Autopsy Of Supernova's Aftermath Yields Surprising Results

Brett Smith for redOrbit.com – Your Universe Online

In 1987, astronomers in the Southern Hemisphere witnessed the violent death of a giant star in the form of a supernova.

Now, a large team of researchers has published the results of an extensive ‘autopsy’ on Supernova 1987A using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile’s Atacama Desert and the Australia Telescope Compact Array (ATCA) in Australia.

“By combining observations from the two telescopes we’ve been able to distinguish radiation being emitted by the supernova’s expanding shock wave from the radiation caused by dust forming in the inner regions of the remnant,” said Giovanna Zanardo of the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia and lead author of the study published in The Astrophysical Journal.

“This is important because it means we’re able to separate out the different types of emission we’re seeing and look for signs of a new object which may have formed when the star’s core collapsed,” Zanardo said. “Our observations with the ATCA and ALMA radio telescopes have shown signs of something never seen before, located at the center or the remnant. It could be a pulsar wind nebula, driven by the spinning neutron star, or pulsar, which astronomers have been searching for since 1987.”

“It’s amazing that only now, with large telescopes like ALMA and the upgraded ATCA, we can peek through the bulk of debris ejected when the star exploded and see what’s hiding underneath,” she added.

Using the telescopes, the study team was able to examine the radio emissions of Supernova 1987A in the far infrared end of the spectrum. Another recent study based on these observations was able to solve a long-standing mystery: why one side of the supernova remnant looks ‘brighter’ than the other.

Image Above: Left Panel: SNR1987A as seen by the Hubble Space Telescope in 2010. Middle Panel: SNR1987A as seen by the Australia Telescope Compact Array (ATCA) in New South Wales and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Right Panel: A computer generated visualization of the remnant showing the possible location of a Pulsar. Credit: ATCA & ALMA Observations & data – G. Zanardo et al. / HST Image: NASA, ESA, K. France (University of Colorado, Boulder), P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics). More images can be found here.

Also published in The Astrophysical Journal, the second study used a detailed three-dimensional computer model of the expanding supernova shockwave.

“By introducing asymmetry into the explosion and adjusting the gas properties of the surrounding environment, we were able to reproduce a number of observed features from the real supernova such as the persistent one-sidedness in the radio images,” said study author Toby Potter, an ICRAR researcher.

The time-progression simulation revealed that the eastern, or left, side of the growing shockwave swells more swiftly than the other side, resulting in more radio emission than on the weaker side. This influence becomes much more obvious as the shock wave slams into the equatorial ring, as shown in Hubble Space Telescope pictures of the supernova, the researcher said.

“Our simulation predicts that over time the faster shock will move beyond the ring first,” the study team said. “When this happens, the lop-sidedness of radio asymmetry is expected to be reduced and may even swap sides.”

“The fact that the model matches the observations so well means that we now have a good handle on the physics of the expanding remnant and are beginning to understand the composition of the environment surrounding the supernova – which is a big piece of the puzzle solved in terms of how the remnant of SN1987A formed,” the researchers added.

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