195 research outputs found
The Habitable Exoplanet (HabEx) Imaging Mission: preliminary science drivers and technical requirements
HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astrophysics science. HabEx aims to fully characterize planetary systems around nearby solar-type stars for the first time, including rocky planets, possible water worlds, gas giants, ice giants, and faint circumstellar debris disks. In particular, it will explore our nearest neighbors and search for signs of habitability and biosignatures in the atmospheres of rocky planets in the habitable zones of their parent stars. Such high spatial resolution, high contrast observations require a large (roughly greater than 3.5m), stable, and diffraction-limited optical space telescope. Such a telescope also opens up unique capabilities for studying the formation and evolution of stars and galaxies. We present some preliminary science objectives identified for HabEx by our Science and Technology Definition Team (STDT), together with a first look at the key challenges and design trades ahead
Interférométrie spatiale dédiée à la recherche de planètes extrasolaires : Simulations des propriétés d'imagerie et de spectroscopie
Parmi les différentes techniques envisagées pour détecter et caractériser des planètes extrasolaires orbitant autour d'étoiles proches, l'interférométrie spatiale infrarouge est la seule qui permette une détection directe de planètes telluriques et le sondage de leur atmosphère par spectroscopie. Nous nous intéressons ici exclusivement à la pupille d'entrée d'un tel interféromètre, et à l'optimisation de ses propriétés d'imagerie et de spectroscopie. Apres avoir passé en revue les contraintes imposées par les principales sources de bruit astrophysique, nous proposons une configuration à 5 télescopes, répartis sur une base d'environ 50m sur 25m. Avec un tel réseau interférométrique, un temps d'intégration de 30h permettrait de reconstruire une "image" d'un système planétaire situé à 10pc et analogue au notre. La spectroscopie des planètes ainsi détectées pourrait révéler la présence de vapeur d'eau, de dioxyde de carbone, et d'ozone en quelques semaines d'intégration
Reflected spectroscopy of small exoplanets III: probing the UV band to measure biosignature gasses
Direct-imaging observations of terrestrial exoplanets will enable their
atmospheric characterization and habitability assessment. Considering the
Earth, the key atmospheric signatures for the biosphere is O and the
photochemical product O. However, this O-O biosignature is not
detectable in the visible wavelengths for most of the time after the emergence
of oxygenic photosynthesis life (i.e., the Proterozoic Earth). Here we
demonstrate spectroscopic observations in the ultraviolet wavelengths for
detecting and characterizing O and O in Proterozoic Earth-like planets,
using ExoReL. For an O mixing ratio 2 to 3 orders of magnitude less
than the present-day Earth, and an O mixing ratio of , we
find that O can be detected and its mixing ratio can be measured precisely
(within order of magnitude) in the ultraviolet (m) in
addition to visible-wavelength spectroscopy. With modest spectral resolution
() and S/N () in the ultraviolet, the O detection is robust
against other potential gases absorbing in the ultraviolet (e.g., HS and
SO), as well as the short-wavelength cutoff between 0.2 and 0.25 m.
While the O detection does not rely on the near-infrared spectra, extending
the wavelength coverage to the near-infrared (m) would provide
essential information to interpret the O biosignature, including the mixing
ratio of HO, the cloud pressure, as well as the determination of the
dominant gas of the atmosphere. The ultraviolet and near-infrared capabilities
should thus be evaluated as critical components for future missions aiming at
imaging and characterizing terrestrial exoplanets, such as the Habitable Worlds
Observatory.Comment: 13 pages, 8 figures, 3 tables, accepted for publication in A
Ring-apodized vortex coronagraphs for obscured telescopes. I. Transmissive ring apodizers
The vortex coronagraph (VC) is a new generation small inner working angle
(IWA) coronagraph currently offered on various 8-meter class ground-based
telescopes. On these observing platforms, the current level of performance is
not limited by the intrinsic properties of actual vortex devices, but by
wavefront control residuals and incoherent background (e.g. thermal emission of
the sky) or the light diffracted by the imprint of the secondary mirror and
support structures on the telescope pupil. In the particular case of unfriendly
apertures (mainly large central obscuration) when very high contrast is needed
(e.g. direct imaging of older exoplanets with extremely large telescopes or
space- based coronagraphs), a simple VC, as most coronagraphs, can not deliver
its nominal performance because of the contamination due to the diffraction
from the obscured part of the pupil. Here we propose a novel yet simple concept
that circumvents this problem. We combine a vortex phase mask in the image
plane of a high-contrast instrument with a single pupil-based amplitude ring
apodizer, tailor designed to exploit the unique convolution properties of the
VC at the Lyot-stop plane. We show that such a ring-apodized vortex coronagraph
(RAVC) restores the perfect attenuation property of the VC regardless of the
size of the central obscuration, and for any (even) topological charge of the
vortex. More importantly the RAVC maintains the IWA and conserves a fairly high
throughput, which are signature properties of the VC.Comment: 10 pages, 6 figure
White-Light Nulling Interferometers for Detecting Planets
A report proposes the development of a white-light nulling interferometer to be used in conjunction with a singleaperture astronomical telescope that would be operated in outer space. When such a telescope is aimed at a given star, the interferometer would suppress the light of that star while passing enough light from planets (if any) orbiting the star, to enable imaging or spectroscopic examination of the planets. In a nulling interferometer, according to the proposal, scattered light would be suppressed by spatial filtering in an array of single-mode optical fibers rather than by requiring optical surfaces to be accurate within 1/4,000 wavelength as in a coronagraph or an apodized telescope. As a result, angstrom-level precision would be needed in only the small nulling combiner, and not in large, meter-sized optics. The nulling interferometer could work as an independent instrument in space or in conjunction with a coronagraphic system to detect planets outside our solar system
The Habitable Exoplanet (HabEx) Imaging Mission: preliminary science drivers and technical requirements
HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astrophysics science. HabEx aims to fully characterize planetary systems around nearby solar-type stars for the first time, including rocky planets, possible water worlds, gas giants, ice giants, and faint circumstellar debris disks. In particular, it will explore our nearest neighbors and search for signs of habitability and biosignatures in the atmospheres of rocky planets in the habitable zones of their parent stars. Such high spatial resolution, high contrast observations require a large (roughly greater than 3.5m), stable, and diffraction-limited optical space telescope. Such a telescope also opens up unique capabilities for studying the formation and evolution of stars and galaxies. We present some preliminary science objectives identified for HabEx by our Science and Technology Definition Team (STDT), together with a first look at the key challenges and design trades ahead
Resolving the delta Andromedae spectroscopic binary with direct imaging
We present a direct image of the innermost companion to the red giant delta
Andromedae using the Stellar Double Coronagraph at the Palomar Observatory. We
use a Markov chain Monte Carlo based algorithm to simultaneously reduce the
data and perform astrometry and photometry of the companion. We determine that
the companion is most likely a main-sequence K-type star and is certainly not
the previously hypothesized white dwarf.Comment: ApJ, accepted. 10 pages, 3 figure
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