When did Supernova explode in 1987A

In February 1987, a supernova, an exploded star, lit up in the Large Magellanic Cloud. To this day, astronomers have been puzzling over what kind of star exploded back then and how this explosion went. Now, for the first time, two researchers have succeeded in using a computer simulation to explain the observed structures of the supernova.

Oxford (Great Britain) - According to this, two stars collided with each other 20,000 years before the explosion - and there was not one, but two explosions. The scientists present the results of their simulations in the journal "Science".

"The 1987A supernova in the Large Magellanic Cloud was one of the most important astronomical events of the 1980s," write Thomas Morris and Phillipp Podsiadlowski of the University of Oxford, "but it was highly unusual." Astronomers expect a red giant star to be the predecessor star of a supernova - but 1987A was a blue giant before the explosion. In addition, the previous star contained too much helium in its outer layers - signs of an unusual intermingling of the stellar matter. And finally, the supernova was surrounded by a complex structure, three superimposed gas rings.

Astronomers have long suspected that the supernova could have been preceded by the merging of two massive stars. This basically explains the unusual color of the star and the high proportion of helium. "But so far there has been no conclusive evidence that such a merger actually took place," said Morris and Podsiadlowski.

The two researchers are now providing this proof, because their simulation can also explain the three gas rings around the supernova. Their detailed hydrodynamic model of the two stars and the merging process shows that there have been two explosions. The first explosion created an hourglass-like structure of ejected matter. Viewed from the earth, this structure appears in the form of two rings displaced against the supernova. A second explosion eventually led to the formation of the smaller, inner ring around the supernova.

"The hydrodynamic model we presented provides an excellent fit for the triple ring observed," said Morris and Podsiadlowski happily. In addition, her model makes a number of predictions - for example about the mass and chemical composition of the rings. This means that the model can be checked through further observations.