“Are we alone?” is a question that has likely been with us since before recorded history. Over the aeons, we have discovered a variety of human communities on Earth that add richness to our civilisations. But in discovering also the universe beyond Earth, the question has become broader: Are we alone in the Universe? In this presentation, Dr. Cartledge discussed the current classification scheme for exoplanets (planets orbiting stars other than the Sun), separating the Mercurians (Mercury-like) from the Subterrans (smaller than Earth), the Terrans (Earth-like), the Superterrans (larger rocky planets), the Neptunians (Neptune-like ice giant planets), and the Jovians (Jupiter-like and larger gas giants).
He mentioned the biases in exoplanet detection techniques, explaining why we find some types more easily than others. He described what range of planet types we look for in terms of habitability, and why, both for location within the Galaxy and within a star system. Finally, he revealed 12 habitable planet candidates and discussed the prospects of discovering “another Earth” in the near future.