In November 1572, Tycho Brahe observed a new star in the constellation Cassiopeia. It was the first supernova to be observed in detail by Western astronomers and has become known as Tycho's supernova. Observations by Chinese and Japanese astronomers had preceded other supernovae, but Tycho's observations revealed to the world that stars were not fixed and unchanging, as Aristotle. Just three decades later, in 1604, Johannes Kepler observed a supernova explosion in the constellation Ophiuchus. This phenomenon would glow brightly and then fade away. No supernova explosions have been observed in Milky Way .
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More than three centuries have passed since then. Galileo turned to the sky with his first telescopes. Astrophotography has redefined our perception of the sky, as has radio astronomy. We have launched telescopes into space, reached the Moon , and sent robotic probes to the outer reaches of the Solar System.
However, we didn't get a chance to observe nearby supernovae with our smart instruments until February 1987, when a supernova appeared in the Large Magellanic Cloud. Known as SN 1987a, this bright star is the only supernova visible to the naked eye in the era of modern astronomy.
Cosmologically, SN 1987a is right in our backyard, just 168,000 light-years away. It has been studied extensively with both ground-based and space-based telescopes , and recently the James Webb Space Telescope took a closer look. The results tell us a lot about the rare supernova, but they also raise a few questions.
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The image shows a bright ring of ionized gas at the equator. This ring was ejected from the star thousands of years before it exploded, remaining intact throughout that time. It is currently being heated by shock waves from the supernova. The true power of JWST, however, is revealed when it looks into the center of SN 1987a. There, it reveals a turbulent keyhole structure where clumps of gas are expanding into space. In this region, rich chemical interactions are observed to be occurring.
Even JWST couldn't observe the ultimate supernova , the star that remains. Supernovae not only blast new material into space, but also cause the core of stars to collapse, creating neutron stars or black holes. Based on the scale of SN 1987a, a neutron star should have formed at its center.
However, the air and dust inside the keyhole are so dense that JWST cannot observe them. The process of creating a neutron star and how it interacts with galactic gas and dust remains an unsolved mystery that requires further study and understanding. We have observed the neutron stars of some supernovae, but only from a much greater distance.
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Tycho's supernova was only 8,000 light-years from Earth, while Kepler was about 20,000 light-years away. Barring something unexpected, like the explosion of Betelgeuse in the very near future, SN 1987a is likely to be the closest new supernova we'll be able to study for some time.
