Title: Researchers Propose Exploring Stellar Cocoons as a New Source of Gravitational Waves
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Scientists from Northwestern University have put forward a groundbreaking proposal to detect gravitational waves from non-binary sources. Until now, these elusive signals have only been detected from binary systems, such as mergers between black holes or neutron stars. However, the researchers suggest that the turbulent cocoons of debris surrounding dying massive stars could provide a novel and unexplored area to search for gravitational waves.
In a recent study, led by Northwestern’s Ore Gottlieb, the team used state-of-the-art simulations to demonstrate that these cocoons have the potential to emit gravitational waves. Unlike gamma-ray burst jets, cocoons’ gravitational waves should fall within the detection range of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Gottlieb explained, “As of today, LIGO has only detected gravitational waves from binary systems, but one day it will detect the first non-binary source of gravitational waves. Cocoons are one of the first places we should look to for this type of source.”
The researchers conducted simulations to model the collapse of a massive star and the subsequent formation of black holes. They found that the jets colliding into the collapsing layers of the dying star create a bubble or “cocoon” around the jet. This cocoon is a turbulent environment where hot gases and debris mix randomly and expand in all directions. As the energetic bubble accelerates from the jet, it perturbs space-time, generating gravitational waves.
“When I calculated the gravitational waves from the vicinity of the black hole, I found another source disrupting my calculations — the cocoon,” said Gottlieb. “I tried to ignore it, but I found it was impossible to ignore. Then I realized the cocoon was an interesting gravitational wave source.”
If cocoons do indeed produce gravitational waves, LIGO should be capable of detecting them in upcoming runs. While previous searches focused on single-source gravitational waves from events like gamma-ray bursts or supernovae, those efforts have had limited success due to the symmetrical nature of supernovae and the lower frequency of gamma-ray bursts. In contrast, cocoons are both asymmetrical and highly energetic, making them an attractive target for future studies.
“Our study is a call to action to the community to look at cocoons as a source of gravitational waves,” Gottlieb urged. “By studying them, we could learn more about what happens in the innermost parts of stars, the properties of jets, and their prevalence in stellar explosions.”
The researchers believe that studying cocoons could not only advance our understanding of the inner workings of stars but also potentially lead to multi-messenger events, where gravitational waves are detected in conjunction with other forms of radiation.
The study, titled “Jetted and Turbulent Stellar Deaths: New LVK-detectable Gravitational-wave Sources,” was published in The Astrophysical Journal Letters. It was made possible through the support of the National Science Foundation, NASA, and the Fermi Cycle 14 Guest Investigator program, and advanced simulations were conducted using supercomputers provided by the Department of Energy’s Oak Ridge National Laboratory and the National Energy Research Scientific Computing Center.
As the search for gravitational waves continues to evolve, this study opens up a promising avenue for discovery and highlights the importance of exploring diverse astronomical phenomena to unlock the secrets of our universe.