On the thick‐disc exoplanet host subgiant HD 155358

The nearby subgiant HD 155358 has very recently been announced by Cochran et al. to harbour two Jovian‐mass planetary companions and to be the lowest metallicity exoplanet host star yet found. Here, we present a model atmosphere analysis and stellar evolutionary tracks for HD 155358, and demonstrate that it is actually a member of the ancient thick‐disc population of the Milky Way (τ≥ 12 Gyr). As such, HD 155358 is considerably rich in its α‐chain nuclei, and hence only about a factor of 2 below the solar abundance in terms of these species. Yet, as a precursor to the thin disc and residing on the metal‐poor end of the thin‐disc metal abundance distribution, HD 155358 gives way to the principal possibility that any star of the thin‐disc population of the Galaxy can be a potential exoplanet host. As opposed to this, the formation of planets and even planetary systems for HD 155358 and HD 37124 (another previously known thick‐disc exoplanet host) is mentionable, as there is strong evidence for a vigorous starburst phase in the early Milky Way, and secondly, the direct census of an unbiased nearby thick‐disc sample implies a minimum fraction of no less than 30 per cent multiple star systems ( N ≥ 3) to originate from that epoch.