Question

an Astronomy question, please answer it comprehensively. Thank you

Astronomers cannot map all of the material in our galaxy using visible light.

a) Why is it that they cannot use visible light?

b) Which regions of the EM spectrum are used to map the galaxy?

Answer 1

• The main reason we don't see the bright center of our galaxy, which is composed of millions of stars, is dust. Visible light is absorbed and scattered by interstellar dust, but that doesn't mean we can't see it on other waves of the spectrum, for example, infrared light doesn't suffer as much because of the dust
• Radio waves and microwaves – the longest wavelengths and lowest energies of light – are used to peer inside dense interstellar clouds and track the motion of cold, dark gas. Radio telescopes have been used to map the structure of our galaxy while microwave telescopes are sensitive to the remnant glow of the Big Bang