The space within our Solar System is incredibly cold, despite being close to a fiery sphere with temperatures reaching millions of degrees Celsius.
This seemingly simple question opens the door to an intriguing exploration of heat transfer mechanisms in the universe.
In the extremely cold vacuum of space, the average temperature is around -270.45°C. In contrast, the Sun is an astonishing source of heat.
Its core exceeds temperatures of 15 million degrees Celsius, while the surface, known as the photosphere, reaches about 5,500°C, and the solar corona (located far beyond the photosphere) has a temperature of 3.5 million degrees Celsius.
The Sun has temperatures reaching tens of millions of degrees Celsius. (Illustration: Futura Science).
But why is the space within our Solar System not heated to extreme temperatures by the Sun’s intense heat?
The confusion often arises from the intuitive idea that the Sun acts like a giant fire, directly heating nearby objects. However, this process varies in space.
Interaction with the Atmosphere
The warmth we feel on Earth is due to radiation emitted by the Sun, which encompasses various wavelengths across the electromagnetic spectrum, including visible light. This radiation interacts with particles present on Earth.
In other words, the heat we perceive on the surface of our Blue Planet primarily comes from the interaction of photons emitted by the Sun with particles in Earth’s atmosphere.
Specifically, this interaction leads to the absorption of energy. It excites particles to vibrate, resulting in increased molecular agitation, which in turn raises the temperature.
This process causes the warming of the atmosphere. Similarly, when this energy reaches the Earth’s surface, it is absorbed, leading to the excitation of surface particles and warming our planet.
However, in nearly perfect vacuum space, there are very few particles for solar radiation to interact with. As a result, there is not enough matter to be directly heated by radiation, creating a sense of coldness.
Nonetheless, this does not mean that space lacks temperature. An object, such as a space probe, on the path of solar radiation can indeed be heated, as the heat shield of NASA’s Parker Solar Probe will face temperatures soaring up to 1,400°C as it nears the Sun.
