# Tag Info

47

Yes, the plane of the rings of Uranus are at about 98 degrees to the plane of its orbit around the Sun. This means that the ring system looks as in your picture twice per orbit. As the planet orbits the Sun, the rings, although still inclined at 98 degrees to the orbital plane gradually become "face-on" when viewed from the Sun. This will happen ...

29

I posted a few animations, just to make sure :) The image is hopefully obviously not to scale. This is possible: and is, in fact, not far from what Uranus is doing. The animation above was produced using Mathematica. The camera is above the plane of the planet's orbit, but not directly above the star. The rings are perpendicular to the plane of the orbit. ...

24

The answer to the headline question is: No. Most of Saturn's rings are below the Roche limit of about 2.5 Saturn radii. Hence tidal forces will prevent that part of the rings to form a (large) moon. Actually, part of the rings may be caused by loss of material from some of Saturn's moons, as suspected from observations of Enceladus. Accretion of Earth is ...

23

Pan, Daphnis, and various other moonlets, I would argue, are inside the rings. If you explicitly discount the Encke gap (which Pan orbits in) and the Keeler gap (which Daphnis orbits in) as being part of the ring system, Daphnis would be your answer, as it is a ~8 km object in a 42 km gap. (for comparison, Pan is a ~35 km object in a 325 km gap) Really, ...

21

A moon is held together by its own gravity, and pulled apart by the tidal action of a planet. If a moon comes too close to a planet it will be ripped apart by the planet's gravity and become a ring. The closest a moon can come to a planet is known as the Roche limit, and it is dependent on the mass and density of the planet and moon. A large planet, such as ...

14

First of all, at that distance seeing the Moon and seeing the Earth amounts to the same thing. At its closest, Saturn is around 3000 times as far from Earth as the Moon is, so viewed from Saturn, the Moon is never more than about a minute of arc away from the Earth. If you can see Earth from the North Pole of Saturn, you can see the Moon, also. (Though it ...

13

In a sense, that is what a circumstellar disk is. Source: European Southern Observatory (ESO) These are usually most noticeable around young stars as protoplanetary disks, disks that form planets. In the picture above, the gaps in the "rings" likely represent forming planets, similar to how the gaps in Saturn's rings indicate the presence of moons. Our ...

13

From wikipedia, the rings of uranus The definitive discovery of the Uranian Rings [...] use[d] the occultation of the star SAO 158687[...] The star SAO 158687, also cataloged as HD 128598 is a magnitude 8.7, orange dwarf star in Libra. There seems to be nothing special about the star, except that one day, a planet passed in front of it.

12

Yes, if you observe Earth and the Moon at a favorable time. Near a Saturn summer solstice, e.g. between 2012 and 2022, Earth appears well above the horizon from Saturn's north pole. If the planet body is out of the way, so are the rings. The other observability issue is Earth's elongation from the Sun. This reaches a maximum of about 6$^\circ$ at intervals ...

11

They certainly can. A ring is often formed around a celestial body when its gravity rips apart another smaller celestial body. The Sun is really massive, so it could destroy any object that is not dense enough. Just Google about the Roche Limit for more informations (and better explanations). Now, take a look at our solar system : You have the asteroid ...

11

The currently leading answer is correct to say that moon formation inside the Roche limit is unlikely. However, the disk is evolving due to viscosity between the particles, and as a consequence it "spreads", so that material is able to move to outside the Roche limit. In fact this is a leading possible explanation for the formation of the inner moons of ...

11

This doesn't seem to occur in our solar system. The most volcanic body, Io, does create a trail of gas around its orbit of Jupiter, but has no ringlike structure of its own. As uhoh notes, orbital dynamics means that if an object is projected from the surface of a planet or moon it will either exceed escape velocity (in which case it goes out into space) or ...

10

It appears (and I am no expert) that Saturn's ring evolution is governed mainly by "viscous spreading" - collisions between ring particles; and also by interactions with Saturn's moons (resonances); and bombardment with meteoritic material. There appears to be no consensus on how old the ring system is. Most theories of their formation have this taking ...

10

While such a scenario would be unlikely, all you'd need is an existing ring and an icy moon to enter inside the Roche limit at a measurably different inclination. I wouldn't want to guess how long a set-up like that would be stable, but it's possible to have one.

9

The vast majority of the particles in Saturn's rings are small, on the order of $\sim10^{-1}$ m or lower. The columnar number density, according to data from Voyager 1 and Earth-based observations, can be approximated as a function of particle radius by a power law for all particle radii $a$ in meters such that $0<a<1$, as can be seen on this log-log ...

