In May 2023, shortly after the Laser Interferometer Gravitational-wave Observatory (LIGO) was restarted for its fourth series of observations, it detected a gravitational wave signal from the collision of an object, most likely a star neutron, with a presumed black hole having a mass 2.5 to 4.5 times greater than that of our Sun.
This signal, called GW230529, intrigues researchers because the mass of the candidate black hole falls within what is called a mass gap between the heaviest known neutron stars, which are a little more than two solar masses, and the lightest known black holes, which are about five solar masses. Although the gravitational wave signal alone cannot reveal the true nature of this object, future detections of similar events, particularly those accompanied by bursts of light, may hold the key to answering the question of whether how light black holes can be.
The image shows the coalescence and merger of a lower mass gap black hole (dark gray surface) with a neutron star (highly distorted by the black hole’s gravity). This still image from a merger simulation highlights only the low-density components of the neutron star, ranging from 60 grams per cubic centimeter (dark blue) to 600 kilograms per cubic centimeter (white). Its shape highlights the strong deformations of the low density material of the neutron star. Image credit: Ivan Markin, Tim Dietrich (University of Potsdam), Harald Paul Pfeiffer, Alessandra Buonanno (Max Planck Institute for Gravitational Physics)
“The latest findings demonstrate the impressive scientific capability of the gravitational wave detector array, which is significantly more sensitive than it was during the third observation period,” says Jenne Driggers (PhD ’15), detection scientist at LIGO Hanford in Washington. one of two facilities, along with LIGO Livingston in Louisiana, that make up the LIGO Observatory.
LIGO made history in 2015 after achieving the first direct detection of gravitational waves in space. Since then, LIGO and its partner detector in Europe, Virgo, have detected nearly 100 mergers between black holes, a handful between neutron stars, as well as mergers between neutron stars and black holes. The Japanese KAGRA detector joined the gravitational wave network in 2019, and the team of scientists collectively analyzing data from the three detectors is known as the LIGO-Virgo-KAGRA (LVK) collaboration. The LIGO observatories are funded by the National Science Foundation (NSF) and were designed, built and operated by Caltech and MIT.
The latest findings also indicate that collisions involving light black holes may be more common than previously thought.
“This detection, the first of our exciting results from the fourth LIGO-Virgo-KAGRA observation campaign, reveals that there may be a higher rate of similar collisions between neutron stars and low-mass black holes than We didn’t think so before,” says Jess McIver. assistant professor at the University of British Columbia, deputy spokesperson for the LIGO Scientific Collaboration, and former postdoctoral fellow at Caltech.
Prior to the GW230529 event, another intriguing mass-gap candidate object had been identified. During this event, which occurred in August 2019 and known as GW190814, a compact object of 2.6 solar masses was found as part of a cosmic collision, but scientists do not know if it was acted like a neutron star or a black hole.
After a pause for maintenance and upgrades, the fourth detector observation campaign will resume on April 10, 2024 and continue until February 2025.
Written by Whitney Clavin
Source: Caltech
Originally published in The European Times.
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