What are decadal stars?

Decadal stars are stars that change every 10 years, just like how you might grow a little taller each year.

Imagine your favorite toy car, it’s always there, but sometimes it gets a new color or a shiny wheel. That’s kind of what decadal stars do, except they’re way far away in space. Instead of changing colors, they change brightness, getting brighter or dimmer, every 10 years.

Think about your bedroom light. Sometimes you turn it on full brightness, and sometimes just a little. Decadal stars are like that light, but instead of you turning it on and off, something inside the star causes its brightness to go up and down in a pattern that repeats every 10 years.

One famous decadal star is called Mira. It’s so far away, we can’t see it with our eyes alone, but astronomers watch it closely because it gets much brighter every 10 years, like a slow, space-based blinking light that helps us learn more about stars!