[Baps] BU seminar 10/13 Wesley Traub (Jet Propulsion Laboratory) on Kepler exoplanets

[Paul Withers]

Speaker: Wesley Traub
Affiliation: Jet Propulsion Laboratory
Title: The Number of Terrestrial-Size, Habitable-Zone Planets as
Projected from Kepler Mission Transits

Date: Thursday, October 13, 2011
Time: 3:30 PM Refreshments in CAS 500, 4:00 PM Talk
Place: 725 Commonwealth Ave. CAS 502

Abstract:

Data from Kepler's first 136 days of operation are analyzed to determine
the distribution of exoplanets with respect to radius, period, and
host-star spectral type. The analysis is extrapolated to estimate the
percentage of terrestrial, habitable-zone exoplanets. The Kepler census
is assumed to be complete for bright stars (magnitude brighter than
14.0) having transiting planets of size greater than 0.5 Earth radius
and periods less than 42 days. It is also assumed that the size
distribution of planets is independent of orbital period, and that there
are no hidden biases in the data. Six significant statistical results
are found: there is a paucity of small planet detections around faint
target stars, probably an instrumental effect; the frequency of mid-size
planet detections is independent of whether the host star is bright or
faint; there are significantly fewer planets detected with periods less
than 3 days, compared to longer periods, almost certainly an
astrophysical effect; the frequency of all planets in the population
with periods less than 42 days is 29%, broken down as terrestrials 9%,
ice giants 18%, and gas giants 3%; the population has a planet frequency
with respect to period which follows a power-law relation dN/dln(P) =
A*P^\beta , with \beta = 0.71 +/- 0.08; and an extrapolation to longer
periods gives the frequency of terrestrial planets in the habitable
zones of FGK stars as eta-sub-Earth = 34 +/- 14%. Thus about one-third
of FGK stars are predicted to have at least one terrestrial,
habitable-zone planet.

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