[Of course I picked this one to highlight because the title made me laugh. From Tuesday’s article. Credit: S. Safi-Harb et al (2022)]

A brief synopsis of some interesting astronomy/science news

I also mentioned it had a supernova in it, called SN2021 afdx. And I have to say, when I first saw that designation I actually muttered an obscenity or two under my breath.

Why? Because it’s all in the name.

Way back when, supernovae — exploding stars — were named after the year they were seen, or maybe given the name of the astronomer who described them. That’s how we get Tycho’s Supernova, and Kepler’s Supernova, which are also called SN 1572 and SN 1604 since that was the year they were seen.

That was fine when naked eye supernovae occurred once a century or so. But then we did something irritating: We invented telescopes.

To compound that we also invented photography, allowing long exposures to reveal fainter objects. And suddenly instead of once a century astronomers were seeing several supernovae per year, occurring in distant galaxies to faint to have been seen earlier!

So we developed a naming system to minimize confusion. A supernova would be designated by the letters SN and the year it was found, and after that would be given a letter alphabetically in order of discovery. That’s why the first supernova in 1987 was called SN1987A — and it turned out to be one of the most important supernovae of all time, since it was in a nearby galaxy and was heavily studied. It was also the first (and so far only) one ever detected via neutrinos.

Anyway, the second supernova seen in 1987 was 1987B, and the third 1987C, and so on. If, in a given year, more than 26 supernovae are seen, then the 27th is given the year plus the letters aa (yes, A-Z are capital letters but then the ones after are lower case, because astronomers are nothing if not maddening even when trying to codify naming conventions logically), the 28th would be ab, etc. The 52nd supernova of that year would be az, and so the 53rd would be called ba.

If, at some unlikely point in the future, the naming convention people reasoned, we actually found 26 + 26 x 26 = 702 (26 for the single letters, then 26 x 26 for all the doubles) supernovae in a single year (like that would ever happen) then the 703rd would be SNXXXXaaa. Und so weiter.

Flash forward a few years. Our telescopes and cameras are not only way way better than they used to be, we now have robotic telescopes surveying huge chunks of the night sky automatically and software that analyzes the images looking for things that change from night to night, like, say, a supernova getting brighter. They discover a lot of supernovae that way.

And that brings me back to the Cartwheel. The supernova found in it was seen in late November, so there was nearly a whole year’s worth of explodey stars seen before it.

And it’s designated SN2021 afdx.

That means a whole lot of supernovae were seen that year before it. How many?

Yeah, there’s math. 26 for the single letters gets you to z, and 26 + (26 x 26) = 702 gets you to zz. That means 26 + (26 x 26) + (26 x 26 x 26) = 18,278 gets you to zzz.

Still with me? The next one is aaaa, and that would be the 18,279th. To get to abaa would take 26 x 26 more, or 18,955. You have to do that four more times to get to afaa, or 18,955 + 4 x 26 x 26 =  21,659. You have to go through all 26 letters three more times to get to afda, or 21,659 + (3 x 26) = 21,737. Then finally, 23 more letters to get to afdx.

That means — assuming I did this math right, and I have maybe a 50/50 chance of that — SN2021 was the 21,760th supernova seen in that year*.

Twenty-one thousand seven hundred and sixty. Wow. That’s a whole lotta stars blowing up.

And that is why I swore when I saw the Cartwheel supernova’s designation. 21,760! In one year. That number is so high I thought I must be wrong, but I found this page that calculates the totals, and it says there were 21,081 supernovae seen in 2021. These are candidates, actually, only some of which are confirmed, and so many are seen every night that the discrepancy between 21,081 and 21,760 is understandable — probably just a cataloguing issue.

The point being, we are now finding tens of thousands of supernovae every year!

That’s the 54th day of the year, and it was the first one seen.

November 23, 2021 was the 327th day of that year. If we take 21,760 as the total seen by then, that means there were, on average, 66.5 supernovae seen per day in 2021. By February 23 of that year, that average works out to 3,593 supernovae. That’s somewhere in the low-to-mid triple letters.

If you want to know how much astronomy has improved in just 35 years, look to supernovae. We went from seeing one star explode by February 23, 1987 to well over 3,000 in the same amount of time in 2021.

I’ve seen a lot of numbers estimating the number of supernovae per galaxy per century, and there’s a big spread, but let’s say it’s one per century per galaxy. There are possibly 2 trillion galaxies in the Universe, but that includes small ones with much fewer stars, so let’s again wave our hands and say there are 100 billion galaxies, averaging over size. That’s one hundred billion supernovae per century, or a billion per year, or about 30 per second.

THIRTY SUPERNOVAE PER SECOND, over the entire observable Universe.

Cripes. We’ve come a long way observing them, but there’s a helluva long way to go.

* Another way to think about it: Going through single letters takes 26 supernovae. Going through the double letters takes 26 x 26 or 26^2, and triple letters 26^3. To get to “f” in the quadruple letters means going through the double letters 5 times (aaaa – aezz), getting to “d” means going through the single letters three times, and “x” is the 24th letter, so the equation iszz), getting to “d” means going through the single letters three times, and “x” is the 24th letter, so the equation is

26 + 26^2 + 26^3 + (5 x 26^2) + (3 x 26) + 24  = 21,760

P.S. My thanks to my friend and fellow supernova-studier Sarafina Nance for indulging me in a conversation about this.