  Precision Doppler measurements from an intensive 48 night "Rocky Planet
Search" observing campaign on the Anglo-Australian Telescope (AAT) have
revealed the presence of a low-mass exoplanet orbiting the G1 dwarf HD16417.
Subsequent Doppler observations with the AAT, as well as independent
observations obtained by the Keck Planet Search, have confirmed this initial
detection and refine the orbital parameters to period 17.24+/-0.01 d,
eccentricity 0.20+/-0.09, orbital semi-major axis 0.14+/-0.01 AU and minimum
planet mass 22.1+/-2.0 Mearth. HD 16417 raises the number of published
exoplanets with minimum masses of less than 25 Mearth to eighteen.
Interestingly, the distribution of detected sub-25 Mearth planets over the
spectral types G, K and M is almost uniform. The detection of HD 16417b by an
intensive observing campaign clearly demonstrates the need for extended and
contiguous observing campaigns when aiming to detect low-amplitude Doppler
planets in short period orbits. Perhaps most critically it demonstrates that
the search for low-mass Doppler planets will eventually require these
traditional "bright-time" projects to extend throughout dark lunations.
