Earth's Second Moon 137
sbryant writes "According to the Daily Telegraph (free login required): the earth has a second moon called 'Cruithne', which was discovered by a British team.
The moon was previously thought to be an asteroid, but the experts now tell us that Cruithne, which is 3 miles across (4.8km), is in fact
a Trojan asteroid, and has an eccentric horseshoe orbit around Earth which takes 770 years to complete. "
unstable orbit (Score:1)
are they sure it will return to earth again? how many times did it pass here before?
Magneto's base... (Score:2)
Old news (Score:2)
How to get in (Score:3)
Lilith and Other Discoveries of Earth's 2nd Moon (Score:5)
Many of you interested in anstronomy, or just the planets of the Solar System in general, might find this information [arizona.edu] very interesting. It's an account of other people who claimed to have discovered that Earth had a second moon.
I'm not trying to discredit the British team's discovery in any way, but it's still a very interesting read.
The main page of the site (called Nine Planets) is here [arizona.edu].
Re:What defines a big rock/asteroid vs a moon? (Score:1)
The only difference between an asteroid and a moon is whether it orbits the sun (asteroid) or another planet (moon).
There is good reason to suspect, for example, that the moons of Mars are captured asteroids, along with Charon (Pluto's moon).
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Greetings New User! Be sure to replace this text with a
how does this affect my Zodiac? (Score:4)
Time (Score:3)
"Sir, I'd stake my reputation on it."
"Kryten, you haven't got a reputation."
More information on the asteroid (Score:4)
Re:Old news (Score:3)
Just for informational purposes, the asteroid was discovered in 1986, and the paper on its orbit was published in 1997.
At the end of time (Score:3)
Alternatively if we never see the two moons again might be for the same reason we never see Peter Parker and Spiderman or Bruce and Batman at the same time. When we are only "seeing" the dark side of the moon maybe it's getting into a slightly smaller dress and posing as the other one.
Manifold : Time (Score:1)
Wow, this is cool! (Score:3)
You get plenty of kids asking for the earth for their birthdays, but on mine I get a moon! Not bad for a start, is it?
:-)
Greg
Re:unstable orbit (Score:2)
The moon isn't stable, and it will probably leave it's position within a few hundred years. There's some evidence that the moon was in a similar situation about 100,000 years ago. It sort of falls into place every once in awhile.
As a point of interest, the first object discovered in such a peculiar horseshoe shaped orbit was a moon of an asteroid.
A good website about these strange orbits is:
right here [nasa.gov]
What's a moon, anyway? (Score:3)
Not all of us are astrogeeks here. When does an orbiting body become a moon rather than as asteroid?
~~~~~~~~~
auntfloyd
Old news (Score:2)
see http://www.asteroid.yorku.ca/
other moons also seen and reported last night (Score:4)
It's not a moon! (Score:1)
More info can be found here (Score:1)
Scientists Report New Hope For Cheese (Score:4)
Scientists ignited renewed hopes for Extra-Terrestrial Cheese today, as they reported discovery of a second "moon" orbiting the earth. The asteriod, named Cruithne, was first discovered in 1986, but has only recently been subjected to detailed analysis of its highly eccentric orbit and dairyon emissions.
The asteroid will remain in it's orbit for at least 5,000 years. "That's plenty of time for proper ageing," said one astronomer. "And with a diameter of 5 kilometers, this asteroid could supply the earth with Space Cheese for centuries."
Thanks to whoever posted the article "Hidden Agenda [slashdot.org]".
your horoscope (Score:5)
The Divine Creatrix in a Mortal Shell that stays Crunchy in Milk
Re:unstable orbit (Score:3)
The stable points in question are called the familar L4 and L5 (L is for Lagrange the French mathematician who originally discovered them). If I recall correctly, L4 trails the Earth in it's orbit by 60 degrees while L5 precedes the Earth by the same angle.
I suspect that the reason Cruithne wasn't found before is because it probably has an exceptionally elongated orbit and is rather small. It is about the same distance away from Earth as the Sun is!
Incidentally, for those that love to speculate on these things, I don't think it would take much effort to push Cruithne into a more stable orbit. If Cruithne happens to be solid rock (rather than a pile of gravel weakly bound by gravity), then it would make an ideal base for a space station or shipyard.
