When I hear the word extinction, I think of the dinosaurs and endangered animals. Astronomers have meaning for this term too, and it doesn't involve dinosaurs in space or anything like that!
When astronomers point their telescopes towards the stars, they have to look through not only Earth's atmosphere, but also any gas and dust between us and the star in outer space. Since stars form out of big clouds of mostly Hydrogen gas, astronomers often find themselves looking through thick "space clouds" to try and see stars. These clouds can make the stars appear dim, and sometimes block the light completely! This dimming/blocking of starlight is called "extinction" or "reddening". Stars emit all colors of the rainbow, and even many types of light that we can't see with our eyes. These space clouds tend to preferentially block blue light, making stars appear more red than they actually are. This is why extinction is sometimes called reddening. Above is a picture of the Pillars of Creation taken in visible light with the Hubble Space Telescope. This image shows giant clouds of Hydrogen gas, behind which many stars are forming. We can't see the stars though, because the gas cloud is extincting them and blocking them from our view. Tune in next time to learn how astronomers beat this difficult problem and see these hidden stars!
Image Credit: NASA/HST
