Valve appear to be working on a new game, and no, it isn't Half-Life 3.
Dozens of concept art images have been uncovered by a forum-goer on FacePunch for what could be a new IP by Valve. There's little evidence for its existence outside of the beautiful images, but the user states that the game's working title is Stars of Barathrum, and is an open-world sci-fi game.
Whether or not the rumor is true is yet to be determined, but the series of images present a virtual world set in outer space that hasn't been truly explored since EVE Online. Given the amount of spaceships included in the art, it appears to follow a similar gameplay style set in flight with a variety of ship options.
Sure, it isn't Half-Life 3 or Half life 2: Episode 3, but I never shy away from games that let me enjoy my fascination with astonomy. Be sure to check out the concept art and share your thoughts.