![]() These cocoons should also emit light at different frequencies, and the double-whammy of gravitational waves and light always piques astronomers’ attention. That’s especially valuable because unless collapsing stars have jets and cocoons, their supernovae are too quiet for LIGO to hear unless they’re super close by. This new type of gravitational-wave signal could offer astronomers new insights into how stars’ cores collapse. (The jets themselves also produce gravitational waves when viewed down the beam, but at lower frequencies that are beyond LIGO’s domain.) Not only would the signal be distinct, it would be loud - loud enough, even, to be picked up by LIGO in the observing run that just started May 24th.Įven more critically, those gravitational waves would be at frequencies within LIGO’s reach, as long as we’re viewing the jets from the side. Unlike the happy bloops and chirps of inspiraling black hole pairs, the signal from an emerging jet-cocoon sounds more like the eerie howl of wind. Gottlieb presented the research during a press briefing at the 242nd meeting of the American Astronomical Society ( preprint available here). They then calculated the resulting gravitational-wave signal. To find out, Gottlieb’s team ran computer simulations that followed the jets - and the cocoons around them - all the way from their launch near the black hole to where they punch through the stellar surface and escape to space. It wasn’t immediately obvious that these gravitational waves would have the right pitch and volume for LIGO to “hear” them. “But these cocoons were too strong to ignore.It was more or less by chance that I started to try to understand their gravitational wave emission.” ![]() “To be honest, I didn't look for cocoons I was interested in another source of gravitational waves,” Gottlieb says. This jet-cocoon is what Ore Gottlieb (Northwestern University) and colleagues only recently realized can emit gravitational waves. For several seconds - until the jets break out of the star completely - the cocoon of gas that's wrapped around them creates ripples in spacetime, or gravitational waves. As the jets ram their way through the star’s outer layers, they amass a sheath of hot, dense star-stuff. This process powers two opposite jets that drill their way out of the star. First the center gives way, forming a black hole that immediately begins to feed. Hefty stars with 20 to 40 times the Sun’s mass die in particularly spectacular fashion. This source is within reach of the recently begun observing run of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Ore Gottlieb / CIERA / Northwestern UniversityĪ team of astronomers has uncovered a new possible source of gravitational waves: the cocoon of hot, dense gas that forms within a massive, dying star. The sound in the video represents the frequency of the gravitational waves. This image is a still from the full simulation video shown below. The color indicates the strength of the gravitational-wave signal. As the jet pierces the cocoon enveloping the newborn black hole at the star's center, the system emits gravitational waves.
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