The fourth example was a G-Wizz electric vehicle which is the most environmentally friendly or carbon neutral green vehicle type.

BBC: NEWS | Programmes | Breakfast | Low carbon family: "Green" cars

Neutrino astronomy is hard because neutrinos (a type of electrically neutral elementary particle) are rarely absorbed by matter.

ECONOMIST: This year, the Nobel authorities have shown a deft touch

Both these supernova remnants are strong sources of the type of gamma rays one would expect from neutral pion decay.

BBC: Cosmic rays: Fermi telescope settles mystery of origin