Learn about why Wolf-Rayet stars are the brightest stars in the sky; why immune cells in your brain may have started out in your gut; and the history of why we can thank Grace Hopper for calling computer glitches “bugs.”
Learn about why Wolf-Rayet stars are the brightest stars in the sky; why immune cells in your brain may have started out in your gut; and the history of why we can thank Grace Hopper for calling computer glitches “bugs.”
Wolf-Rayet Stars Are Ridiculously Hot, Bright, and Massive by Ashley Hamer
Immune cells that protect the brain get their training in the gut by Grant Currin
Why glitches are called "bugs" by Mae Rice
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Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/why-we-call-computer-glitches-bugs
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about the brightest star ever; why immune cells in your brain may have started out in your gut; and why we call computer glitches “bugs.”
CODY: Let’s satisfy some curiosity.
What's the brightest star in the sky? Trick question: to us, it's the sun. The brightest star in the night sky, though, is Sirius, known as the "Dog Star." But what about the brightest star ever? That honor goes to a really, really massive celestial object called a Wolf-Rayet star [Wolf Rye-A like Apex, 1:15] OR [1:05 “wolf array” stars https://www.youtube.com/watch?v=REHJvW53G54]. Our sun may be bright, but it's got nothing on these things.
Wolf-Rayet stars don't start their lives as the universe's brightest, but they are born big. They start out at least 20 times as massive as our sun — and that's where the trouble begins. See, just like you need to digest food for energy, stars need to fuse elements to keep on shining. For our sun, that means fusing hydrogen, the lightest element, into helium, the second lightest. Bigger stars fuse those into even heavier elements, from carbon to oxygen all the way to iron. Ideally, all the energy blasted outward from that fusion is balanced by the star's gravity pulling inward, and the star can happily survive for billions of years.
But if a star is big enough, that process goes a lot faster. As a Wolf-Rayet star runs from heavier element to heavier element, the energy it creates starts to exceed the gravity it takes to keep everything together. This energy is what makes Wolf-Rayet stars so hot and bright: they burn 10 times hotter and shine millions of times brighter than our sun. But that energy-gravity imbalance leads to intense winds that strip away the star's outer layers.
As the star loses elements to the universe, it starts to run out of stuff to fuse. Once fusion stops, there's no more outward pressure, and the only force left is the squeeze of gravity. At that point, it explodes as a supernova and its core implodes to become a black hole.
But there's a happy ending to this story. The high-energy winds that blow off the star's outer layers? They carry newly fused elements out into the universe, where they can play a role in the formation of everything from new celestial objects to life itself, yours included. Every element in your body was fused in the core of a star. I know we just dropped this Carl Sagan quote a few weeks ago, but it bears repeating: we're made of star stuff. Cosmic, isn't it?
Your immune system has got your back. And your butt. And your brain. Now, surprising new research shows how some immune cells get training in the gut before shipping out to protect the brain and spinal cord from pathogenic invaders.
The nervous system is very, very important. It’s also pretty vulnerable. But there’s usually no need to worry because the immune system works really hard to those sensitive sites from ne’er-do-well viruses, bacteria, protists, fungi, and *sigh* parasitic worms. (Yeah, brain worms are a thing.) All of those intruders are constantly trying to figure out how to slip past the immune system and invade the nervous system, where they can finish their life cycle and reproduce.
One place where they have a better-than-average chance of getting through is the network of veins that carry blood from the brain back to the heart. This is a potential vulnerability for two reasons. First, those veins are really close to the brain, and second, the blood in these veins doesn’t move very fast — it’s basically a lazy river that slowly drains into the heart. That makes it easier for pathogens to accumulate and work their way into the brain.
That all sounds scary, but the immune system is very good at what it does. That’s why when researchers looked closely at the immune cells patrolling that neck of the woods, they expected to find some fascinating defensive strategies. And boy, did they.
What they found were immune cells typically associated with the mucous membranes that surround the gut and the lungs...but these immune cells were in the brain. Specifically, in the outer layer of the meninges — that’s the three-ply envelope of connective tissue that surrounds the brain and protects it from pathogens. These immune cells are called Immunoglobulin-A or IgA cells, and they’re trained to produce antibodies against particular microbes. And the researchers suspected that they got that training in the gut.
To find out, they compared the IgA cells in regular mice to those in germ-free mice, which are raised in clean environments so their guts don’t contain any microbes. The germ-free mice had almost no IgA cells in their meninges! Then the researchers took some of those germ-free mice and carefully built their gut microbiomes from scratch. And wouldn’t you know it, IgA cells showed up in their meninges! That all suggests that microbes in the gut play a critical part in developing immune cells that protect the brain.
As the final smoking gun, the researchers compared the DNA in IgA cells in the gut with DNA from IgA cells in the meninges. The two shared a ton of genes, which suggests that they’re very closely related. This is just the beginning of research into IgA cells in the meninges, but even this early work shows that the body is doing some pretty cool things to keep the brain safe.
And one of those things seems to be immune cell boot camp in the gut. Well done, soldiers.
CODY: Chances are, you haven’t listened to every episode of Curiosity Daily ever. I mean, there are more than SEVEN HUNDRED of them. So once a week, we remaster one of our favorite classic clips, to help you satisfy your curiosity. Here’s a gem from 2018.
Let’s do a quick recap of what we learned today
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CODY: Today’s stories were written by Ashley Hamer, Grant Currin, and Mae Rice, and edited by Ashley Hamer, who’s the managing editor for Curiosity Daily.
ASHLEY: Scriptwriting was by Cody Gough and Sonja Hodgen. Today’s episode was produced and edited by Cody Gough.
CODY: Join us again tomorrow to learn something new in just a few minutes.
ASHLEY: And until then, stay curious!