Recently scientists in Hawai’i have found a new planet, but this one is different. This one doesn’t have a star. Astronomers have found almost 1,000 planets outside of our solar system. But they all orbit stars. We’ve hypothesized that there are failed stars out there, that never got hot enough to start fusion in their cores, but they’re very difficult to find because they’re so dim.
But PSO J318.5-22 is about 80 light years from Earth, in the Beta Pictoris group of stars, and it isn’t orbiting a star. It’s just moving along with a group of 17 stars, in the same direction. It likely formed with them, around 12 million years ago. We found it by direct imaging, that is, by looking at it.
All the other exoplanets we’ve found have been by observing the main star and looking for wobbles caused by planets, or changes in light levels from a planet moving across the disc of the star. This makes them easier to find, but hard to study because the star outshines them.
Stars form in nebulas, large clouds of dust and gas. When the core is hot enough, with enough pressure, it stars fusing hydrogen into helium, which releases tremendous amounts of energy, forming a star. It looks like this planet, which is a gas giant, wasn’t massive enough to start fusion. There may be many other failed stars like this around, but they’re very hard to find since there isn’t a luminous star next to it.
Since PSO J318.5-22 isn’t orbiting a star, we can observe it directly. It’s a great chance to observe a failed star, soon after fusion should have started.
You may want to take a look at http://exoplanet.eu/, which has information on exoplanets.