Happy Sunday, folks! I was cruising LinkedIn (boring!), when I read something that made me sit up. And so, an hour later, here’s a special Sunday post with some alt text about that Webb deep field.
A Thousand and One Words
The science world is buzzing about the new James Webb Space Telescope images, but what about my blind and low vision colleagues? I’m working on a project with some blind students to design 3D prints, but - have you all read the alt text with the photos, too? Fortunately, they’ve released some! You know I’ve got to get involved, too.
As a sighted writer and astronomer, I had missed this part of the interpretive process. Time to fix that! Turning towards the cliché “A picture is worth a thousand words”, I’m setting out to deliver even more - call it Project A Thousand + One.
I’ll rave about sights in the telescope, describing faraway stars and impossibly remote galaxies. My friends will get pumped, wanting to see this glittering universe, and…are usually relatively disappointed by the sight. Sometimes the interpretation is just as important as the sight. In this case, let’s see how it works. Buckle up - in exactly a thousand and one words, here’s my alt text of the deepest view of the Universe yet.
Setting the Scene: SMACS J0723
The photo background is jet black. Innumerable blurs of light, each one a distant galaxy, swarm around like gnats. Some are white, others blue, red, orange, or even greenish. Eleven stars, one especially bright, shine like spiky diamonds, or a kid’s jax. The design of the telescope adds this artifact, and they look vaguely like a ninja would throw them as a weapon. The six main spikes, and two tiny ones - look sharp - dangerous - like you’d cut yourself on them, or break them if handled. In the center, there’s a bigger, brighter blur. This is a group of galaxies that are closer to us than the small dots in the background. Strangely enough, some of the tiny galaxies that appear near the big blur seem warped and bent. This is a key point. We’ll get to it soon.
Getting a Feel for It
Let’s get involved with this with a silly example. I’m always hungry, so food is a great example for me. I went to the cupboard, and put a spoonful of uncooked brown rice on a dinner plate.
Spreading out the rice evenly over the plate, I was met with something that partly resembled the image. There’s a few limitations: Rice grains are roughly the same size, and the galaxies have variety in the photo. Their apparent dimensions range from a speck of rice dust, up to peas. The big galaxy in the middle would be a dollop of mashed potato. Again, strangely, the grains of rice near the mashed potato seem warped.
I realize this sounds like a kids’ game, but for me, I’ve never outgrown loving to eat, or the power of a simple example. Plus, if I can throw rice everywhere, it helps me cultivate the image of a mad scientist. Feel free to borrow the trick! We’ll get to the nuance in just a moment.
Audio Parallels
Another way to picture this is eating at a restaurant. A murmur of indistinct voices rumble and chirp in the background. (The distant galaxies.) You tap your fork and knife on your empty plate, waiting for dinner. (This would be the bright foreground stars - sharp, steely blue, bold.) Your aunt Mildred sits at the table and drones on about…something. It’s rather boring. (This is the indistinct haze that’s the closer galaxy cluster smack in the middle of the frame.) The waiter seems like he’s taking forever to bring the pizza. Fortunately, he won’t take 13.4 billion years, like the light from the most distant galaxy in this frame.
What is this?
Each “grain of rice” in this image is an entire galaxy. Up until the 1920’s, humanity thought the universe was contained in our own galaxy, The Milky Way. At a hundred thousand light years across, it was a big place. Space was about to get a lot bigger.
Edwin Hubble figured out that we were one of many galaxies floating in a much bigger Universe than previously comprehended.
Our nearest major galaxy neighbor is the Andromeda Galaxy, and that’s 2.5 million light years away!
I don’t know about you, but I get “sticker shock” easily, and lose track of big numbers. Here’s something I try to keep in mind when contemplating the Universe: One “light year” is the distance light travels in a year, which is roughly 5.88 trillion miles. To drive the same distance at highway speeds of 60 mph, it would take us over 11 million years to travel the same distance that light can traverse in 12 calendar months.
Back to the photo: each “grain of rice” on our silly plate example is an entire galaxy.
And then - dig the distance! The most distant galaxy in the photo was formed just 300 million years after the Big Bang, which is a cosmic blink. We are seeing parts of the Universe as it was at the dawn of time!
Space and Time - A Refresher
Remember, the farther away we observe, the farther back in time we go. Although light is fast, it’s not instantaneous.
Let us use the post office for our thought experiment: Should I mail you a letter Tuesday morning saying I just washed my car, and you live a day away, you’ll receive news of my car on Wednesday: as it was a day ago. If it rains Tuesday afternoon, and I send you another letter grumping about how it messed up the car wax, you’ll have to wait a day to learn of my petty misfortune. LIkewise, if those galaxies in the photo merged, were destroyed, zapped with a ray gun, or otherwise went through their natural evolutions…we won’t know for billions of years. We’re seeing them as we would baby photos of our distant ancestors.
Aunt Mildred’s Presence
Remember the mystery of Why do some of the grains of rice (galaxies) look warped?
Remember our restaurant example, where “Aunt Mildred” droned on in a bland haze? Is her presence in the room bending the social fabric?
What gives?
Gravitational Lensing
The cluster we’ve affectionately dubbed “Aunt Mildred” (my name, not NASA’s) is “nearby” - “only” 5.2 billion light years away. The immense mass of this group has caused the fabric of spacetime to warp and bend. As distant photons from the ancient background galaxies travel by, they are refracted (bent) and redirected towards us. The galaxy cluster distorts space, which ends up acting like a giant telescope lens.
Think of a bowling ball sitting on a trampoline. If you were to roll a marble across the surface, it would divert towards the depression made by the bowling ball. The same thing happens as a photon traverses space warped by a massive object…roughly speaking.
The “bent rice” is the distorted light from these lensed galaxies. Far out, man!
Cleaning up
Finally, remember this: when the light from some of these galaxies started its journey to reach us, some of the elements in the rice on your plate didn’t even exist. Now that’s tasty.