Is there a explanation for a moving "star" Is this a trick of the eyes?

Question

I am a amateur when it comes to astronomy... I don't even have a telescope but I often like star gazing. Many times (but not always) I start staring at a star and it starts moving erratically... never fast but not slow either... it also stays in one vicinity (it isn't zipping all over the sky).

Like I said, its movement is erratic (so I don't think it is a satellite). I can see fixed or nearer objects in the sky (brighter stars) that always seem to be on the same spot in the sky... i.e., the moving "star" is closer to the fixed object and then moves away from it.

Does anyone know what I am talking about??? I don't think these are UFO's... I am thinking this is a trick of the eye but I purposely don't allow myself to get tunnel vision when I am seeing this.

I hope I explained this clearly.

Answer 1

You have observed autokinesis. The eyes are normally always darting back and forth in order to take in a wider picture. The brain normally patches the different pictures together into a coherent whole, but it does this based on cues in the images, not the known positions of the eyes. As a result, when there are not enough cues in the images (such as when looking at a star on a dark background), the images can no longer be combined and you perceive the actual motion of the eyes. Autokinesis is a leading cause of UFO sightings.

Answer 2

It is basically an optical illusion. With no reference points nearby to gage its position your eyes trick you into thinking it is moving around. If you clamp a stick on a tripod or something so that it points at the star, you will see that it isn't moving after all, except for the usual gradual rising and setting motion that is too slow to easily see. And that motion proceeds in one direction at the same speed all the time.

This illusion is responsible for so many people looking at Venus and swearing it is a UFO darting here and there. I have even seen home video that the person who took it said was a UFO. You can see it moving in and out of the field of view as he exclaims how it is moving. But it is CLEARLY an out of focus star or planet in a hand held camera at full telephoto and he is fooling himself into thinking it is moving and so magnifying his own unconscious hand movements trying to chase a non existent motion.

Answer 3

The thing that's got me stumped is the "staying in one location" business.

Otherwise, I would say that you are seeing an artificial satellite. LEO (Low Earth Orbitting) satellites can create something called an "Iridium flare" (http://www.satobs.org/iridium.html#iridium)

These are actually predictable and are pretty cool when you first see them.

there are a host of other satellites that are visible as well. heck, you could be seeing the International Space Station!

Have fun with your newly found interest in Astronomy. It's the last science where amateurs can truly still provide significant value.

Answer 4

could be a small imperfection on the lens of your eye, the light could be bent around it, while you move you head and or eyes even tiny unnoticed amounts, the object would appear to zip around the imperfection. This is common in telescopes and is actually a principle of einsteins that allowed us to locate black holes in outer space. The black hole being the imperfection and more distant star light being bent around it, appearing in two places at once.