<Dd> 4 H → He + 2e + 2γ + 2ν (26.7 MeV) </Dd> <P> where e is a positron, γ is a gamma ray photon, ν is a neutrino, and H and He are isotopes of hydrogen and helium, respectively . The energy released by this reaction is in millions of electron volts, which is actually only a tiny amount of energy . However enormous numbers of these reactions occur constantly, producing all the energy necessary to sustain the star's radiation output . In comparison, the combustion of two hydrogen gas molecules with one oxygen gas molecule releases only 5.7 eV . </P> <Table> Minimum stellar mass required for fusion <Tr> <Th> Element </Th> <Th> Solar masses </Th> </Tr> <Tr> <Td> Hydrogen </Td> <Td> 0.01 </Td> </Tr> <Tr> <Td> Helium </Td> <Td> 0.4 </Td> </Tr> <Tr> <Td> Carbon </Td> <Td> 5 </Td> </Tr> <Tr> <Td> Neon </Td> <Td> 8 </Td> </Tr> </Table> <Tr> <Th> Element </Th> <Th> Solar masses </Th> </Tr>

In the present time on earth can we see star a as a main sequence star