Max Planck Institute for Astronomy - Annual Report 2005

126 V. People and Events
Fig. V.8.2: Sebastian Wolf during his talk on protoplanetary
disks. (Photo: DFG)
young stars to be traced in three spatial dimensions.
These simulations enable predictions of observational
quantities that reflect the growth of dust to planetesimals
and later to planets, among other things. Such
observational quantities can be spectra, images, polarization
maps or interferometric data of circumstellar
disks. These predictions can be verified by observing
real stars.
One such prediction is, for instance, that young massive
planets can be detected by the warm, dense dust in
their immediate surroundings and by the gaps they leave
along their orbits in a gaseous disk around the star.
Observations of this kind will be made possible with the
Atacama Large Millimeter Array (alma) that is scheduled
to go into operation within the next few years in
the Chilean Atacama Desert. Within these simulations,
Wolf also investigated the questions as to how the appearance
of protoplanetary disks can be affected by variously
shaped dust grains, clumpy spatial distributions
of the dust, and the sizes and chemical compositions of
the dust particles.
Even now, observations of protoplanetary disks
allow little insight into the first steps of planet formation.
So with the aid of his simulations, Wolf was able
to make a breakthrough by demonstrating that within
a prominent protoplanetary disk – the one around the
»Butterfly Star« – the growth of dust grains proceeds
faster than in the circumstellar envelope of the same
object. The dust grains in the circumstellar disk are
already 100 to 1000 times bigger than those in the surrounding
thin envelope, which obviously still harbors
the original dust population. This result corroborates the
theoretical predictions and is based on high-resolution
images obtained in various wavebands with different
telescopes, e.g., the Hubble Space Telescope and the
Radio Observatory in Owens Valley, California.
It is customary at the presentation of the prizes that
one of the prizewinners – in 2005 there were six of them
– gives a scientific talk about his subject. It is considered
a special honor for Sebastian Wolf to have been
chosen for this task. His topic was: »Can we observe
planet formation?« This, too, proves the attractiveness
of astronomy on the general research scene.
Marie Curie Excellence Grant for Elena Masciadri
Elena Masciadri was hired at the MPIA at the time
of the feasibility study of the Planet finder, a sophisticated
second generation instrument for the VLT.
During her stay at the MPIA, she concentrated on two
topics. She supported the Planet finder project on the
instrumental side. In particular, she carried out a study
on the scintillation effects on this instrument, which
was fundamental to quantify these effects, to optimize
the conception of the Planet finder, and to define the
number of deformable mirrors needed to correct the
wavefront perturbations induced by the atmospheric
turbulence.
As her second area of work, she realized surveys for
searches for extrasolar planets and Brown Dwarfs orbiting
around nearby young stars, employing the direct
imaging technique. To do so, she used high-contrast
imaging techniques, taking advantage of the high-performance
infrared camera naco installed on one unit of
the VLT, in particular the new state-of-the-art SDI/naco.
This latter instrument is based on the simultaneous
differential imaging technique, with the double goal of
reducing the speckle noise at sub-arcsecond separations
and revealing methane-rich faint objects such as the
majority of the young and massive planets potentially
orbiting young (100 – 200 million years old) nearby
stars. It is therefore a technique that may greatly improve
our ability to detect faint objects with a contrast of 9
to 11 magnitudes in H at 0.5 seconds of arc separation
from the central star. This corresponds to planets having
masses on the order of 3 to 10 Jupiter masses and ages
of 1 to 200 million years.
These studies permitted her to strongly constrain the
planet formation models. Her interest was also directed
towards the conception of alternative techniques for
image processing, aiming at an automatic detection of
planets in deep imaging such as the wavelet technique,
and she investigated the possibilities of detecting outflows
from very low-mass stars and brown dwarfs. This
topic is particularly interesting because the detection of