The birth of massive galaxies, according to galaxy formation theories, begins with the buildup of a dense, compact core that is ablaze with the glow of millions of newly formed stars. Evidence of this early construction phase, however, has eluded astronomers until now. Astronomers identified a dense galactic core, dubbed "Sparky," using a combination of data from Hubble and Spitzer, other space telescopes, and the W.M. Keck Observatory in Hawaii. Hubble photographed the emerging galaxy as it looked 11 billion years ago, just 3 billion years after the birth of our universe in the big bang.
A massive galaxy in its core formation phase three billion years after the Big Bang
Nature 513, 7518 (2014). doi:10.1038/nature13616
Authors: Erica Nelson, Pieter van Dokkum, Marijn Franx, Gabriel Brammer, Ivelina Momcheva, Natascha Förster Schreiber, Elisabete da Cunha, Linda Tacconi, Rachel Bezanson, Allison Kirkpatrick, Joel Leja, Hans-Walter Rix, Rosalind Skelton, Arjen van der Wel, Katherine Whitaker & Stijn Wuyts
Most massive galaxies are thought to have formed their dense stellar cores in early cosmic epochs. Previous studies have found galaxies with high gas velocity dispersions or small apparent sizes, but so far no objects have been identified with both the stellar structure and the gas dynamics of a forming core. Here we report a candidate core in the process of formation 11 billion years ago, at redshift z = 2.3. This galaxy, GOODS-N-774, has a stellar mass of 100 billion solar masses, a half-light radius of 1.0 kiloparsecs and a star formation rate of solar masses per year. The star-forming gas has a velocity dispersion of 317 ± 30 kilometres per second. This is similar to the stellar velocity dispersions of the putative descendants of GOODS-N-774, which are compact quiescent galaxies at z ≈ 2 (refs 8, 9, 10, 11) and giant elliptical galaxies in the nearby Universe. Galaxies such as GOODS-N-774 seem to be rare; however, from the star formation rate and size of this galaxy we infer that many star-forming cores may be heavily obscured, and could be missed in optical and near-infrared surveys.
Astronomy: Collision history written in rock
Nature 512, 7515 (2014). doi:10.1038/512350c
Meteorites recovered in California have yielded details about their collision-filled journey from the Solar System's asteroid belt.The fragments (pictured) originated from a meteoroid whose fiery descent lit up the night sky over San Francisco in 2012. Peter Jenniskens of NASA's Ames Research
Astrobiology: Cosmic prestige
Nature 512, 7515 (2014). doi:10.1038/512368a
Author: Mario Livio
Mario Livio welcomes a lucid description of attempts to evaluate how special humans are.
Astrophysics: Supernova seen through γ-ray eyes
Nature 512, 7515 (2014). doi:10.1038/512375a
Authors: Robert P. Kirshner
Observations of γ-ray photons from a type Ia supernova indicate that stellar explosions of this kind get their energy from sudden thermonuclear fusion in the progenitor star. See Letter p.406
Neutrinos from the primary proton–proton fusion process in the Sun
Nature 512, 7515 (2014). doi:10.1038/nature13702
In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly
Neutrino physics: What makes the Sun shine
Nature 512, 7515 (2014). doi:10.1038/512378a
Authors: Wick Haxton
Neutrinos produced in the nuclear reaction that triggers solar-energy generation have been detected. This milestone in the search for solar neutrinos required a deep underground detector of exceptional sensitivity. See Article p.383
Cobalt-56 γ-ray emission lines from the type Ia supernova 2014J
Nature 512, 7515 (2014). doi:10.1038/nature13672
Authors: E. Churazov, R. Sunyaev, J. Isern, J. Knödlseder, P. Jean, F. Lebrun, N. Chugai, S. Grebenev, E. Bravo, S. Sazonov & M. Renaud
A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon–oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive 56Ni (refs 1–3). After the explosion, the decay chain from 56Ni to 56Co to 56Fe generates γ-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of 56Co lines at energies of 847 and 1,238 kiloelectronvolts and a γ-ray continuum in the 200–400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 ± 0.1 solar masses of radioactive 56Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometres per second. The observed γ-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of 56Ni.