Chuck Bednar for redOrbit.com – @BednarChuck
By analyzing the remnant of a recently-exploded star, researchers have confirmed what computer models have long predicted – when stellar giants die, they do so in a lopsided fashion, as the core of the star is flung off in one direction and debris is sent flying the opposite way.
Confirmation came as California Institute of Technology physics professor Fiona Harrison and a team of colleagues studied observations of the remnant of supernova (SN) 1987A from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR). During their analysis, Harrison’s team found the unique energy signature of a radioactive version of titanium, titanium-44.
Titanium-44 is “unstable,” Harrison explained in a statement, and it is produced during the early stages of a Type II or core-collapse supernova. As it decays and turns into calcium, it gives off a series of gamma rays at a specific energy that can be detected by NuSTAR, they explained.
By looking at the direction-dependent frequency changes, or Doppler shifts, of energy from the radioactive form of titanium, the researchers were able to discover the majority of the material is moving away from NuSTAR, providing evidence that the mechanism behind Type II supernovae is inherently lopsided. Their findings appear in the May 8 edition of Science.
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Using this information to solve the mysteries of supernovae
As the researchers explained in their paper, titanium-44 is produced in the innermost ejecta of a core-collapse supernova, in the layer of materials directly above the new compact object formed by the process. This allows astronomers to get a direct look at the inner workings of the Type II supernova’s so-called engine, revealing “large-scale asymmetry in the explosion.”
First detected in 1987, supernova 1987A was the result of an exploding blue supergiant star that was about 168,000 light years from Earth. It was the closest supernova to be detected in several hundred years, and also marked the first time that neutrinos were detected from an astronomical source other than our sun.
Now, it has provided evidence to support supercomputer models conducted at Caltech, as well as at other laboratories, predicting that the cores of pending Type II supernovae change shape just before exploding. Those projections said that they would transform from a perfectly symmetrical sphere into a wobbly mass consisting of turbulent plumes of extremely hot gas.
The simulations went on to suggest that the shape change was the result of turbulence caused by neutrinos absorbed within the core, which helped “push out a powerful shock wave” that caused the explosions, according to Christian Ott, a professor of theoretical physics at Caltech who was not involved in the new study that analyzed the NuSTAR data.
Now, both Harrison’s team and Orr’s team plan to combine their efforts, using both observed and theoretical simulation data to solve some of the mysteries surrounding supernovae, including why some exploding stars collapse into neutron stars and others into a black hole to form a space-time singularity, and what role (if any) the degree of asymmetry plays in this phenomenon.
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