ABSTRACT. As part of NASA's mission to explore habitable planets orbiting nearby stars, this article explores the detection and characterization capabilities of a 4 m space telescope plus 50 m starshade located at the Earth-Sun L2 point, known as the New Worlds Observer (NWO). Our calculations include the true spectral types and distribution of stars on the sky, an iterative target selection protocol designed to maximize efficiency based on prior detections, and realistic mission constraints. We conduct simulated observing runs for a wide range in exozodiacal background levels (ε ¼ 1-100 times the local zodi brightness) and overall prevalence of Earth-like terrestrial planets (η ⊕ ¼ 0:1-1). We find that even without any return visits, the NWO baseline architecture (IWA ¼ 65 mas, limiting FPB ¼ 4 × 10 À11 ) can achieve a 95% probability of detecting and spectrally characterizing at least one habitable Earth-like planet and an expectation value of ∼3 planets found, within the mission lifetime and ΔV budgets, even in the worst-case scenario (η ⊕ ¼ 0:1 and ε ¼ 100 zodis for every target). This achievement requires about 1 yr of integration time spread over the 5 yr mission, leaving the remainder of the telescope time for UV-NIR general astrophysics. Cost and technical feasibility considerations point to a "sweet spot" in starshade design near a 50 m starshade effective diameter, with 12 or 16 petals, at a distance of 70,000-100,000 km from the telescope.

The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5 layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wave front sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.

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We report here on a sample of resolved, infrared images of galaxies at z~0.5 taken with the 10-m Keck Telescope's Adaptive Optics (AO) system. We regularly achieve a spatial resolution of 0.05'' and are thus able to resolve both the disk and bulge components. We have extracted morphological information for ten galaxies and compared their properties to those of a local sample. The selection effects of both samples were explicitly taken into account in order to derive the unbiased result that disks at z~0.5 are ~0.6 mag arcsec^-2 brighter than, and about the same size as, local disks. The no-luminosity-evolution case is ruled out at 90% confidence. We also find, in a more qualitative analysis, that the bulges of these galaxies have undergone a smaller amount of surface brightness evolution and have also not changed significantly in size from z~0.5 to today. This is the first time this type of morphological evolution has been measured in the infrared and it points to the unique power of AO in exploring galaxy evolution.Comment: 27 pages, 7figures, 2 tables. Accepted for publication in the Astrophysical Journa