Concentra (Star System)
Concentra is a star system first mentioned in The Lion in Paradise, where it's said to be "about a hundred, hundred and fifty light years thataway" from Devlin's Star.
The best candidate for Concentra is therefore HD 168443, also known as Omega Serpentis, a G8 III spectral type, at about 278 light years from Earth. The star is about 4 billion years old, weighs in at 1.2 solar masses, and has a luminosity 69 times that of Earth with a temperature of around 4800°K. It is over 10 solar radii in size, and is actually a "red clump" giant star. It is believed to be in the helium-burning stage of stellar evolution, and is unlikely to have any habitable planets unless they were already at great distances and have become habitable after the star expanded to its present size.
The life zone begins at about 8 AU, so any life-bearing planet is going to have a long-duration orbit. The orbit of a notional, rocky, 1M⊕-sized planet at 8AU, the bare inside boundary of the life zone, would be 20.6524 years. The life zone ends at about 14.5AU, where the same planet would take 50.3949 years to complete an orbit. See this CalcTool to calculate for other masses/distances.
Concentra was explored, claimed, and is thought to have been colonized in the late 21st century by an Earth consortium called the Concentra Group. As of 2249, very little is known about the colony presumably started there (even, for instance, if it's located on a planet, in an asteroid belt, in a space-borne habitat, or whatever). And frankly, nobody cares; they're all too busy with their own problems to worry about whether a colony in a way-off place like Concentra made it big, is barely hanging on, or failed horribly. Somebody will go out there in a hundred years or so and see. No rush.