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See detailThe twofold debris disk around HD 113766 A. Warm and cold dust as seen with VLTI/MIDI and Herschel/PACS
Olofsson, Johan; Henning, Thomas; Nielbock, Markus et al

in Astronomy and Astrophysics (2013), 551

Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-IR. Around solar-type stars, very few objects show emission features in mid-IR ... [more ▼]

Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-IR. Around solar-type stars, very few objects show emission features in mid-IR spectroscopic observations, that are attributed to small, warm silicate dust grains. The origin of this warm dust can possibly be explained either by a collision between several bodies or by transport from an outer belt. Aims. We present and analyse new far-IR Herschel/Pacs observations, supplemented by ground-based data in the mid-IR (VLTI/Midi and VLT/Visir), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. Methods. We improve an existing model to account for these new observations, and better constrain the spatial distribution of the dust and its composition. Results. We underline the limitations of SED modelling and the need for spatially resolved observations. We find that the system is best described by an inner disk located within the first AU, well constrained by the Midi data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least a 8 years time span, in a environment subjected to strong radiation pressure. Conclusions. The time stability of the emission features indicates that µm-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub-µm-sized grains. We suggest that the emission features may arise from multi-composition aggregates. We discuss possible scenarios concerning the origin of the warm dust. The compactness of the innermost regions as probed by Midi, as well as the dust composition, suggest that we are witnessing the outcomes of (at least) one collision between partially differentiated bodies, in an environment possibly rendered unstable by terrestrial planetary formation. [less ▲]

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See detailThe Search for Worlds Like Our Own
Fridlund, Malcolm; Eiroa, Carlos; Henning, Thomas et al

in Astrobiology (2010), 10(1), 5-17

The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets -- particularly, their evolution, their atmospheres, and their ability to host life ... [more ▼]

The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets -- particularly, their evolution, their atmospheres, and their ability to host life -- constitute a significant problem. The quest for other worlds as abodes of life has been one of mankind's great questions for several millennia. For instance, as stated by Epicurus 300 BC: Other worlds, with plants and other living things, some of them similar and some of them different from ours, must exist. Demokritos from Abdera (460-370 BC), the man who invented the concept of indivisible small parts - atoms - also held the belief that other worlds exist around the stars and that some of these worlds may be inhabited by life-forms. The idea of the plurality of worlds and of life on them has since been held by scientists like Johannes Kepler and William Herschel, among many others. Here, one must also mention Giordano Bruno. Born in 1548, Bruno studied in France and came into contact with the teachings of Nicolas Copernicus. He wrote the book De l'Infinito, Universo e Mondi in 1584, in which he claimed that the Universe was infinite, that it contained an infinite amount of worlds like Earth, and that these worlds were inhabited by intelligent beings. At the time, this was extremely controversial, and eventually Bruno was arrested by the church and burned at the stake in Rome in 1600, as a heretic, for promoting this and other equally confrontational issues (though it is unclear exactly which idea was the one that ultimately brought him to his end). In all the aforementioned cases, the opinions and results were arrived at through reasoning--not by experiment. We have only recently acquired the technological capability to observe planets orbiting stars other than 6our Sun; acquisition of this capability has been a remarkable feat of our time. We show in this introduction to the Habitability Primer that mankind is at the dawning of an age when, by way of the scientific method and 21st-century technology, we will be able to answer this fascinating controversial issue that has persisted for at least 2500 years. [less ▲]

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See detailDarwin---an experimental astronomy mission to search for extrasolar planets
Cockell, Charles S; Herbst, Tom; Léger, Alain et al

in Experimental Astronomy (2009), 23

As a response to ESA call for mission concepts for its Cosmic Vision 2015--2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for ... [more ▼]

As a response to ESA call for mission concepts for its Cosmic Vision 2015--2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument. [less ▲]

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