9 Second generation planets formed in-situ as first generation planets in their current position. However, these orbits are accessible for in-situ formation of second generation planets are the already evolved and much shorter period binary observed today. The globular cluster pulsar planet PSR B1620−26 (Backer et al. 1993) is another highly interesting second generation candidate. It is the only planet found in a globular cluster (metal poor environment) and it is a circumbinary planet around a WD-NS binary, found in the cluster outskirts of a globular cluster, as might be expected from our discussion above of second genera- tion planets in globular clusters (see section 3). Sev- eral studies suggested scenarios for the formation of this system and its unique and puzzling configuration (Sigurdsson & Thorsett 2005; Sigurdsson et al. 2008). These usually require highly fine tuned and complex dy- namical and evolutionary history. A second generation origin could give an alternative and more robust expla- nation [as also suggested by Livio & Pringle (2003) and studied by Beer et al. (2004)]. The high relative inclina- tion observed for this planets suggested that even in the second generation scenario some an encounter with an- other star is required to explain this system (Beer et al. 2004). However, recent studies show that high in- clinations could also occur from planet-planet scatter- ing in a multiple planet system (Chatterjee et al. 2008; Jurić & Tremaine 2008). Note that the existence of an- other planet in this system is highly unlikely for the favor- able formation scenarios discussed by Sigurdsson et al. (2008), but could be a natural consequence for the sec- ond generation scenario. This could motivate further observational study of this system. Similarly, findings of additional globular cluster planets preferably in WD binary systems would strongly support the second gener- ation scenario origin of globular cluster planets (see also Sigurdsson & Thorsett 2005). Other possibly weaker candidate second generation planets would be those planets found around metal poor stars (e.g. Santos et al. 2007). Finding a WD compan- ions for such stars, however, would give a strong support for the second generation scenario and the identification of these systems as second generation planets. We conclude that several second generation candidate planets have already been observed, and show proper- ties consistent with the scenario discussed in this pa- per. Moreover, the current properties of these systems may pose problems for our current (poor) understand- ing of first generation planets formation and evolution in evolved binary systems, which could be naturally solved in the context of second generation planets. Observed WD-MS binary systems (e.g. Rebassa-Mansergas et al. 2009) should therefore serve as potentially promising tar- gets for exo-planets searches. In this paper we suggested and discussed the formation of second generation planetary systems in mass transfer- ring binaries. We found that this is a possible route for planet formation in old evolved systems and around com- pact objects in double compact object binaries. We pre- sented possible implications for this process and the plan- etary systems it could produce, and detailed the possible observational signatures of second generation planetary systems. We also pointed out a few currently observed planetary systems with properties suggestive of a second generation origin. The possibility of second generation planets may open new horizons and suggest new approaches and targets for planetary searches and research. It suggests that stel- lar evolution processes and stellar deaths may serve as the cradle for the birth and/or rejuvenation of a new generation of planets, rather than just being the death throes or hostile hosts for pre-existing planets. In par- ticular such processes could provide new routes for the formation of habitable planets, opening the possibilities for their existence and discovery even in (the previously thought) less likely places to find them. The environ- ments of old stars and more so of compact objects could be very different from that of young stars. Such dif- ferent environments can strongly affect the formation of second generation planets and possibly introduce unique processes involved in their formation and evolution. The discovery and study of second generation planets could therefore shed new light on our understanding of both planet formation and binary evolution, and drive further research on the wide range of novel processes opened up by this possibility. I am most greatful to Scott Kenyon for many iluminat- ing discussions. I would also like to thank Scott Kenyon and Noam Soker for helpful comments on an earlier ver- sion of this manuscript. 8. CONCLUSIONS