Nice article.

Never geard of AB doradus before.

The fact that thet have been able to see it indicates that it is hot enough to glow.

The question of how many free floating panets there are out there is quite apt. In a short abount of time most will cool to below detectability, particularly the H & He globules that formed in the early days of the galaxy.
Looks like this is a rather warm verion of the dark matter component of the galaxy.

In the disc the lifespan of an average planet will be relatively short as there is no emitted radiation & stellar wind to counteract condensation of mass from a giant molecular cloud. The result is that the average free floating planet may make only one or 2 orbits in the disc before being dumped on and emerging from the GMC as a brown dwarf or star in similar galactic orbit as it initially hit the GMC with.

Out of the galactic disc, the chances of a free foating planet being dumped on is extremely small as the relative velocities between the free flaoter and the GMC is large even if there is a direct hit, so the amount accreted is minute. The result is a lot of old cold free floaters & brown dwarves zipping about in the galactic halo adding to its stabilising mass.

Have a nice day: Ag