Reflection in a Dark Universe

Like lighthouse beacons in a dark ocean, stars act as tiny islands in the vast universe.  Producing light at the atomic level from the powerful release of energy through fusion, they are the engines that drive the formation of new elements.  But in the darkness there are plenty of other hidden objects that are cold and give off little to no light.  Yet many of them are easily seen.  Here’s Why! The first thing to think about is infrared light, the radiation given off by warm objects.  Large planets and brown dwarf stars are very bright in infrared, much brighter...

Why is Mercury so Dark?

Mercury, the smallest planet in the solar system, and closest to the Sun, is only a little bit bigger than Earth’s Moon.  But the Moon is comparatively reflective object.  Mercury is thought to be made of the same rock as the Moon, so what is the difference? Why do objects in our Solar system have different brightnesses? The key is in a property called albedo.  It’s basically how much light an object reflects, measured as a fraction.  For example, the Moon reflects 12% of the light the Sun shines on it, so it has an albedo of 0.12.  The albedo...