Scientists use a variety of different instruments to look at the stars. Ever since the 1600s, the most important instrument is still a telescope. But, telescopes today are much more powerful than back then. They can see farther and clearer than before. Originally, telescopes only saw visible light. Now, we have telescopes that can also see x-rays, microwaves, infrared, and other kinds of radiation. This gives us a lot of information about the properties of stars that we look at, much more than just their color and shape. This helps us tell what elements the star is made of, how hot it is, how old it is, etc. Scientists look at other things, too, including planets and comets and asteroids. If we get back physical samples of any of these, we use the same tools chemists use to determine what they are made of.

Probably the most important thing that has changed since the old days is the precision of the instruments used. An example of this is how scientists find new planets. We don't literally "look" for planets. They're far too small to see. Instead, we generally look for very very very small wobbles in a star's rotation. These tiny wobbles are the result of planets and gravity making the star spin slightly off its center. Being able to see this has been compared to listening for a pin drop at a concert. It's only by the remarkably precise instruments that we are able to find these wobbles. The "secret" instrument used the most is math. Math lets you calculate planet size and distance from the wobbles. It also lets you simulate galaxy and star formation and lives. Math is responsible for pretty much everything we know in astronomy and is really important. However, you probably wouldn't think of that as an instrument.