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Direct imaging of multiple planets orbiting the star HR 8799.

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TLDR
High-contrast observations with the Keck and Gemini telescopes have revealed three planets orbiting the star HR 8799, with projected separations of 24, 38, and 68 astronomical units.
Abstract
Direct imaging of exoplanetary systems is a powerful technique that can reveal Jupiter-like planets in wide orbits, can enable detailed characterization of planetary atmospheres, and is a key step toward imaging Earth-like planets. Imaging detections are challenging because of the combined effect of small angular separation and large luminosity contrast between a planet and its host star. High-contrast observations with the Keck and Gemini telescopes have revealed three planets orbiting the star HR 8799, with projected separations of 24, 38, and 68 astronomical units. Multi-epoch data show counter clockwise orbital motion for all three imaged planets. The low luminosity of the companions and the estimated age of the system imply planetary masses between 5 and 13 times that of Jupiter. This system resembles a scaled-up version of the outer portion of our solar system.

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Citations
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Circumstellar Debris Disks: Diagnosing the Unseen Perturber

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Theoretical seismic properties of pre-main sequence gamma Doradus pulsators

TL;DR: In this paper, the authors studied the differences between the asteroseismic behaviour of PMS and MS gamma Dor pulsators as predicted by the current theory of stellar evolution and stability.
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Detectability of giant planets in protoplanetary disks by CO emission lines

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Dynamical models to explain observations with SPHERE in planetary systems with double debris belts

C. Lazzoni, +82 more
TL;DR: In this article, the authors investigated the possibility of the presence of multiple double-belts in gaps between double belts and showed that the apparent lack of planets in gaps could be explained by a system of two or more planets possibly of low mass and on eccentric orbits whose sizes are below the present detection limits.
References
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