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NASA floated that idea in 1983, based on new infrared images captured with its Infrared Astronomy Satellite. The satellite was able to document 350,000 infrared sources, many of which had not previously been identified. But subsequent studies with more powerful instruments showed that none of the mystery objects were planets in our own solar system.

DESTRUCTION BY PLANETARY ALIGNMENT

Myth: On Dec. 21, 2012, the sun and the Earth will come into alignment with the center of the Milky Way galaxy. Disastrous cosmic forces will be unleashed at the moment this occurs. Alternatively, the Earth will be harmed through alignment with a supermassive black hole at the center of galaxy. Or by aligning with all of the other planets.

The Facts: Every year in late December, the Earth and the sun do align closely with the center of the galaxy, but this year's alignment won't be exact. The Earth also won't be aligned with other planets in late December.

"Alignments occur. They're interesting from a pictorial point of view, but they really have no bearing and effect on the earth," said Yeomans.

Black holes do have gravitational pull, but the supermassive black hole at the center of the galaxy is tremendously distant from us -- about 28,000 light years away, according to Hertz, director of astrophysics at NASA headquarters -- and its gravitational effects on the earth are negligible. Hertz said black holes don't emit radiation.

"We can't even see the black hole at the center of the galaxy," he said. "The only reason we know it's there is because we can see stars orbiting it."

EARTH'S CRUST SPINS 180 DEGREES

Myth: On Dec. 21, the earth's crust will change rotation, tearing apart land masses and wiping out the population. Alternatively, the globe will flip around 180 degrees when the poles shift in December.

The Facts: Earth has two kinds of poles: rotational and magnetic. People who believe this myth are confusing the two, according to Fraknoi.

The axis of rotation is the imaginary line through the center of the Earth, around which the planet spins. It doesn't move. By contrast, the magnetic poles aren't fixed to one location. They're a reflection of the magnetic field that exists on the planet. The magnetic poles drift a little bit each year because of the complexity of the electrical currents inside the Earth. They can also swap places over long geological periods.

Fraknoi says this "small core of scientific truth" has been twisted into a doomsday myth by some people posting messages on the Web.

"Somehow, people have gotten (magnetic poles) mixed up with the rotational pole, so they say, 'My goodness, on Dec. 21, in one day, there's going to be a flip of the earth's rotation, so that we're going to either rotate the other way, or the whole planet is going to turn upside down.' This is absolutely ridiculous," he said.

The Earth's magnetic poles only swap places about once every 400,000 years, according to Morrison, and such a change isn't expected for several millenia.

If a magnetic change occurred, it might theoretically be accompanied by higher radiation levels, but life on Earth has continued to thrive and evolve in the past in spite of similar events, Fraknoi said.

While it's true that magnetic poles can shift over time, Fraknoi said it's nearly inconceivable that the earth's rotation could change, or that the entire globe would flip 180 degrees. He pointed out that reversing the Earth's rotation would require the influence of another tremendously large object in space, which would already be detectable.