New studies reveal that Supernova Cassiopeia A shows signs of bubbles which might have been created by radioactive metal. Cassiopeia A violently exploded 340 years ago, blowing the inner layers of the star outward into a shockwave-like formation. New observations suggest that radioactive nickel may have caused its unique shapes.
Astronomers believe that observing and studying the bubble-like interior of the supernova may help them also understand the reason why supernovas explode. These herculean eruptions are responsible for spreading new and heavy elements throughout the cosmos, which provides for the germination of new planets – just like the Earth was born with a vast array of heavy elements.
Postdoctoral researcher Dan Milisavljevic, with the Harvard Smithsonian Center for Astrophysics, feels the need to understand why these gaseous giants explode. He is using Cassiopeia A, located 11,000 light years from Earth, as a base point for stellar detonation.
Milisavljevic says that he and his team work as a cosmic bomb squad. A bomb squad analyzes how and why a bomb explodes. Along with Dartmouth College Professor Rob Fesen, Milisavljevic authored a paper analyzing the wreckage and debris of Cassiopeia A, which they found was not scattered randomly. They explained that at the core of the supernova there are cavernous assemblies which indicate a measurable and concise process to the explosion.
Current images of Cassiopeia A, taken by space telescopes, show a vibrant, multicolored façade of material around the circumference of the once bright and radiant star. The material from the supernova is illuminated by the shockwave that preceded the initial stages of the ferocious explosion. Astronomers have had difficulty peering beyond the supernova’s veneer due to the immense amount of star dust and clouds of heavy elements which surround the core.
To combat this, Milisavljevic and Fesen used a highly-advanced, four-meter-wide telescope located at the Kitt Peak National Observatory. They searched for light containing wavelengths towards the infrared spectrum. This type of light can pierce through the clouds of dust due to its minute wavelength range. When observing the supernova, the scientists found that sulfur, sensitive to this type of light, is very common in Cassiopeia A.
As a result, they were looking just where they should have been. The sulphur in the inner sections of the supernova created and held the bubble shapes. For example, this would compare to how a pillow holds an imprint of a head after you release the pressure. The two scientists also observed cavernous, hollowed-out regions near the core.
Milisavljevic and Fesen believe that the bubble formations were created by radioactive isotopes of nickel as the material from the once-star’s core exploded outward. This occurred after its own gravity allowed it to collapse on itself, which created the supernova. New studies show that the groups of radioactive nickel moved outward, thus expanding the clouds. The radioactive decay of the nickel atoms would have created photons, which would have had the energy to shove the clouds outward, thereby creating the bubble formations.
In addition to this finding, they explained that “bubble theory,” or cosmic inflation theory through entropy, could possibly give scientists the reason why larger structures exist in Cassiopeia A. Milisavljevic stated that if the radioactive nickel did in fact create the bubble structures, they would no longer exist in the body of the supernova. However, deposits of heavy iron elements may have been left behind. Moreover, the confirmation of this theory would involve scientists in efforts to locate groups of iron in and around the supernova, which could draw them to the conclusion of the mystery behind the bubble appearance.
By: Alex Lemieux
Picture: NASA’s Marshall Space Flight Center – Flickr License