Unidentified Flying Objects ARE real but not what you think.
They are not aliens from some distant star. They are... well unidentified!!
If they were alien space ships you wouldn't say "I wonder what that was - I can' identify it." No, you would say, "Look another damn alien space ship - sixth one today."
Unidentified means unidentified - you don't know what it is - period!
Where do they come from? Well, try Earth since that is where you are.
Consider this:
Man presently might have the technology and ability to send a man to Neptune. At the speed of 50,000 miles per hour we would need to provide life support to the astronauts for several years. It would take 6.4 years at 50,000 mph to go to Neptune – one way. Now consider the NEAREST star. At a speed of 1,000,000 miles per hour it would take 2,885 years just to get there AND that is only to the nearest star!
Unless there really is a new physics unknown to man there is essentially no way for aliens to visit the Earth. If you accept physics as we know it- then there are too few nearby stars for there to be a high probability for the development of technologically sophisticated life forms.
Consider this; if the sun were about the size of a golf ball, 1 inch in diameter, the orbit of Neptune would be 300 feet away. At that scale the NEAREST star would be 461 MILES away.