LMR-020 · Galaxies
Galaxy
A herd of a hundred billion stars, held together by gravity and dark matter.
§ A first look
§ Depths
Six ways into the same idea — from bedtime story to chalkboard. No order required.
L1 · Crayon
Told like a bedtime story.
For a curious 10-year-old. No jargon. Just a picture in your head.
Stars don't usually wander around alone. They like to live in massive groups, hundreds of billions of them at a time, slowly turning together in a kind of incredibly slow cosmic dance party. One of those groups is called a galaxy. We live inside one — it's the Milky Way. Our Sun is just one regular dot in it, plodding around the middle once every couple hundred million years (the lap is long, the parking is dreadful). Beyond our galaxy there are trillions more galaxies, each with their own crowd. The universe is, mostly, crowds.
§ Strange but true
- 01There are roughly two trillion galaxies in the observable universe. Each one a city of stars.
- 02Most of every galaxy is invisible. The stars are a glittering veneer floating in a much larger ghost.
- 03The Milky Way and Andromeda are aimed at each other at 110 km/s. In 4.5 billion years, they'll merge into one giant.
§ From the field journal
Galaxy
"A herd of a hundred billion stars, held together by gravity and dark matter."
— observed, sketched, not yet fully understood.
§ Nearby
Constellations near Galaxy
→
Star
The Sun is detonating 600 million tons of hydrogen every second.
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Dark Matter
Most of the universe is invisible. We only see its footprints.
→
Andromeda
Our nearest big neighbor. Will collide with us in 4.5 billion years.
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Cosmic Web
Galaxies don't drift randomly. They live on filaments around vast empty voids.
→
Black Hole
A place in the sky where the door only opens one way.
→
Quasar
A baby black hole eating so fast it outshines its entire galaxy.