Bright spots on Ceres could be active ice
Nature 519, 7544 (2015). http://www.nature.com/doifinder/10.1038/nature.2015.17139
Author: Alexandra Witze
Early data from Dawn spacecraft bring scientists closer to clearing up mystery about dwarf planet.
Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy
Nature 519, 7544 (2015). doi:10.1038/nature14261
Authors: F. Tombesi, M. Meléndez, S. Veilleux, J. N. Reeves, E. González-Alfonso & C. S. Reynolds
Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 1046 ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).
Galaxy formation: When the wind blows
Nature 519, 7544 (2015). doi:10.1038/519423a
Authors: James E. Geach
Astronomical observations of a luminous galaxy that has a central, mass-accreting supermassive black hole reveal how such entities launch and propel gas through galaxies at high speeds. See Letter p.436
Planetary science: Rings proposed for orbiting rock
Nature 519, 7544 (2015). doi:10.1038/519393a
An asteroid-sized rock orbiting between Saturn and Uranus may have a system of rings.Amanda Bosh of the Massachusetts Institute of Technology in Cambridge and her team observed the minor planet 2060 Chiron passing in front of a star, using NASA's Infrared Telescope Facility on
A dusty, normal galaxy in the epoch of reionization
Nature 519, 7543 (2015). doi:10.1038/nature14164
Authors: Darach Watson, Lise Christensen, Kirsten Kraiberg Knudsen, Johan Richard, Anna Gallazzi & Michał Jerzy Michałowski
Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z ≥ 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 ± 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7.
Five Solar System sights NASA should visit
Nature 519, 7543 (2015). http://www.nature.com/doifinder/10.1038/519274a
Author: Alexandra Witze
US planetary scientists dream up voyages of discovery, from Venus mappers to asteroid tours.