Is This Moon Three?

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.

Comments

size matters?

[Anonymous Coward]

Doesnt an orbiting object need to be of some specific minimum size? or does Saturn have billions of moons that just end up looking like rings?

What's in a moon?

[(H)olyGeekboy]

Just out of curiosity, what is the scientific criterion for a moon?

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? :)

Re:What's in a moon?

[Xunker]

Scientifically speaking, a "moon" is any planetary body that orbits a larger body and causes American students to turn to werewolves whilst visiting France.

Re:What's in a moon?

[NetFu]

New Page 1

Well, here's what Merriam-Webster's Collegiate Dictionary says:

Moon:
-- 1a : a natural satellite of a planet

Satellite:
-- 2a : a celestial body orbiting another of larger size

I think based on these common definitions that these objects, assuming they are found be natural and that they can be proved to orbit Earth, should be called moons. Maybe they don't fit our cultural, unwritten definition of a Moon, but that doesn't change the facts. So, maybe we need to change what most people think of as the Moon...

Re:What's in a moon?

[Bonker]

IANAA, but a professor once told me that a body that orbits another non-stellar body is a moon while a body that orbits a star is a planet or an astroid (astro- from star) depending on its size and regularity of its orbit.

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:What's in a moon?

[kzinti]

Just out of curiosity, what is the scientific criterion for a moon?

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

Re:What's in a moon?

[Autonomous Crowhard]

The best explanation I've ever heard of if a two body system is a planet-moon or two-planet combination is this:

If the center of gravity of two bodies lies inside one of the bodies then that is the planet and the other is the moon. If the center of gravity is between the two objects then it is a two planet system.

Maybe an old Apollo booster?

[ishmalius]

Here is a link I saw just before your posting:

Space.com

4th moon hopes dashed.

[lateralus_1024]

Nasa and I had our hopes of a 4th moon dashed when that NSync kid couldn't cough up the money on time. He hadn't even read the fine print regarding a conditional return.

The Martian Space Defence...

[amorsen]

...has decided to deploy an advanced warning system, due to the number of missiles coming from Earth that have been hitting or narrowly missing Mars in recent years. While planetary defenses have had a decent intercept rate, some of the missiles are still getting through. Hopefully the new early warning system will enable the Martian Space Defense to improve intercept rates considerably.

Third-Moon a Disturbing Libertarian Myth!

[zulux]

We all have grown up with the notion that there are three earth-orbiting natural satlites, but did you know that there is no mention of the third satelite in any media before 2002!

It's true!

See, it's all a plot of the Libertarians - they have been secretly construcing this "third moon" in order to live there and to not pay any of their taxes - taxes that you and I need in order to buy delicious governemnt cheese!

Being cheap bastards, this new moon is nesesairly small - but if you look at it with a high-power "telescope", then you'll realise that this "moon" has been meticulously constructed to look like Montanna!

Complete with Moon-Sheep!

I urge you, the right minded American, to rise up and take a stand! No third moon, unless taxes are to be paid on it.

Ephemeris information for the object

[xlation]

The JPL has an ephemeris generator that now calculates the position of the object.
To see the data:

1. Click the "Target Body" Button
2. Choose "Spacecraft" from the "Select Major Body" dropdown.
3. Select "J002E3 Spacecraft (UNCONFIRMED)"

The 60-degree angle, moons, and whatnot

[devphil]

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.)

Anytime you have something (Foo) orbiting something else (Bar), i.e., once the requirements of "orbit" are met, there are five points of gravitational equilibrium set up amongst the two bodies. They're called LaGrange points. The last two, L4 and L5, are on Foo's orbit around Bar, sixty degrees ahead of Foo (L4) and sixty degrees behind (L5).

L4 and L5 by themselves, ignoring L1-L3, are often called Trojan points, named for this particular group of satellites.

As for the defintion of moon versus just another satellite in general, I believe it has to do with respective mass ratios, and where the fulcrum point of rotation is between the two bodies. Right now our own moon isn't in a true rotation around us, we're in a sort of dumbbell tumble, and the center of the dumbbell is a bit below the ground.

(Actual astronomers please correct me, I'm on a number of narcotic-containing painkillers right now and could have gotten some words tumbled.)

Scientists suspect object is space junk

[AndroidCat]

Scientists suspect object orbiting Earth is space 'junk'

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