ARE THE TWO BLACK HOLES OBSERVED BY LIGO PRODUCED FROM THE COLLAPSE OF A SINGLE STAR?

Image: Simulation of two colliding black holes. Animation created by SXS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org) - Caltech LIGO

If the GW signal observed by LIGO is due to the merger of two isolated black holes (BHs) in vacuum, no electromagnetic counterparts are expected. However, Fermi observed a signal 0.4 s after LIGO in a region of space compatible with the GW source.

A recent paper (Loeb 2016) suggests that the two black holes could be the result of the collapse of a single massive and rapidly rotating star. In this scenario the GRB is produced from a jet generated in the accretion disk of residual debris around the black hole or from an outflow generating by the BHs' merging.

The detection of a GRB afterglow in the future could be used to determine the precise localization of the electromagnetic source and eventually confirm the association to the GW source.

Loeb 2016 (accepted for publication in ApJ Letters) - Electromagnetic Counterparts to Black Hole Mergers Detected by LIGO (arXiv)

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CONTAMINATION BY SUPERNOVAE IN GLOBULAR CLUSTERS

Credit: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF) Only a small amount of the supernovae products remains trapped within globular clusters and this "catch" only occurs in the most massive cases (mass cluster ≥ 10^6 solar masses).

Fermi Bubbles

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.

Scientists detect comets outside our solar system

An artist’s conception of a view from within the Exocomet system KIC 3542116. Credit: Danielle Futselaar Team of professional and citizen scientists identifies tails of comets streaking past a distant star Jennifer Chu | MIT News Office Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets — comets outside our solar system — orbiting a faint star 800 light years from Earth. These cosmic balls of ice and dust, which were about the size of Halley’s Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system. The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star’s light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, ...

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