I have really enjoyed reading the speculation about the mysterious comet (named Oumuamua or Comet C/2017 U1) taking a spin through our solar system. What evidence would there have to be to make the argument for, or against? The article below, from Daily Mail Online does a great job describing the object, and is worth a read..
This comet is unusual in many ways from previously observed comets. First off, it's not from around here. Comets from our past experience are trapped by our sun's gravitational pull, and for the most part share a similar plane to Earth and the rest of the planets. This one is coming from a completely different and nearly perpendicular plane to ours. It has come from outside our solar system and is not sticking around - after slinging through our sun's gravity well, it it shooting off and outside our solar system. This is much like the maneuver our satellites and probes perform to get a speed boost to the outer solar system, and in Voyagers case, outside our solar system. Another unusual aspect of this object is it's shape. It is much longer than it is wide - roughly a ten to one ratio. Most comets are closer to a ball shape.
There are radio telescope scans being performed on it to see if it emanates any signals. While I don't think it is a horrible idea, here are a few reasons I think the scans will not be fruitful.
First, it it is an alien craft, it would have taken a long time to get here at it's current speed. It would in fact take centuries to get here from the nearest of solar systems at this speed. Given that it is spending this much time 'on the road', I would think that any kind of technological communication or operation would have to be something more efficient than radio frequency. To conserve energy for the long haul, you don't want to spend any of it radiating away from yourself. Light would be a better way to go - think how much less power a fiber optic cable uses than a radio link. I believe that a true alien ship, capable of interstellar travel, would be beyond rf.
Next, it has been said that this shape is better at protection from radiation. Does that still hold true if you are tumbling? This comet is tumbling, more end over end than a cylindrical rotation. Wouldn't that take away the radiation avoidance profile? It's period of rotation is slightly over seven hours.
Lastly, it is similar in color of other known space rocks. Would a ship be as irregular and similar in texture that of common space rocks?
I'm really hoping that the scans and any other types of observation turn up something, even if it isn't an alien ship. It is just too interesting to simply wave goodbye to. What do you think?