As we prepare to undertake the observational search for extrasolar terrestrial planets, theoretical modeling studies can help to prepare us for the likely diversity of the extrasolar terrestrial planets. This diversity may arise as a function of planetary system architecture and formation history, which results in a variety of initial planetary properties, as well as stellar, planetary and biological evolutionary processes. Modeling of the physical and chemical processes of the planetary environment, and their interaction with the parent star, allows us to understand the nature of the planetary characteristics that indicate habitability and life, and how these manifest in the planetary spectra. Here we present disk-averaged spectra of planets in our own solar system, and models of the Earth through several eons to understand the types of planetary characteristics that are likely to be observed by planned planet detection and characterization missions.

This communication is devoted to data processing of images obtained using an extreme adaptive optics (AO) system and a coronagraph. Specific attention is given to the following degrading factors: the residuals of atmospheric turbulence after AO correction and the “side” effects of the coronagraph. Relying on a statistical modeling of the measurements a test based on short exposure images is proposed. This processing, which generalizes the dark-speckle technique, takes into account the “local” variance of the complex amplitude residuals and the deterministic response of the system (i.e. without atmospheric turbulence).

As the number of large scale ground- and space-bound planet detection and imaging projects is growing, the need for theoretical guidance in order to optimize instrumental design is rapidly mounting. In an effort to provide this required framework, we present the results of Monte Carlo simulations of the formation of giant planets and compare them with the current population of exoplanets. Our models show that due to the severe current observational detection bias only a small percentage (3.6 %) of the potentially existing planets can be detected. Indeed, a large number of planetary embryos never grow enough to become giant planets giving raise to a large populations of bodies with masses smaller than ${\simeq} 5 M_{\hbox{\it \scriptsize jup}}$. In addition, this observational bias, coupled with the fact that systems enriched in heavy elements tend to form more massive planets, explains the currently observed correlation between stellar metallicity and likelihood to host planets. Finally, we show that the disk gas delivery rate during the late stages of formation actually determines the maximum planetary mass.

We present here a software for simulations of observations made with an Integral Field Spectrograph attached to an extreme adaptive optics system, with the main goal of simulating direct detection of extrasolar planets and to test the capabilities in detecting planets of an instrument based on IFS on large telescopes. This code, written for IDL, has been conceived within the CHEOPS project, a second generation “Planet Finder” instrument for ESO's VLT; but it has been extended to the case of various ELTs. Here we describe in detail the procedure adopted in order to simulate realistic values of speckle noise, Adaptive Optics corrections, specific instrumental features and the efficiency of a Simultaneous Differential Imaging technique to increase the signal of the planet.

Currently two planetary systems around pulsars are known - discovered by the pulse timing technique, an indirect method. These planets were a surprise and gave rise to diverse planet formation scenarios, some of them very different to the common planet formation models around solar type stars and thus physically very interesting. Furthermore, neutron star planets are not only interesting themselves but also to study properties of the poorly understood neutron stars. After a summary about the current state of pulsar planets and the theoretical formation models, we present our own direct-imaging search for thermal emission of neutron star planets using the VLT. The project sample includes the fascinating radio-quiet isolated neutron stars, which are some of the closest and probably youngest neutron stars we know. Companions around them can only be found by direct imaging. Detecting planets around neutron stars by direct imaging differs significantly from using this technique for other, e.g. solar type, stars. As great advantage there is no need to reject the starlight of the primary.

We describe the rationale and requirements for an integral-field spectrograph aboard NASA's Terrestrial Planet Finder Coronagraph.

We present new laboratory measurements of the intrinsic rejection performances in infrared (1.9 $\mu\,$m to 2.5 $\mu\,$m) for a prototype of Achromatic Interfero Coronagraph (AIC). We first recall basics about the AIC, then describe the prototype under consideration. We give detailed explanations about the experimental setup and the procedures followed to measure the rejection rate. We end up with a discussion of the results obtained.

