Alien Anomalies

Software_Pyrate · Veteran Member

RE: Clumping ice in Saturn's F-ring due to Prometheus

fruitnut1 · Dedicated to the truth

OBrien wrote:

I wasn't able to get the animated GIF to work.

A nice high-res version is available at http://photojournal.jpl.nasa.gov/catalog/PIA07712

P.S. Anyone know the trick to getting an animated GIF to run embedded in the text?

It's no trick. The source site should be enabled for hotlinking animated gifs. Nasa's site is not.

-- Frutty

qmantoo · Teaching the truth

I would love to understand how/why the stars in the background move fairly quicky whereas the rings of Saturn are rock steady. I am assuming that Cassini is moving directly away from Saturn at this point.

I am not proposing anything strange about these stars or their movements but I genuinely dont understand how it works.

To me, there seems to be a lot of moving stars in the background and if they are far away, they would have to move very quickly to register moving such a distance across the picture screen. Sometimes I am like Pooh bear - a bear of little brain. I need things explained very simply to me before I can understand it all.

OBrien · Member

I wasn't able to get the animated GIF to work.

A nice high-res version is available at http://photojournal.jpl.nasa.gov/catalog/PIA07712

P.S. Anyone know the trick to getting an animated GIF to run embedded in the text?

qmantoo · Teaching the truth

Ok, thanks for your explanation. The way I interpreted/read the article seemed that it was an oddity, but obviously not.

OBrien · Member

First attempt at including an animated GIF. If it works you'll see:

Pandora and Prometheus on either side of the F ring.

Pandora on the outside, Prometheus on the inside. Prometheus pulls wisps of the F ring with it.

OBrien · Member

qmantoo wrote:
The article says that is whizzes around and causes disturbances in the F-ring because it is going faster than the other bodies at the same radius.

No it doesn't.

Objects at the same radius will move at the same speed, assuming no other forces. But Prometheus is not at the same radius as the F ring.

"Saturn's relatively thin F ring was discovered by NASA's Pioneer 11 spacecraft in 1979. Prometheus and Pandora, the small moons found on either flank of the F ring, were discovered a year later by NASA's Voyager 1 robotic space probe"

"Prometheus, which is larger and closer to Saturn, appears to be the main source of the disturbances in the F ring."

"This moon swerves around Saturn at a speed slightly greater than the speed of the much smaller particles in the planet's F ring. As a result of this discrepancy, and the slightly offset orientation of Prometheus' orbit, the moon laps the F ring particles, stirring them up approximately every 68 days."

Prometheus is inside the F ring. Pandora is outside the F ring. Nowhere does the article say that Prometheus and the F ring have the same radius. Orbiting objects with a smaller radius will travel faster, therefore it is expected that Prometheus with its smaller radius will travel faster than the F ring particles. Additionally, the eccentricity and offset of its orbit makes it approach and recede from the F ring every orbit.

No need to invoke speculation about Prometheus' non-natural origin or begin to doubt simple orbital mechanics. Just read the article carefully, and teach yourself a little about high school physics.

qmantoo · Teaching the truth

What IS Prometheus then ?

The article says that is whizzes around and causes disturbances in the F-ring because it is going faster than the other bodies at the same radius. If it is a natural body, it should not do this - or else our physics is wrong and we need another 'someones Law' to explain it.

fruitnut1 · Dedicated to the truth

qmantoo wrote:

so everything going around Saturn at the same radius SHOULD be moving at the same speed then? Is that what this is saying? (sorry to be so stupid)

Exacltly GM, and in general everything that gravitates in a (approx) CIRCULAR orbit around another, more massive object.

-- Frutty

Software_Pyrate · Veteran Member

Not everybody is a photo graphical, gravitational, mathematical, theoretical, expert like Fruit...

just kidden fruit.

qmantoo · Teaching the truth

so everything going around Saturn at the same radius SHOULD be moving at the same speed then? Is that what this is saying? (sorry to be so stupid)

fruitnut1 · Dedicated to the truth

qmantoo wrote:

But, my remembered physics says that larger bodies SHOULD go slower than smaller bodies at a given radiius... Yes??? No??? Anyone??

Apparently we were wrong:

Newton's Universal Law of Gravitation

By now you must be wondering: ``What is the Force that keeps the Saturn going around the Sun?'' Newton's great discovery was the force of {\sl gravity}, which is an attractive force that occurs between two masses. The Universal Law of Gravitation is usually stated as an equation:

F_gravity = G M₁ M₂ / r²

where F_gravity is the attractive gravitational force between two objects of mass M₁ and M₂ separated by a distance r. The constant G in the equation is called the Universal Constant of Gravitation. The value of G is:

G = 6.67 X 10^-11 meters³ kilograms^-1 seconds^-2

Newton's great step was developing this law and using it, with his laws of motion, to explain the motion of lots of different things --- from falling objects to planets. Amazingly, out of these simple and general rules, Newton was able to show that all of Kepler's descriptive laws for orbits followed as a direct consequence.

