right throught the mug!  This is an infrared image, which shows  wavelengths of energy that humans can't see.  The wavelength of radiated heat is slightly longer than the wavelength we see as red. (hence the name infra-red) Normal cameras produce images using the wavelengths visible to humans, but technology has allowed us to "see" the heat given off by objects. Radiated heat is different from conducted or convected heat.  Radiated heat is a type of electromagnetic enegy, and can travel through space.  This is how energy reached the earth from the sun.  Heat from a radiant source travels in all directions.  For example, much of the heat from a candle rises due to convection, but you can see the evidence of radiated heat from the melted wax on the candle's top.

What sorts of things give off infrared radiation?  You'd be surprised.... of course you can feel radiant heat coming from your own skin or from a fire, but even things you think of as being cold radiate heat they are still made of particles which are moving.  Particle motion translates to radiating heat.

Anything with energy radiates heat.  Even an ice cube radiates heat.  You can imagine air that is -9°C pretty easily... what if you took a 0°C ice cube and put it into that air?  The ice cube would give heat to the colder air!    Even objects in the coldness of outer space radiate heat.
 
 

Image stolen from K.-P. Möllmann and M. Vollmer, University of Applied Sciences Brandenburg/Germany