1.   Instead they use computers to analyze the light the object emits.

2.   Low sounds are usually emitted by objects large enough to generate the long wavelengths of those notes.

3.   Objects emit radiation of increasing frequency as they get hotter, which is why a filament goes from red-hot to blue-hot when it heats up.

4.   Yet in many cases the objects do not emit visible light, suggesting that they existed at a time before the multitude of stars.

5.   At that temperature, these objects do not emit enough light or other radiation to be easily detected by telescopes.

6.   As a result, the object is continually emitting energy comparable to that of a million suns, while its size is no larger than a long avenue.