  Aims: We study the formation of substellar objects (exoplanets and brown
dwarfs) as companions to young nearby stars. Methods: With high contrast AO
imaging obtained with NACO at ESO's VLT we search for faint
companion-candidates around our targets, whose companionship can be confirmed
with astrometry. Results: In the course of our imaging campaign we found a
faint substellar companion of the nearby pre-main sequence star PZ Tel, a
member of the beta Pic moving group. The companion is 5-6 mag fainter than its
host star in JHK and is located at a separation of only 0.3 arcsec (or 15 AU of
projected separation) north-east of PZ Tel. Within three NACO observing epochs
we could confirm common proper motion (>39 sigma) and detected orbital motion
of PZ Tel B around its primary (>37 sigma). The photometry of the newly found
companion is consistent with a brown dwarf with a mass of 24 to 40 MJup, at the
distance (50 pc) and age (8-20 Myr) of PZ Tel. The effective temperature of the
companion, derived from its photometry, ranges between 2500 and 2700 K, which
corresponds to a spectral type between M6 and M8. After beta Pic b, PZ Tel B is
the second closest substellar companion imaged directly around a young star.
