Imagine driving through a small town containing modest-sized buildings and seeing a 100-story skyscraper. Astronomers found the equivalent monstrosity in space: a near-record supermassive black hole that weighs 17 billion suns and lives in a cosmic backwater community of a few galaxies. Until now, extremely massive black holes have been found at the cores of very large galaxies in regions of the universe packed with other large galaxies. This is not just coincidence. Like a cosmic Pac-Man, a monster black hole gobbles smaller black holes when two galaxies collide. This game of bumper cars is common in large galaxy clusters. In fact, the current black hole record holder tips the scale at 21 billion suns and resides in the crowded Coma galaxy cluster, located 330 million light-years away.
Controversial dark-matter claim faces ultimate test
Nature 532, 7597 (2016). http://www.nature.com/doifinder/10.1038/532014a
Author: Davide Castelvecchi
Multiple teams finally have the material they need to repeat enigmatic experiment.
Recent near-Earth supernovae probed by global deposition of interstellar radioactive 60Fe
Nature 532, 7597 (2016). doi:10.1038/nature17196
Authors: A. Wallner, J. Feige, N. Kinoshita, M. Paul, L. K. Fifield, R. Golser, M. Honda, U. Linnemann, H. Matsuzaki, S. Merchel, G. Rugel, S. G. Tims, P. Steier, T. Yamagata & S. R. Winkler
The rate of supernovae in our local Galactic neighbourhood within a distance of about 100 parsecs from Earth is estimated to be one every 2–4 million years, based on the total rate in the Milky Way (2.0 ± 0.7 per century). Recent massive-star and supernova activity in Earth’s vicinity may be traced by radionuclides with half-lives of up to 100 million years, if trapped in interstellar dust grains that penetrate the Solar System. One such radionuclide is 60Fe (with a half-life of 2.6 million years), which is ejected in supernova explosions and winds from massive stars. Here we report that the 60Fe signal observed previously in deep-sea crusts is global, extended in time and of interstellar origin from multiple events. We analysed deep-sea archives from all major oceans for 60Fe deposition via the accretion of interstellar dust particles. Our results reveal 60Fe interstellar influxes onto Earth at 1.5–3.2 million years ago and at 6.5–8.7 million years ago. The signal measured implies that a few per cent of fresh 60Fe was captured in dust and deposited on Earth. Our findings indicate multiple supernova and massive-star events during the last ten million years at distances of up to 100 parsecs.
The locations of recent supernovae near the Sun from modelling 60Fe transport
Nature 532, 7597 (2016). doi:10.1038/nature17424
Authors: D. Breitschwerdt, J. Feige, M. M. Schulreich, M. A. de. Avillez, C. Dettbarn & B. Fuchs
The signature of 60Fe in deep-sea crusts indicates that one or more supernovae exploded in the solar neighbourhood about 2.2 million years ago. Recent isotopic analysis is consistent with a core-collapse or electron-capture supernova that occurred 60 to 130 parsecs from the Sun. Moreover, peculiarities in the cosmic ray spectrum point to a nearby supernova about two million years ago. The Local Bubble of hot, diffuse plasma, in which the Solar System is embedded, originated from 14 to 20 supernovae within a moving group, whose surviving members are now in the Scorpius–Centaurus stellar association. Here we report calculations of the most probable trajectories and masses of the supernova progenitors, and hence their explosion times and sites. The 60Fe signal arises from two supernovae at distances between 90 and 100 parsecs. The closest occurred 2.3 million years ago at present-day galactic coordinates l = 327°, b = 11°, and the second-closest exploded about 1.5 million years ago at l = 343°, b = 25°, with masses of 9.2 and 8.8 times the solar mass, respectively. The remaining supernovae, which formed the Local Bubble, contribute to a smaller extent because they happened at larger distances and longer ago (60Fe has a half-life of 2.6 million years). There are uncertainties relating to the nucleosynthesis yields and the loss of 60Fe during transport, but they do not influence the relative distribution of 60Fe in the crust layers, and therefore our model reproduces the measured relative abundances very well.
Stellar astrophysics: Supernovae in the neighbourhood
Nature 532, 7597 (2016). doi:10.1038/532040a
Authors: Adrian L. Melott
Detailed measurements of radioisotopes in deep-sea deposits, plus modelling of how they reached Earth, indicate that many supernovae have occurred near enough to have potentially influenced evolution. See Letters p.69 & p.73
Astrophysics: Black-hole crackle-and-pop
Nature 532, 7597 (2016). doi:10.1038/532009f
Gravitational 'noise' could be easier to detect than previously thought.Gravitational waves were first observed in 2015 by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors (pictured). This demonstrated the existence of binary black holes and suggested that these are more abundant than
Astronomy: White dwarf's weird atmosphere
Nature 532, 7597 (2016). doi:10.1038/532008d
Astronomers have discovered a white dwarf star that has an atmosphere made almost entirely of oxygen — the first of its kind to be discovered.White dwarfs are the dense cores that get left behind when a relatively small star's nuclear fuel runs out and