Supernova remnant 1987A continues to reveal secrets

A team of astronomers led by the International Centre for Radio Astronomy Research has succeeded in observing the death throes of a giant star in unprecedented detail.

Just over 25 years ago, in February 1987, astronomers observing the Large Magellanic Cloud – a nearby dwarf galaxy – noticed the sudden appearance of what appeared to be a new star. But they were watching not the birth of a star but the death of one.

It was the brightest supernova seen from Earth since the telescope was invented 400 years ago. By the following day, news of the discovery had spread around the globe, and southern hemisphere stargazers began watching the aftermath of the enormous stellar explosion.

Since then, the remnant of what astronomers call Supernova 1987A has continued to be a focus for researchers around the world, providing a wealth of information about one of the universe’s most extreme events.

In research published in the Astrophysical Journal, astronomers in Australia and Hong Kong used the Australia Telescope Compact Array in New South Wales to make the highest resolution radio images yet obtained of the expanding supernova remnant at millimetre wavelengths.

“Imaging distant astronomical objects like this at wavelengths less than one centimetre demands the most stable atmospheric conditions,” said the lead author, Dr Giovanna Zanardo of ICRAR. “For this telescope these are usually only possible during cooler winter conditions; but even then, the humidity and low elevation of the site makes things very challenging.”

Unlike optical telescopes, a radio telescope can operate in the daytime and can peer through gas and dust, allowing astronomers to see the inner workings of supernova remnants, radio galaxies and black holes.

“Supernova remnants are like natural particle accelerators, the radio emission we observe comes from electrons spiralling along the magnetic field lines and emitting photons every time they turn. The higher the resolution of the images, the more we can learn about the structure of this object,” said Professor Lister Staveley-Smith, deputy director of ICRAR and the Centre for All-sky Astrophysics.

Scientists study the evolution of supernovae into supernova remnants to gain an insight into the dynamics of these massive explosions and the interaction of the blast wave with the surrounding medium.

“Not only have we been able to analyse the morphology of Supernova 1987A through our high-resolution imaging, we have compared it to X-ray and optical data in order to model its likely history,” said centre Director Professor Bryan Gaensler.

The team suspects a compact source or pulsar wind nebula to be sitting at the centre of the radio emission, implying that the supernova explosion did not make the star collapse into a black hole. They will now attempt to observe further into the core and see what’s there.