What do supernovae look like

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The era of greyhound racing in the U. See how people have imagined life on Mars through history. Life on Earth will be unharmed. Goldberg and Bauer found that when Betelgeuse explodes, it will shine as bright as the half-Moon — nine times fainter than the full Moon — for more than three months. Everyone all over the world would be curious about it, because it would be unavoidable.

And it would be visible at night with the naked eye for several years, as the supernova aftermath dims. A supernova has to happen extremely close to Earth for the radiation to harm life — perhaps as little as several dozen light-years, according to some estimates.

Betelgeuse is far outside that range, with recent studies suggesting it sits roughly light-years away, well outside the danger zone. But the supernova could still impact Earth in some surprising ways. For example, Howell points out that many animals use the Moon for navigation and are confused by artificial lights. Adding a second object as bright as the Moon could be disruptive. The bright light would overwhelm their instruments. And if Betelgeuse does defy the odds and blow up in our lifetimes, astronomers say there will be ample warning.

Instruments on Earth would start detecting neutrinos or gravitational waves generated by the explosion as much as a day in advance. Some astronomers even suspect that several different dimming mechanisms are playing out at once. As their nuclear fuel runs out near the ends of their lives, red supergiant stars start to bloat and form growing envelopes of gas and dust.

Red supergiant stars also have enormous convective cells on their surfaces — like much larger versions of those on our Sun — where turbulence makes hot material rise from inside the star. Once it reaches the surface, part of that material erupts violently into space like a giant, radioactive belch, which can temporarily change its brightness.

Whatever the root cause, the strange behavior should ultimately offer new insights into the dying days of red supergiant stars. A star is in balance between two opposite forces. This outward push resists the inward squeeze of gravity. What holds stars together? When a massive star runs out of fuel, it cools off. This causes the pressure to drop. Gravity wins out, and the star suddenly collapses. Imagine something one million times the mass of Earth collapsing in 15 seconds!

The collapse happens so quickly that it creates enormous shock waves that cause the outer part of the star to explode! Usually a very dense core is left behind, along with an expanding cloud of hot gas called a nebula.

A supernova of a star more than about 10 times the size of our sun may leave behind the densest objects in the universe— black holes. The Crab Nebula is the leftover, or remnant, of a massive star in our Milky Way that died 6, light-years away. Astronomers and careful observers saw the supernova in the year The nebula of expelled matter created around Betelgeuse, which, for scale, is shown in the interior This structure, resembling flames emanating from the star, forms because the behemoth is shedding its material into space.

The extended emissions go beyond the equivalent of Neptune's orbit around the Sun. Even when it transitions from carbon to neon to oxygen to silicon fusion, we won't have any directly observable signatures of those events. The rate of the core's fusion and energy output will change, but our understanding of how that affects the star's photosphere and chromosphere — the parts that we can observe — is too poor for us to extract concrete predictions about.

The energy spectrum of the neutrinos produced in the core, the one observable we know will change, is irrelevant, as the neutrino flux is far too low to be detectable from hundreds of light-years away. But at some critical moment in the star's evolutionary process, the inner core's silicon burning will reach completion, and the radiation pressure deep inside Betelgeuse will plummet. As this pressure was the only thing holding the star up against gravitational collapse, the inner core, composed of elements like iron, cobalt, and nickel, now begins to implode.

Artist's illustration left of the interior of a massive star in the final stages, pre-supernova, Silicon-burning is where iron, nickel, and cobalt form in the core.

A Chandra image right of the Cassiopeia A supernova remnant today shows elements like Iron in blue , sulphur green , and magnesium red. Betelgeuse is expected to follow a very similar pathway to previously observed core-collapse supernovae. It's difficult to imagine the scale of this: an object totaling about 20 solar masses, spread out over the volume of Jupiter's orbit, whose inner core is comparable to and more massive than the size of the Sun, suddenly begins to rapidly collapse.

As large as the gravitational force was pulling everything in on itself, it was counterbalanced by the radiation pressure coming from nuclear fusion in the interior. Now, that fusion and that outward pressure is suddenly gone, and collapse proceeds uninhibited.

The innermost atomic nuclei — a dense collection of iron, nickel, cobalt and other similar elements — get forcefully scrunched together, where they fuse into an enormous ball of neutrons. The layers atop them also collapse, but rebound against the dense proto-neutron star in the core, which triggers an incredible burst of nuclear fusion. As the layers pile up, they rebound, creating waves of fusion, radiation, and pressure that cascade through the star.

In the inner regions of a star that undergoes a core-collapse supernova, a neutron star begins to Neutrons, neutrinos, radiation, and extraordinary amounts of energy are produced.

These fusion reactions take place over a timescale of approximately 10 seconds, and the overwhelming majority of the energy is carried away in the form of neutrinos, which hardly ever interact with matter.