throughout an elliptical orbit, due to changing distance from the star? How exactly would they ...
Elhammo's user avatar
  • 1,107
9 votes
2 answers
418 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?
user25024's user avatar
9 votes
2 answers
1k 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 ...
LocalFluff's user avatar
  • 11.4k
9 votes
2 answers
905 views

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 ...
Hojin Cho's user avatar
  • 191
9 votes
2 answers
790 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 ...
Nico's user avatar
  • 803
8 votes
3 answers
3k views

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 ...
sampathsris's user avatar
8 votes
2 answers
345 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?
Venethica's user avatar
8 votes
2 answers
3k views

The moon rises at a different time each day, but that difference changes. Why?

Let's say the moon rose at 5pm yesterday and 5:30pm today. The difference is 30 minutes – but that difference changes from day to day and can be anywhere between twenty-some to seventy-some minutes. ...
Treplef's user avatar
  • 81
8 votes
1 answer
443 views

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 ...
user avatar
8 votes
2 answers
804 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 ...
user1410910's user avatar
8 votes
1 answer
582 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 ...
Zoltán Schmidt's user avatar
8 votes
1 answer
570 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, ...
Bruce Becker's user avatar

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