SpaceTime

Image: Star-forming region in the Carina Nebula. Credit: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI/AURA) In a recent paper (Mesa-Delgado et al. 2016) [1] the authors report the first direct imaging of protoplanetary disks in the star-forming region of Carina, the most distant, massive cluster in which disks have been imaged.

Image: This computer-simulated image shows gas from a star that is ripped apart by tidal forces as it falls into a black hole. Credits: NASA, S. Gezari (The Johns Hopkins University), and J. Guillochon (University of California, Santa Cruz) When a star in a galactic nucleus is deflected too close to the central supermassive black hole (BH), it can be torn apart by tidal forces. During this tidal disruption event (TDE), roughly half of the stellar debris remains bound to the BH, while the other half is flung outwards and unbound from the system. The bound material, following a potentially complex process of debris circularization accretes onto the BH, creating a luminous flare lasting months to years.

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.