A bit confusing to a layperson... (Score:3)
However, This [yorku.ca] link says this asteroid actually shares an orbit with the Earth around the sun.
Now, I know that this object has a rather unusual "orbit" of the Earth, but what exactly qualifies it as a bonafied Satellite rather than just a near Earth meteor?
"You ever have that feeling where you're not sure if you're dreaming or awake?"
Re:What's a moon, anyway? (Score:1)
moon 1 n. the only natural satellite of the earth || any planetary satellite 2 v.i. to behave in a dreamy abstracted manner.
So, not being a super astrogeek myself, I guess the key phrase would be 'planetary satellite'. If it orbits a sun, like all those other Asteroids in the Belt do, it's not a moon. Of course, if it's taking 770 years to make its rounds, I -guess- that could be caled dreamy, abstracted behavior, if those scientists have some sort of poetic streak....
Ya won't (Score:2)
Where is Cruithne Now? (Score:5)
I've gone and higlighted it on my NEO map [arm.ac.uk] so you can all see where it is right now. (look near Venus). I presume this is the same object they're talking about.
It's not actually a moon of the earth, at least I wouldn't consider it a moon. Trojan objects aren't bound to their objects in the same way that moons are. Certainly the Earth's influence acts to stabilise the orbit, but if that's teh only criteria for an object being a moon then perhaps we should consider Pluto a Moon of Neptune since pluto is help in the 3:2 resonance with Neptune.
Oddly enough - the 1:1 resonance of trojan objects with respect to the Earth make it almost dynamically impossible for the object to ever become a true satellite of the Earth.
Re:What's a moon, anyway? (Score:1)
First pictures of 2nd moon released... (Score:1)
Re:How to get in (Score:1)
Is there a new password for this recognized international user???????
Re:What defines a big rock/asteroid vs a moon? (Score:3)
- Pluto's low mass would make it difficult for it to capture an independent Charon.
- Charon has a very high mass relative to its parent body
- In fact, Charon and Pluto revolve about their relative center of mass about halfway between the center of Pluto and Pluto's surface
An interesting note (that would be I would be hard-pressed to claim as evidence supporting or countering my claim that Charon was not captured by Pluto) is that during Pluto's summer, its atmosphere encompasses Charon. It's so thin, though, that it doesn't affect Charon's orbit. During Pluto's autumn, the atmosphere "snows-out", and it won't have any atmosphere during winter. This is one of the reasons why launching a Pluto Fast Flyby was such a hot item a few years back -- they wanted to be able to study the atmosphere before it snowed-out. Now, it's not likely a probe will be able to do the flyby in time, but we can always hope & vote.Christopher A. Bohn
Observational Information (Score:3)
It's a numbered asteroid (3753) so the orbit is well-determined. Right now it's within 60 degrees of the Sun so that's a little challenging (but Venus is always within 47, Mercury 17ish, so that gives some perspective).
According to the Minor Planet Center [harvard.edu] it's presently at magnitude 16.2 in Scutum (approx R.A. 18h 34m, Dec. -14 11', but of course that's changing fairly quickly), with a solar distance of 1.205 AU and a distance from Earth of 0.56 AU. It has a diameter of about 17.5 km.
Since it's in Scutum, that means it's also in the Milky Way so the chances of there being few 16th magnitude stars nearby is well, astronomical! :-)
You can get up to date positions, etc. from the website listed above. Please be gentle - it's not a terribly fast server, and a lot of dedicated amateurs/professionals rely on it being available!
Re:How to get in (Score:2)
cipherpunk/cipherpunk and cypherpunk/cypherpunk are both commonly in use.
Moon/Asteroid/whatever (Score:1)
The orbit is a series of spiraling loops that form an overlapping horseshoe, with the Earth in the overlap. This orbital pattern therefore revolves around Sol along with Earth. Very strange, and pretty unusual (actual rarity is difficult to establish).
Here are some decent drawings and explanations of the phenomenon. [yorku.ca]
Re:How to get in (Score:1)
cypherpunks/cypherpunks. Which does work on this site as it's how I got in.
a moon is... (Score:5)
I remember reading _Asimov on Astronomy_ many times as a kid. Here's what I remember from one of his articles:
Anyway, as I read it, this asteroid is not a true moon in the sense of being a satellite of our planet. It still revolves around the sun. However, it is in a gravitational relationship with Terra, as our Luna is. In that sense I suppose it is "a moon".
