(Every day until Christmas, I’ll be posting a science-related image.)

Day 7

Human vision is a glorious thing, but in many respects it’s limited. We can only see a very narrow range of the electromagnetic spectrum: the colors of light run from gamma rays to radio waves, with visible light falling somewhere in the middle. We use technology to compensate for our eyes, allowing us to “see” colors otherwise invisible to us. (No value judgement here! We humans evolved to see the light corresponding to the dominant wavelengths our Sun produces.) In astronomy, we use telescopes of a variety of shapes and sizes to turn light from distant objects into images and spectra—the constituent colors, whether we can see them or not.

Radio light has the lowest energy and largest wavelengths: the waves can measured in centimeters or meters! The telescopes that see radio light are correspondingly larger than their visible light counterparts. The photo above shows one of the 27 telescopes of the Very Large Array (VLA), each of which is 25 meters across. Each of the individual telescopes can see reasonably well, but when they all work together, they create some of the highest-resolution images of the Universe in radio light. I’ll highlight an image from the VLA in tomorrow’s Science Advent entry.