When you imagine an explosion in space, a supernova is usually what first comes to mind. But astronomers are still quite puzzled by some of the details of these cosmic fireworks. The typical supernova we often picture is really the end of a massive star’s life — a very dramatic ending.
During its life, a star keeps its spherical shape through a very delicate balance between the outward pressure created by the central engine and the gravity that compresses the star. But as massive stars (more than 8 times the mass of the Sun) get older, they slowly run out of fuel in their engines and the balance starts to shake. When in the end there is no fuel left, there is also no force protecting the star from falling onto itself, and the star collapses.
A supernova is, therefore, technically first an implosion. Only when the innermost parts (what we call the core of the star) have collapsed and the outer layers fall onto this now extremely compact core and bounce off it — like a ball from the ground — is it an explosion. That’s when the star goes supernova, which we can detect as soon as the bounced off material breaks through the star›s outermost layer — we call this the shock breakout. Now you might expect: since a star is a sphere, like a ball, it only makes sense that the explosion is also shaped like a sphere, right? It turns out that’s not quite true.
Astronomers have now directly observed the true shape of a supernova explosion — SN 2024ggi — just after the shock broke out of the star, and were able to see how it changes, for the first time. They found that the supernova starts off shaped more like an olive. And they managed to observe this just about a day after the supernova was first detected.
The dying star was relatively close in astronomical terms: about 22 million light-years away, making it shine very bright. Nevertheless, observing this very early phase of a supernova explosion is not easy at all. As mentioned, it goes off so fast that there is only a limited time in which the supernova shock breakout is detectable. Thankfully, the European Southern Observatory reacted quickly and pointed its Very Large Telescope (VLT) at it. This observation — using a special kind of instrument — allowed astronomers to capture the initial shape of the explosion and analyse how it evolves in later stages. Strangely enough, the supernova doesn’t keep its olive-like shape throughout the explosion. In fact, it later puffs up sideways and transforms into what looks like a huge cosmic watermelon, enclosing everything
close by.
The astronomers consider this specific supernova to be quite an ordinary one, so they believe that it is representative of most massive stars’ explosive death. Ultimately, there are probably many more of these olive-shaped supernovae out there in
the Universe.
Why exactly these shapes occur is not yet clear, but astronomers are one step closer to understanding stars and some of the most dramatic light shows out there!
(Space Scoop)
