It's easier to ask how many were known, and the answer is six.
Currently there are 353 known extrasolar planets (that is to say, outside of our solar system), but it is unknown how many planets exist in the universe.
yes, but as for how many... no one knows since they are unknown lol I hope I answered your question!
It is Unknown
It's unknown. We didn't discover a planet with water, and oxygen.
Scientists predict that they are planets because there wouldn't be random gas' from unknown places
If you refer to creatures from other planets, that is currently unknown.
There are many videos and photos of flying objects. But what they are remain largly unknown. Are they run by aliens for other planets? There has yet to be definitive proof of that.
We are Finding more and more all the time but the total is still unknown to the commity.
Pluto and the unknown planet Falkite (falk-i-tee)
all of them
Sibtract 2010 and 1769
1, 29, 61, 1769