A team of astrophysicists using ESA’s International Gamma-Ray Astrophysics Laboratory (Integral) has reported the first direct detection of radioactive titanium in supernova remnant 1987A.
This image shows supernova remnant SNR 1987A, located in the Large Magellanic Cloud. The titanium-44 detected by the team of astrophysicists is powering only the innermost part of the remnant (ESA / Hubble / NASA)
Located 166,000 light-years away in the Large Magellanic Cloud, supernova 1987A was close enough to be seen by the naked eye when its light first reached us in February 1987. During the peak of the explosion, fingerprints of elements from oxygen to calcium were detected, representing the outer layers of the ejecta. Soon after, signatures of the material synthesized in the inner layers could be seen in the radioactive decay of nickel-56 to cobalt-56, and its subsequent decay to iron-56.
Now, the team has detected X-rays from radioactive titanium-44 in supernova remnant 1987A.
“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,” said Dr Sergei Grebenev of the Russian Academy of Science’s Space Research Institute in Moscow, lead author of a paper reporting the discovery in the journal Nature.
The team estimated that the total mass of titanium-44 that must have been produced just after the core collapse of SN1987A’s progenitor star amounted to 0.03% of the mass of our own Sun. This value is near the upper boundary of theoretical predictions and is nearly twice the amount seen in supernova remnant Cas A, the only other remnant where titanium-44 has been detected.
“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,” Dr Grebenev explained.
“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,” said study co-author Dr 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.”
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Bibliographic information: Grebenev S.A. et al. 2012. Hard-X-ray emission lines from the decay of 44Ti in the remnant of supernova 1987A. Nature 490, 373–375; doi: 10.1038/nature11473
