36 research outputs found
Probable detection of starlight reflected from the giant exoplanet orbiting tau Bootis
Giant planets orbiting stars other than the Sun are clearly detectable
through precise radial-velocity measurements of the orbital reflex motion of
the parent star. In the four years since the discovery of the companion to the
star 51 Peg, similar low-amplitude ``Doppler star wobbles'' have revealed the
presence of some 20 planets orbiting nearby solar-type stars. Several of these
newly-discovered planets are very close to their parent stars, in orbits with
periods of only a few days. Being an indirect technique, however, the
reflex-velocity method has little to say about the sizes or compositions of the
planets, and can only place lower limits on their masses. Here we report the
use of high-resolution optical spectroscopy to achieve a probable detection of
the Doppler-shifted signature of starlight reflected from one of these objects,
the giant exoplanet orbiting the star tau Bootis. Our data give the planet's
orbital inclination i=29 degrees, indicating that its mass is some 8 times that
of Jupiter, and suggest strongly that the planet has the size and reflectivity
expected for a gas-giant planet.Comment: 15 pages, 4 figures. (Fig 1 and equation for epsilon on p1 para 2
revised; changed from double to single spacing
Ultra-diffuse hydrothermal venting supports Fe-oxidizing bacteria and massive umber deposition at 5000 m off Hawaii
© International Society for Microbial Ecology, 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in The ISME Journal 5 (2011): 1748–1758, doi:10.1038/ismej.2011.48.A novel hydrothermal field has been discovered at the base of Lōihi Seamount, Hawaii, at 5000 mbsl. Geochemical analyses demonstrate that ‘FeMO Deep’, while only 0.2 °C above ambient seawater temperature, derives from a distal, ultra-diffuse hydrothermal source. FeMO Deep is expressed as regional seafloor seepage of gelatinous iron- and silica-rich deposits, pooling between and over basalt pillows, in places over a meter thick. The system is capped by mm to cm thick hydrothermally derived iron-oxyhydroxide- and manganese-oxide-layered crusts. We use molecular analyses (16S rDNA-based) of extant communities combined with fluorescent in situ hybridizations to demonstrate that FeMO Deep deposits contain living iron-oxidizing Zetaproteobacteria related to the recently isolated strain Mariprofundus ferroxydans. Bioenergetic calculations, based on in-situ electrochemical measurements and cell counts, indicate that reactions between iron and oxygen are important in supporting chemosynthesis in the mats, which we infer forms a trophic base of the mat ecosystem. We suggest that the biogenic FeMO Deep hydrothermal deposit represents a modern analog for one class of geological iron deposits known as ‘umbers’ (for example, Troodos ophilolites, Cyprus) because of striking similarities in size, setting and internal structures.Funding has been provided by the NSF
Microbial Observatories Program (KJE, DE, BT, HS and
CM), by the Gordon and Betty Moore Foundation (KJE),
the College of Letters, Arts, and Sciences at the University
of Southern California (KJE) and by the NASA Astrobiology
Institute (KJE, DE)
The quest for the solar g modes
Solar gravity modes (or g modes) -- oscillations of the solar interior for
which buoyancy acts as the restoring force -- have the potential to provide
unprecedented inference on the structure and dynamics of the solar core,
inference that is not possible with the well observed acoustic modes (or p
modes). The high amplitude of the g-mode eigenfunctions in the core and the
evanesence of the modes in the convection zone make the modes particularly
sensitive to the physical and dynamical conditions in the core. Owing to the
existence of the convection zone, the g modes have very low amplitudes at
photospheric levels, which makes the modes extremely hard to detect. In this
paper, we review the current state of play regarding attempts to detect g
modes. We review the theory of g modes, including theoretical estimation of the
g-mode frequencies, amplitudes and damping rates. Then we go on to discuss the
techniques that have been used to try to detect g modes. We review results in
the literature, and finish by looking to the future, and the potential advances
that can be made -- from both data and data-analysis perspectives -- to give
unambiguous detections of individual g modes. The review ends by concluding
that, at the time of writing, there is indeed a consensus amongst the authors
that there is currently no undisputed detection of solar g modes.Comment: 71 pages, 18 figures, accepted by Astronomy and Astrophysics Revie
Limits on active to sterile neutrino oscillations from disappearance searches in the MINOS, Daya Bay, and bugey-3 experiments
Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^2 2θμe are set over 6 orders of magnitude in the sterile mass-squared splitting Δm^2 41. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm^2 41 < 0.8 eV^2 at 95% CLs
Colonization of subsurface microbial observatories deployed in young ocean crust
Oceanic crust comprises the largest hydrogeologic reservoir on Earth, containing fluids in thermodynamic disequilibrium with the basaltic crust. Little is known about microbial ecosystems that inhabit this vast realm and exploit chemically favorable conditions for metabolic activities. Crustal samples recovered from ocean drilling operations are often compromised for microbiological assays, hampering efforts to resolve the extent and functioning of a subsurface biosphere. We report results from the first in situ experimental observatory systems that have been used to study subseafloor life. Experiments deployed for 4 years in young (3.5 Ma) basaltic crust on the eastern flank of the Juan de Fuca Ridge record a dynamic, post-drilling response of crustal microbial ecosystems to changing physical and chemical conditions. Twisted stalks exhibiting a biogenic iron oxyhydroxide signature coated the surface of mineral substrates in the observatories; these are biosignatures indicating colonization by iron oxidizing bacteria during an initial phase of cool, oxic, iron-rich conditions following observatory installation. Following thermal and chemical recovery to warmer, reducing conditions, the in situ microbial structure in the observatory shifted, becoming representative of natural conditions in regional crustal fluids. Firmicutes, metabolic potential of which is unknown but may involve N or S cycling, dominated the post-rebound bacterial community. The archaeal community exhibited an extremely low diversity. Our experiment documented in situ conditions within a natural hydrological system that can pervade over millennia, exemplifying the power of observatory experiments for exploring the subsurface basaltic biosphere, the largest but most poorly understood biotope on Earth