Does the Earth Have a Second Moon?

Does the Earth Have a Second Moon?

Does the Earth have a second Moon? Many of the planets in the solar system have more than just one personal satellite. Mars has two, while Jupiter has 67, Saturn 62, Uranus 27 and Neptune has 14. Those amounts keep changing but the number is a basic fairly current count of solar system Moons which have been named from NASA. It only makes sense that the outer worlds, with their stronger amounts of gravity, would have more Moons. In the meantime, the Earth only has one Moon, right?

Moons are defined as natural and personal satellites. They circle around planets. However some believe the Earth has more than one Moon. There is an object that readers may have heard of which is commonly called Earth’s second Moon but it really is not. However what it actually is is an asteroid named 3753 Cruithne. Astronomer Duncan Waldron discovered this dim quasi-satellite on Oct. 10, 1986, on a photographic plate that was taken by the U.K. Schmidt Telescope which is located in Australia.

Quasi-satellites are not considered second Moons. They are objects which are in a co-orbital formation with Earth or any other planet. The quasi-satellite revolves around the Sun, just like Earth. Its orbit around the Sun takes exactly the same time as Earth’s does, but their orbit shape is somewhat altered.

As was mentioned above, 3753 Cruithne has been called Earth’s second Moon. This object is around three miles across and has an asteroid’s name. That is due to the fact that it is indeed an asteroid orbiting the Sun, one of many thousand space rocks whose paths cross Earth’s track. Waldron found Cruithne in the mid 1980’s, but it was not until 1997 that its intricate orbit was figured out. It is not a second Moon for Earth; it does not go around the Earth but it is going around the Sun with Earth. Just like all quasi-satellites, Cruithne revolves around the Sun once for every orbit of Earth.

Earth’s gravity disturbs Cruithne, in such a matter that the Earth and this asteroid end up returning each year to almost the very same place in orbit comparative to one other. However Cruithne will never crash with Earth, because its orbit is very inclined in respect to the Earth’s. Cruithne moves in and out of the plane of Earth’s orbit that goes around the Sun.

Orbits like Cruithne’s are not stable. Computer mockups show that the quasi-satellite will spend only about 5,000 years or so in its present orbit. That is only considered a flicker on the extensive timescale of the solar system. The asteroid may then slip into actual orbit around the Earth for a certain period of time, for which then it would actually be considered a true second Moon. However it probably would not stay around for long. Astronomers think that after around 3,000 years of orbiting Earth, Cruithne would then escape back into moving around the Sun.

Basically the asteroid known as 3753 Cruithne is not an actual second Moon for Earth, but its track around the Sun is so weird that sometimes people say that it is. Even though some might think that it would only make sense that the Earth might have a second Moon, in truth it does not, no matter what anyone says.

By Kimberly Ruble


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3 Responses to "Does the Earth Have a Second Moon?"

  1. Michael Schultheiss   July 29, 2014 at 8:45 pm

    Excellent article! You know, I always love seeing articles in Science that take on popular ideas and show how they are in some way flawed, incomplete, or simply flat-out wrong. It is also interesting to learn of this asteroid!

    • Kimberly Ruble   July 29, 2014 at 9:10 pm

      Thanks Michael!!

      • Michael Schultheiss   July 29, 2014 at 9:14 pm

        Absolutely, thank you! 🙂

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