9

By "visible to the naked eye", I take it you mean "visible from Earth with a small telescope". Saturn's rings are largely water ice, and so they reflect more sunlight back to us. Jupiter's rings, have lower proportions of ice, and lots of smaller dust particles that tend to scatter light forward rather than back to us. The ring systems of Uranus and ...

9

For these kind of questions, you might want to use Stellarium, a free open source planetarium. You can specify the location of the observer on many celestial bodies, including Saturn. Any time between 2011 and 2023 With this tool, you can see that the moon will be in the northern saturnian sky non-stop between 2011 and 2023. You can also see that the moon ...

7

Short answer: no. Long answer: There are many collisions within ring systems, and collisions always work, over time, to push orbits to a circular shape (or destroy the rings). Any deviations tend to be quickly corrected. For the same reason, rings tend to be extremely flat and extremely thin. E.g. Saturn's rings are only dozens of meters thick; given ...

7

Nearly always. The asymmetric gravity of a spinning (and hence oblate) planet will induce tides that can pull small moons and ring particles into orbit around its equator in a few million years. If you had a moon that was for some reason not orbiting around the equator, and it broke up (for example by passing the Roche limit) then the resulting ring would ...

7

Most planets don't have rings. The ring region is inside the Roche limit which is quite close to the planet. A ring system outside the Roche limit needs to be either very faint or, it would over time coalesce into a moon or possibly pair of moons at Trojan points to each other. There's different Roche limits for rocky bodies vs icy, but an icy body ...

7

The simple answer is yes, an asteroid can have rings. The current known example is 10199 Chariklo, whose rings were discovered in 2014 (see Braga-Ribas et al. (2014)). It actually has two rings, at distances of 391 km and 405 km, 7 km and 3km in width. As the discovery paper notes, they may be the (young) remnants of a debris disk around Chariklo, and have ...

6

The answer is a bit more complex than what userLTK presents. Tides play a huge role for the orientation of the rings. If the ring system has an inclination relative towards the planet, then inclination damping will occur. This means that the planet, that is flattened due to its own rotation, will exert asymmetric force tugs onto orbiting masses, until the ...

6

First, Azimov was writing (Edge 1982, and Earth 1986) before the first extra solar planets were tentatively detected (1989), or definitely detected 1991 or 1992. So what he wrote could not be based on any real data on extra solar planets, and must have been an educated guess. However both books were written after the discovery of Charon, so he may have been ...

6

The denser rings are actually very comparable in mass density to that of air. Because of their larger particle/particulate sizes, the number density is much much smaller. e.g. Ring A: Radius ~ 137,000km, thickness ~ 10m, surface density ~ 20 g/cm^2 so a density of about 0.02 g/cm^3, which is about 10 times more than air, and 100 times less than water. ...

6

First, there are different types of rings. Using saturn as an example: there are icy particles, dust bands and more. These interact differently if they were to hit a moon, for example enceladus. Every little particle in a ring is a „mini-moon“ and obeys the same laws (see kepler) as the big ones. They technically all have their own orbit. The main rings ...

6

Here is an answer based on photometric arguments: The astronaut probably would not be able to see the rings, but it would be worth a try. I would recommend the astronaut float somewhere at a distance of ~1.5 $R_J$ from Jupiter's center, where $R_J$ is the planetary radius of 74,000 km (at back of envelope precision). That way, they can look in a direction ...

5

You're right that density is the important thing here. The Roche limit is the distance from the main body $d$ such that $$d=1.26R_M\left(\frac{\rho_M}{\rho_m}\right)^{\frac{1}{3}}$$ where $_M$ denotes the main body and $_m$ denotes the satellite. As you can see from the chart on the Wikipedia page, Pandora and Prometheus are both at least one and a half ...

5

The rings are about 3% solid in the densest parts, but this translates to a separation between 30cm particles of about 1metre. There are no images Because approaching the dense part of the rings would be extremely difficult. A probe would be travelling at orbital speeds, and even a small percentage difference in speed would translate to a large absolute ...

5

Bryan (2007) gives a number of reasons why O'Meara's discovery was largely discounted: As you stated, the behavior was entirely inconsistent with Keplerian predictions of motion. While O'Meara was able to reproduce his findings, no other independent observers could. The detections were done entirely visually, rather than with numerical measurements. There ...

4

As addition: What Conrad said about ring systems is true, we have a possible first detection, but nowhere near detections to make any claim about such phenomena being normal. Also our knowledge on that won't change much in the coming years. With the upcoming photometric missions on transits like NASA's TESS or ESA's PLATO we'll probably be only able to ...

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