Gliese 581d: The First Potentially Habitable Water-World Discovered?

Abstract

Skulking in the shadows of nearby brighter stars lies the 581st member of the Wilhelm Gliese’s catalog of nearby dim stars. The catalog contains nearly 1,000 stars organized according to their position and stellar properties. Gliese 581 is a low mass, red dwarf star weighing in at a little under one third the mass of our Sun with a surface temperature of 3,200 °C. This little, unassuming star lies 20.3 light years from Earth. It’s a diminutive body of light and color, and its low content of metals suggests an age of 7 billion years or more. When the Sun formed, Gleise 581 had already settled down and was, by our standards, a mature star. Any instability in either the orbits of its progeny worlds or its surface would long since have ceased. Its planetary retinue circumnavigate their parent star in tight, nearly circular paths.