How is heat transferred?
There are three main modes of heat transfer:
- conduction
- convection
- radiation
In space, which is essentially a vacuum, heat can only be transferred through radiation.
Any body with a temperature above absolute zero (0 K = −273.15 °C) emits electromagnetic radiation as a result of the thermal agitation of its particles. The characteristics of this radiation, particularly its wavelength, depend on the temperature of the emitting body.
The radiation emitted by a body is described by the electromagnetic spectrum. This spectrum classifies electromagnetic waves according to their wavelength (Figure 1). The main domains, from shortest to longest wavelength, are:
- X-rays
- ultraviolet (UV) radiation
- visible light
- infrared (IR) radiation
Other domains also exist, such as gamma rays (shorter wavelengths) and radio waves (longer wavelengths).
Figure 1: Ozone concentration as a function of altitude. The vast majority of ozone molecules are concentrated in the stratosphere. This “layer” protects the Earth from harmful UV-B radiation.