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Image: A rupture in the crust of a highly magnetized neutron star, shown here in an artist's rendering, can trigger high-energy eruptions. Fermi observations of these blasts include information on how the star's surface twists and vibrates, providing new insights into what lies beneath. Credits: NASA's Goddard Space Flight Center/S. Wiessinger Some of the most intriguing neutron stars are the magnetars: highly magnetised objects whose surface fields are inferred to be in excess of 10 14 G in some cases, and whose interior fields may reach 10 16 G. In contrast with many older, more predictable neutron stars, magnetars are volatile, alternating between quiescent states and highly energetic bursts and flares. Their most spectacular events are the giant flares, releasing over ~ 10 45 erg of energy in a very brief flash and decaying X-ray tail. The giant flares of magnetars are believed to be powered by colossal magnetic energy reservoirs. In a recent paper (Lan...

Image: In the most common type of gamma-ray burst, illustrated here, a dying massive star forms a black hole (left), which drives a particle jet into space. Light across the spectrum arises from hot gas near the black hole, collisions within the jet, and from the jet's interaction with its surroundings. Credit: NASA's Goddard Space Flight Center Astrophysical explosions and jets generate shock waves, which produce radiation. Their radiative properties are determined by the dissipation mechanism that sustains the velocity jump in the shock and by its ability to generate nonthermal particles. A recent paper (Beloborodov 2016) examines the mechanism of internal shocks in gamma-ray bursts (GRBs) that occur before the GRB jets become transparent to radiation. The approach and some of the results may also be of interest for other explosions, e.g. in novae or supernovae. Sub-photospheric shocks can produce neutrino emission and affect the observed photospheric radiation f...

Image: A Schematic Outline of the Cosmic History - Credit: NASA/WMAP Science Team The epoch of reionisation and the emergence of the universe from the cosmic dark ages is a subject of intense study in modern cosmology.

Picture: These images show the merger of two neutron stars simulated using a new supercomputer model. Redder colors indicate lower densities. Green and white ribbons and lines represent magnetic fields. The orbiting neutron stars rapidly lose energy by emitting gravitational waves and merge after about three orbits, or in less than 8 milliseconds. The merger amplifies and scrambles the merged magnetic field. A black hole forms and the magnetic field becomes more organized, eventually producing structures capable of supporting the jets that power short gamma-ray bursts. Credit: NASA/AEI/ZIB/M. Koppitz and L. Rezzolla The LIGO and Virgo Collaborations recently reported the first direct detection of a gravitational-wave (GW) signal and demonstrated that it was produced by the inspiral and coalescence of a binary black hole (BHBH) system.

Image: This annotated artist’s impression shows the Milky Way galaxy. The blue halo of material surrounding the galaxy indicates the expected distribution of the mysterious dark matter. Credit: ESO/L. Calçada In a recent paper (Huang et al. 2016) the rotation curve (RC) of the Milky Way out to ~100kpc has been constructed using ~16,000 primary red clump giants (PRCGs) in the outer disk selected from the LSS-GAC and the SDSS-III/APOGEE survey, combined with ~5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey.

Image: At left is a map of gamma rays with energies between 1 and 3.16 GeV detected in the galactic center by Fermi's LAT; red indicates the greatest number. Prominent pulsars are labeled. Removing all known gamma-ray sources (right) reveals excess emission that may arise from dark matter annihilations. Credits: T. Linden, Univ. of Chicago Observations by the Fermi-LAT have uncovered a bright, spherically symmetric excess surrounding the center of the Milky Way galaxy. The spectrum of the gamma-ray excess peaks sharply at an energy ~2 GeV, exhibiting a hard spectrum at lower energies, and falls off quickly above an energy ~5 GeV. The spectrum of the excess above ~10 GeV is potentially an important discriminator between different physical models for its origin.

Image: A giant gamma-ray structure was discovered in 2010 by processing Fermi all-sky data at energies from 1 to 10 billion electron volts, shown here. The dumbbell-shaped feature (center) emerges from the galactic center and extends 50 degrees north and south from the plane of the Milky Way, spanning the sky from the constellation Virgo to the constellation Grus. Credits: NASA/DOE/Fermi LAT/D. Finkbeiner et al. At a time when our earliest human ancestors mastered walking upright the heart of our Milky Way galaxy underwent a titanic eruption, driving gases and other material outward at 2 million miles per hour.