Does Earth has a second Moon?

A moon is any heavenly body that circles another cosmic body (moons can orbit a planet, dwarf planet, asteroid, comet, etc.). The first moon ever found clearly was THE MOON, aka our moon, or the one circling the Earth. In 1610, Galileo found the first moons orbiting another planet when he observed through his telescope and saw four objects circling Jupiter: Ganymede, Callisto, Io, and Europa, Since then, astrophysicists have found hundreds more all over our Solar System (containing 63 moons orbiting Jupiter alone). Mercury and Venus are the only two planets in our Solar System that don't have moons. 

But the Earth only has one moon, right? Theoretically, yes but it's not that simple. There is a inquiring satellite called 3753 Cruithne that, though it circles the sun, is in what's known as an "orbital resonance" with Earth. This means that comparative to us, it does a bean-shaped orbit. It is certainly not "Earth's second moon", as some people have wrongly labelled it: Sometimes Cruithne is all the way on the other side of the Sun from us. 

It takes it approximately one year to orbit the Sun but 770 years to finish its complex bean-shaped loop about the Earth. It's only 5 km (3.1 miles) wide, which is pretty tiny related to the Moon, which is 3,476 km (2159 miles) wide. At its nearby point to Earth, it's 30 times farther away than the Moon, so don't imagine seeing Cruithne with the naked eye.

And Cruithne isn't the Earth's only almost-moon. In 2010, astrophysicists found that--like Jupiter--we have our own Trojan object. These objects have been witnessed at the Lagrangian points of other planet's orbits: they're 60 degrees ahead or behind a planet at a gravitationally steady spot. Our Trojan is called 2010 TK7 and is only 300 meters (984 feet) in diameter. It circles the Sun at Earth's L4 Lagrange point. 

That's not even it: Celestial studies have found numerous tiny objects that seem to be orbiting the Earth (though one may just be a part of the Apollo 12 Saturn V rocket.) Either way, the notion that more than one thing may be orbiting the Earth is pretty cool.

"We all know and love the moon. We're so certain that we only have one that we don't even give it a precise name. It is the liveliest object in the night sky, and unprofessional stargazers take great joy in mapping its craters and seas. To date, it is the only other cosmic body with human footprints."

Source: The DNews


Earth's Moons

The Moon

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