The astronomers overcame this by using cameras that pick up infra-red rather than visible light (like the thermal imaging cameras used for seeing in the dark).

ECONOMIST: Dusty genesis

For example, iron-gall ink, commonly used on ancient documents, is transparent to infra-red light and most visible in the ultraviolet region of the spectrum.

ECONOMIST: Monitor

This part of the infra-red spectrum, with wavelengths close to that of visible light, carries heat energy.

ECONOMIST: Archaeology: What lies beneath | The

Though the carbon nanotubes absorb infra-red light, they are almost totally transparent to the visible variety.

ECONOMIST: Monitor

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

Subsequent observations with an infra-red telescope, which can see things that are too cool to shine with visible light, showed that it was a very faint star so faint that it is off the bottom of astronomers' scale of stellar classification.

ECONOMIST: Twinkle, twinkle, giant planet