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