If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Cepheid variables

3 videos
Stellar parallax can be used for "nearby" stars, but what if we want to measure further out? Well this tutorial will expose you to a class of stars that helps us do this. Cepheids are large, bright, variable stars that are visible in other galaxies. We know how bright they should be and can gauge how far they are by how bright they look to us.

Cepheid variables 1

VIDEO 9:23 minutes
Cepheid Variables 1

Why cepheids pulsate

VIDEO 7:10 minutes
Why Cepheids Pulsate

Why gravity gets so strong near dense objects

VIDEO 8:13 minutes
Why Gravity Gets So Strong Near Dense Objects