From Gl229B to HR8799bcd: 15 years of Direct Exoplanet Imaging Research

Christian Marois (Herzberg Institute of Astrophysics)

Almost 15 years ago the first unambiguous direct detection of a substellar object
around a star (Gl229B) was made. Several teams have since then pursued ambitious
adaptive optics surveys on large telescopes, but only several brown dwarfs and
a few possible candidate planets have been detected so far at generally
wide >100 AU separations. If those planet candidates are finally confirmed
as being bound and/or in the planetary mass regime, it is unlikely they have
formed in a disk like the planets of our solar system and are probably the result
of the binary star formation process. The essentially null result of these
surveys, in contrast with the very successful radial velocity searches <5 AU,
is suggesting that massive Jupiter-like planets are rare >20 AU around stars.
The year 2008 marks then end of this long drought with the direct detection of
planets around A-type stars. One of these discoveries, the HR8799 planetary
system made at the Gemini North telescope, is the first multi-planet system
portrait and also the first direct detection of thermal emission of confirmed
planets in orbit around a star. This system also shows strong evidences that
the three planets formed in a disk. I will briefly summarized the field history
and will described the important role that Gemini is playing in the quest
to image and characterize planets around other stars.