Re: Where did the 16 million year planetary age come from?
Is it concluded from the composition on the stars?
Identifying the age of stars and planets works by several techniques. A summary is presented at wikipedia, which includes the two techniques I wrote up in this reply before finding wiki's summary page. :)
One method is that you can look at a star's neighbor's for a rough idea. If the star's in a cluster, are there fresh, bright blue stars? Those don't live long, so if they're present the cluster and specific star is probably pretty young. The same goes for stars of other ages and colors - blue-white, white, and yellow stars may have lifespans less than that of the universe, so you can set bounds on the age of a cluster by their presence or absence. A cluster of only red dwarfs is probably old. Presence of absence of stellar remnants like white dwarfs or neutron stars is also somewhat indicative of age. Many clusters also scatter with time, so looking at the scatter of a cluster can give some ideas about age of cluster members.
There's a pretty strict relationship between stellar lifespan and stellar mass so if you get a good estimate of stellar mass - maybe the star has a companion or you have a good idea of its absolute luminosity - the door is opened to a lot of techniques for age estimation. For example, stars gradually brighten during their time on the main sequence (hydrogen burning stage of life), so knowing mass and brightness tells you the stars age. Similarly, "gyrochronology" just demonstrated the ability to estimate a star's age by its spin and mass: stars' spins slow down with age.
There are a few other features that help: protoplanetary disks don't last long, for example. If you see one, then it's a young system.
Planet ages would normally be estimated by the age of the star if you couldn't land a probe on the planet and do some radioactive dating like Apollo did for Luna. However, in this case the planet IS visible and several useful facts are known about it:
1) Its mass is 4 Jovian masses. That means it is not a brown dwarf and thus never had deuterium fusion in its core.
2) It's quite far from its bright primary, far enough that its would be Pluto cold
3) It's quite far from the pair of dwarf stars, far enough they add no supplemental heating
4) It's hot as hell
While the Kelvin-Helmholtz mechanism (energy release by gravitational contraction) flopped in attempting to explain the sun, it does give some idea about the age of a planet since the heat released drops with time. It helps to know the amount of sunlight falling on it (so you can subtract that and figure out just the K-H heat release) and the mass of the planet (so you can crunch the K-H equation). Knowing this planet's mass, distant orbit, and high temperature allows you to guess this planet is young and freshly formed, still radiating huge amounts of heat from its gravitational collapse.