In recent days, I’ve noticed a flurry of online activity concerning one of the stars I am studying, Betelgeuse. Perhaps you’ve heard? It began dimming back in late 2019, and is still dimming as of this writing, although the rate of dimming appears to have slowed.
It also appears to have become distorted, as a new image from ESO reveals.
Betelgeuse is an M class star, a true red supergiant. Type M stars have a low surface temperature, in the case of Betelgeuse, around 3,600 K (6,020 Fahrenheit). That may sound like a lot, and it is, but keep in mind our own Sun has a hotter surface temperature of around 5800 K (Type G star). Betelgeuse is a lot more massive than our Sun… actually there is some uncertainty here because the star does not have a direct companion and so direct measurements using Newton’s Laws are impossible (we need to be able to look at an orbital companion in order to tease out its mass, and Betelgeuse currently has none). We must resort to indirect measurements and there is a slight disagreement among astronomers. The truth is Betelgeuse could be anywhere from 11 to 20 times more massive than our Sun. This is one of the things I am investigating for my own scientific work (Master’s Thesis).
Betelgeuse is definitely much larger than the Sun, with a radius extending out past the orbit of Jupiter! If Betelgeuse was switched with our own Sun, the Earth would be well inside of it. Thanks to its large size, it is around 150,000 times brighter (more luminous) than our own Sun.
Or at least it was until it started dimming! Betelgeuse was on the list of 20 brightest stars in the night sky, until now… it has dimmed more than a full magnitude (astronomers use a logarithmic magnitude scale to measure the brightness of a star), knocking it off the list at least for the moment.
This has prompted speculation that Betelgeuse is about to explode! And although most astronomers (mainly due to simulations and theory) believe Betelgeuse will not go supernova for at least another 100,000 years, this still remains a possibility. It is a possibility I am investigating with my thesis work.
Fear not, dear reader, if indeed Betelgeuse does explode tomorrow, at a distance of 642 light years, it is more than far enough away for it to be safe for us. The minimum safe distance for a typical supernova is between 30 to 100 light years (depending on several factors). Anything above 100 light years and you’re totally safe. So do not worry.
There is a particular type of supernova, called a hypernova, which would not be safe at that distance. Hypernovae are very energetic, an order of magnitude more powerful than regular supernovae, caused by the collapse of very massive stars (greater than 30 times the mass of our Sun) into black holes. They usually send out ridiculous amounts of energy in two twin jets emitting from the polar regions of the collapsar (collapsing supernova). If you’re in the path of one of these jets, especially, you’re cooked (and your planet with you). For these hypernovae, you’d have to be at least 1,000, maybe even as much as 10-20,000 light years away in order to be truly safe. Thankfully, Betelgeuse is not massive enough to turn into one of those. We’re in the clear.
If Betelgeuse does go supernova, it will light up the night sky, perhaps slightly brighter than the full Moon. It will truly be a sight to behold. 😊
Incidentally, the original Arabic name of this star (as it was discovered by an Arab astronomer) was Yad al-Jauzā’, or “the Hand of al-Jauzā’”. No one is quite sure who al-Jauzā’ is… could have been an ancient king or dragon or some other mythical figure. Yet over the centuries, scholarly errors crept in as the name was repeatedly written down and mistranslated to become… Betelgeuse!
My suggestion is to go out, if the night is clear, and take a look at beautiful Betelgeuse while it is still up there in the constellation Orion. Soon enough summer will be here, and Betelgeuse will be setting beyond view… perhaps for the last time?
This image is a colour composite made from exposures from the Digitized Sky Survey 2 (DSS2). The field of view is approximatelly 2.0 x 1.5 degrees.Credit: ESO/Digitized Sky Survey 2. Acknowledgment: Davide De Martin.