Hot Jupiters, Cool Neptunes, and Extrasolar Earths

I discuss three topics related to the search for extrasolar planets.
(1) I discuss the recent detection of a population of ``very hot
Jupiters,'' planets with periods P<3 days, in transit (TR) surveys for
extrasolar planets.  These detections are surprising, given that
radial velocity (RV) surveys have found a dearth of such planets,
despite the fact that their sensitivity increases with decreasing P.
I demonstrate that, when the selection biases of TR surveys and
small-number statistics are properly taken into account, the results
of RV and TR surveys are consistent and imply that the relative
frequency of very hot Jupiters to hot Jupiters (P>3d) is ~10-20%.
(2) I summarize the theory of, results from, and future prospects for
microlensing searches for extrasolar planets.  I demonstrate that,
within a few years, it should be possible to use microlensing to
constrain the frequency of companions at several AU with mass as small
as ~15 Earth masses to ~10%.  (3) Finally, I compare the prospects of
potential state-of-the-art experiments for detecting Earth-mass
planets around main-sequence stars using radial velocities, transits,
astrometry, and microlensing.  In particular, I show that unless
Earth-mass planets are very common or are packed much closer to their
parent stars than in the solar system, future searches using
transits, RV, and astrometry (as they are currently planned) may not
yield any reliable Earth-mass planet detections.  Further, even if all
stars have Earth-mass planets at periods of one year (and adopting
other optimistic assumptions as well), the combined yield of all four
techniques would be the detection of only about five such planets at
high S/N.