In Oversight, humanity tries to recover from a narrowly won war against an alien species. We survived, but the planet is destroyed and the only hope – at least according to the authorities – is to leave Earth behind. At the start of the film, that’s what we think is happening. In truth, the conflict is ongoing. The space station carrying humanity off-world is actually an alien ship that steals humanity’s last resources before it departs. They even tricked people like Jack Harper into helping them. Humanity eventually prevails, but it was a close thing. If only we had been warned in advance.
As far as actual oblivion goes, there are few things in the universe more destructive than a supernova, and astronomers have no real way of knowing when it’s going to happen. Although supernovae aren’t a cosmic threat to Earth – our star isn’t big enough to enjoy such a dazzling ending – they cause incredible carnage when they occur. The problem is that we usually don’t know they’re happening until they’ve already started. Unless we’re very lucky and already looking at a star when it explodes, we might miss the opening acts.
Getting our eyes on a supernova before it starts would allow astronomers to piece together a full picture of what’s going on and expand our understanding of the cosmos…and now we can. Scientists from Liverpool John Moores University and the University of Montpellier have recently developed a way to detect supernovae before they occur. Their method was published in the Royal Astronomical Society Monthly Notices.
To understand what they did, we must first understand how stars work and how supernovae form. When a star burns fuel in its core, it creates internal pressure that causes the star to expand. However, the star is also under the influence of gravity, which wants to pull all the mass towards the center. When the star is young or middle-aged and actively fusing fuel into its core, these two opposing forces reach a sort of balance that defines the size of the star. And it goes on for millions or billions of years, depending on the type of star.
At the end of a star’s life, it begins to run out of fuel to burn and the core begins to cool, reducing internal pressure. He also begins to accumulate material around him, almost as if he greedily gobbles up whatever he can find before the end. A last meal. This accumulation of material is important, and we will come back to it later.
Meanwhile, gravity is still pushing the star toward its center. If you’ve ever seen a can of soda in a vacuum chamber, you know what’s going to happen. Without the internal pressure, gravity overwhelms the star and it quickly collapses in on itself. The force of this collapse creates a shock wave that blasts parts of the star apart in a bright explosion. It’s a supernova.
If the star is even larger, at least ten times the mass of the Sun, the collapse will continue, leaving behind a black hole. Supernovae are among the most interesting phenomena in the universe, but until now they have been difficult to study in real time. We didn’t know when they were going to explode.
Astronomers have been waiting for years for Betelgeuse to finally die. The star, which appears in the night sky as Orion’s left shoulder, is expected to go supernova any day now. Of course, any day now in astronomical terms could be tomorrow or it could be thousands of years away. When it finally explodes, the explosion will be so bright you can see it in daylight.
We still can’t accurately predict when Betelgeuse, or any other star, will explode, but the process described in the Royal Astronomical Society paper provides an early warning system. The researchers found that massive stars nearing the end of their lives transition to a red supergiant phase. At that point, they start accumulating that material that we talked about earlier. So much material is attracted to the star that it blocks the light from the star from reaching us. During this phase, the star can become something like a hundred times fainter and could become so faint that in the days before the explosion we wouldn’t be able to see it at all.
These cocoons of material envelop the star for its final metamorphosis. The researchers looked at historical images of stars before they went supernova and found they hadn’t seen this phase or buildup a year before they exploded. This means that it occurs at most months before the explosion. It provides a window of time during which we can reasonably expect a star to burst.
Having a timeline for a star’s end-of-life process could allow astronomers to plan ahead for an upcoming supernova explosion. Rather than racing to capture images after the fact, we could point our telescopes days or months before the explosion happens and capture every moment of the process.
When Betelgeuse finally tears apart, chances are we’ll have a front row seat. Now we just have to wait for the lights to go out.
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