A Black Hole can Tear a Neutron Star Apart in Less Than 2 Seconds

Numerical simulation of a black hole-neutron star merger. Credit and ©: K. Hayashi (Kyoto University)

Almost seven years ago (September 14th, 2015), researchers at the Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves (GWs) for the first time. Their results were shared with the world six months later and earned the discovery team the Noble Prize in Physics the following year. Since then, a total of 90 signals have been observed that were created by binary systems of two black holes, two neutron stars, or one of each. This latter scenario presents some very interesting opportunities for astronomers.

If a merger involves a black hole and neutron star, the event will produce GWs and a serious light display! Using data collected from the three black hole-neutron star mergers we’ve detected so far, a team of astrophysicists from Japan and Germany was able to model the complete process of the collision of a black hole with a neutron star, which included everything from the final orbits of the binary to the merger and post-merger phase. Their results could help inform future surveys that are sensitive enough to study mergers and GW events in much greater detail.

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The Gamow Explorer Would be a new Gamma-ray Observatory to Search for the First Stars in the Universe… as They Explode

Gamma rays are useful for more than just turning unassuming scientists into green-skinned behemoths.  They can also shine a light on the deaths of some of the earliest stars in the universe.  More accurately, they are some of the light caused by the deaths of the earliest stars in the universe.  Now, a team of scientists led by Nicholas White of George Washington University, and formerly of NASA’s Goddard Space Flight Center, has proposed an observatory mission that would scan the sky for evidence of Gamma-ray bursts (GRBs) and use them to understand the early universe.

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Finally an Answer to why Gamma Rays are Coming From Seemingly Empty Space

The cosmic glow of the gamma ray background. Credit: NASA/DOE/Fermi LAT Collaboration

Gamma rays strike Earth from all directions of the sky. Our planet is bathed in a diffuse glow of high-energy photons. It doesn’t affect us much, and we don’t really notice it, because our atmosphere is very good at absorbing gamma rays. It’s so good that we didn’t notice cosmic gamma rays until the 1960s when gamma-ray detectors were launched into space to look for signs of atomic weapons tests. Even then, what we noticed were intense flashes of gamma rays known as gamma ray bursts.

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Astronomers Locate the Source of High-Energy Cosmic Rays

Artist's impression of a supernova. Credit: NASA

Roughly a century ago, scientists began to realize that some of the radiation we detect in Earth’s atmosphere is not local in origin. This eventually gave rise to the discovery of cosmic rays, high-energy protons and atomic nuclei that have been stripped of their electrons and accelerated to relativistic speeds (close to the speed of light). However, there are still several mysteries surrounding this strange (and potentially lethal) phenomenon.

This includes questions about their origins and how the main component of cosmic rays (protons) are accelerated to such high velocity. Thanks to new research led by the University of Nagoya, scientists have quantified the amount of cosmic rays produced in a supernova remnant for the first time. This research has helped resolve a 100-year mystery and is a major step towards determining precisely where cosmic rays come from.

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Exploding Material From a Gamma-ray Burst Scrambled Nearby Magnetic Fields

Artist’s impression of a gamma-ray burst shining through two young galaxies in the early Universe. Credit: ESO

A team of astronomers has found that giant, organized magnetic fields can help drive some of the most powerful explosions in the universe. But when all is said and done, the shock wave from that blast scrambles any magnetic fields in a matter of minutes.

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New Simulation Shows Exactly What’s Happening as Neutron Stars Merge

Artist rendering of colliding neutron stars. Credit: Robin Dienel/Carnegie Institution for Science

Neutron stars are the remnants of massive stars that explode as supernovae at the end of their fusion lives. They’re super-dense cores where all of the protons and electrons are crushed into neutrons by the overpowering gravity of the dead star. They’re the smallest and densest stellar objects, except for black holes, and possibly other arcane, hypothetical objects like quark stars.

When two neutron stars merge, we can detect the resulting gravitational waves. But some aspects of these mergers are poorly-understood. One question surrounds short-lived gamma-ray bursts from these mergers. Previous studies have shown that these bursts may come from the decay of heavy elements produced in a neutron star merger.

A new study strengthens our understanding of these complex mergers and introduces a model that explains the gamma rays.

