Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
Astronomy 2e

Thinking Ahead

Astronomy 2eThinking Ahead

Artist's depiction of the James Webb Space Telescope
Figure 6.1 James Webb Space Telescope (JWST). The James Webb Space Telescope, launched December 25, 2021, is the largest space telescope humanity has deployed so far. Its 18 gold-coated beryllium segments make up a mirror for reflecting infrared light that is 6.5 meters in diameter. Below it on our illustration you see the tennis-court-sized sunscreen that protects it from the heat of our star. The first Webb science images were released in July 2022. (credit: modification of work “Artist’s Impression of the NASA/ESA/CSA James Webb Space Telescope” by ESA/ATG medialab)

If you look at the sky when you are far away from city lights, there seem to be an overwhelming number of stars up there. In reality, only about 9000 stars are visible to the unaided eye (from both hemispheres of our planet). The light from most stars is so weak that by the time it reaches Earth, it cannot be detected by the human eye. How can we learn about the vast majority of objects in the universe that our unaided eyes simply cannot see?

In this chapter, we describe the tools astronomers use to extend their vision into space. We have learned almost everything we know about the universe from studying electromagnetic radiation, as discussed in the chapter on Radiation and Spectra. In the twentieth century, our exploration of space made it possible to detect electromagnetic radiation at all wavelengths, from gamma rays to radio waves. The different wavelengths carry different kinds of information, and the appearance of any given object often depends on the wavelength at which the observations are made.

Order a print copy

As an Amazon Associate we earn from qualifying purchases.


This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at
Citation information

© Jan 23, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.