The discovery of a new sub-atomic particle: the pentaquark
Although the relevant data was accumulated more than three years ago, those clever people at CERN on the French/Swiss border chose to announce the discovery of a new sub-atomic particle on the same day as the New Horizons photographs of Pluto were published by NASA, so you won’t have heard about it.
The particle is called the pentaquark. As the name suggests, this is a particle made up of five quarks ; actually four quarks and one anti-quark.
Now, until recently, all the known hadrons consist of either three quarks, or one quark and one antiquark. Particles made of two quarks and two antiquarks (known as tetraquarks) have been seen, but the pentaquark is something new.
Excited? Thoroughly confused? Want to know more? See here.