If it is a brown dwarf star than you wouldn't be able to see it because it's cool and doesn't radiate enough energy but if in the right position for the sun the reflect energy off of it then you would be able to see it through filters like the guy on the video used. Quoting: Anonymous Coward 2704006
You see - this is where all the Nibiru-nutters fall down.
Contrary to what they try to tell people, Brown-Dwarfs are NOT difficult to see.
A Brown-Dwarf is the in-between step between Gas-Giant planet (like Jupiter), and a small star.
Gas-Giants, and stars, are made of pretty much the same stuff - Mostly hydrogen, some helium, and only traces of other elements.
Above a certain mass (around 80 Jupiter masses), there is enough gravity to compress the core to the point where full-on nuclear fusion occurs.
But there's a point, at around 13 Jupiter masses, where an object can fuse deuterium - creating heat, and some light.
This is what's known as a 'Brown Dwarf'
They are VERY dim, by stellar standards, but they do show up in infa-red.
The point the Nibiru-nutters ignore - deliberately IMHO (the knowledgeable ones, anyway) - is that a brown-dwarf will reflect light in the same way as a large Gas-Giant planet would.
If there were an object of more than 13 Jupiter masses, near enough to pass anywhere near Earth this year - it would be VERY visible.
Bear in mind that to reach Earth this year. it would need to be ALREADY closer to us than Jupiter is.
Jupiter is currently quite bright currently to the west after sunset - Imagine something AT LEAST 13 times that mass - and NEARER.
It would be unmissable...
So where is it?