A wide-orbit giant planet in the high-mass b Centauri binary system.

Planet formation occurs around a wide range of stellar masses and stellar system architectures1. An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly towards the extremes. Earlier studies of planets in close-in orbits around high-mass stars have revealed an increase in giant planet frequency with increasing stellar mass2 until a turnover point at 1.9 solar masses (M⊙), above which the frequency rapidly decreases3. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3 M⊙ may be rare or non-existent. However, the methods used to detect planets in small orbits are insensitive to planets in wide orbits. Here we demonstrate the existence of a planet at 560 times the Sun-Earth distance from the 6- to 10-M⊙ binary b Centauri through direct imaging. The planet-to-star mass ratio of 0.10-0.17% is similar to the Jupiter-Sun ratio, but the separation of the detected planet is about 100 times wider than that of Jupiter. Our results show that planets can reside in much more massive stellar systems than what would be expected from extrapolation of previous results. The planet is unlikely to have formed in situ through the conventional core accretion mechanism4, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability.

A measurement of the wind speed on a brown dwarf.

Zonal (latitudinal) winds dominate the bulk flow of planetary atmospheres. For gas giant planets such as Jupiter, the motion of clouds can be compared with radio emissions from the magnetosphere, which is connected to the planet's interior, to determine the wind speed. In principle, this technique can be applied to brown dwarfs and/or directly imaged exoplanets if periods can be determined for both the infrared and radio emissions. We apply this method to measure the wind speeds on the brown dwarf 2MASS J10475385+2124234. The difference between the radio period of 1.751 to 1.765 hours and infrared period of 1.741 ± 0.007 hours implies a strong wind (+650 ± 310 meters per second) proceeding eastward. This could be due to atmospheric jet streams and/or low frictional drag at the bottom of the atmosphere.

The UK Centre for Astrobiology: A Virtual Astrobiology Centre. Accomplishments and Lessons Learned, 2011-2016.

The UK Centre for Astrobiology (UKCA) was set up in 2011 as a virtual center to contribute to astrobiology research, education, and outreach. After 5 years, we describe this center and its work in each of these areas. Its research has focused on studying life in extreme environments, the limits of life on Earth, and implications for habitability elsewhere. Among its research infrastructure projects, UKCA has assembled an underground astrobiology laboratory that has hosted a deep subsurface planetary analog program, and it has developed new flow-through systems to study extraterrestrial aqueous environments. UKCA has used this research backdrop to develop education programs in astrobiology, including a massive open online course in astrobiology that has attracted over 120,000 students, a teacher training program, and an initiative to take astrobiology into prisons. In this paper, we review these activities and others with a particular focus on providing lessons to others who may consider setting up an astrobiology center, institute, or science facility. We discuss experience in integrating astrobiology research into teaching and education activities. Key Words: Astrobiology-Centre-Education-Subsurface-Analog research. Astrobiology 18, 224-243.

Synergy testing by Etest, microdilution checkerboard, and time-kill methods for pan-drug-resistant Acinetobacter baumannii.

Pan-drug-resistant (PDR) Acinetobacter baumannii is an important nosocomial pathogen that poses therapeutic challenges. Tigecycline alone or in combination with agents such as colestimethate, imipenem, and/or amikacin is being used clinically to treat PDR A. baumannii infections. The purpose of this study was to compare in vitro susceptibility testing by epsilometric (Etest) methods and the checkerboard (CB) method with testing by time-kill analysis. PDR A. baumannii clinical strains representing eight unique pulsed-field gel electrophoresis clones selected from a total of 32 isolates were tested in vitro with tigecycline, colestimethate, imipenem, and amikacin in single- and two-drug combinations by using two different methods of Etest (with a fixed ratio method [method 1] and with the incorporation of the active drug in medium [method 2]) and by using CB. The three-drug combination of imipenem, tigecycline, and amikacin was also tested by CB. These results were compared to time-kill results. Synergy was consistently detected with the imipenem plus colestimethate and tigecycline plus imipenem combinations. The Etest method with active drug incorporated into the agar allowed us to detect synergy even in the presence of the active drug and was more comparable to CB and time-kill tests. Synergy was detected with the three-drug combination of imipenem, tigecycline, and amikacin by both CB and time-kill methods among several tested clones. These findings indicate the utility of synergy testing to predict activity of specific antibiotic combinations against PDR A. baumannii.

A dynamical calibration of the mass-luminosity relation at very low stellar masses and young ages.

Mass is the most fundamental parameter of a star, yet it is also one of the most difficult to measure directly. In general, astronomers estimate stellar masses by determining the luminosity and using the 'mass-luminosity' relationship, but this relationship has never been accurately calibrated for young, low-mass stars and brown dwarfs. Masses for these low-mass objects are therefore constrained only by theoretical models. A new high-contrast adaptive optics camera enabled the discovery of a young (50 million years) companion only 0.156 arcseconds (2.3 au) from the more luminous (> 120 times brighter) star AB Doradus A. Here we report a dynamical determination of the mass of the newly resolved low-mass companion AB Dor C, whose mass is 0.090 +/- 0.005 solar masses. Given its measured 1-2-micrometre luminosity, we have found that the standard mass-luminosity relations overestimate the near-infrared luminosity of such objects by about a factor of approximately 2.5 at young ages. The young, cool objects hitherto thought to be substellar in mass are therefore about twice as massive, which means that the frequency of brown dwarfs and planetary mass objects in young stellar clusters has been overestimated.