The loneliest planet: Riddle of world found floating through space without a star

An international team of astronomers has discovered a large planet floating freely through space with no star to orbit.

Planets traditionally travel in a uniform, singular direction, around a star. However, the free-floating planet, named PSO J318.5-22, has been found without a host.

Its movement isn’t structured, scientists do not understand how it formed and they are baffled by what – if anything – controls it.

PSO J318.5-22 was detected 80 lightyears away from Earth and it is estimated to have a mass six times that of Jupiter.

Astronomers believe it formed 12 million years ago, and is considered a newborn in planetary terms – Earth is thought to be around 4.5 billion years old.

Dr Michael Liu of the Institute for Astronomy at the University of Hawaii identified the rogue planet from its ‘faint and unique heat signature’.

….‘We have never before seen an object free-floating in space that that looks like this.

‘It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,’ explained Liu.

‘I had often wondered if such solitary objects exist, and now we know they do.’

Read more: http://www.dailymail.co.uk/sciencetech/article-2452217/A-lonely-planet-Giant-gas-world-sun-orbit-floating-space.html

Well you see because it’s so young it has not had time to be gravitationally captured by a larger body such as a star.

But I think someone should explain to the laymen how planets are born and why they have different ages.
I haven’t got time right now.

“The object was discovered in 2013 in images taken by the Pan-STARRS PS1 wide-field telescope.” “Pan-STARRS is primarily sensitive to visible light, though observations can be extended slightly into the infrared passbands. … The excellent near-infrared response of the Pan-STARRS detectors means that we can also make use of a y-band filter (1.0 microns).”

1.0 microns is barely a long enough wavelength to spot a free planet. A free planet of any great age (greater than 1% of the age of the universe) will always have a spectral type “Y”, as opposed to brown dwarfs which can have spectral types M, L, T or Y depending on age and mass. The WISE satellite performed an all-sky astronomical survey with images in 3.4, 4.6, 12 and 22 micron wavelength range bands. Y dwarfs shine brightest in 12 and 4.6 microns and are barely visible at 3.4 and shorter wavelengths. So Pan-STARRS couldn’t have seen it.

Ah, now I understand.

Because PSO J318.5-22 is co-moving with the star Beta Pictoris and because Beta Pictoris is a mere 12 million years old, it is inferred that PSO J318.5-22 is also 12 million years old. At that incredibly young age a free planet will have spectral type “L”, which Pan-STARRS could have and must have seen.

… and it wouldn’t have been specifically noted in earlier surveys such as 2MASS and WISE because without any knowledge of age it would have been dismissed as another relatively hot brown dwarf. Only when its proper motion was matched to that of Beta Pictoris would its extremely young age and therefore planetary nature have been discovered.