The Universe

Dark Matter and Dark Energy

What’s the difference between dark matter and non-luminous matter?

Early in the study of dark matter, astronomers weren’t sure if the dark matter found in observations consisted of baryonic matter (which, like atoms and molecules, are composed primarily of protons, neutrons, and other known subatomic particles) or non-baryonic matter (composed primarily of particles yet undiscovered). To make a distinction, astronomers sometimes refer to ordinary but unseen matter as “non-luminous” matter. Although a great deal of non-luminous baryonic matter has been discovered over the years, we now know that almost all dark matter in the cosmos is most likely of the non-baryonic variety.


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