Try to imagine a world that knows only night and the unabated, but distant stars filling its sky. Such worlds without a partner-star have been theorized to exist but finding them is very difficult, for multiple reasons. However, researchers at the University of Montreal with data from the European Southern Observatory's Very Large Telescope and Canada-France-Hawaii Telescope have found one.
The most obvious reason these planets are hard to find is that there is nothing to illuminate them, at least nothing that would do so as well as sun. However, multiple potential homeless planets have been catalogued, but there is not enough information to prove they are planets and not just brown stars; failed stars. Luckily this planet, CFBDSIR2149, does provide us with that information, including its age of between 50 and 120 million years, a mass four to seven times that of Jupiter, and a temperature of 400 ºC. The reason we can get this information, especially its age, is that it is apparently traveling with a group of stars (though they are not gravitationally linked to the planet, like the Earth is to the Sun).
Sadly that information is not enough to answer the obvious question: how is it homeless? Did the planet form on its own or was it ejected from a solar system? Only further observations may be able to determine that.