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You should all know Judy Schmidt’s name by now. I have linked to his work several times here on the blog; she’s an image processing assistant, taking raw images from Hubble and turning them into ridiculously beautiful art.
There is also science there, like a strange nebula that she and I tried to discover in a nearby galaxy. We never really came to a conclusion about it, but sometimes what she does leads not only to science, but to a scientific publication.
And in this particular case it started with a tweet:
This is a Hubble image of the neighboring galaxy sort IC5063, about 160 million light-years away. It’s a galaxy of disks, although it’s hard to tell in this picture. What Judy was trying to see are what rays of light emerge from the center, very faint, just barely above the background levels of the image.
Many astronomers are following her and a conversation has started (click on the tweet above to see the whole thing). Dr Julianne Delcanton suggested they look like ionization cones: intense light from the center of the galaxy explodes and zaps gas around it, creating glowing luminous triangles in the images. We all agreed that it looks like this (especially after Bill Keel processed the image to improve the rays), then, after Judy asked if they could be shadows, one of us (cough cough) suggested that they look like crepuscular rays: Opaque elements in the center of the galaxy block light in some directions but not in others, so you see bright and dark rays unfolding, like rays of light from the setting sun (twilight means relating to twilight).
Astronomer Peter Maksym entered the thread… and now here we are, less than a year later, and he posted an article on this image (with Judy listed as co-author)!
IC 5063 is what we call a active galaxy: Like all large galaxies, it has a supermassive black hole in its core, but in this case, the material falls into the black hole. A lot of material, and it forms a large accretion disc which can extend just beyond the point of no return several hundred light years away. This record is extremely hot and therefore incredibly bright. In some active galaxies, it can easily outperform all the stars of the galaxy combined.
On the outside of the disc is a much larger dust torus (donut). Usually this is all aligned with the large flat disk of the galaxy itself, but not always. In the article, they argue that the torus is significantly tilted relative to the galactic plane, and it is the torus that casts these shadows.
If the torus was not there, the whole galaxy would have a spherical glow around it due to the intense light from the internal accretion disk illuminating the dust around the galaxy. But the torus blocks some of that light and we shadow it as dark rays rising from the center (so the speculation in the Twitter feed about ionization cones is pretty close to being correct). This may be due to uneven dust clumps in the torus, which is why light may come out in certain directions.
I will note that this is what the authors consider the likely explanation. Other ideas have been considered but are less likely, such as bright rays being stars in X-shaped orbits (which has been seen in galaxies before, including ours), but given that the IC 5063 is active, I would bet on this phenomenon being related to this.
Incidentally, given the distance to this galaxy, these rays reach about 35,000 light years! It’s a long way.
This idea of the shadow of the tori had been speculated for some time, but never seen before. This is therefore a first! And all because Judy loves processing Hubble images, saw something funny and decided to release it to the community on social media.
So, from now on, I’m going to use this as an excuse to read Twitter. Well, I’m not kidding. I do pre-science!
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