Laetitia Delrez

Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1

One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them—ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

Fast-evolving weather for the coolest of our two new substellar neighbours

We present the results of intense photometric monitoring in the near-infrared ( 0.9 m) with the TRAPPIST robotic telescope of the newly discovered binary brown dwarf WISE J104915.57-531906.1, the third closest system to the Sun at a distance of only 2 pc. Our twelve nights of time-series photometry reveal a quasi-periodic (P = 4:87 0:01h) variability with a maximum peak-peak amplitude of 11% and strong night-to-night evolution. We attribute this variability to the rotational modulation of fast-evolving weather patterns in the atmosphere of the coolest component ( T1-type) of the binary. No periodic signal is detected for the hottest component ( L8-type). For both brown dwarfs, our data allow us to firmly discard any unique transit during our observations for planets 2R . For orbital periods smaller than 9.5 h, transiting planets are excluded down to an Earth-size.

A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c

Three Earth-sized exoplanets were recently discovered close to the habitable zone of the nearby ultracool dwarf star TRAPPIST-1 (ref. 3). The nature of these planets has yet to be determined, as their masses remain unmeasured and no observational constraint is available for the planetary population surrounding ultracool dwarfs, of which the TRAPPIST-1 planets are the first transiting example. Theoretical predictions span the entire atmospheric range, from depleted to extended hydrogen-dominated atmospheres. Here we report observations of the combined transmission spectrum of the two inner planets during their simultaneous transits on 4 May 2016. The lack of features in the combined spectrum rules out cloud-free hydrogen-dominated atmospheres for each planet at ≥10σ levels; TRAPPIST-1 b and c are therefore unlikely to have an extended gas envelope as they occupy a region of parameter space in which high-altitude cloud/haze formation is not expected to be significant for hydrogen-dominated atmospheres. Many denser atmospheres remain consistent with the featureless transmission spectrum—from a cloud-free water-vapour atmosphere to a Venus-like one.

Hot Jupiters with relatives: discovery of additional planets in orbit around WASP-41 and WASP-47

We report the discovery of two additional planetary companions to WASP-41 and WASP-47. WASP-41 c is a planet of minimum mass 3.18

WASP-103 b: a new planet at the edge of tidal disruption

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High-frequency A-type pulsators discovered using SuperWASP

0.20 M

Three newly discovered sub-Jupiter-mass planets : WASP-69b and WASP-84b transit active K dwarfs and WASP-70Ab transits the evolved primary of a G4+K3 binary

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Transiting hot Jupiters from WASP-South, Euler and TRAPPIST : WASP-95b to WASP-101b

and eccentricity 0.29

TESTS OF THE PLANETARY HYPOTHESIS FOR PTFO 8-8695b

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