My own current neighborhood fits this definition of a suburb that lacks the negative aspects of postwar sprawl. A 20-minute train ride from the center of Philadelphia, it boasts a retail and small office district within a short walk of most homes.
Crab supernova remnant: A supernova is an explosion of a massive supergiant star. It may shine with the brightness of 10 billion suns! The total energy output may be 10 44 joules, as much as the total output of the sun during its 10 billion year lifetime. The likely scenario is that fusion proceeds to build up a core of iron.
A) One or two supernova are observed to go off in the Milky Way galaxy each year. B) When a planetary nebula is produced it can outshine an entire galaxy. C) Type II supernovae are produced by the death of a massive star. D) Type Ia supernovae are produced when a neutron star collapses to become a black hole. E) Type Ia supernovae show a lot of strong hydrogen lines in their spectra.