Skip to comments.Earth Must Have Another Moon, Say Astronomers
Posted on 12/22/2011 7:05:56 AM PST by Lonesome in Massachussets
But this was not an object of ours. Instead, 2006 RH120, as it became known, turned out to be a tiny asteroid just a few metres across--a natural satellite like the Moon. It was captured by Earth's gravity in September 2006 and orbited us until June 2007 when it wandered off into the Solar System in search of a more interesting neighbour.
(Excerpt) Read more at technologyreview.com ...
I downloaded the linked article in PDF. Maybe when I get done chewing on that I'll report back.
Captured and released? How exactly did it get "released" to wander off in search of a more interesting neighbor?
bump for later.
It didn’t exactly get released. It just left in disgust.
I think I see it now. It only completed two orbits before moving on - yes?
Did it “wander” off or was it slingshotted? Sounds like it was out for a Sunday stroll and then just moseyed off.
FR's resident Rapturists are slapping their foreheads asking "How could we have missed THAT sign of the imminent End-Of-The-World?"
It’s all the moon’s fault. Without the moon, something not already in Earth orbit can only come by parabolically or hyperbolically (some which crash into the Earth). But a deflection by the moon can put it into a stable orbit, at least until the moon kicks it out again. Which it is likely to do, given how many other moons we have besides the main one, accumulated over billions of years of moon collection time.
The any object orbiting a planet is perturbed by the gravity of every other particle in the solar system. For objects orbiting the earth, the significant perturbing bodies are, more or less in order: the moon, the sun, Venus and Jupiter. Depending on their relative locations, they can provide just enough of a push to free a weakly bound object from the grasp of earth's gravity and continue in orbit around the sun.
Jupiter, of course is the king of capture, remember Shoemaker-Levy? It was captured in 1968, but not observed until 1994, shortly before its perturbed orbit caused it to collide with Jupiter.
The opposite of capture occurs, too. An asteroid approaching a planet's orbit from behind can be given a boost that increases its velocity enough to hurl it out of the solar system. Numerous solar system missions take advantage of the gravitational boost available from Jupiter and the other planets.
Thanks for the nice, succinct explanation.
Damn.....even the asteroids want our welfare money. Go over to Mars! They have free healthcare!
PS: That also explains why the earth and the inner planets do not have significant ring structures and all the outter gas giants do. The relative strength of the perturbing forces, especially the sun, are so much stronger.
Both of Mars’ moons are believed to have been recently (like the past few million years) captured. Phobos is in retrograde orbit, opposite the direction of Mars’ rotation. The effect of tidal drag continually reduces the radius of its orbit and it is expected to collide with mars in a few million more years. (Tides actually increase the radius of our moon’s orbit by about one centimeter per year increase the length of the earth’s day by about 0.0015 seconds per century. The transfer of energy from earth’s rotation to the moon’s orbit is about one gigawatt.)
Too bad it didnt beam up Hussein before it left...
My thoughts exactly. Does it have it's own source of power, if not how did it move out of our gravity field. If it does, how did it get that source of power and is it man made?
Planets can capture objects that cross their orbits. This thing, obviously, was orbiting the earth-moon system, but it came within one lunar distance of something, either the earth or the baricenter. The most likely perturbation that released it from orbit around the earth-moon barycenter was probably due to the moon.
It must have crossed the border from Mexico.
Okay, now that we have all of that orbital eccentricity stuff explained, how about explaining that face on Mars!?
If you look for accurate ephemerides on the web, you will find instead of earth, a mysterious object called EMB. This is the earth-moon barycenter, which must be regarded as the object orbiting the sun as a single mass.
To speak of 2006 RH120 as being "perturbed by the moon" is like saying that Apollo 8, e.g., was orbiting the earth and "perturbed by the moon". I notice that the cited article is ambivalent on this point, which is amusing in light of the flap over the planetary status of Pluto. The embarrassing fact is that the earth-moon system is a double planet.
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