Moons and mini-moons

[vogon13]

Solar perturbations (and earth's too) caused the Apollo Fields and Particles sub-satellites (Apollos 15 and 16) to contact the lunar surface within less than a year. Although the orbits were deemed good enough for a manned (!) spacecraft, the long term instability of circular orbits about the moon was not appreciated at the time.<br /><br />The effect (as I understand it) is that the intensity of earth's (and the sun's) gravitational field weakens across the diameter of the orbit. Even though superimposed on the relatively far stronger lunar gravitational field, the effect 'tweaks' the orbit every pass and pumps up the eccentricity. This effect cannot continue for long till the object contacts the surface.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[alokmohan]

Dear SEARCH I was thlnking of moon in perspective of history of science.None is thinking that observation of moon by ancients raised questions about what role the moon played to open up astrology and astronomy,same thing in those eras..If there was no moon ancients would see all nights dark and they would have never bothered about movement of celestial objects.

 

[search]

Although now Pluto is no longer a planet we can consider its case.<br /><br />Pluto has three known satellites, Nix, Hydra, and a large companion called Charon. Charon is also unusual in that it does not orbit Pluto, but rather both bodies orbit a barycenter in empty space, making Pluto-Charon a binary system.<br /><br />Its not a moon of a moon but surely a 3 (4) body system. In this case the barycenter is ouside the surface of the Pluto. <br /><br />I believe it is possible that at a certain stage of the solar system life the barycenter of a Planet and the main moon of a 3 or more body system may have been below the surface of he planet, in which case it would quailify (by definition) the main moon as moon and the barycenter of the "moonlet" or "mini-moon" (I am using these words just to continue the thread idea) may at a certain stage have been below the surface of the main moon. However that moonlet would not quailify by definition as moon. I am sure some other name would be found and another definition would come up after lengthy discussion.<br /><br />In the end it all as to do with definitions and barycenters. There are plenty of 3 or more body systems in our solar system.

 

[search]

It was good that you point that out because it brought more interest into the discussion.

 

[alokmohan]

Moonlet is the term.Why not call them moom?

 

[search]

I knew these moonlet word was going to cause trouble.<br />Moonlet is a small natural or artificial satellite. It is moon (see definition above) in which size is considered to be too small. <br />I do not know if there is any limit size for this definition. Maybe somebody could help on this.<br /><br />It is not called moom" because that is a natural hair removal product...not a natural stellite...hihihi...<br />

 

[alokmohan]

Too small moons wre once termed so after Voyager2.I dont recollect any more.Any way it may be poetic.

 

[MeteorWayne]

That is not true. The planets were seen as "wanderers" from ancient times. And without the moon, and no light pollution, the sky can be quite bright.<br />Venus can be bright enough to cast shadows. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[search]

The difference is that the lunar orbiter was self propelled spacecraft and not an artificial satellite, although it may have behaved as such when major maneuvers were not required, and above all the discussion is about natural satellites which do not use propulsion and the word "moonlet" landed in this thread I believe by accident.<br /><br />Unless you know any natural satellite (besides our Moon which was rocketed out into space after an accidental atomic explosion in the fiction serie Space 1999) wich have some kind of mechanical propulsion system a bit more powerfull than the Lunar Orbiter:<br /><br />Extra to this thread from wiki<br />http://en.wikipedia.org/wiki/Lunar_Orbiter<br />Power of 375 W was provided by the four solar arrays containing 10,856 n/p solar cells which would directly run the spacecraft and also charge the 12 A·h nickel-cadmium battery. The batteries were used during brief periods of occultation when no solar power was available. Propulsion for major maneuvers was provided by the gimballed velocity control engine, a hypergolic 100 pound-force (445 N) thrust Marquardt rocket motor. Three axis stabilization and attitude control were provided by four one lbf (4 N) nitrogen gas jets. Navigational knowledge was provided by five Sun sensors, Canopus star sensor, and the IRU equipped with internal gyros. Communications were via a 10 W transmitter and the directional 1 m diameter high gain antenna for transmission of photographs and a 0.5 W transmitter and omnidirectional low gain antenna for other communications. Both antennas operated in S-band at 2295 MHz. Thermal control was maintained by a multilayer aluminized Mylar® and Dacron thermal blanket which enshrouded the main bus, special paint, insulation, and small heaters. <br /><br />P.S. By the way your posts are much nicer.

 

[MeteorWayne]

Actually the larger asteroid is Ida, the moonlet is Dactyl <br /><br />See image here <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[alokmohan]

Gaspra and Ida.Nice to recollect.