Astronomers discovered stars even cooler than the traditional spectral type M stars recently. Astronomers have these cool stars a new spectral type, L. If you wanted to go out and find more such type L stars, what kind of instrument would it be smart to use?

A sensitive infra-red telescope

Explanation:

Infrared light is highly advantageous for astronomers as it helps in discovering and studying the astronomical objects that are observed in the night sky.

This infrared light is commonly used in the telescopes to study the distant stars, and by analyzing them, they are classified as different types like L or M types. These telescopes, by using the infrared light, it is able to detect the presence of stars and other astronomical bodies, and this type of telescopes helps in determining the temperature of the distant objects such as the stars, planets, and other objects.