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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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Journal ArticleDOI

The Architecture of Exoplanets

TL;DR: The first radial velocity surveys showed that the occurrence rate increases with decreasing mass as discussed by the authors, which was put on a firm statistical basis with the Kepler mission that clearly demonstrated that there were more Neptune and Superearth-sized planets than Jupiter-sized ones.
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Direct Spectrum of the Benchmark T dwarf HD 19467 B

TL;DR: In this article, spectroscopy measurements of HD 19467 B were taken with the Project 1640 integral field unit at Palomar Observatory to confirm the cold nature of the companion and determine its spectral type.
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The Gemini NICI Planet-Finding Campaign: The Companion Detection Pipeline

TL;DR: In this article, the authors present the high-contrast image processing techniques used by the Gemini NICI Planet-Finding Campaign to detect faint companions to bright stars and compare their pipeline to the performance of the LOCI algorithm for NICI data and do not find significant improvement with LOCI.
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