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 star has to be a minimum of about 8 times the mass of our Sun to go supernova. Actually, we are probably talking about what is technically called a Type II (type two) suâ¦pernova. This is the second most common sort of supernova. What happens inside the star is a little complex.