Is This Moon Three? 317
tetrad writes "The BBC reports that a new object has been discovered orbiting Earth. It's possible that it's just a piece of space junk, but more likely it is a rock that has been recently (in the last year) captured by our planet's gravitational field. If the object is confirmed to be natural, this would be Earth's third moon. (Did you know there were two already?)" Here's our earlier mention of Earth's alleged second moon. Update: 09/12 04:52 GMT by T : Reader cscx adds a link to an article running on space.com which says this newfound object may be some trash from the Apollo missions.
size matters? (Score:4, Interesting)
What's in a moon? (Score:4, Interesting)
The "trojan asteroid" described in the previous story is only 3 miles wide and take 770 years to orbit the earth. That is not what elementary schoolteachers say is a moon, a la Jupiter's many moons... giants like Europa and IO.
I also heard a while back that Charon might not be a real moon either, because of size or rotation or something? Huh?
I'm not versed in astronomy enough to know, so does anyone have an answer for laypeople, so I can talk with people at work about this?
Ask Buzz what he thinks about it. (Score:2, Interesting)
Re:What's in a moon? (Score:5, Interesting)
Thus, the Pluto-Charon system is probably much more accurately labeled as either a pair of asteroids due to size considerations, or a dual-planetary system because their orbits are highly regular, albeit at a significant pitch compared to the other 8 planetary systems.
I've also heard that the Earth/Luna system should be considered a dual-planetary system because Luna has a much higher percentage of it's parent planet's mass than other moons... This jives with the 'Planetary Collision' theory of moon formataion, in which the moon is actualy a significant chunk of Earth, torn off early during our planet's formation.
The 'second moon', Cruithne, fits in with a large category of non-moon, non-planetary, non-asteroid bodies in the solar system. If you ever study the 'Trojans', you know that there are huge bodies of apparent moonlets that sit on a sixty-degree angle from Jupiter's, directly along Jupiter's orbit from the sun. (They are apparently held in such a strange place by the gravity of Jupiter vs. the gravity of Sol.) Rather than calling Cruithne a moon, we're probably better off adding a new 'common' cetegory to our solar classification to include it and the Trojans. AFAIC, there's no reason not to call these all Trojans and be done with it.
Re:If this is true.. (Score:3, Interesting)
Re:The Martian Space Defence... (Score:3, Interesting)
* Sort of inner. Scientology is like a Mystic Onion. You peel it off layer by expensive layer until you reach the center of the onion. (Where you have nothing -- except tears.)
Stop laughing, this is science damn it!
Re:What's in a moon? (Score:5, Interesting)
Isaac Asimov, in one of his popular-science articles, once presented a well-reasoned argument that the Earth and Moon should not be considered a planet and satellite, but a double planet. He formed his argument by comparing the masses of all the other moons in the Solar system to the masses of their primaries, and showed that the Moon:Earth mass ratio was far greater than that of any other planet/satellite pair. He suggested that we could account for this "outlier" by considering the Earth and Moon to be a double planet.
Whether this argument would stand up to real scientific scrutiny, I don't know. It sounded pretty good to me, but I was just 10 at the time. Maybe it was just gee-whiz stuff made up to impress 10-year-olds, but that doesn't really seem like Isaac's style.
Does anybody else remember this essay?
--Jim
Scientists suspect object is space junk (Score:4, Interesting)
Scientists think a newly-found object orbiting the Earth could be a remnant from the Apollo era.
Experts at Nasa's Jet Propulsion Laboratory believe its brightness and distance shows it's a rocket booster.
'J002E3' was discovered on September 3 and listed by scientists as a minor planet or asteroid.
But Nasa's Donald Yeomans believes that designation is erroneous.
He told Space.com: "It's most likely a spacecraft. It's not likely to be a natural object, not in that kind of orbit."
He said minor planets or asteroids tend to be on strange orbits gravitationally-influenced by the Sun. This does not appear to be the case with this object.
Nasa are currently running computer calculations and expect to be able to identify the object conclusively soon.
Story filed: 10:39 Thursday 12th September 2002
Another Criteria (Score:3, Interesting)
In the case of the Earth/Moon system, it is called a double planet because the path of the moon from the point of view of the sun in strictly concave -- that is it dosn't loop back on itself as do other moons.