When you combine Newton's gravitation and circular acceleration, which must balance in order for the object to remain in orbit, you get a nice relation between the period, distance, and mass of the central body. It beings by equating the centripetal force (F_cent) due to the circular motion to the gravitational force (F_grav): F_grav = F_cent

F_grav = G m₁ m₂ / r²
F_cent = m₂ V² /r

Let the Saturn be m₁ and the moonlet be m₂. For circular motion the distance r is the semi-major axis a. The orbital velocity of the moonlet can be described as distance/time, or circumference of the circular orbit divided by the orbital period:

V = 2 pi r /P

so setting the forces equal yields

G m₁ m₂ / a² = m₂ V² /a

note that the m₂ will cancel, so that circular orbital motion is independent of the mass of the orbiting body!

Source

Software_Pyrate · Veteran Member

O sorry...I missed the part about a given radius....will get back

Software_Pyrate · Veteran Member

Q....that is not necessarily true.....

its just how much energy or velocity is in the mass. Look at Jupiter, the biggest planet, orbits faster than all the other planets beyond its orbit.

fruitnut1 · Dedicated to the truth

Of course it should ... but in outer space our physics are useless lol biggrin

qmantoo · Teaching the truth

But, my remembered physics says that larger bodies SHOULD go slower than smaller bodies at a given radiius... Yes??? No??? Anyone??

Software_Pyrate · Veteran Member

Yep...thats what I'm gettin from it....

qmantoo · Teaching the truth

I am not very well informed about the motion of moons and planets and rings and bits of ice etc, however the article interested me as it said that the 'thing' called Prometheus moved much faster than the particles in the F-ring and in fact it lapped them (meaning that it was moving so fast that it overtook the original same place it started from before the other particles had completed one circuit)

The asteroid/moon Prometheus which orbits at the same place as the F-ring is causing a disturbance when it 'laps' the other particles and since it is a potato-shaped thing, it disturbs the F-ring causing some clumping of particles into ice (snowballs).

That is what I understand from reading the article mentioned above.

Software_Pyrate · Veteran Member

Ah...so what u r wondering is why Prometheus is orbiting faster than the rings.? Is that right Q?

The origin of it would be the tall tell sign....

would I be right to say that Prometheus is the result of of this snowballing effect?....or is it from some where else.....Anybody...?

Software_Pyrate · Veteran Member

What do you mean by this fruit....

"You might suspect I've already saw through several images of saturn with our enhancing technique. The fan-like structures were already visible, and this one goes to SP -> there is a clump faces dancing around Saturn cry

"

could you reiterate?

fruitnut1 · Dedicated to the truth

Software_Pyrate wrote:

First , interesting thread...as I was unaware of the disturbense in the f-ring.

But I don't quite understand what your asking Q?

_________________________________________________________________

Alright Fruit...I'll bight. What you got on the rings...?

I think he is referring to S/2004 S 6

S/2004 S 6 is the provisional designation of a dusty object seen orbiting Saturn very close to the F ring. It is not clear whether it is only a transient clump of dust, or if there is a solid moonlet at its core.

Software_Pyrate · Veteran Member

First , interesting thread...as I was unaware of the disturbense in the f-ring.

But I don't quite understand what your asking Q?

_________________________________________________________________

Alright Fruit...I'll bight. What you got on the rings...?

Software_Pyrate · Veteran Member

So ...what you are sayin is the "snowballs" should be moving slower...is that right?

fruitnut1 · Dedicated to the truth

qmantoo wrote:

Saturn's Prometheus shoots around the F-ring at a faster rate than the smaller particles in the F-ring. According to this article on space.com, This apparently causes disturbances in the F-ring which makes clumps of ice stick together into snowballs.

From what I remember of my physics lessons many moons ago, I thought that a larger body should go slower at the same radius from a centre point? I might have remembered it wrong?

You might suspect I've already saw through several images of saturn with our enhancing technique. The fan-like structures were already visible, and this one goes to SP -> there is a clump faces dancing around Saturn cry

-- Frutty

qmantoo · Teaching the truth

Saturn's Prometheus shoots around the F-ring at a faster rate than the smaller particles in the F-ring. According to this article on space.com, This apparently causes disturbances in the F-ring which makes clumps of ice stick together into snowballs.

From what I remember of my physics lessons many moons ago, I thought that a larger body should go slower at the same radius from a centre point? I might have remembered it wrong?