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Does anybody know if it is even possible for a planetary moon to have a moon of its own orbiting it?

I hear that the moon is steadily moving away from the earth. Is it due to the suns gravity? Will it eventually go out of earth orbit and circle the sun on its own? Would there be any chance of a posssible collision with earth if this happened or would it leave earth orbit at its closest...

but I have heard of stars appearing green to the naked eye using backyard telescopes.

"There is a big difference between ordinary novas (all are binary stars with a white dwarf companion) and supernovas. Antares does have a distant (green!) companion, but it is a red super giant itself, and will likely become a "Type II supernova" eventually. " Someone on a mailing list I...

Thank you very much for your patient and well-crafted answer.

Well. I'm not much educated about some of these things, it seems people are always saying stuff like " the terrible cold of 'space'" or something. Not only that, but when one gets far away from the sun, so I assumed for any star or starlike source, it gets colder: like Pluto and Charon.

http://science.nasa.gov/headlines/y2004/27sep_shieldsup.htm?aol667632 [Broken] At the above link, it appears there is a high temperature cloud of gas has been colliding with the solar system. What could keep a cloud of gas at such a high temperature in the interstellar medium?

There are moons of asteroids. Just thought it might should be mentioned. :)

If it is an optical aberration why are not the other stars affected as well making them green?

No the "green stars" were in the foreground. Quite bright. Go here to see what I was talking about. http://antwrp.gsfc.nasa.gov/apod/ap030531.html

in some photos, mixed among the red white and blue stars, are green stars. Any idea what causes this?

Actually... How would it become "rogue" in the first place? Perhaps it was thrown about by a supernova and thus would have an interesting structure perhaps. It would probably be older than all our planets. Cool stuff!

Thanks Thats cool if you are right. Maybe we could send a probe to it and find out about extraterrestrial planets. Not that it wouldnt take forever to do it and we probably wouldn't find out anything too shattering. Its still cool!

thanks bob I feel a bit silly now. Nice explanation. :)

thank you bob I was perhaps not clear or I just dont fully understand you. I was wondering about the angular momentum of the people on the earth more than the earth itself, as if our inertia which tries to fly us of the earth somehow negates some of the gravitational force trying to hold us...

Is our angular momentum altering our gravitational attraction to the earth so that if the rotation of the Earth was stopped we would all be attracted to the earth more? If we stopped or slowed the rotation of mars would the gravity be closer to earth normal (and btw the temperature, if rotation...

tiny black holes (again) How could a black hole with an event horizon the size of an atomic nucleus contain enough mass to not let light escape. It seems to me that it would only have the mass of a softball and would thus not be any more dangerous than a softball.

pbh Would these tiny black holes be dangerous? Would they be powerful enough to eat earth up? (insert higgs boson story here) Are black holes infinitely small or do they have a distinct diameter? If they are infinitely small, why would one have more mass than another? Does the mass of a...

In a recent scientific american they discussed the fact that there are clouds of hydrogen entering our galaxy from intergalactic space.

Could Sedna be a trapped rogue planet due to the nature of its distant and highly eccentric orbit? Could a trip to Sedna thus be useful?

Thank you. But we have never actually detected a proton decay right?

heat and energy I assume by non free energy you mean matter and by heat you mean fusion or like in the earths core perhaps. Does heat not mean like in the cores of stars? Would this heat not effect change like fusion? Will there perhaps be a universe which is full of higher elements with...

If energy can neither be created or destroyed, why is there supposedly a "heat death" or any sort of death to the universe.