BAN #389: Another banner new year

3 January 2022 Issue #389

January 03, 2022

Blog Jam

[The spectacular comet C/2021 A1 (Leonard), currently gracing the southern skies. From Wednesday’s article. Credit: Dr. Sebastian Voltmer | http://astrofilm.com]

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it

[I never know whether to make this more-or-less annual section Pic o’ the Letter, Astro Tidbit, or About this Newsletter, and then I remember it doesn’t matter, and by explaining that I’ve already covered my bases anyway.]

Happy 2022!

As I sometimes like to do, I’ve changed my banner above to reflect a new year, and new things to say.

If you missed it, scroll up. Or instead, just look here, because here’s the full version of what I’m now using with my name and BAN defacing it:

And also, as I sometimes like to do, I’ll explain what you’re seeing, because it’s very very cool. And there’s a surprise hidden in it in plain sight, too.

That is the star-forming region NGC 3603. It’s about 20,000 light years from Earth in the constellation Carina, and it’s a big one, roughly 75 light years wide. That’s three times bigger than the Orion Nebula.

It comes complete with a cluster of young stars that recently coalesced from all that gas and dust — the age is estimated as about a million years. The cluster is a beast, with thousands of stars in it, dozens of which are classified as O-type, the highest mass and most luminous stars. The biggest in the cluster are well over 50 times the mass of the Sun, among the most massive stars known and the most massive even possible.

I love this Hubble image. Years ago my brother-in-law asked me what my favorite Hubble is, and I told him this one. Then, for my birthday, he printed a big version of it and framed it for me. I’ve had it in my office for years.

The obvious beauty and measured power of this nebula and cluster are not why it’s my favorite, though. Take another look at the image; see that one really bright star to the upper right of the cluster center? It’s surrounded by some blue fuzz. Here’s a closer view:

That star is called Sher 25, the 25th entry in a stellar catalog by astronomer David Sher. It’s a blue supergiant, a bruiser with something like 60 times the Sun’s mass. It’s dying; some time ago it stopped fusing hydrogen into helium in its core and is now fusing heavier elements into even heavier ones. It may have once been a red supergiant like Betelgeuse (though more massive and larger) but stars like this can change color as their cores step through ever-heavier elemental fusion.

Here’s the very cool part though. That blue fuzz of gas near the star takes the form of a ring around it, clearly tilted to our line of sight so that it looks like an ellipse, and two caps of gas above and below the ring’s long axis. In the first Hubble image of this object the gas isn’t obvious, but in this one, which includes filters that emphasize hydrogen gas, it’s more easily seen.

I remember that when I first saw this image showing the gas I gasped out loud: It’s a near twin of the structure around the ex-star Sanduleak 69-202, the star that exploded to become Supernova 1987A. That star had three rings around it, part of an hourglass-shaped nebula. The gas was blown out by the star as it began dying, and when it exploded it lit them up for all to see.

[Rings of gas around the exploded star Supernova 1987A, which is the blob in the middle of the central ring. I studied this object for my degree. Credit: Jason Pun (NOAO) and SINS Collaboration]

I studied Hubble images of SN 87A for my PhD, and knew immediately this was a similar structure. That in itself was amazing; at the time no other such hourglass nebula had ever been seen around a massive star. As it happens the one and only journal paper I ever refereed as a scientist was about Sher 25 and its peculiar nebulosity. It has details about it that make it clear we’re seeing something very similar to SN 87A.

Sanduleak 69-202 ejected its gas and then exploded about 20,000 years later. Sher 25 is more massive, and therefore shorter lived. So it’s a pretty easy prediction to make that it has much less than 20,000 years left to go before it too goes kablooie. That paper linked above indicates the gas is likely already 9,000 years old.

People always ask me when Betelgeuse will explode, and think it’ll be soon. It probably won’t be for 100,000 years, though. Sher 25 will go long before that. At 20,000 light years away it’ll outshine Venus when it does, but it’s a southern hemisphere star, so we won’t see it from the north. And by “we” I mean likely a few generations removed from now, but still.

And now you know why it’s my favorite, and why I chose it for my banner. I wanted something of great beauty and scientific interest, of course, but also something personal. I spent a long time in grad school looking through literature for other objects like SN 87A’s three-ring circus, and only found a couple that resembled it, and those were for low-mass stars. Then this fell into my lap, and while I never did research on it myself, it was a phenomenal feeling — relief, joy, amazement — that other objects like the one I had spent so long studying definitely existed.

So: Happy New Year, and may you too find the pot of gold at the end of your rainbow, the treasure at the spot marked X, or a several-light-year-long nebula that confirms your suspicions.

P.S. I wrote articles about some previous banner images, like the one of planetary nebula M 2-9, and the gorgeous spiral galaxy M81.

Et alia

You can email me at [email protected] (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Reply

or to participate.