We discuss the preliminary results of a survey of young ($<$300 Myr), close ($<$50 pc) stars with the Simultaneous Differential Extrasolar Planet Imager (SDI) implemented at the VLT and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 $\mu$m methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data. In our survey data, we achieved H band contrasts $>$25000 (5$\sigma \Delta$F1(1.575$\mu$m)$>$10 mag, $\Delta$H$>$11.5 mag for a T6 spectral type) at a separation of 0.5” from the primary star. With this degree of attenuation, we should be able to image (5$\sigma$ detection) a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We are currently completing our survey of young, nearby stars, with complete datasets for 35 stars in the southern sky (VLT) and 7 stars in the northern sky (MMT). We believe that our SDI images are the highest contrast astronomical images ever made from ground or space for methane rich companions.

Our group at Princeton University is developing the Shaped-Pupil Coronagraph (SPC) as a solution to the high contrast imaging requirements for NASA's Terrestrial Planet Finder mission. At the heart of the SPC is a specially designed shaped mask at the pupil plane, and a star occulter at the image plane. We report a measurement of $10^{5}$ contrast at 4 $\lambda/D$ and $10^{6}$ at 7 $\lambda/D$, with no adaptive optics corrections. This contrast is maintained at laser wavelengths of 532, 594, and 632nm, and for broadband light from at least 550nm to 750nm. The contrast is almost certainly limited by wavefront aberrations in the mirrors. Indeed, the level and general structure of the speckles in the high contrast region is consistent with statistical simulations of our optics.

The Automated Patrol Telescope, operated by the University of New South Wales, has been undertaking a search for extrasolar planets using the transit method. We present lightcurves from two recent promising candidates; spectroscopic follow-up using the ANU 2.3m telescope shows that the companions are probably low mass stars rather than planets, although more data will be needed to be certain. Additionally, we outline future improvements to our transit search: a hardware upgrade scheduled for 2006, and the addition of a robust trend-filtering algorithm to the data reduction software.

Light reflected from planets is polarized. This basic property of planets provides the possibility for detecting and characterizing extra-solar planets using polarimetry. The expected polarization properties of extra-solar planets are discussed that can be inferred from polarimetry of “our” solar system planets. They show a large variety of characteristics depending on the atmospheric and/or surface properties. Best candidates for a polarimetric detection are extra-solar planets with an optically thick Rayleigh scattering layer.

Even the detection of highly polarized extra-solar planets requires a very sophisticated instrument. We present the results from a phase A (feasibility) study for a polarimetric arm in the ESO VLT planet finder instrument. It is shown that giant planets around nearby stars can be searched and investigated with an imaging polarimeter, combined with a powerful AO system and a coronagraph at an 8 m class telescope.

A similar type of polarimeter is also considered for the direct detection of terrestrial planets using an AO system on one of the future Extremely Large Telescopes.

Our activities are focused upon the experimental demonstration of deep nulling in the mid-IR over a wide bandpass. Specifically, our near-term goal is demonstrating a contrast of 10$^{-6}$ at 10 $\mu$m with a 25% spectral bandwidth. To meet this goal, several areas of technology development are required. These include: single-mode infrared fibers, bright infrared sources, laser path-length and tip/tilt metrology, and improvements to detection sensitivity. Progress in each of these areas of technical development will be reviewed as well as their impact on the overarching technical milestones.

We have recently deployed a four-quadrant phase-mask coronagraph behind an unobscured, circular, off-axis section of the Palomar 200-inch telescope. To obtain very good wavefront correction across the 1.5 m subaperture, our relay optics reimage the sub-aperture onto the adaptive optics system's deformable mirror. This approach combines the advantages of low diffraction from obscuring elements, due to the off-axis aperture, with high wavefront correction, due to the magnification of the pupil, and high stellar rejection, due to the phase mask coronagraph. Our initial on-sky results include Strehl ratios exceeding 90%, peak stellar rejections of >100:1, and an improvement in contrast of 235:1 on a binary of separation $2 \lambda /D$.

The Darwin and TPF-I missions are Infrared free flying interferometer missions based on nulling interferometry. Their main objective is to detect and characterize other Earth-like planets, analyze the composition of their atmospheres and their capability to sustain life, as we know it. Darwin and TPF-I are currently in study phase. A number of mission architectures of 3 and 4 free flying telescopes are evaluated on the basis of the interferometer's response, ability to distinguish multiple planet signatures and starlight rejection capabilities. The characteristics of the new configurations are compared also to the former, more complex Bowtie baseline architectures as well as evaluated on base of their science capability.