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It Takes Two Stars to Make a Gamma Ray Burst

Artist’s impression of gamma-ray burst with orbiting binary star. Credit: University of Warwick/Mark Garlick

In 1967, NASA scientists noticed something they had never seen before coming from deep space. In what has come to be known as the “Vela Incident“, multiple satellites registered a Gamma-Ray Burst (GRB) that was so bright, it briefly outshined the entire galaxy. Given their awesome power and the short-lived nature, astronomers have been eager to determine how and why these bursts take place.

Decades of observation have led to the conclusion that these explosions occur when a massive star goes supernova, but astronomers were still unsure why it happened in some cases and not others. Thanks to new research by a team from the University of Warwick, it appears that the key to producing GRBs lies with binary star systems – i.e. a star needs a companion in order to produce the brightest explosion in the Universe.

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Hubble Observes the Most Powerful Gamma Ray Burst Ever Detected

New observations from the NASA/ESA Hubble Space Telescope have investigated the nature of the powerful gamma-ray burst GRB 190114C by studying its environment. Gamma-ray bursts are the most powerful explosions in the Universe. They emit most of their energy in gamma rays, light which is much more energetic than the visible light we can see with our eyes. Hubble’s observations suggest that this particular burst displayed such powerful emission because the collapsing star was sitting in a very dense environment, right in the middle of a bright galaxy 5 billion light years away.

Gamma-ray bursts (GRBs) are one of the most energetic phenomena in the Universe, and also one of the least researched. These explosions of energy occur when a massive star goes supernova and emits twin beams of gamma rays that can be seen billions of light-years away. Because they are closely tied with the formation of black holes, scientists have been eager to study this rare occurrence in greater detail.

Unfortunately, few opportunities for this have occurred since GRBs are very short-lived (lasting for just seconds) and most have happened in distant galaxies. But thanks to the efforts using a suite of telescopes, astronomers were able to spot a GRB (designated GRB 190114C) back in January of 2019. Some of the radiation from this GRB was the highest energy ever observed, making this a milestone in the history of astronomy.

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Hubble Has Looked at the 2017 Kilonova Explosion Almost a Dozen Times, Watching it Slowly Fade Away

An artistic rendering of two neutron stars merging. Credit: NSF/LIGO/Sonoma State/A. Simonnet

In 2017, LIGO (Laser-Interferometer Gravitational Wave Observatory) and Virgo detected gravitational waves coming from the merger of two neutron stars. They named that signal GW170817. Two seconds after detecting it, NASA’s Fermi satellite detected a gamma ray burst (GRB) that was named GRB170817A. Within minutes, telescopes and observatories around the world honed in on the event.

The Hubble Space Telescope played a role in this historic detection of two neutron stars merging. Starting in December 2017, Hubble detected the visible light from this merger, and in the next year and a half it turned its powerful mirror on the same location over 10 times. The result?

The deepest image of the afterglow of this event, and one chock-full of scientific detail.

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Massive Triple Star System Creates this Bizarre Swirling Pinwheel of Dust. And it Could be the Site of a Gamma Ray Burst

The VISIR instrument on ESO’s VLT captured this stunning image of a newly-discovered massive binary star system. Nicknamed Apep after an ancient Egyptian deity, it could be the first gamma-ray burst progenitor to be found in our galaxy. Apep’s stellar winds have created the dust cloud surrounding the system, which consists of a binary star with a fainter companion. With 2 Wolf-Rayet stars orbiting each other in the binary, the serpentine swirls surrounding Apep are formed by the collision of two sets of powerful stellar winds, which create the spectacular dust plumes seen in the image. The reddish pinwheel in this image is data from the VISIR instrument on ESO’s Very Large Telescope (VLT), and shows the spectacular plumes of dust surrounding Apep. The blue sources at the centre of the image are a triple star system — which consists of a binary star system and a companion single star bound together by gravity. Though only two star-like objects are visible in the image, the lower source is in fact an unresolved binary Wolf-Rayet star. The triple star system was captured by the NACO adaptive optics instrument on the VLT. Credit: ESO/Callingham et al.

When stars reach the end of their lifespan, many undergo gravitational collapse and explode into a supernova, In some cases, they collapse to become black holes and release a tremendous amount of energy in a short amount of time. These are what is known as gamma-ray bursts (GRBs), and they are one of the most powerful events in the known Universe.

Recently, an international team of astronomers was able to capture an image  of a newly-discovered triple star system surrounded by a “pinwheel” of dust. This system, nicknamed “Apep”, is located roughly 8,000 light years from Earth and destined to become a long-duration GRB. In addition, it is the first of its kind to be discovered in our galaxy.

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