Splotchy supernova shakes assumptions.
An irregularly shaped spot, stain, or colored or discolored area: "spectacular splotches of color and beauty in the blossoms" Wendy Lyon Moonan.
tr.v. supernova supernova, a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. shakes assumptions
The expanding shell of gas surrounding supernova 1987 A is more likely to be lumpy or disk-like than a uniform sphere, says Scott Barthelmy of the NASA NASA: see National Aeronautics and Space Administration.
in full National Aeronautics and Space Administration
Independent U.S. Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. Until now, astronomers have always assumed in their theoretical models that the gas cloud from a supernova explosion has a spherical symmetry as it expands.
Barthelmy and his collaborators measured the gamma-rays given off by the radioactive decay radioactive decay
1. Spontaneous disintegration of a radionuclide accompanied by the emission of ionizing radiation in the form of alpha or beta particles or gamma rays.
2. An instance of such disintegration. of cobalt-56, which was synthesized in the supernova explosion. The standard model of a supernova explosion predicts that Earth-based observers should see only the gamma-rays coming from the Earth-facing side of the explosion. This forward motion would shift the emitted gamma-rays to a slightly shorter wavelength. Furthermore, because the gamma-rays should be coming from a narrow shell of gas, the range of wavelengths would be small, producing a sharp line in the gamma-ray spectrum. However, the researchers saw a wide spectral line spectral line
An isolated bright or dark line in a spectrum produced by emission or absorption of light of a single wavelength.
spectral line and detected no shift to a shorter wavelength.
Two possible scenarios explain these results. In one, the expanding envelope of gas has broken up into fragments, allowing observers to detect gamma-ray emissions from both the front and the back of the gas cloud. "There may be tunnels and holes so that we can see all the way to the back side," Barthelmy says. Alternatively, the gaseous material may be flattened into a disk that's tilted with respect to the line of sight to the Earth. This would allow observers to detect gamma-rays emitted from material traveling toward or away from the Earth.
"By studying the shape of gamma-ray lines, we're learning a lot about the explosion itself," Barthelmy says. "Until these results, nobody had ever speculated that asymmetries [in the expanding gases] could show up at such an early age."