When Supernova 1987A first appeared in earthly skies 26 years ago, astronomers were beside themselves with delight. It was the closest observed supernova since 1604. In this shining pinpoint in our sky, those fortunate to be in Earth’s Southern Hemisphere (in whose sky the supernova appeared) could see the death throes of a giant star. The new star remained visible to the eye for many months. It has been studied by astronomers for decades since. Today (April 2, 2013), astronomers in Australia and Hong Kong released new images and insights about this nearby supernova. Their work, published today in Astrophysical Journal, suggests that:
… a compact source or pulsar wind nebula [is] sitting in the center of the radio emission, implying that the supernova explosion did not make the star collapse into a black hole.
Their plan for the coming months and years is to attempt to observe further into the core of Supernova 1987A, and see what’s there.
The image above, provided by the Australian and Hong Kong astronomers, is an overlay of radio emission (contours) and a Hubble space telescope image of Supernova 1987A (in center). Astronomers at the International Centre for Radio Astronomy Research (ICRAR) in Perth, Australia led this research. They used the Australia Telescope Compact Array, CSIRO radio telescope in northern New South Wales, to make what they say are the highest resolution, or clearest, radio images of the expanding supernova remnant at millimeter wavelengths.
They say the radio emission comes from electrons spiralling along the magnetic field lines and emitting photons every time they turn. In this way, according to these astronomers, “supernova remnants are like natural particle accelerators.”
Whether it’s radio or visible light, the clearer the image, the more astronomers can learn about the structure of this distant supernova. Why should we care about Supernova 1987A, and about supernovae in general? There are some good reasons!
1. We are made of stardust. When you hear this common phrase, you know that astronomers today believe that a large fraction of the atoms in our bodies were forged inside stars. Supernovae are the mechanism by which the atoms created in stars – the same atoms that make up our bodies and all that we know – are released into space.
2. High-energy radiation and how life evolves. Astronomers belive that supernova explosions flood our Milky Way galaxy with high-energy radiation that probably contributed to the radiation background that produces mutation and drives the evolution of life on Earth.
3. A cosmic trigger to our local solar system. There is intriguing evidence that a supernova triggered the formation of our own solar system – our sun, Earth and the other planets near us in space – five billion years ago.
For all these reasons and more, astronomers want to know what makes supernovae explode, and what happens after they do.
The word nova, of course, means new star. Early astronomers like Johannes Kepler thought he was witnessing the birth of a new star when he first saw the supernova that now bears his name – Kepler’s Star – in 1604. That was the last nearby supernova, and it was before the invention of telescopes.
Today, we know we’re not watching the birth of a star, but the death of one. Supernova 1987A was the brightest supernova seen from Earth in the four centuries since the telescope was invented. The explosion occurred 160,000 years ago, in the Large Magellanic Cloud – a nearby dwarf galaxy. The light of the explosion – travelling at 186,000 miles per second (300 million meters per second) – finally reached Earth on February 23-24, 1987.
Bottom line: Astronomers at the International Centre for Radio Astronomy Research (ICRAR) in Perth, Australia led research leading to a high resolution image of Supernova 1987A at radio wavelengths. Their work suggests that there is no black hole at the center of the supernova remnant, but instead there is a compact source or pulsar wind nebula (a nebula powered by the pulsar wind of a pulsar) at its center.