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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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LISA has Passed a key Review Phase, it’s Time to Actually Design the Final Mission

Any project manager will tell you that a phased review project system is the way to go.  Whether or not you agree with that statement, the process has been widely adopted by space exploration organizations across the globe. They form the basis of many of the best-known projects, and the completion of their phases are events to be celebrated by both the people working on them and the public at large. Now LISA, ESA’s attempt to build a 2.5 million kilometers long interferometer in space, has passed its Feasibility Phase, and is moving on to actually building some prototype technologies.

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Astronomers Could Detect Gravitational Waves by Tracking the Moon's Orbit Around the Earth

An artist view of primordial gravitational waves. Credit: Carl Knox, OzGrav/Swinburne University of Technology

Gravitational waves are notoriously difficult to detect. Although modern optical astronomy has been around for centuries, gravitational wave astronomy has only been around since 2015. Even now our ability to detect gravitational waves is limited. Observatories such as LIGO and Virgo can only detect powerful events such as the mergers of stellar black holes or neutron stars. And they can only detect waves with a narrow range of frequencies from tens of Hertz to a few hundred Hertz. Many gravitational waves are produced at much lower frequencies, but right now we can’t observe them. Imagine raising a telescope to the night sky and only being able to see light that is a few shades of purple.

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The Expanding Debris Cloud From the Kilonova Tells the Story of What Happens When Neutron Stars Collide

This artist’s conception illustrates the aftermath of a "kilonova," a powerful event that happens when two neutron stars merge. The object is called GW170817 and is the only cosmic event where both gravitational waves and electromagnetic radiation were detected. Image Credit: X-ray: NASA/CXC/Northwestern Univ./A. Hajela et al.; Illustration: NASA/CXC/M.Weiss

When two neutron stars collide, it creates a kilonova. The event causes both gravitational waves and emissions of electromagnetic energy. In 2017 the LIGO-Virgo gravitational-wave observatories detected a merger of two neutron stars about 130 million light-years away in the galaxy NGC 4993. The merger is called GW170817, and it remains the only cosmic event observed in both gravitational waves and electromagnetic radiation.

Astronomers have watched the expanding debris cloud from the kilonova for years. A clearer picture of what happens in the aftermath is emerging.

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A Highly Eccentric Black Hole Merger Detected for the First Time

Credit: RIT

In February 2016, scientists with the Laser Interferometer Gravitational-Wave Observatory (LIGO) confirmed the first-ever detection of a gravitational wave event. Originally predicted by Einstein’s Theory of General Relativity, GWs result from mergers between massive objects – like black holes, neutron stars, and supermassive black holes (SMBHs). Since 2016, dozens of events have been confirmed, opening a new window to the Universe and leading to a revolution in astronomy and cosmology.

In another first, a team of scientists led by the Center for Computational Relativity and Gravitation (CCRG) announced that they may have detected a merger of two black holes with eccentric orbits for the first time. According to the team’s paper, which recently appeared in Nature Astronomy, this potential discovery could explain why some of the black hole mergers detected by the LIGO Scientific Collaboration and the Virgo Collaboration are much heavier than previously expected.

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Astronomers Might Have Detected the Background Gravitational Waves of the Universe

Artistic impression of the Double Pulsar system, where two active pulsars orbit each other in just 147 min. The orbital motion of these extremely dense neutrons star causes a number of relativistic effects, including the creation of ripples in spacetime known as gravitational waves. The gravitational waves carry away energy from the systems which shrinks by about 7mm per days as a result. The corresponding measurement agrees with the prediction of general relativity within 0.013%. The picture at high resolution and two alternative versions (1b, 1c) are accessible in the left column. [less] © Michael Kramer/MPIfR

In February 2016, Gravitational Waves (GWs) were detected for the first time in history. This discovery confirmed a prediction made by Albert Einstein over a century ago and triggered a revolution in astronomy. Since then, dozens of GW events have been detected from various sources, ranging from black hole mergers, neutron star mergers, or a combination thereof. As the instruments used for GW astronomy become more sophisticated, the ability to detect more events (and learn more from them) will only increase.

For instance, an international team of astronomers recently detected a series of low-frequency gravitational waves using the International Pulsar Timing Array (IPTA). These waves, they determined, could be the early signs of a background gravitational wave signal (BGWS) caused by pairs of supermassive black holes. The existence of this background is something that astrophysicists have theorized since GWs were first detected, making this a potentially ground-breaking discovery!

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Gravitational Waves Reveal Surprising Secrets About Neutron Stars

The confirmation of gravitational waves back in 2017 continues to unlock whole new worlds of physics but also continues to elicit further questions.  The detection of each gravitational wave brings a new challenge – how to find out what caused the event.  Sometimes that is harder than it sounds.  Now a team led by Alejandro Vigna-Gomez of the University of Copenhagen thinks they found a model of star death that helps to explain some previously inexplicable findings – and points to a galaxy with many more massive neutron stars than previously thought.

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Next-Generation Gravitational Wave Observatories Could Detect the First Stars When They Exploded as Supernovae

From the Ashes of the First Stars
From the Ashes of the First Stars

The first stars to appear in the universe are no longer with us – they died long ago. But when they died they released torrents of gravitational waves, which might still be detectable as a faint hum in the background vibrations of the cosmos.

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On its Next run, LIGO Will be Able to Probe 8 Times as Much Space

Materials science has once again come through for space exploration.  Researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO) have developed a coating that could increase the sensitivity of LIGO by almost an order of magnitude.  That would increase the detection rate of the gravitational waves the observatory is seeking from about once a week to once a day, mainly due to the increased volume of space that the observatory’s interferometers would be able to collect signals from.

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A Gravitational Wave Observatory on the Moon Could "Hear" 70% of the Observable Universe

Concept for a Gravitational-wave Lunar Observatory for Cosmology (GLOC). Credit: Jani, et al

Gravitational-wave astronomy is set to revolutionize our understanding of the cosmos. In only a few years it has significantly enhanced our understanding of black holes, but it is still a scientific field in its youth. That means there are still serious limitations to what can be observed.

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