 In our segment on nearby stars, we reached as far as parallax can take us by using the space-based satellites, Parkus and Gaia. But if that's all we had, we'd know very little about our galaxy, and almost nothing about the universe beyond. But in this segment on distant stars, we introduced two new rungs for our cosmic distance ladder. One is the Hertz-Brunn-Russell diagram for estimating a star's luminosity and therefore its distance. The other is variable stars that work as standard candles, stars that tell us their intrinsic luminosity by the period of their variable luminosity cycles. In particular, we covered Cepheid and RR Lyra variables. These rungs in our distance ladder have taken us across the entire Milky Way. In subsequent sections, we'll use these distance ladder techniques on star clusters, our birth nebula, star death nebula, also known as planetary nebula. Our next segment.