Welcome to Issue #1068 of the Bad Astronomy Newsletter! Now, for normal people, that number doesn’t necessarily have a special meaning. But for astronomy dorks it does: NGC 1068 is one of the most studied galaxies in science. By coincidence, astronomers released a totally amazing image of the galaxy taken by JWST just a few months ago. I almost wrote about it right away, but then realized I could save it for today’s issue because why not. Yes, I’m a math dork too. I contain multitudes. So here you go.

If you’ve ever wondered why astronomers always want more telescopes that cover different parts of the electromagnetic spectrum, then you really need to see the JWST image of the nearby spiral galaxy M77.

OK, even if you haven’t asked yourself that you still really need to see the JWST image of the nearby spiral galaxy M77.

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M77, aka NGC 1068, is pretty close to us as spiral galaxies go, about 45 million light-years away (so, closer than galaxies in the Virgo Cluster, for example). That means we can see it in great detail, especially with big ‘scopes like JWST.

You can see the galaxy itself in blue — though it’s not really blue; it’s actually infrared light at a wavelength of 7.7 microns, ten times longer than the reddest wavelength your eye can see, but just colored blue here so you can see it. And what you’re really seeing is dust, long chains of carbon-based molecules that are nothing if not soot. Dust is created in dying massive stars (think Betelgeuse) and blown out into space to create huge clouds. These massive stars are born in spiral arms, and die in them as well, so we see the dust clouds strung out along the spirals of galaxies like this one.

In red, though, we see something else entirely (the huge spikes going through the center are not real, but are called diffraction spikes, caused by the optics inside the telescope; they can be irritating for astronomers since they interfere with the object but dang, they’re cool looking). This is light at the much longer wavelength of 21 microns, and that’s important, because the longer the wavelength of light, the easier it is to get through dust clouds. In visible light, for example, a bright star behind a dust cloud might be completely invisible, but at 21 microns the light passes right through so we can see it. 

What you’re seeing here is dust heated in the center of the galaxy, and I do mean the very center. Because sitting there at the exact center of M77 is a supermassive black hole that weighs in at many millions of times the sun’s mass. There’s one called Sgr A* at the center of the Milky Way as well, but M77’s is twice as hefty, and also unlike ours is very enthusiastically gobbling down matter around it.

As this material falls into the black hole it forms a huge disk called an accretion disk, and friction causes the matter in it to get infernally hot. Between the temperature and size of the disk, this makes the center of the galaxy blast out light across the EM spectrum, easily outshining all the light from all the other stars combined.

But — and this, like Peewee’s friends, is a big but — surrounding that disk at a distance of a few light-years is a massive torus (donut-shape) of thick dust. Dust like this is opaque to visible light, so it swallows up even the immense brilliance of the accretion disk’s emission. In visible light we see nothing at all! But in the far-infrared the dust, heated by the accretion disk, glows brilliantly (note too that we don’t even really see it well at 7.7 microns, or else there would be a lot of blue mixed in with the red).

If you don’t believe me — and I wouldn’t, since that sucker is obviously booming out light in the JWST image — here’s a Hubble Space Telescope image (rotated to the same orientation) taken in ultraviolet, visible, and near-infrared light (just barely outside what he human eye can perceive, so nowhere near as long a wavelength as the JWST image):

See what I mean? That image is spectacular, but there’s no hint of the ridiculously powerful lighthouse in the core. All that light is blocked by the thick dust. It looks like a rather typical, if gorgeous, spiral galaxy.

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