The “cocoons” of debris surrounding dying stars appear to be capable of creating tiny ripples in space-time.
So far, astronomers have only detected these ripples, known as gravitational waveswhen they were triggered by cataclysmic mergers of pairs of orbiting black holes, neutron stars or a combination of the two. As these very dense objects spiral towards each other in a cosmic dance spanning millions of years, they distort the fabric of space and time, emitting gravitational waves in the process.
Now, new research shows that these elusive space-time ripples are also emitted by solo members of the universe, particularly massive stars that collapse in on themselves after running out of fuel, and that those signals might even be powerful enough to be detected. from tools on Earth.
According to a new study, when incredibly dense stars 20 to 40 times more massive than the sun, those that collapse to form black holes — explode at the end of their lives, their stellar material forms a cloud-like “cocoon” of debris, which is “a potential source of gravitational waves that has never been studied before,” Ore Gottlieb, a high-tech theoretical astrophysicist energy of the Northwestern University that conducted the study, said Monday (June 5) at the 242nd meeting of the American Astronomical Society to be held in Albuquerque and online.
Related: What are gravitational waves?
While binary systems like orbiting black holes emit gravitational waves similar to a harmoniously playing orchestra, cocoons of stellar debris around exploding massive stars radiate very incoherent signals, Gottlieb said. The new findings could shed light on the less-studied type of such random ‘stochastic’ gravitational waves that are thought to be very common in the universe but extremely difficult to discern, thanks to their confusing nature.
In the new study, Gottlieb and his team simulated the collapse of a massive star into a black hole, during which a burst of energy called relativistic jet took shape and exploded from the star that collapses a similar to light speed. Much like drilling a hole in a wall, “a jet starts deep inside a star and then works its way out,” Gottlieb said in a declaration.
Gottlieb’s team was initially looking to see if the superheated disk of stellar material around the black hole, called an accretion disk, could produce gravitational waves. However, as the simulation continued, the outgoing jet collided with the dying star’s collapsing material layers, heating the debris and inflating it into an hourglass-shaped structure, also called a stellar cocoon. The results of this simulation showed for the first time that such cocoons of stellar debris emit gravitational waves at detectable frequencies, according to the new study.
“To be honest, I didn’t look for cocoons, but the cocoons were too strong to ignore, so I had to go and study [them]Gottlieb said at Monday’s press conference. “So it was more or less by accident that I started trying to understand their gravitational wave emission.”
The elusive gravitational waves emitted by stellar cocoons, whose signals according to astronomers are the weakest and more difficult to locate, come from objects throughout the universe and continually pass by the Earth, but they are so random and tangled that predicting their visit or solving them is nearly impossible. Additionally, various regions in a supernova explosion emit signals at different frequencies, making the already elusive waves much harder to detect than the cleaner signals beamed by orbiting cosmic beasts like black holes or neutron stars.
“However, there is much anticipation for the first detection of gravitational waves not from a merger of compact objects, and this is something expected to be detected in the next decade or so,” Gottlieb said during his presentation on Monday.
Gravitational waves from stellar cocoons are thought to be promising candidates because they have the right shape, not too symmetrical, to emit signals strong enough to be detected. They also evolve rapidly, which means there’s a greater chance of detecting signals from them, according to Gottlieb.
THE Laser Interferometer Gravitational Wave Observatory (LIGO), which constitute the worldwide network of the four massive research facilities designed to hunt for gravitational waves, they have yet to locate gravitational waves from stellar cocoons. However, simulations show that the signals from such sources are powerful enough for LIGO to detect in its next observing sessions, Gottlieb said on Monday.
“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,” Gottlieb said in the declaration. “Cocoons are one of the first places we should look for this type of source.”
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