BUBBLE NEBULA
Hubble’s snap of a giant cosmic soap bubble was selected to mark the telescope’s 26th year in space. This seven-light-year-wide bubble, also known as NGC 7635, can be found some 11,090 light years away in the constellation of Cassiopeia. Within the bubble sits the massive superhot star SAO 20575, which is 45 times more massive than the Sun. Gas from the star – its stellar wind – escapes at speeds of over 6.4 million kilometres (4 million miles) per hour, providing the pressure to force the interstellar material outwards to form the bubble shape. The star is 4 million years old and will explode in a spectacular supernova in roughly 10 to 20 million years.