Gravitational waves could be generated by the debris fields of dying stars

A team of astrophysicists has determined through simulations that debris released by dying stars can be a source of gravitational wavesthose ripples in spacetime predicted by Einstein more than a century ago.

Gravitational waves are predicted by the theory of general relativity; they are ripples in spacetime generated by huge accelerating objects. The waves are also produced by the interactions of such objects, such as binaries and mergers between neutron stars and black holes.

Gravitational waves were first detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), which is based in Louisiana and Washington. LIGO detects gravitational waves by measuring tiny differences in the timing of laser pulses compared to mirrors in underground structures; these differences suggest that the ripples in spacetime delayed the laser pulses slightly.

Now, a team of researchers is suggesting that a new type of wave among those yet to be detected may be rippling through the cosmos: gravitational waves produced by matter emitted by dying stars. Their research was presented today at the 242nd meeting of the American Astronomical Society.

The evolution of a jet cocoon of dying stars, a possible source of gravitational waves.
gif: Gottlieb/CIERA/Northwestern University hours

To date, LIGO has only detected gravitational waves from binary systems, but one day it will detect the first non-binary source of gravitational waves, said Ore Gottlieb, a Northwestern University astrophysicist and lead author of the study, in a Northwestern publication. Cocoons are one of the first places we should look for this type of source.

While such waves have not yet been observed, they have been predicted in simulations by Gottlieb and his colleagues. Researchers modeled how stars die, flinging material outward as it collapses inward, leaving a black hole in the voids they leave behind.

The researchers were trying to determine whether black hole accretion disks, the superheated material surrounding black holes and makes their shadows visible in radio telescope imagesthey could be sources of gravitational waves.

An image of the black hole at the center of M87, surrounded by superheated material.

But looking toward the accretion disks, the team’s calculations were disrupted by data modeled from the cocoon of material surrounding the jets of accelerated material produced by dying stars. The model suggested that material around the jets could cause spacetime perturbations that lie within the frequency band detected by LIGO.

Detecting gravitational waves from new sources would also be a boon for astrophysicists trying to trace the gravitational wave backgroundor the hum of gravitational waves sweeping through the universe at all times. Scientists are looking for the gravitational-wave background using pulsar timing arrays, which work similar to LIGO but rely on synchronizing detections of light emitted by rapidly rotating pulsars instead of subterranean laser pulses.

A holy grail of gravitational-wave astronomy would be a space observatory that would function in the same way, but on a much larger scale than LIGO (which has since expanded and joined with other observatories to form the LIGO-Virgo- KAGRA. ) Instead of using 2.5 miles long LIGOs (4 kilometer) arms to detect gravitational waves, astrophysicists could use the 1.5 million mile (2.41 million km) long arms of the proposed LISA mission.

But whenever such an observatory occurs, it sure helps to know where to look.

Other: A black hole has collided with something that shouldn’t exist

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