Theres a well-known star that I am certain you have seen within the sky. Its identify is Betelgeuse, and you’ll find it within the Orion constellation, the place it marks Orion’s proper shoulder. If you wish to name it “Beetlejuice,” I am positive with that as long as you do not say it 3 times.
However one thing is happening up there. This pink supergiant has dimmed repeatedly prior to now few years, which may imply that it is able to go full supernova fairly quickly—and by “quickly” we imply throughout the subsequent 10,000 years. Really, because it’s some 500 light-years away, it is doable that it already exploded and we simply do not know it but. It may present up tomorrow.
One factor’s for certain: If Betelgeuse does blow, it is going to be the brightest supernova ever witnessed by people. Simply how shiny are we speaking? Might you see it through the day? Would it not be harmful? I will present you easy methods to determine all this out with just a few very fundamental physics.
What Is a Supernova?
In most stars, the core consists of hydrogen and helium, the 2 lightest components—however solely the positively charged nuclei of these atoms, because it’s too scorching for the electrons to remain put. Underneath immense gravity and temperatures, these nuclei can fuse into heavier components, releasing large quantities of power within the course of. (This nuclear fusion is the place our solar will get its power.)
For a steady star like our solar, there is a stability between two opposing forces. The mass of all of the matter within the star produces a gravitational power that tends to break down the star. Nevertheless, that is countered by the outward-pushing power from the core, so the star stays pretty fixed in dimension, although it is not a strong object like a planet.
However as a star ages, it progressively makes use of up its hydrogen and helium and begins producing heavier components like carbon, oxygen, silicon, and eventually iron. And that is so far as it goes—fusing components heavier than iron takes power as a substitute of making it, so the star basically runs out of gas and collapses in on itself.
In some circumstances, this collapse might be very extreme—so extreme that it quickly will increase the stress and temperature within the core of the star. The star then goes growth. Big boom. Properly, large silent growth, since explosions make no sound within the vacuum of house.
However this produces A LOT of sunshine power. For comparability, our solar has a luminosity, or power output, of 3.8 x 1026 watts. A supernova that was observed in 2015 (ASASSN-15h) had a peak luminosity of round 2 x 1038 watts. That is extra energy output than 500 billion suns. It is loopy. Oh, you did not see that one? Yeah, as a result of it was in a special galaxy. Betelgeuse is in our again yard, astronomically talking.
Brightness and Luminosity
A very long time in the past, a Greek thinker named Hipparchus categorized the celebs into six teams, primarily based on how shiny they appeared within the night time sky. From that, we’ve got developed a classification scheme for “obvious magnitude,” such {that a} star of magnitude 1 seems to be very shiny, whilst you most likely cannot even see a magnitude 6 star via mild air pollution. Betelgeuse is within the first group.
To be clear, this is not the precise luminosity of a star—it is how shiny it seems from Earth, which relies on (1) how a lot mild it produces and (2) how far-off it’s. Oh, additionally (3), magnitude is predicated on how the human eye sees objects, and it is not linear. A magnitude 1 object has a light-weight depth (in watts per sq. meter) that’s 100 occasions larger than a magnitude 6 object.