I think in that same book, maybe even that article, Asimov discussed the Trojan satellites. At that point I don't think anyone had discovered any for earth, but dust clouds were detected in the L4 and L5 positions.
Astronomy is only a neglected hobby of mine, so I may not be totally correct. (I almost got a minor in it, but that's been years ago.)
This is very cool (Score:1)
A couple of years ago, I bought a set of Cosmos video tapes (the old Carl Sagan show). One episode discussed the creation of the universe and the origins of all the elements, etc. He made one quote that summed up my beliefs... "We are Star Stuff". Of course, I am not an astronomer nor an extert in nuclear physics, so I apologize in advance if I offend anyone (I have degrees in Civil Engineering).
Sagan talked about fusion and so forth as well as how gold and other heavier elements are created by exploding super novas (as opposed to champagne super novas ). There is a certain simplistic beauty in the life of a star. It spends billions of years fusing hydrogen molecules into helium then in its dying days, it squeezes the helium molecules into other elements and in a spectacular "swan song" it explodes, seeding space with the basic building blocks of everything around us.
I have often wished that I had enough time to research the parallels between astronomy and various religious beliefs. I think that there are some interesting things that can be concluded from that sort of research.
Trojan Satellites (Score:2)
No, that's not a trojan satellite. A trojan satellite shows up in a place where we would *expect* a satellite, and therefore send probes and astronauts to explore it. It thus gains vital information about us, steals our technology, and uses our DNA to create an army of clones.
They are a serious security threat. The first probe to an apparent sattellite should send a series of ^D to close any trojans before landing.
:)
Such "moons" are old hat. (Score:1)
It has been a well known fact that there are dust clouds at the LeGrange points with the earth/moon system. I remember reading pieces about this in the early 1970s and I suspect that there were even earlier ones. Because such points form a potential energy well, random cruft collects there. However, for anything to be called a true moon, I would propose the following tests: 1) Is it bigger than a breadbox? 2) Is the orbit stable over several million years. The second is true with the dust clouds, and the first is true with this object. Both are not true with either this object or the dust clouds. Not to detract from the research which has more to do with the probablility of becoming toast from an asteroid collision and is well done, but a second moon? I think not.
Cresent? (Score:1)
Re:Crescent? (Score:1)
Intersting thought, though.
Re:unstable orbit (Score:1)
Also, does anyone know if Cruithne was part of the earth at one point, as the moon was?
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Re:unstable orbit (Score:1)
>discovered in such a peculiar horseshoe shaped
>orbit was a moon of an asteroid.
I'm not sure to what you are referring. Can you be more specific?
Then there are two two moons of Saturn (sorry, I forget the names) which are on real horseshoe orbits. I hear some astronomers actually beleived they were going to collide and tried to watch, only to see them gradually turn around. Hehe
Re:unstable orbit (Score:2)
www.space.com also has an article (Score:1)
Re:unstable orbit (Score:4)
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love songs (Score:1)
<music>
When the moons hit your eyes like
<music&/gt;
Old news, and not so British? (Score:1)
It might also be that there are several such "Troyan" asteroids, so I'm not totally sure that this is the same one.
I think the orbit was calculated by Seppo Mikkola in Tuorla Observatory, in University of Turku, Finland. But I'm not too sure about this, the following article seems to have two Finnish authors, but the primary author may well be British. It may be that the observations were British, or something like that.
See:
*Wiegert, P.A., *Innanen, K.A. and Mikkola, S. 1997: The Earth companion asteroid 3753 (1986 TO) - Nature 387: 685--686.
"Trojan" satellites (Score:3)
This cluster wasn't hard to explain - the "three body problem" can't be analytically solved for the general case, but it can be easily solved for cases where M1 >= M2 >> M3. This solution shows five points there the gravitational attraction of the two large bodies balance. IIRC all of these points are "stable," but objects can orbit those points for billions of years before friction with the solar wind, gravitational attraction from other objects, etc., cause the object to return to a normal orbit.