We present simulations which demonstrate to which extent mid-infrared images and millimeter maps can be used to trace the location of giant planets in circumstellar disks. The most promising approach is to look for characteristic signatures in circumstellar disks caused by the interaction of giant planets with the disk. Numerical simulations show that these signatures are usually in size much larger than the planet itself and thus much easier to detect. The particular result of the planet-disk-interaction depends on the evolutionary stage of the disk. Primary signatures of planets embedded in disks are gaps in the case of young disks and characteristic asymmetric density patterns in debris disks. Radiative transfer simulations predict that high spatial resolution observations performed with instruments/telescopes that will become available in the near future will allow to trace the formation and evolution of planets in protoplanetary and debris disks.

We investigate the problem of giant planet formation around stars with various masses based on the core accretion/gas capture model. At first, we follow the evolution of gas and solids from the moment when all solids are in the form of small grains to the stage when most of them have reached planetesimal size. We show that the surface density of a planetesimal swarm tends to be higher around less massive stars. Subsequently, we derive the minimum surface density of the planetesimal swarm required for the formation of giant planets, both in a numerical and in an approximate analytical approach. We combine these results by calculating a set of representative disk models, characterized by different masses, sizes, and metallicities. This allows us to quantify the probability of each individual disk model to form giant planets. Furthermore, we take the fact into account, that in some of these models, the outer regions of the disks become gravitationally unstable.

The search for extrasolar planets is nowadays one of the most promising science drivers in Astronomy. The radial velocity technique proved to be successful in planet hunting, harvesting more than a hundred planets to date. In these last recent years, the transit method has come to fruition, with the detection of seven Jupiter-mass extrasolar transiting planets in close-in orbits (${<}0.05$ AU). Currently, the radius of planets can only be determined from transiting planets, representing the principal motivation and strength of this technique. The MPIA is presently building the Large Area Imager (LAIWO) for the 1m telescope in the Wise Observatory, Israel. LAIWO will have a field of view of one square degree. An intensive search for extra-solar planets will be performed with the 1m Wise telescope, together with the 1.2m MONET telescope in Texas. We will monitor three fields at a given time during three years and more than 200 nights per year. We expect several dozens of extra-solar planets.

We are about to embark on a project to directly image low-mass companions orbiting within 1.5″ of their host stars. Our long-term aim is to reach down into the planetary-mass regime. In order to start this project we have time on the VLT NAOS/CONICA (NACO) facility and in the near future we plan to make use of the Near-Infrared Coronographic Imager (NICI) instrument mounted on Gemini-South. Our targets are F-M type dwarfs, and have been selected from the Anglo-Australian Planet Search (AAPS), Keck and Lick search lists. These surveys have been periodically monitoring over 1200 stars between them for the past $\sim$8 years with precisions typically around 3ms$^{-1}$. Our target list comprises objects which show significant evidence for companions on long-period orbits. Having a priori knowledge of companion characteristics allows us the advantage of prioritising our target list. Given the relatively high incidence of multiple planet systems found so far our search may also serve to provide useful constraints on any large separation, massive companions in our target systems.

High contrast imaging from space must overcome photon noise of the diffracted star light and scattered light from optical components defects. The very high contrast required (up to $10^{-10}$ for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. In this paper we present a closed loop correction method for the shaped pupil coronagraph to minimize the energy in a pre-defined region in the image where terrestrial planets would be found. The reconstruction part uses three intensity measurements in the image plane with a pinhole added to the shaped pupil for diversity. This method has been shown in simulations to be effective in the presence of photon noise, deformable mirror modeling errors and overcoming defective actuators in the deformable mirror.

A new approach to high contrast observations near bright stars with a single-aperture telescope is discussed, which is based on the idea of a rotating separated-aperture nulling interferometer. The approach can be described as a rotating sub-aperture nuller, because it nulls two or more sub-apertures within a single telescope's pupil, and uses baseline rotation to modulate the signals from off-axis sources in a manner similar to that of potential space-based nulling interferometers. The sub-aperture beams can be combined in a number of ways, including a fiber nuller and a rotational shearing interferometer. Such a rotating nulling coronagraph has two great advantages. First, it can be used on a ground-based telescope to test signal reconstruction approaches pertinent to potential space-based nulling interferometers. Moreover, it also has the potential to enable ground-based coronagraphic observations of faint off-axis companions very close to bright stars.