Simulating the Last Moments Before Neutron Stars Merge

Volume rendering of density in a simulation of a binary neutron star merger. New research shows that neutrinos created in the hot interface between the merging stars can be briefly trapped and remain out of equilibrium with the cold cores of the merging stars for 2 to 3 milliseconds. Credit: David Radice/Penn State

When stars reach the end of their life cycle, they shed their outer layers in a supernova. What is left behind is a neutron star, a stellar remnant that is incredibly dense despite being relatively small and cold. When this happens in binary systems, the resulting neutron stars will eventually spiral inward and collide. When they finally merge, the process triggers the release of gravitational waves and can lead to the formation of a black hole. But what happens as the neutron stars begin merging, right down to the quantum level, is something scientists are eager to learn more about.

When the stars begin to merge, very high temperatures are generated, creating “hot neutrinos” that remain out of equilibrium with the cold cores of the merging stars. Ordinarily, these tiny, massless particles only interact with normal matter via weak nuclear forces and possibly gravity. However, according to new simulations led by Penn State University (PSU) physicists, these neutrinos can weakly interact with normal matter during this time. These findings could lead to new insights into these powerful events.

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More Evidence for the Gravitational Wave Background of the Universe

Pulsar timing array. Credit: David Champion/Max Planck

The gravitational wave background was first detected in 2016. It was announced following the release of the first data set from the European Pulsar Timing Array. A second set of data has just been released and, joined by the Indian Pulsar Timing Array, both studies confirm the existence of the background. The latest theory seems to suggest that we’re seeing the combined signal of supermassive black hole mergers. 

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Gravitational Lenses Could Pin Down Black Hole Mergers with Unprecedented Accuracy

Gravitational wave astronomy has been one of the hottest new types of astronomy ever since the LIGO consortium officially detected the first gravitational wave (GW) back in 2016. Astronomers were excited about the number of new questions that could be answered using this sensing technique that had never been considered before. But a lot of the nuance of the GWs that LIGO and other detectors have found in the 90 gravitational wave candidates they have found since 2016 is lost. 

Researchers have a hard time determining which galaxy a gravitational wave comes from. But now, a new paper from researchers in the Netherlands has a strategy and developed some simulations that could help narrow down the search for the birthplace of GWs. To do so, they use another darling of astronomers everywhere—gravitational lensing.

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Astronomers Will Get Gravitational Wave Alerts Within 30 Seconds

Astronomers and astrophysicists could use these alerts and information to understand how neutron stars behave and study nuclear interactions between neutron stars and black holes colliding.

Any event in the cosmos generates gravitational waves, the bigger the event, the more disturbance. Events where black holes and neutron stars collide can send out waves detectable here on Earth. It is possible that there can be an event in visible light when neutron stars collide so to take advantage of every opportunity an early warning is essential. The teams at LIGO-Virgo-KAGRA observatories are working on an alert system that will alert astronomers within 30 seconds fo a gravity wave event. If warning is early enough it may be possible to identify the source and watch the after glow. 

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Here’s Why We Should Put a Gravitational Wave Observatory on the Moon

Gravitational Wave science holds great potential that scientists are eager to develop. Is a gravitational wave observatory on the Moon the way forward? NASA/Goddard/LRO.

Scientists detected the first long-predicted gravitational wave in 2015, and since then, researchers have been hungering for better detectors. But the Earth is warm and seismically noisy, and that will always limit the effectiveness of Earth-based detectors.

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Gravitational Waves Could Show us the First Minute of the Universe

Primordial Gravitational Waves
Primordial Gravitational Waves

Astronomers routinely explore the universe using different wavelengths of the electromagnetic spectrum from the familiar visible light to radio waves and infra-red to gamma rays. There is a problem with studying the Universe through the electromagnetic spectrum, we can only see light from a time when the Universe was only 380,000 years old. An alternate approach is to use gravitational waves which are thought to have been present in the early Universe and may allow us to probe back even further. 

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The Echoes From Inflation Could Still Be Shaking the Cosmos Today

In the very early universe, physics was weird. A process known as “inflation,” where best we understand the universe went from a single infinitesimal point to everything we see today, was one such instance of that weird physics. Now, scientists from the Chinese Academy of Science have sifted through 15 years of pulsar timing data in order to put some constraints on what that physics looks like.

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Astronomers are Hoping to Detect Gravitational Waves Coming from Supernova 1987A

This Hubble Space Telescope image shows Supernova 1987A within the Large Magellanic Cloud, a neighboring galaxy to our Milky Way.
Hubble Space Telescope image of SN1987A in the Large Magellanic Cloud (Credit : NASA)

A supernova explosion is a cataclysmic explosion that marks the violent end of a massive star’s life. During the event, the star releases immense amounts of energy, often outshining the combined light from all the stars in the host galaxy for a very brief period of time. The explosion produces heavy elements and spreads them out among the stars to contribute to the formation of new stars and planets. The closest supernova in recent years occurred in the Large Magellanic Cloud in 1987 (SN1987A) and now, a team of astronomers have searched through mountains of data to see if they can detect gravitational waves from the remnant. 

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Next Generation Gravitational Wave Observatories Could Detect 100-600 Solar Mass Black Hole Mergers

Simulation of merging supermassive black holes. Credit: NASA's Goddard Space Flight Center/Scott Noble
Simulation of merging supermassive black holes. Credit: NASA's Goddard Space Flight Center/Scott Noble

Humans are born wonderers. We’re always wondering about the next valley over, the next horizon, what we’ll understand next about this vast Universe that we’re all wrapped up in.

In 2015, we finally detected our first long-awaited and long-theorized gravitational wave from the distant merger of two stellar mass black holes. But now we want to know more, and only better detectors can feed our appetite.

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A Kilonova Simulated in 3D

An artists impression of a kilonova, the moment where two neutron stars merge. Credit: Dana Berry, Skyworks Digital, Inc.

In 2017, astronomers detected gravitational waves from colliding neutron stars for the first time: a kilonova. Enormous amounts of heavy metals were detected in the light from the explosion, and astronomers continued to watch the expanding debris cloud.

Researchers have continued to study this event. Now, using a three-dimensional computer simulation, they have created a new recreation of this merger — second by second, as it happened — giving insights into all the high-energy mayhem and heavy elements formation in this catastrophic event.

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