Betelgeuse… Betelgeuse… Betelgeuse

Published 12:30 pm Thursday, August 14, 2025

The star Betelgeuse (not to be confused with the movie Beetlejuice) is close to exploding — and its supernova will be visible from Earth, even in daylight.

That sounds very exciting. And it would be. Currently, Betelgeuse, the constellation Orion's left shoulder (as viewed from Earth), is the 10th (actually 11th, but we'll get to that later) brightest star in the sky.

For the three months, or so, its supernova would be visible, it would be the brightest (actually second), about as bright as the half moon.

A cosmic spectacle to be sure, likely to produce pilgrimages of wisemen.

I can't wait. Literally. Because, when astronomers say 'close', they don't mean it in the way that we normal humans tend to take it.

In this case, close means, given their best estimates, within the next 100,000 years. Let's put that in context. We generally think about recorded human history as being around 5,000 years. That's a lot of history, but it's only one-twentieth of how long it might be until Betelgeuse explodes.

Or it could be tomorrow. And by tomorrow, I mean 640 years ago.

In fact, if we are to see it in our lifetimes, it had to have already happened around that long ago because the star is around 640 light-years from Earth. The instability scientists are seeing today, which leads them to believe the star's demise is imminent (astronomically-speaking) actually happened in the late 14th century.

Betelgeuse (was that three times?) is a very interesting star. A red supergiant, which is only about 10 million years old. Compare that to our sun (a yellow dwarf), which is already close to five billion years old and is expected to last another five billion before it too goes supernova.

Why so short-lived Betelgeuse?

It's just so massive, it is burning through its fuel very rapidly (also astronomically-speaking, of course). 

How massive? Oh, baby! If it were at the centre of our solar system, it would encompass the orbits of Mercury, Venus, Earth, and Mars with its surface being near the asteroid belt between Mars and Jupiter.

I know, right? It is really hard to fathom something that big.

And while we are talking about our G-type main-sequence star, let's go back to the relative brightness question. For some reason, even in official rankings, our star, clearly the brightest thing in the sky, doesn't rank first. 

As near as I can tell, it's a mathematical convention in which the Sun is the 0th (zeroth) element in a sequence that includes the relative brightness, from Earth, of all the countless stars we can see and, of which, Betelgeuse is number 10. 

Imagine that, our modest little planet, the centre of the universe. Maybe things haven't really changed that much since the 14th century.

Mathematically, it makes sense, but in layperson terms, the brightest is number 1, making Betelgeuse number 11, but at some point it will temporarily be number 2.

Not that I wish Betelgeuse any ill will, but I really hope it has already exploded. That supernova would really be something to see.