GeminiFocus 2014 Year in Review | Page 23

Figure 4. Kepler-186 was observed using the Differential Speckle Survey Instrument (DSSI) on Gemini North and using the NIRC2 camera on the Keck-II telescope. Gemini and Keck each imaged Kepler-186 to different degrees of proximity (to address how close to Kepler-186 another source could be resolved) and magnitude (to determine the faintest a nearby source could be detected). The exceptional data from DSSI allowed us to be sensitive to An Earth-sized planet crossing in front of a Sun-like star (left) and an M dwarf like Kepler-186 (right). The amount of starlight blocked by an Earth-sized planet in the habitable zone is proportionately greater for an M dwarf than a Sun-like star, creating a larger dip in the transit light curve (bottom) and therefore making them easier to detect. Credit: Wendy Stenzel M Dwarfs: Prime Targets in the Search for Habitable Worlds M dwarfs (stars with 0.1-0.5 times the mass of the Sun) are excellent targets in the search for habitable worlds. Planets in the habitable zones of M stars are easier to detect than planets in the habitable zones of Sun-like stars due to their shorter orbital periods and frequency of transits detected. The proportion of starlight that they block is also greater (see Figure 4) so the transit depths are deeper. M-dwarfs are also very abundant, comprising about three quarters of all main sequence stars in our galaxy. They also evolve very slowly in luminosity, thus their habitable zones remain stable for billions of years. Furthermore, planets around M dwarf hosts may (ultimately) be imaged more easily due to higher contrast between the planet and the star. M Dwarfs have long been thought to be unsuitable hosts for