Final answer:
The particle described as virtually massless, chargeless, traveling close to the speed of light, and rarely interacting with matter is a neutrino. It is a byproduct of solar fusion processes and can pass through large amounts of material without being affected.
Step-by-step explanation:
The virtually massless and chargeless particle that is one of the products of fusion reactions in the Sun, moves at close to the speed of light and interacts with matter hardly at all is known as a neutrino. Neutrinos are fundamental particles that are associated with the weak nuclear force, have almost no mass, and travel near the speed of light. They interact so weakly with other matter that they could pass through extensive amounts of solid material without any interaction, making them extremely elusive to detect.
Solar neutrinos are produced in the proton-proton chain reaction when two hydrogen atoms fuse to form deuterium, emitting a neutrino in the process. These neutrinos escape the Sun approximately two seconds after being created, as they can traverse the Sun's dense interior without being absorbed or scattered, unlike photons that may take much longer due to repeated interactions with matter.