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 expand upon the results of Close et al. 2005 regarding the young, low-mass object AB Dor C and its role as a calibration point for theoretical tracks. We argue for a new 70$\pm$30 Myr age estimate and present two additional detections of C with the Simultaneous Differential Imaging (SDI) camera. Our improved analysis (Nielsen et al. 2005) confirms our spectral type of M8 ($\pm$1) and mass of 0.090 $\pm$0.003 M$_{\hbox{\it \scriptsize sun}}$ for AB Dor C. However, Luhman & Potter (2006) argue for a hotter spectral type (M6$\pm$1). Here we adopt the consistent spectral range of M7$\pm$1 in this paper as a final spectral type. Plotting AB Dor C (and all other young (${<}0.12$ Myr), low-mass ($0.3-0.05 M_{\hbox{\it \scriptsize sun}}$) objects with accurate dynamical masses) on the HR diagram suggests a trend where current evolutionary models tend to over-predict the temperature (or under-predict the mass) for young low-mass stars and high-mass brown dwarfs. With our uncertainties, there is a $\sim$90% chance that the mass of AB Dor C is underestimated by the DUSTY tracks in the HR diagram.

We report preliminary results from our search for massive giant planets (6–12 Jupiter masses) around the known seven single white dwarfs in the Hyades cluster at sub-arcsec separations. At an age of 625 Myr, the white dwarfs had progenitor masses of about 3 solar masses, and massive gaseous giant planets should have formed in the massive circumstellar disks around these ex-Herbig A0 stars, probably at orbital separations similar or slightly larger than that of Jupiter. Such planets would have survived the post-Main-Sequence mass loss of the parent star and would have migrated outward adiabatically to orbital separations of about 25 AU. At the distance of the Hyades (45 pc) this corresponds to angular separations of about 0.5 arcsec which can be resolved with NICMOS/HST; the expected contrast in the J and H bands amount to 7.5 $\pm$ 1.5 mag.

Evaluation of our NICMOS data set did not reveal any evidence for planetary mass companions with masses down to about 10 Jupiter masses nor brown dwarfs around any of the seven white dwarfs for separations larger than 0.5 arcsec. However, we detected a low-mass, probably stellar, companion to a field white dwarf (WD1847-223J, distance $\sim$50 pc, age $\sim$1 Gyr; separation $\sim$0.5 arcsec, $\Delta$H $\sim$ 2.5 mag), using the NACO adaptive optics system at the VLT.

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.

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.

Neuhäuser et al. (2005a) presented evidence for a sub-stellar, common proper motion companion to GQ Lup, which is almost certainly a planet imaged directly, based on two independent mass estimates by means of theoretical models. The magnitude of GQ Lup b was determined by relative photometry compared to GQ Lup A. During a one-month monitoring of the primary star, we found is to be a variable with K= 6.9 to 7.3 mag (absolute photometry). Then, we re-observed GQ Lup A+b in May 2005, again with VLT/NACO. Due to the monitoring in April 2005, we could predict the exact K-band magnitude range of the primary during the new AO observation. Hence, we could determine a more precise error of the K-band magnitude of GQ Lup b by relative photometry compared to the primary. The new value is consistent with the previous estimate within the error margin, so that also the conclusions in Neuhäuser et al. (2005a,b) about its very low mass remain valid.

We discuss our numerical approach to the high-resolution modeling of the 3D structure and infrared emission of circumstellar dust disks. We examine the resonant structures of a dusty disk induced by the presence of giant planet, that outermost from a star. These features can serve as indicators of outermost planets embedded in the circumstellar dust disk and, moreover, can be used to determine its position, major orbital parameters and even the mass of the planet. Such planets are attractive goals for direct imaging. Our simulations indicate that Vega may have a massive planet $\sim$2 Jupiter mass at a distance ${>}50$ AU, and other giant planet(s) at a smaller distance, and Epsilon Eri may have a less massive planet $\sim$0.2 Jovian mass at a distance of 55–60 AU. Theoretical models and non-direct observations show that Beta Pictoris system can be a multiplanetary system with set of giant planets. Our dynamical model of the origin of the warping of the Beta Pictoris disk includes the gravitational influence of a planet with a mass of about 10 masses of Earth, at a distance of 70 AU, and a small inclination (2.5 deg) of the planetary orbit to the main dust disk. The direct signatures of this planet were discovered on 2002 by Keck observations.

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.

Discriminating exo-planetary photons from stellar photons with a ground-based instrument is a physically interesting and challenging issue. We propose an observational technique based upon both spectral and polarimetric coding to discriminate the exo-planetary photons. We also discuss a preliminary observation run performed with the spectrograph “CARELEC” on the 193 cm telescope at the Observatoire de Haute provence (OHP).

We discuss the evolution of the habitable zone around low mass and intermediate mass stars as they evolve off the main sequence. This work shows that this new class of stars should be included in the search for life because if planets could be found in their habitable zones, and these planets showed evidence for life, it is possible to empirically determine a lower limit to the timescale for the formation of life. This time scale is not well determined from the study of the Earth (or planets around main sequence stars), as life formation initially occurred during a period of heavy bombardment from comets and asteroids during the formation of the solar system. Our initial research was recently published (Lopez, Schneider, & Danchi 2005). We will describe our work in progress, in which we perform calculations and simulations aiming to demonstrate the potential of TPF and Darwin for the search and characterization of planets around evolved stars.