The five Lagrange points are named L1-L5. As I recall, if M1 >> M2 then
L1 = on M1-M2 line, opposite of M2 (e.g., "counter-earth")
L2 = on M1-M2 line, between M1 and M2, (e.g., the solar observer satellite)
L3 = on M1-M2 line, beyond M2
L4 = 60 degrees ahead of M2 on M2's orbit
L5 = 60 degrees behind M2 on M2's orbit
Since it's been twenty years since I thought about this, I might have L1-L3 permuted and L4-L5 reversed.
Re:How to get in (Cypherpunk:Cypherpunk works.) (Score:1)
what the heck are you talking about? (Score:1)
The concept of a "horseshoe" orbit is laughable. If it is in a closed orbit, that orbit must be an ellipse (see Kepler's first Law). A horseshoe is open ended, and while open ended orbits do exist, the object would only pass by the earth once in the orbit, achieve escape velocity, and never return.
In other words this article, and yea verily this Slashdot post, makes no sense whatsoever.
The nature of international astronomy (Score:2)
The object was discovered by a British team, but it's "satellite" nature was not known until a Canadian team performed the analysis (contrary to an earlier posting which credited one at a... Turkish university?).
Alors, we have a co-discovery... unreported, as is usual for matters of Canadian pride. But astronomy and other such international sciences is to be about the high purpose of fact and truth and the extension of knowledge's frontiers, not nationality or whatsoever nation a research happens to be working in. Consider all the discoveries by foreign (non-Chilean) researchers in Chile's Atacama Desert...
By the by, there is some interest among a select band of Canadians to launch a probe to the asteroid...
Cruithne's orbit appears to be stable (Score:2)
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Suitability for a space station: nil (Score:3)
- The orbit is inclined 20 degrees to Earth's. Change-of-plane maneuvers are very costly in terms of propellant.
- Being so close to the Sun, there is a smaller likelihood of Cruithne having deposits of the essentials for life-support: water, ammonia or methane ices. These would make it more attractive to set up shop there, because resupply costs would be drastically reduced.
As it is, we're probably better off looking for something like an extinct comet nucleus, regardless of its orbit, if we want to set up a space station far from Earth.--
Re:What's a moon, anyway? (Score:2)
The classical thought on this is that the orbit of these satelites are pretty eleptical and regular. Often times, these satelites are in "tidal lock" with their planet, just like our Moon is and most of the other moons out there with apriciable mass. In one sense, objects like this asteroid are satelites...they just don't follow a circular orbital path.
People look up at the sky and look at our Moon, especially on nights like the recent Lunar Eclipse and forget how special that thing is. No where else in this star system will you find an object that big(the Moon) orbiting an object this small(Earth). Okay...Pluto is an exception too but Pluto is special in its own little way.
Well, you don't... (Score:2)
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Re:"Trojan" satellites (Score:1)
The asteroids at the two points 60 degrees before and after were, just after discovery, named after the Greeks and Trojans named in the Illiad. The prefered shorthand do describe those objects as a group became "trojans", which was later generalized to all objects in similar orbits.
Steven E. Ehrbar
Re:Old news, and not so British? (Score:2)
Wiegert is Canadian, and works with Innanen in York University in Canada. Innanen and Mikkola are Finnish, and Mikkola works in Tuorla Observatory.
The asteroid has a homepage:
http://www.asteroid.yorku.ca/ [yorku.ca]
I think the British researchers photographed the asteroid in 1988, found it from the film plate, and possibly even made observations of its subsequent locations. They did not, however, calculate its orbit, and thus did not actually "discover" the asteroid as "second moon" of Earth. However, according to the rules, they were given the right to name the asteroid.
It should be noted that there are probably thousands of asteroids which have been photographed, but have not been identified as asteroids. For example, Pluto was photographed in the Tuorla Observatory some 8 years before it was photographed and identified as a planet in U.S. There might be several hundred asteroids which have been identified, and their positions have been measured, but the orbit has not been calculated.
More Asteroids links (Score:2)
http://markn.users.netlink.co.uk
http://www.atarihq.com/2678/revi ews/asteroids.html [atarihq.com]
http://www.funescape.com/games/as teroids/main.htm [funescape.com] - Java required.
