The Webb Telescope peered deep into the remnants of a nearby supernova

In November 1572, Tycho Brahe noticed the presence of a new star in the constellation Cassiopeia. It was the first supernova to be observed in detail by Western astronomers and became known as the Tycho supernova. Previous supernovae had been observed by Chinese and Japanese astronomers, but Tycho’s observations showed the Catholic world that stars were not as fixed and unchanging as Aristotle had assumed. Just three decades later, in 1604, Johannes Kepler watched a supernova in the constellation Ophiuchus brighten and fade. No supernovae have been observed in the Milky Way since then.

More than three centuries have passed. Galileo pointed his first telescopes at the sky. Astrophotography has revolutionized our view of the sky, as has radio astronomy. We have launched telescopes into space, landed on the moon, and sent robotic probes into the outer solar system.

But there were no nearby supernovas that could be observed with our intelligent instruments until February 1987, when a supernova appeared in the Large Magellanic Cloud. Known as SN 1987a, it reached a maximum apparent magnitude of about 3. It is the only supernova visible to the naked eye to occur in the era of modern astronomy.

In cosmological terms, SN 1987a is in our own backyard, just 168,000 light-years away. It has been studied over the years by ground-based and space telescopes, and recently, the James Webb Space Telescope took a closer look at it. The results tell us a lot about the rare supernova, but they also raise some questions.

The highlight of the image is the bright equatorial ring of ionized gas. This ring was ejected from the star for thousands of years before it exploded. It is now heated by shock waves from the supernova. The equatorial ring encircles the hourglass shape of faint outer regions that emanate from the star’s polar regions. These structures have been observed before with telescopes such as Hubble and Spitzer. But the real power of JWST is looking at the center of SN 1987a. There, it reveals a turbulent keyhole structure as masses of gas expand into space. Rich chemical reactions began to occur in this area.

Structures seen in the new JWST image.

Image source: NASA, ESA, CSA, M. Matsuura, R. Arendt, C. Fransson

But even the James Webb Space Telescope was unable to observe the supernova’s final jewel, the remnant of the star. Supernovas not only release new material into interstellar space, but also cause a star’s core to collapse into a neutron star or black hole. Based on the scale of SN 1987a, a neutron star should have formed at its centre.

However, the gas and dust in the inner keyhole region is too dense for JWST to observe. How a neutron star forms and how it interacts with the gas and dust surrounding it is a mystery that needs further study. We have observed the neutron stars of some supernovae, but only from a much greater distance.

The Tycho supernova was only 8,000 light-years from Earth, and the Kepler supernova about 20,000 light-years away. Unless Betelgeuse explodes in the near future, SN 1987a will likely be the closest new supernova we’ll be able to study for some time.

This article was originally published on The universe today By Brian Koberlein. Read the original article here.

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