Marcy next, talking about the ηEarth survey with the Keck.
simulations, under certain assumptions, predict a “planet desert”
roughly for mass range 1-10 MEarth and 0.1-1 AU or so
can populate the desert with some fine tuning of migration parameters etc
but still noticeable deficiency of moderate mass planets
very assumption dependent
best tested through observations
cf Lin & Ida, and Mordasini et al.
But, as Mayor just said, there are loads of planets in that mass range in that orbital range…
Keck sample of 238 G/K/M main sequence stars, looking for 3-30 MEarth stars. Quiet, nearby, bright stars.
seeing lots o’planets, including multi-planet systems, and super-earths!
nice 4/sin(i) earth mass planet in ~ 4 day orbit around a K star (Howard et al in press)
41 detected planets around 27 stars, so far, out of 238 hosts observed
also have some candidates not robust enough yet to announce, some of which look very interesting and might become real planets real soon now
6 planets between 10 and 100 earth masses(/sin(i)), orbital period less than 20 days, out of 171 G and K hosts, should be fairly complete for this range – incompleteness quantified
4 more candidates not yet solid detections
incompleteness suggest 3-4 planets in this mass/period range have planets
- so, 5-8% of stars have planets in just this mass and period range
consistent with Mayor? hard to compare directly because of different mass and period ranges and systematic sample issues – but could be consistent
thing to do is to look at completeness of HARPS sample for the same range Keck has done completeness and see if statistics are consistent
maybe there are just more planets in the South
conclusion – details of formation models are lacking…
oh, how exactly – well, we don’t understand type I migration