Ground based astrometry has not been very successful in detecting extrasolar planets. Some reasons are the relatively long time baselines required and instrumental stability requirements. Also, the number of free parameters is large compared to other methods (such as Doppler spectroscopy) and additional information is often required to constrain the true nature of the candidate signals. An example is the recently announced astrometric detection of a planet around the low mass star VB 10, where a careful reanalysis of the astrometric data casts some doubts on the true nature of the announced low mass companion. The Carnegie Astrometric Planet Search Program (CAPS), is focused on the detection of gas giant exoplanets around nearby low mass stars. We show that accuracies at the level of 0.4 mas can be reached on time-scales of years with a 2.5 class meter telescope given a sufficiently stable and optimized camera (CAPScam-S). This accuracy enables the detection of Jupiter-sized planets around nearby cool stars providing at the same time, accurate measurements of their distances and spatial motion.

Planets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of giant planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more gas giant planets. Given the strong correlation of gas giant planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms giant planets. Recent work, however, implies that the formation of gas giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by gas giant protoplanets leads to strong enrichments of heavy elements in their gaseous envelopes. Both scenarios also imply that gas giant planets should have significant solid cores, raising questions for gas giant interior models without cores. Exoplanets with large inferred core masses seem likely to have formed by core accretion, while gas giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoplanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of giant planets.

The discovery of decay products of a short-lived radioisotope (SLRI) in the Allende meteorite led to the hypothesis that a supernova shock wave transported freshly synthesized SLRI to the presolar dense cloud core, triggered its self-gravitational collapse, and injected the SLRI into the core. Previous multidimensional numerical calculations of the shock-cloud collision process showed that this hypothesis is plausible when the shock wave and dense cloud core are assumed to remain isothermal at similar to 10 K, but not when compressional heating to similar to 1000 K is assumed. Our two-dimensional models with the FLASH2.5 adaptive mesh refinement hydrodynamics code have shown that a 20 km s(-1) shock front can simultaneously trigger collapse of a 1 M-circle dot core and inject shock wave material, provided that cooling by molecular species such as H2O, CO, and H-2 is included. Here, we present the results for similar calculations with shock speeds ranging from 1 km s(-1) to 100 km s(-1). We find that shock speeds in the range from 5 km s(-1) to 70 km s(-1) are able to trigger the collapse of a 2.2 M-circle dot cloud while simultaneously injecting shock wave material: lower speed shocks do not achieve injection, while higher speed shocks do not trigger sustained collapse. The calculations continue to support the shock-wave trigger hypothesis for the formation of the solar system, though the injection efficiencies in the present models are lower than desired.

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (similar to 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

Five new planets orbiting G and K dwarfs have emerged from the Magellan velocity survey. These companions are Jovian-mass planets in eccentric (e >= 0.24) intermediate- and long-period orbits. HD 86226b orbits a solar metallicity G2 dwarf. The M-P sin i mass of the planet is 1.5 M-JUP, the semimajor axis is 2.6 AU, and the eccentricity is 0.73. HD 129445b orbits a metal-rich G6 dwarf. The minimum mass of the planet is M-P sin i = 1.6 M-JUP, the semimajor axis is 2.9 AU, and the eccentricity is 0.70. HD 164604b orbits a K2 dwarf. The M-P sin i mass is 2.7 M-JUP, the semimajor axis is 1.3 AU, and the eccentricity is 0.24. HD 175167b orbits a metal-rich G5 star. The MP sin i mass is 7.8 M-JUP, the semimajor axis is 2.4 AU, and the eccentricity is 0.54. HD 152079b orbits a G6 dwarf. The M-P sin i mass of the planet is 3M(JUP), the semimajor axis is 3.2 AU, and the eccentricity is 0.60.

The Kepler Mission, launched on 2009 March 6, was designed with the explicit capability to detect Earth-size planets in the habitable zone of solar-like stars using the transit photometry method. Results from just 43 days of data along with ground-based follow-up observations have identified five new transiting planets with measurements of their masses, radii, and orbital periods. Many aspects of stellar astrophysics also benefit from the unique, precise, extended, and nearly continuous data set for a large number and variety of stars. Early results for classical variables and eclipsing stars show great promise. To fully understand the methodology, processes, and eventually the results from the mission, we present the underlying rationale that ultimately led to the flight and ground system designs used to achieve the exquisite photometric performance. As an example of the initial photometric results, we present variability measurements that can be used to distinguish dwarf stars from red giants.

The short-lived radioisotope (SLRI) (60)Fe requires production in a core collapse supernova or asymptotic giant branch (AGB) star immediately before its incorporation into the earliest solar system solids. Shock waves from a somewhat distant supernova, or a relatively nearby AGB star, have the right speeds to simultaneously trigger the collapse of a dense molecular cloud core and to inject shock wave material into the resulting protostar. A new set of FLASH2.5 adaptive mesh refinement hydrodynamic models shows that the injection efficiency depends sensitively on the assumed shock thickness and density. Supernova shock waves appear to be thin enough to inject the amount of shock wave material necessary to match the SLRI abundances measured for primitive meteorites. Planetary nebula shock waves from AGB stars, however, appear to be too thick to achieve the required injection efficiencies. These models imply that a supernova pulled the trigger that led to the formation of our solar system.

We report the discovery of a tight substellar companion to the young solar analog PZ Tel, a member of the beta Pic moving group observed with high-contrast adaptive optics imaging as part of the Gemini Near-Infrared Coronagraphic Imager Planet-Finding Campaign. The companion was detected at a projected separation of 16.4 +/- 1.0 AU (0.'' 33 +/- 0.'' 01) in 2009 April. Second-epoch observations in 2010 May demonstrate that the companion is physically associated and shows significant orbital motion. Monte Carlo modeling constrains the orbit of PZ Tel B to eccentricities >0.6. The near-IR colors of PZ Tel B indicate a spectral type of M7 +/- 2 and thus this object will be a new benchmark companion for studies of ultracool, low-gravity photospheres. Adopting an age of 12(-4)(+8) Myr for the system, we estimate a mass of 36 +/- 6 M-Jup based on the Lyon/DUSTY evolutionary models. PZ Tel B is one of the few young substellar companions directly imaged at orbital separations similar to those of giant planets in our own solar system. Additionally, the primary star PZ Tel A shows a 70 mu m emission excess, evidence for a significant quantity of circumstellar dust that has not been disrupted by the orbital motion of the companion.

The Palomar High-precision Astrometric Search for Exoplanet Systems monitored 51 subarcsecond binary systems to evaluate whether tertiary companions as small as Jovian planets orbited either the primary or secondary stars, perturbing their otherwise smooth Keplerian motions. Six binaries are presented that show evidence of substellar companions orbiting either the primary or secondary star. Of these six systems, the likelihoods of two of the detected perturbations to represent real objects are considered to be "high confidence," while the remaining four systems are less certain and will require continued observations for confirmation.