-M
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"Trojan" satellites, addendum (Score:5)
Note also that there is a difference between "equilibrium" and "stability". Equilibrium just means that there exists a static solution to the equations of motion (albeit static in a rotating frame of reference in this case). Stable means that the static solution, if perturbed, will return to the equilibrium instead of drifting off into some dynamic orbit. The L1-L3 points are stable to perturbations in one direction (the tangential, if I recall), but they are unstable to perturbations in the other direction. Consequently, one doesn't expect to find long-lived orbits at these locations. The L4 and L5 equilibria are stable against all perturbations, so one might expect to find objects in long lived orbits at these locations, like the Trojan asteroids, for instance.
The original poster's confusion arose because the earth has two sets of Lagrange points associated with it. One comes from the earth-moon system (in which the earth is M1 and the moon is M2), and the other comes from the earth-sun system (M1==sun, M2==earth). An object at L4 or L5 in the earth-moon system would appear to orbit the earth in synch with the moon, while an object at an earth-sun lagrange point would appear to orbit the sun in synch with the earth. So, it's a little far-fetched to call an object at the earth-sun Lagrange points a "second moon", although such an object is in some sense more deeply associated with the earth than an object in some random solar orbit.
Finally, one should remember that the Lagrange points are solutions of the restricted 3-body problem which presumes that there are only three bodies in the system. Obviously, that isn't the case in our solar system. For instance, I've seen people argue that the earth-moon L4 and L5 points aren't really stable because of the sun's influence. Similarly, the lagrange points between the sun and most of the outer planets are thought to be disrupted by Jupiter's gravity. Consequently, I wouldn't be surprised if Venus' gravity had a tendency to destabilize the earth-sun Lagrange points, resulting in objects trapped there eventually escaping into regular solar orbits.
-r
Re:unstable orbit (Score:1)
>If Cruithne happens to be solid rock (rather than a pile of gravel weakly bound by gravity), then it would make an ideal base for a space station or shipyard." Let's do it.
Re:what the heck are you talking about? (Score:1)
The concept of a "horseshoe" orbit is laughable. If it is in a closed orbit, that orbit must be an ellipse (see Kepler's first Law).
Ahhh... Newtonian mechanics. BTW - Newton got thoroughly beaten by this little theory published by some guy named Einstein earlier this century.
But seriously... Newton's law's don't work very well for "n" bodies problems, where n > 2. Furthermore, there are some serious non-linear differential equations that come into play for something as complex as this. Think of it this way:
The asteroid would follow an elliptical orbit if all the other bodies acting on it stood still. Since the Earth, Mars, Venus, etc... are all moving, and in doing so act on each other, the "ellipse" gets smeared into this weird kidney bean shape. The stability of this orbit is questionable, and certainly this solution to the problem of co-existing with all the other planets/planetoids is rare. But it is certainly possible.
Temkin
Re:What defines a big rock/asteroid vs a moon? (Score:2)
Re:what the heck are you talking about? (Score:1)
I recieved an email from someone trying to debunk what I said. He referenced a webpage that is very informative. http://www.asteroid.yorku.ca/ [yorku.ca].
This shows the asteroid's true colors. It does not orbit Earth. It orbits with Earth, much like the trojans around Jupiter, but a little more funkily. It is not a moon. That is what threw me about the "horseshoe" orbit.
Future article (Score:1)
Great, the way he said "the earth now has a second moon. Its name is Cruithne. Luv dat.
Where is my mind?
Re:Suitability for a space station: nil (Score:1)
We should just ask Mr. Gates if he would like to make a small donation of $500M for a second earth orbiting telescope project instead.
Loren.
cruithne.com already taken (Score:1)
Jeez.
Re:Scientists Report New Hope For Cheese (Score:1)
Re:unstable orbit (Score:1)
This link has more info [nasa.gov]
Re:what the heck are you talking about? (Score:1)
For example, just by combining two ellipses (one around Earth and one around Sun), you can get weird orbits.
Actually, none of the orbits of the planets are "perfect ellipses around the sun", but because the planets also orbit each other a little (although those orbits are "open"), the actual orbits of planets are infinitely complex. And, chaotic. (Remember, three-object problem has not been solved.)
Re:unstable orbit (Score:2)
The ISS isn't projected to have 'simulated gravity' except in specific lab areas.
