Water is a hot topic in the study of exoplanets, including "hot Jupiters," whose masses are similar to that of Jupiter, but lie much closer to their parent star than Jupiter is to the sun. They are estimated to be a scorching 2,000 degrees Fahrenheit, meaning any water they host would take the form of water vapor.
Cold, clumpy accretion onto an active supermassive black hole
Nature 534, 7606 (2016). doi:10.1038/nature17969
Authors: Grant R. Tremblay, J. B. Raymond Oonk, Françoise Combes, Philippe Salomé, Christopher, P. O’Dea, Stefi A. Baum, G. Mark Voit, Megan Donahue, Brian R. McNamara, Timothy A. Davis, Michael A. McDonald, Alastair C. Edge, Tracy E. Clarke, Roberto Galván-Madrid, Malcolm N. Bremer, Louise O. V. Edwards, Andrew C. Fabian, Stephen Hamer, Yuan Li, Anaëlle Maury, Helen R. Russell, Alice C. Quillen, C. Megan Urry, Jeremy S. Sanders & Michael W. Wise
Supermassive black holes in galaxy centres can grow by the accretion of gas, liberating energy that might regulate star formation on galaxy-wide scales. The nature of the gaseous fuel reservoirs that power black hole growth is nevertheless largely unconstrained by observations, and is instead routinely simplified as a smooth, spherical inflow of very hot gas. Recent theory and simulations instead predict that accretion can be dominated by a stochastic, clumpy distribution of very cold molecular clouds—a departure from the ‘hot mode’ accretion model—although unambiguous observational support for this prediction remains elusive. Here we report observations that reveal a cold, clumpy accretion flow towards a supermassive black hole fuel reservoir in the nucleus of the Abell 2597 Brightest Cluster Galaxy (BCG), a nearby (redshift z = 0.0821) giant elliptical galaxy surrounded by a dense halo of hot plasma. Under the right conditions, thermal instabilities produce a rain of cold clouds that fall towards the galaxy’s centre, sustaining star formation amid a kiloparsec-scale molecular nebula that is found at its core. The observations show that these cold clouds also fuel black hole accretion, revealing ‘shadows’ cast by the molecular clouds as they move inward at about 300 kilometres per second towards the active supermassive black hole, which serves as a bright backlight. Corroborating evidence from prior observations of warmer atomic gas at extremely high spatial resolution, along with simple arguments based on geometry and probability, indicate that these clouds are within the innermost hundred parsecs of the black hole, and falling closer towards it.
Astrophysics: Relativity passes black-hole test
Nature 534, 7606 (2016). doi:10.1038/534154e
General relativity holds true, even under the extreme conditions of colliding black holes.In 2015, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) saw the first evidence of gravitational waves, which had been created by two merging black holes. Walter Del Pozzo at the University of
When astronomer Edwin Hubble discovered nearly 100 years ago that the universe was uniformly expanding in all directions, the finding was a big surprise. Then, in the mid-1990s, another shocker occurred: astronomers found that the expansion rate was accelerating perhaps due to a repulsive property called "dark energy." Now, the latest measurements of our runaway universe suggest that it is expanding faster than astronomers thought. The consequences could be very significant for our understanding of the shadowy contents of our unruly universe. It may mean that dark energy is shoving galaxies away from each other with even greater or growing strength. Or, the early cosmos may contain a new type of subatomic particle referred to as "dark radiation." A third possibility is that "dark matter," an invisible form of matter that makes up the bulk of our universe, possesses some weird, unexpected characteristics. Finally, Einstein's theory of gravity may be incomplete.
Astronomy: Cosmic detectives
Nature 534, 7605 (2016). doi:10.1038/534034a
Author: Bernie Fanaroff
Bernie Fanaroff surveys a study that probes telescopes in history and across the electromagnetic spectrum.
Astronomy: Galaxy from the cosmic dark ages
Nature 534, 7605 (2016). doi:10.1038/534008b
Astronomers have found the faintest example yet of a galaxy from the early Universe.Kuang-Han Huang of the University of California, Davis, and his colleagues spotted the 13-billion-year-old galaxy using the Keck Observatory in Hawaii and the Hubble Space Telescope. A cluster of galaxies in