Cosmic Perspectives from Amid the Stars:
Astronomy Blog

Have you ever wondered where to point your telescope? If you’ve ever looked into a listing of astronomical objects, you’ve likely noticed that many of the galaxies, nebulae, and more are labeled with an M followed by a number. That means the object in question is part of the Messier Catalog, a listing of 110 astronomical objects used worldwide that features some of the best targets for any telescope.

Ever since Galileo pointed his telescope to the sky in 1609, telescopes have slowly revealed the universe to us. Over time, the telescopes got better, and so did the views they provided. But we started to hit a point of diminishing returns. As powerful as telescopes were getting, factors that seemed inescapable on Earth got more and more in the way. There was one clear solution: make a telescope that’s not on Earth.

Ask any number of people what the single most important tool in astronomy is, and almost universally, they will claim the telescope as their answer. With telescopes, we’ve been able to peer beyond our world and out into the distant reaches of the universe. The name literally means far-seeing. How is it that these rather simple contraptions are able to show us so much? How do telescopes work?