Observatory? To observe what? (Score:3)
- You still have the Zodiacal light fogging your pictures of nebulae; to get away from that, you need to go further from the Sun.
- You can't see much more of the Sun from a 20-degree inclined orbit. For that you really want a polar orbit. If you want to see solar flares and prominences from a different angle, you'd want to be at the Earth-Sun L4 or L5 point instead of on Cruithne, which varies its angular separation from the Earth-Sun line throughout the year.
- You can't see much more of the sky from Cruithne than you can from the Moon's L4 or L5 point, and it's a lot faster to get data back from the shorter distance.
- Last and most significant: what kind of observatory needs to be gotten away from Earth and put on a rock somewhere out in the middle of nowhere, so that you can still only see the half of the sky it doesn't block? Why not a free-flying probe?
An observatory which is best suited to Cruithne than somewhere else would have to have some very specialized requirements. I can't think of anything that has requirements remotely like that. Note: I am not an astronomer.--
Here ya go. (Score:2)
http://www.telegraph.co.uk:80/et?ac=0020682315192
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- Sean
Re:what the heck are you talking about? (Score:1)
As I said in a reply to a reply, this asteroid is not a moon of Earth's. It does not orbit the earth, it is just heavily affected by it. If it were orbiting the earth the horseshoe orbit would make little sense. Although I guess a very small asteroid could be affected by the moon in such a way, but because the gravity wells are so much smaller it would be far less stable and therefore less likely to happen.
Re:Where is Cruithne Now? (Score:1)
This is not a happy thought to have on a regular Tuesday.
I wanted that movie Armegeddon dead and buried!!! Now that I hear how possible it is I shudder to think...
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Our moon orbits sun, perturbed by earth (Score:1)
So both Cruithne and Moon trace out a repeatable path with respect to the Earth, but both can be considered to really orbit the Sun.
--Neal
Re:Actually, it's everything above Iron (Score:1)
Space Race Revisited? (Score:3)
Does this mean that Russia can beat JFK's challenge of the early '60s to send men to the moon first?
You still have a chance, Russia! RUN! RUN!
Editorial bias? (Score:2)
If you wanted to post it yourself, that's fine; but at least include the links, to make the story more useful to folks.
Wait... (Score:1)
A dangerous nightmare weapon? (Score:1)
User: Slashdot Password: Slashdot (Score:1)
Username: Slashdot (case-sensitive)
Password: Slashdot
--
Patrick Doyle
Re:unstable orbit (Score:2)
Re:More information on the asteroid (Score:1)
At the bottom it says POV Ray was used for the animations. It's an open source asteroid!
space.com article: "More Moons Around Earth? ..." (Score:1)
Re:unstable orbit (Score:1)
"Are there any other known horseshoe orbits?
There is only one other known case, involving the small moons Janus and Epimetheus of the planet Saturn. Janus plays the role of the Earth in that case, and Epimetheus that of Cruithne."
Re:Observatory? To observe what? (Score:1)
Other than that, I agree that Cruithne is essentially worthless as an observatory. If we wanted one further out than the moon, there's always the Sun-Earth L4/L5 points, as well as other planets, or their Lagrange points, or the larger asteroids. But close in would be suitable for me, as we would need to be generating a lot of data from it to keep all those seti@home computers busy
Re:unstable orbit (Score:1)
Another good story on CRUITHNE, the astronomical object formerly known as an asteroid, is at space.com. [space.com]
I wonder why this is a story now?
\/0!d
Better article (Score:1)
How do you pronounce "Cruithne"? (Score:1)
Re:Better article (Score:1)
But see "Near Earth Asteroid 3753 Cruithne"
http://www.asteroid.yorku.ca/It does NOT orbit Earth and it therefore is NOT Earth's second moon. It does have a Keplerian elliptical orbit about the Sun but this orbit isn't the same as the Earth's and doesn't intersect it.
Re:unstable orbit (Score:2)
Now where would we find something like that?
Too bad it'd be beyond our technology to get there. [nasm.edu]
Re:How do you pronounce "Cruithne"? (Score:1)
THROAT WOBBLER MANGROVE
Your Working Boy,
Re:unstable orbit (Score:1)
If any astro-computer geeks out there feel like showing off, I happen to know that there's research money out there for this.
here's a Cruithne applet (Score:2)