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As you may know, I’ve been writing for the magazine Scientific American since late 2022. When I was let go from SYFY I sent a note to my friend Laura Helmuth, who was my editor at Slate for several years, and who was the Editor in Chief at SciAm, asking if I could write for her on the odd occasion. She said yes, and it eventually turned into a weekly Friday column at first called “Over Your Head” but is now “The Universe”.

Why mention all this now? Because I just wrote my 200^th article for them. Yegads.

The article is called “The biggest explosions in the universe, ranked” and I discuss some of he biggest bangs in the cosmos. I joked with my editor, Lee Billings, that covering all of them would take a whole book (and it kinda did), so I only tackled a few. Some of them will get more attention in the coming weeks, too, since they’re so cool I wanted to dig into them more.

So head on over there and give it a look, please. And you can subscribe to the magazine, too; they frequently have discounts running. It’s the oldest continuously printed magazine in the US, and there’s a reason for that. Science! We all love this stuff.

I recently wrote about the Ring Nebula, a planetary nebula with a mysterious structure across its middle.

Today, let me tell you about the iconic Helix Nebula, another magnificent gas cloud that has also been very well studied, but now new JWST images reveal absolutely staggering detail in it.

Staggering, and also slightly unsettling.

First, here’s a Hubble image (plus some ground-based observations) from a few years ago to get your bearings.

Gorgeous, ain’t it?

The Helix is a planetary nebula, gas blown off the upper layers of a dying red giant star (if you want details you can read that Ring Nebula article, and I also have an episode of Crash Course Astronomy talking about how stars turn into red giants, and another on what happens after to create the nebulae). It’s roughly 650 light-years from us, which is pretty close! At two light-years in diameter, it’s pretty big as seen from Earth, almost as large as the full Moon in the sky. Its light is spread out making it rather faint, though; I’ve looked for it many times with my own ‘scope but I’ve never managed to see it.

The structure is layered. The outer part was blown off by the star when it was a red giant. As those layers of the star peel away, hotter and hotter material below them, deeper inside the star, are exposed. Eventually this creates a faster wind of material that catches up to the slower red giant wind and slams into it. The old wind is denser than the new one, which sets up a weird situation.

Any denser clump of material in the old wind gets hit by the new wind, but because this new wind is lower density, the clump doesn’t immediately get destroyed or blown away. Instead, the new wind erodes it as it flows past and around the clump. What you get is similar to a sandbar in a creek, when water flows around a small pile of sand, sculpting it into a teardrop shape. The water flowing around creates a wake called a bow wave, since it’s like the wave of water seen as a ship moves through water.

This is happening in the Helix! A lot.

There are hints of it in the Hubble image, with hundreds of long, narrow structures visible in the ring itself that point toward the center, where the dying star is. The material is coming from the star, from the center, so the structures all point that way. These are sometimes called fingers, but more technically cometary globules; “globules” because they’re, well, blobs of denser dust and gas, and “cometary” because the material flowing past and off them resembles a comet’s tail.

OK, that’s the background. Ready? Here’s the JWST image:

Whoa.

The JWST image shows one small part of the nebula; the bright star at the top center is the one at about the 4 o’clock position just inside the inner edge in the Hubble image. But, while the Hubble image is mostly smooth with a few dozen fingers seen, with JWST you can see thousands, and that’s just in one small section! 

One estimate based on previous observations is that there are about 40,000 such structures in the Helix! Holy wow.

There is a very high-resolution version of the JWST image available (11,000 x 8,000 pixels), which is a truly amazing thing to peruse. Here is one tiny section of it, which I took from the upper left part of the frame:

Yeah look I’m not too embarrassed to admit this is somewhat ookie-looking to me. Biological, almost, like some weird sea creatures aligning with the current.

…which isn’t too far off, in a sense. They are aligned, pointing toward the central star (“upstream”, if you will). Some of the globules are loners, and others come in packs, likely starting off as a larger clump that eroded into a tight-knit clot of smaller ones all shoulder-to-shoulder. They’re brightest at the tips, because that’s where they’re densest, and that’s getting the full brunt of the radiation from the central star, which is mostly ultraviolet light that also helps erode the globules.

There’s one at the top left, shaped kind of like a gun, where you can see the arc-shaped bow wave of material flowing around it, too.

There’s a term for all this: the Rayleigh-Taylor instability. This is when a lower density fluid pushes on a higher density one, just as in the nebula. It’s common in nature. In astronomy it happens pretty much whenever stars blow out winds; the faster (more energetic) the wind, the longer the fingers get, like in WR 124.

I’ve never seen such detail in them before, though. The colors are important, too. These are all in infrared, and invisible to the eye, but we can use filters and color them artificially to show the different wavelengths involved. What you see as blue is from warm hydrogen (it permeates the bottom left part of the wide image), while green and red show cold molecular hydrogen gas (H₂). Different atoms and molecules emit different colors of light, and respond to temperature and density differently, so images like this help us understand the physics going on in various parts of the nebula.

Incidentally, in the Ring article I mentioned that planets orbiting the dying stars can affect the nebula; it turns out there’s some evidence that the white dwarf at the center of the Helix is tearing apart and dining on the pieces of a former rocky world as well [link to journal paper]. I love stuff like this; the earliest known evidence of the existence of exoplanets was a spectrum taken in 1917, from a white dwarf that just ate asteroids or a destroyed planet, so there’s a long history of such things.

On top of all this, planetary nebulae are just cool and beautiful, and some of my very favorite astronomical objects. I got my Master’s Degree studying one, and my PhD studying another that was a variation on the theme. When I take my ‘scope out I still always look for one or two that happen to be up.

The Helix is a late summer/early fall object, in the constellation of Aquarius. It doesn’t get very high here in Virginia, but maybe later this year I’ll take a stab at it once again. It’s a good reminder that these bizarre objects I write about are real, they can be seen, and they can also be studied and appreciated. That’s always a nice thing to keep in mind.

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!