The eRosita space telescope has just unveiled its first survey of X-ray sources from the whole sky.
Our eye only perceives a tiny part of the whole extent of the light spectrum. We are only sensitive to photons included in a certain range of energies, from red to purple (through yellow, green or blue). There is, however, a plethora of invisible photons, including those that are less energetic, starting with infrared, before descending into the microwave, then radio (which breaks down into millimeter, then centimeter, decimetric, metric waves, etc.). All these photons are emitted by “cold” matter.
Conversely, there is a whole range of more energetic photons beyond violet: ultraviolet, then X-rays and finally gamma rays. These more energetic grains are emitted, you will understand, by “hot” events. The Sun emits a little, but most of its activity is centered in the visible (it is no coincidence: our eye is adapted to the light of our star).
For astronomers, look
