Colliding Neutron Stars can Generate Long Gamma-ray Bursts

Artist's illustration of a bright gamma-ray burst occurring in a star-forming region and beaming out energy into two narrow, oppositely directed jets. Image Credit: By NASA/Swift/Mary Pat Hrybyk-Keith and John Jones - http://imagine.gsfc.nasa.gov/docs/features/news/10sep08.html [1]Transferred from en.wikipedia to Commons by TheDJ using CommonsHelper., Public Domain, https://commons.wikimedia.org/w/index.php?curid=8807284

Gamma-Ray Bursts (GRBs) are the most energetic recurring events in the Universe. Only the Big Bang was more energetic, and it was a singularity. Astronomers see GRBs in distant Universes, and a lot of research has gone into understanding them and what causes them.

A new paper is upending some of what scientists thought they knew about these extraordinary explosions.

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How Artificial Intelligence Can Find the Source of Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are powerful flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes. In the explosion, two jets of very fast-moving material are ejected, as depicted in this artist’s illustration. If a jet happens to be aimed at Earth, we see a brief but powerful gamma-ray burst. Credit: ESO/A. Roquette

Gamma-ray bursts come in two main flavors, short and long. While astronomers believe that they understand what causes these two kinds of bursts, there is still significant overlap between them. A team of researchers have proposed a new way to classify gamma-ray bursts using the aid of machine learning algorithms. This new classification scheme will help astronomers better understand these enigmatic explosions.

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Gamma-ray Bursts Don’t Always Signal the Birth of a Black Hole, Sometimes It’s Just a New Neutron Star

gamma-ray burst from neutron star merger
Artist rendering of colliding neutron stars. Credit: Robin Dienel/Carnegie Institution for Science

Way out in the universe, a long time ago, a proto-magnetar was born. The birth was heralded by a gamma-ray burst (GRB), followed by a blast of strange emissions. Astronomers once assumed that GRBs like this came from black hole births. However, observations of the new object by astronomers in England show there’s more than one way to cause a GRB. And, there’s more than one type of GRB.

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Astronomers Just saw the Most Powerful Gamma-ray Burst Ever Recorded

Artist’s impression of a gamma-ray burst. Credit: ESO/A. Roquette

Gamma-ray bursts (GRBs) are one of the most mysterious transient phenomena facing astronomers today. These incredibly energetic bursts are the most powerful electromagnetic events observed since the Big Bang and can last from a few milliseconds to many hours. Whereas longer bursts are thought to occur during supernovae, when massive stars undergo gravitational collapse and shed their outer layer to become black holes, shorter events have also been recorded when massive binary objects (black holes and neutron stars) merge.

These bursts are characterized by an initial flash of gamma rays and a longer-lived “afterglow” typically emitted in X-ray, ultraviolet, radio, and other longer wavelengths. In the early-morning hours on October 14th, 2022, two independent teams of astronomers using the Gemini South telescope observed the aftermath of a GRB designated GRB221009A. Located 2.4 billion light-years away in the Sagitta constellation, this event was perhaps the closes and most powerful explosion ever recorded and was likely triggered by a supernova that gave birth to a black hole.

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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

gamma-ray burst from neutron star merger
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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