From messages sent to NASA’s “Ask an Astrobiologist” Web page. David Morrison, who responds to the questions, has received more than 5,000 messages related to “Doomsday 2012” and the planet Nibiru, sometimes called Planet X, which some believe will collide with Earth on December 21, 2012.

I have read your website about Nibiru not existing over and over again and yet I still worry. Sometimes I cry myself to sleep because so many people said they’ve seen it. I know the astronomers watch the sky every single night, but how do you know for sure that nothing is up there?

So there is no Planet X coming toward Earth? We are not in any type of danger, right? If there was a Planet X would we be able to see it by now?

I am thirteen and am very scared about Nibiru. Is it possible it could be behind the Sun? If so, what can we do to stop it?

Last winter, I got extremely depressed because of my fears of December 21, 2012. Every day would be filled with fear. Every little noise I heard I thought something was happening. I wouldn’t watch the news for fear of seeing something bad or scary. I am seventeen years old, and I actually did contemplate suicide because of all the rumors.

I am fourteen, and I have been researching the 2012 theories since I was ten. I have read about galactic alignment, magnetic-pole reversal, Nibiru, and solar flares. I have seen videos and images and articles about sightings of Nibiru. Are you guys covering something up? If so, tell the truth.

I’m fifteen, and I’m terrified of all these rumors, and I don’t know how to get over it. I keep hearing about the fifth sun and how it affects the North and South Poles. If you could honestly tell me there is no danger whatsoever to Earth on December 21, 2012, that would make me feel a lot better, because sometimes I think suicide would help.

Would you mind talking to my son Collin over the phone? He is having nightmares about this so-called Nibiru colliding with Earth. I am concerned about his mental health. He is an impressionable thirteen-year-old boy.

I’m a twelve-year-old boy. The Moon hasn’t been rising this past week and the Sun was rising and setting in different places each night. I’m freaked and my parents don’t believe me. I can’t even focus on my schoolwork. Please tell me the truth about the end.

I just wanted to thank you for the work that you are doing. I sometimes feel as though all of our new technology is just allowing the nonsense to grow ever larger, so I appreciate the attempt to shed some light on our self-generated darkness. The truth can be elusive, but I still think it is out there waiting for us to discover it.