I was told that there was a second Cruithne and even more...very oddly named moons. What is your opinion?
2007-01-18 00:00:17 · 17 answers · asked by Shaun W 1 in Science & Mathematics ➔ Astronomy & Space
Cruithne is not really a moon, because Earth and Cruithne are not gravitationally bound. (Luna IS a real moon.) But Cruithne is locked into a 1::1 resonance with Earth.
Two more asteroids in earth-resonant orbit have been found, 1998 UP1 and 2000 PH5.
But these things are asteroids that orbit the Sun, although very near the Earth, not moons orbiting the Earth.
2007-01-18 00:48:38 · answer #1 · answered by campbelp2002 7 · 1⤊ 0⤋
We actually have have one moon (i.e. a natural satellite) but Cruithne has a companion orbit to the Earth. There is one other that was originally named Asteroid 2002 AA29. Both of these share an orbit with the earth and are in a horseshoe orbit so some people may say they are Moons of Earth
2007-01-18 02:16:51 · answer #2 · answered by Anonymous · 0⤊ 0⤋
With a capital M, there is only one Moon (that's its name).
With a lower case m, moon = satellite and there, it depends what you mean by satellite.
"A satellite is any object that orbits another object (which is known as its primary)."
"The general criterion for an object to be a satellite is that the center of mass (known as the Barycenter) of the two objects is inside the primary object." (1)
Using the above definition, Earth has only one natural satellite: the Moon.
The original sense of the word "satellite" is of a person who gravitates arounda more important person, doing chores for that person in return for favors. (not a slave)
You had the movers and shakers of Rome, and lots of people would try to get in these people's good books.
In a more modern sense, if you know a Minister of government and you always manage to meet him at breakfast just to chat and do some minor tasks to please him, just so that, one day, you could get some favor, then you are a satellite (old sense); you don't need to be around him all day. A somewhat regular encounter may be sufficient.
Then, there are small objects in the Solar system, whose orbit is affected by Earth's in such a way that there are regular (or semi-regular) encounters.
The first one I heard about is asteroid Toro (minor planet 1685) it is on an orbit with perihelion between Earth and Venus, and has an orbital period that is in resonance with both.(2) So, after a regular number of orbits, it passes through the same point in relation to Earth's position; it does the same for Venus. It is like a person who has breakfast with the Minister and lunch with the contractor who wants the contract.
Minor planet 3753 Cruithne also has an orbit with a special relationship with Earth's orbit (but it is not in orbit around Earth). The average of its orbital period around the Sun is exactly one year, but each orbit is not exactly one year. So its "closest point of approach" appears to move away from us and then get closer again, with a period a a little less than 400 years.(3)
PS:
Go to:
http://neo.jpl.nasa.gov/cgi-bin/db_shm?sstr=3753+Cruithne
Below the diagram (animation), select:
1 Day
Center on Earth
remove the planet labels
Then click on the double arrow >>
You will not that once a year (near October in 2018) Cruithne and Earth pass very close to each other.
2007-01-18 01:20:14 · answer #3 · answered by Raymond 7 · 0⤊ 0⤋
The Moon is Earth's only natural satellite. The near-Earth asteroid 3753 Cruithne is now known to be a companion, and an unusual one, of the Earth. This asteroid shares the Earth's orbit, its motion "choreographed" in such a way as to remain stable and avoid colliding with our planet. This relationship was revealed in a paper by Paul Wiegert, Kim Innanen and Seppo Mikkola, and published in the British-based science journal Nature on June 12, 1997.
2007-01-18 01:18:14 · answer #4 · answered by Bill G 2 · 0⤊ 0⤋
On a typical evening, you can see all of Earth's moons. Go out and look up in the sky. Count all of them. You will probably only need 1 hand.
2007-01-18 00:08:45 · answer #5 · answered by gebobs 6 · 0⤊ 0⤋
This is Sure
there is only ONE moon the earth has
2007-01-18 00:09:09 · answer #6 · answered by Keypper 2 · 0⤊ 0⤋
Actually, it has more than six billion. One on the back end of each person living on it, and one in orbit. Seriously, there's only one moon orbiting the Earth.
2007-01-18 00:04:21 · answer #7 · answered by togashiyokuni2001 6 · 0⤊ 0⤋
There is only 1 moon.
2007-01-18 00:04:01 · answer #8 · answered by Bella 7 · 0⤊ 0⤋
Earth only has one natural satellite, The Moon. There are no other ones.
2007-01-18 00:52:09 · answer #9 · answered by bldudas 4 · 0⤊ 0⤋
No kid , there is only one moon around the earth , but other plants got mor than one moon, as Jupitar it got 63 moon, Mars got 2 moon.
2007-01-18 00:09:46 · answer #10 · answered by hossam_amin2010 1 · 0⤊ 0⤋