Superjupiters are much brigther when they are young and still contracting, and the contrast with the harboring stars is significantly more favorable for their detection. Within the JOVIAN (Jupiter-like Objects in the Visible and the Infrared: Astrophysical Nature) project, a search has been performed for superjupiters around nearby young stars using 4 m class telescopes. Here we summarize the results and present prospects for a future search around young and also relatively older nearby stars with the 10 m Gran Telescopio Canarias and the mid-infrared camera CanariCam.

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.

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 report 320 to 1020nm disk-averaged Earth reflectance spectra obtained from Moon's Earthshine observations with the EMMI spectrograph on the NTT at ESO La Silla (Chile). The spectral signatures of Earth atmosphere and ground vegetation are observed. A vegetation red-edge of up to 9% is observed on Europe and Africa and ${\approx}2%$ upon Pacific Ocean. The spectra also show that Earth is a blue planet when Rayleigh scattering dominates, or totally white when the cloud cover is large.

In order to evaluate and develop mission concepts for a search for Terrestrial Exoplanets, the European Space Agency has prepared a list of potential target systems. In this paper we present the criteria for selecting potential target stars suitable for the search for Earth like planets. We also establish the habitable zone for the stellar systems. Planets found within these zones would be potentially able to host complex life forms. The Darwin target star catalogue was created from the Hipparcos catalogue by examining the information on distance, spectral classification, multiplicity and stellar variability. Additional information on the targets stars including spectral type, metallicity, X-ray luminosity, rotation and Strömgren photometry from several other catalogues are included to determine the target star sample. Design constraints of the mission are added to derive a final target star catalogue of 262 target stars excluding and 447 target stars including M stars for the Darwin mission. We also discuss the completeness of sample for different classes of stars.

We discuss the evolution of the habitable zone around low mass and intermediate mass stars as they evolve off the main sequence. This work shows that this class of stars should be included in the search for life because if planets could be found in their habitable zones, they will allow to test different hypothesis concerning the conditions of life formation. For instance if these planets show traces for life, it is possible to empirically determine a lower limit to the timescale for the formation of life. This time scale is not well determined from the Earth's study, as life formation initially occurred during a period of heavy bombardment from comets and asteroids during the formation of the solar system. We will summarize (to the best of our knowledge) some of the recent results concerning the early signs of life on Earth. We will present some of our work in progress in which we evaluate the effects of stellar evolution on the habitable zone changes.

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 next generation of high-contrast imaging instruments will provide the first unresolved image of an extrasolar planet. While the emitted infrared light from the planet in thermal equilibrium should show almost no phase effect, the reflected visible light will vary with the orbital phase angle. We study the photometric variation of the reflected light with orbital phase of a ringed extrasolar planet. We show that a ring around an extrasolar planet, both obviously unresolved, can be detected by its specific photometric signature.

As high contrast imaging surveys are being designed and carried out to directly detect extrasolar planets around young, nearby stars it is important to carefully evaluate the criteria for selection of target stars, as well as the predicted success of such a survey based on the sensitivity of the AO system used. We have developed a routine to simulate a large number of planets around each potential target star, and determine what fraction can be reliably (5$\sigma$) detected using an AO system's predicted or observed sensitivity curve (the maximum flux ratio between the parent star and a detectable planet as a function of projected radius). Each planet has a randomly assigned semi-major axis, mass, and eccentricity (following extrapolations of detected radial velocity planet power laws), as well as random viewing angles and orbital phase. The orbital parameters give a projected separation for each planet, while the mass is converted into a flux ratio in the appropriate bandpass of the detector using the models of Burrows et al. (2003); this allows the simulated planets to be directly evaluated against the system's sensitivity curve. Since this method requires basic parameters (age, distance, spectral type, apparent magnitude) for each target star, a target list can be constructed that maximizes the likelihood of detecting planets, or competing instrument designs can be evaluated with respect to their predicted success for a given survey. We are already employing this method to select targets for our Simultaneous Differential Imaging (SDI) surveys (Biller et al. 2004), now underway at telescopes in the northern (MMT) and southern hemispheres (VLT).

We use Monte Carlo techniques to estimate the results and character of the early TPF-C mission. Using 108 samples to represent the planets of interest, we compute the completeness of the first search observations of prioritized target stars with optimized exposure times that sum to one year total. Assuming simple observing protocols and decision rules for searching, verifying, and characterizing observations, and taking into account ranges of probabilities for confusion sources ($P_\mathrm{confusion}$) and the occurrence of planets of interest ($\eta$), we compute 105 samples of the TPF-C schedule and observational outcomes for the first year of exposure time. For example, for Earth-like planets on habitable-zone orbits, assuming no observing overheads or pointing restrictions, and for the values $P_\mathrm{confusion}=0.5$ and $\eta=0.1$, we find that a median 2.2 planets are found, verified, and characterized in one year of exposure time, with the 68 highest priority stars searched.