The benefit of studying white dwarfs, though, is that they give off less light than other types of stars.

FORBES: White Dwarfs May Hold The Key To Finding Alien Life

The principle behind these experiments is that particles hitting the xenon cause the nucleus of the atom to give off a little bit of light.

CNN: How particle smasher and telescopes relate

Even something too small to emit visible light will probably give off radio waves and infra-red radiation (Jupiter does).

ECONOMIST: X marks the spot

Then he discovered a new Japanese method of cutting diamonds: When viewed under a low-magnification (3x) lens, the stone refracted light in such a way as to give off a pattern of eight heart-shaped sparkles at the bottom of the diamond and eight arrow-shaped fire-bursts through the top--hence the name "hearts-and-arrows" diamonds.

FORBES: Stones on fire