Lonely ‘homeless’ planet found for the first time

These planetars stoke the scifi imagination. They are the perfect hideaway for a fleeing civilization... or deadly weapon. What kind of life could exist on a planet without a star?<p>Even when the scientific payoff is limited, the payoff to the imagination is immense.

Looks like it was detected in the infrared. The article is a bit light on detail, but on the face of it it's an absolutely astonishing achievement to detect a planet-sized body with an earth-based optical telescope.

Can someone explain to me how this would be termed a planet?<p>Doesn't the very definition of planet imply rotation around a star or other celestial object?<p>The BBC article is a little better: <a href="http://www.bbc.co.uk/news/science-environment-20309762" rel="nofollow">http://www.bbc.co.uk/news/science-environment-20309762</a> And it links to the actual paper: <a href="http://arxiv.org/abs/1210.0305" rel="nofollow">http://arxiv.org/abs/1210.0305</a>

I don't always read pop science, but when I do, I read thehindubusinessline.com. Also, the illustration paired with the article screams Melancholia.

If you read the article all the way towards the end, you will see that it's not exactly "lonely". From the article:<p><i>The planet is in fact called CFBDSIR2149 and appears to be part of a group of very young stars known as the AB Doradus Moving Group. “This group is unique in that it is made up of around thirty stars that all have the same age, have the same composition and that move together through space. It’s the link between the planet and AB Doradus that enabled us to deduce its age and classify it as a planet,” researcher Lison Malo explained. </i><p>I find it fascinating that we have identified a group of stars that are (i'm assuming) moving in synchronous towards a general direction. I can only theorize that it was caused by perhaps a giant supernova that flung all of these stars/planets outwards but it does make you wonder what caused it exactly.

It says that the image is a photo. Is that really so?<p>It says that the planet has a temperature of approx 400 degrees Celsius. That is hot. I would have expected it to be deadly cold, esp since it never managed to initiate nuclear reactions in its center. Why is that?

Given enough time, I wonder if this planet can gather enough gas and dust to turn into a star.

Would anyone like to explain why this planet would have a temperature of 400C (I was picturing it being really cold)? Is this because of its mass/size, more related to its gaseous composition or both?