Actually, the group of bananas commonly referred to as a bunch at the store is actually a hand, or less commonly tier.
PSR B1509-58 - X-rays from Chandra are gold; Infrared from WISE in red, green and blue/max. A pulsar (from pulse and -ar as in quasar) is a highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much like the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission.
PU is generally an abbreviation for polyurethane, a flexible and resilient material that is foamy or rubbery. The substance is categorised as a polymer and can be manipulated to take on a foam, liquid, or solid form. It is elastic like rubber, but strong, like metal and therefore it can be used to make tires.