October 18, 2012
INTEGRAL Finds Radioactive Decay Of Titanium Around Supernova Remnant
April Flowers for redOrbit.com - Your Universe Online
Radioactive titanium associated with supernova remnant 1987A has been directly detected by ESA's Integral space observatory. The glowing remnant around the exploded star has likely been powered by the decaying from this titanium for the last 20 years.
The first space observatory that can simultaneously observe objects in gamma rays, X-rays and visible light, Integral's principal targets are violent explosions known as gamma ray bursts, supernova explosions, and black holes.
Like nuclear furnaces, stars continuously fuse hydrogen into helium within their cores. Stars that are eight times the mass of our Sun collapse when they exhaust their hydrogen fuel, sometimes generating temperatures high enough to create much heavier elements through fusion. These elements are titanium, iron, cobalt and nickel. These elements are flung into space when the star rebounds and explodes in a spectacular supernova.
For a brief time, supernovae can shine as brightly as entire galaxies because of the massive amount of energy released when they explode. After that initial flash subsides, the total luminosity of the remnant is created by the release of energy from radioactive elements produced in the explosion decaying.
Because each element emits energy at a distinct wavelength as it decays, it provides insight into the chemical composition of the shells of material ejected by the exploding star.
Supernova 1987A is located in the Large Magellanic Cloud, one of the Milky Way's nearby satellite galaxies. According to ESA, SN1987A was close enough to be seen by the naked eye when its light first reached Earth in February 1987.
The distinctive fingerprints of elements from oxygen to calcium were detected during the peak of the explosion, representing the outer layers of the ejecta. Signatures of materials created in the inner layers were seen soon after in the radioactive decay of nickel-56 to cobalt-56, and its subsequent decay to iron-56.
Over 1000 hours of observation by the Integral space observatory has detected high-energy X-rays from radioactive titanium-44 for the first time from SNR1987A. The results of these observations have been published in the journal Nature.
“This is the first firm evidence of titanium-44 production in supernova 1987A and in an amount sufficient to have powered the remnant over the last 20 years,” says Sergei Grebenev from the Space Research Institute of the Russian Academy of Science in Moscow.
The astronomers estimate the total mass of titanium-44 produced just after the core collapse of SN1987A amounted to 0.03% of the total mass of our Sun. This is nearly twice the amount seen in supernova remnant Cas A, the only other remnant where titanium-44 has been detected, and near the theoretical prediction boundary.
“The high values of titanium-44 measured in Cas A and SNR1987A are likely produced in exceptional cases, favoring supernovae with an asymmetric geometry, and perhaps at the expense of the synthesis of heavier elements,” says Dr Grebenev.
“This is a unique scientific result obtained by Integral that represents a new constraint to be taken into account in future simulations for supernova explosions,” adds Chris Winkler, ESA´s Integral project scientist. These observations are broadening our understanding of the processes involved during final stages of a massive star´s life.”
Image Caption: The image above shows the patch of the sky surrounding the remnant of supernova remnant 1987A as seen in three different bands at high X-ray energies with ESA´s Integral. Titanium-44 is only present in the central image, which spans the 65—82 keV energy range. The panel on the left is based on data collected in the 48—65 keV band, whereas the panel on the right is based on data collected in the 82—99 keV band. The presence of signal corresponding to the position in the sky of SNR 1987A only in the energy range between 65 keV and 82 keV demonstrates that the signal does arise from emission at the specific wavelengths unique to the radioactive decay of Ti-44, at 67.9 keV and 78.4 keV. Also seen in the field of view are two other bright sources of high-energy emission, the black hole binary known as LMC X-1 and the pulsar PSR B0540-69. Credits: ESA/Integral/IBIS—ISGRI/S. Grebenev et al.