"Our study provides a new direction to understand the whole evolutionary history of massive stars toward the formation of black hole binaries."
At the beginning of the exoplanet age, the goals were fairly simple. The first was to find as many of them as possible to flesh out our understanding of the exoplanet population. The second was to determine if any were in the habitable zones around their stars. The definition of a habitable zone was necessarily simple in the beginning. Any planet in the right distance range from its star to allow liquid surface water was considered to be in the habitable zone.

