Final answer:
Dark matter may consist of weakly interacting massive particles (WIMPs), which are massive, chargeless particles that interact minimally with normal matter, and are difficult to detect.
Step-by-step explanation:
Astronomers suggest that dark matter is composed of weakly interacting massive particles, or WIMPs. These particles are theorized to be massive and interact only through the weak nuclear force and gravity, making them difficult to detect. WIMPs are considered to be non-baryonic matter, and they could be in forms like neutralinos or axions. Neutralinos might have masses many times that of nucleons, whereas axions could be much lighter. These particles are thought to not participate in nuclear reactions that produce deuterium, thus the abundance of deuterium does not limit the number of WIMPs that could exist. The search for WIMPs involves advanced experiments, such as those conducted at the Large Hadron Collider (LHC) at CERN, to directly observe these elusive candidates for dark matter.